Context and waitUntil

On Cloudflare Workers, a callback passed to waitUntil runs after the response is sent, outside the request’s AsyncLocalStorage scope. Logs in that callback lose HTTP context (requestId, method, url) unless you restore it. This guide shows how to snapshot and re-enter the active log store.

Prerequisites

1. Enable context in config:

{
  "log": { "enableContext": true }
}

Or set FLARE__log__enableContext=true.

2. Enable nodejs_compat in wrangler.toml (required for Flare on Workers generally).

Capture context before waitUntil

While the handler still runs inside the request scope, call captureLogStore():

import { captureLogStore, runWithLogStore } from "@flare-ts/core";
import { waitUntil } from "cloudflare:workers";

// Inside a handler with active request scope:
const store = captureLogStore();
waitUntil(
  runWithLogStore(store, async () => {
    // logs here carry the same context as the handler's logs
  }),
);

Import waitUntil from cloudflare:workers. The runtime provides the current request’s context; Flare does not thread ExecutionContext through your handlers.

Use with DI in a handler

import {
  FlareHost,
  FlareResponse,
  Logger,
  captureLogStore,
  runWithLogStore,
} from "@flare-ts/core";
import { cf } from "@flare-ts/core/cloudflare";
import { waitUntil } from "cloudflare:workers";

const host = new FlareHost(cf);

host.http.post(
  "/orders",
  { inject: { log: Logger } },
  (_ctx, scope) => {
    const store = captureLogStore();
    waitUntil(
      runWithLogStore(store, async () => {
        scope.log.info("async follow-up");
      }),
    );
    return new FlareResponse(202, { accepted: true });
  },
);

export default host.build().export();

API behavior

Function	Behavior
captureLogStore()	Returns { context, state? } when context is active, or undefined when log.enableContext is off or no store exists
runWithLogStore(store, fn)	Runs fn inside the captured store; returns whatever fn returns. When store is undefined, runs fn without entering a store

runWithLogStore with an async callback returns a Promise, which is what waitUntil expects.

What appears on records

When log.enableContext is true:

Context	When on record.context
source: "flare:host"	During host.build() on every runtime
source: "flare:http" with requestId, method, url	During each incoming HTTP request

When the restored store includes state, it also appears on record.state.

Related

• Logging overview
• flare.json reference
• Host: Workers app.export() and WorkerExportedHandle