fix(bash): add 120s default timeout to prevent autonomous mode hangs

- Add BUILT_IN_DEFAULT_TIMEOUT_SECS = 120 constant to bash tool
- Compute effectiveTimeout = timeout ?? resolvedDefaultTimeout so LLM
  calls without a timeout get the 120s guard automatically
- Add defaultTimeoutSeconds? to BashToolOptions for override at creation
- Dynamic bashSchemaWithDefault describes the actual default in the LLM
  tool description, improving model awareness
- Add BashSettings interface + getBashDefaultTimeoutSeconds() to
  SettingsManager so users can override or disable via settings.json
- Wire defaultTimeoutSeconds into agent-session.ts _buildRuntime()

Root cause: npx sf --help triggered npm package download, hanging for
4+ minutes without timeout, consuming entire autonomous run budget.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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

@@ -2530,6 +2530,8 @@ export class AgentSession {
 					read: { autoResizeImages },
 					bash: {
 						commandPrefix: shellCommandPrefix,
+						defaultTimeoutSeconds:
+							this.settingsManager.getBashDefaultTimeoutSeconds(),
 						interceptor: {
 							enabled: this.settingsManager.getBashInterceptorEnabled(),
 							rules: this.settingsManager.getBashInterceptorRules(),

packages/coding-agent/src/core/settings-manager.ts

@@ -51,6 +51,14 @@ export interface BashInterceptorSettings {
 	rules?: BashInterceptorRule[]; // override default rules
 }
 
+export interface BashSettings {
+	/**
+	 * Default timeout in seconds for bash commands when the LLM does not provide one.
+	 * Set to 0 to disable (commands run without a timeout). Defaults to 120.
+	 */
+	defaultTimeoutSeconds?: number;
+}
+
 export interface MarkdownSettings {
 	codeBlockIndent?: string; // default: "  "
 }
@@ -173,6 +181,7 @@ export interface Settings {
 	memory?: MemorySettings;
 	async?: AsyncSettings;
 	bashInterceptor?: BashInterceptorSettings;
+	bash?: BashSettings;
 	taskIsolation?: TaskIsolationSettings;
 	fallback?: FallbackSettings;
 	modelDiscovery?: ModelDiscoverySettings;
@@ -505,6 +514,16 @@ export class SettingsManager {
 		return this.settings.bashInterceptor?.rules;
 	}
 
+	/**
+	 * Default bash command timeout in seconds. Returns undefined when unset,
+	 * which lets the bash tool use its built-in default (120s).
+	 * Returns 0 explicitly when the user has disabled the default.
+	 */
+	getBashDefaultTimeoutSeconds(): number | undefined {
+		const val = this.settings.bash?.defaultTimeoutSeconds;
+		return typeof val === "number" ? val : undefined;
+	}
+
 	reload(): void {
 		const globalLoad = SettingsManager.tryLoadFromStorage(
 			this.storage,

packages/coding-agent/src/core/tools/bash.ts

@@ -28,6 +28,15 @@ import {
 	truncateTail,
 } from "./truncate.js";
 
+/**
+ * Built-in default timeout (seconds) applied when the caller does not provide
+ * one and `BashToolOptions.defaultTimeoutSeconds` is not set.
+ * Prevents stuck commands (e.g. `npx pkg --help` triggering a download) from
+ * consuming the entire autonomous-mode run budget.
+ * Set `defaultTimeoutSeconds: 0` in BashToolOptions to opt out.
+ */
+const BUILT_IN_DEFAULT_TIMEOUT_SECS = 120;
+
 // Cached Win32 FFI handles for restoring VT input after child processes
 let _vtHandles: {
 	GetConsoleMode: any;
@@ -145,7 +154,8 @@ const bashSchema = Type.Object({
 	command: Type.String({ description: "Bash command to execute" }),
 	timeout: Type.Optional(
 		Type.Number({
-			description: "Timeout in seconds (optional, no default timeout)",
+			description:
+				"Timeout in seconds. Omitting uses the built-in default (see createBashTool). Pass 0 to run without timeout.",
 		}),
 	),
 });
@@ -316,6 +326,12 @@ export interface BashToolOptions {
 	};
 	/** Tool names available in the session, used by the interceptor to check if replacement tools exist */
 	availableToolNames?: string[] | (() => string[]);
+	/**
+	 * Default timeout in seconds applied when the LLM does not provide one.
+	 * Set to 0 to disable the built-in default (allows commands to run indefinitely).
+	 * Defaults to BUILT_IN_DEFAULT_TIMEOUT_SECS (120s) when not set.
+	 */
+	defaultTimeoutSeconds?: number;
 }
 
