refactor: migrate workflow-manager process logic to WorkerRuntime (RFC-006 Phase 3)

- workflow-manager.ts: 792 → 498 lines, no more fork/ChildProcess/crash counting
- Extract pure functions to workflow-manager-support.ts (256 lines)
- WorkerRuntime gains: onCrashLimitReached callback, WorkerDrainOpts for per-call timeout
- worker-pool.ts updated for new evict/drain signature (null opts)
- All 167 daemon tests pass

Closes #282

packages/daemon/src/__tests__/crash-recovery.test.ts

@@ -28,6 +28,11 @@ function makeMockChild(pid = 1): MockChild {
   child.connected = true;
   child.exitCode = null;
   child.pid = pid;
+  setImmediate(() => {
+    if (child.connected) {
+      child.emit("message", { type: "ready" });
+    }
+  });
   child.send = vi.fn((msg: unknown) => {
     if (
       msg !== null &&
@@ -132,6 +137,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
 
       mgr.startWorkflow("my-wf", { prompt: "test 1", maxRounds: 10, dryRun: false });
       mgr.startWorkflow("my-wf", { prompt: "test 2", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       expect(mgr.activeCount("my-wf")).toBe(2);
 
       // Simulate unexpected exit (not shutdown)
@@ -159,6 +165,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
 
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       expect(mgr.activeCount("my-wf")).toBe(2);
 
       const child = mockChildren[0];
@@ -183,6 +190,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       expect(mockChildren).toHaveLength(1);
 
       const child = mockChildren[0];
@@ -216,6 +224,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       const firstChild = mockChildren[0];
       firstChild.exitCode = 1;
       firstChild.connected = false;
@@ -260,6 +269,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
 
       // Start one thread to fill the concurrency slot (so queued run stays queued on respawn)
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       const firstChild = mockChildren[0];
       firstChild.exitCode = 1;
       firstChild.connected = false;
@@ -285,6 +295,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       const child = mockChildren[0];
       const startCall = (child.send as ReturnType<typeof vi.fn>).mock.calls[0];
@@ -322,6 +333,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
 
       const launch = { prompt: "build-docker for myrepo", maxRounds: 10, dryRun: false };
       mgr.startWorkflow("my-wf", launch);
+      await vi.runAllTimersAsync();
 
       const startedCall = logStore.upsertWorkflowRun.mock.calls.find(
         (args: any[]) => (args[0] as { type: string }).type === "started",
@@ -357,6 +369,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
 
       // Start one thread to fill the concurrency slot
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       const firstChild = mockChildren[0];
 
       // Crash once → respawn → crash again → second respawn
@@ -398,6 +411,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
       const firstChild = mockChildren[0];
       firstChild.exitCode = 1;
       firstChild.connected = false;
@@ -428,6 +442,7 @@ describe("WorkflowManager — crash recovery (Phase 3)", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("crash-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       // Crash the worker 6 times in rapid succession (within CRASH_WINDOW_MS = 60s)
       for (let i = 0; i < 6; i++) {

packages/daemon/src/__tests__/hot-reload.test.ts

@@ -33,6 +33,11 @@ function makeMockChild(pid = 1): MockChild {
   child.connected = true;
   child.exitCode = null;
   child.pid = pid;
+  setImmediate(() => {
+    if (child.connected) {
+      child.emit("message", { type: "ready" });
+    }
+  });
   child.send = vi.fn((msg: unknown) => {
     if (
       msg !== null &&
@@ -114,6 +119,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     expect(mockChildren).toHaveLength(1);
 
     // Remove workflow from config before drain completes
@@ -134,6 +140,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     expect(mgr.activeCount("my-wf")).toBe(2);
 
     const drainPromise = mgr.drainAndRespawn("my-wf", 5000);
@@ -165,6 +172,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     expect(mockChildren).toHaveLength(1);
 
     const drainPromise = mgr.drainAndRespawn("my-wf", 5000);
@@ -181,6 +189,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     expect(mockChildren).toHaveLength(1);
 
     const drainPromise = mgr.drainAndRespawn("my-wf", 5000);
@@ -198,6 +207,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
 
     const drainPromise = mgr.drainAndRespawn("my-wf", 5000);
     await vi.runAllTimersAsync();
@@ -223,6 +233,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "first", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
 
     const drainPromise = mgr.drainAndRespawn("my-wf", 5000);
     await vi.runAllTimersAsync();
@@ -230,6 +241,7 @@ describe("WorkflowManager — drainAndRespawn (Phase 3 hot reload)", () => {
 
     // Start a new thread on the fresh worker
     mgr.startWorkflow("my-wf", { prompt: "second", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
 
     const newChild = mockChildren[1];
     const startCalls = (newChild.send as ReturnType<typeof vi.fn>).mock.calls.filter(
@@ -257,12 +269,13 @@ describe("WorkflowManager — drainWhenIdle (hot reload without interrupting in-
     vi.clearAllMocks();
   });
 
-  it("does not send shutdown while a thread is still active", () => {
+  it("does not send shutdown while a thread is still active", async () => {
     const logStore = makeLogStore();
     const config = makeWfConfig({ "my-wf": { concurrency: 1, overflow: "drop" } });
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const child = mockChildren[0];
 
     mgr.drainWhenIdle("my-wf");
@@ -282,6 +295,7 @@ describe("WorkflowManager — drainWhenIdle (hot reload without interrupting in-
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const child = mockChildren[0];
     const runId = (child.send as ReturnType<typeof vi.fn>).mock.calls[0][0] as { runId: string };
 
@@ -311,6 +325,7 @@ describe("WorkflowManager — drainWhenIdle (hot reload without interrupting in-
 
     mgr.startWorkflow("my-wf", { prompt: "a", maxRounds: 10, dryRun: false });
     mgr.startWorkflow("my-wf", { prompt: "b", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const child = mockChildren[0];
     const sendMock = child.send as ReturnType<typeof vi.fn>;
     const runIdA = (sendMock.mock.calls[0][0] as { runId: string }).runId;
@@ -355,6 +370,7 @@ describe("WorkflowManager — drainWhenIdle (hot reload without interrupting in-
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const child = mockChildren[0];
     const runId = (child.send as ReturnType<typeof vi.fn>).mock.calls[0][0] as { runId: string };
 
@@ -388,6 +404,7 @@ describe("WorkflowManager — drainWhenIdle (hot reload without interrupting in-
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const child = mockChildren[0];
     const runId = (child.send as ReturnType<typeof vi.fn>).mock.calls[0][0] as { runId: string };
 
@@ -414,6 +431,7 @@ describe("WorkflowManager — drainWhenIdle (hot reload without interrupting in-
     const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
     mgr.startWorkflow("my-wf", { prompt: "once", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const firstChild = mockChildren[0];
     const runId = (firstChild.send as ReturnType<typeof vi.fn>).mock.calls[0][0] as {
       runId: string;
@@ -471,6 +489,7 @@ describe("Kernel — workflow hot reload via file-watcher (Phase 3)", () => {
 
