Lightweight, in-memory profiler for AppController init phases. Used by
the startup_speedup_20260606 track to measure where the time goes
during boot (config hydration, hook server start, subsystem init, etc.).
The profiler is exposed via /api/startup_profile (Phase 8 work) and
the Diagnostics panel so the user can see the exact per-phase cost.
Public API:
StartupProfiler() - create
.phase(name) - context manager
.snapshot() - {phases: {name: {start_ts, duration_ms}}, total_ms, count}
.reset() - clear recorded phases
.enable() / .disable() - toggle recording
Implementation:
- dataclass with list of _Phase(name, start_ts, end_ts)
- @contextmanager records wall-clock via time.perf_counter
- records duration even if the body raises (try/finally)
- snapshot is a copy, so consumers can't mutate the live state
TDD: 5 tests in tests/test_startup_profiler.py cover: basic
recording, total math, snapshot isolation, exception safety, empty
state.
ed
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