feat(criteria): make async the primary criterion-checking surface

[akshaylive]

Summary

Redesign of the fix for #55, replacing PR #58. That PR made judge criteria (llm_judge/agent_judge) concurrent by bolting an async path onto a sync-first BaseCriterion — each judge checker ended up with two near-duplicate implementations (a sync client + an async client) plus a supports_native_async marker flag to tell SuccessChecker which path to dispatch through. This PR inverts that relationship instead of layering on top of it:

• BaseCriterion._check_impl_async is now the primary implementation surface. A checker overrides exactly one of _check_impl (sync) or _check_impl_async (async) — whichever is its natural form — and the base class derives the other automatically:
  • CPU/file-bound checkers (file_exists, command_executed, ...) keep overriding _check_impl only; the default _check_impl_async offloads it via asyncio.to_thread.
  • llm_judge/agent_judge now override only _check_impl_async, using AsyncAnthropic, httpx.AsyncClient, and a new SubAgentRunner.run_async — no sync client duplicated. The default _check_impl derives a sync call via asyncio.run(...) for any caller that still wants one (tests, etc.).
• register_criterion enforces that a checker overrides at least one of the two (overriding neither would recurse forever between the defaults).
• SuccessChecker.check_all_async no longer needs an explicit "is this checker async-native" flag — it detects it by introspecting whether _check_impl_async is overridden, then gathers those checkers concurrently with each other while the remaining sync checkers still share one asyncio.to_thread slot (unchanged behavior for the 12 non-judge criteria).
• SubAgentRunner.run() (sync) is removed — nothing calls it anymore now that agent_judge is async-only; run_async() is the sole entrypoint.

Net effect on behavior is identical to #58 (judge criteria run concurrently instead of serializing, and don't pin a thread-pool thread for the network wait) — this PR just gets there with one implementation per criterion instead of two.

Test plan

• make check / make typecheck / make lint clean
• make verify — 3582 passed, 2 skipped, 90.99% coverage
• tests/test_check_all_async.py — judge criteria overlap instead of serializing, sync/async batches overlap, ordering preserved, error handling parity, _is_native_async detection, register_criterion guard, and direct sync↔async derivation on BaseCriterion
• tests/test_judge_anthropic.py / tests/test_judge_bedrock.py rewritten against the async invokers
• tests/test_sub_agent_runner.py converted to run_async

Closes #55 (supersedes #58 — closing that PR in favor of this one)

🤖 Generated with Claude Code

[akshaylive]

Addressed the review across two commits (7dcb8b6 → d4e6f87):

Blockers

• Override contract enforcement moved to BaseCriterion.__init_subclass__ (fires at class-definition time on every subclass, not just via register_criterion) — closes the CriterionRegistry.register bypass, turns the mutual-recursion failure mode into an immediate, clear TypeError.
• handle_criterion_errors(_async) re-typed with PEP 695 ParamSpec + Concatenate instead of Callable[..., ...] — no longer erases the checked method's signature.
• check_all_async's sync batch now runs to completion before the native-async (judge) batch starts, instead of overlapping — closes the sandbox-mutation-vs-judge-read race (run_command/uipath_eval writes vs. llm_judge/agent_judge reads). Judges still run concurrently with each other, which is the actual GH Judge criteria (llm_judge/agent_judge) serialize and pin threads during check_all #55 fix.
• The native-async gather now uses return_exceptions=True and re-raises only after every sibling settles — a JudgeInfrastructureError no longer orphans sibling judge work (e.g. an agent_judge sub-agent left running against a sandbox already being torn down).
• Closed the three lost test guards: native-async dispatch is now pinned against the real registered llm_judge/agent_judge; test_registry's context-kwarg check now inspects whichever of _check_impl/_check_impl_async is actually overridden; check_all_async's reference_code/reference_dir persistence has a regression test.

Non-blocking / nits

• llm_judge/agent_judge now offload JudgeContextBuilder.build() (sandbox file reads) via asyncio.to_thread instead of blocking the event loop directly.
• SubAgentRunner's finally-block cleanup is a plain synchronous shutil.rmtree instead of an awaited to_thread call, so cancellation (task_timeout watchdog) can't skip it; added a cancellation regression test.
• _is_native_async now classifies via the registered class (CriterionRegistry.get_checker) instead of a constructed instance, so a checker-constructor failure can't escape the per-criterion error boundary.
• Collapsed the _check_single/_check_single_async duplication and the triplicated reference-persist preamble into shared helpers.
• Replaced the two wall-clock-timing concurrency assertions with a deterministic rendezvous barrier / ordered event markers, and added an end-to-end regression test with the real run_command + llm_judge checkers proving the sequencing fix.
• Fixed stale docstrings (old invoke_*_judge names, check_all vs check_all_async) and lightly documented the dual-surface contract in docs/EXTENDING.md / CLAUDE.md.

