refactor: promote steer injection to a first-class pydantic-ai capability - #828
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mpfaffenberger wants to merge 2 commits into
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refactor: promote steer injection to a first-class pydantic-ai capability#828mpfaffenberger wants to merge 2 commits into
mpfaffenberger wants to merge 2 commits into
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…lity The Ctrl+T mid-turn steering injector was a closure-based history processor wrapped in ProcessHistory. Rewrite it as SteerInjection, a proper AbstractCapability subclass in harness house style (dataclass, injectable drain/mirror seams, get_serialization_name -> None). It overrides before_model_request directly -- the exact seam ProcessHistory uses -- so registration order against the compaction capability is unchanged: compaction first, then steering, so a fresh steer can never be compacted away on the same call. Feature parity preserved: - drains ONLY now-mode steers (queue-mode stays with the runtime loop) - carries in-effect instructions onto injected requests - resolves attachments via resolve_steer_content - one discrete ModelRequest per steer, appended after existing messages - mirrors injections into agent._message_history for durability - emits the same observability message per steer New unit suite tests the capability contracts directly; the wiring guard and smoke tests in test_runtime_pause_leakage.py updated to the capability seam.
…lity chain Reviewer follow-up: the unit suite exercised the hook through a duck-typed context. Add a TestModel-backed Agent.run() test proving the framework dispatches before_model_request and that the injected steer persists into result.all_messages().
This was referenced Aug 21, 2026
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What
The Ctrl+T mid-turn steering injector (
_steer_processor.py) was a closure-based history processor wrapped inProcessHistory. This PR rewrites it asSteerInjection, a genuineAbstractCapabilitysubclass in pydantic-ai-harness house style — dataclass, injectabledrain/mirrorseams,get_serialization_name() -> None(not spec-serializable: seams take callables).Module renamed
_steer_processor.py→_steering.pyto match its promotion.Why
capabilities=[...]; steering was the odd one out hiding behind the genericProcessHistoryadapter.drainandmirrorcallables instead of reaching for globals +agent._message_historyfrom inside a closure — unit tests no longer need the global pause controller.SteerInjection.before_model_requestis the exact hookProcessHistoryuses internally, so compaction-then-steering registration order is byte-for-byte preserved (a fresh steer still can't be compacted away on the same call).Feature parity checklist
now-mode steers (queue-mode stays with the runtime's between-turns loop — no double-inject)resolve_steer_content(steer with a pasted screenshot Just Works)ModelRequestper steer, appended AFTER existing messagesagent._message_historyfor durability across the turn boundaryemit_infoper steerTesting
tests/agents/test_steering_capability.py— 10 contract tests on the capability directly (no-op on empty queue, ordering, instruction carry, mirror behavior, now-vs-queue isolation, native-async hook)test_runtime_pause_leakage.pytests/agents/+tests/plugins/test_steer_queue.py: 423 passedruff check+ruff formatcleanDo not merge yet — under agent review.