Merge pull request 'RFC-006 Phase 2: Migrate SenseWorkerPool to WorkerRuntime' (#292) from refactor/rfc-006-worker-runtime into main

packages/daemon/src/__tests__/fixtures/crash-worker.js

@@ -0,0 +1,9 @@
+// Ready then crashes on a timer; still echoes IPC so parent tests can send after respawn
+process.on("message", (msg) => {
+  if (msg && msg.type === "shutdown") {
+    process.exit(0);
+  }
+  process.send({ type: "echo", payload: msg });
+});
+process.send({ type: "ready" });
+setTimeout(() => process.exit(1), 50);

packages/daemon/src/__tests__/fixtures/echo-worker.js

@@ -0,0 +1,9 @@
+// Simple test worker: sends ready, echoes messages, handles shutdown
+process.on("message", (msg) => {
+  if (msg && msg.type === "shutdown") {
+    process.exit(0);
+  }
+  // Echo back with 'echo' type
+  process.send({ type: "echo", payload: msg });
+});
+process.send({ type: "ready" });

packages/daemon/src/__tests__/fixtures/stderr-worker.js

@@ -0,0 +1,9 @@
+// Like echo-worker but writes stderr for tail diagnostics
+console.error("stderr-marker");
+process.on("message", (msg) => {
+  if (msg && msg.type === "shutdown") {
+    process.exit(0);
+  }
+  process.send({ type: "echo", payload: msg });
+});
+process.send({ type: "ready" });

packages/daemon/src/__tests__/kernel-phase6.test.ts

@@ -70,6 +70,14 @@ const { createKernel } = await import("../kernel.js");
 // Helpers
 // ---------------------------------------------------------------------------
 
+/** Sense worker `fork` runs on the next microtask per scheduled `start`. */
+async function flushSenseWorkerForkMicrotasks(kernel: { groups: Set<string> }): Promise<void> {
+  const n = kernel.groups.size;
+  for (let i = 0; i < n; i++) {
+    await Promise.resolve();
+  }
+}
+
 function makeConfig(overrides: Partial<NerveConfig> = {}): NerveConfig {
   return {
     senses: {
@@ -142,6 +150,8 @@ describe("kernel — getHealth", () => {
       },
     });
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
+    await vi.runAllTimersAsync();
 
     const health = kernel.getHealth();
     expect(health.activeSenses).toBe(3);
@@ -171,6 +181,8 @@ describe("kernel — restartGroup", () => {
   it("sends shutdown to old worker and spawns new one", async () => {
     const config = makeConfig();
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
+    await vi.runAllTimersAsync();
 
     expect(mockChildren.length).toBe(1);
     const oldChild = mockChildren[0];
@@ -178,6 +190,7 @@ describe("kernel — restartGroup", () => {
     const restartPromise = kernel.restartGroup("system");
     // The shutdown message triggers exit in the mock
     await restartPromise;
+    await vi.runAllTimersAsync();
 
     // A new child should have been spawned
     expect(mockChildren.length).toBe(2);
@@ -191,6 +204,8 @@ describe("kernel — restartGroup", () => {
   it("restartGroup on unknown group does nothing", async () => {
     const config = makeConfig();
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
+    await vi.runAllTimersAsync();
 
     expect(mockChildren.length).toBe(1);
     await kernel.restartGroup("nonexistent");
@@ -218,6 +233,8 @@ describe("kernel — reloadConfig", () => {
   it("adds new group worker when new sense group appears", async () => {
     const config = makeConfig();
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
+    await vi.runAllTimersAsync();
 
     expect(mockChildren.length).toBe(1); // only system group
     expect(kernel.groups.has("network")).toBe(false);
@@ -249,6 +266,9 @@ describe("kernel — reloadConfig", () => {
       api: { port: null, token: null, host: "127.0.0.1" },
     });
 
+    await Promise.resolve();
+    await vi.runAllTimersAsync();
+
     expect(kernel.groups.has("network")).toBe(true);
     expect(mockChildren.length).toBe(2); // system + network
 
@@ -283,6 +303,8 @@ describe("kernel — reloadConfig", () => {
       api: { port: null, token: null, host: "127.0.0.1" },
     };
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
+    await vi.runAllTimersAsync();
 
     expect(mockChildren.length).toBe(2);
     expect(kernel.groups.has("network")).toBe(true);
@@ -308,6 +330,7 @@ describe("kernel — reloadConfig", () => {
     });
 
     expect(kernel.groups.has("network")).toBe(false);
+    await vi.runAllTimersAsync();
     // Network child should have received shutdown
     expect(networkChild.send).toHaveBeenCalledWith(expect.objectContaining({ type: "shutdown" }));
 
@@ -317,6 +340,8 @@ describe("kernel — reloadConfig", () => {
   it("health reflects updated sense count after reloadConfig", async () => {
     const config = makeConfig();
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
+    await vi.runAllTimersAsync();
 
     expect(kernel.getHealth().activeSenses).toBe(1);
 

packages/daemon/src/__tests__/kernel-trigger-sense.test.ts

@@ -29,6 +29,9 @@ type MockChild = EventEmitter & {
 function makeMockChild(pid = 1): MockChild {
   const child = new EventEmitter() as MockChild;
   child.connected = true;
+  setImmediate(() => {
+    child.emit("message", { type: "ready" });
+  });
   child.send = vi.fn((msg: unknown) => {
     if (
       msg !== null &&
@@ -136,6 +139,7 @@ describe("kernel.triggerSense()", () => {
       logStore: makeMockLogStore() as never,
     });
 
