Merge pull request #4 from tintinweb/feat/stop-subagents

feat: subagents-api (eventbus) subagent-stop; switch to new API envs; fix bugs

CHANGELOG.md

@@ -5,6 +5,25 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+- **RPC-based subagent spawning** — `TaskExecute` now communicates with `@tintinweb/pi-subagents` via a standardized RPC envelope (`rpcCall` helper) with protocol version negotiation and timeout handling.
+- **RPC-based subagent stopping** — `stopSubagent` sends stop requests via `subagents:rpc:stop` event bus RPC.
+- **TaskOutput supports subagent tasks** — can wait for subagent completion with blocking/timeout, using `subagents:completed` and `subagents:failed` events.
+- **TaskStop supports subagent tasks** — stops running subagents via RPC and marks the task as completed.
+- **Debug logging** — set `PI_TASKS_DEBUG=1` to trace RPC communication (request/reply/timeout) and spawn errors to stderr.
+- **TaskExecute prompt guidelines** — agents are instructed not to use the Agent tool for tasks already launched via TaskExecute.
+- **Biome linter** — added [Biome](https://biomejs.dev/) for correctness linting.
+
+### Changed
+- **TaskOutput/TaskStop accept agent IDs** — both tools now resolve agent IDs (including partial prefixes) to task IDs via `agentTaskMap`, fixing the mismatch where TaskExecute returns agent IDs but TaskOutput/TaskStop only accepted task IDs.
+- **TaskGet shows metadata** — non-empty metadata is now displayed in TaskGet output as JSON.
+- **TaskGet filters completed blockers** — consistent with TaskList, TaskGet now only shows open (non-completed) blockers instead of all dependency edges.
+- **TaskExecute success message** — now includes guidance to use TaskOutput for progress and not spawn duplicate agents.
+- **Softened TaskExecute description** — removed "Requires @tintinweb/pi-subagents extension" from the tool description to prevent agents from refusing to use it when the extension is loaded.
+- **Stopped subagents handled gracefully** — `subagents:failed` listener now distinguishes intentional stops (status `"stopped"` → mark completed, preserve partial result) from actual errors (revert to pending).
+
 ## [0.3.3] - 2026-03-17
 
 ### Added

biome.json

@@ -0,0 +1,26 @@
+{
+	"$schema": "https://biomejs.dev/schemas/2.4.8/schema.json",
+	"linter": {
+		"enabled": true,
+		"rules": {
+			"recommended": true,
+			"style": {
+				"recommended": false
+			},
+			"suspicious": {
+				"noExplicitAny": "off",
+				"noControlCharactersInRegex": "off",
+				"noEmptyInterface": "off"
+			}
+		}
+	},
+	"formatter": {
+		"enabled": false
+	},
+	"files": {
+		"includes": [
+			"src/**/*.ts",
+			"test/**/*.ts"
+		]
+	}
+}

package.json

@@ -27,13 +27,18 @@
     "@sinclair/typebox": "latest"
   },
   "scripts": {
+    "build": "tsc",
+    "prepublishOnly": "npm run lint && npm run typecheck && npm run test && npm run build",
     "test": "vitest run",
     "test:watch": "vitest",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "lint": "biome check src/ test/",
+    "lint:fix": "biome check --fix src/ test/"
   },
   "devDependencies": {
     "@types/node": "^20.0.0",
     "typescript": "^5.0.0",
+    "@biomejs/biome": "^2.3.5",
     "vitest": "^4.0.18"
   },
   "pi": {

src/index.ts

@@ -24,6 +24,13 @@ import { openSettingsMenu } from "./ui/settings-menu.js";
 import { randomUUID } from "node:crypto";
 import { join, resolve } from "node:path";
 
