Resolve merge conflicts

packages/opencode/test/agent/agent.test.ts

@@ -111,6 +111,20 @@ test("explore agent denies edit and write", async () => {
   })
 })
 
+test("explore agent asks for external directories and allows Truncate.GLOB", async () => {
+  const { Truncate } = await import("../../src/tool/truncation")
+  await using tmp = await tmpdir()
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const explore = await Agent.get("explore")
+      expect(explore).toBeDefined()
+      expect(PermissionNext.evaluate("external_directory", "/some/other/path", explore!.permission).action).toBe("ask")
+      expect(PermissionNext.evaluate("external_directory", Truncate.GLOB, explore!.permission).action).toBe("allow")
+    },
+  })
+})
+
 test("general agent denies todo tools", async () => {
   await using tmp = await tmpdir()
   await Instance.provide({

packages/opencode/test/cli/github-action.test.ts

@@ -1,5 +1,5 @@
 import { test, expect, describe } from "bun:test"
-import { extractResponseText } from "../../src/cli/cmd/github"
+import { extractResponseText, formatPromptTooLargeError } from "../../src/cli/cmd/github"
 import type { MessageV2 } from "../../src/session/message-v2"
 
 // Helper to create minimal valid parts
@@ -159,3 +159,39 @@ describe("extractResponseText", () => {
     expect(extractResponseText(parts)).toBe("Here's what I found")
   })
 })
+
+describe("formatPromptTooLargeError", () => {
+  test("formats error without files", () => {
+    const result = formatPromptTooLargeError([])
+    expect(result).toBe("PROMPT_TOO_LARGE: The prompt exceeds the model's context limit.")
+  })
+
+  test("formats error with files (base64 content)", () => {
+    // Base64 is ~33% larger than original, so we multiply by 0.75 to get original size
+    // 400 KB base64 = 300 KB original, 200 KB base64 = 150 KB original
+    const files = [
+      { filename: "screenshot.png", content: "a".repeat(400 * 1024) },
+      { filename: "diagram.png", content: "b".repeat(200 * 1024) },
+    ]
+    const result = formatPromptTooLargeError(files)
+
+    expect(result).toStartWith("PROMPT_TOO_LARGE: The prompt exceeds the model's context limit.")
+    expect(result).toInclude("Files in prompt:")
+    expect(result).toInclude("screenshot.png (300 KB)")
+    expect(result).toInclude("diagram.png (150 KB)")
+  })
+
+  test("lists all files when multiple present", () => {
+    // Base64 sizes: 4KB -> 3KB, 8KB -> 6KB, 12KB -> 9KB
+    const files = [
+      { filename: "img1.png", content: "x".repeat(4 * 1024) },
+      { filename: "img2.jpg", content: "y".repeat(8 * 1024) },
+      { filename: "img3.gif", content: "z".repeat(12 * 1024) },
+    ]
+    const result = formatPromptTooLargeError(files)
+
+    expect(result).toInclude("img1.png (3 KB)")
+    expect(result).toInclude("img2.jpg (6 KB)")
+    expect(result).toInclude("img3.gif (9 KB)")
+  })
+})

packages/opencode/test/cli/plugin-auth-picker.test.ts

@@ -0,0 +1,120 @@
+import { test, expect, describe } from "bun:test"
+import { resolvePluginProviders } from "../../src/cli/cmd/auth"
+import type { Hooks } from "@kilocode/plugin"
+
+function hookWithAuth(provider: string): Hooks {
+  return {
+    auth: {
+      provider,
+      methods: [],
+    },
+  }
+}
+
+function hookWithoutAuth(): Hooks {
+  return {}
+}
+
+describe("resolvePluginProviders", () => {
+  test("returns plugin providers not in models.dev", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(),
+      providerNames: {},
+    })
+    expect(result).toEqual([{ id: "portkey", name: "portkey" }])
+  })
+
+  test("skips providers already in models.dev", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("anthropic")],
+      existingProviders: { anthropic: {} },
+      disabled: new Set(),
+      providerNames: {},
+    })
+    expect(result).toEqual([])
+  })
+
+  test("deduplicates across plugins", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey"), hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(),
+      providerNames: {},
+    })
+    expect(result).toEqual([{ id: "portkey", name: "portkey" }])
+  })
+
+  test("respects disabled_providers", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(["portkey"]),
+      providerNames: {},
+    })
+    expect(result).toEqual([])
+  })
+
+  test("respects enabled_providers when provider is absent", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(),
+      enabled: new Set(["anthropic"]),
+      providerNames: {},
+    })
+    expect(result).toEqual([])
+  })
+
+  test("includes provider when in enabled set", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(),
+      enabled: new Set(["portkey"]),
+      providerNames: {},
+    })
+    expect(result).toEqual([{ id: "portkey", name: "portkey" }])
+  })
+
+  test("resolves name from providerNames", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(),
+      providerNames: { portkey: "Portkey AI" },
+    })
+    expect(result).toEqual([{ id: "portkey", name: "Portkey AI" }])
+  })
+
+  test("falls back to id when no name configured", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithAuth("portkey")],
+      existingProviders: {},
+      disabled: new Set(),
+      providerNames: {},
+    })
+    expect(result).toEqual([{ id: "portkey", name: "portkey" }])
+  })
+
+  test("skips hooks without auth", () => {
+    const result = resolvePluginProviders({
+      hooks: [hookWithoutAuth(), hookWithAuth("portkey"), hookWithoutAuth()],
+      existingProviders: {},
+      disabled: new Set(),
+      providerNames: {},
+    })
+    expect(result).toEqual([{ id: "portkey", name: "portkey" }])
+  })
+
+  test("returns empty for no hooks", () => {
+    const result = resolvePluginProviders({
+      hooks: [],
+      existingProviders: {},
+      disabled: new Set(),
+      providerNames: {},
+    })
+    expect(result).toEqual([])
+  })
+})

packages/opencode/test/config/config.test.ts

@@ -7,6 +7,7 @@ import path from "path"
 import fs from "fs/promises"
 import { pathToFileURL } from "url"
 import { Global } from "../../src/global"
+import { Filesystem } from "../../src/util/filesystem"
 
 // Get managed config directory from environment (set in preload.ts)
 const managedConfigDir = process.env.KILO_TEST_MANAGED_CONFIG_DIR!
@@ -17,11 +18,11 @@ afterEach(async () => {
 
 async function writeManagedSettings(settings: object, filename = "opencode.json") {
   await fs.mkdir(managedConfigDir, { recursive: true })
-  await Bun.write(path.join(managedConfigDir, filename), JSON.stringify(settings))
+  await Filesystem.write(path.join(managedConfigDir, filename), JSON.stringify(settings))
 }
 
 async function writeConfig(dir: string, config: object, name = "opencode.json") {
-  await Bun.write(path.join(dir, name), JSON.stringify(config))
+  await Filesystem.write(path.join(dir, name), JSON.stringify(config))
 }
 
 test("loads config with defaults when no files exist", async () => {
@@ -58,7 +59,7 @@ test("loads JSON config file", async () => {
 test("loads JSONC config file", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.jsonc"),
         `{
         // This is a comment
@@ -144,7 +145,7 @@ test("preserves env variables when adding $schema to config", async () => {
     await using tmp = await tmpdir({
       init: async (dir) => {
         // Config without $schema - should trigger auto-add
-        await Bun.write(
+        await Filesystem.write(
           path.join(dir, "opencode.json"),
           JSON.stringify({
             theme: "{env:PRESERVE_VAR}",
@@ -159,7 +160,7 @@ test("preserves env variables when adding $schema to config", async () => {
         expect(config.theme).toBe("secret_value")
 
         // Read the file to verify the env variable was preserved
-        const content = await Bun.file(path.join(tmp.path, "opencode.json")).text()
+        const content = await Filesystem.readText(path.join(tmp.path, "opencode.json"))
         expect(content).toContain("{env:PRESERVE_VAR}")
         expect(content).not.toContain("secret_value")
         expect(content).toContain("$schema")
@@ -177,7 +178,7 @@ test("preserves env variables when adding $schema to config", async () => {
 test("handles file inclusion substitution", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(path.join(dir, "included.txt"), "test_theme")
+      await Filesystem.write(path.join(dir, "included.txt"), "test_theme")
       await writeConfig(dir, {
         $schema: "https://app.kilo.ai/config.json",
         theme: "{file:included.txt}",
@@ -196,7 +197,7 @@ test("handles file inclusion substitution", async () => {
 test("handles file inclusion with replacement tokens", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(path.join(dir, "included.md"), "const out = await Bun.$`echo hi`")
+      await Filesystem.write(path.join(dir, "included.md"), "const out = await Bun.$`echo hi`")
       await writeConfig(dir, {
         $schema: "https://app.kilo.ai/config.json",
         theme: "{file:included.md}",
@@ -233,7 +234,7 @@ test("validates config schema and throws on invalid fields", async () => {
 test("throws error for invalid JSON", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(path.join(dir, "opencode.json"), "{ invalid json }")
+      await Filesystem.write(path.join(dir, "opencode.json"), "{ invalid json }")
     },
   })
   await Instance.provide({
@@ -336,7 +337,7 @@ test("handles command configuration", async () => {
 test("migrates autoshare to share field", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -358,7 +359,7 @@ test("migrates autoshare to share field", async () => {
 test("migrates mode field to agent field", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -395,7 +396,7 @@ test("loads config from .opencode directory", async () => {
       const agentDir = path.join(opencodeDir, "agent")
       await fs.mkdir(agentDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentDir, "test.md"),
         `---
 model: test/model
@@ -428,7 +429,7 @@ test("loads agents from .opencode/agents (plural)", async () => {
       const agentsDir = path.join(opencodeDir, "agents")
       await fs.mkdir(path.join(agentsDir, "nested"), { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentsDir, "helper.md"),
         `---
 model: test/model
@@ -437,7 +438,7 @@ mode: subagent
 Helper agent prompt`,
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentsDir, "nested", "child.md"),
         `---
 model: test/model
@@ -479,7 +480,7 @@ test("loads commands from .opencode/command (singular)", async () => {
       const commandDir = path.join(opencodeDir, "command")
       await fs.mkdir(path.join(commandDir, "nested"), { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandDir, "hello.md"),
         `---
 description: Test command
@@ -487,7 +488,7 @@ description: Test command
 Hello from singular command`,
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandDir, "nested", "child.md"),
         `---
 description: Nested command
@@ -524,7 +525,7 @@ test("loads commands from .opencode/commands (plural)", async () => {
       const commandsDir = path.join(opencodeDir, "commands")
       await fs.mkdir(path.join(commandsDir, "nested"), { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandsDir, "hello.md"),
         `---
 description: Test command
@@ -532,7 +533,7 @@ description: Test command
 Hello from plural commands`,
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandsDir, "nested", "child.md"),
         `---
 description: Nested command
@@ -568,7 +569,7 @@ test("updates config and writes to file", async () => {
       const newConfig = { model: "updated/model" }
       await Config.update(newConfig as any)
 
-      const writtenConfig = JSON.parse(await Bun.file(path.join(tmp.path, "config.json")).text())
+      const writtenConfig = await Filesystem.readJson(path.join(tmp.path, "config.json"))
       expect(writtenConfig.model).toBe("updated/model")
     },
   })
@@ -639,8 +640,8 @@ test("installs dependencies in writable KILO_CONFIG_DIR", async () => {
       },
     })
 
-    expect(await Bun.file(path.join(tmp.extra, "package.json")).exists()).toBe(true)
-    expect(await Bun.file(path.join(tmp.extra, ".gitignore")).exists()).toBe(true)
+    expect(await Filesystem.exists(path.join(tmp.extra, "package.json"))).toBe(true)
+    expect(await Filesystem.exists(path.join(tmp.extra, ".gitignore"))).toBe(true)
   } finally {
     if (prev === undefined) delete process.env.KILO_CONFIG_DIR
     else process.env.KILO_CONFIG_DIR = prev
@@ -653,12 +654,12 @@ test("resolves scoped npm plugins in config", async () => {
       const pluginDir = path.join(dir, "node_modules", "@scope", "plugin")
       await fs.mkdir(pluginDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "package.json"),
         JSON.stringify({ name: "config-fixture", version: "1.0.0", type: "module" }, null, 2),
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(pluginDir, "package.json"),
         JSON.stringify(
           {
@@ -672,9 +673,9 @@ test("resolves scoped npm plugins in config", async () => {
         ),
       )
 
-      await Bun.write(path.join(pluginDir, "index.js"), "export default {}\n")
+      await Filesystem.write(path.join(pluginDir, "index.js"), "export default {}\n")
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({ $schema: "https://app.kilo.ai/config.json", plugin: ["@scope/plugin"] }, null, 2),
       )
@@ -708,7 +709,7 @@ test("merges plugin arrays from global and local configs", async () => {
       await fs.mkdir(opencodeDir, { recursive: true })
 
       // Global config with plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -717,7 +718,7 @@ test("merges plugin arrays from global and local configs", async () => {
       )
 
       // Local .opencode config with different plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -753,7 +754,7 @@ test("does not error when only custom agent is a subagent", async () => {
       const agentDir = path.join(opencodeDir, "agent")
       await fs.mkdir(agentDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentDir, "helper.md"),
         `---
 model: test/model
@@ -784,7 +785,7 @@ test("merges instructions arrays from global and local configs", async () => {
       const opencodeDir = path.join(projectDir, ".opencode")
       await fs.mkdir(opencodeDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -792,7 +793,7 @@ test("merges instructions arrays from global and local configs", async () => {
         }),
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -823,7 +824,7 @@ test("deduplicates duplicate instructions from global and local configs", async
       const opencodeDir = path.join(projectDir, ".opencode")
       await fs.mkdir(opencodeDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -831,7 +832,7 @@ test("deduplicates duplicate instructions from global and local configs", async
         }),
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -867,7 +868,7 @@ test("deduplicates duplicate plugins from global and local configs", async () =>
       await fs.mkdir(opencodeDir, { recursive: true })
 
       // Global config with plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -876,7 +877,7 @@ test("deduplicates duplicate plugins from global and local configs", async () =>
       )
 
       // Local .opencode config with some overlapping plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -915,7 +916,7 @@ test("deduplicates duplicate plugins from global and local configs", async () =>
 test("migrates legacy tools config to permissions - allow", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -946,7 +947,7 @@ test("migrates legacy tools config to permissions - allow", async () => {
 test("migrates legacy tools config to permissions - deny", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -977,7 +978,7 @@ test("migrates legacy tools config to permissions - deny", async () => {
 test("migrates legacy write tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1086,7 +1087,7 @@ test("missing managed settings file is not an error", async () => {
 test("migrates legacy edit tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1115,7 +1116,7 @@ test("migrates legacy edit tool to edit permission", async () => {
 test("migrates legacy patch tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1144,7 +1145,7 @@ test("migrates legacy patch tool to edit permission", async () => {
 test("migrates legacy multiedit tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1173,7 +1174,7 @@ test("migrates legacy multiedit tool to edit permission", async () => {
 test("migrates mixed legacy tools config", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1208,7 +1209,7 @@ test("migrates mixed legacy tools config", async () => {
 test("merges legacy tools with existing permission config", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1241,7 +1242,7 @@ test("merges legacy tools with existing permission config", async () => {
 test("permission config preserves key order", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1289,7 +1290,7 @@ test("project config can override MCP server enabled status", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
       // Simulates a base config (like from remote .well-known) with disabled MCP
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.jsonc"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1308,7 +1309,7 @@ test("project config can override MCP server enabled status", async () => {
         }),
       )
       // Project config enables just jira
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1347,7 +1348,7 @@ test("MCP config deep merges preserving base config properties", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
       // Base config with full MCP definition
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.jsonc"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1364,7 +1365,7 @@ test("MCP config deep merges preserving base config properties", async () => {
         }),
       )
       // Override just enables it, should preserve other properties
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1399,7 +1400,7 @@ test("local .opencode config can override MCP from project config", async () =>
   await using tmp = await tmpdir({
     init: async (dir) => {
       // Project config with disabled MCP
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1415,7 +1416,7 @@ test("local .opencode config can override MCP from project config", async () =>
       // Local .opencode directory config enables it
       const opencodeDir = path.join(dir, ".opencode")
       await fs.mkdir(opencodeDir, { recursive: true })
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -1483,7 +1484,7 @@ test("project config overrides remote well-known config", async () => {
       git: true,
       init: async (dir) => {
         // Project config enables jira (overriding remote default)
-        await Bun.write(
+        await Filesystem.write(
           path.join(dir, "opencode.json"),
           JSON.stringify({
             $schema: "https://app.kilo.ai/config.json",
@@ -1576,7 +1577,7 @@ describe("deduplicatePlugins", () => {
         const pluginDir = path.join(opencodeDir, "plugin")
         await fs.mkdir(pluginDir, { recursive: true })
 
