[aviggiano]

Summary

• Fix durable eval journal append behavior and fail closed on incomplete durable appends.
• Bound new public Modal sandbox lifetimes while preserving retry/history provenance from Preserve retry cost, timing, and history provenance #429.
• Use six hours for smoke and sixteen hours for full runs so the bound remains below the historical 24 hours without undercutting the full EVMBench worker envelope.

Closes #382
Closes #422

Validation

• Artifacts tests: 89 passed
• Evals tests: 182 passed
• Modal tests: 394 passed
• Modal typecheck, touched-file lint, and format checks passed
• Root build, typecheck, lint, and format check passed before the timeout-envelope follow-up

Greptile Summary

The PR makes eval-journal appends durable and preserves fail-closed handling of incomplete records. It also bounds new public Modal sandboxes to six hours for smoke runs and sixteen hours for full runs while retaining persisted lifetimes across retries and resumes.

• Adds checked writes plus file and directory synchronization for durable JSONL appends.
• Selects public sandbox lifetimes according to benchmark lane.
• Records the selected lifetime in launch state and reuses it for sandbox creation.
• Adds coverage for durability failures, timeout selection, provenance, and the full-lane execution envelope.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
packages/artifacts/src/safe-paths.ts	Durable appends now detect short writes, synchronize the file and containing directory, and preserve operation and close errors.
packages/evals/src/utils.ts	Eval JSONL journals now use the shared durable append implementation.
packages/modal/src/config.ts	New launch generations select six-hour smoke, sixteen-hour full, or historical private sandbox lifetimes.
packages/modal/src/defaults.ts	Defines bounded public sandbox lifetimes, including a full-lane limit above the checked-in worker envelope.
packages/modal/src/runner.ts	Launch state records the configured lifetime and primary sandbox creation consistently uses the persisted value.

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