+// ---- Debug ----
+
+const DEBUG = !!process.env.PI_TASKS_DEBUG;
+function debug(...args: unknown[]) {
+  if (DEBUG) console.error("[pi-tasks]", ...args);
+}
+
 // ---- Helpers ----
 
 function textResult(msg: string) {
@@ -74,40 +81,80 @@ export default function (pi: ExtensionAPI) {
   /** Maps agent IDs to task IDs for O(1) completion lookup. */
   const agentTaskMap = new Map<string, string>();
 
-  // ── Subagent extension presence detection ──
-  // Two paths: (1) listen for ready broadcast (subagents loads first),
-  //            (2) send ping on our init (tasks loads first).
-  let subagentsAvailable = false;
+  // ── Subagent RPC helpers ──
 
-  // Ping subagents extension — scoped reply channel, no filtering needed
-  const pingId = randomUUID();
-  const unsubPing = pi.events.on(`subagents:rpc:ping:reply:${pingId}`, () => {
-    subagentsAvailable = true;
-    unsubPing();
-  });
-  pi.events.emit("subagents:rpc:ping", { requestId: pingId });
+  /** RPC reply envelope — matches pi-mono's RpcResponse shape. */
+  type RpcReply<T = void> =
+    | { success: true; data?: T }
+    | { success: false; error: string };
 
-  // Also listen for ready broadcast (covers: subagents loads after us)
-  pi.events.on("subagents:ready", () => {
-    subagentsAvailable = true;
-    unsubPing();   // clean up ping listener if still pending
-  });
+  /** Call a subagents RPC method: emit request, wait for scoped reply, unwrap envelope. */
+  function rpcCall<T>(channel: string, params: Record<string, unknown>, timeoutMs: number): Promise<T> {
+    const requestId = randomUUID();
+    debug(`rpc:send ${channel}`, { requestId });
+    return new Promise<T>((resolve, reject) => {
+      const timer = setTimeout(() => {
+        unsub();
+        debug(`rpc:timeout ${channel}`, { requestId });
+        reject(new Error(`${channel} timeout`));
+      }, timeoutMs);
+      const unsub = pi.events.on(`${channel}:reply:${requestId}`, (raw: unknown) => {
+        unsub(); clearTimeout(timer);
+        debug(`rpc:reply ${channel}`, { requestId, raw });
+        const reply = raw as RpcReply<T>;
+        if (reply.success) resolve(reply.data as T);
+        else reject(new Error(reply.error));
+      });
+      pi.events.emit(channel, { requestId, ...params });
+      debug(`rpc:emitted ${channel}`, { requestId });
+    });
+  }
 
   /** Spawn a subagent via pi.events RPC (requires @tintinweb/pi-subagents extension). */
   function spawnSubagent(type: string, prompt: string, options?: any): Promise<string> {
-    const requestId = randomUUID();
-    return new Promise((resolve, reject) => {
-      const timer = setTimeout(() => { unsub(); reject(new Error("subagents:rpc:spawn timeout")); }, 30000);
-      const unsub = pi.events.on(`subagents:rpc:spawn:reply:${requestId}`, (p: unknown) => {
-        const { id, error } = p as { id?: string; error?: string };
-        unsub(); clearTimeout(timer);
-        if (error) reject(new Error(error));
-        else resolve(id!);
-      });
-      pi.events.emit("subagents:rpc:spawn", { requestId, type, prompt, options });
-    });
+    debug("spawn:call", { type, options: { ...options, prompt: undefined } });
+    return rpcCall<{ id: string }>("subagents:rpc:spawn", { type, prompt, options }, 30_000)
+      .then(d => { debug("spawn:ok", d); return d.id; });
   }
 