-        await Bun.write(
+        await Filesystem.write(
           path.join(dir, "opencode.json"),
           JSON.stringify({
             $schema: "https://app.kilo.ai/config.json",
@@ -1584,7 +1585,7 @@ describe("deduplicatePlugins", () => {
           }),
         )
 
-        await Bun.write(path.join(pluginDir, "my-plugin.js"), "export default {}")
+        await Filesystem.write(path.join(pluginDir, "my-plugin.js"), "export default {}")
       },
     })
 
@@ -1611,7 +1612,7 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
       await using tmp = await tmpdir({
         init: async (dir) => {
           // Create a project config that would normally be loaded
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://app.kilo.ai/config.json",
@@ -1649,7 +1650,7 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
           // Create a .opencode directory with a command
           const opencodeDir = path.join(dir, ".opencode", "command")
           await fs.mkdir(opencodeDir, { recursive: true })
-          await Bun.write(path.join(opencodeDir, "test-cmd.md"), "# Test Command\nThis is a test command.")
+          await Filesystem.write(path.join(opencodeDir, "test-cmd.md"), "# Test Command\nThis is a test command.")
         },
       })
       await Instance.provide({
@@ -1706,7 +1707,7 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
       await using tmp = await tmpdir({
         init: async (dir) => {
           // Create a config with relative instruction path
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://app.kilo.ai/config.json",
@@ -1714,7 +1715,7 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
             }),
           )
           // Create the instruction file (should be skipped)
-          await Bun.write(path.join(dir, "CUSTOM.md"), "# Custom Instructions")
+          await Filesystem.write(path.join(dir, "CUSTOM.md"), "# Custom Instructions")
         },
       })
 
@@ -1752,7 +1753,7 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
       await using configDirTmp = await tmpdir({
         init: async (dir) => {
           // Create config in the custom config dir
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://app.kilo.ai/config.json",
@@ -1765,7 +1766,7 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
       await using projectTmp = await tmpdir({
         init: async (dir) => {
           // Create config in project (should be ignored)
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://app.kilo.ai/config.json",
@@ -1800,3 +1801,66 @@ describe("KILO_DISABLE_PROJECT_CONFIG", () => {
     }
   })
 })
+
+describe("OPENCODE_CONFIG_CONTENT token substitution", () => {
+  test("substitutes {env:} tokens in OPENCODE_CONFIG_CONTENT", async () => {
+    const originalEnv = process.env["OPENCODE_CONFIG_CONTENT"]
+    const originalTestVar = process.env["TEST_CONFIG_VAR"]
+    process.env["TEST_CONFIG_VAR"] = "test_api_key_12345"
+    process.env["OPENCODE_CONFIG_CONTENT"] = JSON.stringify({
+      $schema: "https://opencode.ai/config.json",
+      theme: "{env:TEST_CONFIG_VAR}",
+    })
+
+    try {
+      await using tmp = await tmpdir()
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const config = await Config.get()
+          expect(config.theme).toBe("test_api_key_12345")
+        },
+      })
+    } finally {
+      if (originalEnv !== undefined) {
+        process.env["OPENCODE_CONFIG_CONTENT"] = originalEnv
+      } else {
+        delete process.env["OPENCODE_CONFIG_CONTENT"]
+      }
+      if (originalTestVar !== undefined) {
+        process.env["TEST_CONFIG_VAR"] = originalTestVar
+      } else {
+        delete process.env["TEST_CONFIG_VAR"]
+      }
+    }
+  })
+
+  test("substitutes {file:} tokens in OPENCODE_CONFIG_CONTENT", async () => {
+    const originalEnv = process.env["OPENCODE_CONFIG_CONTENT"]
+
+    try {
+      await using tmp = await tmpdir({
+        init: async (dir) => {
+          await Bun.write(path.join(dir, "api_key.txt"), "secret_key_from_file")
+          process.env["OPENCODE_CONFIG_CONTENT"] = JSON.stringify({
+            $schema: "https://opencode.ai/config.json",
+            theme: "{file:./api_key.txt}",
+          })
+        },
+      })
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const config = await Config.get()
+          expect(config.theme).toBe("secret_key_from_file")
+        },
+      })
+    } finally {
+      if (originalEnv !== undefined) {
+        process.env["OPENCODE_CONFIG_CONTENT"] = originalEnv
+      } else {
+        delete process.env["OPENCODE_CONFIG_CONTENT"]
+      }
+    }
+  })
+})

packages/opencode/test/file/index.test.ts

@@ -0,0 +1,394 @@
+import { describe, test, expect } from "bun:test"
+import path from "path"
+import fs from "fs/promises"
+import { File } from "../../src/file"
+import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
+import { tmpdir } from "../fixture/fixture"
+
+describe("file/index Filesystem patterns", () => {
+  describe("File.read() - text content", () => {
+    test("reads text file via Filesystem.readText()", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      await fs.writeFile(filepath, "Hello World", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.txt")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("Hello World")
+        },
+      })
+    })
+
+    test("reads with Filesystem.exists() check", async () => {
+      await using tmp = await tmpdir()
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          // Non-existent file should return empty content
+          const result = await File.read("nonexistent.txt")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("")
+        },
+      })
+    })
+
+    test("trims whitespace from text content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      await fs.writeFile(filepath, "  content with spaces  \n\n", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.txt")
+          expect(result.content).toBe("content with spaces")
+        },
+      })
+    })
+
+    test("handles empty text file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "empty.txt")
+      await fs.writeFile(filepath, "", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("empty.txt")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("")
+        },
+      })
+    })
+
+    test("handles multi-line text files", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "multiline.txt")
+      await fs.writeFile(filepath, "line1\nline2\nline3", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("multiline.txt")
+          expect(result.content).toBe("line1\nline2\nline3")
+        },
+      })
+    })
+  })
+
+  describe("File.read() - binary content", () => {
+    test("reads binary file via Filesystem.readArrayBuffer()", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "image.png")
+      const binaryContent = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])
+      await fs.writeFile(filepath, binaryContent)
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("image.png")
+          expect(result.type).toBe("text") // Images return as text with base64 encoding
+          expect(result.encoding).toBe("base64")
+          expect(result.mimeType).toBe("image/png")
+          expect(result.content).toBe(binaryContent.toString("base64"))
+        },
+      })
+    })
+
+    test("returns empty for binary non-image files", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "binary.so")
+      await fs.writeFile(filepath, Buffer.from([0x7f, 0x45, 0x4c, 0x46]), "binary")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("binary.so")
+          expect(result.type).toBe("binary")
+          expect(result.content).toBe("")
+        },
+      })
+    })
+  })
+
+  describe("File.read() - Filesystem.mimeType()", () => {
+    test("detects MIME type via Filesystem.mimeType()", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.json")
+      await fs.writeFile(filepath, '{"key": "value"}', "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          expect(Filesystem.mimeType(filepath)).toContain("application/json")
+
+          const result = await File.read("test.json")
+          expect(result.type).toBe("text")
+        },
+      })
+    })
+
+    test("handles various image MIME types", async () => {
+      await using tmp = await tmpdir()
+      const testCases = [
+        { ext: "jpg", mime: "image/jpeg" },
+        { ext: "png", mime: "image/png" },
+        { ext: "gif", mime: "image/gif" },
+        { ext: "webp", mime: "image/webp" },
+      ]
+
+      for (const { ext, mime } of testCases) {
+        const filepath = path.join(tmp.path, `test.${ext}`)
+        await fs.writeFile(filepath, Buffer.from([0x00, 0x00, 0x00, 0x00]), "binary")
+
+        await Instance.provide({
+          directory: tmp.path,
+          fn: async () => {
+            expect(Filesystem.mimeType(filepath)).toContain(mime)
+          },
+        })
+      }
+    })
+  })
+
+  describe("File.list() - Filesystem.exists() and readText()", () => {
+    test("reads .gitignore via Filesystem.exists() and readText()", async () => {
+      await using tmp = await tmpdir({ git: true })
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const gitignorePath = path.join(tmp.path, ".gitignore")
+          await fs.writeFile(gitignorePath, "node_modules\ndist\n", "utf-8")
+
+          // This is used internally in File.list()
+          expect(await Filesystem.exists(gitignorePath)).toBe(true)
+
+          const content = await Filesystem.readText(gitignorePath)
+          expect(content).toContain("node_modules")
+        },
+      })
+    })
+
+    test("reads .ignore file similarly", async () => {
+      await using tmp = await tmpdir({ git: true })
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const ignorePath = path.join(tmp.path, ".ignore")
+          await fs.writeFile(ignorePath, "*.log\n.env\n", "utf-8")
+
+          expect(await Filesystem.exists(ignorePath)).toBe(true)
+          expect(await Filesystem.readText(ignorePath)).toContain("*.log")
+        },
+      })
+    })
+
+    test("handles missing .gitignore gracefully", async () => {
+      await using tmp = await tmpdir({ git: true })
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const gitignorePath = path.join(tmp.path, ".gitignore")
+          expect(await Filesystem.exists(gitignorePath)).toBe(false)
+
+          // File.list() should still work
+          const nodes = await File.list()
+          expect(Array.isArray(nodes)).toBe(true)
+        },
+      })
+    })
+  })
+
+  describe("File.changed() - Filesystem.readText() for untracked files", () => {
+    test("reads untracked files via Filesystem.readText()", async () => {
+      await using tmp = await tmpdir({ git: true })
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const untrackedPath = path.join(tmp.path, "untracked.txt")
+          await fs.writeFile(untrackedPath, "new content\nwith multiple lines", "utf-8")
+
+          // This is how File.changed() reads untracked files
+          const content = await Filesystem.readText(untrackedPath)
+          const lines = content.split("\n").length
+          expect(lines).toBe(2)
+        },
+      })
+    })
+  })
+
+  describe("Error handling", () => {
+    test("handles errors gracefully in Filesystem.readText()", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "readonly.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const nonExistentPath = path.join(tmp.path, "does-not-exist.txt")
+          // Filesystem.readText() on non-existent file throws
+          await expect(Filesystem.readText(nonExistentPath)).rejects.toThrow()
+
+          // But File.read() handles this gracefully
+          const result = await File.read("does-not-exist.txt")
+          expect(result.content).toBe("")
+        },
+      })
+    })
+
+    test("handles errors in Filesystem.readArrayBuffer()", async () => {
+      await using tmp = await tmpdir()
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const nonExistentPath = path.join(tmp.path, "does-not-exist.bin")
+          const buffer = await Filesystem.readArrayBuffer(nonExistentPath).catch(() => new ArrayBuffer(0))
+          expect(buffer.byteLength).toBe(0)
+        },
+      })
+    })
+
+    test("returns empty array buffer on error for images", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "broken.png")
+      // Don't create the file
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          // File.read() handles missing images gracefully
+          const result = await File.read("broken.png")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("")
+        },
+      })
+    })
+  })
+
+  describe("shouldEncode() logic", () => {
+    test("treats .ts files as text", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.ts")
+      await fs.writeFile(filepath, "export const value = 1", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.ts")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("export const value = 1")
+        },
+      })
+    })
+
+    test("treats .mts files as text", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.mts")
+      await fs.writeFile(filepath, "export const value = 1", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.mts")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("export const value = 1")
+        },
+      })
+    })
+
+    test("treats .sh files as text", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.sh")
+      await fs.writeFile(filepath, "#!/usr/bin/env bash\necho hello", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.sh")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("#!/usr/bin/env bash\necho hello")
+        },
+      })
+    })
+
+    test("treats Dockerfile as text", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "Dockerfile")
+      await fs.writeFile(filepath, "FROM alpine:3.20", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("Dockerfile")
+          expect(result.type).toBe("text")
+          expect(result.content).toBe("FROM alpine:3.20")
+        },
+      })
+    })
+
+    test("returns encoding info for text files", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      await fs.writeFile(filepath, "simple text", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.txt")
+          expect(result.encoding).toBeUndefined()
+          expect(result.type).toBe("text")
+        },
+      })
+    })
+
+    test("returns base64 encoding for images", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.jpg")
+      await fs.writeFile(filepath, Buffer.from([0xff, 0xd8, 0xff, 0xe0]), "binary")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await File.read("test.jpg")
+          expect(result.encoding).toBe("base64")
+          expect(result.mimeType).toBe("image/jpeg")
+        },
+      })
+    })
+  })
+
+  describe("Path security", () => {
+    test("throws for paths outside project directory", async () => {
+      await using tmp = await tmpdir()
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          await expect(File.read("../outside.txt")).rejects.toThrow("Access denied")
+        },
+      })
+    })
+
+    test("throws for paths outside project directory", async () => {
+      await using tmp = await tmpdir()
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          await expect(File.read("../outside.txt")).rejects.toThrow("Access denied")
+        },
+      })
+    })
+  })
+})

