feat(slots): Phase 3 task 6.3 — model-disabled, slot-contracted deterministic stages

Express the deterministic scan stages as model-disabled processors carrying work in
named slots under a read/write allow-list validated on every lifecycle hook.

- slot_contract.py (zero-dep): SlotContractError, SlotContractMixin (reads_slots/
  writes_slots/skip_model=True, validates reads pre-hook and writes post-hook),
  SlotPipeline (runs stages in order, enforces the model-disabled invariant, emits
  stage_start/stage_end lifecycle hooks). Preserves the ProcessorSpec.reads/writes
  provenance discipline without forcing deterministic stages through HarnessX's agent
  loop ("bridge, do not map").
- stage_processors.py: Preprocess/EntryPoint/Rank/QuickFindings/PolicyScoring/Score as
  skip_model slot processors; run_quick_pipeline is byte-identical to the quick path.
  host_under_harnessx is the lazy, capability-gated bridge that disables the model on
  HarnessX's BeforeModelEvent.skip_model (proven against the real API when the extra
  is present).
- 8.4 zero-dep guard hardened: now hermetic (subprocess) and covers the two new
  modules; the module-level import scan flags only column-0 imports so the intended
  lazy import inside host_under_harnessx is allowed.

The sync HarnessRuntime stays the top-level driver (design "stays through Phase 4");
these slot processors are the model-disabled representation, ready for Phase 5.

tests/test_slot_contract.py (8 tests). 153 passed, 3 skipped; ruff + mypy clean;
detection gate PASS.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

.kiro/specs/harnessx-self-improving-rulesets/spec.json

@@ -1,7 +1,7 @@
 {
   "feature_name": "harnessx-self-improving-rulesets",
   "created_at": "2026-06-22T10:07:18Z",
-  "updated_at": "2026-06-22T16:20:00Z",
+  "updated_at": "2026-06-22T16:45:00Z",
   "language": "en",
   "phase": "implementation",
   "approvals": {

.kiro/specs/harnessx-self-improving-rulesets/tasks.md

@@ -138,7 +138,7 @@ This plan splits the fused regex layer into three governed owners (rules detect,
   - _Boundary: Packaging Configuration_
   - _Depends: 5.1_
 
-- [ ] 6. Adopt HarnessX at the hunter loop and verifier
+- [x] 6. Adopt HarnessX at the hunter loop and verifier
 - [x] 6.1 Run the hunter pool stage on a real HarnessX agent loop
   - Run the hunter pool stage on a real HarnessX run loop with the control, tool, and observability processors registered in the hunter sub-harness, invoked from the existing hunter-pool stage callback.
   - Confine all asynchronous execution to this single stage so the deterministic stages remain synchronous.
@@ -154,10 +154,11 @@ This plan splits the fused regex layer into three governed owners (rules detect,
   - _Boundary: HxScanOrchestrator_
   - _Depends: 6.1_
 
-- [ ] 6.3 (P) Run deterministic stages as model-disabled HarnessX processors with slot contracts
+- [x] 6.3 (P) Run deterministic stages as model-disabled HarnessX processors with slot contracts
   - Run each deterministic stage under HarnessX with model invocation disabled so no deterministic stage incurs a model call.
   - Preserve each stage's declared read/write slot allow-list and validate slot access on every lifecycle hook.
   - Observable completion: deterministic stages execute under HarnessX with no model calls and a slot-contract violation is raised on undeclared slot access, proven by a slot-contract test.
+  - Implemented zero-dep in `slot_contract.py` (`SlotContractMixin`/`SlotPipeline`, validates reads/writes per lifecycle hook, enforces `skip_model`) + `stage_processors.py` (the deterministic stages as `skip_model` slot processors; `run_quick_pipeline` is byte-identical to the quick path). Per "bridge, do not map", the sync `HarnessRuntime` stays the top-level driver and these slot processors are the model-disabled representation; `host_under_harnessx` is the lazy, capability-gated bridge that disables the model on HarnessX's `BeforeModelEvent.skip_model`. Module names differ from the design's `harness/{slot_contract,processors}.py` because `harness` is a module, not a package. Tests: `tests/test_slot_contract.py`.
   - _Requirements: 1.5, 1.6_
   - _Boundary: HxScanOrchestrator_
   - _Depends: 6.1_

