## What
Runs that carry no external trace context (schedules, task-to-task
triggers) fall back to a trace id generated once in the [`TracingSDK`
constructor](https://github.com/triggerdotdev/trigger.dev/blob/main/packages/core/src/v3/otel/tracingSDK.ts#L165).
With `experimental_processKeepAlive` the SDK outlives the run, so every
run on a warm process is exported to the external OTLP endpoint under
that one id.
Across our production traces, 80.3% contained spans from more than one
run, worst case 25. Per-run cost and latency attribution is unusable as
a result. This is the same warm-start hazard c043c4a6a fixed for the
external-context path, which left the fallback captured at construction.
## How
`FallbackExternalTraceIds` hands out one id per internal trace, shared
by the span and log wrappers so a run's spans and logs agree.
The id is keyed off the record's own internal trace id rather than
ambient state at export time, because batch processors drain
asynchronously and a run's records routinely export after the next run
has started. The map is bounded and evicts least-recently-used, so a run
that is still exporting can't lose its id.
Granularity follows the internal trace, so a run and the runs it
triggers stay on one trace.
**Risk:** the wrappers only exist when `exporters` / `logExporters` are
configured, so deployments that don't export externally are untouched.
Nothing outside `tracingSDK.ts` changes.
**Known gap (pre-existing):** sampling and id selection still branch on
ambient `getExternalTraceContext()`, so records draining across a run
boundary in mixed mode are misplaced in both directions. It can't use
the approach here — the external id comes from the run's incoming
`traceparent`, which isn't carried on the record — so closing it means
capturing `internalTraceId -> external context` in a span processor.
Happy to follow up separately.
---
## Testing
`packages/core` suite passes. `pnpm run format` and `pnpm run lint:fix`
produce no diff.
Six cases in `externalSpanExporterWrapper.test.ts`, each
mutation-checked rather than just observed passing: one id per run,
stability within a run, correct id when records drain after the next run
started (spans and logs together), external export stays off when
unconfigured, retention of a run still exporting while the map churns,
and the bound itself.
**CI:** the five failing `webapp` shards are the ones containing
`containerTest` suites. Fork PRs receive no repository secrets, so
`unit-tests-webapp.yml` skips the DockerHub login and the image pre-pull
(both gated on `env.DOCKERHUB_USERNAME`) and the container tests time
out at 60s. Same five shards across five runs, every failure a 60s
timeout, and those shards pass on internal PRs. Happy to be corrected if
you can run them with secrets available.
---
## Changelog
Unrelated runs are no longer merged into a single trace in your external
observability tool when they happen to execute on the same warm worker
process. A run and the runs it triggers still share one trace, so a run
tree stays together.
---
## Screenshots
_n/a_
---
_Supersedes #4526 (auto-closed before I was vouched) and #4533 (opened
ready rather than as a draft). GitHub won't reopen either._
---------
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-authored-by: Iss <74388823+isshaddad@users.noreply.github.com>
Co-authored-by: nicktrn <55853254+nicktrn@users.noreply.github.com>
Marcus Nerløe
b83cf671de