[codex] Stabilize skippy smoke chain startup

[i386]

Summary

Stabilizes the PR Linux tests (skippy-smoke) lane by balancing the dense 3-stage smoke split and making dense chain startup timeout configurable.

Why

Several unrelated PRs have failed with stage 2 binary server did not become ready. The old default dense split 1,2 leaves stage 2 owning nearly the full 30-layer smoke model, so startup can exceed the fixed 60s readiness timeout on current GitHub runners.

Details

• Leaves DENSE_SMOKE_SPLIT_1 / DENSE_SMOKE_SPLIT_2 override support intact.
• When unset, computes roughly one-third/two-third balanced splits from the inspected dense layer count.
• Adds DENSE_CHAIN_STARTUP_TIMEOUT_SECS, defaulting to 180, and passes it to skippy-correctness chain.

Validation

• bash -n scripts/skippy-ci-smoke.sh
• git diff --check

Summary by CodeRabbit

• Chores
  • Enhanced smoke testing infrastructure with flexible split boundary configuration that no longer enforces default values
  • Introduced configurable startup timeout for chain operations, replacing hardcoded value (default: 180 seconds)

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: a8ae9425-b23b-4288-a40c-417b5416fb86

📥 Commits

Reviewing files that changed from the base of the PR and between 39cd7d2 and 9bd68ca.

📒 Files selected for processing (1)

• scripts/skippy-ci-smoke.sh

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📝 Walkthrough

Walkthrough

This script update makes dense chain smoke test configuration more flexible by replacing hardcoded defaults with optional environment-driven values. Dense split boundaries now compute automatically if not explicitly set, and startup timeout becomes configurable instead of hardcoded to 60 seconds.

Changes

Dense Chain Smoke Test Configuration

Layer / File(s)	Summary
Dense split boundary configuration and selection logic scripts/skippy-ci-smoke.sh	DENSE_SMOKE_SPLIT_1 and DENSE_SMOKE_SPLIT_2 default to unset, triggering conditional logic: explicit values are used directly if both are provided; otherwise balanced split points are computed from DENSE_LAYER_END with validation clamping.
Startup timeout configuration usage scripts/skippy-ci-smoke.sh	New DENSE_CHAIN_STARTUP_TIMEOUT_SECS variable (default 180) replaces the hardcoded 60-second timeout in the dense chain correctness invocation.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: configuring dense chain startup to stabilize CI smoke tests by balancing splits and making timeout configurable.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/skippy-smoke-balanced-splits

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[michaelneale]

Interesting wonder why it has to be flexible with this now