diff --git a/CHANGELOG.md b/CHANGELOG.md
index b30a9ea..034a5f2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,23 @@ 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).
 
+## [0.2.0] - 2026-03-12
+
+### Added
+- **`TaskExecute` tool** — execute tasks as background subagents via pi-chonky-subagents. Tasks with `agentType` metadata are spawned as independent agents; validates status, dependencies, and agent type before launching.
+- **`agentType` parameter on `TaskCreate`** — opt-in field (e.g., `"general-purpose"`, `"Explore"`) that marks tasks for subagent execution.
+- **Auto-cascade** — when enabled via `/tasks` → Settings, completed agent tasks automatically trigger execution of their unblocked dependents, flowing through the task DAG like a build system. Off by default.
+- **Subagent completion listener** — listens to `subagents:completed` and `subagents:failed` events to automatically update task status. Failed tasks revert to `pending` with error stored in metadata.
+- **READY tags in system prompt** — pending tasks with `agentType` and all dependencies completed are marked `[READY — use TaskExecute to start]` in the system prompt.
+- **Agent ID in widget** — in-progress tasks backed by subagents show the agent ID (e.g., `✳ Writing tests (agent abc12)…`).
+- **Settings menu** — `/tasks` → Settings → toggle "Auto-execute tasks with agents".
+- **`SubagentBridge` type** — typed interface for the cross-extension Symbol.for bridge.
+
+### Changed
+- `pi-chonky-subagents` global registry now exposes `spawn()` and `getRecord()` in addition to `waitForAll()` and `hasRunning()`.
+- `pi-chonky-subagents` emits lifecycle events on `pi.events`: `subagents:created`, `subagents:started`, `subagents:completed`, `subagents:failed`, `subagents:steered`.
+- `AgentManager` accepts an optional `onStart` callback, fired when an agent transitions to running (including from queue).
+
 ## [0.1.0] - 2026-03-12
 
 Initial release — Claude Code-style task tracking and coordination for pi.
@@ -24,4 +41,5 @@ Initial release — Claude Code-style task tracking and coordination for pi.
 - **Background process tracker** — output buffering (stdout + stderr), waiter notification, graceful stop with timeout escalation (SIGTERM → 5s → SIGKILL).
 - **78 unit tests** — task store CRUD, dependencies, warnings, file persistence; widget rendering, icons, spinners, token/duration formatting; process tracker lifecycle.
 
+[0.2.0]: https://github.com/tintinweb/pi-tasks/releases/tag/v0.2.0
 [0.1.0]: https://github.com/tintinweb/pi-tasks/releases/tag/v0.1.0
diff --git a/README.md b/README.md
index 581a616..afb0304 100644
--- a/README.md
+++ b/README.md
@@ -12,7 +12,7 @@ https://github.com/user-attachments/assets/86b09bd1-6882-4b0c-be20-ea866dd44b6a
 
 ## Features
 
-- **6 LLM-callable tools** — `TaskCreate`, `TaskList`, `TaskGet`, `TaskUpdate`, `TaskOutput`, `TaskStop` — matching Claude Code's exact tool specs and descriptions
+- **7 LLM-callable tools** — `TaskCreate`, `TaskList`, `TaskGet`, `TaskUpdate`, `TaskOutput`, `TaskStop`, `TaskExecute` — matching Claude Code's exact tool specs and descriptions
 - **Persistent widget** — live task list above the editor with `✔`/`◼`/`◻` status icons, strikethrough for completed tasks, star spinner (`✳✽`) for active tasks with elapsed time and token counts
 - **System-reminder injection** — periodic `<system-reminder>` nudges appended to tool results when task tools haven't been used recently (matches Claude Code's behavior)
 - **Task state persistence** — current task state injected into system prompt on every agent loop, surviving context compaction
@@ -21,6 +21,7 @@ https://github.com/user-attachments/assets/86b09bd1-6882-4b0c-be20-ea866dd44b6a
 - **Shared task lists** — multiple pi sessions can share a file-backed task list for agent team coordination
 - **File locking** — concurrent access is safe when multiple sessions share a task list
 - **Background process tracking** — track spawned processes with output buffering, blocking wait, and graceful stop
+- **Subagent integration** — tasks with `agentType` can be executed as subagents via `TaskExecute` (requires [pi-chonky-subagents](https://github.com/tintinweb/pi-subagents)). Auto-cascade mode flows through the task DAG automatically when enabled.
 
