Content-free traces

Bonus: content-free traces

Time: 5–8 minutes

Flue’s Cloudflare tracing includes prompts, responses, instructions, tool arguments, and results by default. Keep the execution shape while turning that content capture off.

1. Install an explicit tracing policy

Update src/app.ts to install content-free tracing before creating the route map. The diff starts from completed checkpoint 6; Complete file includes the existing chat UI, ping endpoint, and agent route:

src/app.ts+4−0

Changes from Checkpoint 6 (guide) → Content-free traces bonus

Changes

src/app.ts

===================================================================
--- a/src/app.ts  Checkpoint 6 (guide)
+++ b/src/app.ts  Content-free traces bonus
@@ -1,8 +1,12 @@
 import { Hono } from 'hono';
 import { createAgentRouter } from '@flue/runtime/routing';
+import { instrument } from '@flue/runtime';
+import { createCloudflareTracing } from '@flue/runtime/cloudflare';
 import { FieldTrip } from './agents/field-trip.ts';
 import chatUi from './ui/index.html?raw';

+instrument(createCloudflareTracing({ content: false }));
+
 // src/app.ts is the Flue route map. Its default export owns every HTTP request
 // the Worker receives. Agents get mounted here with createAgentRouter(...)
 // starting in checkpoint 1.

Complete file

src/app.ts

import { Hono } from 'hono';
import { createAgentRouter } from '@flue/runtime/routing';
import { instrument } from '@flue/runtime';
import { createCloudflareTracing } from '@flue/runtime/cloudflare';
import { FieldTrip } from './agents/field-trip.ts';
import chatUi from './ui/index.html?raw';

instrument(createCloudflareTracing({ content: false }));

// src/app.ts is the Flue route map. Its default export owns every HTTP request
// the Worker receives. Agents get mounted here with createAgentRouter(...)
// starting in checkpoint 1.
const app = new Hono();

// A small chat UI for trying the agent in a browser, locally and on workers.dev.
app.get('/', (c) => c.html(chatUi));
app.get('/api/ping', (c) => c.text('pong'));
app.route('/agents/field-trip', createAgentRouter(FieldTrip));

export default app;

This explicit instrumentation replaces Flue’s built-in tracing install. The existing wrangler.jsonc already enables Workers Traces.

2. Deploy and inspect

Live deploy

npm run typecheck
npm run deploy
sleep 5
npm run smoke -- https://field-trip-agent.<subdomain>.workers.dev private-trace \
  "Plan a Lisbon offsite from <START> to <END> for 8 people. What's the weather?"

Use the exact deployed URL and the workshop dates. After ingestion, open the newest trace in Workers & Pages → field-trip-agent → Observability → Traces.

Save your workers.dev subdomain to open this test ↗https://field-trip-agent.<subdomain>.workers.dev/?id=private-trace

This opens the same conversation as the smoke test. If you repeat this checkpoint, use a fresh test IDbefore copying its commands.

Local dev

Restart npm run dev in Terminal A, then run in Terminal B:

npm run typecheck
npm run smoke -- http://localhost:5173 private-trace-local \
  "Plan a Lisbon offsite from <START> to <END> for 8 people. What's the weather?"

Open local chat in your browser ↗http://localhost:5173/?id=private-trace-local

This opens the same conversation as the smoke test. If you repeat this checkpoint, use a fresh test IDbefore copying its commands.

This tests the agent with the new instrumentation. To verify content-free Workers Traces in the dashboard, use the Live deploy tab.

Verification gate

Prove it works

• invoke_agent, chat, and execute_tool spans remain.
• Timing, status, model identity, and token usage remain.
• Messages, system instructions, tool arguments, and tool results are absent.

Reset

Remove both imports and instrument(...), then redeploy. Existing traces retain the policy used when they were recorded; only new traces change.

Reference: Flue Cloudflare tracing.