fix(pty): fix race condition in PTY read loop

Add temporary monkey patch to bun-pty _startReadLoop to prevent race condition until upstream PR is merged.

Update echo test to use echo command for simpler testing. Add spawn repeat test.

Author: MBanucu

src/plugin/pty/manager.ts

@@ -5,6 +5,15 @@ import { OutputManager } from './OutputManager.ts'
 import { NotificationManager } from './NotificationManager.ts'
 import { withSession } from './utils.ts'
 
+// Monkey-patch bun-pty to fix race condition in _startReadLoop
+// Temporary workaround until https://github.com/sursaone/bun-pty/pull/37 is merged
+import { Terminal } from 'bun-pty'
+const originalStartReadLoop = (Terminal.prototype as any)._startReadLoop
+;(Terminal.prototype as any)._startReadLoop = async function (...args: any[]) {
+  await new Promise((resolve) => setTimeout(resolve, 0))
+  return originalStartReadLoop.apply(this, args)
+}
+
 let onSessionUpdate: (() => void) | undefined
 
 export function setOnSessionUpdate(callback: () => void) {

test/pty-echo.test.ts

@@ -22,35 +22,33 @@ describe('PTY Echo Behavior', () => {
   it('should echo input characters in interactive bash session', async () => {
     const receivedOutputs: string[] = []
 
-    // Subscribe to raw output events
-    onRawOutput((_sessionId, rawData) => {
-      receivedOutputs.push(rawData)
-    })
+    const promise = new Promise<void>((resolve) => {
+      // Subscribe to raw output events
+      onRawOutput((_sessionId, rawData) => {
+        receivedOutputs.push(rawData)
+        if (receivedOutputs.join('').includes('Hello World')) {
+          resolve()
+        }
+      })
+      setTimeout(resolve, 1000)
+    }).catch((e) => { console.error(e) })
 
     // Spawn interactive bash session
     const session = manager.spawn({
-      command: 'bash',
-      args: ['-i'],
+      command: 'echo',
+      args: ['Hello World'],
       description: 'Echo test session',
       parentSessionId: 'test',
     })
 
-    // Wait for PTY to initialize and show prompt
-    await new Promise((resolve) => setTimeout(resolve, 200))
-
-    // Send test input
-    const success = manager.write(session.id, 'a')
-    expect(success).toBe(true)
-
-    // Wait for echo to be processed
-    await new Promise((resolve) => setTimeout(resolve, 200))
+    await promise
 
     // Clean up
     manager.kill(session.id, true)
 
     // Verify echo occurred
     const allOutput = receivedOutputs.join('')
-    expect(allOutput).toContain('a')
+    expect(allOutput).toContain('Hello World')
 
     // Should have received some output (prompt + echo)
     expect(receivedOutputs.length).toBeGreaterThan(0)

test/spawn-repeat.test.ts

@@ -0,0 +1,72 @@
+import { describe, it, expect, beforeEach, afterEach, } from 'bun:test'
+import { initManager, manager, onRawOutput } from '../src/plugin/pty/manager.ts'
+
+describe('PTY Echo Behavior', () => {
+  const fakeClient = {
+    app: {
+      log: async (_opts: any) => {
+        // Mock logger
+      },
+    },
+  } as any
+
+  beforeEach(() => {
+    initManager(fakeClient)
+  })
+
+  afterEach(() => {
+    // Clean up any sessions
+    manager.clearAllSessions()
+  })
+
+  it("should receive initial data reproducibly", async () => {
+    const start = Date.now();
+    const maxRuntime = 4000;
+    let runnings = 1;
+    while (Date.now() - start < maxRuntime) {
+      console.log(`[TEST] Iteration ${runnings++}`);
+      const { success, stderr } = Bun.spawnSync({
+        cmd: ["bun", "test", "--test-name-pattern", "should receive initial data once"],
+        stdout: "pipe",
+        stderr: "pipe",
+        env: { ...process.env, SYNC_TESTS: "1" },
+      });
+      expect(success, `stderr: ${stderr}`).toBe(true);
+    }
+  });
+
+  it.skipIf(!process.env.SYNC_TESTS)("should receive initial data once", async () => {
+  const receivedOutputs: string[] = []
+
+  const promise = new Promise<void>((resolve) => {
+    // Subscribe to raw output events
+    onRawOutput((_sessionId, rawData) => {
+      receivedOutputs.push(rawData)
+      if (receivedOutputs.join('').includes('Hello World')) {
+        resolve()
+      }
+    })
+    setTimeout(resolve, 1000)
+  }).catch((e) => { console.error(e) })
+
+  // Spawn interactive bash session
+  const session = manager.spawn({
+    command: 'echo',
+    args: ['Hello World'],
+    description: 'Echo test session',
+    parentSessionId: 'test',
+  })
+
+  await promise
+
+  // Clean up
+  manager.kill(session.id, true)
+
+  // Verify echo occurred
+  const allOutput = receivedOutputs.join('')
+  expect(allOutput).toContain('Hello World')
+
+  // Should have received some output (prompt + echo)
+  expect(receivedOutputs.length).toBeGreaterThan(0)
+  });
+})