🤖 Pass abort controllers through runtime stack

[ammar-agent]

Prevents indefinite hangs when cancelling long-running operations by passing abort signals through the runtime stack.

Changes

• Runtime interfaces: Added optional abortSignal parameter to operations with long timeouts (≥30s)
• LocalRuntime: Accepts but ignores abort signals (local operations are fast)
• SSHRuntime: Passes abort signals to all exec() calls and spawn() operations
• Tool integration: Bash tool passes abort signal to runtime operations

Impact

Long-running operations can now be cancelled cleanly:

• Git operations (clone, checkout, init hooks)
• SSH file I/O (readFile, writeFile)
• Workspace operations (create, rename, delete)
• Bundle creation for SSH sync

Generated with cmux

[chatgpt-codex-connector]

💡 Codex Review

cmux/src/runtime/SSHRuntime.ts

Lines 435 to 465 in 2760b83

	// Step 2: Create bundle locally and pipe to remote file via SSH
	initLogger.logStep(`Creating git bundle...`);
	await new Promise<void>((resolve, reject) => {
	const sshArgs = this.buildSSHArgs(true);
	const command = `cd ${shescape.quote(projectPath)} && git bundle create - --all | ssh ${sshArgs.join(" ")} "cat > ${bundleTempPath}"`;
	log.debug(`Creating bundle: ${command}`);
	const proc = spawn("bash", ["-c", command]);
	streamProcessToLogger(proc, initLogger, {
	logStdout: false,
	logStderr: true,
	});
	let stderr = "";
	proc.stderr.on("data", (data: Buffer) => {
	stderr += data.toString();
	});
	proc.on("close", (code) => {
	if (code === 0) {
	resolve();
	} else {
	reject(new Error(`Failed to create bundle: ${stderr}`));
	}
	});
	proc.on("error", (err) => {
	reject(err);
	});
	});

Wire abortSignal to git bundle spawn

The new abortSignal is passed into syncProjectToRemote, but the expensive "git bundle" step still spawns a local process without listening for that signal. If a workspace initialization is cancelled while the bundle is being generated, this Promise keeps running until the bundle command finishes, so callers still block for minutes despite cancellation. Consider hooking the signal to proc.kill() (and rejecting the Promise) so that cancellation is effective for the longest phase of workspace syncing.

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[ammar-agent]

@codex This has been addressed. The bundle creation spawn() now hooks the abort signal to proc.kill() and rejects the Promise when cancelled. See the latest commit.

[ammar-agent]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

cmux/src/runtime/SSHRuntime.ts

Lines 164 to 205 in d388f1b

	// Spawn ssh command
	const sshProcess = spawn("ssh", sshArgs, {
	stdio: ["pipe", "pipe", "pipe"],
	});
	// Convert Node.js streams to Web Streams
	const stdout = Readable.toWeb(sshProcess.stdout) as unknown as ReadableStream<Uint8Array>;
	const stderr = Readable.toWeb(sshProcess.stderr) as unknown as ReadableStream<Uint8Array>;
	const stdin = Writable.toWeb(sshProcess.stdin) as unknown as WritableStream<Uint8Array>;
	// Track if we killed the process due to timeout
	let timedOut = false;
	// Create promises for exit code and duration
	// Uses special exit codes (EXIT_CODE_ABORTED, EXIT_CODE_TIMEOUT) for expected error conditions
	const exitCode = new Promise<number>((resolve, reject) => {
	sshProcess.on("close", (code, signal) => {
	// Check abort first (highest priority)
	if (options.abortSignal?.aborted) {
	resolve(EXIT_CODE_ABORTED);
	return;
	}
	// Check if we killed the process due to timeout
	// Don't check signal - if we set timedOut, we timed out regardless of how process died
	if (timedOut) {
	resolve(EXIT_CODE_TIMEOUT);
	return;
	}
	resolve(code ?? (signal ? -1 : 0));
	});
	sshProcess.on("error", (err) => {
	reject(new RuntimeErrorClass(`Failed to execute SSH command: ${err.message}`, "exec", err));
	});
	});
	const duration = exitCode.then(() => performance.now() - startTime);
	// Handle abort signal
	if (options.abortSignal) {
	options.abortSignal.addEventListener("abort", () => sshProcess.kill("SIGKILL"));
	}

Respect already-aborted signals before spawning SSH commands

The new abort handling in SSHRuntime.exec only registers a listener after the SSH process is spawned and never checks whether options.abortSignal is already in the aborted state. AbortSignal events do not fire retroactively, so if the controller is aborted before exec is called (for example, a user cancels initialization between sequential steps), the method will still launch the remote command and it will run until completion or timeout, defeating the cancellation the commit is trying to add. Consider short‑circuiting at the top of exec or killing the process immediately when abortSignal.aborted is true so that later operations don’t start once cancellation has been requested.

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• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

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