+  /** Stop a subagent via pi.events RPC (requires @tintinweb/pi-subagents extension). */
+  function stopSubagent(agentId: string): Promise<void> {
+    return rpcCall<void>("subagents:rpc:stop", { agentId }, 10_000).catch(() => {});
+  }
+
+  // ── Subagent extension presence & version detection ──
+  const PROTOCOL_VERSION = 2;
+  let subagentsAvailable = false;
+  let pendingWarning: string | undefined;
+
+  /** Ping subagents and check protocol version. Works with any handler version. */
+  function checkSubagentsVersion() {
+    const requestId = randomUUID();
+    const timer = setTimeout(() => { unsub(); }, 5_000);
+    const unsub = pi.events.on(`subagents:rpc:ping:reply:${requestId}`, (raw: unknown) => {
+      unsub(); clearTimeout(timer);
+      const remoteVersion = (raw as any)?.data?.version as number | undefined;
+      if (remoteVersion === undefined) {
+        pendingWarning =
+          "@tintinweb/pi-subagents is outdated — please update for task execution support.";
+      } else if (remoteVersion > PROTOCOL_VERSION) {
+        pendingWarning =
+          `@tintinweb/pi-tasks is outdated (protocol v${PROTOCOL_VERSION}, ` +
+          `pi-subagents has v${remoteVersion}) — please update for task execution support.`;
+      } else if (remoteVersion < PROTOCOL_VERSION) {
+        pendingWarning =
+          `@tintinweb/pi-subagents is outdated (protocol v${remoteVersion}, ` +
+          `pi-tasks has v${PROTOCOL_VERSION}) — please update for task execution support.`;
+      } else {
+        subagentsAvailable = true;
+      }
+    });
+    pi.events.emit("subagents:rpc:ping", { requestId });
+  }
+
+  checkSubagentsVersion();
+  pi.events.on("subagents:ready", () => checkSubagentsVersion());
+
   /** Build a prompt for a task being executed by a subagent. */
   function buildTaskPrompt(task: { id: string; subject: string; description: string }, additionalContext?: string): string {
     let prompt = `You are executing task #${task.id}: "${task.subject}"\n\n${task.description}`;
@@ -160,17 +207,22 @@ export default function (pi: ExtensionAPI) {
   });
 
   // Failure → store error, revert to pending, don't cascade (branch stops)
+  // Intentional stop (status === "stopped") → mark completed, preserve partial result
   pi.events.on("subagents:failed", (data) => {
-    const { id, error, status } = data as { id: string; error?: string; status: string };
+    const { id, error, result, status } = data as { id: string; error?: string; result?: string; status: string };
     const taskId = agentTaskMap.get(id);
     if (!taskId) return;
     agentTaskMap.delete(id);
     const task = store.get(taskId);
     if (!task) return;
-    store.update(task.id, {
-      status: "pending",
-      metadata: { ...task.metadata, lastError: error || status },
-    });
+
+    if (status === "stopped") {
+      // Intentional stop — mark completed, preserve partial result
+      store.update(task.id, { status: "completed", metadata: { ...task.metadata, result: result || task.metadata?.result } });
+    } else {
+      // Actual error — revert to pending
+      store.update(task.id, { status: "pending", metadata: { ...task.metadata, lastError: error || status } });
+    }
     widget.setActiveTask(task.id, false);
     widget.update();
   });
@@ -265,6 +317,10 @@ export default function (pi: ExtensionAPI) {
     widget.setUICtx(ctx.ui as UICtx);
     upgradeStoreIfNeeded(ctx);
     showPersistedTasks();
+    if (pendingWarning) {
+      ctx.ui.notify(pendingWarning, "warning");
+      pendingWarning = undefined;
+    }
   });
 
   // session_switch fires on resume (reason: "resume") — reload persisted tasks.
@@ -468,12 +524,24 @@ Returns full task details:
       lines.push(`Description: ${desc}`);
 
       if (task.blockedBy.length > 0) {
-        lines.push(`Blocked by: ${task.blockedBy.map(id => "#" + id).join(", ")}`);
+        const openBlockers = task.blockedBy.filter(bid => {
+          const blocker = store.get(bid);
+          return blocker && blocker.status !== "completed";
+        });
+        if (openBlockers.length > 0) {
+          lines.push(`Blocked by: ${openBlockers.map(id => "#" + id).join(", ")}`);
+        }
       }
       if (task.blocks.length > 0) {
         lines.push(`Blocks: ${task.blocks.map(id => "#" + id).join(", ")}`);
       }
 