+    await vi.runAllTimersAsync();
     expect(() => kernel.triggerSense("no-such-sense")).toThrow(/Unknown sense/);
 
     await kernel.stop();
@@ -169,6 +173,7 @@ describe("kernel.triggerSense()", () => {
       logStore: makeMockLogStore() as never,
     });
 
+    await vi.runAllTimersAsync();
     // Two groups → two workers
     expect(mockChildren.length).toBe(2);
 
@@ -214,6 +219,7 @@ describe("kernel.triggerSense()", () => {
       logStore: makeMockLogStore() as never,
     });
 
+    await vi.runAllTimersAsync();
     // Both senses share the "system" group → one worker only
     expect(mockChildren.length).toBe(1);
     const worker = mockChildren[0];
@@ -237,6 +243,7 @@ describe("kernel.triggerSense()", () => {
       logStore: makeMockLogStore() as never,
     });
 
+    await new Promise<void>((resolve) => setImmediate(resolve));
     const worker = mockChildren[0];
     worker.connected = false;
 

packages/daemon/src/__tests__/kernel-workflow-integration.test.ts

@@ -102,6 +102,13 @@ function makeLogStore() {
   };
 }
 
+async function flushSenseWorkerForkMicrotasks(kernel: { groups: Set<string> }): Promise<void> {
+  const n = kernel.groups.size;
+  for (let i = 0; i < n; i++) {
+    await Promise.resolve();
+  }
+}
+
 function makeConfig(overrides: Partial<NerveConfig> = {}): NerveConfig {
   return {
     senses: {
@@ -164,6 +171,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Simulate a sense worker sending a signal with workflow launch payload
       // The kernel's handleWorkerMessage processes "signal" type messages
@@ -222,6 +231,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Simulate sense worker returning a signal plus workflow launch
       const workerPool = mockChildren[0];
@@ -275,6 +286,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       const workerPool = mockChildren[0];
       if (workerPool) {
@@ -337,6 +350,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Emit a regular signal (shorthand payload) — should NOT trigger any workflow
       const workerPool = mockChildren[0];
@@ -387,6 +402,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Simulate sense compute returning a signal plus workflow launch
       const workerPool = mockChildren[0];
@@ -440,6 +457,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Reload with a workflow added
       const newConfig: NerveConfig = {
@@ -517,6 +536,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Reload with the workflow removed
       const newConfig: NerveConfig = {
@@ -600,6 +621,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       // Trigger a workflow via sense compute return value
       const workerPool = mockChildren[0];
@@ -664,6 +687,8 @@ describe("kernel + workflowManager integration", () => {
         workerScript: "fake-worker.js",
         logStore,
       });
+      await flushSenseWorkerForkMicrotasks(kernel);
+      await vi.runAllTimersAsync();
 
       const health = kernel.getHealth();
       expect(health).toHaveProperty("activeWorkflows");

packages/daemon/src/__tests__/kernel.test.ts

@@ -16,10 +16,12 @@ type MockChild = EventEmitter & {
   send: ReturnType<typeof vi.fn>;
   kill: ReturnType<typeof vi.fn>;
   pid: number;
+  connected: boolean;
 };
 
 function makeMockChild(pid = 1): MockChild {
   const child = new EventEmitter() as MockChild;
+  child.connected = true;
   setImmediate(() => {
     child.emit("message", { type: "ready" });
   });
@@ -27,7 +29,10 @@ function makeMockChild(pid = 1): MockChild {
     if (msg === null || typeof msg !== "object") return;
     const m = msg as Record<string, unknown>;
     if (m.type === "shutdown") {
-      setImmediate(() => child.emit("exit", 0, null));
+      setImmediate(() => {
+        child.connected = false;
+        child.emit("exit", 0, null);
+      });
       return;
     }
     if (m.type === "compute" && typeof m.sense === "string") {
@@ -37,6 +42,7 @@ function makeMockChild(pid = 1): MockChild {
     }
   });
   child.kill = vi.fn((_signal?: string) => {
+    child.connected = false;
     child.emit("exit", null, _signal ?? "SIGKILL");
   });
   child.pid = pid;
@@ -59,6 +65,14 @@ const { createLogStore } = await import("@uncaged/nerve-store");
 // Helpers
 // ---------------------------------------------------------------------------
 
