t8y2/dbx · error

agent did not become ready: %s

Error message

agent did not become ready: %s

What it means

After a successful Scan, startAgent validates the readiness line contains "ready":true. If the first stdout line is something else, the agent is killed and this error includes the unexpected text verbatim, signaling a protocol violation on the startup handshake.

Source

Thrown at agents/drivers/rabbitmq/bench/agent_compare.go:328

	stdout, err := process.command.StdoutPipe()
	if err != nil {
		return nil, 0, err
	}
	process.command.Stderr = os.Stderr
	process.stdin = stdin
	process.reader = bufio.NewScanner(stdout)
	process.reader.Buffer(make([]byte, 64*1024), 512*1024*1024)
	start := time.Now()
	if err := process.command.Start(); err != nil {
		return nil, 0, err
	}
	if !process.reader.Scan() {
		process.kill()
		return nil, 0, fmt.Errorf("agent did not become ready: %v", process.reader.Err())
	}
	if !strings.Contains(process.reader.Text(), `"ready":true`) {
		process.kill()
		return nil, 0, fmt.Errorf("agent did not become ready: %s", process.reader.Text())
	}
	return process, time.Since(start), nil
}

func (process *agentProcess) call(method string, params map[string]any) (json.RawMessage, error) {
	process.nextID++
	request := map[string]any{
		"jsonrpc": "2.0",
		"id":      process.nextID,
		"method":  method,
		"params":  params,
	}
	payload, err := json.Marshal(request)
	if err != nil {
		return nil, err
	}
	if _, err := process.stdin.Write(append(payload, '\n')); err != nil {
		return nil, err

View on GitHub (pinned to c0390bff16)

Solutions

1. Configure all agent logging to stderr, keeping stdout for the JSON protocol
2. Confirm the agent prints {"ready":true} exactly once as the first stdout line
3. Align the agent version with what the benchmark expects (ready-line contract)
4. Inspect the %s text in the error to see exactly what was emitted instead

Example fix

// before
log.Printf("agent starting") // goes to stdout by default in some setups
fmt.Println(`{"ready":true}`)
// after
log.SetOutput(os.Stderr)
fmt.Println(`{"ready":true}`)

// enforce stdout purity: in the agent, before anything else
if os.Getenv("AGENT_PROTOCOL_STDOUT") == "1" {
    log.SetOutput(os.Stderr)
}

if err != nil && strings.Contains(err.Error(), "agent did not become ready") {
    log.Fatalf("ready-line protocol violation: %v", err)
}

When it happens

Trigger: The agent emits a log line, warning, or banner on stdout as its first output instead of the JSON readiness line, or prints a readiness line with different formatting (e.g. "ready": false or plain text).

Common situations: A logging library configured to write INFO logs to stdout pollutes the handshake; agent version changed its ready-line format; agent prints deprecation warnings before readiness.

Related errors

• timed out waiting for agent readiness
• agent did not become ready: %v
• Unknown method: {method}
• Unknown method: <method>
• agent exited before {method}

AI-assisted analysis of t8y2/dbx@c0390bff16 (2026-09-05). Data as JSON: /api/errors/0678202866cc453b. Report an issue: GitHub.