packages/opencode/test/file/time.test.ts

@@ -0,0 +1,361 @@
+import { describe, test, expect, beforeEach } from "bun:test"
+import path from "path"
+import fs from "fs/promises"
+import { FileTime } from "../../src/file/time"
+import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
+import { tmpdir } from "../fixture/fixture"
+
+describe("file/time", () => {
+  const sessionID = "test-session-123"
+
+  describe("read() and get()", () => {
+    test("stores read timestamp", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const before = FileTime.get(sessionID, filepath)
+          expect(before).toBeUndefined()
+
+          FileTime.read(sessionID, filepath)
+
+          const after = FileTime.get(sessionID, filepath)
+          expect(after).toBeInstanceOf(Date)
+          expect(after!.getTime()).toBeGreaterThan(0)
+        },
+      })
+    })
+
+    test("tracks separate timestamps per session", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read("session1", filepath)
+          FileTime.read("session2", filepath)
+
+          const time1 = FileTime.get("session1", filepath)
+          const time2 = FileTime.get("session2", filepath)
+
+          expect(time1).toBeDefined()
+          expect(time2).toBeDefined()
+        },
+      })
+    })
+
+    test("updates timestamp on subsequent reads", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(sessionID, filepath)
+          const first = FileTime.get(sessionID, filepath)!
+
+          await new Promise((resolve) => setTimeout(resolve, 10))
+
+          FileTime.read(sessionID, filepath)
+          const second = FileTime.get(sessionID, filepath)!
+
+          expect(second.getTime()).toBeGreaterThanOrEqual(first.getTime())
+        },
+      })
+    })
+  })
+
+  describe("assert()", () => {
+    test("passes when file has not been modified", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(sessionID, filepath)
+
+          // Should not throw
+          await FileTime.assert(sessionID, filepath)
+        },
+      })
+    })
+
+    test("throws when file was not read first", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow("You must read file")
+        },
+      })
+    })
+
+    test("throws when file was modified after read", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(sessionID, filepath)
+
+          // Wait to ensure different timestamps
+          await new Promise((resolve) => setTimeout(resolve, 100))
+
+          // Modify file after reading
+          await fs.writeFile(filepath, "modified content", "utf-8")
+
+          await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow("modified since it was last read")
+        },
+      })
+    })
+
+    test("includes timestamps in error message", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(sessionID, filepath)
+          await new Promise((resolve) => setTimeout(resolve, 100))
+          await fs.writeFile(filepath, "modified", "utf-8")
+
+          let error: Error | undefined
+          try {
+            await FileTime.assert(sessionID, filepath)
+          } catch (e) {
+            error = e as Error
+          }
+          expect(error).toBeDefined()
+          expect(error!.message).toContain("Last modification:")
+          expect(error!.message).toContain("Last read:")
+        },
+      })
+    })
+
+    test("skips check when OPENCODE_DISABLE_FILETIME_CHECK is true", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const { Flag } = await import("../../src/flag/flag")
+          const original = Flag.OPENCODE_DISABLE_FILETIME_CHECK
+          ;(Flag as { OPENCODE_DISABLE_FILETIME_CHECK: boolean }).OPENCODE_DISABLE_FILETIME_CHECK = true
+
+          try {
+            // Should not throw even though file wasn't read
+            await FileTime.assert(sessionID, filepath)
+          } finally {
+            ;(Flag as { OPENCODE_DISABLE_FILETIME_CHECK: boolean }).OPENCODE_DISABLE_FILETIME_CHECK = original
+          }
+        },
+      })
+    })
+  })
+
+  describe("withLock()", () => {
+    test("executes function within lock", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          let executed = false
+          await FileTime.withLock(filepath, async () => {
+            executed = true
+            return "result"
+          })
+          expect(executed).toBe(true)
+        },
+      })
+    })
+
+    test("returns function result", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const result = await FileTime.withLock(filepath, async () => {
+            return "success"
+          })
+          expect(result).toBe("success")
+        },
+      })
+    })
+
+    test("serializes concurrent operations on same file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const order: number[] = []
+
+          const op1 = FileTime.withLock(filepath, async () => {
+            order.push(1)
+            await new Promise((resolve) => setTimeout(resolve, 10))
+            order.push(2)
+          })
+
+          const op2 = FileTime.withLock(filepath, async () => {
+            order.push(3)
+            order.push(4)
+          })
+
+          await Promise.all([op1, op2])
+
+          // Operations should be serialized
+          expect(order).toContain(1)
+          expect(order).toContain(2)
+          expect(order).toContain(3)
+          expect(order).toContain(4)
+        },
+      })
+    })
+
+    test("allows concurrent operations on different files", async () => {
+      await using tmp = await tmpdir()
+      const filepath1 = path.join(tmp.path, "file1.txt")
+      const filepath2 = path.join(tmp.path, "file2.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          let started1 = false
+          let started2 = false
+
+          const op1 = FileTime.withLock(filepath1, async () => {
+            started1 = true
+            await new Promise((resolve) => setTimeout(resolve, 50))
+            expect(started2).toBe(true) // op2 should have started while op1 is running
+          })
+
+          const op2 = FileTime.withLock(filepath2, async () => {
+            started2 = true
+          })
+
+          await Promise.all([op1, op2])
+
+          expect(started1).toBe(true)
+          expect(started2).toBe(true)
+        },
+      })
+    })
+
+    test("releases lock even if function throws", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          await expect(
+            FileTime.withLock(filepath, async () => {
+              throw new Error("Test error")
+            }),
+          ).rejects.toThrow("Test error")
+
+          // Lock should be released, subsequent operations should work
+          let executed = false
+          await FileTime.withLock(filepath, async () => {
+            executed = true
+          })
+          expect(executed).toBe(true)
+        },
+      })
+    })
+
+    test("deadlocks on nested locks (expected behavior)", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          // Nested locks on same file cause deadlock - this is expected
+          // The outer lock waits for inner to complete, but inner waits for outer to release
+          const timeout = new Promise<never>((_, reject) =>
+            setTimeout(() => reject(new Error("Deadlock detected")), 100),
+          )
+
+          const nestedLock = FileTime.withLock(filepath, async () => {
+            return FileTime.withLock(filepath, async () => {
+              return "inner"
+            })
+          })
+
+          // Should timeout due to deadlock
+          await expect(Promise.race([nestedLock, timeout])).rejects.toThrow("Deadlock detected")
+        },
+      })
+    })
+  })
+
+  describe("stat() Filesystem.stat pattern", () => {
+    test("reads file modification time via Filesystem.stat()", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(sessionID, filepath)
+
+          const stats = Filesystem.stat(filepath)
+          expect(stats?.mtime).toBeInstanceOf(Date)
+          expect(stats!.mtime.getTime()).toBeGreaterThan(0)
+
+          // FileTime.assert uses this stat internally
+          await FileTime.assert(sessionID, filepath)
+        },
+      })
+    })
+
+    test("detects modification via stat mtime", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "original", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(sessionID, filepath)
+
+          const originalStat = Filesystem.stat(filepath)
+
+          // Wait and modify
+          await new Promise((resolve) => setTimeout(resolve, 100))
+          await fs.writeFile(filepath, "modified", "utf-8")
+
+          const newStat = Filesystem.stat(filepath)
+          expect(newStat!.mtime.getTime()).toBeGreaterThan(originalStat!.mtime.getTime())
+
+          await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow()
+        },
+      })
+    })
+  })
+})

packages/opencode/test/fixture/skills/agents-sdk/SKILL.md

@@ -0,0 +1,152 @@
+---
+name: agents-sdk
+description: Build AI agents on Cloudflare Workers using the Agents SDK. Load when creating stateful agents, durable workflows, real-time WebSocket apps, scheduled tasks, MCP servers, or chat applications. Covers Agent class, state management, callable RPC, Workflows integration, and React hooks.
+---
+
+# Cloudflare Agents SDK
+
+**STOP.** Your knowledge of the Agents SDK may be outdated. Prefer retrieval over pre-training for any Agents SDK task.
+
+## Documentation
+
+Fetch current docs from `https://github.com/cloudflare/agents/tree/main/docs` before implementing.
+
+| Topic               | Doc                           | Use for                                        |
+| ------------------- | ----------------------------- | ---------------------------------------------- |
+| Getting started     | `docs/getting-started.md`     | First agent, project setup                     |
+| State               | `docs/state.md`               | `setState`, `validateStateChange`, persistence |
+| Routing             | `docs/routing.md`             | URL patterns, `routeAgentRequest`, `basePath`  |
+| Callable methods    | `docs/callable-methods.md`    | `@callable`, RPC, streaming, timeouts          |
+| Scheduling          | `docs/scheduling.md`          | `schedule()`, `scheduleEvery()`, cron          |
+| Workflows           | `docs/workflows.md`           | `AgentWorkflow`, durable multi-step tasks      |
+| HTTP/WebSockets     | `docs/http-websockets.md`     | Lifecycle hooks, hibernation                   |
+| Email               | `docs/email.md`               | Email routing, secure reply resolver           |
+| MCP client          | `docs/mcp-client.md`          | Connecting to MCP servers                      |
+| MCP server          | `docs/mcp-servers.md`         | Building MCP servers with `McpAgent`           |
+| Client SDK          | `docs/client-sdk.md`          | `useAgent`, `useAgentChat`, React hooks        |
+| Human-in-the-loop   | `docs/human-in-the-loop.md`   | Approval flows, pausing workflows              |
+| Resumable streaming | `docs/resumable-streaming.md` | Stream recovery on disconnect                  |
+
+Cloudflare docs: https://developers.cloudflare.com/agents/
+
+## Capabilities
+
+The Agents SDK provides:
+
+- **Persistent state** - SQLite-backed, auto-synced to clients
+- **Callable RPC** - `@callable()` methods invoked over WebSocket
+- **Scheduling** - One-time, recurring (`scheduleEvery`), and cron tasks
+- **Workflows** - Durable multi-step background processing via `AgentWorkflow`
+- **MCP integration** - Connect to MCP servers or build your own with `McpAgent`
+- **Email handling** - Receive and reply to emails with secure routing
+- **Streaming chat** - `AIChatAgent` with resumable streams
+- **React hooks** - `useAgent`, `useAgentChat` for client apps
+
+## FIRST: Verify Installation
+
+```bash
+npm ls agents  # Should show agents package
+```
+
+If not installed:
+
+```bash
+npm install agents
+```
+
+## Wrangler Configuration
+
+```jsonc
+{
+  "durable_objects": {
+    "bindings": [{ "name": "MyAgent", "class_name": "MyAgent" }],
+  },
+  "migrations": [{ "tag": "v1", "new_sqlite_classes": ["MyAgent"] }],
+}
+```
+
+## Agent Class
+
+```typescript
+import { Agent, routeAgentRequest, callable } from "agents"
+
+type State = { count: number }
+
+export class Counter extends Agent<Env, State> {
+  initialState = { count: 0 }
+
+  // Validation hook - runs before state persists (sync, throwing rejects the update)
+  validateStateChange(nextState: State, source: Connection | "server") {
+    if (nextState.count < 0) throw new Error("Count cannot be negative")
+  }
+
+  // Notification hook - runs after state persists (async, non-blocking)
+  onStateUpdate(state: State, source: Connection | "server") {
+    console.log("State updated:", state)
+  }
+
+  @callable()
+  increment() {
+    this.setState({ count: this.state.count + 1 })
+    return this.state.count
+  }
+}
+
+export default {
+  fetch: (req, env) => routeAgentRequest(req, env) ?? new Response("Not found", { status: 404 }),
+}
+```
+
+## Routing
+
+Requests route to `/agents/{agent-name}/{instance-name}`:
+
+| Class      | URL                        |
+| ---------- | -------------------------- |
+| `Counter`  | `/agents/counter/user-123` |
+| `ChatRoom` | `/agents/chat-room/lobby`  |
+
+Client: `useAgent({ agent: "Counter", name: "user-123" })`
+
+## Core APIs
+
+| Task                | API                                                    |
+| ------------------- | ------------------------------------------------------ |
+| Read state          | `this.state.count`                                     |
+| Write state         | `this.setState({ count: 1 })`                          |
+| SQL query           | `` this.sql`SELECT * FROM users WHERE id = ${id}` ``   |
+| Schedule (delay)    | `await this.schedule(60, "task", payload)`             |
+| Schedule (cron)     | `await this.schedule("0 * * * *", "task", payload)`    |
+| Schedule (interval) | `await this.scheduleEvery(30, "poll")`                 |
+| RPC method          | `@callable() myMethod() { ... }`                       |
+| Streaming RPC       | `@callable({ streaming: true }) stream(res) { ... }`   |
+| Start workflow      | `await this.runWorkflow("ProcessingWorkflow", params)` |
+
+## React Client
+
+```tsx
+import { useAgent } from "agents/react"
+
+function App() {
+  const [state, setLocalState] = useState({ count: 0 })
+
+  const agent = useAgent({
+    agent: "Counter",
+    name: "my-instance",
+    onStateUpdate: (newState) => setLocalState(newState),
+    onIdentity: (name, agentType) => console.log(`Connected to ${name}`),
+  })
+
+  return <button onClick={() => agent.setState({ count: state.count + 1 })}>Count: {state.count}</button>
+}
+```
+
+## References
+
+- **[references/workflows.md](references/workflows.md)** - Durable Workflows integration
+- **[references/callable.md](references/callable.md)** - RPC methods, streaming, timeouts
+- **[references/state-scheduling.md](references/state-scheduling.md)** - State persistence, scheduling
+- **[references/streaming-chat.md](references/streaming-chat.md)** - AIChatAgent, resumable streams
+- **[references/mcp.md](references/mcp.md)** - MCP server integration
+- **[references/email.md](references/email.md)** - Email routing and handling
+- **[references/codemode.md](references/codemode.md)** - Code Mode (experimental)

packages/opencode/test/fixture/skills/agents-sdk/references/callable.md

@@ -0,0 +1,92 @@
+# Callable Methods
+
+Fetch `docs/callable-methods.md` from `https://github.com/cloudflare/agents/tree/main/docs` for complete documentation.
+
+## Overview
+
+`@callable()` exposes agent methods to clients via WebSocket RPC.
+
+```typescript
+import { Agent, callable } from "agents"
+
+export class MyAgent extends Agent<Env, State> {
+  @callable()
+  async greet(name: string): Promise<string> {
+    return `Hello, ${name}!`
+  }
+
+  @callable()
+  async processData(data: unknown): Promise<Result> {
+    // Long-running work
+    return result
+  }
+}
+```
+
+## Client Usage
+
+```typescript
+// Basic call
+const greeting = await agent.call("greet", ["World"])
+
+// With timeout
+const result = await agent.call("processData", [data], {
+  timeout: 5000, // 5 second timeout
+})
+```
+
+## Streaming Responses
+
+```typescript
+import { Agent, callable, StreamingResponse } from "agents"
+
+export class MyAgent extends Agent<Env, State> {
+  @callable({ streaming: true })
+  async streamResults(stream: StreamingResponse, query: string) {
+    for await (const item of fetchResults(query)) {
+      stream.send(JSON.stringify(item))
+    }
+    stream.close()
+  }
+
+  @callable({ streaming: true })
+  async streamWithError(stream: StreamingResponse) {
+    try {
+      // ... work
+    } catch (error) {
+      stream.error(error.message) // Signal error to client
+      return
+    }
+    stream.close()
+  }
+}
+```
+
+Client with streaming:
+
+```typescript
+await agent.call("streamResults", ["search term"], {
+  stream: {
+    onChunk: (data) => console.log("Chunk:", data),
+    onDone: () => console.log("Complete"),
+    onError: (error) => console.error("Error:", error),
+  },
+})
+```
+
+## Introspection
+
+```typescript
+// Get list of callable methods on an agent
+const methods = await agent.call("getCallableMethods", [])
+// Returns: ["greet", "processData", "streamResults", ...]
+```
+
+## When to Use
+
+| Scenario                             | Use                         |
+| ------------------------------------ | --------------------------- |
+| Browser/mobile calling agent         | `@callable()`               |
+| External service calling agent       | `@callable()`               |
+| Worker calling agent (same codebase) | DO RPC directly             |
+| Agent calling another agent          | `getAgentByName()` + DO RPC |

