fix(windows): reap orphaned MCP processes when their parent exits

CHANGELOG.md

@@ -21,6 +21,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ### Fixes
 
+- On Windows, CodeGraph's background processes no longer pile up without bound and saturate CPU over a long session. When the editor or agent that launched CodeGraph exited, its helper process couldn't tell its parent had gone — Windows reports process lineage differently than macOS and Linux — so the helper kept running, the shared background server never saw the client disconnect, and its idle timer never fired to shut it down. CodeGraph now detects parent-process exit directly on Windows, so helpers and the idle background server wind down promptly, the same as they already did on macOS and Linux. (#692, #576, #680)
 - React Native native→JS events now connect through the common `sendEvent(context, "X", body)` wrapper. Many libraries (react-native-device-info and others) wrap the event emitter behind a helper whose `.emit(eventName, …)` takes a *variable*, so the matcher — which looked for `.emit("literal", …)` — missed it; the literal event name actually lives in the wrapper call. Now a native method that fires `sendEvent(…, "batteryLevelChanged", …)` links to the JS `addListener('batteryLevelChanged', …)` handler, so editing the native emitter surfaces the JS subscriber. (React Native)
 - React Native / Expo cross-language bridges are more complete and more precise. An Expo Module method declared with a generic type — Android's `AsyncFunction<Float>("getBatteryLevelAsync")` — is now indexed (the `<Float>` used to defeat the matcher, so every Android Expo method was dropped and a JS call resolved only to the iOS Swift impl). The iOS and Android implementations of the same JS-visible method — both Expo Modules and classic NativeModules (`@ReactMethod` on Android, the matching method on iOS) — are now linked to each other, so a JS call that resolves to one platform still reaches the other and editing either platform's native code surfaces the JS caller. And a `Type.member` static read in native code (e.g. Android's `BatteryManager.EXTRA_LEVEL`) no longer falsely links to a coincidentally same-named class in another language (a web `BatteryManager`) — type references stay within a language family, while genuine cross-language bridges (config→code, JS↔native calls) are unaffected. (React Native, Expo)
 - A TypeScript/JavaScript reference or import no longer gets mis-linked to a same-named class in a native language. In a React Native / Expo repo that has both a TypeScript `TestRunner` type and a Kotlin `TestRunner` class, a TS reference to `TestRunner` — or an `import React` sitting next to a Swift `React` — used to resolve onto the native symbol (the component resolver matched any same-named class regardless of language, and import statements weren't language-checked at all). References and imports now stay within their language family, so they land on the right symbol while genuine cross-language bridges (JS↔native calls, config→code) are untouched. A C/C++ `#include "Foo.h"` likewise no longer resolves to a same-named header from another platform (an iOS Objective-C `Foo.h`). (React Native, Expo, TypeScript, C/C++)