 ## Install
 
@@ -64,6 +65,7 @@ Create a structured task. Used proactively for complex multi-step work.
 | `subject` | string | yes | Brief imperative title |
 | `description` | string | yes | Detailed context and acceptance criteria |
 | `activeForm` | string | no | Present continuous form for spinner (e.g., "Running tests") |
+| `agentType` | string | no | Agent type for subagent execution (e.g., `"general-purpose"`, `"Explore"`) |
 | `metadata` | object | no | Arbitrary key-value pairs |
 
 ```
@@ -143,6 +145,21 @@ Stop a running background task process. Sends SIGTERM, waits 5 seconds, then SIG
 |-----------|------|-------------|
 | `task_id` | string | Task ID to stop |
 
+### `TaskExecute`
+
+Execute one or more tasks as background subagents. Requires [pi-chonky-subagents](https://github.com/tintinweb/pi-subagents).
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `task_ids` | string[] | Task IDs to execute (required) |
+| `additional_context` | string | Extra context appended to each agent's prompt |
+| `model` | string | Model override (e.g., `"sonnet"`, `"haiku"`) |
+| `max_turns` | number | Max turns per agent |
+
+Tasks must be `pending`, have `agentType` set, and all `blockedBy` dependencies `completed`. Each task spawns as an independent background subagent.
+
+With **auto-cascade** enabled (via `/tasks` → Settings), completed tasks automatically trigger execution of their unblocked dependents — flowing through the DAG like a build system.
+
 ## Task Lifecycle
 
 ```
@@ -180,19 +197,21 @@ Interactive menu:
 Tasks
 ├─ View all tasks (4)
 ├─ Create task
+├─ Settings
 └─ Clear completed (1)
 ```
 
 - **View all tasks** — select a task to see details and take actions (start, complete, delete)
 - **Create task** — input prompts for subject and description
+- **Settings** — toggle auto-cascade (auto-execute unblocked agent tasks on completion)
 - **Clear completed** — remove all completed tasks
 
 ## Architecture
 
 ```
 src/
-├── index.ts            # Extension entry: 6 tools + /tasks command + widget
-├── types.ts            # Task, TaskStatus, BackgroundProcess types
+├── index.ts            # Extension entry: 7 tools + /tasks command + widget + subagent integration
+├── types.ts            # Task, TaskStatus, BackgroundProcess, SubagentBridge types
 ├── task-store.ts       # File-backed store with CRUD, dependencies, locking
 ├── process-tracker.ts  # Background process output buffering and stop
 └── ui/
diff --git a/package.json b/package.json
index 7eddeed..630c890 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@tintinweb/pi-tasks",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "A pi extension that brings Claude Code-style task tracking and coordination to pi.",
   "author": "tintinweb",
   "license": "MIT",
diff --git a/src/index.ts b/src/index.ts
index 0853afd..0b3c39a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -8,6 +8,7 @@
  *   TaskUpdate   — Update task fields, status, dependencies
  *   TaskOutput   — Get output from a background task process
  *   TaskStop     — Stop a running background task process
+ *   TaskExecute  — Execute tasks as subagents (requires pi-chonky-subagents)
  *
  * Commands:
  *   /tasks       — Interactive task management menu
@@ -18,6 +19,7 @@ import { Type } from "@sinclair/typebox";
 import { TaskStore } from "./task-store.js";
 import { ProcessTracker } from "./process-tracker.js";
 import { TaskWidget, type UICtx } from "./ui/task-widget.js";
+import type { SubagentBridge } from "./types.js";
 
 // ---- Helpers ----
 
@@ -26,7 +28,7 @@ function textResult(msg: string) {
 }
 
 /** Task tool names — used to detect task tool usage for reminder suppression. */
-const TASK_TOOL_NAMES = new Set(["TaskCreate", "TaskList", "TaskGet", "TaskUpdate", "TaskOutput", "TaskStop"]);
+const TASK_TOOL_NAMES = new Set(["TaskCreate", "TaskList", "TaskGet", "TaskUpdate", "TaskOutput", "TaskStop", "TaskExecute"]);
 
 /** How many turns without task tool usage before injecting a reminder. */
 const REMINDER_INTERVAL = 4;
@@ -42,6 +44,79 @@ export default function (pi: ExtensionAPI) {
   const tracker = new ProcessTracker();
   const widget = new TaskWidget(store);
 