     // Trigger a workflow thread so a worker is spawned
     kernel.workflowManager.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
 
     // Manually call drainAndRespawn (simulating what kernel does on workflow file change)
     const drainPromise = kernel.workflowManager.drainAndRespawn("my-wf", 1000);
@@ -511,6 +530,7 @@ describe("Kernel — workflow hot reload via file-watcher (Phase 3)", () => {
       maxRounds: 10,
       dryRun: false,
     });
+    await vi.runAllTimersAsync();
     expect(mockChildren).toHaveLength(1);
 
     // Reload config without old-wf
@@ -551,6 +571,7 @@ describe("Kernel — workflow hot reload via file-watcher (Phase 3)", () => {
     });
 
     kernel.workflowManager.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     const workersBefore = mockChildren.length;
 
     // Reload with updated concurrency — should NOT spawn a new workflow worker
@@ -573,6 +594,7 @@ describe("Kernel — workflow hot reload via file-watcher (Phase 3)", () => {
     // Can now start up to 5 concurrent threads (previously only 1)
     kernel.workflowManager.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
     kernel.workflowManager.startWorkflow("my-wf", { prompt: "test", maxRounds: 10, dryRun: false });
+    await vi.runAllTimersAsync();
     expect(kernel.workflowManager.activeCount("my-wf")).toBe(3);
 
     const stopPromise = kernel.stop();

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

@@ -194,6 +194,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       // A workflow worker should be spawned and a start-thread message sent
       const workflowWorker = mockChildren.find((c) =>
         (c.send as ReturnType<typeof vi.fn>).mock.calls.some(
@@ -252,6 +254,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       // Find the start-thread call and verify triggerPayload
       const startThreadCall = mockChildren
         .flatMap((c) => (c.send as ReturnType<typeof vi.fn>).mock.calls as [unknown][])
@@ -306,6 +310,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       const senseEntries = logStore.append.mock.calls
         .map((c) => c[0] as { source: string; type: string; refId: string | null })
         .filter((e) => e.source === "sense" && e.refId === "cpu-usage");
@@ -423,6 +429,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       expect(logStore.upsertWorkflowRun).toHaveBeenCalledWith(
         expect.objectContaining({ source: "workflow", type: "started" }),
         expect.objectContaining({ workflow: "log-test-workflow", status: "started" }),
@@ -498,6 +506,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       const startThreadCall = mockChildren
         .flatMap((c) => (c.send as ReturnType<typeof vi.fn>).mock.calls as [unknown][])
         .find(
@@ -582,6 +592,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       const startThreadCall = mockChildren
         .flatMap((c) => (c.send as ReturnType<typeof vi.fn>).mock.calls as [unknown][])
         .find(
@@ -642,6 +654,8 @@ describe("kernel + workflowManager integration", () => {
         });
       }
 
+      await vi.runAllTimersAsync();
+
       const stopPromise = kernel.stop();
       await vi.runAllTimersAsync();
       await expect(stopPromise).resolves.toBeUndefined();

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

@@ -16,6 +16,7 @@ function baseConfig(script: string) {
     onMessage: vi.fn(),
     onReady: vi.fn(),
     onExit: vi.fn(),
+    onCrashLimitReached: null,
     respawn: {
       enabled: true,
       maxCrashes: 6,
@@ -84,7 +85,7 @@ describe("createWorkerRuntime", () => {
     const rt = track(createWorkerRuntime(baseConfig(echoWorkerPath)));
     await rt.start("k");
     expect(rt.has("k")).toBe(true);
-    await rt.evict("k");
+    await rt.evict("k", null);
     expect(rt.has("k")).toBe(false);
     await rt.shutdown();
   });
@@ -94,7 +95,7 @@ describe("createWorkerRuntime", () => {
     await rt.start("k");
     const before = rt.pid("k");
     expect(before).not.toBeNull();
-    await rt.drain("k");
+    await rt.drain("k", null);
     const after = rt.pid("k");
     expect(after).not.toBeNull();
     expect(after).not.toBe(before);

packages/daemon/src/__tests__/workflow-manager.test.ts

@@ -26,6 +26,11 @@ function makeMockChild(pid = 1): MockChild {
   child.connected = true;
   child.exitCode = null;
   child.pid = pid;
+  setImmediate(() => {
+    if (child.connected) {
+      child.emit("message", { type: "ready" });
+    }
+  });
   child.send = vi.fn((msg: unknown) => {
     if (
       msg !== null &&
@@ -110,7 +115,7 @@ describe("WorkflowManager", () => {
   });
 
   describe("startWorkflow under concurrency limit dispatches thread", () => {
-    it("forks a worker and sends start-thread when active < concurrency", () => {
+    it("forks a worker and sends start-thread when active < concurrency", async () => {
       const logStore = makeLogStore();
       const config = makeConfig({
         "my-workflow": { concurrency: 2, overflow: "drop" },
@@ -118,6 +123,7 @@ describe("WorkflowManager", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("my-workflow", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       expect(mockChildren).toHaveLength(1);
       expect(mockChildren[0].send).toHaveBeenCalledWith(
@@ -126,7 +132,7 @@ describe("WorkflowManager", () => {
       expect(mgr.activeCount("my-workflow")).toBe(1);
     });
 
-    it("reuses the same worker for a second thread under the limit", () => {
+    it("reuses the same worker for a second thread under the limit", async () => {
       const logStore = makeLogStore();
       const config = makeConfig({
         "my-workflow": { concurrency: 3, overflow: "drop" },
@@ -135,6 +141,7 @@ describe("WorkflowManager", () => {
 
       mgr.startWorkflow("my-workflow", { prompt: "test 1", maxRounds: 10, dryRun: false });
       mgr.startWorkflow("my-workflow", { prompt: "test 2", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       // Only one forked child — worker is reused
       expect(mockChildren).toHaveLength(1);
@@ -142,7 +149,7 @@ describe("WorkflowManager", () => {
       expect(mgr.activeCount("my-workflow")).toBe(2);
     });
 
-    it("logs a 'started' event for each dispatched thread", () => {
+    it("logs a 'started' event for each dispatched thread", async () => {
       const logStore = makeLogStore();
       const config = makeConfig({
         "my-workflow": { concurrency: 2, overflow: "drop" },
@@ -150,6 +157,7 @@ describe("WorkflowManager", () => {
       const mgr = createWorkflowManager("/nerve-root", config, logStore);
 
       mgr.startWorkflow("my-workflow", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       expect(logStore.upsertWorkflowRun).toHaveBeenCalledWith(
         expect.objectContaining({ source: "workflow", type: "started" }),
@@ -159,7 +167,7 @@ describe("WorkflowManager", () => {
   });
 
