mastra-ai/mastra · error · Error

No response body for log stream

Error message

No response body for log stream

What it means

Thrown by streamLogs after the response passes the ok check but has a null body — meaning the runtime cannot provide a readable stream for the SSE response. The reader/getReader() streaming loop requires a non-null body, so the CLI fails fast rather than dereferencing null.

Source

Thrown at packages/cli/src/commands/studio/deploy-logs.ts:43

}

async function streamLogs(deployId: string, token: string, orgId: string) {
  const url = `${MASTRA_PLATFORM_API_URL}/v1/studio/deploys/${deployId}/logs/stream`;

  const resp = await platformFetch(url, {
    headers: {
      ...authHeaders(token, orgId),
      Accept: 'text/event-stream',
    },
  });

  if (!resp.ok) {
    const text = await resp.text();
    throw new Error(`Failed to stream logs: ${resp.status} — ${text}`);
  }

  if (!resp.body) {
    throw new Error('No response body for log stream');
  }

  const reader = resp.body.getReader();
  const decoder = new TextDecoder();
  let buffer = '';

  // Handle Ctrl+C gracefully
  process.on('SIGINT', () => {
    void reader.cancel();
    process.exit(0);
  });

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;

    buffer += decoder.decode(value, { stream: true });
    // Parse SSE data lines, keeping any incomplete trailing line in the buffer

View on GitHub (pinned to 75dd419e61)

Solutions

1. Upgrade to a recent Node.js LTS (18+) where fetch response streaming is fully supported.
2. Retry the command — transient empty-body 200s can occur behind proxies.
3. Use the non-streaming `mastra studio deploy logs` command as a fallback for fetching logs.
4. Check whether a corporate proxy is stripping response bodies and bypass it if possible.

try {
  await streamLogs(deployId, token);
} catch (err) {
  if ((err as Error).message === 'No response body for log stream') {
    console.error('Runtime does not support response streaming; using non-streaming logs.');
    await getLogs(deployId);
    return;
  }
  throw err;
}

When it happens

Trigger: The log stream endpoint returns 2xx but `resp.body` is null: runtimes that don't support response streaming (some Node fetch implementations/undici configurations), responses constructed without a body, or an intermediary stripping the body.

Common situations: Older Node.js versions or polyfilled fetch without streaming support; corporate proxies returning buffered empty 200 responses; unusual runtime environments where getReader() on the body is unavailable.

Related errors

• Failed to stream logs: ${resp.status} — ${text}
• Response body is null
• Response body is null
• @mastra/livekit: Mastra agent stream returned an empty respo
• Experiment emitted multiple terminal semantic events

AI-assisted analysis of mastra-ai/mastra@75dd419e61 (2026-08-30). Data as JSON: /api/errors/e69a38af061d3af3. Report an issue: GitHub.