+  // ── Subagent integration state ──
+  let autoCascadeEnabled = false;
+  /** Latest ExtensionContext — refreshed on every tool execution so cascade always has a valid one. */
+  let latestCtx: ExtensionContext | undefined;
+  /** Cascade config — set by TaskExecute, consumed by completion listener. */
+  let cascadeConfig: { additionalContext?: string; model?: string; maxTurns?: number } | undefined;
+
+  /** Get the subagent bridge from the global registry (returns undefined if pi-chonky-subagents not loaded). */
+  function getSubagentBridge(): SubagentBridge | undefined {
+    const key = Symbol.for("pi-subagents:manager");
+    return (globalThis as any)[key] as SubagentBridge | undefined;
+  }
+
+  /** 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${task.description}`;
+    if (additionalContext) prompt += `\n\n${additionalContext}`;
+    prompt += `\n\nComplete this task fully. Do not attempt to manage tasks yourself.`;
+    return prompt;
+  }
+
+  // ── Subagent completion listener ──
+  // Listens for subagent lifecycle events to update task status and optionally cascade.
+
+  // Success → mark task completed, cascade if enabled
+  pi.events.on("subagents:completed", (data) => {
+    const { id } = data as { id: string };
+    const task = store.list().find(t => t.metadata?.agentId === id);
+    if (!task) return;
+
+    store.update(task.id, { status: "completed" });
+    widget.setActiveTask(task.id, false);
+
+    // Auto-cascade: find unblocked dependents with agentType
+    if (autoCascadeEnabled && cascadeConfig && latestCtx) {
+      const bridge = getSubagentBridge();
+      if (bridge) {
+        const unblocked = store.list().filter(t =>
+          t.status === "pending" &&
+          t.metadata?.agentType &&
+          t.blockedBy.includes(task.id) &&
+          t.blockedBy.every(depId => store.get(depId)?.status === "completed")
+        );
+        for (const next of unblocked) {
+          store.update(next.id, { status: "in_progress" });
+          const prompt = buildTaskPrompt(next, cascadeConfig.additionalContext);
+          const agentId = bridge.spawn(pi, latestCtx,
+            next.metadata.agentType, prompt, {
+              description: next.subject,
+              isBackground: true,
+              maxTurns: cascadeConfig.maxTurns,
+            });
+          store.update(next.id, { owner: agentId, metadata: { ...next.metadata, agentId } });
+          widget.setActiveTask(next.id);
+        }
+      }
+    }
+    widget.update();
+  });
+
+  // Failure → store error, revert to pending, don't cascade (branch stops)
+  pi.events.on("subagents:failed", (data) => {
+    const { id, error, status } = data as { id: string; error?: string; status: string };
+    const task = store.list().find(t => t.metadata?.agentId === id);
+    if (!task) return;
+    store.update(task.id, {
+      status: "pending",
+      metadata: { ...task.metadata, lastError: error || status },
+    });
+    widget.setActiveTask(task.id, false);
+    widget.update();
+  });
+
   // ── Turn tracking for system-reminder injection ──
   let currentTurn = 0;
   let lastTaskToolUseTurn = 0;
@@ -107,6 +182,16 @@ export default function (pi: ExtensionAPI) {
           line += ` [blocked by ${openBlockers.map(id => "#" + id).join(", ")}]`;
         }
       }
+      // Mark agent-typed pending tasks with all deps completed as READY
+      if (t.status === "pending" && t.metadata?.agentType) {
+        const allDepsCompleted = t.blockedBy.length === 0 || t.blockedBy.every(bid => {
+          const blocker = store.get(bid);
+          return blocker && blocker.status === "completed";
+        });
+        if (allDepsCompleted) {
+          line += ` [READY — use TaskExecute to start]`;
+        }
+      }
       return line;
     }).join("\n");
 
@@ -115,8 +200,9 @@ export default function (pi: ExtensionAPI) {
     };
   });
 
-  // Grab UI context from first tool execution
+  // Grab UI + extension context from every tool execution
   pi.on("tool_execution_start", async (_event, ctx) => {
+    latestCtx = ctx;
     widget.setUICtx(ctx.ui as UICtx);
     widget.update();
   });
@@ -167,7 +253,8 @@ All tasks are created with status \`pending\`.
 - Create tasks with clear, specific subjects that describe the outcome
 - Include enough detail in the description for another agent to understand and complete the task
 - After creating tasks, use TaskUpdate to set up dependencies (blocks/blockedBy) if needed
-- Check TaskList first to avoid creating duplicate tasks`,
+- Check TaskList first to avoid creating duplicate tasks
+- Include \`agentType\` (e.g., "general-purpose", "Explore") to mark tasks for subagent execution via TaskExecute`,
     promptGuidelines: [
       "When working on complex multi-step tasks, use TaskCreate to track progress and TaskUpdate to update status.",
       "Mark tasks as in_progress before starting work and completed when done.",
@@ -177,11 +264,14 @@ All tasks are created with status \`pending\`.
       subject: Type.String({ description: "A brief title for the task" }),
       description: Type.String({ description: "A detailed description of what needs to be done" }),
       activeForm: Type.Optional(Type.String({ description: "Present continuous form shown in spinner when in_progress (e.g., 'Running tests')" })),
+      agentType: Type.Optional(Type.String({ description: "Agent type for subagent execution (e.g., 'general-purpose', 'Explore'). Tasks with agentType can be started via TaskExecute." })),
       metadata: Type.Optional(Type.Record(Type.String(), Type.Any(), { description: "Arbitrary metadata to attach to the task" })),
     }),
 
     execute(_toolCallId, params, _signal, _onUpdate, _ctx) {
-      const task = store.create(params.subject, params.description, params.activeForm, params.metadata);
+      const meta = params.metadata ?? {};
+      if (params.agentType) meta.agentType = params.agentType;
+      const task = store.create(params.subject, params.description, params.activeForm, Object.keys(meta).length > 0 ? meta : undefined);
       widget.update();
       return Promise.resolve(textResult(`Task #${task.id} created successfully: ${task.subject}`));
     },
@@ -511,6 +601,103 @@ Set up task dependencies:
     },
   });
 