packages/opencode/test/fixture/skills/cloudflare/SKILL.md

@@ -0,0 +1,211 @@
+---
+name: cloudflare
+description: Comprehensive Cloudflare platform skill covering Workers, Pages, storage (KV, D1, R2), AI (Workers AI, Vectorize, Agents SDK), networking (Tunnel, Spectrum), security (WAF, DDoS), and infrastructure-as-code (Terraform, Pulumi). Use for any Cloudflare development task.
+references:
+  - workers
+  - pages
+  - d1
+  - durable-objects
+  - workers-ai
+---
+
+# Cloudflare Platform Skill
+
+Consolidated skill for building on the Cloudflare platform. Use decision trees below to find the right product, then load detailed references.
+
+## Quick Decision Trees
+
+### "I need to run code"
+
+```
+Need to run code?
+├─ Serverless functions at the edge → workers/
+├─ Full-stack web app with Git deploys → pages/
+├─ Stateful coordination/real-time → durable-objects/
+├─ Long-running multi-step jobs → workflows/
+├─ Run containers → containers/
+├─ Multi-tenant (customers deploy code) → workers-for-platforms/
+├─ Scheduled tasks (cron) → cron-triggers/
+├─ Lightweight edge logic (modify HTTP) → snippets/
+├─ Process Worker execution events (logs/observability) → tail-workers/
+└─ Optimize latency to backend infrastructure → smart-placement/
+```
+
+### "I need to store data"
+
+```
+Need storage?
+├─ Key-value (config, sessions, cache) → kv/
+├─ Relational SQL → d1/ (SQLite) or hyperdrive/ (existing Postgres/MySQL)
+├─ Object/file storage (S3-compatible) → r2/
+├─ Message queue (async processing) → queues/
+├─ Vector embeddings (AI/semantic search) → vectorize/
+├─ Strongly-consistent per-entity state → durable-objects/ (DO storage)
+├─ Secrets management → secrets-store/
+├─ Streaming ETL to R2 → pipelines/
+└─ Persistent cache (long-term retention) → cache-reserve/
+```
+
+### "I need AI/ML"
+
+```
+Need AI?
+├─ Run inference (LLMs, embeddings, images) → workers-ai/
+├─ Vector database for RAG/search → vectorize/
+├─ Build stateful AI agents → agents-sdk/
+├─ Gateway for any AI provider (caching, routing) → ai-gateway/
+└─ AI-powered search widget → ai-search/
+```
+
+### "I need networking/connectivity"
+
+```
+Need networking?
+├─ Expose local service to internet → tunnel/
+├─ TCP/UDP proxy (non-HTTP) → spectrum/
+├─ WebRTC TURN server → turn/
+├─ Private network connectivity → network-interconnect/
+├─ Optimize routing → argo-smart-routing/
+├─ Optimize latency to backend (not user) → smart-placement/
+└─ Real-time video/audio → realtimekit/ or realtime-sfu/
+```
+
+### "I need security"
+
+```
+Need security?
+├─ Web Application Firewall → waf/
+├─ DDoS protection → ddos/
+├─ Bot detection/management → bot-management/
+├─ API protection → api-shield/
+├─ CAPTCHA alternative → turnstile/
+└─ Credential leak detection → waf/ (managed ruleset)
+```
+
+### "I need media/content"
+
+```
+Need media?
+├─ Image optimization/transformation → images/
+├─ Video streaming/encoding → stream/
+├─ Browser automation/screenshots → browser-rendering/
+└─ Third-party script management → zaraz/
+```
+
+### "I need infrastructure-as-code"
+
+```
+Need IaC? → pulumi/ (Pulumi), terraform/ (Terraform), or api/ (REST API)
+```
+
+## Product Index
+
+### Compute & Runtime
+
+| Product               | Reference                           |
+| --------------------- | ----------------------------------- |
+| Workers               | `references/workers/`               |
+| Pages                 | `references/pages/`                 |
+| Pages Functions       | `references/pages-functions/`       |
+| Durable Objects       | `references/durable-objects/`       |
+| Workflows             | `references/workflows/`             |
+| Containers            | `references/containers/`            |
+| Workers for Platforms | `references/workers-for-platforms/` |
+| Cron Triggers         | `references/cron-triggers/`         |
+| Tail Workers          | `references/tail-workers/`          |
+| Snippets              | `references/snippets/`              |
+| Smart Placement       | `references/smart-placement/`       |
+
+### Storage & Data
+
+| Product         | Reference                     |
+| --------------- | ----------------------------- |
+| KV              | `references/kv/`              |
+| D1              | `references/d1/`              |
+| R2              | `references/r2/`              |
+| Queues          | `references/queues/`          |
+| Hyperdrive      | `references/hyperdrive/`      |
+| DO Storage      | `references/do-storage/`      |
+| Secrets Store   | `references/secrets-store/`   |
+| Pipelines       | `references/pipelines/`       |
+| R2 Data Catalog | `references/r2-data-catalog/` |
+| R2 SQL          | `references/r2-sql/`          |
+
+### AI & Machine Learning
+
+| Product    | Reference                |
+| ---------- | ------------------------ |
+| Workers AI | `references/workers-ai/` |
+| Vectorize  | `references/vectorize/`  |
+| Agents SDK | `references/agents-sdk/` |
+| AI Gateway | `references/ai-gateway/` |
+| AI Search  | `references/ai-search/`  |
+
+### Networking & Connectivity
+
+| Product              | Reference                          |
+| -------------------- | ---------------------------------- |
+| Tunnel               | `references/tunnel/`               |
+| Spectrum             | `references/spectrum/`             |
+| TURN                 | `references/turn/`                 |
+| Network Interconnect | `references/network-interconnect/` |
+| Argo Smart Routing   | `references/argo-smart-routing/`   |
+| Workers VPC          | `references/workers-vpc/`          |
+
+### Security
+
+| Product         | Reference                    |
+| --------------- | ---------------------------- |
+| WAF             | `references/waf/`            |
+| DDoS Protection | `references/ddos/`           |
+| Bot Management  | `references/bot-management/` |
+| API Shield      | `references/api-shield/`     |
+| Turnstile       | `references/turnstile/`      |
+
+### Media & Content
+
+| Product           | Reference                       |
+| ----------------- | ------------------------------- |
+| Images            | `references/images/`            |
+| Stream            | `references/stream/`            |
+| Browser Rendering | `references/browser-rendering/` |
+| Zaraz             | `references/zaraz/`             |
+
+### Real-Time Communication
+
+| Product      | Reference                  |
+| ------------ | -------------------------- |
+| RealtimeKit  | `references/realtimekit/`  |
+| Realtime SFU | `references/realtime-sfu/` |
+
+### Developer Tools
+
+| Product            | Reference                        |
+| ------------------ | -------------------------------- |
+| Wrangler           | `references/wrangler/`           |
+| Miniflare          | `references/miniflare/`          |
+| C3                 | `references/c3/`                 |
+| Observability      | `references/observability/`      |
+| Analytics Engine   | `references/analytics-engine/`   |
+| Web Analytics      | `references/web-analytics/`      |
+| Sandbox            | `references/sandbox/`            |
+| Workerd            | `references/workerd/`            |
+| Workers Playground | `references/workers-playground/` |
+
+### Infrastructure as Code
+
+| Product   | Reference               |
+| --------- | ----------------------- |
+| Pulumi    | `references/pulumi/`    |
+| Terraform | `references/terraform/` |
+| API       | `references/api/`       |
+
+### Other Services
+
+| Product       | Reference                   |
+| ------------- | --------------------------- |
+| Email Routing | `references/email-routing/` |
+| Email Workers | `references/email-workers/` |
+| Static Assets | `references/static-assets/` |
+| Bindings      | `references/bindings/`      |
+| Cache Reserve | `references/cache-reserve/` |

packages/opencode/test/fixture/skills/index.json

@@ -0,0 +1,6 @@
+{
+  "skills": [
+    { "name": "agents-sdk", "description": "Cloudflare Agents SDK", "files": ["SKILL.md", "references/callable.md"] },
+    { "name": "cloudflare", "description": "Cloudflare Platform Skill", "files": ["SKILL.md"] }
+  ]
+}

packages/opencode/test/project/project.test.ts

@@ -4,6 +4,7 @@ import { Log } from "../../src/util/log"
 import { $ } from "bun"
 import path from "path"
 import { tmpdir } from "../fixture/fixture"
+import { Filesystem } from "../../src/util/filesystem"
 import { GlobalBus } from "../../src/bus/global"
 
 Log.init({ print: false })
@@ -78,7 +79,7 @@ describe("Project.fromDirectory", () => {
     expect(project.worktree).toBe(tmp.path)
 
     const opencodeFile = path.join(tmp.path, ".git", "opencode")
-    const fileExists = await Bun.file(opencodeFile).exists()
+    const fileExists = await Filesystem.exists(opencodeFile)
     expect(fileExists).toBe(false)
   })
 
@@ -94,7 +95,7 @@ describe("Project.fromDirectory", () => {
     expect(project.worktree).toBe(tmp.path)
 
     const opencodeFile = path.join(tmp.path, ".git", "opencode")
-    const fileExists = await Bun.file(opencodeFile).exists()
+    const fileExists = await Filesystem.exists(opencodeFile)
     expect(fileExists).toBe(true)
   })
 

packages/opencode/test/project/worktree-remove.test.ts

@@ -4,6 +4,7 @@ import fs from "fs/promises"
 import path from "path"
 import { Instance } from "../../src/project/instance"
 import { Worktree } from "../../src/worktree"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 
 describe("Worktree.remove", () => {
@@ -53,7 +54,7 @@ describe("Worktree.remove", () => {
     })()
 
     expect(ok).toBe(true)
-    expect(await Bun.file(dir).exists()).toBe(false)
+    expect(await Filesystem.exists(dir)).toBe(false)
 
     const list = await $`git worktree list --porcelain`.cwd(root).quiet().text()
     expect(list).not.toContain(`worktree ${dir}`)

packages/opencode/test/provider/amazon-bedrock.test.ts

@@ -7,11 +7,12 @@ import { Instance } from "../../src/project/instance"
 import { Provider } from "../../src/provider/provider"
 import { Env } from "../../src/env"
 import { Global } from "../../src/global"
+import { Filesystem } from "../../src/util/filesystem"
 
 test("Bedrock: config region takes precedence over AWS_REGION env var", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -43,7 +44,7 @@ test("Bedrock: config region takes precedence over AWS_REGION env var", async ()
 test("Bedrock: falls back to AWS_REGION env var when no config region", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -68,7 +69,7 @@ test("Bedrock: falls back to AWS_REGION env var when no config region", async ()
 test("Bedrock: loads when bearer token from auth.json is present", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -89,14 +90,14 @@ test("Bedrock: loads when bearer token from auth.json is present", async () => {
   // Save original auth.json if it exists
   let originalAuth: string | undefined
   try {
-    originalAuth = await Bun.file(authPath).text()
+    originalAuth = await Filesystem.readText(authPath)
   } catch {
     // File doesn't exist, that's fine
   }
 
   try {
     // Write test auth.json
-    await Bun.write(
+    await Filesystem.write(
       authPath,
       JSON.stringify({
         "amazon-bedrock": {
@@ -122,7 +123,7 @@ test("Bedrock: loads when bearer token from auth.json is present", async () => {
   } finally {
     // Restore original or delete
     if (originalAuth !== undefined) {
-      await Bun.write(authPath, originalAuth)
+      await Filesystem.write(authPath, originalAuth)
     } else {
       try {
         await unlink(authPath)
@@ -136,7 +137,7 @@ test("Bedrock: loads when bearer token from auth.json is present", async () => {
 test("Bedrock: config profile takes precedence over AWS_PROFILE env var", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -169,7 +170,7 @@ test("Bedrock: config profile takes precedence over AWS_PROFILE env var", async
 test("Bedrock: includes custom endpoint in options when specified", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -202,7 +203,7 @@ test("Bedrock: includes custom endpoint in options when specified", async () =>
 test("Bedrock: autoloads when AWS_WEB_IDENTITY_TOKEN_FILE is present", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -240,7 +241,7 @@ test("Bedrock: autoloads when AWS_WEB_IDENTITY_TOKEN_FILE is present", async ()
 test("Bedrock: model with us. prefix should not be double-prefixed", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -277,7 +278,7 @@ test("Bedrock: model with us. prefix should not be double-prefixed", async () =>
 test("Bedrock: model with global. prefix should not be prefixed", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -313,7 +314,7 @@ test("Bedrock: model with global. prefix should not be prefixed", async () => {
 test("Bedrock: model with eu. prefix should not be double-prefixed", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",
@@ -349,7 +350,7 @@ test("Bedrock: model with eu. prefix should not be double-prefixed", async () =>
 test("Bedrock: model without prefix in US region should get us. prefix added", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://app.kilo.ai/config.json",

packages/opencode/test/provider/transform.test.ts

@@ -2378,62 +2378,6 @@ describe("ProviderTransform.variants", () => {
         expect(Object.keys(result)).toEqual(["low", "high"])
       })
     })
-
-    describe("@ai-sdk/cohere", () => {
-      test("returns empty object", () => {
-        const model = createMockModel({
-          id: "cohere/command-r",
-          providerID: "cohere",
-          api: {
-            id: "command-r",
-            url: "https://api.cohere.com",
-            npm: "@ai-sdk/cohere",
-          },
-        })
-        const result = ProviderTransform.variants(model)
-        expect(result).toEqual({})
-      })
-    })
-
-    describe("@ai-sdk/groq", () => {
-      test("returns none and WIDELY_SUPPORTED_EFFORTS with thinkingLevel", () => {
-        const model = createMockModel({
-          id: "groq/llama-4",
-          providerID: "groq",
-          api: {
-            id: "llama-4-sc",
-            url: "https://api.groq.com",
-            npm: "@ai-sdk/groq",
-          },
-        })
-        const result = ProviderTransform.variants(model)
-        expect(Object.keys(result)).toEqual(["none", "low", "medium", "high"])
-        expect(result.none).toEqual({
-          includeThoughts: true,
-          thinkingLevel: "none",
-        })
-        expect(result.low).toEqual({
-          includeThoughts: true,
-          thinkingLevel: "low",
-        })
-      })
-    })
-
-    describe("@ai-sdk/perplexity", () => {
-      test("returns empty object", () => {
-        const model = createMockModel({
-          id: "perplexity/sonar-plus",
-          providerID: "perplexity",
-          api: {
-            id: "sonar-plus",
-            url: "https://api.perplexity.ai",
-            npm: "@ai-sdk/perplexity",
-          },
-        })
-        const result = ProviderTransform.variants(model)
-        expect(result).toEqual({})
-      })
-    })
   })
 
   // kilocode_change start
@@ -2482,5 +2426,43 @@ describe("ProviderTransform.variants", () => {
       })
     })
   })
+
+  describe("@ai-sdk/groq", () => {
+    test("returns none and WIDELY_SUPPORTED_EFFORTS with thinkingLevel", () => {
+      const model = createMockModel({
+        id: "groq/llama-4",
+        providerID: "groq",
+        api: {
+          id: "llama-4-sc",
+          url: "https://api.groq.com",
+          npm: "@ai-sdk/groq",
+        },
+      })
+      const result = ProviderTransform.variants(model)
+      expect(Object.keys(result)).toEqual(["none", "low", "medium", "high"])
+      expect(result.none).toEqual({
+        reasoningEffort: "none",
+      })
+      expect(result.low).toEqual({
+        reasoningEffort: "low",
+      })
+    })
+  })
+
+  describe("@ai-sdk/perplexity", () => {
+    test("returns empty object", () => {
+      const model = createMockModel({
+        id: "perplexity/sonar-plus",
+        providerID: "perplexity",
+        api: {
+          id: "sonar-plus",
+          url: "https://api.perplexity.ai",
+          npm: "@ai-sdk/perplexity",
+        },
+      })
+      const result = ProviderTransform.variants(model)
+      expect(result).toEqual({})
+    })
+  })
 })
 // kilocode_change end

packages/opencode/test/pty/pty-output-isolation.test.ts

@@ -18,6 +18,7 @@ describe("pty", () => {
 
           const ws = {
             readyState: 1,
+            data: { events: { connection: "a" } },
             send: (data: unknown) => {
               outA.push(typeof data === "string" ? data : Buffer.from(data as Uint8Array).toString("utf8"))
             },
@@ -30,6 +31,7 @@ describe("pty", () => {
           Pty.connect(a.id, ws as any)
 
           // Now "reuse" the same ws object for another connection.
+          ws.data = { events: { connection: "b" } }
           ws.send = (data: unknown) => {
             outB.push(typeof data === "string" ? data : Buffer.from(data as Uint8Array).toString("utf8"))
           }
@@ -51,4 +53,48 @@ describe("pty", () => {
       },
     })
   })
+
+  test("does not leak output when Bun recycles websocket objects before re-connect", async () => {
+    await using dir = await tmpdir({ git: true })
+
+    await Instance.provide({
+      directory: dir.path,
+      fn: async () => {
+        const a = await Pty.create({ command: "cat", title: "a" })
+        try {
+          const outA: string[] = []
+          const outB: string[] = []
+
+          const ws = {
+            readyState: 1,
+            data: { events: { connection: "a" } },
+            send: (data: unknown) => {
+              outA.push(typeof data === "string" ? data : Buffer.from(data as Uint8Array).toString("utf8"))
+            },
+            close: () => {
+              // no-op (simulate abrupt drop)
+            },
+          }
+
+          // Connect "a" first.
+          Pty.connect(a.id, ws as any)
+          outA.length = 0
+
+          // Simulate Bun reusing the same websocket object for another
+          // connection before the next onOpen calls Pty.connect.
+          ws.data = { events: { connection: "b" } }
+          ws.send = (data: unknown) => {
+            outB.push(typeof data === "string" ? data : Buffer.from(data as Uint8Array).toString("utf8"))
+          }
+
+          Pty.write(a.id, "AAA\n")
+          await Bun.sleep(100)
+
+          expect(outB.join("")).not.toContain("AAA")
+        } finally {
+          await Pty.remove(a.id)
+        }
+      },
+    })
+  })
 })

packages/opencode/test/session/llm.test.ts

@@ -7,6 +7,7 @@ import { Instance } from "../../src/project/instance"
 import { Provider } from "../../src/provider/provider"
 import { ProviderTransform } from "../../src/provider/transform"
 import { ModelsDev } from "../../src/provider/models"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 import type { Agent } from "../../src/agent/agent"
 import type { MessageV2 } from "../../src/session/message-v2"
@@ -185,7 +186,7 @@ function createChatStream(text: string) {
 
 async function loadFixture(providerID: string, modelID: string) {
   const fixturePath = path.join(import.meta.dir, "../tool/fixtures/models-api.json")
-  const data = (await Bun.file(fixturePath).json()) as Record<string, ModelsDev.Provider>
+  const data = await Filesystem.readJson<Record<string, ModelsDev.Provider>>(fixturePath)
   const provider = data[providerID]
   if (!provider) {
     throw new Error(`Missing provider in fixture: ${providerID}`)

packages/opencode/test/session/prompt-missing-file.test.ts

@@ -2,6 +2,7 @@ import path from "path"
 import { describe, expect, test } from "bun:test"
 import { Instance } from "../../src/project/instance"
 import { Session } from "../../src/session"
+import { MessageV2 } from "../../src/session/message-v2"
 import { SessionPrompt } from "../../src/session/prompt"
 import { tmpdir } from "../fixture/fixture"
 