+/** `WorkerRuntime.start` schedules `fork` on the next microtask — flush one tick per initial group. */
+async function flushSenseWorkerForkMicrotasks(kernel: { groups: Set<string> }): Promise<void> {
+  const n = kernel.groups.size;
+  for (let i = 0; i < n; i++) {
+    await Promise.resolve();
+  }
+}
+
 function makeConfig(overrides: Partial<NerveConfig> = {}): NerveConfig {
   return {
     senses: {
@@ -173,6 +187,7 @@ describe("kernel — message routing", () => {
       },
     });
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
 
     const child = mockChildren[0];
     child.emit("message", { type: "error", sense: "cpu-usage", error: "compute failed" });
@@ -201,6 +216,7 @@ describe("kernel — message routing", () => {
       },
     });
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
 
     const child = mockChildren[0];
     const callsBefore = stderrSpy.mock.calls.length;
@@ -228,6 +244,7 @@ describe("kernel — message routing", () => {
       },
     });
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
 
     const child = mockChildren[0];
     expect(() => child.emit("message", { type: "unknown-type" })).not.toThrow();
@@ -290,6 +307,7 @@ describe("kernel — groupForSense mapping", () => {
       api: { port: null, token: null, host: "127.0.0.1" },
     };
     const kernel = createKernel(config, nerveRoot);
+    await flushSenseWorkerForkMicrotasks(kernel);
 
     // system and network = 2 unique groups
     expect(mockChildren.length).toBe(2);
@@ -311,8 +329,10 @@ describe("kernel — groupForSense mapping", () => {
       },
     });
     const kernel = createKernel(config, nerveRoot);
-
+    await flushSenseWorkerForkMicrotasks(kernel);
     const child = mockChildren[0];
+    child.emit("message", { type: "ready" });
+
     vi.advanceTimersByTime(500);
 
     expect(child.send).toHaveBeenCalledWith(

packages/daemon/src/__tests__/worker-pool.test.ts

@@ -50,6 +50,7 @@ async function startWorkerWithReady(
   group: string,
 ): Promise<void> {
   const pr = pool.startWorker(group);
+  await Promise.resolve();
   const child = mockChildren[mockChildren.length - 1];
   child.emit("message", { type: "ready" });
   await pr;
@@ -137,6 +138,7 @@ describe("createSenseWorkerPool", () => {
     expect(pool.activeGroupCount()).toBe(1);
     pool.evictGroup("x");
     expect(pool.hasWorkerForGroup("x")).toBe(false);
+    await Promise.resolve();
     expect(mockChildren[0].send).toHaveBeenCalledWith(
       expect.objectContaining({ type: "shutdown" }),
     );
@@ -159,6 +161,7 @@ describe("createSenseWorkerPool", () => {
 
     const p = pool.restartGroup("g");
     expect(onBeforeGroupRestart).toHaveBeenCalledWith("g");
+    await Promise.resolve();
     expect(mockChildren[0].send).toHaveBeenCalledWith(
       expect.objectContaining({ type: "shutdown" }),
     );
@@ -171,7 +174,7 @@ describe("createSenseWorkerPool", () => {
   });
 
   it("onWorkerCrashed runs and schedules respawn after non-zero exit", async () => {
-    vi.useFakeTimers({ shouldAdvanceTime: true });
+    vi.useFakeTimers();
     const onWorkerCrashed = vi.fn();
     const pool = createSenseWorkerPool({
       nerveRoot: "/tmp/n",