+      // Show metadata if non-empty
+      const metaKeys = Object.keys(task.metadata);
+      if (metaKeys.length > 0) {
+        lines.push(`Metadata: ${JSON.stringify(task.metadata)}`);
+      }
+
       return Promise.resolve(textResult(lines.join("\n")));
     },
   });
@@ -630,6 +698,39 @@ Set up task dependencies:
 
       const processOutput = tracker.getOutput(task_id);
       if (!processOutput) {
+        // No shell process — check if this is a subagent task
+        // Support both task IDs and agent IDs (resolve agent ID → task ID)
+        let resolvedId = task_id;
+        if (!store.get(resolvedId)) {
+          // Check if this is an agent ID mapped to a task
+          for (const [agentId, taskId] of agentTaskMap) {
+            if (agentId === task_id || agentId.startsWith(task_id)) { resolvedId = taskId; break; }
+          }
+        }
+        const task = store.get(resolvedId);
+        if (!task) throw new Error(`No task found with ID ${task_id}`);
+
+        if (task.metadata?.agentId) {
+          // Subagent task — wait for completion if blocking
+          if (block && task.status === "in_progress") {
+            await new Promise<void>((resolve) => {
+              const timer = setTimeout(() => { unsubOk(); unsubFail(); resolve(); }, timeout ?? 30000);
+              const cleanup = () => { clearTimeout(timer); resolve(); };
+              const unsubOk = pi.events.on("subagents:completed", (d: unknown) => {
+                if ((d as any).id === task.metadata?.agentId) { unsubOk(); unsubFail(); cleanup(); }
+              });
+              const unsubFail = pi.events.on("subagents:failed", (d: unknown) => {
+                if ((d as any).id === task.metadata?.agentId) { unsubOk(); unsubFail(); cleanup(); }
+              });
+              // Re-check in case status changed between the outer check and listener registration
+              const current = store.get(task_id);
+              if (current && current.status !== "in_progress") { unsubOk(); unsubFail(); cleanup(); }
+              signal?.addEventListener("abort", () => { unsubOk(); unsubFail(); cleanup(); }, { once: true });
+            });
+          }
+          const updated = store.get(task_id) ?? task;
+          return textResult(`Task #${task_id} [${updated.status}] — subagent ${task.metadata.agentId}`);
+        }
         throw new Error(`No background process for task ${task_id}`);
       }
 
@@ -671,6 +772,22 @@ Set up task dependencies:
 
       const stopped = await tracker.stop(taskId);
       if (!stopped) {
+        // No shell process — check if this is a subagent task
+        // Support both task IDs and agent IDs
+        let resolvedId = taskId;
+        if (!store.get(resolvedId)) {
+          for (const [agentId, tId] of agentTaskMap) {
+            if (agentId === taskId || agentId.startsWith(taskId)) { resolvedId = tId; break; }
+          }
+        }
+        const task = store.get(resolvedId);
+        if (task?.metadata?.agentId && task.status === "in_progress") {
+          store.update(taskId, { status: "completed" });
+          await stopSubagent(task.metadata.agentId);
+          widget.setActiveTask(taskId, false);
+          widget.update();
+          return textResult(`Task #${taskId} stopped successfully`);
+        }
         throw new Error(`No running background process for task ${taskId}`);
       }
 
@@ -688,7 +805,7 @@ Set up task dependencies:
   pi.registerTool({
     name: "TaskExecute",
     label: "TaskExecute",
-    description: `Execute one or more tasks as subagents. Requires @tintinweb/pi-subagents extension.
+    description: `Execute one or more tasks as subagents.
 
