flake: TestProcessLifecycle/OutputExceedsBuffer

[flake-investigator]

CI Run: https://github.com/coder/coder/actions/runs/23549672835
Job: test-go-pg (windows-2022)
Commit: 239520f912088459b97c62e3d4ae9b5ab89e059f (Mathias Fredriksson)

Failure:

=== FAIL: agent/agentproc TestProcessLifecycle/OutputExceedsBuffer (0.52s)
    api_test.go:1181:
        Error Trace: C:/actions-runner/coder/coder/agent/agentproc/api_test.go:1181
        Error:       "0" is not greater than "0"

The test asserts resp.Truncated.OmittedBytes > 0, but on Windows the response reported OmittedBytes = 0 while still indicating Strategy = head_tail. This suggests the output length fell between MaxHeadBytes and MaxHeadBytes+MaxTailBytes (so no omitted bytes), or truncation metadata is being set even when omitted == 0. Likely Windows-specific command/output size behavior.

Race/Panic/OOM checks: No "WARNING: DATA RACE", panic, or OOM indicators in the job log.

Assignment analysis (no line-level blame tooling available):

• git log --oneline -10 --follow agent/agentproc/api_test.go
  • 41e15ae4 feat: make process output blocking-capable (#23312) — Mathias Fredriksson
  • 6edcbdba fix(agent/agentproc): enforce chat ID isolation... — Mathias Fredriksson
  • 119030d7 fix(agent): default process working directory... — Mathias Fredriksson
    The most recent substantive changes touching output handling/tests in this file are by Mathias Fredriksson, so assigning to Mathias for triage.

Related issues: none found in coder/internal for TestProcessLifecycle, OutputExceedsBuffer, or agent/agentproc/api_test.go.

Reproduction (Windows):

• go test ./agent/agentproc -run TestProcessLifecycle/OutputExceedsBuffer
• or make test with TEST_PACKAGES="./cli/... ./enterprise/cli/... ./agent/..."

Root cause classification: Flaky test / OS-specific output sizing in truncation metadata.