   describe("startWorkflow at limit with drop overflow drops the request", () => {
-    it("does NOT send start-thread when at concurrency limit with overflow=drop", () => {
+    it("does NOT send start-thread when at concurrency limit with overflow=drop", async () => {
       const logStore = makeLogStore();
       const config = makeConfig({
         "drop-wf": { concurrency: 1, overflow: "drop" },
@@ -169,6 +177,7 @@ describe("WorkflowManager", () => {
       mgr.startWorkflow("drop-wf", { prompt: "first", maxRounds: 10, dryRun: false });
       // now at limit — second call should be dropped
       mgr.startWorkflow("drop-wf", { prompt: "second", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       expect(mgr.activeCount("drop-wf")).toBe(1);
       expect(mgr.queueLength("drop-wf")).toBe(0);
@@ -254,7 +263,7 @@ describe("WorkflowManager", () => {
   });
 
   describe("completing a thread dequeues the next one", () => {
-    it("dispatches the next queued thread when the active thread sends completed", () => {
+    it("dispatches the next queued thread when the active thread sends completed", async () => {
       const logStore = makeLogStore();
       const config = makeConfig({
         "queue-wf": { concurrency: 1, overflow: "queue", maxQueue: 5 },
@@ -263,6 +272,7 @@ describe("WorkflowManager", () => {
 
       mgr.startWorkflow("queue-wf", { prompt: "first", maxRounds: 10, dryRun: false });
       mgr.startWorkflow("queue-wf", { prompt: "second", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       expect(mgr.activeCount("queue-wf")).toBe(1);
       expect(mgr.queueLength("queue-wf")).toBe(1);
@@ -289,7 +299,7 @@ describe("WorkflowManager", () => {
       );
     });
 
-    it("dispatches next queued thread when active thread sends failed", () => {
+    it("dispatches next queued thread when active thread sends failed", async () => {
       const logStore = makeLogStore();
       const config = makeConfig({
         "queue-wf": { concurrency: 1, overflow: "queue", maxQueue: 5 },
@@ -298,6 +308,7 @@ describe("WorkflowManager", () => {
 
       mgr.startWorkflow("queue-wf", { prompt: "first", maxRounds: 10, dryRun: false });
       mgr.startWorkflow("queue-wf", { prompt: "second", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       const child = mockChildren[0];
       const firstRunId = (child.send as ReturnType<typeof vi.fn>).mock.calls[0][0].runId as string;
@@ -325,6 +336,7 @@ describe("WorkflowManager", () => {
 
       mgr.startWorkflow("wf-a", { prompt: "test", maxRounds: 10, dryRun: false });
       mgr.startWorkflow("wf-b", { prompt: "test", maxRounds: 10, dryRun: false });
+      await vi.runAllTimersAsync();
 
       // Two distinct workers should have been forked
       expect(mockChildren).toHaveLength(2);

packages/daemon/src/worker-pool.ts

@@ -66,6 +66,7 @@ export function createSenseWorkerPool(options: SenseWorkerPoolOptions): SenseWor
     onReady: (_key, msg) => {
       options.onWorkerMessage(msg);
     },
+    onCrashLimitReached: null,
     onExit: (group, code, signal) => {
       const sig =
         signal === null || signal === undefined || signal === ""
@@ -102,13 +103,13 @@ export function createSenseWorkerPool(options: SenseWorkerPoolOptions): SenseWor
       return;
     }
     options.onBeforeGroupRestart(group);
-    await runtime.drain(group);
+    await runtime.drain(group, null);
   }
 
   function evictGroup(group: string): void {
     trackedGroups.delete(group);
     evicting.add(group);
-    void runtime.evict(group).finally(() => {
+    void runtime.evict(group, null).finally(() => {
       evicting.delete(group);
     });
   }

packages/daemon/src/worker-runtime.ts

@@ -8,6 +8,10 @@ import { isPlainRecord } from "@uncaged/nerve-core";
 
 const STDERR_TAIL_MAX_CHARS = 2048;
 
+export type WorkerDrainOpts = {
+  shutdownTimeoutMs: number | null;
+};
+
 export type WorkerRuntimeConfig<K extends string> = {
   script: string;
   argsForKey: (key: K) => string[];
@@ -16,6 +20,8 @@ export type WorkerRuntimeConfig<K extends string> = {
   onMessage: (key: K, msg: unknown) => void;
   onReady: (key: K, msg: unknown) => void;
   onExit: (key: K, code: number | null, signal: string | null) => void;
+  /** Invoked when automatic respawn is skipped because `maxCrashes` was exceeded in `windowMs`. */
+  onCrashLimitReached: ((key: K) => void) | null;
   respawn: {
     enabled: boolean;
     maxCrashes: number;
@@ -32,8 +38,8 @@ export type WorkerRuntime<K extends string> = {
   /** 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>;
+  evict: (key: K, opts: WorkerDrainOpts | null) => Promise<void>;
+  drain: (key: K, opts: WorkerDrainOpts | null) => 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). */
@@ -264,7 +270,14 @@ export function createWorkerRuntime<K extends string>(
     await waitForReady(slot, config.shutdownTimeoutMs);
   }
 
-  async function gracefulStop(slot: WorkerSlot<K>): Promise<void> {
+  function resolveShutdownTimeoutMs(opts: WorkerDrainOpts | null): number {
+    if (opts !== null && opts.shutdownTimeoutMs !== null) {
+      return opts.shutdownTimeoutMs;
+    }
+    return config.shutdownTimeoutMs;
+  }
+
+  async function gracefulStop(slot: WorkerSlot<K>, shutdownTimeoutMs: number): Promise<void> {
     if (slot.child === null) {
       return;
     }
@@ -276,7 +289,7 @@ export function createWorkerRuntime<K extends string>(
     } catch {
       // IPC channel may have closed between null-check and send
     }
-    await waitForChildExit(child, config.shutdownTimeoutMs);
+    await waitForChildExit(child, shutdownTimeoutMs);
   }
 
   async function handleUnexpectedCrashRecovery(slot: WorkerSlot<K>): Promise<void> {
@@ -295,6 +308,9 @@ export function createWorkerRuntime<K extends string>(
       console.error(
         `[WorkerRuntime] worker "${String(slot.key)}" exceeded crash limit (${String(config.respawn.maxCrashes)} in ${String(config.respawn.windowMs)}ms); not respawning`,
       );
+      if (config.onCrashLimitReached !== null) {
+        config.onCrashLimitReached(slot.key);
+      }
       return;
     }
 
@@ -303,7 +319,7 @@ export function createWorkerRuntime<K extends string>(
   }
 
   async function shutdownWorker(slot: WorkerSlot<K>): Promise<void> {
-    await gracefulStop(slot);
+    await gracefulStop(slot, config.shutdownTimeoutMs);
     workers.delete(slot.key);
   }
 
@@ -348,22 +364,24 @@ export function createWorkerRuntime<K extends string>(
       });
     },
 
-    evict: async (key: K) => {
+    evict: async (key: K, opts: WorkerDrainOpts | null) => {
       const slot = getOrCreateSlot(key);
+      const shutdownMs = resolveShutdownTimeoutMs(opts);
       await enqueueOp(slot, async () => {
-        await gracefulStop(slot);
+        await gracefulStop(slot, shutdownMs);
         workers.delete(key);
       });
     },
 
