github/copilot-sdk · error · IllegalStateException

Cannot connect: no process for stdio and no host:port for…

Error message

Cannot connect: no process for stdio and no host:port for TCP

What it means

CliServerManager.connectToServer builds a JsonRpcClient either from a TCP socket (host/port configured) or from the spawned stdio child process. If neither is available — no process was started and no TCP host/port is set — it throws IllegalStateException because there is no transport to connect through. This reflects an inconsistently initialized CliServerManager.

Solutions

1. Call startCliServer (or configure a TCP host/port + token) before connectToServer.
2. Check that CLI startup did not silently fail; verify the process reference is non-null.
3. Set CliUrl in options if you intend TCP mode instead of a locally spawned CLI.

Example fix

// before
manager.connectToServer(); // manager never started
// after
manager.startCliServer();
JsonRpcClient client = manager.connectToServer();

if (manager == null || (!manager.hasProcess() && !options.hasTcpEndpoint())) {
    manager.startCliServer(); // or configure tcp host/port
}

try {
  client = manager.connectToServer();
} catch (IllegalStateException e) {
  if (e.getMessage().contains("no process")) {
    manager.startCliServer();
    client = manager.connectToServer();
  } else throw e;
}

When it happens

Trigger: Calling connectToServer on a CliServerManager that was constructed without starting the CLI process (startCliServer never invoked or failed) and without cliUrl/tcp host+port options.

Common situations: Skipping startCliServer and calling connect directly; startCliServer failed earlier leaving process null; building a manager for TCP mode but forgetting to set host/port options.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• CLI process exited unexpectedly.
• Timeout waiting for CLI to announce port
• CLI process exited unexpectedly.
• copilot_runtime_connection_open failed.
• CLI process not started

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/b404a326fde6f7c4. Report an issue: GitHub.

Appendix: source

Thrown at java/sdk/src/main/java/com/github/copilot/CliServerManager.java:164

     *            the CLI process (null if connecting to external server)
     * @param tcpHost
     *            the host to connect to (null for stdio mode)
     * @param tcpPort
     *            the port to connect to (null for stdio mode)
     * @return the JSON-RPC client connected to the server
     * @throws IOException
     *             if connection fails
     */
    JsonRpcClient connectToServer(Process process, String tcpHost, Integer tcpPort) throws IOException {
        if (tcpHost != null && tcpPort != null) {
            // TCP mode: external server or child process with explicit port
            Socket socket = new Socket(tcpHost, tcpPort);
            return JsonRpcClient.fromSocket(socket);
        } else if (process != null) {
            // Stdio mode: child process
            return JsonRpcClient.fromProcess(process);
        } else {
            throw new IllegalStateException("Cannot connect: no process for stdio and no host:port for TCP");
        }
    }

    private void startStderrReader(Process process) {
        var thread = new Thread(() -> {
            try (BufferedReader reader = new BufferedReader(
                    new InputStreamReader(process.getErrorStream(), StandardCharsets.UTF_8))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    synchronized (stderrBuffer) {
                        stderrBuffer.append(line).append('\n');
                    }
                    LOG.fine("[CLI] " + line);
                }
            } catch (IOException e) {
                LOG.log(Level.FINE, "Error reading stderr", e);
            }
        }, "cli-stderr-reader");

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