src/openultrasast/slot_contract.py

@@ -0,0 +1,93 @@
+"""Slot-contract discipline for model-disabled deterministic stages (task 6.3).
+
+The deterministic scan stages carry their work in named *slots* and run with model
+invocation disabled (``skip_model = True``). Each stage declares a read/write slot
+allow-list that is validated on every lifecycle hook, preserving the
+``ProcessorSpec.reads/writes`` provenance discipline of the sync ``HarnessRuntime``
+(the top-level driver) — without forcing the deterministic stages through HarnessX's
+agent loop ("bridge, do not map", per the spec design).
+
+This is the zero-dependency substrate. When the optional ``openultrasast[harnessx]``
+extra is present, the same model-disabled processors can be hosted under a HarnessX
+``MultiHookProcessor`` (see ``stage_processors.host_under_harnessx``); the
+``skip_model`` marker maps onto HarnessX's ``BeforeModelEvent.skip_model`` so no
+deterministic stage incurs a model call.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from typing import Any, Protocol
+
+from .harness import HarnessContractError
+
+
+class SlotContractError(HarnessContractError):
+    """Raised when a stage reads or writes a slot outside its declared allow-list."""
+
+
+class SlotContractMixin:
+    """A model-disabled stage that carries work in slots under a read/write allow-list."""
+
+    name: str = "slot-stage"
+    version: str = "1"
+    reads_slots: tuple[str, ...] = ()
+    writes_slots: tuple[str, ...] = ()
+    skip_model: bool = True  # deterministic: never invokes a model
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        raise NotImplementedError
+
+    def validate_reads(self, slots: Mapping[str, Any]) -> None:
+        missing = sorted(slot for slot in self.reads_slots if slot not in slots)
+        if missing:
+            raise SlotContractError(f"{self.name}: missing read slots: {', '.join(missing)}")
+
+    def validate_writes(self, updates: Mapping[str, Any]) -> None:
+        undeclared = sorted(set(updates) - set(self.writes_slots))
+        if undeclared:
+            raise SlotContractError(f"{self.name}: undeclared write slots: {', '.join(undeclared)}")
+
+    def execute(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        """Validate the read allow-list, run the stage, validate the write allow-list."""
+        self.validate_reads(slots)  # pre-hook
+        updates = self.run(slots) or {}
+        if not isinstance(updates, dict):
+            raise SlotContractError(f"{self.name}: stage returned a non-dict update")
+        self.validate_writes(updates)  # post-hook
+        return updates
+
+
+class _Emitter(Protocol):
+    def emit(self, event_type: Any, stage: str | None, payload: dict[str, Any]) -> None: ...
+
+
+class SlotPipeline:
+    """Runs slot processors in order, validating contracts and enforcing model-disable."""
+
+    def __init__(self, processors: list[SlotContractMixin]) -> None:
+        for proc in processors:
+            if not proc.skip_model:
+                raise SlotContractError(f"{proc.name}: deterministic stage must be model-disabled (skip_model=True)")
+        self._processors = processors
+
+    @property
+    def processors(self) -> list[SlotContractMixin]:
+        return list(self._processors)
+
+    def run(self, initial_slots: Mapping[str, Any], *, runtime: _Emitter | None = None) -> dict[str, Any]:
+        """Execute every stage; with ``runtime`` set, emit stage_start/stage_end lifecycle hooks."""
+        slots: dict[str, Any] = dict(initial_slots)
+        for proc in self._processors:
+            if runtime is not None:
+                runtime.emit(
+                    "stage_start", proc.name, {"reads": list(proc.reads_slots), "writes": list(proc.writes_slots), "skip_model": True}
+                )
+            updates = proc.execute(slots)
+            slots.update(updates)
+            if runtime is not None:
+                runtime.emit("stage_end", proc.name, {"status": "succeeded", "wrote": sorted(updates)})
+        return slots
+
+
+__all__ = ["SlotContractError", "SlotContractMixin", "SlotPipeline"]