@@ -50,4 +51,54 @@ describe("session.prompt missing file", () => {
       },
     })
   })
+
+  test("keeps stored part order stable when file resolution is async", async () => {
+    await using tmp = await tmpdir({
+      git: true,
+      config: {
+        agent: {
+          build: {
+            model: "openai/gpt-5.2",
+          },
+        },
+      },
+    })
+
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const session = await Session.create({})
+
+        const missing = path.join(tmp.path, "still-missing.ts")
+        const msg = await SessionPrompt.prompt({
+          sessionID: session.id,
+          agent: "build",
+          noReply: true,
+          parts: [
+            {
+              type: "file",
+              mime: "text/plain",
+              url: `file://${missing}`,
+              filename: "still-missing.ts",
+            },
+            { type: "text", text: "after-file" },
+          ],
+        })
+
+        if (msg.info.role !== "user") throw new Error("expected user message")
+
+        const stored = await MessageV2.get({
+          sessionID: session.id,
+          messageID: msg.info.id,
+        })
+        const text = stored.parts.filter((part) => part.type === "text").map((part) => part.text)
+
+        expect(text[0]?.startsWith("Called the Read tool with the following input:")).toBe(true)
+        expect(text[1]?.includes("Read tool failed to read")).toBe(true)
+        expect(text[2]).toBe("after-file")
+
+        await Session.remove(session.id)
+      },
+    })
+  })
 })

packages/opencode/test/skill/discovery.test.ts

@@ -1,8 +1,47 @@
-import { describe, test, expect } from "bun:test"
+import { describe, test, expect, beforeAll, afterAll } from "bun:test"
 import { Discovery } from "../../src/skill/discovery"
+import { Filesystem } from "../../src/util/filesystem"
+import { rm } from "fs/promises"
 import path from "path"
 
-const CLOUDFLARE_SKILLS_URL = "https://developers.cloudflare.com/.well-known/skills/"
+let CLOUDFLARE_SKILLS_URL: string
+let server: ReturnType<typeof Bun.serve>
+let downloadCount = 0
+
+const fixturePath = path.join(import.meta.dir, "../fixture/skills")
+
+beforeAll(async () => {
+  await rm(Discovery.dir(), { recursive: true, force: true })
+
+  server = Bun.serve({
+    port: 0,
+    async fetch(req) {
+      const url = new URL(req.url)
+
+      // route /.well-known/skills/* to the fixture directory
+      if (url.pathname.startsWith("/.well-known/skills/")) {
+        const filePath = url.pathname.replace("/.well-known/skills/", "")
+        const fullPath = path.join(fixturePath, filePath)
+
+        if (await Filesystem.exists(fullPath)) {
+          if (!fullPath.endsWith("index.json")) {
+            downloadCount++
+          }
+          return new Response(Bun.file(fullPath))
+        }
+      }
+
+      return new Response("Not Found", { status: 404 })
+    },
+  })
+
+  CLOUDFLARE_SKILLS_URL = `http://localhost:${server.port}/.well-known/skills/`
+})
+
+afterAll(async () => {
+  server?.stop()
+  await rm(Discovery.dir(), { recursive: true, force: true })
+})
 
 describe("Discovery.pull", () => {
   test("downloads skills from cloudflare url", async () => {
@@ -11,26 +50,27 @@ describe("Discovery.pull", () => {
     for (const dir of dirs) {
       expect(dir).toStartWith(Discovery.dir())
       const md = path.join(dir, "SKILL.md")
-      expect(await Bun.file(md).exists()).toBe(true)
+      expect(await Filesystem.exists(md)).toBe(true)
     }
-  }, 30_000)
+  })
 
   test("url without trailing slash works", async () => {
     const dirs = await Discovery.pull(CLOUDFLARE_SKILLS_URL.replace(/\/$/, ""))
     expect(dirs.length).toBeGreaterThan(0)
     for (const dir of dirs) {
       const md = path.join(dir, "SKILL.md")
-      expect(await Bun.file(md).exists()).toBe(true)
+      expect(await Filesystem.exists(md)).toBe(true)
     }
-  }, 30_000)
+  })
 
   test("returns empty array for invalid url", async () => {
-    const dirs = await Discovery.pull("https://example.invalid/.well-known/skills/")
+    const dirs = await Discovery.pull(`http://localhost:${server.port}/invalid-url/`)
     expect(dirs).toEqual([])
   })
 
   test("returns empty array for non-json response", async () => {
-    const dirs = await Discovery.pull("https://example.com/")
+    // any url not explicitly handled in server returns 404 text "Not Found"
+    const dirs = await Discovery.pull(`http://localhost:${server.port}/some-other-path/`)
     expect(dirs).toEqual([])
   })
 
@@ -38,23 +78,33 @@ describe("Discovery.pull", () => {
     const dirs = await Discovery.pull(CLOUDFLARE_SKILLS_URL)
     // find a skill dir that should have reference files (e.g. agents-sdk)
     const agentsSdk = dirs.find((d) => d.endsWith("/agents-sdk"))
+    expect(agentsSdk).toBeDefined()
     if (agentsSdk) {
       const refs = path.join(agentsSdk, "references")
-      expect(await Bun.file(path.join(agentsSdk, "SKILL.md")).exists()).toBe(true)
+      expect(await Filesystem.exists(path.join(agentsSdk, "SKILL.md"))).toBe(true)
       // agents-sdk has reference files per the index
       const refDir = await Array.fromAsync(new Bun.Glob("**/*.md").scan({ cwd: refs, onlyFiles: true }))
       expect(refDir.length).toBeGreaterThan(0)
     }
-  }, 30_000)
+  })
 
   test("caches downloaded files on second pull", async () => {
+    // clear dir and downloadCount
+    await rm(Discovery.dir(), { recursive: true, force: true })
+    downloadCount = 0
+
     // first pull to populate cache
     const first = await Discovery.pull(CLOUDFLARE_SKILLS_URL)
     expect(first.length).toBeGreaterThan(0)
+    const firstCount = downloadCount
+    expect(firstCount).toBeGreaterThan(0)
 
     // second pull should return same results from cache
     const second = await Discovery.pull(CLOUDFLARE_SKILLS_URL)
     expect(second.length).toBe(first.length)
     expect(second.sort()).toEqual(first.sort())
-  }, 60_000)
+
+    // second pull should NOT increment download count
+    expect(downloadCount).toBe(firstCount)
+  })
 })

packages/opencode/test/snapshot/snapshot.test.ts

@@ -1,7 +1,9 @@
 import { test, expect } from "bun:test"
 import { $ } from "bun"
+import fs from "fs/promises"
 import { Snapshot } from "../../src/snapshot"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 
 async function bootstrap() {
@@ -11,8 +13,8 @@ async function bootstrap() {
       const unique = Math.random().toString(36).slice(2)
       const aContent = `A${unique}`
       const bContent = `B${unique}`
-      await Bun.write(`${dir}/a.txt`, aContent)
-      await Bun.write(`${dir}/b.txt`, bContent)
+      await Filesystem.write(`${dir}/a.txt`, aContent)
+      await Filesystem.write(`${dir}/b.txt`, bContent)
       await $`git add .`.cwd(dir).quiet()
       await $`git commit --no-gpg-sign -m init`.cwd(dir).quiet()
       return {
@@ -46,11 +48,16 @@ test("revert should remove new files", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/new.txt`, "NEW")
+      await Filesystem.write(`${tmp.path}/new.txt`, "NEW")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/new.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/new.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -64,11 +71,16 @@ test("revert in subdirectory", async () => {
       expect(before).toBeTruthy()
 
       await $`mkdir -p ${tmp.path}/sub`.quiet()
-      await Bun.write(`${tmp.path}/sub/file.txt`, "SUB")
+      await Filesystem.write(`${tmp.path}/sub/file.txt`, "SUB")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/sub/file.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/sub/file.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
       // Note: revert currently only removes files, not directories
       // The empty subdirectory will remain
     },
@@ -84,18 +96,23 @@ test("multiple file operations", async () => {
       expect(before).toBeTruthy()
 
       await $`rm ${tmp.path}/a.txt`.quiet()
-      await Bun.write(`${tmp.path}/c.txt`, "C")
+      await Filesystem.write(`${tmp.path}/c.txt`, "C")
       await $`mkdir -p ${tmp.path}/dir`.quiet()
-      await Bun.write(`${tmp.path}/dir/d.txt`, "D")
-      await Bun.write(`${tmp.path}/b.txt`, "MODIFIED")
+      await Filesystem.write(`${tmp.path}/dir/d.txt`, "D")
+      await Filesystem.write(`${tmp.path}/b.txt`, "MODIFIED")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(tmp.extra.aContent)
-      expect(await Bun.file(`${tmp.path}/c.txt`).exists()).toBe(false)
+      expect(await fs.readFile(`${tmp.path}/a.txt`, "utf-8")).toBe(tmp.extra.aContent)
+      expect(
+        await fs
+          .access(`${tmp.path}/c.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
       // Note: revert currently only removes files, not directories
       // The empty directory will remain
-      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(tmp.extra.bContent)
+      expect(await fs.readFile(`${tmp.path}/b.txt`, "utf-8")).toBe(tmp.extra.bContent)
     },
   })
 })
@@ -123,13 +140,18 @@ test("binary file handling", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/image.png`, new Uint8Array([0x89, 0x50, 0x4e, 0x47]))
+      await Filesystem.write(`${tmp.path}/image.png`, new Uint8Array([0x89, 0x50, 0x4e, 0x47]))
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(`${tmp.path}/image.png`)
 
       await Snapshot.revert([patch])
-      expect(await Bun.file(`${tmp.path}/image.png`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/image.png`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -157,7 +179,7 @@ test("large file handling", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/large.txt`, "x".repeat(1024 * 1024))
+      await Filesystem.write(`${tmp.path}/large.txt`, "x".repeat(1024 * 1024))
 
       expect((await Snapshot.patch(before!)).files).toContain(`${tmp.path}/large.txt`)
     },
@@ -173,11 +195,16 @@ test("nested directory revert", async () => {
       expect(before).toBeTruthy()
 
       await $`mkdir -p ${tmp.path}/level1/level2/level3`.quiet()
-      await Bun.write(`${tmp.path}/level1/level2/level3/deep.txt`, "DEEP")
+      await Filesystem.write(`${tmp.path}/level1/level2/level3/deep.txt`, "DEEP")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/level1/level2/level3/deep.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/level1/level2/level3/deep.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -190,9 +217,9 @@ test("special characters in filenames", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/file with spaces.txt`, "SPACES")
-      await Bun.write(`${tmp.path}/file-with-dashes.txt`, "DASHES")
-      await Bun.write(`${tmp.path}/file_with_underscores.txt`, "UNDERSCORES")
+      await Filesystem.write(`${tmp.path}/file with spaces.txt`, "SPACES")
+      await Filesystem.write(`${tmp.path}/file-with-dashes.txt`, "DASHES")
+      await Filesystem.write(`${tmp.path}/file_with_underscores.txt`, "UNDERSCORES")
 
       const files = (await Snapshot.patch(before!)).files
       expect(files).toContain(`${tmp.path}/file with spaces.txt`)
@@ -225,7 +252,7 @@ test("patch with invalid hash", async () => {
       expect(before).toBeTruthy()
 
       // Create a change
-      await Bun.write(`${tmp.path}/test.txt`, "TEST")
+      await Filesystem.write(`${tmp.path}/test.txt`, "TEST")
 
       // Try to patch with invalid hash - should handle gracefully
       const patch = await Snapshot.patch("invalid-hash-12345")
@@ -273,7 +300,7 @@ test("unicode filenames", async () => {
       ]
 
       for (const file of unicodeFiles) {
-        await Bun.write(file.path, file.content)
+        await Filesystem.write(file.path, file.content)
       }
 
       const patch = await Snapshot.patch(before!)
@@ -286,7 +313,12 @@ test("unicode filenames", async () => {
       await Snapshot.revert([patch])
 
       for (const file of unicodeFiles) {
-        expect(await Bun.file(file.path).exists()).toBe(false)
+        expect(
+          await fs
+            .access(file.path)
+            .then(() => true)
+            .catch(() => false),
+        ).toBe(false)
       }
     },
   })
@@ -300,14 +332,14 @@ test.skip("unicode filenames modification and restore", async () => {
       const chineseFile = `${tmp.path}/文件.txt`
       const cyrillicFile = `${tmp.path}/файл.txt`
 
-      await Bun.write(chineseFile, "original chinese")
-      await Bun.write(cyrillicFile, "original cyrillic")
+      await Filesystem.write(chineseFile, "original chinese")
+      await Filesystem.write(cyrillicFile, "original cyrillic")
 
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(chineseFile, "modified chinese")
-      await Bun.write(cyrillicFile, "modified cyrillic")
+      await Filesystem.write(chineseFile, "modified chinese")
+      await Filesystem.write(cyrillicFile, "modified cyrillic")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(chineseFile)
@@ -315,8 +347,8 @@ test.skip("unicode filenames modification and restore", async () => {
 
       await Snapshot.revert([patch])
 
-      expect(await Bun.file(chineseFile).text()).toBe("original chinese")
-      expect(await Bun.file(cyrillicFile).text()).toBe("original cyrillic")
+      expect(await fs.readFile(chineseFile, "utf-8")).toBe("original chinese")
+      expect(await fs.readFile(cyrillicFile, "utf-8")).toBe("original cyrillic")
     },
   })
 })
@@ -331,13 +363,18 @@ test("unicode filenames in subdirectories", async () => {
 
       await $`mkdir -p "${tmp.path}/目录/подкаталог"`.quiet()
       const deepFile = `${tmp.path}/目录/подкаталог/文件.txt`
-      await Bun.write(deepFile, "deep unicode content")
+      await Filesystem.write(deepFile, "deep unicode content")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(deepFile)
 
       await Snapshot.revert([patch])
-      expect(await Bun.file(deepFile).exists()).toBe(false)
+      expect(
+        await fs
+          .access(deepFile)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -353,13 +390,18 @@ test("very long filenames", async () => {
       const longName = "a".repeat(200) + ".txt"
       const longFile = `${tmp.path}/${longName}`
 
-      await Bun.write(longFile, "long filename content")
+      await Filesystem.write(longFile, "long filename content")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(longFile)
 
       await Snapshot.revert([patch])
-      expect(await Bun.file(longFile).exists()).toBe(false)
+      expect(
+        await fs
+          .access(longFile)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -372,9 +414,9 @@ test("hidden files", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/.hidden`, "hidden content")
-      await Bun.write(`${tmp.path}/.gitignore`, "*.log")
-      await Bun.write(`${tmp.path}/.config`, "config content")
+      await Filesystem.write(`${tmp.path}/.hidden`, "hidden content")
+      await Filesystem.write(`${tmp.path}/.gitignore`, "*.log")
+      await Filesystem.write(`${tmp.path}/.config`, "config content")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(`${tmp.path}/.hidden`)
@@ -393,7 +435,7 @@ test("nested symlinks", async () => {
       expect(before).toBeTruthy()
 
       await $`mkdir -p ${tmp.path}/sub/dir`.quiet()
-      await Bun.write(`${tmp.path}/sub/dir/target.txt`, "target content")
+      await Filesystem.write(`${tmp.path}/sub/dir/target.txt`, "target content")
       await $`ln -s ${tmp.path}/sub/dir/target.txt ${tmp.path}/sub/dir/link.txt`.quiet()
       await $`ln -s ${tmp.path}/sub ${tmp.path}/sub-link`.quiet()
 
@@ -450,9 +492,9 @@ test("gitignore changes", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/.gitignore`, "*.ignored")
-      await Bun.write(`${tmp.path}/test.ignored`, "ignored content")
-      await Bun.write(`${tmp.path}/normal.txt`, "normal content")
+      await Filesystem.write(`${tmp.path}/.gitignore`, "*.ignored")
+      await Filesystem.write(`${tmp.path}/test.ignored`, "ignored content")
+      await Filesystem.write(`${tmp.path}/normal.txt`, "normal content")
 
       const patch = await Snapshot.patch(before!)
 