__tests__/ppid-watchdog.test.ts

@@ -0,0 +1,138 @@
+/**
+ * Unit coverage for the PPID-watchdog decision logic (#277, #692).
+ *
+ * The live watchdog timers in `proxy.ts` / `index.ts` are integration-tested on
+ * POSIX in `mcp-ppid-watchdog.test.ts`, but that test is skipped on Windows
+ * (`process.kill(pid, 'SIGKILL')` and reparenting are POSIX-specific). That gap
+ * is exactly how the Windows leak (#692) shipped: on Windows `process.ppid`
+ * never changes when the parent dies, so the old change-only check could never
+ * fire. These pure-function tests exercise the Windows branch on any OS by
+ * stubbing `isAlive` and `platform`.
+ */
+import { describe, it, expect } from 'vitest';
+import { supervisionLostReason } from '../src/mcp/ppid-watchdog';
+
+const alive = () => true;
+const dead = () => false;
+/** Alive for everyone except the listed pids. */
+const deadOnly = (...pids: number[]) => (pid: number) => !pids.includes(pid);
+
+describe('supervisionLostReason', () => {
+  describe('POSIX (parent death reparents → ppid changes)', () => {
+    it('returns null while the parent is unchanged', () => {
+      expect(
+        supervisionLostReason({
+          originalPpid: 100,
+          currentPpid: 100,
+          hostPpid: null,
+          isAlive: alive,
+          platform: 'linux',
+        }),
+      ).toBeNull();
+    });
+
+    it('detects a reparent (ppid divergence) as the death signal', () => {
+      const reason = supervisionLostReason({
+        originalPpid: 100,
+        currentPpid: 1, // reparented to init
+        hostPpid: null,
+        isAlive: alive,
+        platform: 'linux',
+      });
+      expect(reason).toBe('ppid 100 -> 1');
+    });
+
+    it('does NOT use liveness on POSIX — a dead original ppid is not orphaning', () => {
+      // A double-forked grandparent can die while we stay correctly parented.
+      // POSIX must rely on the change-check only, or it would false-positive.
+      expect(
+        supervisionLostReason({
+          originalPpid: 100,
+          currentPpid: 100,
+          hostPpid: null,
+          isAlive: dead,
+          platform: 'linux',
+        }),
+      ).toBeNull();
+    });
+  });
+
+  describe('Windows (ppid is stable across parent death → poll liveness)', () => {
+    it('returns null while the original parent is still alive', () => {
+      expect(
+        supervisionLostReason({
+          originalPpid: 100,
+          currentPpid: 100,
+          hostPpid: null,
+          isAlive: alive,
+          platform: 'win32',
+        }),
+      ).toBeNull();
+    });
+
+    it('detects parent death by liveness even though ppid is unchanged (the #692 fix)', () => {
+      const reason = supervisionLostReason({
+        originalPpid: 100,
+        currentPpid: 100, // Windows never reparents
+        hostPpid: null,
+        isAlive: deadOnly(100),
+        platform: 'win32',
+      });
+      expect(reason).toBe('parent pid 100 exited');
+    });
+
+    it('ignores pid 0/1 — never a real Windows parent, must not trigger shutdown', () => {
+      for (const ppid of [0, 1]) {
+        expect(
+          supervisionLostReason({
+            originalPpid: ppid,
+            currentPpid: ppid,
+            hostPpid: null,
+            isAlive: dead,
+            platform: 'win32',
+          }),
+        ).toBeNull();
+      }
+    });
+  });
+
+  describe('threaded host pid (reached past an intermediate launcher shim)', () => {
+    it('shuts down when the host pid is gone, on either platform', () => {
+      for (const platform of ['linux', 'win32'] as const) {
+        const reason = supervisionLostReason({
+          originalPpid: 100,
+          currentPpid: 100,
+          hostPpid: 42,
+          isAlive: deadOnly(42), // shim 100 alive, host 42 dead
+          platform,
+        });
+        expect(reason).toBe('host pid 42 exited');
+      }
+    });
+
+    it('stays supervised while the host pid is alive', () => {
+      expect(
+        supervisionLostReason({
+          originalPpid: 100,
+          currentPpid: 100,
+          hostPpid: 42,
+          isAlive: alive,
+          platform: 'linux',
+        }),
+      ).toBeNull();
+    });
+  });
+
+  describe('signal precedence', () => {
+    it('reports the ppid change ahead of a host-gone reason', () => {
+      const reason = supervisionLostReason({
+        originalPpid: 100,
+        currentPpid: 1,
+        hostPpid: 42,
+        isAlive: dead,
+        platform: 'linux',
+      });
+      expect(reason).toBe('ppid 100 -> 1');
+    });
+  });
+});

src/mcp/index.ts

@@ -49,6 +49,7 @@ import {
 } from './daemon';
 import { connectWithHello, runLocalHandshakeProxy } from './proxy';
 import { getDaemonSocketPath } from './daemon-paths';
+import { supervisionLostReason } from './ppid-watchdog';
 import { HOST_PPID_ENV } from '../extraction/wasm-runtime-flags';
 
 /**
@@ -423,13 +424,13 @@ export class MCPServer {
     const pollMs = parsePpidPollMs(process.env.CODEGRAPH_PPID_POLL_MS);
     if (pollMs <= 0) return;
     this.ppidWatchdog = setInterval(() => {
-      const current = process.ppid;
-      const ppidChanged = current !== this.originalPpid;
-      const hostGone = this.hostPpid !== null && !isProcessAlive(this.hostPpid);
-      if (ppidChanged || hostGone) {
-        const reason = ppidChanged
-          ? `ppid ${this.originalPpid} -> ${current}`
-          : `host pid ${this.hostPpid} exited`;
+      const reason = supervisionLostReason({
+        originalPpid: this.originalPpid,
+        currentPpid: process.ppid,
+        hostPpid: this.hostPpid,
+        isAlive: isProcessAlive,
+      });
+      if (reason) {
         process.stderr.write(
           `[CodeGraph MCP] Parent process exited (${reason}); shutting down.\n`
         );