 ## When to Use This Tool
 
@@ -702,6 +819,9 @@ Set up task dependencies:
 - **additional_context**: Extra context appended to each agent's prompt
 - **model**: Model override for agents (e.g., "sonnet", "haiku")
 - **max_turns**: Maximum turns per agent`,
+    promptGuidelines: [
+      "Never use the Agent tool for tasks launched via TaskExecute — agents are already running.",
+    ],
     parameters: Type.Object({
       task_ids: Type.Array(Type.String(), { description: "Task IDs to execute as subagents" }),
       additional_context: Type.Optional(Type.String({ description: "Extra context for agent prompts" })),
@@ -712,8 +832,8 @@ Set up task dependencies:
     async execute(_toolCallId, params, _signal, _onUpdate, _ctx) {
       if (!subagentsAvailable) {
         return textResult(
-          "TaskExecute requires the @tintinweb/pi-subagents extension to be loaded. " +
-          "Install and enable it, then try again."
+          "Subagent execution is currently unavailable. " +
+          "Ensure the @tintinweb/pi-subagents extension is loaded and try again."
         );
       }
 
@@ -759,6 +879,7 @@ Set up task dependencies:
           widget.setActiveTask(taskId);
           launched.push(`#${taskId} → agent ${agentId}`);
         } catch (err: any) {
+          debug(`spawn:error task=#${taskId}`, err);
           store.update(taskId, { status: "pending" });
           results.push(`#${taskId}: spawn failed — ${err.message}`);
         }
@@ -774,7 +895,12 @@ Set up task dependencies:
       widget.update();
 
       const lines: string[] = [];
-      if (launched.length > 0) lines.push(`Launched ${launched.length} agent(s):\n${launched.join("\n")}`);
+      if (launched.length > 0) {
+        lines.push(
+          `Launched ${launched.length} agent(s):\n${launched.join("\n")}\n` +
+          `Use TaskOutput to check progress. Do not spawn additional agents for these tasks.`
+        );
+      }
       if (results.length > 0) lines.push(`Skipped:\n${results.join("\n")}`);
       if (lines.length === 0) lines.push("No tasks to execute.");
 

test/subagent-integration.test.ts

@@ -76,6 +76,7 @@ function mockCtx() {
     ui: {
       setWidget: vi.fn(),
       setStatus: vi.fn(),
+      notify: vi.fn(),
     },
   };
 }
@@ -83,14 +84,15 @@ function mockCtx() {
 // ---- Mock subagents extension (RPC responders) ----
 
 /** Simulates the @tintinweb/pi-subagents extension: responds to ping + spawn RPCs and emits ready. */
-function installSubagentsMock(pi: { events: { on: Function; emit: Function } }) {
+function installSubagentsMock(pi: { events: { on: Function; emit: Function } }, opts?: { spawnError?: string }) {
   let idCounter = 0;
   const spawned: Array<{ id: string; type: string; prompt: string; options: any }> = [];
+  const stopped: string[] = [];
 
   // Respond to ping — reply on scoped channel
   const unsubPing = pi.events.on("subagents:rpc:ping", (data: unknown) => {
     const { requestId } = data as { requestId: string };
-    pi.events.emit(`subagents:rpc:ping:reply:${requestId}`, {});
+    pi.events.emit(`subagents:rpc:ping:reply:${requestId}`, { success: true, data: { version: 2 } });
   });
 
   // Respond to spawn — reply on scoped channel
@@ -98,9 +100,25 @@ function installSubagentsMock(pi: { events: { on: Function; emit: Function } })
     const { requestId, type, prompt, options } = data as {
       requestId: string; type: string; prompt: string; options?: any;
     };
+    if (opts?.spawnError) {
+      pi.events.emit(`subagents:rpc:spawn:reply:${requestId}`, { success: false, error: opts.spawnError });
+      return;
+    }
     const id = `agent-${++idCounter}`;
     spawned.push({ id, type, prompt, options });
-    pi.events.emit(`subagents:rpc:spawn:reply:${requestId}`, { id });
+    pi.events.emit(`subagents:rpc:spawn:reply:${requestId}`, { success: true, data: { id } });
+  });
+
+  // Respond to stop — reply on scoped channel
+  const unsubStop = pi.events.on("subagents:rpc:stop", (data: unknown) => {
+    const { requestId, agentId } = data as { requestId: string; agentId: string };
+    const known = spawned.some(s => s.id === agentId);
+    if (known) {
+      stopped.push(agentId);
+      pi.events.emit(`subagents:rpc:stop:reply:${requestId}`, { success: true });
+    } else {
+      pi.events.emit(`subagents:rpc:stop:reply:${requestId}`, { success: false, error: "Agent not found" });
+    }
   });
 
