Merge pull request #13466 from Kilo-Org/investigate-connection-failures-root-cause

fix(vscode): handle fragmented CLI startup output

.changeset/fix-vscode-server-startup-output.md

@@ -0,0 +1,5 @@
+---
+"kilo-code": patch
+---
+
+Prevent intermittent server connection failures during VS Code startup.

packages/kilo-vscode/src/services/cli-backend/server-manager.ts

@@ -6,7 +6,7 @@ import * as path from "path"
 import * as vscode from "vscode"
 import { resolveLocalBwrapEnv, resolveTreeSitterEnv } from "./cli-resources"
 import { t } from "./i18n"
-import { parseServerPort } from "./server-utils"
+import { scanServerPort } from "./server-utils"
 
 export interface ServerInstance {
   port: number
@@ -15,6 +15,7 @@ export interface ServerInstance {
 }
 
 const STARTUP_TIMEOUT_SECONDS = 30
+const STARTUP_OUTPUT_LIMIT = 1024
 
 type WorkspaceFolderLike = { uri: { fsPath: string } }
 type ServerExitListener = (code: number | null, signal: NodeJS.Signals | null) => void
@@ -162,13 +163,16 @@ export class ServerManager {
       console.log("[Kilo New] ServerManager: 📦 Process spawned with PID:", serverProcess.pid)
 
       let resolved = false
+      let output = ""
       const stderrLines: string[] = []
 
       serverProcess.stdout?.on("data", (data: Buffer) => {
-        const output = data.toString()
-        console.log("[Kilo New] ServerManager: 📥 CLI Server stdout:", output)
+        const chunk = data.toString()
+        console.log("[Kilo New] ServerManager: 📥 CLI Server stdout:", chunk)
 
-        const port = parseServerPort(output)
+        const state = scanServerPort(output, chunk, STARTUP_OUTPUT_LIMIT)
+        output = state.output
+        const port = state.port
         if (port !== null && !resolved) {
           resolved = true
           console.log("[Kilo New] ServerManager: 🎯 Port detected:", port)

packages/kilo-vscode/src/services/cli-backend/server-utils.ts

@@ -3,8 +3,15 @@
  * Matches lines like: "kilo server listening on http://127.0.0.1:12345"
  * Returns the port number or null if not found.
  */
-export function parseServerPort(output: string): number | null {
-  const match = output.match(/listening on http:\/\/[\w.]+:(\d+)/)
+export function parseServerPort(output: string, complete = false): number | null {
+  const match = output.match(
+    complete ? /listening on http:\/\/[\w.]+:(\d+)\r?\n/ : /listening on http:\/\/[\w.]+:(\d+)/,
+  )
   if (!match) return null
   return parseInt(match[1]!, 10)
 }
+
+export function scanServerPort(output: string, chunk: string, limit: number) {
+  const text = `${output}${chunk}`
+  return { output: text.slice(-limit), port: parseServerPort(text, true) }
+}

packages/kilo-vscode/tests/unit/server-manager-utils.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from "bun:test"
-import { parseServerPort } from "../../src/services/cli-backend/server-utils"
+import { parseServerPort, scanServerPort } from "../../src/services/cli-backend/server-utils"
 import {
   resolveServerCwd,
   resolveIndexingEnv,
@@ -61,6 +61,51 @@ describe("parseServerPort", () => {
     const output = "listening on http://127.0.0.1:3000 and http://127.0.0.1:4000"
     expect(parseServerPort(output)).toBe(3000)
   })
+
+  it("waits for the complete startup line before resolving a split port", () => {
+    const first = "kilo server listening on http://127.0.0.1:43"
+
+    expect(parseServerPort(first, true)).toBeNull()
+    expect(parseServerPort(`${first}123\n`, true)).toBe(43123)
+  })
+
+  it("detects a startup announcement split across stdout chunks", () => {
+    const first = "kilo server listening on http://127.0."
+    const second = "0.1:43123\n"
+
+    expect(parseServerPort(first, true)).toBeNull()
+    expect(parseServerPort(`${first}${second}`, true)).toBe(43123)
+  })
+
+  it("accepts complete Windows startup lines", () => {
+    expect(parseServerPort("kilo server listening on http://127.0.0.1:43123\r\n", true)).toBe(43123)
+  })
+})
+
+describe("scanServerPort", () => {
+  it("detects startup announcements split across stdout chunks", () => {
+    const first = scanServerPort("", "kilo server listening on http://127.0.", 1024)
+    const second = scanServerPort(first.output, "0.1:43123\n", 1024)
+
+    expect(first.port).toBeNull()
+    expect(second.port).toBe(43123)
+  })
+
+  it("waits for split port digits before resolving startup", () => {
+    const first = scanServerPort("", "kilo server listening on http://127.0.0.1:43", 1024)
+    const second = scanServerPort(first.output, "123\n", 1024)
+
+    expect(first.port).toBeNull()
+    expect(second.port).toBe(43123)
+  })
+
+  it("preserves startup announcements followed by oversized stdout chunks", () => {
+    const chunk = `kilo server listening on http://127.0.0.1:43123\n${"x".repeat(1024)}`
+    const state = scanServerPort("", chunk, 1024)
+
+    expect(state.port).toBe(43123)
+    expect(state.output).toHaveLength(1024)
+  })
 })
 
 describe("cli tree-sitter resources", () => {