Rebuild CHANGELOG.md files and release histories from git, tags, releases, and issue trackers. Use when writing changelogs, version timelines, or agent-facing project history summaries.

Golden artifact test suites that freeze known-good outputs and catch regressions through exact comparison. Use when: snapshot testing, approval testing, compiler output validation, query plan verification, UI snapshots, CLI output regression, or serialization format stability. Supports insta (Rust), jest snapshots, golden file workflows, scrubbing, canonicalization, and multi-format goldens.

Run Lean-Rust proof feedback loops to find runtime bugs. Use when proving theorems, triaging hard proof blockers, checking conformance, or closing formal assurance gaps.

Build conformance test harnesses that verify implementations against specifications. Use when: porting libraries across languages, implementing RFCs/specs, building database engines, validating protocol compliance, cross-platform compatibility, API contract testing, golden file testing, round-trip validation, compliance matrices, differential testing against reference implementations.

Debug running processes with GDB, strace, and /proc inspection. Use when: process hang, spin loop, segfault, crash, backtrace, attach debugger, ptrace, core dump, thread starvation, accept loop, deadlock, busy wait, or diagnose why a process is stuck.

Build mock-free integration and E2E tests that hit real databases, real APIs, and real services with structured logging. Use when: replacing mocked tests with real-DB tests, transaction rollback isolation, test data factories, structured JSON-line test logging, webhook simulation, or billing flow verification. Covers Vitest, Supabase, Stripe test mode, and testcontainers.

Find stubs, mocks, placeholders, TODOs, and fake code in a project. Use when "find mocks", "find stubs", "find placeholders", "check for fake code", or auditing for incomplete code.

Shrink and unify code without changing behavior. Use when: simplify, refactor, reduce duplication, remove lines, extract helper, reuse component, DRY, collapse, better abstraction.

Rank hot paths by CPU, memory, I/O, and contention; hand the optimization skill a scored target list. Use when: profile, flamegraph, hotspot, bottleneck, p95/p99, IOPS, fsync, "why is this slow".