   // Broadcast readiness
@@ -108,7 +126,8 @@ function installSubagentsMock(pi: { events: { on: Function; emit: Function } })
 
   return {
     spawned,
-    unsub() { unsubPing(); unsubSpawn(); },
+    stopped,
+    unsub() { unsubPing(); unsubSpawn(); unsubStop(); },
   };
 }
 
@@ -556,12 +575,10 @@ describe("RPC protocol correctness", () => {
 
   it("spawn RPC rejects on timeout when no responder exists", async () => {
     const mock = mockPi();
+    // Install ping handler (for version check) but no spawn handler
+    installVersionedMock(mock.pi, 2);
     initExtension(mock.pi as any);
 
-    // Emit ready AFTER init so the listener is registered — marks subagents
-    // as available, but there's no spawn handler installed
-    mock.pi.events.emit("subagents:ready", {});
-
     await mock.executeTool("TaskCreate", {
       subject: "Timeout test",
       description: "desc",
@@ -603,6 +620,176 @@ describe("RPC protocol correctness", () => {
 
     rpc.unsub();
   });
+
+  it("spawn RPC rejects with error message from server", async () => {
+    const mock = mockPi();
+    installSubagentsMock(mock.pi, { spawnError: "No active session" });
+    initExtension(mock.pi as any);
+
+    await mock.executeTool("TaskCreate", {
+      subject: "Err test",
+      description: "desc",
+      agentType: "general-purpose",
+    });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(result.content[0].text).toContain("No active session");
+  });
+
+  it("stop RPC resolves on success", async () => {
+    const mock = mockPi();
+    const rpc = installSubagentsMock(mock.pi);
+    initExtension(mock.pi as any);
+
+    // Spawn a task so we have an agent to stop
+    await mock.executeTool("TaskCreate", {
+      subject: "Stoppable",
+      description: "desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(rpc.spawned).toHaveLength(1);
+
+    const result = await mock.executeTool("TaskStop", { task_id: "1" });
+    expect(result.content[0].text).toContain("stopped successfully");
+    expect(rpc.stopped).toContain("agent-1");
+
+    rpc.unsub();
+  });
+
+  it("stop RPC returns false on error (agent not found) without throwing", async () => {
+    const mock = mockPi();
+    const rpc = installSubagentsMock(mock.pi);
+    initExtension(mock.pi as any);
+
+    // Create and execute a task, then simulate agent already gone
+    await mock.executeTool("TaskCreate", {
+      subject: "Ghost",
+      description: "desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+
+    // Clear spawned list so the mock's stop handler won't find the agent
+    rpc.spawned.length = 0;
+
+    // TaskStop should still succeed (stopSubagent catches the error)
+    const result = await mock.executeTool("TaskStop", { task_id: "1" });
+    expect(result.content[0].text).toContain("stopped successfully");
+
+    rpc.unsub();
+  });
+
+  it("stop RPC returns false on timeout without throwing", async () => {
+    const mock = mockPi();
+    initExtension(mock.pi as any);
+
+    // Mark subagents as available via ready broadcast, but no stop handler installed
+    mock.pi.events.emit("subagents:ready", {});
+
+    await mock.executeTool("TaskCreate", {
+      subject: "Timeout stop",
+      description: "desc",
+      agentType: "general-purpose",
+    });
+    // Manually set task as in_progress with an agentId (no spawn handler)