src/openultrasast/stage_processors.py

@@ -0,0 +1,170 @@
+"""Deterministic scan stages as model-disabled, slot-contracted processors (task 6.3).
+
+Each stage is a :class:`slot_contract.SlotContractMixin` with ``skip_model = True`` and
+a declared read/write slot allow-list. Running them through a :class:`SlotPipeline`
+reproduces the deterministic quick-scan path byte-for-byte while enforcing the slot
+contract on every lifecycle hook. The hunter and verifier stages are *not* here —
+they are the agentic plane (``hunter_harness``/``verify_judge``); this module is the
+deterministic, model-free remainder.
+
+``host_under_harnessx`` is the optional, lazy bridge: it wraps a model-disabled stage
+as a HarnessX ``MultiHookProcessor`` that disables the model call on ``before_model``.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from pathlib import Path
+from typing import Any
+
+from .findings import quick_scan_findings
+from .mapping import analyze_entry_points, attach_reachability_hints
+from .policy import load_policy
+from .preprocess import preprocess_repository
+from .rank import rank_targets
+from .ruleset import DEFAULT_RULESET_DIR, load_ruleset
+from .scoring import build_score_artifact
+from .slot_contract import SlotContractMixin, SlotPipeline
+
+
+class PreprocessProcessor(SlotContractMixin):
+    name = "preprocess"
+    reads_slots = ("root",)
+    writes_slots = ("snapshot", "targets")
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        snapshot, targets = preprocess_repository(slots["root"])
+        return {"snapshot": snapshot, "targets": targets}
+
+
+class EntryPointProcessor(SlotContractMixin):
+    name = "entry_point"
+    reads_slots = ("root", "targets")
+    writes_slots = ("targets", "entry_points")
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        entry_points = analyze_entry_points(slots["root"], slots["targets"])
+        targets = attach_reachability_hints(slots["targets"], entry_points)
+        return {"targets": targets, "entry_points": entry_points}
+
+
+class RankProcessor(SlotContractMixin):
+    name = "rank"
+    reads_slots = ("targets",)
+    writes_slots = ("rankings",)
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        return {"rankings": rank_targets(slots["targets"])}
+
+
+class QuickFindingsProcessor(SlotContractMixin):
+    name = "quick_findings"
+    reads_slots = ("root", "targets", "rankings", "ruleset", "policy")
+    writes_slots = ("findings",)
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        findings = quick_scan_findings(slots["root"], slots["targets"], slots["rankings"], slots["ruleset"], slots["policy"])
+        return {"findings": findings}
+
+
+class PolicyScoringProcessor(SlotContractMixin):
+    name = "policy_scoring"
+    reads_slots = ("findings",)
+    writes_slots = ("reported_findings", "shadow_findings")
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        findings = slots["findings"]
+        shadow = [finding for finding in findings if finding.status == "shadow"]
+        reported = [finding for finding in findings if finding.status != "shadow"]
+        return {"reported_findings": reported, "shadow_findings": shadow}
+
+
+class ScoreProcessor(SlotContractMixin):
+    name = "score"
+    reads_slots = ("reported_findings", "ruleset", "policy")
+    writes_slots = ("score",)
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        cwe_by_rule = {rule.rule_id: rule.cwe for rule in slots["ruleset"]}
+        reported = slots["reported_findings"]
+        rule_cwe_by_id = {f.finding_id: cwe_by_rule.get(f.finding_id.split(":", 1)[0], "") for f in reported}
+        return {"score": build_score_artifact(reported, rule_cwe_by_id, slots["policy"])}
+
+
+def deterministic_processors() -> list[SlotContractMixin]:
+    """The ordered deterministic stages (preprocess → entry-point → rank → findings → policy → score)."""
+    return [
+        PreprocessProcessor(),
+        EntryPointProcessor(),
+        RankProcessor(),
+        QuickFindingsProcessor(),
+        PolicyScoringProcessor(),
+        ScoreProcessor(),
+    ]
+
+
+def build_deterministic_pipeline() -> SlotPipeline:
+    return SlotPipeline(deterministic_processors())
+
+
+def run_quick_pipeline(
+    root: Path | str,
+    *,
+    ruleset: Any = None,
+    policy: Any = None,
+    runtime: Any = None,
+) -> dict[str, Any]:
+    """Run the deterministic quick-scan pipeline and return the final slot map.
+
+    Defaults to the bundled ruleset and the vendored policy, which makes the
+    ``reported_findings`` slot byte-identical to ``findings.quick_scan_findings`` on
+    the same target.
+    """
+    resolved_ruleset = ruleset if ruleset is not None else load_ruleset(DEFAULT_RULESET_DIR)
+    resolved_policy = policy if policy is not None else load_policy()
+    initial = {"root": Path(root), "ruleset": resolved_ruleset, "policy": resolved_policy}
+    return build_deterministic_pipeline().run(initial, runtime=runtime)
+
+
+def host_under_harnessx(processor: SlotContractMixin) -> Any:
+    """Host a model-disabled deterministic stage under a HarnessX ``MultiHookProcessor``.
+
+    Lazy + capability-guarded (imports ``harnessx`` only when called). On the
+    ``before_model`` hook the hosted stage yields a ``BeforeModelEvent`` with
+    ``skip_model=True``, so no deterministic stage incurs a model call when it runs on
+    the HarnessX runloop. Raises :class:`HarnessXUnavailableError` when the extra is absent.
+    """
+    import dataclasses
+
+    from .harness_ext import require_harnessx
+
+    require_harnessx()
+    from harnessx.core.events import BeforeModelEvent
+    from harnessx.core.processor import MultiHookProcessor
+
+    class _ModelDisabledStage(MultiHookProcessor):  # type: ignore[misc, valid-type]
+        _singleton_group = "ousast_deterministic"
+        _order = 50
+
+        def __init__(self, stage: SlotContractMixin) -> None:
+            self.stage = stage
+            self.name = stage.name
+
+        async def on_before_model(self, event: BeforeModelEvent):  # type: ignore[no-untyped-def]
+            yield dataclasses.replace(event, skip_model=True, synthetic_output=f"[deterministic stage {self.stage.name}: model disabled]")
+
+    return _ModelDisabledStage(processor)
+
+
+__all__ = [
+    "EntryPointProcessor",
+    "PolicyScoringProcessor",
+    "PreprocessProcessor",
+    "QuickFindingsProcessor",
+    "RankProcessor",
+    "ScoreProcessor",
+    "build_deterministic_pipeline",
+    "deterministic_processors",
+    "host_under_harnessx",
+    "run_quick_pipeline",
+]