packages/daemon/src/__tests__/worker-runtime.test.ts

@@ -0,0 +1,180 @@
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { createWorkerRuntime } from "../worker-runtime.js";
+
+const fixturesDir = join(dirname(fileURLToPath(import.meta.url)), "fixtures");
+const echoWorkerPath = join(fixturesDir, "echo-worker.js");
+const crashWorkerPath = join(fixturesDir, "crash-worker.js");
+const stderrWorkerPath = join(fixturesDir, "stderr-worker.js");
+
+function baseConfig(script: string) {
+  return {
+    script,
+    argsForKey: () => [],
+    forwardStderr: true,
+    onMessage: vi.fn(),
+    onReady: vi.fn(),
+    onExit: vi.fn(),
+    respawn: {
+      enabled: true,
+      maxCrashes: 6,
+      windowMs: 60_000,
+      delayMs: 80,
+      allowRespawn: null,
+    },
+    shutdownTimeoutMs: 5000,
+  };
+}
+
+describe("createWorkerRuntime", () => {
+  const runtimes: Array<{ shutdown: () => Promise<void> }> = [];
+
+  afterEach(async () => {
+    await Promise.all(runtimes.splice(0).map((r) => r.shutdown()));
+  });
+
+  function track<R extends { shutdown: () => Promise<void> }>(r: R): R {
+    runtimes.push(r);
+    return r;
+  }
+
+  it("start + send message + receive echo", async () => {
+    const incoming: unknown[] = [];
+    const rt = track(
+      createWorkerRuntime({
+        ...baseConfig(echoWorkerPath),
+        onMessage: (_key, msg) => {
+          incoming.push(msg);
+        },
+      }),
+    );
+
+    await rt.start("a");
+    expect(rt.has("a")).toBe(true);
+    await rt.send("a", { type: "ping", n: 1 });
+
+    await vi.waitFor(() => {
+      expect(incoming.some((m) => isEchoOf(m, { type: "ping", n: 1 }))).toBe(true);
+    });
+    await rt.shutdown();
+  });
+
+  it("cold start on send (no explicit start)", async () => {
+    const incoming: unknown[] = [];
+    const rt = track(
+      createWorkerRuntime({
+        ...baseConfig(echoWorkerPath),
+        onMessage: (_key, msg) => {
+          incoming.push(msg);
+        },
+      }),
+    );
+
+    expect(rt.has("x")).toBe(false);
+    await rt.send("x", { type: "hi" });
+    await vi.waitFor(() => {
+      expect(rt.has("x")).toBe(true);
+      expect(incoming.some((m) => isEchoOf(m, { type: "hi" }))).toBe(true);
+    });
+    await rt.shutdown();
+  });
+
+  it("evict stops worker; has() is false", async () => {
+    const rt = track(createWorkerRuntime(baseConfig(echoWorkerPath)));
+    await rt.start("k");
+    expect(rt.has("k")).toBe(true);
+    await rt.evict("k");
+    expect(rt.has("k")).toBe(false);
+    await rt.shutdown();
+  });
+
+  it("drain stops and respawns (new pid)", async () => {
+    const rt = track(createWorkerRuntime(baseConfig(echoWorkerPath)));
+    await rt.start("k");
+    const before = rt.pid("k");
+    expect(before).not.toBeNull();
+    await rt.drain("k");
+    const after = rt.pid("k");
+    expect(after).not.toBeNull();
+    expect(after).not.toBe(before);
+    await rt.shutdown();
+  });
+
+  it("crash triggers auto-respawn", async () => {
+    const incoming: unknown[] = [];
+    const onExit = vi.fn();
+    const rt = track(
+      createWorkerRuntime({
+        ...baseConfig(crashWorkerPath),
+        onExit,
+        onMessage: (_key, msg) => {
+          incoming.push(msg);
+        },
+      }),
+    );
+
+    await rt.start("c");
+
+    await vi.waitFor(() => expect(onExit.mock.calls.length).toBeGreaterThanOrEqual(1), {
+      timeout: 3000,
+    });
+    await vi.waitFor(() => expect(rt.has("c")).toBe(true), { timeout: 3000 });
+
+    await rt.send("c", { type: "after-crash" });
+    await vi.waitFor(() => {
+      expect(incoming.some((m) => isEchoOf(m, { type: "after-crash" }))).toBe(true);
+    });
+    await rt.shutdown();
+  });
+
+  it("crash limit reached → no more automatic respawns", async () => {
+    const rt = track(
+      createWorkerRuntime({
+        ...baseConfig(crashWorkerPath),
+        respawn: {
+          enabled: true,
+          maxCrashes: 2,
+          windowMs: 60_000,
+          delayMs: 50,
+          allowRespawn: null,
+        },
+      }),
+    );
+
+    await rt.start("z");
+
+    await vi.waitFor(() => expect(rt.has("z")).toBe(false), { timeout: 8000 });
+
+    await rt.shutdown();
+  });
+
+  it("shutdown stops all workers", async () => {
+    const rt = track(createWorkerRuntime(baseConfig(echoWorkerPath)));
+    await rt.start("a");
+    await rt.start("b");
+    expect(rt.keys().sort()).toEqual(["a", "b"].sort());
+    await rt.shutdown();
+    expect(rt.keys()).toEqual([]);
+    expect(rt.has("a")).toBe(false);
+    expect(rt.has("b")).toBe(false);
+  });
+
+  it("stderrTail captures stderr output", async () => {
+    const rt = track(createWorkerRuntime(baseConfig(stderrWorkerPath)));
+    await rt.start("s");
+    await vi.waitFor(() => {
+      expect(rt.stderrTail("s")).toContain("stderr-marker");
+    });
+    await rt.shutdown();
+  });
+});
+
+function isEchoOf(msg: unknown, payload: unknown): boolean {
+  return (
+    typeof msg === "object" &&
+    msg !== null &&
+    (msg as Record<string, unknown>).type === "echo" &&
+    JSON.stringify((msg as Record<string, unknown>).payload) === JSON.stringify(payload)
+  );
+}

packages/daemon/src/worker-pool.ts

@@ -1,19 +1,13 @@
 /**
- * Sense worker pool — forked child processes per sense group (IPC lifecycle).
+ * Sense worker pool — thin wrapper around WorkerRuntime (RFC-006): one fork per sense group.
  */
 
-import { fork } from "node:child_process";
-import type { ChildProcess } from "node:child_process";
 import { dirname, join } from "node:path";
 import { fileURLToPath } from "node:url";
 
-import type { ComputeMessage, ShutdownMessage } from "./ipc.js";
+import type { ComputeMessage } from "./ipc.js";
-import { parseWorkerMessage } from "./ipc.js";
+import { formatCapturedStderrTail, formatChildExitSummary } from "./worker-fork-support.js";
-import {
+import { createWorkerRuntime } from "./worker-runtime.js";
-  formatCapturedStderrTail,
-  formatChildExitSummary,
-  teeCapturedStderr,
-} from "./worker-fork-support.js";
 
 export function resolveWorkerScript(): string {
   const __filename = fileURLToPath(import.meta.url);
@@ -21,17 +15,12 @@ export function resolveWorkerScript(): string {
   return join(__dir, "sense-worker.js");
 }
 