@@ -477,7 +519,7 @@ test("concurrent file operations during patch", async () => {
       // Start creating files
       const createPromise = (async () => {
         for (let i = 0; i < 10; i++) {
-          await Bun.write(`${tmp.path}/concurrent${i}.txt`, `concurrent${i}`)
+          await Filesystem.write(`${tmp.path}/concurrent${i}.txt`, `concurrent${i}`)
           // Small delay to simulate concurrent operations
           await new Promise((resolve) => setTimeout(resolve, 1))
         }
@@ -504,7 +546,7 @@ test("snapshot state isolation between projects", async () => {
     directory: tmp1.path,
     fn: async () => {
       const before1 = await Snapshot.track()
-      await Bun.write(`${tmp1.path}/project1.txt`, "project1 content")
+      await Filesystem.write(`${tmp1.path}/project1.txt`, "project1 content")
       const patch1 = await Snapshot.patch(before1!)
       expect(patch1.files).toContain(`${tmp1.path}/project1.txt`)
     },
@@ -514,7 +556,7 @@ test("snapshot state isolation between projects", async () => {
     directory: tmp2.path,
     fn: async () => {
       const before2 = await Snapshot.track()
-      await Bun.write(`${tmp2.path}/project2.txt`, "project2 content")
+      await Filesystem.write(`${tmp2.path}/project2.txt`, "project2 content")
       const patch2 = await Snapshot.patch(before2!)
       expect(patch2.files).toContain(`${tmp2.path}/project2.txt`)
 
@@ -544,7 +586,7 @@ test("patch detects changes in secondary worktree", async () => {
         expect(before).toBeTruthy()
 
         const worktreeFile = `${worktreePath}/worktree.txt`
-        await Bun.write(worktreeFile, "worktree content")
+        await Filesystem.write(worktreeFile, "worktree content")
 
         const patch = await Snapshot.patch(before!)
         expect(patch.files).toContain(worktreeFile)
@@ -569,7 +611,7 @@ test("revert only removes files in invoking worktree", async () => {
       },
     })
     const primaryFile = `${tmp.path}/worktree.txt`
-    await Bun.write(primaryFile, "primary content")
+    await Filesystem.write(primaryFile, "primary content")
 
     await Instance.provide({
       directory: worktreePath,
@@ -578,16 +620,21 @@ test("revert only removes files in invoking worktree", async () => {
         expect(before).toBeTruthy()
 
         const worktreeFile = `${worktreePath}/worktree.txt`
-        await Bun.write(worktreeFile, "worktree content")
+        await Filesystem.write(worktreeFile, "worktree content")
 
         const patch = await Snapshot.patch(before!)
         await Snapshot.revert([patch])
 
-        expect(await Bun.file(worktreeFile).exists()).toBe(false)
+        expect(
+          await fs
+            .access(worktreeFile)
+            .then(() => true)
+            .catch(() => false),
+        ).toBe(false)
       },
     })
 
-    expect(await Bun.file(primaryFile).text()).toBe("primary content")
+    expect(await fs.readFile(primaryFile, "utf-8")).toBe("primary content")
   } finally {
     await $`git worktree remove --force ${worktreePath}`.cwd(tmp.path).quiet().nothrow()
     await $`rm -rf ${worktreePath}`.quiet()
@@ -614,10 +661,10 @@ test("diff reports worktree-only/shared edits and ignores primary-only", async (
         const before = await Snapshot.track()
         expect(before).toBeTruthy()
 
-        await Bun.write(`${worktreePath}/worktree-only.txt`, "worktree diff content")
-        await Bun.write(`${worktreePath}/shared.txt`, "worktree edit")
-        await Bun.write(`${tmp.path}/shared.txt`, "primary edit")
-        await Bun.write(`${tmp.path}/primary-only.txt`, "primary change")
+        await Filesystem.write(`${worktreePath}/worktree-only.txt`, "worktree diff content")
+        await Filesystem.write(`${worktreePath}/shared.txt`, "worktree edit")
+        await Filesystem.write(`${tmp.path}/shared.txt`, "primary edit")
+        await Filesystem.write(`${tmp.path}/primary-only.txt`, "primary change")
 
         const diff = await Snapshot.diff(before!)
         expect(diff).toContain("worktree-only.txt")
@@ -662,8 +709,8 @@ test("diff function with various changes", async () => {
 
       // Make various changes
       await $`rm ${tmp.path}/a.txt`.quiet()
-      await Bun.write(`${tmp.path}/new.txt`, "new content")
-      await Bun.write(`${tmp.path}/b.txt`, "modified content")
+      await Filesystem.write(`${tmp.path}/new.txt`, "new content")
+      await Filesystem.write(`${tmp.path}/b.txt`, "modified content")
 
       const diff = await Snapshot.diff(before!)
       expect(diff).toContain("a.txt")
@@ -683,16 +730,26 @@ test("restore function", async () => {
 
       // Make changes
       await $`rm ${tmp.path}/a.txt`.quiet()
-      await Bun.write(`${tmp.path}/new.txt`, "new content")
-      await Bun.write(`${tmp.path}/b.txt`, "modified")
+      await Filesystem.write(`${tmp.path}/new.txt`, "new content")
+      await Filesystem.write(`${tmp.path}/b.txt`, "modified")
 
       // Restore to original state
       await Snapshot.restore(before!)
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).exists()).toBe(true)
-      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(tmp.extra.aContent)
-      expect(await Bun.file(`${tmp.path}/new.txt`).exists()).toBe(true) // New files should remain
-      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(tmp.extra.bContent)
+      expect(
+        await fs
+          .access(`${tmp.path}/a.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(true)
+      expect(await fs.readFile(`${tmp.path}/a.txt`, "utf-8")).toBe(tmp.extra.aContent)
+      expect(
+        await fs
+          .access(`${tmp.path}/new.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(true) // New files should remain
+      expect(await fs.readFile(`${tmp.path}/b.txt`, "utf-8")).toBe(tmp.extra.bContent)
     },
   })
 })
@@ -710,14 +767,19 @@ test("revert should not delete files that existed but were deleted in snapshot",
       const snapshot2 = await Snapshot.track()
       expect(snapshot2).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/a.txt`, "recreated content")
+      await Filesystem.write(`${tmp.path}/a.txt`, "recreated content")
 
       const patch = await Snapshot.patch(snapshot2!)
       expect(patch.files).toContain(`${tmp.path}/a.txt`)
 
       await Snapshot.revert([patch])
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/a.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -727,14 +789,14 @@ test("revert preserves file that existed in snapshot when deleted then recreated
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      await Bun.write(`${tmp.path}/existing.txt`, "original content")
+      await Filesystem.write(`${tmp.path}/existing.txt`, "original content")
 
       const snapshot = await Snapshot.track()
       expect(snapshot).toBeTruthy()
 
       await $`rm ${tmp.path}/existing.txt`.quiet()
-      await Bun.write(`${tmp.path}/existing.txt`, "recreated")
-      await Bun.write(`${tmp.path}/newfile.txt`, "new")
+      await Filesystem.write(`${tmp.path}/existing.txt`, "recreated")
+      await Filesystem.write(`${tmp.path}/newfile.txt`, "new")
 
       const patch = await Snapshot.patch(snapshot!)
       expect(patch.files).toContain(`${tmp.path}/existing.txt`)
@@ -742,9 +804,19 @@ test("revert preserves file that existed in snapshot when deleted then recreated
 
       await Snapshot.revert([patch])
 
-      expect(await Bun.file(`${tmp.path}/newfile.txt`).exists()).toBe(false)
-      expect(await Bun.file(`${tmp.path}/existing.txt`).exists()).toBe(true)
-      expect(await Bun.file(`${tmp.path}/existing.txt`).text()).toBe("original content")
+      expect(
+        await fs
+          .access(`${tmp.path}/newfile.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/existing.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(true)
+      expect(await fs.readFile(`${tmp.path}/existing.txt`, "utf-8")).toBe("original content")
     },
   })
 })
@@ -754,17 +826,17 @@ test("diffFull sets status based on git change type", async () => {
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      await Bun.write(`${tmp.path}/grow.txt`, "one\n")
-      await Bun.write(`${tmp.path}/trim.txt`, "line1\nline2\n")
-      await Bun.write(`${tmp.path}/delete.txt`, "gone")
+      await Filesystem.write(`${tmp.path}/grow.txt`, "one\n")
+      await Filesystem.write(`${tmp.path}/trim.txt`, "line1\nline2\n")
+      await Filesystem.write(`${tmp.path}/delete.txt`, "gone")
 
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/grow.txt`, "one\ntwo\n")
-      await Bun.write(`${tmp.path}/trim.txt`, "line1\n")
+      await Filesystem.write(`${tmp.path}/grow.txt`, "one\ntwo\n")
+      await Filesystem.write(`${tmp.path}/trim.txt`, "line1\n")
       await $`rm ${tmp.path}/delete.txt`.quiet()
-      await Bun.write(`${tmp.path}/added.txt`, "new")
+      await Filesystem.write(`${tmp.path}/added.txt`, "new")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -803,7 +875,7 @@ test("diffFull with new file additions", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/new.txt`, "new content")
+      await Filesystem.write(`${tmp.path}/new.txt`, "new content")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -829,7 +901,7 @@ test("diffFull with file modifications", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/b.txt`, "modified content")
+      await Filesystem.write(`${tmp.path}/b.txt`, "modified content")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -881,7 +953,7 @@ test("diffFull with multiple line additions", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/multi.txt`, "line1\nline2\nline3")
+      await Filesystem.write(`${tmp.path}/multi.txt`, "line1\nline2\nline3")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -907,7 +979,7 @@ test("diffFull with addition and deletion", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/added.txt`, "added content")
+      await Filesystem.write(`${tmp.path}/added.txt`, "added content")
       await $`rm ${tmp.path}/a.txt`.quiet()
 
       const after = await Snapshot.track()
@@ -941,8 +1013,8 @@ test("diffFull with multiple additions and deletions", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/multi1.txt`, "line1\nline2\nline3")
-      await Bun.write(`${tmp.path}/multi2.txt`, "single line")
+      await Filesystem.write(`${tmp.path}/multi1.txt`, "line1\nline2\nline3")
+      await Filesystem.write(`${tmp.path}/multi2.txt`, "single line")
       await $`rm ${tmp.path}/a.txt`.quiet()
       await $`rm ${tmp.path}/b.txt`.quiet()
 
@@ -1000,7 +1072,7 @@ test("diffFull with binary file changes", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/binary.bin`, new Uint8Array([0x00, 0x01, 0x02, 0x03]))
+      await Filesystem.write(`${tmp.path}/binary.bin`, new Uint8Array([0x00, 0x01, 0x02, 0x03]))
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -1020,11 +1092,11 @@ test("diffFull with whitespace changes", async () => {
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      await Bun.write(`${tmp.path}/whitespace.txt`, "line1\nline2")
+      await Filesystem.write(`${tmp.path}/whitespace.txt`, "line1\nline2")
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/whitespace.txt`, "line1\n\nline2\n")
+      await Filesystem.write(`${tmp.path}/whitespace.txt`, "line1\n\nline2\n")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()

packages/opencode/test/tool/bash.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, test } from "bun:test"
 import path from "path"
 import { BashTool } from "../../src/tool/bash"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 import type { PermissionNext } from "../../src/permission/next"
 import { Truncate } from "../../src/tool/truncation"
@@ -388,7 +389,7 @@ describe("tool.bash truncation", () => {
         const filepath = (result.metadata as any).outputPath
         expect(filepath).toBeTruthy()
 
-        const saved = await Bun.file(filepath).text()
+        const saved = await Filesystem.readText(filepath)
         const lines = saved.trim().split("\n")
         expect(lines.length).toBe(lineCount)
         expect(lines[0]).toBe("1")

packages/opencode/test/tool/edit.test.ts

@@ -0,0 +1,496 @@
+import { describe, test, expect } from "bun:test"
+import path from "path"
+import fs from "fs/promises"
+import { EditTool } from "../../src/tool/edit"
+import { Instance } from "../../src/project/instance"
+import { tmpdir } from "../fixture/fixture"
+import { FileTime } from "../../src/file/time"
+
+const ctx = {
+  sessionID: "test-edit-session",
+  messageID: "",
+  callID: "",
+  agent: "build",
+  abort: AbortSignal.any([]),
+  messages: [],
+  metadata: () => {},
+  ask: async () => {},
+}
+
+describe("tool.edit", () => {
+  describe("creating new files", () => {
+    test("creates new file when oldString is empty", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "newfile.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const edit = await EditTool.init()
+          const result = await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "",
+              newString: "new content",
+            },
+            ctx,
+          )
+
+          expect(result.metadata.diff).toContain("new content")
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("new content")
+        },
+      })
+    })
+
+    test("creates new file with nested directories", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "nested", "dir", "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const edit = await EditTool.init()
+          await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "",
+              newString: "nested file",
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("nested file")
+        },
+      })
+    })
+
+    test("emits add event for new files", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "new.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const { Bus } = await import("../../src/bus")
+          const { File } = await import("../../src/file")
+          const { FileWatcher } = await import("../../src/file/watcher")
+
+          const events: string[] = []
+          const unsubEdited = Bus.subscribe(File.Event.Edited, () => events.push("edited"))
+          const unsubUpdated = Bus.subscribe(FileWatcher.Event.Updated, () => events.push("updated"))
+
+          const edit = await EditTool.init()
+          await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "",
+              newString: "content",
+            },
+            ctx,
+          )
+
+          expect(events).toContain("edited")
+          expect(events).toContain("updated")
+          unsubEdited()
+          unsubUpdated()
+        },
+      })
+    })
+  })
+
+  describe("editing existing files", () => {
+    test("replaces text in existing file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "existing.txt")
+      await fs.writeFile(filepath, "old content here", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          const result = await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "old content",
+              newString: "new content",
+            },
+            ctx,
+          )
+
+          expect(result.output).toContain("Edit applied successfully")
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("new content here")
+        },
+      })
+    })
+
+    test("throws error when file does not exist", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "nonexistent.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: filepath,
+                oldString: "old",
+                newString: "new",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow("not found")
+        },
+      })
+    })
+
+    test("throws error when oldString equals newString", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: filepath,
+                oldString: "same",
+                newString: "same",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow("identical")
+        },
+      })
+    })
+
+    test("throws error when oldString not found in file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "actual content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: filepath,
+                oldString: "not in file",
+                newString: "replacement",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow()
+        },
+      })
+    })
+
+    test("throws error when file was not read first (FileTime)", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: filepath,
+                oldString: "content",
+                newString: "modified",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow("You must read file")
+        },
+      })
+    })
+
+    test("throws error when file has been modified since read", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "original content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          // Read first
+          FileTime.read(ctx.sessionID, filepath)
+
+          // Wait a bit to ensure different timestamps
+          await new Promise((resolve) => setTimeout(resolve, 100))
+
+          // Simulate external modification
+          await fs.writeFile(filepath, "modified externally", "utf-8")
+
+          // Try to edit with the new content
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: filepath,
+                oldString: "modified externally",
+                newString: "edited",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow("modified since it was last read")
+        },
+      })
+    })
+
+    test("replaces all occurrences with replaceAll option", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "foo bar foo baz foo", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "foo",
+              newString: "qux",
+              replaceAll: true,
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("qux bar qux baz qux")
+        },
+      })
+    })
+
+    test("emits change event for existing files", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "original", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const { Bus } = await import("../../src/bus")
+          const { File } = await import("../../src/file")
+          const { FileWatcher } = await import("../../src/file/watcher")
+
+          const events: string[] = []
+          const unsubEdited = Bus.subscribe(File.Event.Edited, () => events.push("edited"))
+          const unsubUpdated = Bus.subscribe(FileWatcher.Event.Updated, () => events.push("updated"))
+
+          const edit = await EditTool.init()
+          await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "original",
+              newString: "modified",
+            },
+            ctx,
+          )
+
+          expect(events).toContain("edited")
+          expect(events).toContain("updated")
+          unsubEdited()
+          unsubUpdated()
+        },
+      })
+    })
+  })
+
+  describe("edge cases", () => {
+    test("handles multiline replacements", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "line1\nline2\nline3", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "line2",
+              newString: "new line 2\nextra line",
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("line1\nnew line 2\nextra line\nline3")
+        },
+      })
+    })
+
+    test("handles CRLF line endings", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "line1\r\nold\r\nline3", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "old",
+              newString: "new",
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("line1\r\nnew\r\nline3")
+        },
+      })
+    })
+
+    test("throws error when oldString equals newString", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: filepath,
+                oldString: "",
+                newString: "",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow("identical")
+        },
+      })
+    })
+
+    test("throws error when path is directory", async () => {
+      await using tmp = await tmpdir()
+      const dirpath = path.join(tmp.path, "adir")
+      await fs.mkdir(dirpath)
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, dirpath)
+
+          const edit = await EditTool.init()
+          await expect(
+            edit.execute(
+              {
+                filePath: dirpath,
+                oldString: "old",
+                newString: "new",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow("directory")
+        },
+      })
+    })
+
+    test("tracks file diff statistics", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "line1\nline2\nline3", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+          const result = await edit.execute(
+            {
+              filePath: filepath,
+              oldString: "line2",
+              newString: "new line a\nnew line b",
+            },
+            ctx,
+          )
+
+          expect(result.metadata.filediff).toBeDefined()
+          expect(result.metadata.filediff.file).toBe(filepath)
+          expect(result.metadata.filediff.additions).toBeGreaterThan(0)
+        },
+      })
+    })
+  })
+
+  describe("concurrent editing", () => {
+    test("serializes concurrent edits to same file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "0", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          FileTime.read(ctx.sessionID, filepath)
+
+          const edit = await EditTool.init()
+
+          // Two concurrent edits
+          const promise1 = edit.execute(
+            {
+              filePath: filepath,
+              oldString: "0",
+              newString: "1",
+            },
+            ctx,
+          )
+
+          // Need to read again since FileTime tracks per-session
+          FileTime.read(ctx.sessionID, filepath)
+
+          const promise2 = edit.execute(
+            {
+              filePath: filepath,
+              oldString: "0",
+              newString: "2",
+            },
+            ctx,
+          )
+
+          // Both should complete without error (though one might fail due to content mismatch)
+          const results = await Promise.allSettled([promise1, promise2])
+          expect(results.some((r) => r.status === "fulfilled")).toBe(true)
+        },
+      })
+    })
+  })
+})

