diff --git a/packages/kilo-vscode/src/KiloProvider.ts b/packages/kilo-vscode/src/KiloProvider.ts
index 04ddf9551c..cb7e0a0b81 100644
--- a/packages/kilo-vscode/src/KiloProvider.ts
+++ b/packages/kilo-vscode/src/KiloProvider.ts
@@ -2471,7 +2471,7 @@ export class KiloProvider implements vscode.WebviewViewProvider, TelemetryProper
           const uri = tab.input.uri
           if (uri.scheme === "file") {
             const rel = path.relative(dir, uri.fsPath)
-            if (!rel.startsWith("..") && controller.validateAccess(uri.fsPath)) {
+            if (!rel.startsWith("..") && !path.isAbsolute(rel) && controller.validateAccess(uri.fsPath)) {
               result.add(rel.replaceAll("\\", "/"))
             }
           }
@@ -2505,7 +2505,7 @@ export class KiloProvider implements vscode.WebviewViewProvider, TelemetryProper
         return undefined
       }
       const relative = path.relative(workspaceDir, fsPath)
-      if (relative.startsWith("..")) {
+      if (relative.startsWith("..") || path.isAbsolute(relative)) {
         return undefined
       }
       return relative
diff --git a/packages/kilo-vscode/src/services/autocomplete/shims/FileIgnoreController.ts b/packages/kilo-vscode/src/services/autocomplete/shims/FileIgnoreController.ts
index c314aacaff..1b8c639cb4 100644
--- a/packages/kilo-vscode/src/services/autocomplete/shims/FileIgnoreController.ts
+++ b/packages/kilo-vscode/src/services/autocomplete/shims/FileIgnoreController.ts
@@ -10,6 +10,11 @@ const GITIGNORE = ".gitignore"
  */
 const SENSITIVE_PATTERNS = [".env", ".env.*"]
 
+// Matches Windows drive-letter absolute paths (e.g. "C:/" or "c:\").
+// path.isAbsolute() on POSIX does not recognise these, so we check explicitly
+// to avoid passing them to the `ignore` package which throws a RangeError.
+const WINDOWS_DRIVE = /^[a-zA-Z]:[/\\]/
+
 function toPosix(filePath: string): string {
   return filePath.replace(/\\/g, "/")
 }
@@ -87,7 +92,7 @@ export class FileIgnoreController {
     }
 
     const relative = path.relative(this.workspacePath, resolved)
-    if (!relative || relative.startsWith("..")) {
+    if (!relative || relative.startsWith("..") || path.isAbsolute(relative) || WINDOWS_DRIVE.test(relative)) {
       return null
     }
 
diff --git a/packages/kilo-vscode/tests/unit/file-ignore-controller.test.ts b/packages/kilo-vscode/tests/unit/file-ignore-controller.test.ts
index 5b4e313121..e590f92b36 100644
--- a/packages/kilo-vscode/tests/unit/file-ignore-controller.test.ts
+++ b/packages/kilo-vscode/tests/unit/file-ignore-controller.test.ts
@@ -2,8 +2,16 @@ import { afterEach, describe, expect, it } from "bun:test"
 import os from "node:os"
 import path from "node:path"
 import fs from "node:fs/promises"
+import ignore from "ignore"
 import { FileIgnoreController } from "../../src/services/autocomplete/shims/FileIgnoreController"
 
+// Activate Windows drive-letter detection in the `ignore` package.
+// On actual Windows this runs automatically (process.platform === 'win32');
+// here we enable it explicitly so the test reproduces the Windows-only
+// RangeError on any platform.
+const setup = (ignore as any)[Symbol.for("setupWindows")]
+if (typeof setup === "function") setup()
+
 const tempDirs: string[] = []
 
 afterEach(async () => {
@@ -102,6 +110,55 @@ describe("FileIgnoreController", () => {
     })
   })
 
+  describe("Windows cross-drive paths", () => {
+    it("does not throw for a Windows-style absolute path from another drive", async () => {
+      const workspace = await createTempWorkspace()
+      await fs.writeFile(path.join(workspace, ".gitignore"), "node_modules/\n")
+
+      const controller = new FileIgnoreController(workspace)
+      await controller.initialize()
+
+      // Simulates a VS Code tab open on a file from a different Windows drive.
+      // On Windows, path.relative("D:\\project", "C:\\Users\\file") returns
+      // "C:\\Users\\file" (absolute), which the `ignore` package rejects via
+      // RangeError: path should be a `path.relative()`d string.
+      //
+      // On macOS, path.resolve joins "c:/..." relative to the workspace,
+      // producing "c:/Users/..." as the relative portion — still detected as
+      // a Windows drive letter by ignore's setupWindows() regex.
+      const cross =
+        "c:/Users/User/AppData/Roaming/Code/User/globalStorage/kilocode.kilo-code/settings/mcp_settings.json"
+
+      expect(() => controller.validateAccess(cross)).not.toThrow()
+      expect(controller.validateAccess(cross)).toBe(false)
+    })
+
+    it("does not throw for file:// URIs with Windows drive letters", async () => {
+      const workspace = await createTempWorkspace()
+      await fs.writeFile(path.join(workspace, ".gitignore"), "node_modules/\n")
+
+      const controller = new FileIgnoreController(workspace)
+      await controller.initialize()
+
+      const uri =
+        "file:///c:/Users/User/AppData/Roaming/Code/User/globalStorage/kilocode.kilo-code/settings/mcp_settings.json"
+
+      expect(() => controller.validateAccess(uri)).not.toThrow()
+      expect(controller.validateAccess(uri)).toBe(false)
+    })
+
+    it("still allows workspace files after cross-drive check", async () => {
+      const workspace = await createTempWorkspace()
+      await fs.writeFile(path.join(workspace, ".gitignore"), "node_modules/\n")
+
+      const controller = new FileIgnoreController(workspace)
+      await controller.initialize()
+
+      expect(controller.validateAccess(path.join(workspace, "src", "main.ts"))).toBe(true)
+      expect(controller.validateAccess(path.join(workspace, "node_modules", "foo.js"))).toBe(false)
+    })
+  })
+
   describe("when constructed with empty workspace path", () => {
     it("denies all access", async () => {
       const controller = new FileIgnoreController("")
diff --git a/packages/opencode/src/file/index.ts b/packages/opencode/src/file/index.ts
index 01f07c9afa..2c181479be 100644
--- a/packages/opencode/src/file/index.ts
+++ b/packages/opencode/src/file/index.ts
@@ -596,12 +596,15 @@ export namespace File {
       const fullPath = path.join(resolved, entry.name)
       const relativePath = path.relative(Instance.directory, fullPath)
       const type = entry.isDirectory() ? "directory" : "file"
+      // On Windows, path.relative() across drives returns an absolute path;
+      // skip the gitignore check in that case to avoid a RangeError from `ignore`.
+      const canIgnore = !path.isAbsolute(relativePath)
       nodes.push({
         name: entry.name,
         path: relativePath,
         absolute: fullPath,
         type,
-        ignored: ignored(type === "directory" ? relativePath + "/" : relativePath),
+        ignored: canIgnore && ignored(type === "directory" ? relativePath + "/" : relativePath),
       })
     }
     return nodes.sort((a, b) => {