-type WorkerEntry = {
-  group: string;
-  process: ChildProcess;
-};
-
 export type SenseWorkerPoolOptions = {
   nerveRoot: string;
   workerScript: string;
   /** Invoked for every IPC message from a worker (including ready / signal / error). */
   onWorkerMessage: (raw: unknown) => void;
-  /** Sense names in a group — used when clearing scheduler state on crash or restart. */
+  /** Sense names in a group — reserved for scheduler-aligned cleanup (kernel passes current config). */
   sensesForGroup: (group: string) => string[];
   /**
    * Called when a worker exits with non-zero code before scheduling a respawn
@@ -58,144 +47,106 @@ export type SenseWorkerPool = {
   activeGroupCount: () => number;
 };
 
-function spawnWorker(
+/** Matches legacy pool: long crash window, 1s respawn delay, practical unlimited respawns. */
-  nerveRoot: string,
+const SENSE_WORKER_RESPAWN = {
-  group: string,
+  enabled: true,
-  workerScript: string,
+  maxCrashes: 100_000,
-  stderrTail: { value: string },
+  windowMs: 86_400_000,
-): ChildProcess {
+  delayMs: 1000,
-  const child = fork(workerScript, ["--group", group, "--root", nerveRoot], {
+} as const;
-    stdio: ["ignore", "inherit", "pipe", "ipc"],
-  });
-  teeCapturedStderr(child, stderrTail);
-  child.on("error", (err) => {
-    if ((err as NodeJS.ErrnoException).code !== "EPIPE") {
-      console.error("[worker] error:", err.message);
-    }
-  });
-  return child;
-}
-
-function sendComputeToProcess(worker: ChildProcess, senseName: string): void {
-  if (worker.connected === false) return;
-  const msg: ComputeMessage = { type: "compute", sense: senseName };
-  try {
-    worker.send(msg);
-  } catch {
-    // IPC channel closed between connected check and send
-  }
-}
-
-function sendShutdownToProcess(worker: ChildProcess): void {
-  if (worker.connected === false) return;
-  const msg: ShutdownMessage = { type: "shutdown" };
-  try {
-    worker.send(msg);
-  } catch {
-    // IPC channel closed between connected check and send
-  }
-}
-
-function waitForExit(child: ChildProcess, timeoutMs: number): Promise<void> {
-  return new Promise((resolve) => {
-    const timer = setTimeout(() => {
-      child.kill("SIGKILL");
-      resolve();
-    }, timeoutMs);
-    child.once("exit", () => {
-      clearTimeout(timer);
-      resolve();
-    });
-  });
-}
 
 export function createSenseWorkerPool(options: SenseWorkerPoolOptions): SenseWorkerPool {
-  const workers = new Map<string, WorkerEntry>();
+  const runtime = createWorkerRuntime<string>({
-
+    script: options.workerScript,
-  function startWorker(group: string): Promise<void> {
+    argsForKey: (group) => ["--group", group, "--root", options.nerveRoot],
-    const stderrTail = { value: "" };
+    forwardStderr: true,
-    const child = spawnWorker(options.nerveRoot, group, options.workerScript, stderrTail);
+    onMessage: (_key, raw) => {
-
-    let workerReadyResolve: (() => void) | undefined;
-    const workerReady = new Promise<void>((resolve) => {
-      workerReadyResolve = resolve;
-    });
-
-    child.on("message", (raw: unknown) => {
-      const result = parseWorkerMessage(raw);
-      if (result.ok && result.value.type === "ready") {
-        workerReadyResolve?.();
-      }
       options.onWorkerMessage(raw);
-    });
+    },
-
+    onReady: (_key, msg) => {
-    child.on("exit", (code, signal) => {
+      options.onWorkerMessage(msg);
-      const summary = formatChildExitSummary(code, signal ?? null);
+    },
+    onExit: (group, code, signal) => {
+      const sig =
+        signal === null || signal === undefined || signal === ""
+          ? null
+          : (signal as NodeJS.Signals);
+      const summary = formatChildExitSummary(code, sig);
       process.stderr.write(
-        `[kernel] worker for group "${group}" exited (${summary})${formatCapturedStderrTail(stderrTail.value)}\n`,
+        `[kernel] worker for group "${group}" exited (${summary})${formatCapturedStderrTail(runtime.stderrTail(group))}\n`,
       );
-      workerReadyResolve?.();
       if (!options.isStopped() && code !== 0) {
         process.stderr.write(`[kernel] respawning worker for group "${group}" in 1s\n`);
         options.onWorkerCrashed(group);
-        setTimeout(() => {
-          if (!options.isStopped()) {
-            startWorker(group);
-          }
-        }, 1000);
       }
-    });
+    },
+    respawn: {
+      ...SENSE_WORKER_RESPAWN,
+      allowRespawn: (_group) => !options.isStopped(),
+    },
+    shutdownTimeoutMs: 5000,
+  });
 