+  // ──────────────────────────────────────────────────
+  // Tool 7: TaskExecute
+  // ──────────────────────────────────────────────────
+
+  pi.registerTool({
+    name: "TaskExecute",
+    label: "TaskExecute",
+    description: `Execute one or more tasks as subagents. Requires pi-chonky-subagents extension.
+
+## When to Use This Tool
+
+- To start execution of tasks that have \`agentType\` set (created via TaskCreate with agentType parameter)
+- Tasks must be \`pending\` with all blockedBy dependencies \`completed\`
+- Each task runs as an independent background subagent
+
+## Parameters
+
+- **task_ids**: Array of task IDs to execute
+- **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`,
+    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" })),
+      model: Type.Optional(Type.String({ description: "Model override for agents" })),
+      max_turns: Type.Optional(Type.Number({ description: "Max turns per agent", minimum: 1 })),
+    }),
+
+    execute(_toolCallId, params, _signal, _onUpdate, ctx) {
+      const bridge = getSubagentBridge();
+      if (!bridge) {
+        return Promise.resolve(textResult(
+          "TaskExecute requires the pi-chonky-subagents extension to be loaded. " +
+          "Install and enable it, then try again."
+        ));
+      }
+
+      const results: string[] = [];
+      const launched: string[] = [];
+
+      for (const taskId of params.task_ids) {
+        const task = store.get(taskId);
+        if (!task) {
+          results.push(`#${taskId}: not found`);
+          continue;
+        }
+        if (task.status !== "pending") {
+          results.push(`#${taskId}: not pending (status: ${task.status})`);
+          continue;
+        }
+        if (!task.metadata?.agentType) {
+          results.push(`#${taskId}: no agentType set — create with agentType parameter or update metadata`);
+          continue;
+        }
+
+        // Check all blockers are completed
+        const openBlockers = task.blockedBy.filter(bid => {
+          const blocker = store.get(bid);
+          return !blocker || blocker.status !== "completed";
+        });
+        if (openBlockers.length > 0) {
+          results.push(`#${taskId}: blocked by ${openBlockers.map(id => "#" + id).join(", ")}`);
+          continue;
+        }
+
+        // Mark in_progress and spawn agent
+        store.update(taskId, { status: "in_progress" });
+        const prompt = buildTaskPrompt(task, params.additional_context);
+        const agentId = bridge.spawn(pi, ctx, task.metadata.agentType, prompt, {
+          description: task.subject,
+          isBackground: true,
+          maxTurns: params.max_turns,
+        });
+
+        store.update(taskId, { owner: agentId, metadata: { ...task.metadata, agentId } });
+        widget.setActiveTask(taskId);
+        launched.push(`#${taskId} → agent ${agentId}`);
+      }
+
+      // Save cascade config for the completion listener
+      cascadeConfig = {
+        additionalContext: params.additional_context,
+        model: params.model,
+        maxTurns: params.max_turns,
+      };
+
+      widget.update();
+
+      const lines: string[] = [];
+      if (launched.length > 0) lines.push(`Launched ${launched.length} agent(s):\n${launched.join("\n")}`);
+      if (results.length > 0) lines.push(`Skipped:\n${results.join("\n")}`);
+      if (lines.length === 0) lines.push("No tasks to execute.");
+
+      return Promise.resolve(textResult(lines.join("\n\n")));
+    },
+  });
+
   // ──────────────────────────────────────────────────
   // /tasks command
   // ──────────────────────────────────────────────────
@@ -528,6 +715,7 @@ Set up task dependencies:
         const choices: string[] = [
           `View all tasks (${taskCount})`,
           "Create task",
+          "Settings",
         ];
         if (completedCount > 0) choices.push(`Clear completed (${completedCount})`);
 
@@ -538,6 +726,8 @@ Set up task dependencies:
           await viewTasks();
         } else if (choice === "Create task") {
           await createTask();
+        } else if (choice === "Settings") {
+          await settingsMenu();
         } else if (choice.startsWith("Clear")) {
           store.clearCompleted();
           widget.update();
@@ -611,6 +801,18 @@ Set up task dependencies:
         return viewTasks();
       };
 
+      const settingsMenu = async (): Promise<void> => {
+        const cascadeLabel = `Auto-execute tasks with agents: ${autoCascadeEnabled ? "ON" : "OFF"}`;
+        const choices = [cascadeLabel, "← Back"];
+        const selected = await ui.select("Settings", choices);
+        if (!selected || selected === "← Back") return mainMenu();
+        if (selected === cascadeLabel) {
+          autoCascadeEnabled = !autoCascadeEnabled;
+          return settingsMenu();
+        }
+        return mainMenu();
+      };
+
       const createTask = async (): Promise<void> => {
         const subject = await ui.input("Task subject");
         if (!subject) return mainMenu();
diff --git a/src/types.ts b/src/types.ts
index 6ba2cf3..fac1504 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -24,6 +24,14 @@ export interface TaskStoreData {
   tasks: Task[];
 }
 
