---
title: "Tie every line to its request · Agent Wranglers"
url: https://agentwranglers.se/playbook/operations/logs/request-ids
updated: 2026-10-20
licence: "All rights reserved"
---

# Tie every line to its request

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Required
- Chapter: [Logs](https://agentwranglers.se/playbook/operations/logs)
- Rule: Give every request an ID, pass it to every service it touches, and write it on every log line and error page.
- How: At the edge, accept an incoming `traceparent` header only if it matches the W3C format, otherwise create a new random ID. Keep the ID in request context, add it to every log line, and return it in a response header. Pass it on every outgoing call. Show it on error pages, so support can find the exact lines.
- Check: Trigger an error on staging. The error page shows an ID, and searching the logs for it returns every line of that request, across services.

Example:

```js
import { AsyncLocalStorage } from 'node:async_hooks';
import { randomUUID } from 'node:crypto';

const TRACEPARENT = /^00-([0-9a-f]{32})-[0-9a-f]{16}-[0-9a-f]{2}$/;
export const requestContext = new AsyncLocalStorage();

app.use((req, res, next) => {
  const requestId = TRACEPARENT.exec(req.get('traceparent') ?? '')?.[1] ?? randomUUID().replaceAll('-', '');
  res.set('X-Request-Id', requestId);
  requestContext.run({ requestId, log: log.child({ request_id: requestId }) }, next);
});
```

```python
import re
import uuid
import structlog

TRACEPARENT = re.compile(r"^00-([0-9a-f]{32})-[0-9a-f]{16}-[0-9a-f]{2}$")

@app.middleware("http")
async def tag_request(request, call_next):
    match = TRACEPARENT.match(request.headers.get("traceparent", ""))
    request_id = match.group(1) if match else uuid.uuid4().hex
    structlog.contextvars.clear_contextvars()
    structlog.contextvars.bind_contextvars(request_id=request_id)
    response = await call_next(request)
    response.headers["X-Request-Id"] = request_id
    return response
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers operations playbook: https://agentwranglers.se/playbook/operations/logs/request-ids`.

- Previous: [Log structured events](https://agentwranglers.se/playbook/operations/logs/structured-logs)
- Next: [Use log levels with fixed meanings](https://agentwranglers.se/playbook/operations/logs/log-levels)
- [Logs](https://agentwranglers.se/playbook/operations/logs)