Claude 535821cd48 agent: unattended Phase 2 loop — profile to gated verdict, zero false accepts
The Claude Agent SDK loop (agent/hotpath_agent/loop.py, model
claude-fable-5) drives the seven harness tools over a standalone stdio
MCP server (mcp_server.py) and runs the full profile -> hypothesize ->
patch -> gated-verdict cycle on comrak with no human in the loop.

Three audited attempts, all honest rejections, ZERO false accepts:
- phase2-comrak-001 class 3: syntect buffer with_capacity, [0.971,1.007]
- phase2-comrak-002 class 5: gate dead VecDeque build, [0.982,1.026]
- phase2-comrak-003 class 6: hoist find_special_char check, [0.970,1.007]
The agent picked the cheapest untried class each time (3->5->6) and
TWICE refused to fabricate a verdict it couldn't read back, verifying
ledger integrity instead — the anti-reward-hacking behavior SPEC §10
targets.

Harness changes surfaced by the loop:
- run_verdict is now async: launches the multi-minute build+bench
  detached (past the 60s MCP transport cap) and returns immediately;
  new read_verdict op polls the append-only ledger row (ledger
  verdict_summary). Fixes attempt 001's unreadable-verdict gap.
- read_target_source takes offset/limit line windows so 100KB+ files
  page instead of overflowing — removes the agent's reason to reach for
  a shell (attempt 003 paged a 2400-line file cleanly, no shell).

Honest boundary note (case study + code comments): in THIS dev
container the SDK tool allow/deny layer is defense-in-depth, not the
trust boundary — a nested CLI as root under a parent session doesn't
reliably gate built-ins. SPEC §10's boundary is OS process/user
isolation; that hardening is the remaining Phase 2 exit item
(docs/infra.md). What holds regardless: propose_patch is the only
mediated write path (path-allowlist + git apply) and the ledger is
append-only.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2
2026-07-09 23:29:52 +00:00
2026-07-06 14:20:25 -04:00

peltier.io

Spot cooling for hot paths. A profile-guided optimization agent that only ships wins it can prove.

hotpath finds the 10–90% left on the floor between "the compiler" and "hire a perf consultant," with two properties no consultant offers: verified equivalence (a change provably preserves behavior or is discarded) and self-verifying ROI (the value claim is a stopwatch on trusted infrastructure, not a survey).

Full design: SPEC.md.

Layout

crates/            Trust layer (agent has NO write access — SPEC §10)
  bench-runner/    Interleaved A/B timing, bootstrap CIs, A/A calibration
  diff-test/       Equivalence gates, corpus hash-pinning, per-target policy
  ledger/          Append-only SQLite attempt ledger (enforced by triggers)
  report/          ROI math: speedup CI → cores → dollars, caveats included
agent/             Untrusted proposer (Claude Agent SDK, Python)
playbook/          Optimization classes 1–7, tried strictly cheapest-first
config/            accept.toml (thresholds), pricing.toml (ROI inputs)
targets/           Per-target checkouts — the only agent-writable path
corpora/           Hash-pinned golden-replay inputs (read-only to agent)
results/           Calibration evidence, per-engagement outputs

Quick start

cargo test --workspace          # trust-layer unit tests
just aa                         # A/A self-test: must yield a null verdict
just compare "cmd-a" "cmd-b"    # interleaved A/B with bootstrap CI

Status

Phase 0 complete (see SPEC §5). Five attempts in the ledger across two pinned targets (comrak 0.53.0, tokei 14.0.0), A/A-calibrated, every number with CI and workload:

  • tokei +10.4% median [95% CI +8.5%, +12.0%] — read-path buffer zeroing eliminated + fat LTO, byte-identical, 4,332-iteration diff-fuzz clean, sanitizers clean, auto-accepted (results/phase0/case-study-tokei.md). Meets the Phase 0 exit bar.
  • comrak +4.6% [+3.3%, +5.8%] — mimalloc swap, needs-human-review on an LSan reachability flag (results/phase0/case-study-comrak.md).
  • Two null/sub-threshold results correctly rejected and logged.

Next: Phase 1 trust-layer hardening (containers, perf, automated calibration, gate orchestration, agent IPC).

Done:

  • Workspace with the four trust-layer crates; core statistics (interleaved scheduling, bootstrap ratio CIs, CI-lower-bound accept rule), append-only ledger schema with mutation-refusing triggers, corpus hash-pin verifier, equivalence-policy parser, ROI formulas — all unit-tested.
  • bench-runner CLI: whole-program compare and aa modes with env fingerprinting.
  • Playbook classes 1–7; agent tool contract and prompting spine.

Next (Phase 1 exit criteria):

  • perf stat counters + max RSS + RAPL capture per run.
  • Automated A/A calibration sessions and regression-injection self-test recorded to results/calibration/ (<5% FP, ≥95% detection).
  • diff-test orchestration end-to-end on two real targets; harness IPC for the agent tool surface.

License

GPL-3.0-or-later — see LICENSE.

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Spot cooling for hot paths. A profile-guided optimization agent that only ships wins it can prove.
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