-    drain: async (key: K) => {
+    drain: async (key: K, opts: WorkerDrainOpts | null) => {
       const slot = getOrCreateSlot(key);
+      const shutdownMs = resolveShutdownTimeoutMs(opts);
       await enqueueOp(slot, async () => {
         if (slot.child === null) {
           await forkAndWaitReady(slot);
           return;
         }
-        await gracefulStop(slot);
+        await gracefulStop(slot, shutdownMs);
         await forkAndWaitReady(slot);
       });
     },

packages/daemon/src/workflow-manager-support.ts

@@ -0,0 +1,256 @@
+/**
+ * Pure helpers and IPC branching for workflow-manager (keeps workflow-manager.ts lean).
+ */
+
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+import type { WorkflowMessage } from "@uncaged/nerve-core";
+import { START, isPlainRecord } from "@uncaged/nerve-core";
+
+import type { LogStore, WorkflowRunStatus } from "@uncaged/nerve-store";
+import type { ResumeThreadMessage, ThreadEventMessage } from "./ipc.js";
+import type { WorkerToParentMessage } from "./ipc.js";
+
+export type PendingThread = {
+  runId: string;
+  prompt: string;
+  maxRounds: number;
+  dryRun: boolean;
+};
+
+export type WorkflowState = {
+  active: Set<string>;
+  queue: PendingThread[];
+};
+
+/** Matches legacy manager: 6 crashes within 60s stops respawn (was `length > 5`). */
+export const WORKFLOW_WORKER_RESPAWN = {
+  enabled: true,
+  maxCrashes: 6,
+  windowMs: 60_000,
+  delayMs: 0,
+} as const;
+
+/**
+ * Worker shutdown timeout — must stay in sync with SHUTDOWN_TIMEOUT_MS in workflow-worker.ts.
+ * The drain timeout passed to drainAndRespawn must be >= this value so the worker has
+ * enough time to finish in-flight threads before the parent force-kills it.
+ */
+export const WORKER_SHUTDOWN_TIMEOUT_MS = 10_000;
+
+export const DEFAULT_MAX_QUEUE = 100;
+
+export function readLaunchFromTriggerPayload(
+  raw: unknown,
+  engineDefaultMaxRounds: number,
+): { prompt: string; maxRounds: number; dryRun: boolean } {
+  if (isPlainRecord(raw)) {
+    const o = raw;
+    if (typeof o.prompt === "string" && typeof o.maxRounds === "number") {
+      const dryRun = typeof o.dryRun === "boolean" ? o.dryRun : false;
+      return { prompt: o.prompt, maxRounds: o.maxRounds, dryRun };
+    }
+  }
+  return { prompt: "", maxRounds: engineDefaultMaxRounds, dryRun: false };
+}
+
+export function ensureThreadMessagesWithStart(
+  messages: Array<{ role: string; content: string; meta: unknown; timestamp: number }>,
+  threadId: string,
+  fallbackPrompt: string,
+  fallbackMaxRounds: number,
+): WorkflowMessage[] {
+  const mapped: WorkflowMessage[] = messages.map((m) => ({
+    role: m.role,
+    content: m.content,
+    meta: m.meta,
+    timestamp: m.timestamp,
+  }));
+  if (mapped.length > 0 && mapped[0].role === START) {
+    return mapped;
+  }
+  const start: WorkflowMessage = {
+    role: START,
+    content: fallbackPrompt,
+    meta: { maxRounds: fallbackMaxRounds, threadId },
+    timestamp: Date.now(),
+  };
+  return [start, ...mapped];
+}
+
+export function resolveWorkflowWorkerScript(): string {
+  const __filename = fileURLToPath(import.meta.url);
+  const __dir = dirname(__filename);
+  return join(__dir, "workflow-worker.js");
+}
+
+export function mapWorkflowRunStatus(eventType: string): WorkflowRunStatus | null {
+  const map: Record<string, WorkflowRunStatus> = {
+    started: "started",
+    queued: "queued",
+    completed: "completed",
+    failed: "failed",
+    crashed: "crashed",
+    dropped: "dropped",
+    interrupted: "interrupted",
+    killed: "killed",
+  };
+  return map[eventType] ?? null;
+}
+
+export function extractExitCodeFromPayload(payload: unknown): number | null {
+  if (isPlainRecord(payload) && typeof payload.exitCode === "number") {
+    return payload.exitCode;
+  }
+  return null;
+}
+
+export function appendWorkflowRunLog(
+  logStore: LogStore,
+  workflowName: string,
+  runId: string,
+  eventType: string,
+  payload: unknown | undefined,
+  exitCode: number | null,
+): void {
+  const timestamp = Date.now();
+  const serialised = payload !== undefined ? JSON.stringify(payload) : null;
+  const status = mapWorkflowRunStatus(eventType);
+
+  if (status !== null) {
+    logStore.upsertWorkflowRun(
+      {
+        source: "workflow",
+        type: eventType,
+        refId: runId,
+        payload: serialised,
+        timestamp,
+      },
+      { runId, workflow: workflowName, status, timestamp, exitCode },
+    );
+  } else {
+    logStore.append({
+      source: "workflow",
+      type: eventType,
+      refId: runId,
+      payload: serialised,
+      timestamp,
+    });
+  }
+}
+
+export function recoverQueuedRun(
+  workflowName: string,
+  runId: string,
+  state: WorkflowState,
+  logStore: LogStore,
+  engineMaxRounds: number,
+): void {
+  if (state.queue.some((q) => q.runId === runId)) return;
+  const launch = readLaunchFromTriggerPayload(logStore.getTriggerPayload(runId), engineMaxRounds);
+  state.queue.push({
+    runId,
+    prompt: launch.prompt,
+    maxRounds: launch.maxRounds,
+    dryRun: launch.dryRun,
+  });
+  process.stderr.write(
+    `[workflow-manager] crash-recovery: re-queued thread "${runId}" for "${workflowName}"\n`,
+  );
+}
+
+export function recoverStartedRun(
+  workflowName: string,
+  runId: string,
+  state: WorkflowState,
+  logStore: LogStore,
+  engineMaxRounds: number,
+  sendResume: (wf: string, msg: ResumeThreadMessage) => void,
+): void {
+  if (state.active.has(runId)) return;
+  const rawMessages = logStore.getThreadMessages(runId);
+  const launch = readLaunchFromTriggerPayload(logStore.getTriggerPayload(runId), engineMaxRounds);
+  const messages = ensureThreadMessagesWithStart(
+    rawMessages,
+    runId,
+    launch.prompt,
+    launch.maxRounds,
+  );
+  state.active.add(runId);
+  const msg: ResumeThreadMessage = {
+    type: "resume-thread",
+    runId,
+    messages,
+    maxRounds: launch.maxRounds,
+    dryRun: launch.dryRun,
+  };
+  sendResume(workflowName, msg);
+  process.stderr.write(
+    `[workflow-manager] crash-recovery: resuming thread "${runId}" for "${workflowName}" (${String(messages.length)} messages)\n`,
+  );
+}
+
+export function recoverThreadsFromStore(
+  workflowName: string,
+  logStore: LogStore,
+  engineMaxRounds: number,
+  getOrCreateState: (name: string) => WorkflowState,
+  sendResume: (wf: string, msg: ResumeThreadMessage) => void,
+): void {
+  const activeRuns = logStore.getActiveWorkflowRuns(workflowName);
+  const state = getOrCreateState(workflowName);
+
+  for (const run of activeRuns) {
+    if (run.status === "queued") {
+      recoverQueuedRun(workflowName, run.runId, state, logStore, engineMaxRounds);
+    } else if (run.status === "started") {
+      recoverStartedRun(workflowName, run.runId, state, logStore, engineMaxRounds, sendResume);
+    }
+  }
+}
+
+export type WorkflowManagerMessageDeps = {
+  logStore: LogStore;
+  handleThreadEvent: (workflowName: string, msg: ThreadEventMessage) => void;
+  onWorkflowRoleError: (
+    workflowName: string,
+    runId: string,
+    error: string,
+    exitCode: number,
+  ) => void;
+};
+
+export function dispatchWorkflowWorkerMessage(
+  workflowName: string,
+  msg: WorkerToParentMessage,
+  deps: WorkflowManagerMessageDeps,
+): void {
+  if (msg.type === "thread-event") {
+    deps.handleThreadEvent(workflowName, msg);
+    return;
+  }
+
+  if (msg.type === "thread-workflow-message") {
+    deps.logStore.append({
+      source: "workflow",
+      type: "thread_workflow_message",
+      refId: msg.runId,
+      payload: JSON.stringify(msg.message),
+      timestamp: Date.now(),
+    });
+    return;
+  }
+
+  if (msg.type === "workflow-error") {
+    process.stderr.write(
+      `[workflow-manager] workflow-error for runId "${msg.runId}" in "${workflowName}": ${msg.error}\n`,
+    );
+    deps.onWorkflowRoleError(workflowName, msg.runId, msg.error, msg.exitCode);
+    return;
+  }
+
+  if (msg.type === "error") {
+    process.stderr.write(`[workflow-manager] error from "${workflowName}" worker: ${msg.error}\n`);
+  }
+}

