The rule scan cache stored a path[] keyed by (projectRoot|startDir|
skipClaudeUserRules), so two issues stacked up on every tracked tool
call:
- Cache hits still ran safeRealpathSync(realpathSync) and re-derived
isGlobal / distance / isSingleFile for every cached path. That is a
per-candidate sync syscall plus repeated string-prefix walks.
- Sibling files in the same project landed under different startDir
keys, so the entire walk-and-recursive-scan chain repeated even
though every ancestor rule directory was identical.
Store the full RuleFileCandidate[] in the per-call cache so a cache hit
returns immediately with no realpath syscall. Add a separate per-
directory scan cache (getDirScan/setDirScan) keyed by absolute rule
directory path, so two sibling files reuse the same readdir + realpath
work for every shared ancestor.
Microbench (200 files / 20 modules / cached session):
- single sweep: 41.8ms -> 2.5ms (16x)
- 3-pass replay: 88.6ms -> 3.2ms (28x)
Pin the new invariants with two new tests:
- 'does not re-resolve symlinked rule path on cache hit' via a
retargeted directory symlink.
- 'reuses ancestor directory scan for sibling files in the same
project' by deleting the source rule file between the two calls.
YeonGyu-Kim