+/** Bridge to the pi-chonky-subagents extension via Symbol.for global registry. */
+export interface SubagentBridge {
+  waitForAll(): Promise<void>;
+  hasRunning(): boolean;
+  spawn(pi: any, ctx: any, type: string, prompt: string, options: any): string;
+  getRecord(id: string): any | undefined;
+}
+
 /** Background process associated with a task. */
 export interface BackgroundProcess {
   taskId: string;
diff --git a/src/ui/task-widget.ts b/src/ui/task-widget.ts
index 57de274..9083386 100644
--- a/src/ui/task-widget.ts
+++ b/src/ui/task-widget.ts
@@ -191,6 +191,8 @@ export class TaskWidget {
         let text: string;
         if (isActive) {
           const form = task.activeForm || task.subject;
+          const agentId = task.metadata?.agentId;
+          const agentLabel = agentId ? ` (agent ${agentId.slice(0, 5)})` : "";
           const m = this.metrics.get(task.id);
           let stats = "";
           if (m) {
@@ -202,11 +204,14 @@ export class TaskWidget {
               ? ` ${theme.fg("dim", `(${elapsed} · ${tokenParts.join(" ")})`)}`
               : ` ${theme.fg("dim", `(${elapsed})`)}`;
           }
-          text = `  ${icon} ${theme.fg("accent", form + "…")}${stats}`;
+          text = `  ${icon} ${theme.fg("accent", form + agentLabel + "…")}${stats}`;
         } else if (task.status === "completed") {
           text = `  ${theme.fg("dim", icon)} ${theme.fg("dim", theme.strikethrough(task.subject))}`;
         } else {
-          text = `  ${icon} ${task.subject}`;
+          const agentSuffix = task.status === "in_progress" && task.metadata?.agentId
+            ? theme.fg("dim", ` (agent ${task.metadata.agentId.slice(0, 5)})`)
+            : "";
+          text = `  ${icon} ${task.subject}${agentSuffix}`;
         }
 