packages/daemon/src/workflow-manager.ts

@@ -6,33 +6,24 @@
  * Concurrency and overflow (drop/queue) are enforced here in the parent process.
  */
 
-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 { NerveConfig, WorkflowConfig, WorkflowStatus } from "@uncaged/nerve-core";
 
-import type {
-  NerveConfig,
-  WorkflowConfig,
-  WorkflowMessage,
-  WorkflowStatus,
-} from "@uncaged/nerve-core";
-import { START, isPlainRecord } from "@uncaged/nerve-core";
-
-import type { LogStore, WorkflowRunStatus } from "@uncaged/nerve-store";
-import type {
-  KillThreadMessage,
-  ResumeThreadMessage,
-  ShutdownMessage,
-  StartThreadMessage,
-  ThreadEventMessage,
-} from "./ipc.js";
+import type { LogStore } from "@uncaged/nerve-store";
+import type { KillThreadMessage, StartThreadMessage, ThreadEventMessage } from "./ipc.js";
 import { parseWorkerMessage } from "./ipc.js";
+import { formatCapturedStderrTail, formatChildExitSummary } from "./worker-fork-support.js";
+import { createWorkerRuntime } from "./worker-runtime.js";
 import {
-  formatCapturedStderrTail,
-  formatChildExitSummary,
-  teeCapturedStderr,
-} from "./worker-fork-support.js";
+  DEFAULT_MAX_QUEUE,
+  WORKER_SHUTDOWN_TIMEOUT_MS,
+  WORKFLOW_WORKER_RESPAWN,
+  type WorkflowState,
+  appendWorkflowRunLog,
+  dispatchWorkflowWorkerMessage,
+  extractExitCodeFromPayload,
+  recoverThreadsFromStore,
+  resolveWorkflowWorkerScript,
+} from "./workflow-manager-support.js";
 
 export type WorkflowLaunchParams = {
   prompt: string;
@@ -74,169 +65,107 @@ export type WorkflowManager = {
   stop: () => Promise<void>;
 };
 
-type PendingThread = {
-  runId: string;
-  prompt: string;
-  maxRounds: number;
-  dryRun: boolean;
-};
-
-type WorkflowState = {
-  active: Set<string>;
-  queue: PendingThread[];
-};
-
-type WorkerEntry = {
-  workflowName: string;
-  process: ChildProcess;
-  stopping: boolean;
-  /** When set, the worker is draining before a hot-reload respawn. */
-  draining: boolean;
-  stderrTail: { value: string };
-};
-
-// Crash respawn backoff: track crash timestamps per workflow.
-const MAX_CRASHES_IN_WINDOW = 5;
-const CRASH_WINDOW_MS = 60_000;
-
-/**
- * Worker shutdown timeout — must stay in sync with SHUTDOWN_TIMEOUT_MS in workflow-worker.ts.
- * The drain timeout passed to drainAndRespawn must be >= this value so the worker has
- * enough time to finish in-flight threads before the parent force-kills it.
- */
-const WORKER_SHUTDOWN_TIMEOUT_MS = 10_000;
-
-const DEFAULT_MAX_QUEUE = 100;
-
-function readLaunchFromTriggerPayload(
-  raw: unknown,
-  engineDefaultMaxRounds: number,
-): { prompt: string; maxRounds: number; dryRun: boolean } {
-  if (isPlainRecord(raw)) {
-    const o = raw;
-    if (typeof o.prompt === "string" && typeof o.maxRounds === "number") {
-      const dryRun = typeof o.dryRun === "boolean" ? o.dryRun : false;
-      return { prompt: o.prompt, maxRounds: o.maxRounds, dryRun };
-    }
-  }
-  return { prompt: "", maxRounds: engineDefaultMaxRounds, dryRun: false };
-}
-
-function ensureThreadMessagesWithStart(
-  messages: Array<{ role: string; content: string; meta: unknown; timestamp: number }>,
-  threadId: string,
-  fallbackPrompt: string,
-  fallbackMaxRounds: number,
-): WorkflowMessage[] {
-  const mapped: WorkflowMessage[] = messages.map((m) => ({
-    role: m.role,
-    content: m.content,
-    meta: m.meta,
-    timestamp: m.timestamp,
-  }));
-  if (mapped.length > 0 && mapped[0].role === START) {
-    return mapped;
-  }
-  const start: WorkflowMessage = {
-    role: START,
-    content: fallbackPrompt,
-    meta: { maxRounds: fallbackMaxRounds, threadId },
-    timestamp: Date.now(),
-  };
-  return [start, ...mapped];
-}
-
-function resolveWorkerScript(): string {
-  const __filename = fileURLToPath(import.meta.url);
-  const __dir = dirname(__filename);
-  return join(__dir, "workflow-worker.js");
-}
-
-function spawnWorkflowWorker(
-  nerveRoot: string,
-  workflowName: string,
-  workerScript: string,
-  stderrTail: { value: string },
-): ChildProcess {
-  const child = fork(workerScript, ["--workflow", workflowName, "--root", nerveRoot], {
-    stdio: ["ignore", "inherit", "pipe", "ipc"],
-  });
-  teeCapturedStderr(child, stderrTail);
-  // Prevent unhandled EPIPE when writing to a child whose IPC channel closed
-  child.on("error", (err) => {
-    if ((err as NodeJS.ErrnoException).code !== "EPIPE") {
-      console.error("[worker] error:", err.message);
-    }
-  });
-  return child;
-}
-
-function sendStartThread(worker: ChildProcess, msg: StartThreadMessage): void {
-  if (worker.connected === false) return;
-  try {
-    worker.send(msg);
-  } catch {
-    // IPC channel closed between connected check and send
-  }
-}
-
-function sendShutdown(worker: ChildProcess, entry: WorkerEntry): void {
-  entry.stopping = true;
-  if (worker.connected === false) return;
-  const msg: ShutdownMessage = { type: "shutdown" };
-  try {
-    worker.send(msg);
-  } catch {
-    // IPC channel closed between connected check and send
-  }
-}
-
-function sendResumeThread(worker: ChildProcess, msg: ResumeThreadMessage): void {
-  if (worker.connected === false) return;
-  try {
-    worker.send(msg);
-  } catch {
-    // IPC channel closed between connected check and send
-  }
-}
-
-function sendKillThread(worker: ChildProcess, runId: string): void {
-  if (worker.connected === false) return;
-  const msg: KillThreadMessage = { type: "kill-thread", runId };
-  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 createWorkflowManager(
   nerveRoot: string,
   initialConfig: NerveConfig,
   logStore: LogStore,
 ): WorkflowManager {
-  const workerScript = resolveWorkerScript();
+  const workerScript = resolveWorkflowWorkerScript();
+
+  /**
+   * Default drain timeout must be at least WORKER_SHUTDOWN_TIMEOUT_MS so the worker
+   * has enough time to finish in-flight threads before the parent force-kills it.
+   */
+  const DEFAULT_DRAIN_TIMEOUT_MS = Math.max(30_000, WORKER_SHUTDOWN_TIMEOUT_MS + 5_000);
 
