Adam Perry @ OpenAI 6e7ab52929 [codex] Speed up local nextest runs (#26479) ...

## Why

`just test` currently uses the CI-oriented nextest profile, which
serializes app-server integration tests even on developer machines that
can run several safely. Bounded local parallelism substantially shortens
this common iteration loop without changing CI behavior.

Eight-worker experiments were faster, but keeping them reliable required
relaxing several test deadlines. Four workers for integration tests is a
solid tradeoff that speeds up local testing without needing to change
test logic.

## What changed

- Add a `local` nextest profile that inherits the existing defaults.
- Allow up to four app-server integration tests to run concurrently
under that profile.
- Make `just test` select the local profile on Unix and Windows.
- Keep the default CI profile serialized and leave all test deadlines
unchanged.

The tests use separate processes, randomized temporary `CODEX_HOME`
directories, and ephemeral ports. The remaining shared constraints are
system resources; each app-server also uses a multi-thread Tokio
runtime, and fuzzy-search tests can create additional worker threads, so
the local cap remains intentionally conservative.

## Performance and validation

All measurements below are warm, execution-only app-server runs with
nextest retries disabled.

On the current rebased branch, an AMD EPYC 7763 machine with 16 logical
CPUs and 62 GiB RAM completed three consecutive runs:

| Run | Nextest time | Wall time | Result |
| --- | ---: | ---: | --- |
| 1 | 142.941s | 145.17s | 836/836 passed |
| 2 | 143.402s | 145.59s | 836/836 passed |
| 3 | 142.870s | 145.08s | 836/836 passed |

The mean wall time was 145.28s. The slow-inventory, approval replay, and
zsh-fork tests all passed with their original deadlines.

Earlier measurements on the same Linux machine, before the suite grew,
showed the scaling that motivated the change:

| App-server concurrency | Nextest time | Result |
| --- | ---: | --- |
| 1 | 369.5s | 572/572 passed |
| 2 | 194.5s | 572/572 passed |
| 4 | 111.0s mean over 3 runs | 3/3 clean |

Four workers reduced that execution time by about 70%, a roughly 3.3x
speedup over serialization.

6e7ab52929 · 2026-06-09 12:48:04 -07:00

History

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nextest.toml

[codex] Speed up local nextest runs (#26479)

2026-06-09 12:48:04 -07:00