@sentry/cloudflare: Durable Object methods called from the constructor's blockConcurrencyWhile callback are captured as untraced RPC entries

[msnelling]

Version

@sentry/cloudflare 10.75.1, with enableRpcTracePropagation: true

Summary

Since #24512, the RPC prototype wrapper instruments any prototype method called while the isolation scope is the default one, in a new trace. The wrapper is installed after construction, but a blockConcurrencyWhile callback started in the constructor runs after that, with no isolation scope. So a method the object calls on itself during initialisation is treated as an untraced RPC entry. If it throws, the error is captured as handled: false with mechanism auto.faas.cloudflare.durable_object, even when the object catches it.

Repro

class Store extends DurableObject {
  failure?: Error;
  constructor(ctx: DurableObjectState, env: Env) {
    super(ctx, env);
    void ctx.blockConcurrencyWhile(async () => {
      try { this.init(); } catch (e) { this.failure = e as Error; }
    });
  }
  init(): void { throw new Error('init failed'); }
  ping(): string { return this.failure ? 'degraded' : 'ok'; }
}

export const Instrumented = Sentry.instrumentDurableObjectWithSentry(
  (env) => ({ dsn: env.SENTRY_DSN, enableRpcTracePropagation: true }),
  Store,
);

Call ping() on a stub.

Expected: no error event. The error is caught inside the object.

Actual: one error event for init failed, handled: false, in its own trace.

Observed in real workerd (@cloudflare/vitest-pool-workers). With a raised Error.stackTraceLimit, the capturing frame is the untraced startNewTrace branch in durableobject.ts, wrapping the method called from the constructor's blockConcurrencyWhile callback.

Notes

Declaring internal methods as #private avoids it, because they are no longer on the prototype, and that matches Cloudflare's RPC visibility guidance (https://developers.cloudflare.com/workers/runtime-apis/rpc/visibility/). It may be worth either documenting that, or running constructor-time blockConcurrencyWhile callbacks inside an isolation scope so they are not mistaken for RPC entries.

[linear-code]

JS-3807