Files
PaperClipAI/doc
Nicky LeachandClaude Opus 5.5 232480d18f perf(runner): write preparation span rows to the run log in the background (#20426)
## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - Before a native run starts its provider, the executor copies the
preparation spans (queue, prepare phases, environment) into the run
trace and the run log
> - It records about 25 spans and waits for one run-log insert per span,
one after another
> - On a hosted test deployment, that step
(`native.controller.span_persistence`, added in #20396) took a median of
0.28 s, and every task waited for it before the Runner started
> - The run trace already has a way to write diagnostics without
blocking the caller: `defer`, which `finish` drains before the root span
closes
> - This pull request writes those run-log rows through that path, in
order, while the spans themselves are still recorded at once
> - The benefit is about 0.25 s less before the provider starts, on
every native run, cold or warm

## Linked Issues or Issue Description

**What existing behavior does this improve?**
The time between the end of heartbeat preparation and
`native.session.execute` for native Runner tasks.

**Subsystem affected**
Server: native runtime tracing
(`server/src/services/native-runtime/native-run-trace.ts`) and the
native session executor.

**Current behavior**
`executeNativeSession` calls `trace.record` for each preparation span
and awaits it. `trace.end` awaits `emitCompletedSpanEvent`, which
inserts one `run.performance.span` row through `onEvent`. On a hosted
test deployment, measured with the #20396 spans across 10 runs,
`native.controller.span_persistence` took a median of 0.28 s:
- 0.30 to 0.36 s for runs right after a computer wake
- 0.17 to 0.25 s for runs on an awake computer

It is the second largest step between preparation and the provider start
(the median of that whole gap is 1.0 s).

**Proposed behavior**
The spans are still started and ended at once, with the same parents.
The speed-budget bookkeeping still runs at once too. Only the run-log
row is written later: one row at a time, in the order the spans ended,
before the trace finishes.

**Reason and benefit**
The rows are diagnostics, and they already carry their own start time
(`wallStartedAtMs`, `startOffsetMs`). Readers do not depend on the row
order: the only reader in the repository, `summarizeStartupReuse`, looks
for `runner.process.launch`, which this change does not defer. The
provider can start without waiting for these inserts.

**Breaking changes**
None.

## What Changed

- `native-run-trace.ts`: `end` and `record` take an optional
`deferRunLog`. With it, `end` queues the run-log row on a per-trace
chain registered with `defer`, so rows are written one at a time in
order and `finish` waits for them. A row requested after the trace
finished is dropped, as for other deferred diagnostics.
- `native-session-executor.ts`: the preparation spans and the
`environment.startup` scope use `deferRunLog: true`.
- `doc/run-log-events.md`: note that native preparation span rows are
written late, in order.
- `native-run-trace.test.ts`: two tests.
- Spans are recorded under their parent while every row write is
blocked, and the rows are written in order before
`task.provider_session.measured`.
  - A deferred row requested after `finish` is not written.

## Verification

- `npx vitest run src/services/native-runtime/native-run-trace.test.ts
src/services/native-runtime/native-run-trace-context.test.ts` (34
passed). Both new tests fail without the source change: the first times
out waiting on the blocked write, and the second sees the row written.
- `npx vitest run src/__tests__/heartbeat-preparation-gap-spans.test.ts
src/services/native-runtime/native-session-executor.test.ts` (1321
passed)
- `pnpm --filter @paperclipai/server typecheck`

## Risks

- Low risk. The change is diagnostic only: OpenTelemetry spans and the
speed-budget checks are unchanged.
- The preparation rows can now land in the run log after the first
Runner events. Readers already use the payload times, not the row order.
- If the server process dies between the provider start and `finish`,
the preparation rows of that run can be missing from the run log. The
OpenTelemetry spans are not affected.
- The deferred rows are written while the run continues, as
budget-breach rows already are, so the sink sees concurrent writes from
one run. This was already the case for deferred diagnostics.

## Model Used

- Claude Opus 5.5 (`claude-opus-5-5`), Anthropic, used through Claude
Code with tool use (shell, file edits, test runs, Honeycomb queries) and
extended thinking.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] All Paperclip CI gates are green
- [x] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
2026-11-09 17:50:15 -08:00
..
…
…
…
…
…