         lines.push(truncate(text + suffix));
diff --git a/test/subagent-integration.test.ts b/test/subagent-integration.test.ts
new file mode 100644
index 0000000..ef2d073
--- /dev/null
+++ b/test/subagent-integration.test.ts
@@ -0,0 +1,584 @@
+/**
+ * Tests for task-subagent integration: TaskExecute tool, completion listener,
+ * auto-cascade, and widget agent ID display.
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { TaskStore } from "../src/task-store.js";
+import { TaskWidget, type UICtx, type Theme } from "../src/ui/task-widget.js";
+import type { SubagentBridge } from "../src/types.js";
+import initExtension from "../src/index.js";
+
+// ---- Mock pi ----
+
+/** Minimal mock of ExtensionAPI with events, tool capture, and event hooks. */
+function mockPi() {
+  const tools = new Map<string, any>();
+  const commands = new Map<string, any>();
+  const eventHandlers = new Map<string, ((data: unknown) => void)[]>();
+  const lifecycleHandlers = new Map<string, ((...args: any[]) => any)[]>();
+
+  const pi = {
+    registerTool(def: any) { tools.set(def.name, def); },
+    registerCommand(name: string, def: any) { commands.set(name, def); },
+    on(event: string, handler: any) {
+      if (!lifecycleHandlers.has(event)) lifecycleHandlers.set(event, []);
+      lifecycleHandlers.get(event)!.push(handler);
+    },
+    events: {
+      emit(channel: string, data: unknown) {
+        for (const h of eventHandlers.get(channel) ?? []) h(data);
+      },
+      on(channel: string, handler: (data: unknown) => void) {
+        if (!eventHandlers.has(channel)) eventHandlers.set(channel, []);
+        eventHandlers.get(channel)!.push(handler);
+        return () => {
+          const arr = eventHandlers.get(channel);
+          if (arr) eventHandlers.set(channel, arr.filter(h => h !== handler));
+        };
+      },
+    },
+    sendUserMessage: vi.fn(),
+  };
+
+  return {
+    pi,
+    tools,
+    commands,
+    /** Execute a registered tool by name. */
+    async executeTool(name: string, params: any, ctx?: any) {
+      const tool = tools.get(name);
+      if (!tool) throw new Error(`Tool ${name} not registered`);
+      return tool.execute("call-1", params, undefined, undefined, ctx ?? mockCtx());
+    },
+    /** Fire lifecycle event handlers (turn_start, tool_result, etc.) */
+    async fireLifecycle(event: string, ...args: any[]) {
+      for (const h of lifecycleHandlers.get(event) ?? []) {
+        await h(...args);
+      }
+    },
+    /** Emit an event on pi.events (simulates subagent extension). */
+    emitEvent(channel: string, data: unknown) {
+      pi.events.emit(channel, data);
+    },
+  };
+}
+
+/** Minimal mock ExtensionContext. */
+function mockCtx() {
+  return {
+    model: { id: "test-model", name: "Test" },
+    modelRegistry: {},
+    ui: {
+      setWidget: vi.fn(),
+      setStatus: vi.fn(),
+    },
+  };
+}
+
+// ---- Mock subagent bridge ----
+
+function mockBridge(): SubagentBridge & { spawned: Array<{ type: string; prompt: string; options: any }> } {
+  let idCounter = 0;
+  const spawned: Array<{ id: string; type: string; prompt: string; options: any }> = [];
+
+  return {
+    spawned,
+    waitForAll: async () => {},
+    hasRunning: () => false,
+    spawn(_pi: any, _ctx: any, type: string, prompt: string, options: any) {
+      const id = `agent-${++idCounter}`;
+      spawned.push({ id, type, prompt, options });
+      return id;
+    },
+    getRecord(id: string) {
+      return spawned.find(s => s.id === id) ? { id, status: "running" } : undefined;
+    },
+  };
+}
+
+/** Install/remove a mock bridge on the global registry. */
+function installBridge(bridge: SubagentBridge) {
+  const key = Symbol.for("pi-subagents:manager");
+  (globalThis as any)[key] = bridge;
+  return () => { delete (globalThis as any)[key]; };
+}
+
+// ---- Tests ----
+
+describe("TaskExecute", () => {
+  let mock: ReturnType<typeof mockPi>;
+  let bridge: ReturnType<typeof mockBridge>;
+  let removeBridge: () => void;
+
+  beforeEach(() => {
+    mock = mockPi();
+    initExtension(mock.pi as any);
+    bridge = mockBridge();
+    removeBridge = installBridge(bridge);
+  });
+
+  afterEach(() => {
+    removeBridge();
+  });
+
+  it("is registered as a tool", () => {
+    expect(mock.tools.has("TaskExecute")).toBe(true);
+  });
+
+  it("returns error when subagent bridge is not loaded", async () => {
+    removeBridge();
+    // Create a task with agentType
+    await mock.executeTool("TaskCreate", {
+      subject: "Test task",
+      description: "Do something",
+      agentType: "general-purpose",
+    });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(result.content[0].text).toContain("requires the pi-chonky-subagents extension");
+  });
+
+  it("rejects non-existent tasks", async () => {
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["999"] });
+    expect(result.content[0].text).toContain("#999: not found");
+  });
+
+  it("rejects tasks without agentType", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "No agent type",
+      description: "Plain task",
+    });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(result.content[0].text).toContain("#1: no agentType set");
+  });
+
+  it("rejects non-pending tasks", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Already started",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "1", status: "in_progress" });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(result.content[0].text).toContain("#1: not pending");
+  });
+
+  it("rejects tasks with unresolved blockers", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Blocker",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "Blocked",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "2", addBlockedBy: ["1"] });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["2"] });
+    expect(result.content[0].text).toContain("#2: blocked by #1");
+  });
+
+  it("spawns agent for valid task and updates metadata", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Run tests",
+      description: "Run the test suite",
+      agentType: "general-purpose",
+    });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(result.content[0].text).toContain("Launched 1 agent");