   const states = new Map<string, WorkflowState>();
-  const workers = new Map<string, WorkerEntry>();
-  const crashTimestamps = new Map<string, number[]>();
+  const trackedWorkflows = new Set<string>();
+  const hotReloadEvicting = new Set<string>();
+  const crashRecoveryPending = new Set<string>();
   let stopped = false;
   let config = initialConfig;
   const pendingDrains = new Set<string>();
 
+  function logWorkflowEvent(
+    workflowName: string,
+    runId: string,
+    eventType: string,
+    payload?: unknown,
+    exitCode: number | null = null,
+  ): void {
+    appendWorkflowRunLog(logStore, workflowName, runId, eventType, payload, exitCode);
+  }
+
+  const runtime = createWorkerRuntime<string>({
+    script: workerScript,
+    argsForKey: (workflowName) => ["--workflow", workflowName, "--root", nerveRoot],
+    forwardStderr: true,
+    onMessage: (workflowName, raw) => {
+      handleWorkerMessage(workflowName, raw);
+    },
+    onReady: (workflowName, _msg) => {
+      if (crashRecoveryPending.has(workflowName)) {
+        crashRecoveryPending.delete(workflowName);
+        recoverThreadsFromStore(
+          workflowName,
+          logStore,
+          config.maxRounds,
+          getOrCreateState,
+          (wf, msg) => {
+            sendToWorker(wf, msg);
+          },
+        );
+      }
+    },
+    onExit: (workflowName, code, signalStr) => {
+      const sig =
+        signalStr === null || signalStr === undefined || signalStr === ""
+          ? null
+          : (signalStr as NodeJS.Signals);
+
+      if (hotReloadEvicting.has(workflowName)) {
+        hotReloadEvicting.delete(workflowName);
+        markActiveRunsInterrupted(workflowName);
+        if (!stopped && workflowConfig(workflowName) !== null) {
+          process.stderr.write(
+            `[workflow-manager] worker for "${workflowName}" drained, respawning\n`,
+          );
+        }
+        return;
+      }
+
+      if (stopped) {
+        const state = states.get(workflowName);
+        if (state !== undefined) {
+          state.active.clear();
+        }
+        crashRecoveryPending.delete(workflowName);
+        return;
+      }
+
+      const summary = formatChildExitSummary(code, sig);
+      const stderrExtra = formatCapturedStderrTail(runtime.stderrTail(workflowName));
+      process.stderr.write(
+        `[workflow-manager] worker for "${workflowName}" exited (${summary})${stderrExtra}\n`,
+      );
+
+      cleanupAfterUnexpectedWorkerExit(workflowName);
+      crashRecoveryPending.add(workflowName);
+    },
+    onCrashLimitReached: (workflowName) => {
+      crashRecoveryPending.delete(workflowName);
+      trackedWorkflows.delete(workflowName);
+      process.stderr.write(
+        `[workflow-manager] worker for "${workflowName}" exceeded crash limit (${String(WORKFLOW_WORKER_RESPAWN.maxCrashes)} in ${String(WORKFLOW_WORKER_RESPAWN.windowMs)}ms) — stopping respawn\n`,
+      );
+    },
+    respawn: {
+      ...WORKFLOW_WORKER_RESPAWN,
+      allowRespawn: (_wf) => !stopped,
+    },
+    shutdownTimeoutMs: DEFAULT_DRAIN_TIMEOUT_MS,
+  });
+
   function getOrCreateState(workflowName: string): WorkflowState {
     let state = states.get(workflowName);
     if (state === undefined) {
@@ -250,56 +179,15 @@ export function createWorkflowManager(
     return config.workflows[workflowName] ?? null;
   }
 
-  function toWorkflowRunStatus(eventType: string): WorkflowRunStatus | null {
-    const map: Record<string, WorkflowRunStatus> = {
-      started: "started",
-      queued: "queued",
-      completed: "completed",
-      failed: "failed",
-      crashed: "crashed",
-      dropped: "dropped",
-      interrupted: "interrupted",
-      killed: "killed",
-    };
-    return map[eventType] ?? null;
-  }
-
-  function extractExitCode(payload: unknown): number | null {
-    if (isPlainRecord(payload) && typeof payload.exitCode === "number") {
-      return payload.exitCode;
+  /** IPC send — matches legacy pool: no-op when IPC is disconnected; cold-start via WorkerRuntime.send. */
+  function sendToWorker(workflowName: string, msg: unknown): void {
+    trackedWorkflows.add(workflowName);
+    if (runtime.hasDisconnectedChild(workflowName)) {
+      return;
     }
-    return null;
-  }
-
-  function logWorkflowEvent(
-    workflowName: string,
-    runId: string,
-    eventType: string,
-    payload?: unknown,
-    exitCode: number | null = null,
-  ): void {
-    const timestamp = Date.now();
-    const serialised = payload !== undefined ? JSON.stringify(payload) : null;
-    const status = toWorkflowRunStatus(eventType);
-
-    if (status !== null) {
-      logStore.upsertWorkflowRun(
-        {
-          source: "workflow",
-          type: eventType,
-          refId: runId,
-          payload: serialised,
-          timestamp,
-        },
-        { runId, workflow: workflowName, status, timestamp, exitCode },
-      );
-    } else {
-      logStore.append({
-        source: "workflow",
-        type: eventType,
-        refId: runId,
-        payload: serialised,
-        timestamp,
+    if (!runtime.trySendSync(workflowName, msg)) {
+      void runtime.send(workflowName, msg).catch(() => {
+        // IPC channel may close between scheduling and send
       });
     }
   }
@@ -314,7 +202,6 @@ export function createWorkflowManager(
     const state = getOrCreateState(workflowName);
     state.active.add(runId);
 
