[TheGreatAxios]

Summary

toolSetDigest (src/agent/director.ts) re-hashed the full tool array on every call. Memoize the digest per stable tool-set identity.

Fix approach — cache semantics

• Cache is a module-level WeakMap<readonly ToolDefinition[], string> keyed by array identity.
• Why this is safe: the director owns stable tool arrays and swaps them wholesale (constructor, updateToolDefinitions) — callers pass freshly computed arrays (computeAdvertised, currentDefinitions) and _toolDefinitions is never mutated in place. So the same reference always means the same content, and a new reference (tools changed) misses the WeakMap and recomputes.
• WeakMap (not Map) so cached arrays are not retained once the director drops them.
• Output is byte-identical for the same tool set; existing digest tests pass unchanged.

Proof test

src/agent/tool-set-digest.test.ts spies on node:crypto createHash (via withMockedModule from testkit/mock-module.ts) and asserts:

• 3 repeated toolSetDigest(tools) calls with the same array run sha256 exactly once.
• A new tool-set array runs it again (recompute on change).

Verification

• bun test src/agent/director.test.ts src/agent/director-compaction.test.ts src/agent/tool-set-digest.test.ts → 93 pass, 0 fail
• bun run typecheck → exit 0
• oxfmt --check + oxlint on changed files → clean
• pre-commit (typecheck + build) → ok

Diff stat

 src/agent/director.ts              | 13 ++++++++++++-
 src/agent/tool-set-digest.test.ts  | 53 ++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)

[linear-code]

CL-10536

[corbits-triage]

No changes needed from you. A maintainer will review this pull request.

[TheGreatAxios]

Review · Comment

Memoizes toolSetDigest on the director. Incoming tool sets are hashed when installed; the previous digest is an instance field used only to skip a repeat debug log.

Findings

No findings. bun test src/agent/tool-set-digest.test.ts src/agent/director.test.ts — 88 pass, 0 fail.

Commit bodies on this branch wrap past 72 characters and walk the implementation (perf(agent): memoize toolSetDigest per director, not per module). Subjects are within the limit. Not a code defect.