[danlapid]

Depends on cloudflare/workerd#7686.

Spans are going away from streaming tail events. cloudflare/workerd#7686 lets workerd export each invocation's spans itself, as OTLP, through a new tracing.otlp config setting. This moves Miniflare's local observability (unsafeObservability) onto it:

• Spans over OTLP. Miniflare sets tracing.otlp to the observability collector. Its new POST /v1/traces decodes workerd's protobuf export (a small reader for the fields workerd sets, no new dependency) and stores the spans. They carry precise timestamps instead of the coarse I/O time tail events report.
• Logs stay on the streaming tail. The tail handler now handles only logs, exceptions, and the per-invocation log. tail_worker_user_spans is no longer enabled. Logs still reference spans correctly: the tail events carry the same span IDs workerd exports.
• Only the user's spans are kept. tracing.otlp traces every service in the config, including Miniflare's own Workers (the entry Worker, simulators, queue brokers, …). The collector receives a map from workerd service name to worker name: user workers, plus the Workflows services that run their workflows. It keeps only those services' spans. This map replaces the per-tail props that used to carry the worker name.
• Roots stay roots. Dropping Miniflare's spans would leave, for example, an invocation that came through the entry Worker pointing at a parent that is never stored. The store keeps a span whose parent is missing as a root and parks the parent in a pending_parents table. If the parent arrives later, the span is attached to it again. That happens when one user worker calls another, because the callee usually finishes and is exported first. So distributed traces across user workers still join up.

The config types in src/runtime/config/generated/workerd.ts are regenerated from the workerd schema in #7686 (the only difference is the new tracing field). This can't merge until a workerd release that includes #7686 is published and Miniflare's workerd dependency is bumped: with today's workerd, tracing is ignored and no spans are captured. Until then, CI fails the tests that need captured spans: the four capture tests in test/plugins/core/observability.spec.ts and "captures the selected same-instance Worker in Observability" in test/plugins/local-explorer/scheduled.spec.ts.

While tracing.otlp is set, workerd stops delivering spans to streaming tail workers, so with local observability on (the default) a streaming tail worker configured locally no longer receives spanOpen/spanClose. That's intended: spans on streaming tail workers are being deprecated in local dev and production alike, and users can't deploy streaming tail workers.

A failed span's error column is its last exception (workerd records uncaught exceptions on the invocation span), else its status message, else its error.type, so a span that failed without an exception, such as a 5xx fetch, still counts as an error.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: unsafeObservability is an unsafe, undocumented option, and what the Local Explorer shows is unchanged.

Tested against workerd built from #7686 (MINIFLARE_WORKERD_PATH): test/plugins/core/observability.spec.ts, test/plugins/local-explorer/, test/plugins/workflows/, test/plugins/core/ and test/index.spec.ts all pass. New tests cover parent re-linking in the store and dropping Miniflare's own spans.

🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: f3f9d28

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
miniflare	Minor
@cloudflare/deploy-helpers	Patch
@cloudflare/pages-shared	Patch
@cloudflare/remote-bindings	Patch
@cloudflare/runtime-types	Patch
@cloudflare/vite-plugin	Patch
@cloudflare/vitest-plugin	Patch
wrangler	Patch

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commit: f3f9d28