 export function createBashTool(
@@ -326,6 +342,12 @@ export function createBashTool(
 	const commandPrefix = options?.commandPrefix;
 	const spawnHook = options?.spawnHook;
 	const artifactManager = options?.artifactManager;
+	// Resolve the default timeout once at construction time.
+	// Explicit 0 in options disables the built-in default; undefined falls through to BUILT_IN_DEFAULT_TIMEOUT_SECS.
+	const resolvedDefaultTimeout =
+		options?.defaultTimeoutSeconds !== undefined
+			? options.defaultTimeoutSeconds
+			: BUILT_IN_DEFAULT_TIMEOUT_SECS;
 
 	// Pre-compile interceptor rules once at construction time
 	const interceptorInstance = options?.interceptor?.enabled
@@ -334,17 +356,32 @@ export function createBashTool(
 			)
 		: null;
 
+	const timeoutDescription =
+		resolvedDefaultTimeout > 0
+			? `Default: ${resolvedDefaultTimeout}s. Pass 0 to run without a timeout.`
+			: "No default timeout — commands run until completion.";
+	const bashSchemaWithDefault = Type.Object({
+		command: Type.String({ description: "Bash command to execute" }),
+		timeout: Type.Optional(
+			Type.Number({
+				description: `Timeout in seconds. ${timeoutDescription}`,
+			}),
+		),
+	});
+
 	return {
 		name: "bash",
 		label: "bash",
-		description: `Execute a bash command in the current working directory. Returns stdout and stderr. Output is truncated to last ${DEFAULT_MAX_LINES} lines or ${DEFAULT_MAX_BYTES / 1024}KB (whichever is hit first). If truncated, full output is saved to a temp file. Optionally provide a timeout in seconds.`,
-		parameters: bashSchema,
+		description: `Execute a bash command in the current working directory. Returns stdout and stderr. Output is truncated to last ${DEFAULT_MAX_LINES} lines or ${DEFAULT_MAX_BYTES / 1024}KB (whichever is hit first). If truncated, full output is saved to a temp file. Default timeout: ${resolvedDefaultTimeout > 0 ? `${resolvedDefaultTimeout}s` : "none"} — pass a higher value for long-running commands (builds, installs, tests).`,
+		parameters: bashSchemaWithDefault,
 		execute: async (
 			_toolCallId: string,
 			{ command, timeout }: { command: string; timeout?: number },
 			signal?: AbortSignal,
 			onUpdate?,
 		) => {
+			// Apply the resolved default when the LLM does not provide a timeout.
+			const effectiveTimeout = timeout ?? resolvedDefaultTimeout;
 			// Check bash interceptor — block commands that duplicate dedicated tools
 			if (interceptorInstance) {
 				const toolNames =
@@ -463,7 +500,7 @@ export function createBashTool(
 					.exec(spawnContext.command, spawnContext.cwd, {
 						onData: handleData,
 						signal,
-						timeout,
+						timeout: effectiveTimeout,
 						env: spawnContext.env,
 					})
 					.then(({ exitCode }) => {

packages/coding-agent/src/index.ts

@@ -280,6 +280,7 @@ export {
 } from "./core/session-manager.js";
 export {
 	type AsyncSettings,
+	type BashSettings,
 	type CompactionSettings,
 	type ImageSettings,
 	type MemorySettings,