-    workers.set(group, { group, process: child });
+  /** Groups we have ever started — mirrors legacy Map presence for `restartGroup` no-op when unknown. */
-    return workerReady;
+  const trackedGroups = new Set<string>();
+  /** Marks groups mid-evict so `hasWorkerForGroup` drops immediately (legacy synchronous eviction). */
+  const evicting = new Set<string>();
+
+  async function startWorker(group: string): Promise<void> {
+    trackedGroups.add(group);
+    await runtime.start(group);
   }
 
   async function restartGroup(group: string): Promise<void> {
-    const entry = workers.get(group);
+    if (!trackedGroups.has(group)) {
-    if (entry === undefined) return;
+      return;
-
-    options.onBeforeGroupRestart(group);
-
-    sendShutdownToProcess(entry.process);
-    await waitForExit(entry.process, 5000);
-
-    if (!options.isStopped()) {
-      await startWorker(group);
     }
+    options.onBeforeGroupRestart(group);
+    await runtime.drain(group);
   }
 
   function evictGroup(group: string): void {
-    const entry = workers.get(group);
+    trackedGroups.delete(group);
-    if (entry === undefined) return;
+    evicting.add(group);
-    sendShutdownToProcess(entry.process);
+    void runtime.evict(group).finally(() => {
-    workers.delete(group);
+      evicting.delete(group);
+    });
   }
 
   async function shutdownAll(): Promise<void> {
-    const exitPromises: Promise<void>[] = [];
+    await runtime.shutdown();
-    for (const entry of workers.values()) {
+    trackedGroups.clear();
-      sendShutdownToProcess(entry.process);
+    evicting.clear();
-      exitPromises.push(waitForExit(entry.process, 5000));
-    }
-    await Promise.all(exitPromises);
   }
 
   function sendCompute(group: string, senseName: string): void {
-    const entry = workers.get(group);
+    if (!trackedGroups.has(group) || evicting.has(group)) {
-    if (entry === undefined) return;
+      return;
-    sendComputeToProcess(entry.process, senseName);
+    }
+    // Legacy pool: `child.send` no-op when IPC is closed (still allow cold start: child === null).
+    if (runtime.hasDisconnectedChild(group)) {
+      return;
+    }
+    const msg: ComputeMessage = { type: "compute", sense: senseName };
+    if (!runtime.trySendSync(group, msg)) {
+      void runtime.send(group, msg).catch(() => {
+        // IPC channel may close between scheduling and send — same as legacy try/catch on child.send
+      });
+    }
   }
 
   function getWorkerPid(group: string): number | null {
-    return workers.get(group)?.process.pid ?? null;
+    return runtime.pid(group);
   }
 
+  /** True once `startWorker` has been called for the group and it is not mid-evict (matches legacy Map key). */
   function hasWorkerForGroup(group: string): boolean {
-    return workers.has(group);
+    return trackedGroups.has(group) && !evicting.has(group);
   }
 
+  /** Count of sense groups with a worker slot (includes not-yet-ready), excluding evicted keys. */
   function activeGroupCount(): number {
-    return workers.size;
+    return trackedGroups.size;
   }
 