-    const worker = getOrSpawnWorker(workflowName);
     const msg: StartThreadMessage = {
       type: "start-thread",
       runId,
@@ -323,7 +210,7 @@ export function createWorkflowManager(
       maxRounds,
       dryRun,
     };
-    sendStartThread(worker.process, msg);
+    sendToWorker(workflowName, msg);
     logWorkflowEvent(workflowName, runId, "started", { prompt, maxRounds, dryRun });
   }
 
@@ -367,92 +254,20 @@ export function createWorkflowManager(
     if (msg.eventType === "completed" || msg.eventType === "failed" || msg.eventType === "killed") {
       state.active.delete(msg.runId);
       dequeueNext(workflowName);
-      const exitCode = extractExitCode(msg.payload);
+      const exitCode = extractExitCodeFromPayload(msg.payload);
       logWorkflowEvent(workflowName, msg.runId, msg.eventType, msg.payload, exitCode);
       maybeDeferredHotReloadDrain(workflowName);
     }
   }
 
-  function recoverQueuedRun(workflowName: string, runId: string, state: WorkflowState): void {
-    if (state.queue.some((q) => q.runId === runId)) return;
-    const launch = readLaunchFromTriggerPayload(
-      logStore.getTriggerPayload(runId),
-      config.maxRounds,
-    );
-    state.queue.push({
-      runId,
-      prompt: launch.prompt,
-      maxRounds: launch.maxRounds,
-      dryRun: launch.dryRun,
-    });
-    process.stderr.write(
-      `[workflow-manager] crash-recovery: re-queued thread "${runId}" for "${workflowName}"\n`,
-    );
-  }
-
-  function recoverStartedRun(
-    workflowName: string,
-    runId: string,
-    state: WorkflowState,
-    worker: WorkerEntry,
-  ): void {
-    if (state.active.has(runId)) return;
-    const rawMessages = logStore.getThreadMessages(runId);
-    const launch = readLaunchFromTriggerPayload(
-      logStore.getTriggerPayload(runId),
-      config.maxRounds,
-    );
-    const messages = ensureThreadMessagesWithStart(
-      rawMessages,
-      runId,
-      launch.prompt,
-      launch.maxRounds,
-    );
-    state.active.add(runId);
-    const msg: ResumeThreadMessage = {
-      type: "resume-thread",
-      runId,
-      messages,
-      maxRounds: launch.maxRounds,
-      dryRun: launch.dryRun,
-    };
-    sendResumeThread(worker.process, msg);
-    process.stderr.write(
-      `[workflow-manager] crash-recovery: resuming thread "${runId}" for "${workflowName}" (${messages.length} messages)\n`,
-    );
-  }
-
-  function recoverThreadsForWorker(workflowName: string, worker: WorkerEntry): void {
-    const activeRuns = logStore.getActiveWorkflowRuns(workflowName);
-    const state = getOrCreateState(workflowName);
-
-    for (const run of activeRuns) {
-      if (run.status === "queued") {
-        recoverQueuedRun(workflowName, run.runId, state);
-      } else if (run.status === "started") {
-        recoverStartedRun(workflowName, run.runId, state, worker);
-      }
-    }
-  }
-
-  function recordCrashAndCheckLimit(workflowName: string): boolean {
-    const now = Date.now();
-    const timestamps = (crashTimestamps.get(workflowName) ?? []).filter(
-      (t) => now - t < CRASH_WINDOW_MS,
-    );
-    timestamps.push(now);
-    crashTimestamps.set(workflowName, timestamps);
-    return timestamps.length > MAX_CRASHES_IN_WINDOW;
-  }
-
-  function handleWorkerCrash(workflowName: string): void {
+  function cleanupAfterUnexpectedWorkerExit(workflowName: string): void {
     const state = states.get(workflowName);
     if (state === undefined) return;
 
     const crashedCount = state.active.size;
     if (crashedCount > 0) {
       process.stderr.write(
-        `[workflow-manager] worker for "${workflowName}" crashed with ${crashedCount} active thread(s)\n`,
+        `[workflow-manager] worker for "${workflowName}" crashed with ${String(crashedCount)} active thread(s)\n`,
       );
       for (const runId of state.active) {
         logWorkflowEvent(workflowName, runId, "crashed", undefined, 255);
@@ -460,26 +275,13 @@ export function createWorkflowManager(
     }
 
     state.active.clear();
-    workers.delete(workflowName);
     pendingDrains.delete(workflowName);
 
-    if (stopped || workflowConfig(workflowName) === null) return;
-
-    if (recordCrashAndCheckLimit(workflowName)) {
-      const count = crashTimestamps.get(workflowName)?.length ?? 0;
+    if (!stopped && workflowConfig(workflowName) !== null) {
       process.stderr.write(
-        `[workflow-manager] worker for "${workflowName}" crashed ${count} times in ${CRASH_WINDOW_MS}ms — stopping respawn\n`,
+        `[workflow-manager] respawning worker for "${workflowName}" after crash\n`,
       );
-      return;
     }
-
-    process.stderr.write(
-      `[workflow-manager] respawning worker for "${workflowName}" after crash\n`,
-    );
-    const newWorker = getOrSpawnWorker(workflowName);
-    setImmediate(() => {
-      recoverThreadsForWorker(workflowName, newWorker);
-    });
   }
 
   function handleWorkerMessage(workflowName: string, raw: unknown): void {
@@ -490,43 +292,19 @@ export function createWorkflowManager(
       );
       return;
     }
-    const msg = result.value;
-
-    if (msg.type === "thread-event") {
-      handleThreadEvent(workflowName, msg);
-      return;
-    }
-
-    if (msg.type === "thread-workflow-message") {
-      logStore.append({
-        source: "workflow",
-        type: "thread_workflow_message",
-        refId: msg.runId,
-        payload: JSON.stringify(msg.message),
-        timestamp: Date.now(),
-      });
-      return;
-    }
-
-    if (msg.type === "workflow-error") {
-      process.stderr.write(
-        `[workflow-manager] workflow-error for runId "${msg.runId}" in "${workflowName}": ${msg.error}\n`,
-      );
-      const state = states.get(workflowName);
-      if (state !== undefined) {
-        state.active.delete(msg.runId);
-        dequeueNext(workflowName);
-      }
-      logWorkflowEvent(workflowName, msg.runId, "failed", { error: msg.error }, msg.exitCode);
-      maybeDeferredHotReloadDrain(workflowName);
-      return;
-    }
-
-    if (msg.type === "error") {
-      process.stderr.write(
-        `[workflow-manager] error from "${workflowName}" worker: ${msg.error}\n`,
-      );
-    }
+    dispatchWorkflowWorkerMessage(workflowName, result.value, {
+      logStore,
+      handleThreadEvent,
+      onWorkflowRoleError: (wf, runId, error, exitCode) => {
+        const state = states.get(wf);
+        if (state !== undefined) {
+          state.active.delete(runId);
+          dequeueNext(wf);
+        }
+        logWorkflowEvent(wf, runId, "failed", { error }, exitCode);
+        maybeDeferredHotReloadDrain(wf);
+      },
+    });
   }
 
   function markActiveRunsInterrupted(workflowName: string): void {
@@ -538,67 +316,6 @@ export function createWorkflowManager(
     state.active.clear();
   }
 