src/mcp/ppid-watchdog.ts

@@ -0,0 +1,63 @@
+/**
+ * Shared decision logic for the PPID watchdog (#277, #692).
+ *
+ * The watchdog's job: notice that the process we depend on — our parent, or the
+ * MCP host reached past an intermediate launcher — has died, so an orphaned
+ * proxy / direct server shuts itself down instead of leaking forever.
+ *
+ * Parent death surfaces differently per OS, and getting this wrong is what
+ * caused the unbounded daemon/proxy leak on Windows (#692, #576):
+ *
+ *   - **POSIX** reparents an orphan to init (pid 1), so `process.ppid` *changes*
+ *     the instant the parent dies. That divergence is the classic #277 signal.
+ *   - **Windows** never reparents: `process.ppid` keeps reporting the original
+ *     (now-dead) parent forever, so the change-check can never fire. There we
+ *     must poll the original parent's *liveness* instead.
+ *
+ * The liveness fallback is deliberately gated to Windows. On POSIX a
+ * double-forked grandparent can legitimately outlive the reparent, so a dead
+ * `originalPpid` is not proof of orphaning there — the change-check is the
+ * correct and sufficient POSIX signal, and using liveness too would risk a
+ * false-positive shutdown.
+ */
+export interface SupervisionState {
+  /** `process.ppid` captured at startup. */
+  originalPpid: number;
+  /** `process.ppid` right now. */
+  currentPpid: number;
+  /**
+   * The MCP host pid threaded past an intermediate launcher
+   * (`CODEGRAPH_HOST_PPID`), or null when unknown — e.g. the standalone bundle,
+   * which pre-bakes `--liftoff-only` and so never runs the relaunch that sets it.
+   */
+  hostPpid: number | null;
+  /** Liveness probe — `process.kill(pid, 0)` in production, stubbed in tests. */
+  isAlive: (pid: number) => boolean;
+  /** Defaults to `process.platform`. */
+  platform?: NodeJS.Platform;
+}
+
+/**
+ * Returns a human-readable reason string when the process has lost its
+ * supervisor and should shut down, or null while it is still supervised.
+ */
+export function supervisionLostReason(state: SupervisionState): string | null {
+  const { originalPpid, currentPpid, hostPpid, isAlive } = state;
+  const platform = state.platform ?? process.platform;
+
+  // POSIX: the parent dying reparents us, so ppid diverges. (Never on Windows.)
+  if (currentPpid !== originalPpid) {
+    return `ppid ${originalPpid} -> ${currentPpid}`;
+  }
+  // Windows: ppid is stable across parent death, so detect it by liveness.
+  // Skip pid 0/1 — "unknown" and init are never a real Windows parent, and a
+  // bogus liveness probe there must not trigger a shutdown.
+  if (platform === 'win32' && originalPpid > 1 && !isAlive(originalPpid)) {
+    return `parent pid ${originalPpid} exited`;
+  }
+  // Either platform: the host pid threaded past a launcher shim is gone.
+  if (hostPpid !== null && !isAlive(hostPpid)) {
+    return `host pid ${hostPpid} exited`;
+  }
+  return null;
+}

src/mcp/proxy.ts

@@ -22,6 +22,7 @@ import * as fs from 'fs';
 import * as net from 'net';
 import { HOST_PPID_ENV } from '../extraction/wasm-runtime-flags';
 import { DaemonHello, MAX_HELLO_LINE_BYTES } from './daemon';
+import { supervisionLostReason } from './ppid-watchdog';
 import { CodeGraphPackageVersion } from './version';
 import { SERVER_INFO, PROTOCOL_VERSION } from './session';
 import { SERVER_INSTRUCTIONS } from './server-instructions';
@@ -292,8 +293,14 @@ function startPpidWatchdogNoSocket(onDeath: () => void): void {
   const originalPpid = process.ppid;
   const hostPpid = parseHostPpid(process.env[HOST_PPID_ENV]);
   const timer = setInterval(() => {
-    if (process.ppid !== originalPpid || (hostPpid !== null && !isProcessAliveLocal(hostPpid))) {
-      process.stderr.write('[CodeGraph MCP] Parent process exited; shutting down.\n');
+    const reason = supervisionLostReason({
+      originalPpid,
+      currentPpid: process.ppid,
+      hostPpid,
+      isAlive: isProcessAliveLocal,
+    });
+    if (reason) {
+      process.stderr.write(`[CodeGraph MCP] Parent process exited (${reason}); shutting down.\n`);
       onDeath();
     }
   }, pollMs);
@@ -408,13 +415,13 @@ function startPpidWatchdog(socket: net.Socket): void {
   const originalPpid = process.ppid;
   const hostPpid = parseHostPpid(process.env[HOST_PPID_ENV]);
   const timer = setInterval(() => {
-    const current = process.ppid;
-    const ppidChanged = current !== originalPpid;
-    const hostGone = hostPpid !== null && !isProcessAliveLocal(hostPpid);
-    if (ppidChanged || hostGone) {
-      const reason = ppidChanged
-        ? `ppid ${originalPpid} -> ${current}`
-        : `host pid ${hostPpid} exited`;
+    const reason = supervisionLostReason({
+      originalPpid,
+      currentPpid: process.ppid,
+      hostPpid,
+      isAlive: isProcessAliveLocal,
+    });
+    if (reason) {
       process.stderr.write(`[CodeGraph MCP] Parent process exited (${reason}); shutting down.\n`);
       try { socket.destroy(); } catch { /* ignore */ }
       process.exit(0);