+    expect(result.content[0].text).toContain("#1 → agent agent-1");
+
+    // Verify the bridge was called
+    expect(bridge.spawned).toHaveLength(1);
+    expect(bridge.spawned[0].type).toBe("general-purpose");
+    expect(bridge.spawned[0].prompt).toContain("Run the test suite");
+    expect(bridge.spawned[0].options.isBackground).toBe(true);
+  });
+
+  it("passes additional_context and max_turns to spawned agents", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Explore codebase",
+      description: "Find all API endpoints",
+      agentType: "Explore",
+    });
+
+    await mock.executeTool("TaskExecute", {
+      task_ids: ["1"],
+      additional_context: "Focus on REST endpoints only",
+      max_turns: 10,
+    });
+
+    expect(bridge.spawned[0].prompt).toContain("Focus on REST endpoints only");
+    expect(bridge.spawned[0].options.maxTurns).toBe(10);
+  });
+
+  it("allows executing tasks whose blockers are all completed", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Blocker",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "Dependent",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "2", addBlockedBy: ["1"] });
+    await mock.executeTool("TaskUpdate", { taskId: "1", status: "completed" });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["2"] });
+    expect(result.content[0].text).toContain("Launched 1 agent");
+  });
+
+  it("handles mixed valid and invalid tasks in one call", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Valid",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "No agent type",
+      description: "Desc",
+    });
+
+    const result = await mock.executeTool("TaskExecute", { task_ids: ["1", "2", "999"] });
+    const text = result.content[0].text;
+    expect(text).toContain("Launched 1 agent");
+    expect(text).toContain("#2: no agentType set");
+    expect(text).toContain("#999: not found");
+  });
+});
+
+describe("Completion listener", () => {
+  let mock: ReturnType<typeof mockPi>;
+  let bridge: ReturnType<typeof mockBridge>;
+  let removeBridge: () => void;
+
+  beforeEach(() => {
+    mock = mockPi();
+    initExtension(mock.pi as any);
+    bridge = mockBridge();
+    removeBridge = installBridge(bridge);
+  });
+
+  afterEach(() => {
+    removeBridge();
+  });
+
+  it("marks task completed on subagents:completed event", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Agent task",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+
+    // Simulate agent completion
+    mock.emitEvent("subagents:completed", { id: "agent-1" });
+
+    const result = await mock.executeTool("TaskGet", { taskId: "1" });
+    expect(result.content[0].text).toContain("Status: completed");
+  });
+
+  it("reverts task to pending on subagents:failed event", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Failing task",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+
+    // Simulate agent failure
+    mock.emitEvent("subagents:failed", { id: "agent-1", error: "Out of turns", status: "error" });
+
+    const result = await mock.executeTool("TaskGet", { taskId: "1" });
+    expect(result.content[0].text).toContain("Status: pending");
+  });
+
+  it("ignores events for unknown agent IDs", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Unrelated",
+      description: "Desc",
+    });
+
+    // Should not throw or modify anything
+    mock.emitEvent("subagents:completed", { id: "unknown-agent" });
+    mock.emitEvent("subagents:failed", { id: "unknown-agent", error: "boom", status: "error" });
+
+    const result = await mock.executeTool("TaskGet", { taskId: "1" });
+    expect(result.content[0].text).toContain("Status: pending");
+  });
+});
+
+describe("Auto-cascade", () => {
+  let mock: ReturnType<typeof mockPi>;
+  let bridge: ReturnType<typeof mockBridge>;
+  let removeBridge: () => void;
+
+  beforeEach(() => {
+    mock = mockPi();
+    initExtension(mock.pi as any);
+    bridge = mockBridge();
+    removeBridge = installBridge(bridge);
+  });
+
+  afterEach(() => {
+    removeBridge();
+  });
+
+  /** Enable auto-cascade by toggling the setting via the /tasks command mock. */
+  function enableAutoCascade() {
+    // Auto-cascade is toggled via module-level state. Since we can't access it
+    // directly, we test that WITHOUT enabling it, cascade doesn't happen,
+    // and test the cascade logic indirectly via event flow.
+    // For a proper toggle test we'd need to invoke the /tasks command handler,
+    // but that requires a full UI mock. Instead we test the default (off) behavior.
+  }
+
+  it("does NOT cascade when auto-cascade is off (default)", async () => {
+    // Create A → B chain
+    await mock.executeTool("TaskCreate", {
+      subject: "Task A",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "Task B",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "2", addBlockedBy: ["1"] });
+
+    // Execute A
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    expect(bridge.spawned).toHaveLength(1);
+
+    // Complete A
+    mock.emitEvent("subagents:completed", { id: "agent-1" });
+
+    // B should NOT have been auto-started
+    expect(bridge.spawned).toHaveLength(1);
+
+    // B should still be pending
+    const result = await mock.executeTool("TaskGet", { taskId: "2" });
+    expect(result.content[0].text).toContain("Status: pending");
+  });
+
+  it("does NOT cascade on failure (branch stops)", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Task A",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "Task B",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "2", addBlockedBy: ["1"] });
+
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    mock.emitEvent("subagents:failed", { id: "agent-1", error: "crashed", status: "error" });
+
+    // B should not start
+    expect(bridge.spawned).toHaveLength(1);
+    const result = await mock.executeTool("TaskGet", { taskId: "2" });
+    expect(result.content[0].text).toContain("Status: pending");
+  });
+
+  it("tasks without agentType are not cascaded even if unblocked", async () => {
+    await mock.executeTool("TaskCreate", {
+      subject: "Agent task",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "Manual task",
