Doc Indexer Fixture Isolation

• Status: Accepted
• Date: 2026-08-04

Motivation

The doc-indexer test helper derived temporary directory names from wall-clock nanoseconds and then reused an existing path through create_dir_all. Parallel or repeated same-process tests could therefore share fixture state.

Design Notes

• Locate the repository through the canonical AGENTS.md file.
• Combine the process id with a process-local atomic sequence.
• Reserve each fixture root atomically with std::fs::create_dir.
• Retry only AlreadyExists; propagate every other filesystem error.

Test Coverage Summary

• cargo test -p revaer-doc-indexer
• just lint
• just ci
• just ui-e2e

Observability Updates

No production logs, metrics, or events change because this is test-only fixture isolation.

Risk And Rollback Plan

The sequence is process-local, while the process id separates concurrent test processes. The atomic directory reservation remains the authoritative collision check. Roll back this ADR and helper change together if the test harness adopts a repository-standard temporary-directory abstraction.

Dependency Rationale

No dependencies were added; the implementation uses std only.

Stale-Policy Check

Reviewed AGENTS.md and .github/instructions/rust.instructions.md. The stale AGENT.md repository-root sentinel was corrected; no other drift was found.