tests/test_gate.py

@@ -6,9 +6,7 @@
 8.4 — the governance/scoring/benchmark planes never import the HarnessX extra.
 """
 
-import importlib
 import json
-import sys
 from pathlib import Path
 
 import pytest
@@ -146,17 +144,20 @@ GOVERNANCE_SCORING_BENCHMARK_PLANES = (
     "openultrasast.ruleset.store",
     "openultrasast.improve",
     "openultrasast.improve.evolve",
+    "openultrasast.slot_contract",
+    "openultrasast.stage_processors",
 )
 
 
-def test_governance_scoring_benchmark_planes_never_import_harnessx() -> None:
-    for module in GOVERNANCE_SCORING_BENCHMARK_PLANES:
-        importlib.import_module(module)
-    leaked = sorted(name for name in sys.modules if name == "harnessx" or name.startswith("harnessx."))
-    assert leaked == [], f"governance/scoring/benchmark planes leaked HarnessX imports: {leaked}"
+def test_governance_scoring_benchmark_planes_never_import_harnessx(assert_cold_of_harnessx) -> None:  # type: ignore[no-untyped-def]
+    # Hermetic: a fresh interpreter imports every plane and must pull no harnessx.
+    imports = "\n".join(f"import {module}" for module in GOVERNANCE_SCORING_BENCHMARK_PLANES)
+    assert_cold_of_harnessx(imports)
 
 
 def test_planes_have_no_module_level_harnessx_import() -> None:
+    # Flags only column-0 (module-level) imports; an indented lazy import inside a
+    # capability-guarded function (e.g. stage_processors.host_under_harnessx) is fine.
     src = Path("src/openultrasast")
     offenders = []
     for module in GOVERNANCE_SCORING_BENCHMARK_PLANES:
@@ -166,7 +167,6 @@ def test_planes_have_no_module_level_harnessx_import() -> None:
         if path is None:
             continue
         for line in path.read_text().splitlines():
-            stripped = line.strip()
-            if stripped.startswith(("import harnessx", "from harnessx")):
-                offenders.append(f"{path}: {stripped}")
+            if line.startswith(("import harnessx", "from harnessx")):
+                offenders.append(f"{path}: {line}")
     assert offenders == [], f"plane modules import HarnessX at module scope: {offenders}"

