Debug

Inject fetch() logging calls into user code that send structured data to a local HTTP ingest server. Log entries accumulate in JSONL files you can read for analysis.

Prerequisites

The env-snapshot includes a logIngest field once the ingest server is running:

logIngest: { port: <number>, token: "<uuid>" }

If logIngest is null, the server has not started yet — wait for an env-change.

Protocol

1. Create a log channel

Use write to create an empty JSONL file. The channel name must be kebab-case ([a-z0-9]+(-[a-z0-9]+)*).

write('logs/react-renders.jsonl', '')

This registers the channel. You will receive a log-channel-created env-change.

2. Construct the ingest URL

http://127.0.0.1:{port}/ingest/{channel-name}?token={token}

Example: http://127.0.0.1:54321/ingest/react-renders?token=abc-123

3. Inject instrumentation code

Wrap all injected debug code in region markers for easy identification and removal:

// #region @stagewise-debug
fetch('http://127.0.0.1:54321/ingest/react-renders?token=abc-123', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    level: 'info',
    source: 'useEffect-mount',
    data: { component: 'App', props: { userId: 42 } }
  })
}).catch(() => {});
// #endregion @stagewise-debug

Rules:

• Always wrap in // #region @stagewise-debug / // #endregion @stagewise-debug.
• Always .catch(() => {}) — instrumentation must never break user code.
• Keep payloads small. The source field distinguishes instrumentation points.

4. POST body schema

{
  "level": "info" | "warn" | "error" | "debug" | "log",
  "source": "descriptive-label",
  "data": { ... }
}

Body must be a JSON object. All fields are optional. level defaults to "log". The server prepends a ts field (epoch milliseconds) automatically — do not send your own.

5. Read logs

read('logs/react-renders.jsonl')

Each line is a JSON object with a server-injected timestamp: { "ts": 1713000000000, "level": "info", "source": "useEffect-mount", "data": { ... } }.

Use grepSearch with mount_prefix targeting logs for filtered searches.

6. Env-change notifications

You receive these for owned log channels only:

7. Size limits

• 64 KB max per POST body. Split large payloads.
• 2 MB max per log file. The server returns 409 when full.

When a file is full: read and analyze the data, then truncate with write('logs/{name}.jsonl', '') and continue.

8. Cleanup (mandatory)

When debugging is complete, always perform both steps:

1. Remove instrumentation — delete all // #region @stagewise-debug … // #endregion @stagewise-debug blocks from user code.
2. Delete log files — delete('logs/{name}.jsonl') for every channel you created.

Never leave debug instrumentation or log files behind.

Notes

• Browser-side code: The ingest server handles CORS (Access-Control-Allow-Origin: *). fetch() works from any origin.
• Node.js server code: fetch() works directly to 127.0.0.1.
• Write buffering: Entries are buffered and flushed every 500ms or 50 entries. There may be a short delay before new entries appear in the file.