fix: expose abort signal to extensions closes #2660

packages/agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added `Agent.signal` to expose the active abort signal for the current turn, allowing callers to forward cancellation into nested async work ([#2660](https://github.com/badlogic/pi-mono/issues/2660))
+
 ## [0.63.1] - 2026-03-27
 
 ## [0.63.0] - 2026-03-27

packages/agent/src/agent.ts

@@ -371,6 +371,11 @@ export class Agent {
 		this._state.messages = [];
 	}
 
+	/** The current abort signal, or undefined when the agent is not streaming. */
+	get signal(): AbortSignal | undefined {
+		return this.abortController?.signal;
+	}
+
 	abort() {
 		this.abortController?.abort();
 	}

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added `ctx.signal` to `ExtensionContext` and wired it to the active agent turn so extension handlers can forward cancellation into nested model calls, `fetch()`, and other abort-aware work ([#2660](https://github.com/badlogic/pi-mono/issues/2660))
+
 ## [0.63.1] - 2026-03-27
 
 ### Added

packages/coding-agent/docs/extensions.md

@@ -629,6 +629,8 @@ Fired after tool execution finishes and before `tool_execution_end` plus the fin
 - Each handler sees the latest result after previous handler changes
 - Handlers can return partial patches (`content`, `details`, or `isError`); omitted fields keep their current values
 