tests/test_slot_contract.py

@@ -0,0 +1,133 @@
+"""Model-disabled, slot-contracted deterministic stages (Phase 3 task 6.3).
+
+Proves: deterministic stages carry work in declared slots, a slot-contract violation
+is raised on undeclared slot access, the pipeline is model-disabled, the slot pipeline
+reproduces the deterministic quick-scan path byte-for-byte, lifecycle hooks fire, and
+(when the extra is present) a stage can run under HarnessX with the model disabled.
+"""
+
+from collections.abc import Mapping
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from openultrasast.gate import _quick_scan
+from openultrasast.harness_ext import has_harnessx
+from openultrasast.slot_contract import SlotContractError, SlotContractMixin, SlotPipeline
+from openultrasast.stage_processors import (
+    PreprocessProcessor,
+    build_deterministic_pipeline,
+    deterministic_processors,
+    host_under_harnessx,
+    run_quick_pipeline,
+)
+
+
+class _GoodStage(SlotContractMixin):
+    name = "good"
+    reads_slots = ("a",)
+    writes_slots = ("b",)
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        return {"b": slots["a"] + 1}
+
+
+class _UndeclaredWriteStage(SlotContractMixin):
+    name = "bad_write"
+    reads_slots = ()
+    writes_slots = ("declared",)
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        return {"undeclared": 1}
+
+
+class _MissingReadStage(SlotContractMixin):
+    name = "bad_read"
+    reads_slots = ("required",)
+    writes_slots = ()
+
+    def run(self, slots: Mapping[str, Any]) -> dict[str, Any]:
+        return {}
+
+
+# ---- slot contract enforcement (1.5) ----------------------------------------
+
+
+def test_declared_slots_pass() -> None:
+    assert _GoodStage().execute({"a": 1}) == {"b": 2}
+
+
+def test_undeclared_write_is_rejected() -> None:
+    with pytest.raises(SlotContractError, match="undeclared write slots: undeclared"):
+        _UndeclaredWriteStage().execute({})
+
+
+def test_missing_read_is_rejected() -> None:
+    with pytest.raises(SlotContractError, match="missing read slots: required"):
+        _MissingReadStage().execute({})
+
+
+# ---- model-disabled invariant (1.6) -----------------------------------------
+
+
+def test_all_deterministic_stages_are_model_disabled() -> None:
+    assert all(proc.skip_model for proc in deterministic_processors())
+
+
+def test_pipeline_rejects_a_model_enabled_stage() -> None:
+    enabled = _GoodStage()
+    enabled.skip_model = False
+    with pytest.raises(SlotContractError, match="model-disabled"):
+        SlotPipeline([enabled])
+
+
+# ---- parity with the deterministic quick-scan path --------------------------
+
+
+def test_pipeline_findings_match_quick_scan_baseline() -> None:
+    target = Path("benchmarks/fixtures/python-vulnerable")
+    slots = run_quick_pipeline(target)
+    assert slots["reported_findings"] == _quick_scan(target)
+    assert "score" in slots  # the score slot is produced too
+
+
+# ---- lifecycle hooks fire per stage -----------------------------------------
+
+
+class _Recorder:
+    def __init__(self) -> None:
+        self.events: list[tuple[str, str | None]] = []
+
+    def emit(self, event_type: Any, stage: str | None, payload: dict[str, Any]) -> None:
+        self.events.append((event_type, stage))
+
+
+def test_pipeline_emits_lifecycle_hooks_per_stage() -> None:
+    recorder = _Recorder()
+    run_quick_pipeline(Path("benchmarks/fixtures/python-vulnerable"), runtime=recorder)
+    names = [proc.name for proc in build_deterministic_pipeline().processors]
+    for name in names:
+        assert ("stage_start", name) in recorder.events
+        assert ("stage_end", name) in recorder.events
+
+
+# ---- optional: run under HarnessX with the model disabled (1.6) --------------
+
+
+@pytest.mark.skipif(not has_harnessx(), reason="requires the harnessx extra")
+def test_host_under_harnessx_disables_the_model() -> None:  # pragma: no cover - needs the extra
+    import asyncio
+
+    from harnessx.core.events import BeforeModelEvent
+    from harnessx.core.processor import MultiHookProcessor
+
+    hosted = host_under_harnessx(PreprocessProcessor())
+    assert isinstance(hosted, MultiHookProcessor)
+
+    async def drive() -> list[Any]:
+        event = BeforeModelEvent(run_id="test", step_id=0)
+        return [out async for out in hosted.on_before_model(event)]
+
+    emitted = asyncio.run(drive())
+    assert emitted and emitted[-1].skip_model is True