Deliberately not done — flagged as new repo-wide tooling/policy investments rather than defects in this diff, better suited to a follow-up issue: the ~13 new CE0xx lint rules, dropping tests/ from the pyright exclude, reportImplicitOverride/reportUnnecessaryTypeIgnoreComment pyright config, ruff PGH selection, a diff-cover patch-coverage gate, a duplicate-code detector step, and a global judge-concurrency semaphore for nightly runs (task-level --max-parallel already caps total fan-out; this PR's added concurrency is only across one task's own 1-3 judge criteria).

make verify (3587 passed, 91.04% coverage) and make lint are green on both commits.

[akshaylive]

Addressed the second review pass (commit a91cf5c → 23929f4).

Blockers fixed

• Declaration-order regression: check_all_async now splits criteria into maximal contiguous runs of the same kind (sync vs native-async) and executes the runs strictly in declaration order, instead of always running the whole sync batch before any async criterion. [llm_judge, run_command] used to invert order (judge always ran after run_command regardless of being declared first, silently grading post-mutation state) — a real scoring bug. Adjacent judges within one run still gather concurrently, which is the actual GH Judge criteria (llm_judge/agent_judge) serialize and pin threads during check_all #55 fix. Added a real end-to-end regression test (real llm_judge + run_command checkers) covering the reversed order, plus the already-existing forward-order test.
• Judge-sandbox cancellation leak: SubAgentRunner.run_async's mkdtemp/copytree are no longer plain asyncio.to_thread awaits (not cancellable — a cancellation mid-copy could leave an orphan thread that recreates files after finally's rmtree already ran). judge_dir is now bound with a synchronous tempfile.mkdtemp (one syscall), and the copy/rmtree calls are asyncio.shielded + tracked so finally awaits them to completion before cleaning up. Reproduced the leak, confirmed the fix closes it, and added a cancel-mid-copytree regression test. Applied the same fix to simulation/user_simulator.py's scratch-dir teardown (same class of bug, previously only fixed in sub_agent.py).
• Silent 0.0 from a running loop: the derived sync _check_impl (asyncio.run bridge) now detects a running event loop and raises a new CheckerMisuseError (escalates like JudgeInfrastructureError) instead of letting asyncio.run's RuntimeError get swallowed into a scored-0.0 result — a library/embedder calling the public sync check()/check_all() on an async-only checker from async host code now gets a loud, named error instead of a wrong score.

Contract/API-surface follow-ups

• __init_subclass__ now enforces "exactly one", not just "at least one" — overriding both _check_impl/_check_impl_async is also rejected. Added an abstract=True escape hatch for intentional abstract intermediate bases, and a __new__ guard so BaseCriterion itself can't be instantiated directly.
• Promoted the native-async check to a public, typed BaseCriterion.is_native_async() classmethod instead of comparing _check_impl_async identity across package boundaries; check()/check_async() are now @typing.final; extracted the duplicated error-capture tail in handle_criterion_errors/_async into one shared helper.
• Fixed the two inert TestNativeAsyncDetection tests (they injected into _checker_instances, which classification never reads) to actually exercise class-based dispatch via the registry; added a checker-__init__-failure test (closes the last uncovered branch); added one check_all_async happy-path test each for llm_judge/agent_judge (production's real entry point); fixed stale check_all mentions in CLAUDE.md/early_stop.py/reports.py/orchestrator.py.

make verify is green: 3600 passed, 91.08% coverage.

Deliberately not implemented — the "Harness & Lint Improvements" follow-up comment proposed ~8 new CE0xx lint rules (CE034–CE041), several scoped pyright/ruff config changes (reportPrivateUsage execution environments, S101, dropping tests/ from the pyright exclude), a diff-coverage gate, and a nightly mutation-testing job. I didn't implement these: they're net-new, repo-wide tooling/CI investments rather than defects in this diff's code — landing 8 new lint rules and CI policy changes inside a bug-fix PR would meaningfully expand its blast radius and review surface beyond what it's actually fixing. I did fix every underlying code defect those rules were designed to catch (contiguous-run ordering, shielded cancellation-safe cleanup, CheckerMisuseError, both-overridden rejection, is_native_async(), @final, shared error-tail helper, dict-based total materialization instead of assert+cast). Happy to file the lint-rule/CI proposals as follow-up tracked issues if useful, but think they're better scoped as their own PRs.