   return {

packages/daemon/src/worker-runtime.ts

@@ -0,0 +1,404 @@
+/**
+ * Generic message-routed worker process manager (RFC-006).
+ * One forked Node child per key; cold start, crash respawn, drain/evict, shutdown.
+ */
+
+import { type ChildProcess, type Serializable, fork } from "node:child_process";
+import { isPlainRecord } from "@uncaged/nerve-core";
+
+const STDERR_TAIL_MAX_CHARS = 2048;
+
+export type WorkerRuntimeConfig<K extends string> = {
+  script: string;
+  argsForKey: (key: K) => string[];
+  /** When false, stderr is not captured into `stderrTail` (e.g. tests without a pipe). */
+  forwardStderr: boolean;
+  onMessage: (key: K, msg: unknown) => void;
+  onReady: (key: K, msg: unknown) => void;
+  onExit: (key: K, code: number | null, signal: string | null) => void;
+  respawn: {
+    enabled: boolean;
+    maxCrashes: number;
+    windowMs: number;
+    delayMs: number;
+    /** When non-null, return false to skip automatic respawn after an unexpected exit. */
+    allowRespawn: ((key: K) => boolean) | null;
+  };
+  shutdownTimeoutMs: number;
+};
+
+export type WorkerRuntime<K extends string> = {
+  send: (key: K, msg: unknown) => Promise<void>;
+  /** When the worker is already ready and IPC-connected, sends synchronously (returns true). Otherwise false — caller may fall back to `send`. */
+  trySendSync: (key: K, msg: unknown) => boolean;
+  start: (key: K) => Promise<void>;
+  evict: (key: K) => Promise<void>;
+  drain: (key: K) => Promise<void>;
+  shutdown: () => Promise<void>;
+  has: (key: K) => boolean;
+  /** True when a child exists but IPC is disconnected (legacy pool skipped sends in this case). */
+  hasDisconnectedChild: (key: K) => boolean;
+  pid: (key: K) => number | null;
+  keys: () => K[];
+  stderrTail: (key: K) => string;
+};
+
+type WorkerMachineState = "stopped" | "starting" | "ready" | "draining";
+
+type ReadyWaiter = {
+  resolve: () => void;
+  reject: (err: Error) => void;
+};
+
+/** Internal: one forked process slot (ManagedWorker). */
+type WorkerSlot<K extends string> = {
+  key: K;
+  state: WorkerMachineState;
+  child: ChildProcess | null;
+  pid: number | null;
+  stderrTail: string;
+  crashTimestamps: number[];
+  expectExit: boolean;
+  readyWaiters: ReadyWaiter[];
+  opChain: Promise<void>;
+};
+
+function isReadyIpcMessage(raw: unknown): boolean {
+  return isPlainRecord(raw) && raw.type === "ready";
+}
+
+function signalToString(signal: NodeJS.Signals | null): string | null {
+  if (signal === null) {
+    return null;
+  }
+  return String(signal);
+}
+
+function attachStderrTail<K extends string>(child: ChildProcess, slot: WorkerSlot<K>): void {
+  const stream = child.stderr;
+  if (stream == null) {
+    return;
+  }
+  stream.setEncoding("utf8");
+  stream.on("data", (chunk: string | Buffer) => {
+    const text = typeof chunk === "string" ? chunk : chunk.toString("utf8");
+    slot.stderrTail = (slot.stderrTail + text).slice(-STDERR_TAIL_MAX_CHARS);
+  });
+}
+
+function enqueueOp<K extends string>(slot: WorkerSlot<K>, fn: () => Promise<void>): Promise<void> {
+  const run = slot.opChain.then(fn, fn);
+  slot.opChain = run.then(
+    () => {},
+    () => {},
+  );
+  return run;
+}
+
+function resolveReadyWaiters<K extends string>(slot: WorkerSlot<K>): void {
+  const waiters = slot.readyWaiters;
+  slot.readyWaiters = [];
+  for (const w of waiters) {
+    w.resolve();
+  }
+}
+
+function rejectReadyWaiters<K extends string>(slot: WorkerSlot<K>, err: Error): void {
+  const waiters = slot.readyWaiters;
+  slot.readyWaiters = [];
+  for (const w of waiters) {
+    w.reject(err);
+  }
+}
+
+function waitForReady<K extends string>(
+  slot: WorkerSlot<K>,
+  shutdownTimeoutMs: number,
+): Promise<void> {
+  if (slot.state === "ready" && slot.child !== null && slot.child.connected) {
+    return Promise.resolve();
+  }
+  return new Promise((resolve, reject) => {
+    let settled = false;
+    const timer = setTimeout(() => {
+      if (!settled) {
+        settled = true;
+        reject(new Error(`Worker "${String(slot.key)}" ready timeout`));
+      }
+    }, shutdownTimeoutMs);
+    slot.readyWaiters.push({
+      resolve: () => {
+        if (settled) {
+          return;
+        }
+        settled = true;
+        clearTimeout(timer);
+        resolve();
+      },
+      reject: (err: Error) => {
+        if (settled) {
+          return;
+        }
+        settled = true;
+        clearTimeout(timer);
+        reject(err);
+      },
+    });
+  });
+}
+
+async function waitForChildExit(child: ChildProcess, timeoutMs: number): Promise<void> {
+  await new Promise<void>((resolve) => {
+    const timer = setTimeout(() => {
+      child.kill("SIGKILL");
+    }, timeoutMs);
+    child.once("exit", () => {
+      clearTimeout(timer);
+      resolve();
+    });
+  });
+}
+
+export function createWorkerRuntime<K extends string>(
+  config: WorkerRuntimeConfig<K>,
+): WorkerRuntime<K> {
+  const workers = new Map<K, WorkerSlot<K>>();
+
+  function getOrCreateSlot(key: K): WorkerSlot<K> {
+    let slot = workers.get(key);
+    if (slot === undefined) {
+      slot = {
+        key,
+        state: "stopped",
+        child: null,
+        pid: null,
+        stderrTail: "",
+        crashTimestamps: [],
+        expectExit: false,
+        readyWaiters: [],
+        opChain: Promise.resolve(),
+      };
+      workers.set(key, slot);
+    }
+    return slot;
+  }
+
+  function handleWorkerMessage(slot: WorkerSlot<K>, msg: unknown): void {
+    if (isReadyIpcMessage(msg)) {
+      if (slot.state === "starting") {
+        slot.state = "ready";
+        config.onReady(slot.key, msg);
+        resolveReadyWaiters(slot);
+      }
+      return;
+    }
+    config.onMessage(slot.key, msg);
+  }
+
+  function onChildExit(
+    slot: WorkerSlot<K>,
+    code: number | null,