packages/opencode/test/tool/read.test.ts

@@ -2,6 +2,7 @@ import { describe, expect, test } from "bun:test"
 import path from "path"
 import { ReadTool } from "../../src/tool/read"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 import { PermissionNext } from "../../src/permission/next"
 import { Agent } from "../../src/agent/agent"
@@ -201,10 +202,10 @@ describe("tool.read truncation", () => {
   test("truncates large file by bytes and sets truncated metadata", async () => {
     await using tmp = await tmpdir({
       init: async (dir) => {
-        const base = await Bun.file(path.join(FIXTURES_DIR, "models-api.json")).text()
+        const base = await Filesystem.readText(path.join(FIXTURES_DIR, "models-api.json"))
         const target = 60 * 1024
         const content = base.length >= target ? base : base.repeat(Math.ceil(target / base.length))
-        await Bun.write(path.join(dir, "large.json"), content)
+        await Filesystem.write(path.join(dir, "large.json"), content)
       },
     })
     await Instance.provide({
@@ -213,8 +214,8 @@ describe("tool.read truncation", () => {
         const read = await ReadTool.init()
         const result = await read.execute({ filePath: path.join(tmp.path, "large.json") }, ctx)
         expect(result.metadata.truncated).toBe(true)
-        expect(result.output).toContain("Output truncated at")
-        expect(result.output).toContain("bytes")
+        expect(result.output).toContain("Output capped at")
+        expect(result.output).toContain("Use offset=")
       },
     })
   })
@@ -232,7 +233,8 @@ describe("tool.read truncation", () => {
         const read = await ReadTool.init()
         const result = await read.execute({ filePath: path.join(tmp.path, "many-lines.txt"), limit: 10 }, ctx)
         expect(result.metadata.truncated).toBe(true)
-        expect(result.output).toContain("File has more lines")
+        expect(result.output).toContain("Showing lines 1-10 of 100")
+        expect(result.output).toContain("Use offset=11")
         expect(result.output).toContain("line0")
         expect(result.output).toContain("line9")
         expect(result.output).not.toContain("line10")
@@ -269,6 +271,10 @@ describe("tool.read truncation", () => {
       fn: async () => {
         const read = await ReadTool.init()
         const result = await read.execute({ filePath: path.join(tmp.path, "offset.txt"), offset: 10, limit: 5 }, ctx)
+        expect(result.output).toContain("10: line10")
+        expect(result.output).toContain("14: line14")
+        expect(result.output).not.toContain("9: line10")
+        expect(result.output).not.toContain("15: line15")
         expect(result.output).toContain("line10")
         expect(result.output).toContain("line14")
         expect(result.output).not.toContain("line0")
@@ -295,6 +301,40 @@ describe("tool.read truncation", () => {
     })
   })
 
+  test("allows reading empty file at default offset", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "empty.txt"), "")
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const read = await ReadTool.init()
+        const result = await read.execute({ filePath: path.join(tmp.path, "empty.txt") }, ctx)
+        expect(result.metadata.truncated).toBe(false)
+        expect(result.output).toContain("End of file - total 0 lines")
+      },
+    })
+  })
+
+  test("throws when offset > 1 for empty file", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "empty.txt"), "")
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const read = await ReadTool.init()
+        await expect(read.execute({ filePath: path.join(tmp.path, "empty.txt"), offset: 2 }, ctx)).rejects.toThrow(
+          "Offset 2 is out of range for this file (0 lines)",
+        )
+      },
+    })
+  })
+
   test("does not mark final directory page as truncated", async () => {
     await using tmp = await tmpdir({
       init: async (dir) => {
@@ -326,7 +366,7 @@ describe("tool.read truncation", () => {
       fn: async () => {
         const read = await ReadTool.init()
         const result = await read.execute({ filePath: path.join(tmp.path, "long-line.txt") }, ctx)
-        expect(result.output).toContain("...")
+        expect(result.output).toContain("(line truncated to 2000 chars)")
         expect(result.output.length).toBeLessThan(3000)
       },
     })
@@ -351,6 +391,9 @@ describe("tool.read truncation", () => {
         expect(result.metadata.truncated).toBe(false)
         expect(result.attachments).toBeDefined()
         expect(result.attachments?.length).toBe(1)
+        expect(result.attachments?.[0]).not.toHaveProperty("id")
+        expect(result.attachments?.[0]).not.toHaveProperty("sessionID")
+        expect(result.attachments?.[0]).not.toHaveProperty("messageID")
       },
     })
   })
@@ -365,6 +408,9 @@ describe("tool.read truncation", () => {
         expect(result.attachments).toBeDefined()
         expect(result.attachments?.length).toBe(1)
         expect(result.attachments?.[0].type).toBe("file")
+        expect(result.attachments?.[0]).not.toHaveProperty("id")
+        expect(result.attachments?.[0]).not.toHaveProperty("sessionID")
+        expect(result.attachments?.[0]).not.toHaveProperty("messageID")
       },
     })
   })
@@ -421,3 +467,40 @@ describe("tool.read loaded instructions", () => {
     })
   })
 })
+
+describe("tool.read binary detection", () => {
+  test("rejects text extension files with null bytes", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        const bytes = Buffer.from([0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x00, 0x77, 0x6f, 0x72, 0x6c, 0x64])
+        await Bun.write(path.join(dir, "null-byte.txt"), bytes)
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const read = await ReadTool.init()
+        await expect(read.execute({ filePath: path.join(tmp.path, "null-byte.txt") }, ctx)).rejects.toThrow(
+          "Cannot read binary file",
+        )
+      },
+    })
+  })
+
+  test("rejects known binary extensions", async () => {
+    await using tmp = await tmpdir({
+      init: async (dir) => {
+        await Bun.write(path.join(dir, "module.wasm"), "not really wasm")
+      },
+    })
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const read = await ReadTool.init()
+        await expect(read.execute({ filePath: path.join(tmp.path, "module.wasm") }, ctx)).rejects.toThrow(
+          "Cannot read binary file",
+        )
+      },
+    })
+  })
+})

packages/opencode/test/tool/truncation.test.ts

@@ -1,6 +1,7 @@
 import { describe, test, expect, afterAll } from "bun:test"
 import { Truncate } from "../../src/tool/truncation"
 import { Identifier } from "../../src/id/id"
+import { Filesystem } from "../../src/util/filesystem"
 import fs from "fs/promises"
 import path from "path"
 
@@ -9,7 +10,7 @@ const FIXTURES_DIR = path.join(import.meta.dir, "fixtures")
 describe("Truncate", () => {
   describe("output", () => {
     test("truncates large json file by bytes", async () => {
-      const content = await Bun.file(path.join(FIXTURES_DIR, "models-api.json")).text()
+      const content = await Filesystem.readText(path.join(FIXTURES_DIR, "models-api.json"))
       const result = await Truncate.output(content)
 
       expect(result.truncated).toBe(true)
@@ -69,7 +70,7 @@ describe("Truncate", () => {
     })
 
     test("large single-line file truncates with byte message", async () => {
-      const content = await Bun.file(path.join(FIXTURES_DIR, "models-api.json")).text()
+      const content = await Filesystem.readText(path.join(FIXTURES_DIR, "models-api.json"))
       const result = await Truncate.output(content)
 
       expect(result.truncated).toBe(true)
@@ -88,7 +89,7 @@ describe("Truncate", () => {
       expect(result.outputPath).toBeDefined()
       expect(result.outputPath).toContain("tool_")
 
-      const written = await Bun.file(result.outputPath).text()
+      const written = await Filesystem.readText(result.outputPath!)
       expect(written).toBe(lines)
     })
 
@@ -139,21 +140,21 @@ describe("Truncate", () => {
       const oldTimestamp = Date.now() - 10 * DAY_MS
       const oldId = Identifier.create("tool", false, oldTimestamp)
       oldFile = path.join(Truncate.DIR, oldId)
-      await Bun.write(Bun.file(oldFile), "old content")
+      await Filesystem.write(oldFile, "old content")
 
       // Create a recent file (3 days ago)
       const recentTimestamp = Date.now() - 3 * DAY_MS
       const recentId = Identifier.create("tool", false, recentTimestamp)
       recentFile = path.join(Truncate.DIR, recentId)
-      await Bun.write(Bun.file(recentFile), "recent content")
+      await Filesystem.write(recentFile, "recent content")
 
       await Truncate.cleanup()
 
       // Old file should be deleted
-      expect(await Bun.file(oldFile).exists()).toBe(false)
+      expect(await Filesystem.exists(oldFile)).toBe(false)
 
       // Recent file should still exist
-      expect(await Bun.file(recentFile).exists()).toBe(true)
+      expect(await Filesystem.exists(recentFile)).toBe(true)
     })
   })
 })

packages/opencode/test/tool/webfetch.test.ts

@@ -46,6 +46,9 @@ describe("tool.webfetch", () => {
             expect(result.attachments?.[0].type).toBe("file")
             expect(result.attachments?.[0].mime).toBe("image/png")
             expect(result.attachments?.[0].url.startsWith("data:image/png;base64,")).toBe(true)
+            expect(result.attachments?.[0]).not.toHaveProperty("id")
+            expect(result.attachments?.[0]).not.toHaveProperty("sessionID")
+            expect(result.attachments?.[0]).not.toHaveProperty("messageID")
           },
         })
       },

packages/opencode/test/tool/write.test.ts

@@ -0,0 +1,341 @@
+import { describe, test, expect } from "bun:test"
+import path from "path"
+import fs from "fs/promises"
+import { WriteTool } from "../../src/tool/write"
+import { Instance } from "../../src/project/instance"
+import { tmpdir } from "../fixture/fixture"
+
+const ctx = {
+  sessionID: "test-write-session",
+  messageID: "",
+  callID: "",
+  agent: "build",
+  abort: AbortSignal.any([]),
+  messages: [],
+  metadata: () => {},
+  ask: async () => {},
+}
+
+describe("tool.write", () => {
+  describe("new file creation", () => {
+    test("writes content to new file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "newfile.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          const result = await write.execute(
+            {
+              filePath: filepath,
+              content: "Hello, World!",
+            },
+            ctx,
+          )
+
+          expect(result.output).toContain("Wrote file successfully")
+          expect(result.metadata.exists).toBe(false)
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("Hello, World!")
+        },
+      })
+    })
+
+    test("creates parent directories if needed", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "nested", "deep", "file.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content: "nested content",
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("nested content")
+        },
+      })
+    })
+
+    test("handles relative paths by resolving to instance directory", async () => {
+      await using tmp = await tmpdir()
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: "relative.txt",
+              content: "relative content",
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(path.join(tmp.path, "relative.txt"), "utf-8")
+          expect(content).toBe("relative content")
+        },
+      })
+    })
+  })
+
+  describe("existing file overwrite", () => {
+    test("overwrites existing file content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "existing.txt")
+      await fs.writeFile(filepath, "old content", "utf-8")
+
+      // First read the file to satisfy FileTime requirement
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const { FileTime } = await import("../../src/file/time")
+          FileTime.read(ctx.sessionID, filepath)
+
+          const write = await WriteTool.init()
+          const result = await write.execute(
+            {
+              filePath: filepath,
+              content: "new content",
+            },
+            ctx,
+          )
+
+          expect(result.output).toContain("Wrote file successfully")
+          expect(result.metadata.exists).toBe(true)
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("new content")
+        },
+      })
+    })
+
+    test("returns diff in metadata for existing files", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "file.txt")
+      await fs.writeFile(filepath, "old", "utf-8")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const { FileTime } = await import("../../src/file/time")
+          FileTime.read(ctx.sessionID, filepath)
+
+          const write = await WriteTool.init()
+          const result = await write.execute(
+            {
+              filePath: filepath,
+              content: "new",
+            },
+            ctx,
+          )
+
+          // Diff should be in metadata
+          expect(result.metadata).toHaveProperty("filepath", filepath)
+          expect(result.metadata).toHaveProperty("exists", true)
+        },
+      })
+    })
+  })
+
+  describe("file permissions", () => {
+    test("sets file permissions when writing sensitive data", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "sensitive.json")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content: JSON.stringify({ secret: "data" }),
+            },
+            ctx,
+          )
+
+          // On Unix systems, check permissions
+          if (process.platform !== "win32") {
+            const stats = await fs.stat(filepath)
+            expect(stats.mode & 0o777).toBe(0o644)
+          }
+        },
+      })
+    })
+  })
+
+  describe("content types", () => {
+    test("writes JSON content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "data.json")
+      const data = { key: "value", nested: { array: [1, 2, 3] } }
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content: JSON.stringify(data, null, 2),
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(JSON.parse(content)).toEqual(data)
+        },
+      })
+    })
+
+    test("writes binary-safe content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "binary.bin")
+      const content = "Hello\x00World\x01\x02\x03"
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content,
+            },
+            ctx,
+          )
+
+          const buf = await fs.readFile(filepath)
+          expect(buf.toString()).toBe(content)
+        },
+      })
+    })
+
+    test("writes empty content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "empty.txt")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content: "",
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe("")
+
+          const stats = await fs.stat(filepath)
+          expect(stats.size).toBe(0)
+        },
+      })
+    })
+
+    test("writes multi-line content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "multiline.txt")
+      const lines = ["Line 1", "Line 2", "Line 3", ""].join("\n")
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content: lines,
+            },
+            ctx,
+          )
+
+          const content = await fs.readFile(filepath, "utf-8")
+          expect(content).toBe(lines)
+        },
+      })
+    })
+
+    test("handles different line endings", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "crlf.txt")
+      const content = "Line 1\r\nLine 2\r\nLine 3"
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await write.execute(
+            {
+              filePath: filepath,
+              content,
+            },
+            ctx,
+          )
+
+          const buf = await fs.readFile(filepath)
+          expect(buf.toString()).toBe(content)
+        },
+      })
+    })
+  })
+
+  describe("error handling", () => {
+    test("throws error for paths outside project", async () => {
+      await using tmp = await tmpdir()
+      const outsidePath = "/etc/passwd"
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          await expect(
+            write.execute(
+              {
+                filePath: outsidePath,
+                content: "test",
+              },
+              ctx,
+            ),
+          ).rejects.toThrow()
+        },
+      })
+    })
+  })
+
+  describe("title generation", () => {
+    test("returns relative path as title", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "src", "components", "Button.tsx")
+      await fs.mkdir(path.dirname(filepath), { recursive: true })
+
+      await Instance.provide({
+        directory: tmp.path,
+        fn: async () => {
+          const write = await WriteTool.init()
+          const result = await write.execute(
+            {
+              filePath: filepath,
+              content: "export const Button = () => {}",
+            },
+            ctx,
+          )
+
+          expect(result.title).toEndWith(path.join("src", "components", "Button.tsx"))
+        },
+      })
+    })
+  })
+})

packages/opencode/test/util/filesystem.test.ts

@@ -1,39 +1,409 @@
-import { describe, expect, test } from "bun:test"
-import os from "node:os"
-import path from "node:path"
-import { mkdtemp, mkdir, rm } from "node:fs/promises"
+import { describe, test, expect } from "bun:test"
+import path from "path"
+import fs from "fs/promises"
 import { Filesystem } from "../../src/util/filesystem"
+import { tmpdir } from "../fixture/fixture"
 