+      description: "Desc",
+      // No agentType — manual
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "2", addBlockedBy: ["1"] });
+
+    await mock.executeTool("TaskExecute", { task_ids: ["1"] });
+    mock.emitEvent("subagents:completed", { id: "agent-1" });
+
+    // Manual task should stay pending
+    expect(bridge.spawned).toHaveLength(1);
+  });
+});
+
+describe("System prompt READY tags", () => {
+  it("marks unblocked agent-typed pending tasks as READY", async () => {
+    // Capture return values from lifecycle handlers
+    const lifecycleHandlers: Array<(...args: any[]) => any> = [];
+    const mock = mockPi();
+    const origOn = mock.pi.on.bind(mock.pi);
+    mock.pi.on = ((event: string, handler: any) => {
+      origOn(event, handler);
+      if (event === "before_agent_start") lifecycleHandlers.push(handler);
+    }) as any;
+
+    initExtension(mock.pi as any);
+
+    await mock.executeTool("TaskCreate", {
+      subject: "Ready task",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+
+    // Call the before_agent_start handler directly to get its return value
+    const result = await lifecycleHandlers[0]({ systemPrompt: "base" });
+    expect(result.systemPrompt).toContain("[READY — use TaskExecute to start]");
+    expect(result.systemPrompt).toContain("Ready task");
+  });
+
+  it("does not mark blocked agent tasks as READY", async () => {
+    const lifecycleHandlers: Array<(...args: any[]) => any> = [];
+    const mock = mockPi();
+    const origOn = mock.pi.on.bind(mock.pi);
+    mock.pi.on = ((event: string, handler: any) => {
+      origOn(event, handler);
+      if (event === "before_agent_start") lifecycleHandlers.push(handler);
+    }) as any;
+
+    initExtension(mock.pi as any);
+
+    await mock.executeTool("TaskCreate", {
+      subject: "Blocker",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskCreate", {
+      subject: "Blocked task",
+      description: "Desc",
+      agentType: "general-purpose",
+    });
+    await mock.executeTool("TaskUpdate", { taskId: "2", addBlockedBy: ["1"] });
+
+    const result = await lifecycleHandlers[0]({ systemPrompt: "base" });
+    // Task 1 should be READY, task 2 should NOT
+    expect(result.systemPrompt).toContain("#1 [pending] Blocker [READY");
+    expect(result.systemPrompt).not.toContain("#2 [pending] Blocked task [READY");
+  });
+
+  it("does not mark tasks without agentType as READY", async () => {
+    const lifecycleHandlers: Array<(...args: any[]) => any> = [];
+    const mock = mockPi();
+    const origOn = mock.pi.on.bind(mock.pi);
+    mock.pi.on = ((event: string, handler: any) => {
+      origOn(event, handler);
+      if (event === "before_agent_start") lifecycleHandlers.push(handler);
+    }) as any;
+
+    initExtension(mock.pi as any);
+
+    await mock.executeTool("TaskCreate", {
+      subject: "Manual task",
+      description: "Desc",
+    });
+
+    const result = await lifecycleHandlers[0]({ systemPrompt: "base" });
+    expect(result.systemPrompt).not.toContain("READY");
+  });
+});
+
+describe("Widget agent ID display", () => {
+  let store: TaskStore;
+  let widget: TaskWidget;
+  let ui: ReturnType<typeof mockUICtx>;
+
+  function mockUICtx() {
+    const state = {
+      widgets: new Map<string, any>(),
+      statuses: new Map<string, string | undefined>(),
+    };
+    const ctx: UICtx = {
+      setWidget(key, content, options) { state.widgets.set(key, { content, options }); },
+      setStatus(key, text) { state.statuses.set(key, text); },
+    };
+    return { ctx, state };
+  }
+
+  function mockTheme(): Theme {
+    return {
+      fg: (_color: string, text: string) => text,
+      bold: (text: string) => text,
+      strikethrough: (text: string) => `~~${text}~~`,
+    };
+  }
+
+  function renderWidget(state: ReturnType<typeof mockUICtx>["state"]): string[] {
+    const entry = state.widgets.get("tasks");
+    if (!entry?.content) return [];
+    const theme = mockTheme();
+    const tui = { terminal: { columns: 200 } };
+    return entry.content(tui, theme).render();
+  }
+
+  beforeEach(() => {
+    vi.useFakeTimers();
+    store = new TaskStore();
+    widget = new TaskWidget(store);
+    ui = mockUICtx();
+    widget.setUICtx(ui.ctx);
+  });
+
+  afterEach(() => {
+    widget.dispose();
+    vi.useRealTimers();
+  });
+
+  it("shows agent ID for active agent-backed tasks", () => {
+    store.create("Agent task", "Desc", "Running tests", { agentType: "general-purpose", agentId: "abc1234567890" });
+    store.update("1", { status: "in_progress" });
+    widget.setActiveTask("1", true);
+
+    const lines = renderWidget(ui.state);
+    expect(lines[1]).toContain("agent abc12");
+    expect(lines[1]).toContain("Running tests");
+  });
+
+  it("shows agent ID for non-active in_progress agent-backed tasks", () => {
+    store.create("Agent task", "Desc", undefined, { agentType: "general-purpose", agentId: "xyz9876543210" });
+    store.update("1", { status: "in_progress" });
+    // NOT calling setActiveTask — simulates external agent management
+    widget.update();
+
+    const lines = renderWidget(ui.state);
+    expect(lines[1]).toContain("agent xyz98");
+    expect(lines[1]).toContain("Agent task");
+  });
+
+  it("does not show agent ID for tasks without agentId", () => {
+    store.create("Manual task", "Desc");
+    store.update("1", { status: "in_progress" });
+    widget.update();
+
+    const lines = renderWidget(ui.state);
+    expect(lines[1]).not.toContain("agent");
+    expect(lines[1]).toContain("Manual task");
+  });
+
+  it("does not show agent ID for pending tasks", () => {
+    store.create("Pending agent task", "Desc", undefined, { agentType: "general-purpose", agentId: "abc12345" });
+    widget.update();
+
+    const lines = renderWidget(ui.state);
+    expect(lines[1]).not.toContain("agent abc");
+  });
+
+  it("does not show agent ID for completed tasks", () => {
+    store.create("Done", "Desc", undefined, { agentType: "general-purpose", agentId: "abc12345" });
+    store.update("1", { status: "completed" });
+    widget.update();
+
+    const lines = renderWidget(ui.state);
+    expect(lines[1]).not.toContain("agent abc");
+  });
+});