can1357/oh-my-pi · error · ToolError

Invalid cmux socket JSON response: ${err instanceof Error ?

Error message

Invalid cmux socket JSON response: ${err instanceof Error ? err.message : String(err)}

What it means

#parseResponse JSON.parses each reply line from the cmux socket; when parsing fails it throws this ToolError embedding the JSON parse error message. It means the daemon (or something on the socket) returned a line that is not valid JSON and not an 'ERROR:' line, so the client cannot interpret the response envelope.

Source

Thrown at packages/coding-agent/src/tools/browser/cmux/socket-client.ts:391

			let line = this.#buffer.slice(0, newlineIndex);
			this.#buffer = this.#buffer.slice(newlineIndex + 1);
			if (line.endsWith("\r")) {
				line = line.slice(0, -1);
			}
			const waiter = this.#lineWaiters.shift();
			waiter?.resolve(line);
		}
	}

	#parseResponse(line: string): Record<string, unknown> {
		if (line.startsWith("ERROR:")) {
			throw new ToolError(line);
		}
		let payload: unknown;
		try {
			payload = JSON.parse(line);
		} catch (err) {
			throw new ToolError(`Invalid cmux socket JSON response: ${err instanceof Error ? err.message : String(err)}`);
		}
		if (!payload || typeof payload !== "object") {
			throw new ToolError("Invalid cmux socket response: expected object");
		}
		const response = payload as { ok?: unknown; result?: unknown; error?: CmuxErrorPayload };
		if (response.ok === true) {
			return (response.result ?? {}) as Record<string, unknown>;
		}
		if (response.ok === false) {
			throw new ToolError(formatCmuxError(response.error));
		}
		throw new ToolError("Invalid cmux socket response: missing ok flag");
	}

	#handleSocketFailure(err: Error): void {
		if (this.#disposed) return;
		this.#connected = false;
		this.#connectPromise = null;

View on GitHub (pinned to 9690622007)

Solutions

1. Verify the socketPath points at the cmux daemon's JSON line socket, not another service
2. Restart the cmux daemon and retry — a truncated response usually follows a daemon-side fault
3. Check daemon logs for crashes/corruption around the failing request
4. Upgrade client and daemon together so framing/version conventions match

Example fix

// before: pointing at a random debug socket
new CmuxSocketClient({ socketPath: "/tmp/app.sock" })
// after: the cmux daemon's control socket
new CmuxSocketClient({ socketPath: cmuxControlSocketPath })

// preflight: confirm the socket answers with a framed JSON line
const probe = net.createConnection({ path: socketPath });
// if it's a TCP relay endpoint use { host: '127.0.0.1', port } instead

function looksLikeJsonLine(s: string): boolean {
  try { const v = JSON.parse(s); return typeof v === "object" && v !== null; } catch { return false; }
}

try {
  return await client.request(method, params);
} catch (err) {
  if (err instanceof ToolError && err.message.startsWith("Invalid cmux socket JSON response")) {
    // wrong endpoint or daemon fault: verify socketPath, restart daemon, retry once
  }
  throw err;
}

When it happens

Trigger: Server emits a banner, log line, or partial/interleaved output on the socket; response truncated by an early close; a proxy or wrong service bound to the socket path returns non-JSON (HTML, plaintext); multi-line JSON payloads sent without newline framing the client expects.

Common situations: Version-mismatched daemon speaking a different framing; connecting the client to the wrong unix socket/port (another daemon's protocol); server crash mid-response leaving a partial line.

Understand the failure class

Background: "Invalid JSON response" and "Failed to parse response" errors: when an API answers 200 but the body isn't the JSON your library expected — this error's family across 28 libraries.

Related errors

• Replacement text is not valid UTF-8: {err}
• Anthropic cache refresh returned a malformed response
• rpc frame must be an object
• Invalid cmux socket response: expected object
• Invalid cmux socket response: missing ok flag

AI-assisted analysis of can1357/oh-my-pi@9690622007 (2026-08-31). Data as JSON: /api/errors/87021b19b835ef4d. Report an issue: GitHub.