+Use `ctx.signal` for nested async work inside the handler. This lets Esc cancel model calls, `fetch()`, and other abort-aware operations started by the extension.
+
 ```typescript
 import { isBashToolResult } from "@mariozechner/pi-coding-agent";
 
@@ -640,6 +642,12 @@ pi.on("tool_result", async (event, ctx) => {
     // event.details is typed as BashToolDetails
   }
 
+  const response = await fetch("https://example.com/summarize", {
+    method: "POST",
+    body: JSON.stringify({ content: event.content }),
+    signal: ctx.signal,
+  });
+
   // Modify result:
   return { content: [...], details: {...}, isError: false };
 });
@@ -759,6 +767,31 @@ ctx.sessionManager.getLeafId()        // Current leaf entry ID
 
 Access to models and API keys.
 
+### ctx.signal
+
+The current agent abort signal, or `undefined` when no agent turn is active.
+
+Use this for abort-aware nested work started by extension handlers, for example:
+- `fetch(..., { signal: ctx.signal })`
+- model calls that accept `signal`
+- file or process helpers that accept `AbortSignal`
+
+`ctx.signal` is typically defined during active turn events such as `tool_call`, `tool_result`, `message_update`, and `turn_end`.
+It is usually `undefined` in idle or non-turn contexts such as session events, extension commands, and shortcuts fired while pi is idle.
+
+```typescript
+pi.on("tool_result", async (event, ctx) => {
+  const response = await fetch("https://example.com/api", {
+    method: "POST",
+    body: JSON.stringify(event),
+    signal: ctx.signal,
+  });
+
+  const data = await response.json();
+  return { details: data };
+});
+```
+
 ### ctx.isIdle() / ctx.abort() / ctx.hasPendingMessages()
 
 Control flow helpers.

packages/coding-agent/src/core/agent-session.ts

@@ -2219,6 +2219,7 @@ export class AgentSession {
 			{
 				getModel: () => this.model,
 				isIdle: () => !this.isStreaming,
+				getSignal: () => this.agent.signal,
 				abort: () => this.abort(),
 				hasPendingMessages: () => this.pendingMessageCount > 0,
 				shutdown: () => {

packages/coding-agent/src/core/extensions/runner.ts

@@ -208,6 +208,7 @@ export class ExtensionRunner {
 	private errorListeners: Set<ExtensionErrorListener> = new Set();
 	private getModel: () => Model<any> | undefined = () => undefined;
 	private isIdleFn: () => boolean = () => true;
+	private getSignalFn: () => AbortSignal | undefined = () => undefined;
 	private waitForIdleFn: () => Promise<void> = async () => {};
 	private abortFn: () => void = () => {};
 	private hasPendingMessagesFn: () => boolean = () => false;
@@ -265,6 +266,7 @@ export class ExtensionRunner {
 		// Context actions (required)
 		this.getModel = contextActions.getModel;
 		this.isIdleFn = contextActions.isIdle;
+		this.getSignalFn = contextActions.getSignal;
 		this.abortFn = contextActions.abort;
 		this.hasPendingMessagesFn = contextActions.hasPendingMessages;
 		this.shutdownHandler = contextActions.shutdown;
@@ -541,6 +543,7 @@ export class ExtensionRunner {
 				return getModel();
 			},
 			isIdle: () => this.isIdleFn(),
+			signal: this.getSignalFn(),
 			abort: () => this.abortFn(),
 			hasPendingMessages: () => this.hasPendingMessagesFn(),
 			shutdown: () => this.shutdownHandler(),

packages/coding-agent/src/core/extensions/types.ts

@@ -274,6 +274,8 @@ export interface ExtensionContext {
 	model: Model<any> | undefined;
 	/** Whether the agent is idle (not streaming) */
 	isIdle(): boolean;
+	/** The current abort signal, or undefined when the agent is not streaming. */
+	signal: AbortSignal | undefined;
 	/** Abort the current agent operation */
 	abort(): void;
 	/** Whether there are queued messages waiting */
@@ -1391,6 +1393,7 @@ export interface ExtensionActions {
 export interface ExtensionContextActions {
 	getModel: () => Model<any> | undefined;
 	isIdle: () => boolean;
+	getSignal: () => AbortSignal | undefined;
 	abort: () => void;
 	hasPendingMessages: () => boolean;
 	shutdown: () => void;

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -1280,6 +1280,7 @@ export class InteractiveMode {
 			modelRegistry: this.session.modelRegistry,
 			model: this.session.model,
 			isIdle: () => !this.session.isStreaming,
+			signal: this.session.agent.signal,
 			abort: () => this.session.abort(),
 			hasPendingMessages: () => this.session.pendingMessageCount > 0,
 			shutdown: () => {

packages/coding-agent/test/extensions-runner.test.ts

@@ -71,6 +71,7 @@ describe("ExtensionRunner", () => {
 	const extensionContextActions: ExtensionContextActions = {
 		getModel: () => undefined,
 		isIdle: () => true,
+		getSignal: () => undefined,
 		abort: () => {},
 		hasPendingMessages: () => false,
 		shutdown: () => {},
@@ -399,6 +400,26 @@ describe("ExtensionRunner", () => {
 		});
 	});
 
+	describe("context creation", () => {
+		it("exposes the current abort signal on ExtensionContext", async () => {
+			const result = await discoverAndLoadExtensions([], tempDir, tempDir);
+			const runner = new ExtensionRunner(result.extensions, result.runtime, tempDir, sessionManager, modelRegistry);
+			const controller = new AbortController();
+
+			runner.bindCore(extensionActions, {
+				...extensionContextActions,
+				getSignal: () => controller.signal,
+			});
+
+			const ctx = runner.createContext();
+			expect(ctx.signal).toBe(controller.signal);
+			expect(ctx.signal?.aborted).toBe(false);
+
+			controller.abort();
+			expect(ctx.signal?.aborted).toBe(true);
+		});
+	});
+
 	describe("error handling", () => {
 		it("calls error listeners when handler throws", async () => {
 			const extCode = `

packages/coding-agent/test/trigger-compact-extension.test.ts

@@ -11,6 +11,7 @@ function createContext(tokens: number | null, compact = vi.fn()): ExtensionConte
 		modelRegistry: {} as ExtensionContext["modelRegistry"],
 		model: undefined,
 		isIdle: () => true,
+		signal: undefined,
 		abort: vi.fn(),
 		hasPendingMessages: () => false,
 		shutdown: vi.fn(),