+    await mock.executeTool("TaskUpdate", {
+      taskId: "1",
+      status: "in_progress",
+      metadata: { agentType: "general-purpose", agentId: "ghost-agent" },
+    });
+
+    vi.useFakeTimers();
+    const stopPromise = mock.executeTool("TaskStop", { task_id: "1" });
+    await vi.advanceTimersByTimeAsync(11000);
+
+    // Should resolve (not throw) — stopSubagent catches timeout
+    const result = await stopPromise;
+    expect(result.content[0].text).toContain("stopped successfully");
+
+    vi.useRealTimers();
+  });
+});
+
+/** Install a ping-only mock with a specific protocol version (or no version for v1). */
+function installVersionedMock(pi: { events: { on: Function; emit: Function } }, version?: number) {
+  const unsubPing = pi.events.on("subagents:rpc:ping", (data: unknown) => {
+    const { requestId } = data as { requestId: string };
+    if (version !== undefined) {
+      pi.events.emit(`subagents:rpc:ping:reply:${requestId}`, { success: true, data: { version } });
+    } else {
+      // v1 handler — no envelope, no version
+      pi.events.emit(`subagents:rpc:ping:reply:${requestId}`, {});
+    }
+  });
+  pi.events.emit("subagents:ready", {});
+  return { unsub() { unsubPing(); } };
+}
+
+describe("Protocol version mismatch", () => {
+  it("matching version — no warning", async () => {
+    const mock = mockPi();
+    installVersionedMock(mock.pi, 2);
+    initExtension(mock.pi as any);
+
+    // No warning on before_agent_start
+    const ctx = mockCtx();
+    await mock.fireLifecycle("before_agent_start", {}, ctx);
+    expect(ctx.ui.notify).not.toHaveBeenCalled();
+  });
+
+  it("old handler (no version) — warns about pi-subagents", async () => {
+    const mock = mockPi();
+    installVersionedMock(mock.pi);  // no version = v1
+    initExtension(mock.pi as any);
+
+    const ctx = mockCtx();
+    await mock.fireLifecycle("before_agent_start", {}, ctx);
+    expect(ctx.ui.notify).toHaveBeenCalledWith(
+      expect.stringContaining("pi-subagents is outdated"),
+      "warning",
+    );
+  });
+
+  it("handler ahead (v3) — warns about pi-tasks", async () => {
+    const mock = mockPi();
+    installVersionedMock(mock.pi, 3);
+    initExtension(mock.pi as any);
+
+    const ctx = mockCtx();
+    await mock.fireLifecycle("before_agent_start", {}, ctx);
+    expect(ctx.ui.notify).toHaveBeenCalledWith(
+      expect.stringContaining("pi-tasks is outdated"),
+      "warning",
+    );
+  });
+
+  it("handler behind (v1) — warns about pi-subagents", async () => {
+    const mock = mockPi();
+    installVersionedMock(mock.pi, 1);
+    initExtension(mock.pi as any);
+
+    const ctx = mockCtx();
+    await mock.fireLifecycle("before_agent_start", {}, ctx);
+    expect(ctx.ui.notify).toHaveBeenCalledWith(
+      expect.stringContaining("pi-subagents is outdated"),
+      "warning",
+    );
+  });
+
+  it("warning shown only once", async () => {
+    const mock = mockPi();
+    installVersionedMock(mock.pi);  // v1 — triggers warning
+    initExtension(mock.pi as any);
+
+    const ctx1 = mockCtx();
+    await mock.fireLifecycle("before_agent_start", {}, ctx1);
+    expect(ctx1.ui.notify).toHaveBeenCalledOnce();
+
+    const ctx2 = mockCtx();
+    await mock.fireLifecycle("before_agent_start", {}, ctx2);
+    expect(ctx2.ui.notify).not.toHaveBeenCalled();
+  });
 });
 
 describe("Widget agent ID display", () => {