-describe("util.filesystem", () => {
-  test("exists() is true for files and directories", async () => {
-    const tmp = await mkdtemp(path.join(os.tmpdir(), "opencode-filesystem-"))
-    const dir = path.join(tmp, "dir")
-    const file = path.join(tmp, "file.txt")
-    const missing = path.join(tmp, "missing")
+describe("filesystem", () => {
+  describe("exists()", () => {
+    test("returns true for existing file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
 
-    await mkdir(dir, { recursive: true })
-    await Bun.write(file, "hello")
+      expect(await Filesystem.exists(filepath)).toBe(true)
+    })
 
-    const cases = await Promise.all([Filesystem.exists(dir), Filesystem.exists(file), Filesystem.exists(missing)])
+    test("returns false for non-existent file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "does-not-exist.txt")
 
-    expect(cases).toEqual([true, true, false])
+      expect(await Filesystem.exists(filepath)).toBe(false)
+    })
 
-    await rm(tmp, { recursive: true, force: true })
+    test("returns true for existing directory", async () => {
+      await using tmp = await tmpdir()
+      const dirpath = path.join(tmp.path, "subdir")
+      await fs.mkdir(dirpath)
+
+      expect(await Filesystem.exists(dirpath)).toBe(true)
+    })
   })
 
-  test("isDir() is true only for directories", async () => {
-    const tmp = await mkdtemp(path.join(os.tmpdir(), "opencode-filesystem-"))
-    const dir = path.join(tmp, "dir")
-    const file = path.join(tmp, "file.txt")
-    const missing = path.join(tmp, "missing")
+  describe("isDir()", () => {
+    test("returns true for directory", async () => {
+      await using tmp = await tmpdir()
+      const dirpath = path.join(tmp.path, "testdir")
+      await fs.mkdir(dirpath)
 
-    await mkdir(dir, { recursive: true })
-    await Bun.write(file, "hello")
+      expect(await Filesystem.isDir(dirpath)).toBe(true)
+    })
 
-    const cases = await Promise.all([Filesystem.isDir(dir), Filesystem.isDir(file), Filesystem.isDir(missing)])
+    test("returns false for file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      await fs.writeFile(filepath, "content", "utf-8")
 
-    expect(cases).toEqual([true, false, false])
+      expect(await Filesystem.isDir(filepath)).toBe(false)
+    })
 
-    await rm(tmp, { recursive: true, force: true })
+    test("returns false for non-existent path", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "does-not-exist")
+
+      expect(await Filesystem.isDir(filepath)).toBe(false)
+    })
+  })
+
+  describe("size()", () => {
+    test("returns file size", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      const content = "Hello, World!"
+      await fs.writeFile(filepath, content, "utf-8")
+
+      expect(await Filesystem.size(filepath)).toBe(content.length)
+    })
+
+    test("returns 0 for non-existent file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "does-not-exist.txt")
+
+      expect(await Filesystem.size(filepath)).toBe(0)
+    })
+
+    test("returns directory size", async () => {
+      await using tmp = await tmpdir()
+      const dirpath = path.join(tmp.path, "testdir")
+      await fs.mkdir(dirpath)
+
+      // Directories have size on some systems
+      const size = await Filesystem.size(dirpath)
+      expect(typeof size).toBe("number")
+    })
+  })
+
+  describe("readText()", () => {
+    test("reads file content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      const content = "Hello, World!"
+      await fs.writeFile(filepath, content, "utf-8")
+
+      expect(await Filesystem.readText(filepath)).toBe(content)
+    })
+
+    test("throws for non-existent file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "does-not-exist.txt")
+
+      await expect(Filesystem.readText(filepath)).rejects.toThrow()
+    })
+
+    test("reads UTF-8 content correctly", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "unicode.txt")
+      const content = "Hello 世界 🌍"
+      await fs.writeFile(filepath, content, "utf-8")
+
+      expect(await Filesystem.readText(filepath)).toBe(content)
+    })
+  })
+
+  describe("readJson()", () => {
+    test("reads and parses JSON", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.json")
+      const data = { key: "value", nested: { array: [1, 2, 3] } }
+      await fs.writeFile(filepath, JSON.stringify(data), "utf-8")
+
+      const result: typeof data = await Filesystem.readJson(filepath)
+      expect(result).toEqual(data)
+    })
+
+    test("throws for invalid JSON", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "invalid.json")
+      await fs.writeFile(filepath, "{ invalid json", "utf-8")
+
+      await expect(Filesystem.readJson(filepath)).rejects.toThrow()
+    })
+
+    test("throws for non-existent file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "does-not-exist.json")
+
+      await expect(Filesystem.readJson(filepath)).rejects.toThrow()
+    })
+
+    test("returns typed data", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "typed.json")
+      interface Config {
+        name: string
+        version: number
+      }
+      const data: Config = { name: "test", version: 1 }
+      await fs.writeFile(filepath, JSON.stringify(data), "utf-8")
+
+      const result = await Filesystem.readJson<Config>(filepath)
+      expect(result.name).toBe("test")
+      expect(result.version).toBe(1)
+    })
+  })
+
+  describe("readBytes()", () => {
+    test("reads file as buffer", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      const content = "Hello, World!"
+      await fs.writeFile(filepath, content, "utf-8")
+
+      const buffer = await Filesystem.readBytes(filepath)
+      expect(buffer).toBeInstanceOf(Buffer)
+      expect(buffer.toString("utf-8")).toBe(content)
+    })
+
+    test("throws for non-existent file", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "does-not-exist.bin")
+
+      await expect(Filesystem.readBytes(filepath)).rejects.toThrow()
+    })
+  })
+
+  describe("write()", () => {
+    test("writes text content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.txt")
+      const content = "Hello, World!"
+
+      await Filesystem.write(filepath, content)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes buffer content", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "test.bin")
+      const content = Buffer.from([0x00, 0x01, 0x02, 0x03])
+
+      await Filesystem.write(filepath, content)
+
+      const read = await fs.readFile(filepath)
+      expect(read).toEqual(content)
+    })
+
+    test("writes with permissions", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "protected.txt")
+      const content = "secret"
+
+      await Filesystem.write(filepath, content, 0o600)
+
+      const stats = await fs.stat(filepath)
+      // Check permissions on Unix
+      if (process.platform !== "win32") {
+        expect(stats.mode & 0o777).toBe(0o600)
+      }
+    })
+
+    test("creates parent directories", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "nested", "deep", "file.txt")
+      const content = "nested content"
+
+      await Filesystem.write(filepath, content)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+  })
+
+  describe("writeJson()", () => {
+    test("writes JSON data", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "data.json")
+      const data = { key: "value", number: 42 }
+
+      await Filesystem.writeJson(filepath, data)
+
+      const content = await fs.readFile(filepath, "utf-8")
+      expect(JSON.parse(content)).toEqual(data)
+    })
+
+    test("writes formatted JSON", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "pretty.json")
+      const data = { key: "value" }
+
+      await Filesystem.writeJson(filepath, data)
+
+      const content = await fs.readFile(filepath, "utf-8")
+      expect(content).toContain("\n")
+      expect(content).toContain("  ")
+    })
+
+    test("writes with permissions", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "config.json")
+      const data = { secret: "data" }
+
+      await Filesystem.writeJson(filepath, data, 0o600)
+
+      const stats = await fs.stat(filepath)
+      if (process.platform !== "win32") {
+        expect(stats.mode & 0o777).toBe(0o600)
+      }
+    })
+  })
+
+  describe("mimeType()", () => {
+    test("returns correct MIME type for JSON", () => {
+      expect(Filesystem.mimeType("test.json")).toContain("application/json")
+    })
+
+    test("returns correct MIME type for JavaScript", () => {
+      expect(Filesystem.mimeType("test.js")).toContain("javascript")
+    })
+
+    test("returns MIME type for TypeScript (or video/mp2t due to extension conflict)", () => {
+      const mime = Filesystem.mimeType("test.ts")
+      // .ts is ambiguous: TypeScript vs MPEG-2 TS video
+      expect(mime === "video/mp2t" || mime === "application/typescript" || mime === "text/typescript").toBe(true)
+    })
+
+    test("returns correct MIME type for images", () => {
+      expect(Filesystem.mimeType("test.png")).toContain("image/png")
+      expect(Filesystem.mimeType("test.jpg")).toContain("image/jpeg")
+    })
+
+    test("returns default for unknown extension", () => {
+      expect(Filesystem.mimeType("test.unknown")).toBe("application/octet-stream")
+    })
+
+    test("handles files without extension", () => {
+      expect(Filesystem.mimeType("Makefile")).toBe("application/octet-stream")
+    })
+  })
+
+  describe("writeStream()", () => {
+    test("writes from Web ReadableStream", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "streamed.txt")
+      const content = "Hello from stream!"
+      const encoder = new TextEncoder()
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(encoder.encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes from Node.js Readable stream", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "node-streamed.txt")
+      const content = "Hello from Node stream!"
+      const { Readable } = await import("stream")
+      const stream = Readable.from([content])
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes binary data from Web ReadableStream", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "binary.dat")
+      const binaryData = new Uint8Array([0x00, 0x01, 0x02, 0x03, 0xff])
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(binaryData)
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      const read = await fs.readFile(filepath)
+      expect(Buffer.from(read)).toEqual(Buffer.from(binaryData))
+    })
+
+    test("writes large content in chunks", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "large.txt")
+      const chunks = ["chunk1", "chunk2", "chunk3", "chunk4", "chunk5"]
+      const stream = new ReadableStream({
+        start(controller) {
+          for (const chunk of chunks) {
+            controller.enqueue(new TextEncoder().encode(chunk))
+          }
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(chunks.join(""))
+    })
+
+    test("creates parent directories", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "nested", "deep", "streamed.txt")
+      const content = "nested stream content"
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes with permissions", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "protected-stream.txt")
+      const content = "secret stream content"
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream, 0o600)
+
+      const stats = await fs.stat(filepath)
+      if (process.platform !== "win32") {
+        expect(stats.mode & 0o777).toBe(0o600)
+      }
+    })
+
+    test("writes executable with permissions", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "script.sh")
+      const content = "#!/bin/bash\necho hello"
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream, 0o755)
+
+      const stats = await fs.stat(filepath)
+      if (process.platform !== "win32") {
+        expect(stats.mode & 0o777).toBe(0o755)
+      }
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
   })
 })

packages/opencode/test/util/glob.test.ts

@@ -0,0 +1,164 @@
+import { describe, test, expect } from "bun:test"
+import path from "path"
+import fs from "fs/promises"
+import { Glob } from "../../src/util/glob"
+import { tmpdir } from "../fixture/fixture"
+
+describe("Glob", () => {
+  describe("scan()", () => {
+    test("finds files matching pattern", async () => {
+      await using tmp = await tmpdir()
+      await fs.writeFile(path.join(tmp.path, "a.txt"), "", "utf-8")
+      await fs.writeFile(path.join(tmp.path, "b.txt"), "", "utf-8")
+      await fs.writeFile(path.join(tmp.path, "c.md"), "", "utf-8")
+
+      const results = await Glob.scan("*.txt", { cwd: tmp.path })
+
+      expect(results.sort()).toEqual(["a.txt", "b.txt"])
+    })
+
+    test("returns absolute paths when absolute option is true", async () => {
+      await using tmp = await tmpdir()
+      await fs.writeFile(path.join(tmp.path, "file.txt"), "", "utf-8")
+
+      const results = await Glob.scan("*.txt", { cwd: tmp.path, absolute: true })
+
+      expect(results[0]).toBe(path.join(tmp.path, "file.txt"))
+    })
+
+    test("excludes directories by default", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "subdir"))
+      await fs.writeFile(path.join(tmp.path, "file.txt"), "", "utf-8")
+
+      const results = await Glob.scan("*", { cwd: tmp.path })
+
+      expect(results).toEqual(["file.txt"])
+    })
+
+    test("excludes directories when include is 'file'", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "subdir"))
+      await fs.writeFile(path.join(tmp.path, "file.txt"), "", "utf-8")
+
+      const results = await Glob.scan("*", { cwd: tmp.path, include: "file" })
+
+      expect(results).toEqual(["file.txt"])
+    })
+
+    test("includes directories when include is 'all'", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "subdir"))
+      await fs.writeFile(path.join(tmp.path, "file.txt"), "", "utf-8")
+
+      const results = await Glob.scan("*", { cwd: tmp.path, include: "all" })
+
+      expect(results.sort()).toEqual(["file.txt", "subdir"])
+    })
+
+    test("handles nested patterns", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "nested"), { recursive: true })
+      await fs.writeFile(path.join(tmp.path, "nested", "deep.txt"), "", "utf-8")
+
+      const results = await Glob.scan("**/*.txt", { cwd: tmp.path })
+
+      expect(results).toEqual(["nested/deep.txt"])
+    })
+
+    test("returns empty array for no matches", async () => {
+      await using tmp = await tmpdir()
+
+      const results = await Glob.scan("*.nonexistent", { cwd: tmp.path })
+
+      expect(results).toEqual([])
+    })
+
+    test("does not follow symlinks by default", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "realdir"))
+      await fs.writeFile(path.join(tmp.path, "realdir", "file.txt"), "", "utf-8")
+      await fs.symlink(path.join(tmp.path, "realdir"), path.join(tmp.path, "linkdir"))
+
+      const results = await Glob.scan("**/*.txt", { cwd: tmp.path })
+
+      expect(results).toEqual(["realdir/file.txt"])
+    })
+
+    test("follows symlinks when symlink option is true", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "realdir"))
+      await fs.writeFile(path.join(tmp.path, "realdir", "file.txt"), "", "utf-8")
+      await fs.symlink(path.join(tmp.path, "realdir"), path.join(tmp.path, "linkdir"))
+
+      const results = await Glob.scan("**/*.txt", { cwd: tmp.path, symlink: true })
+
+      expect(results.sort()).toEqual(["linkdir/file.txt", "realdir/file.txt"])
+    })
+
+    test("includes dotfiles when dot option is true", async () => {
+      await using tmp = await tmpdir()
+      await fs.writeFile(path.join(tmp.path, ".hidden"), "", "utf-8")
+      await fs.writeFile(path.join(tmp.path, "visible"), "", "utf-8")
+
+      const results = await Glob.scan("*", { cwd: tmp.path, dot: true })
+
+      expect(results.sort()).toEqual([".hidden", "visible"])
+    })
+
+    test("excludes dotfiles when dot option is false", async () => {
+      await using tmp = await tmpdir()
+      await fs.writeFile(path.join(tmp.path, ".hidden"), "", "utf-8")
+      await fs.writeFile(path.join(tmp.path, "visible"), "", "utf-8")
+
+      const results = await Glob.scan("*", { cwd: tmp.path, dot: false })
+
+      expect(results).toEqual(["visible"])
+    })
+  })
+
+  describe("scanSync()", () => {
+    test("finds files matching pattern synchronously", async () => {
+      await using tmp = await tmpdir()
+      await fs.writeFile(path.join(tmp.path, "a.txt"), "", "utf-8")
+      await fs.writeFile(path.join(tmp.path, "b.txt"), "", "utf-8")
+
+      const results = Glob.scanSync("*.txt", { cwd: tmp.path })
+
+      expect(results.sort()).toEqual(["a.txt", "b.txt"])
+    })
+
+    test("respects options", async () => {
+      await using tmp = await tmpdir()
+      await fs.mkdir(path.join(tmp.path, "subdir"))
+      await fs.writeFile(path.join(tmp.path, "file.txt"), "", "utf-8")
+
+      const results = Glob.scanSync("*", { cwd: tmp.path, include: "all" })
+
+      expect(results.sort()).toEqual(["file.txt", "subdir"])
+    })
+  })
+
+  describe("match()", () => {
+    test("matches simple patterns", () => {
+      expect(Glob.match("*.txt", "file.txt")).toBe(true)
+      expect(Glob.match("*.txt", "file.js")).toBe(false)
+    })
+
+    test("matches directory patterns", () => {
+      expect(Glob.match("**/*.js", "src/index.js")).toBe(true)
+      expect(Glob.match("**/*.js", "src/index.ts")).toBe(false)
+    })
+
+    test("matches dot files", () => {
+      expect(Glob.match(".*", ".gitignore")).toBe(true)
+      expect(Glob.match("**/*.md", ".github/README.md")).toBe(true)
+    })
+
+    test("matches brace expansion", () => {
+      expect(Glob.match("*.{js,ts}", "file.js")).toBe(true)
+      expect(Glob.match("*.{js,ts}", "file.ts")).toBe(true)
+      expect(Glob.match("*.{js,ts}", "file.py")).toBe(false)
+    })
+  })
+})