-  function handleWorkerExit(
-    workflowName: string,
-    code: number | null,
-    signal: NodeJS.Signals | null,
-  ): void {
-    const entry = workers.get(workflowName);
-    if (entry?.draining) {
-      workers.delete(workflowName);
-      markActiveRunsInterrupted(workflowName);
-      if (!stopped && workflowConfig(workflowName) !== null) {
-        process.stderr.write(
-          `[workflow-manager] worker for "${workflowName}" drained, respawning\n`,
-        );
-        getOrSpawnWorker(workflowName);
-      }
-      return;
-    }
-    if (entry?.stopping) {
-      workers.delete(workflowName);
-      const state = states.get(workflowName);
-      if (state !== undefined) {
-        state.active.clear();
-      }
-      return;
-    }
-    const summary = formatChildExitSummary(code, signal);
-    const stderrExtra = entry !== undefined ? formatCapturedStderrTail(entry.stderrTail.value) : "";
-    process.stderr.write(
-      `[workflow-manager] worker for "${workflowName}" exited (${summary})${stderrExtra}\n`,
-    );
-    handleWorkerCrash(workflowName);
-  }
-
-  function getOrSpawnWorker(workflowName: string): WorkerEntry {
-    const existing = workers.get(workflowName);
-    if (existing !== undefined && existing.process.exitCode === null) {
-      return existing;
-    }
-
-    const stderrTail = { value: "" };
-    const child = spawnWorkflowWorker(nerveRoot, workflowName, workerScript, stderrTail);
-
-    child.on("message", (raw: unknown) => {
-      handleWorkerMessage(workflowName, raw);
-    });
-
-    child.on("exit", (code, signal) => {
-      handleWorkerExit(workflowName, code, signal ?? null);
-    });
-
-    const entry: WorkerEntry = {
-      workflowName,
-      process: child,
-      stopping: false,
-      draining: false,
-      stderrTail,
-    };
-    workers.set(workflowName, entry);
-    return entry;
-  }
-
   function killThread(runId: string): boolean {
     for (const [workflowName, state] of states) {
       const queueIdx = state.queue.findIndex((q) => q.runId === runId);
@@ -609,10 +326,8 @@ export function createWorkflowManager(
       }
 
       if (state.active.has(runId)) {
-        const workerEntry = workers.get(workflowName);
-        if (workerEntry !== undefined) {
-          sendKillThread(workerEntry.process, runId);
-        }
+        const msg: KillThreadMessage = { type: "kill-thread", runId };
+        sendToWorker(workflowName, msg);
         return true;
       }
     }
@@ -663,7 +378,7 @@ export function createWorkflowManager(
     state.queue.push({ runId, prompt, maxRounds, dryRun });
     logWorkflowEvent(workflowName, runId, "queued");
     process.stderr.write(
-      `[workflow-manager] queued thread for "${workflowName}" runId "${runId}" (queue length: ${state.queue.length})\n`,
+      `[workflow-manager] queued thread for "${workflowName}" runId "${runId}" (queue length: ${String(state.queue.length)})\n`,
     );
   }
 
@@ -707,35 +422,29 @@ export function createWorkflowManager(
     config = newConfig;
   }
 
-  /**
-   * Default drain timeout must be at least WORKER_SHUTDOWN_TIMEOUT_MS so the worker
-   * has enough time to finish in-flight threads before the parent force-kills it.
-   */
-  const DEFAULT_DRAIN_TIMEOUT_MS = Math.max(30_000, WORKER_SHUTDOWN_TIMEOUT_MS + 5_000);
-
   async function drainAndRespawn(
     workflowName: string,
     drainTimeoutMs: number = DEFAULT_DRAIN_TIMEOUT_MS,
   ): Promise<void> {
-    const entry = workers.get(workflowName);
-    if (entry === undefined) {
-      // No active worker — nothing to drain
+    if (!trackedWorkflows.has(workflowName)) {
       return;
     }
 
-    entry.draining = true;
-    // Send shutdown without setting stopping=true (so the exit handler uses the draining branch)
-    if (entry.process.connected) {
-      const msg: ShutdownMessage = { type: "shutdown" };
-      try {
-        entry.process.send(msg);
-      } catch {
-        // IPC closed
+    const shutdownMs = Math.max(drainTimeoutMs, WORKER_SHUTDOWN_TIMEOUT_MS);
+    hotReloadEvicting.add(workflowName);
+    try {
+      await runtime.evict(workflowName, { shutdownTimeoutMs: shutdownMs });
+      trackedWorkflows.delete(workflowName);
+
+      if (!stopped && workflowConfig(workflowName) !== null) {
+        trackedWorkflows.add(workflowName);
+        await runtime.start(workflowName);
       }
+    } finally {
+      hotReloadEvicting.delete(workflowName);
     }
-    await waitForExit(entry.process, drainTimeoutMs);
-    // The exit handler (draining branch) will respawn the worker automatically
   }
+
   function drainWhenIdle(workflowName: string): void {
     const state = states.get(workflowName);
     const hasActiveRuns = state !== undefined && state.active.size > 0;
@@ -761,20 +470,17 @@ export function createWorkflowManager(
 
     pendingDrains.add(workflowName);
     process.stderr.write(
-      `[workflow-manager] deferring hot-reload for "${workflowName}" until ${state.active.size} active run(s) complete\n`,
+      `[workflow-manager] deferring hot-reload for "${workflowName}" until ${String(state.active.size)} active run(s) complete\n`,
     );
   }
 
   async function stop(): Promise<void> {
     stopped = true;
     pendingDrains.clear();
-    const exitPromises: Promise<void>[] = [];
-    for (const entry of workers.values()) {
-      sendShutdown(entry.process, entry);
-      exitPromises.push(waitForExit(entry.process, 5000));
-    }
-    await Promise.all(exitPromises);
-    workers.clear();
+    hotReloadEvicting.clear();
+    crashRecoveryPending.clear();
+    await runtime.shutdown();
+    trackedWorkflows.clear();
   }
 
   return {