`--changed` / `--changed-files` now narrow each harness's recorded Rust
sources to those its probes can reach (tools/parity_reach.py): an item-level
reachability walk from the probe modules a harness ran (or the binary it
built) over free items, inherent methods, trait impls and macros, matched by
name so it only over-approximates. Parent modules count through their `mod`
declarations, compared with the merge base. A harness whose probe can't be
placed keeps every source; `--by-crate` turns the narrowing off.
On the last 20 PRs merged on 2026-10-25: 2255 -> 1061 harnesses picked,
2384 -> 1592 harness-minutes. Replaying the week's 61 failed CI parity runs,
every failed harness the old selection picked is still picked; LLVM coverage of
six harnesses' probes executes only kept files.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Ludovic Marie
21d8e53034