+    signal: NodeJS.Signals | null,
+  ): void {
+    config.onExit(slot.key, code, signalToString(signal));
+
+    if (slot.child !== null) {
+      slot.child.removeAllListeners("message");
+      slot.child.removeAllListeners("exit");
+    }
+
+    const wasExpect = slot.expectExit;
+    slot.expectExit = false;
+
+    slot.child = null;
+    slot.pid = null;
+
+    if (wasExpect) {
+      slot.state = "stopped";
+      return;
+    }
+
+    rejectReadyWaiters(slot, new Error(`Worker "${String(slot.key)}" exited unexpectedly`));
+    slot.state = "stopped";
+
+    void enqueueOp(slot, async () => {
+      await handleUnexpectedCrashRecovery(slot);
+    });
+  }
+
+  function registerChild(slot: WorkerSlot<K>, child: ChildProcess): void {
+    slot.child = child;
+    slot.pid = child.pid ?? null;
+    if (config.forwardStderr) {
+      attachStderrTail(child, slot);
+    }
+    child.on("message", (msg: unknown) => {
+      handleWorkerMessage(slot, msg);
+    });
+    child.on("exit", (code, sig) => {
+      onChildExit(slot, code, sig ?? null);
+    });
+  }
+
+  async function forkAndWaitReady(slot: WorkerSlot<K>): Promise<void> {
+    if (slot.state === "ready" && slot.child !== null && slot.child.connected) {
+      return;
+    }
+
+    slot.state = "starting";
+
+    let child: ChildProcess;
+    try {
+      child = fork(config.script, config.argsForKey(slot.key), {
+        stdio: ["ignore", "inherit", "pipe", "ipc"],
+        env: process.env,
+      });
+    } catch (e) {
+      slot.state = "stopped";
+      const err = e instanceof Error ? e : new Error(String(e));
+      rejectReadyWaiters(slot, err);
+      throw err;
+    }
+
+    registerChild(slot, child);
+    await waitForReady(slot, config.shutdownTimeoutMs);
+  }
+
+  async function gracefulStop(slot: WorkerSlot<K>): Promise<void> {
+    if (slot.child === null) {
+      return;
+    }
+    slot.expectExit = true;
+    slot.state = "draining";
+    const child = slot.child;
+    try {
+      child.send({ type: "shutdown" });
+    } catch {
+      // IPC channel may have closed between null-check and send
+    }
+    await waitForChildExit(child, config.shutdownTimeoutMs);
+  }
+
+  async function handleUnexpectedCrashRecovery(slot: WorkerSlot<K>): Promise<void> {
+    if (!config.respawn.enabled) {
+      return;
+    }
+    if (config.respawn.allowRespawn !== null && !config.respawn.allowRespawn(slot.key)) {
+      return;
+    }
+
+    const now = Date.now();
+    slot.crashTimestamps.push(now);
+    slot.crashTimestamps = slot.crashTimestamps.filter((t) => now - t <= config.respawn.windowMs);
+
+    if (slot.crashTimestamps.length >= config.respawn.maxCrashes) {
+      console.error(
+        `[WorkerRuntime] worker "${String(slot.key)}" exceeded crash limit (${String(config.respawn.maxCrashes)} in ${String(config.respawn.windowMs)}ms); not respawning`,
+      );
+      return;
+    }
+
+    await new Promise<void>((resolve) => setTimeout(resolve, config.respawn.delayMs));
+    await forkAndWaitReady(slot);
+  }
+
+  async function shutdownWorker(slot: WorkerSlot<K>): Promise<void> {
+    await gracefulStop(slot);
+    workers.delete(slot.key);
+  }
+
+  function isActive(slot: WorkerSlot<K>): boolean {
+    return slot.state === "ready" && slot.child !== null && slot.child.connected;
+  }
+
+  return {
+    send: async (key: K, msg: unknown) => {
+      const slot = getOrCreateSlot(key);
+      await enqueueOp(slot, async () => {
+        await forkAndWaitReady(slot);
+        const child = slot.child;
+        if (child === null || !child.connected) {
+          throw new Error(`Worker "${String(key)}" is not connected`);
+        }
+        child.send(msg as Serializable);
+      });
+    },
+
+    trySendSync: (key: K, msg: unknown): boolean => {
+      const slot = workers.get(key);
+      if (slot === undefined || !isActive(slot)) {
+        return false;
+      }
+      const child = slot.child;
+      if (child === null || !child.connected) {
+        return false;
+      }
+      try {
+        child.send(msg as Serializable);
+        return true;
+      } catch {
+        return false;
+      }
+    },
+
+    start: async (key: K) => {
+      const slot = getOrCreateSlot(key);
+      await enqueueOp(slot, async () => {
+        await forkAndWaitReady(slot);
+      });
+    },
+
+    evict: async (key: K) => {
+      const slot = getOrCreateSlot(key);
+      await enqueueOp(slot, async () => {
+        await gracefulStop(slot);
+        workers.delete(key);
+      });
+    },
+
+    drain: async (key: K) => {
+      const slot = getOrCreateSlot(key);
+      await enqueueOp(slot, async () => {
+        if (slot.child === null) {
+          await forkAndWaitReady(slot);
+          return;
+        }
+        await gracefulStop(slot);
+        await forkAndWaitReady(slot);
+      });
+    },
+
+    shutdown: async () => {
+      const snapshot = [...workers.values()];
+      await Promise.all(snapshot.map((slot) => enqueueOp(slot, () => shutdownWorker(slot))));
+    },
+
+    has: (key: K) => {
+      const slot = workers.get(key);
+      return slot !== undefined && isActive(slot);
+    },
+
+    hasDisconnectedChild: (key: K): boolean => {
+      const slot = workers.get(key);
+      if (slot === undefined || slot.child === null) {
+        return false;
+      }
+      return !slot.child.connected;
+    },
+
+    pid: (key: K) => {
+      const slot = workers.get(key);
+      if (slot === undefined || !isActive(slot) || slot.pid === null) {
+        return null;
+      }
+      return slot.pid;
+    },
+
+    keys: () => [...workers.values()].filter((slot) => isActive(slot)).map((slot) => slot.key),
+
+    stderrTail: (key: K) => {
+      const slot = workers.get(key);
+      return slot === undefined ? "" : slot.stderrTail;
+    },
+  };
+}