feat(disposition): separate the assessment axis from the action

`decide` returned a `Disposition` — WARN / QUARANTINE_REVIEW / FAIL_SECURE —
which names an ACTION. But BRIEF design principle 4 says the library reports
and the pipeline decides, and disposition.py admitted the gap in its own
docstring: "It imposes no blocking of its own." So we returned an action we
cannot enforce, having discarded the judgement that produced it. A consumer
wanting different behaviour had to reinterpret the action itself — which is
why a consumer ends up pinning our GRADING: the action was all they got.

`Risk` (NONE/LOW/ELEVATED/SEVERE) now carries that judgement, and
`Policy.action_map` lets a caller map it to their own action. Both overlays
move the assessment rather than the action, so a custom map cannot silently
drop the compound escalation or the quarantine floor. `guard`'s fail-closed
path pins both axes and deliberately bypasses the map: downgrading SEVERE
means "I accept this class of finding", never "I accept a crashed scanner".

`DispositionResult.assessment` is required with no default. `Risk.NONE` is the
natural-looking default and the wrong one — a site that forgot the field would
report clean, and the axis would fail open.

MEASURED ADDITIVE, not assumed:
  - 703 -> 715 tests, no existing test changed
  - coverage matrix 128/128 recall, 6/6 documented gaps still hold
  - the PRESET_USER_UPLOAD grading table locked in 0.3.1 re-measured row by
    row: ordinary link/image/autolink/refdef -> warn on BOTH doors, unchanged

Both locked consumer promises in docs/PLAN-v1.md were checked against that
measurement and neither fires: the grading is untouched (linkedin-studio), and
the relative-target asymmetry is untouched (llm-ingestion-okf).

Scope held to disposition, per PLAN-v1.md:380. Version stays 0.4.0; the 0.5.0
bump lands in its release commit with all five version surfaces at once —
that is the fix for the defect where the v0.4.0 tag carried a 0.3.4 README.

Records limitation 32: `Severity` still carries disposition intent on the
DETECTION side, which this change does not address and cannot without moving
the grading.

CHANGELOG.md

@@ -7,7 +7,56 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-Nothing yet.
+### Added — the axis separation: assessment (`Risk`) vs action (`Disposition`)
+
+> **Additive, and measured to be so.** Every disposition 0.4.0 rendered is
+> rendered identically: the full suite went 703 → 715 with no test changed, the
+> coverage matrix holds at 128/128 recall with 6/6 documented gaps, and the
+> `PRESET_USER_UPLOAD` grading table locked in 0.3.1 was re-measured row by row
+> and is unchanged. A caller that never reads the new field sees no difference.
+
+`decide` and `guard` returned a `Disposition` — `WARN` / `QUARANTINE_REVIEW` /
+`FAIL_SECURE` — which names an **action**. But BRIEF design principle 4 says the
+library reports and the *pipeline* decides, and `disposition.py` admitted the
+gap in its own docstring: *"It imposes no blocking of its own."* So the library
+returned an action it cannot enforce, while discarding the judgement that
+produced it. A consumer wanting different behaviour had to reinterpret the
+action itself, which is why a consumer ends up pinning our *grading* — the
+action was all they got.
+
+- **`Risk`** — the new assessment axis: `NONE` / `LOW` / `ELEVATED` / `SEVERE`.
+  It answers *how dangerous is this artifact given its source context*, and is
+  trust-aware exactly as BRIEF §4.7 describes the domain: the same finding
+  genuinely is a different judgement in authored prose than in a code fence.
+- **`DispositionResult.assessment`** — carries that judgement alongside the
+  action. The field is **required, with no default**: `Risk.NONE` would be the
+  natural-looking default and is the wrong one, since a construction site that
+  forgot it would report *clean* and the axis would fail open.
+- **`Policy.action_map`** — an optional `Risk -> Disposition` override, so
+  "hold for review where you would block" is a policy statement rather than a
+  reason to pin our grading. Defaults to `None`, which means
+  `DEFAULT_ACTION_MAP` and keeps an untouched `Policy` hashable as before. A
+  partial map falls back per-level instead of raising.
+- Both overlays — compound escalation and the quarantine floor — now move the
+  **assessment**, so a custom action map cannot silently drop them.
+- The fail-closed path in `guard` pins both axes to their most severe value and
+  deliberately does **not** route through the action map: a policy that
+  downgrades `SEVERE` means "I accept this class of finding", never "I accept a
+  scanner that crashed on crafted input" (§4.6).
+
+`NONE` and `LOW` both map to `WARN`, which is the point rather than an
+oversight: a clean document and one carrying only low-severity findings were a
+single indistinguishable value through 0.4.0.
+
+### Known limitation recorded (32, was 31)
+
+`Severity` still carries disposition intent on the *detection* side — the
+separation above is caller-side only. Two places say so outright:
+`ACTIVE_CONTENT_ORDINARY_SEVERITY = LOW` exists because grading an ordinary
+external image `HIGH` fail-secured ordinary uploads, and the quarantine floor
+was raised to `MEDIUM+` to repair the same regression from the other end.
+Closing it changes the grading and so fires a consumer-notification promise;
+deferred deliberately. See `docs/LIMITATIONS.md`.
 
 
 ## [0.4.0] — 2026-08-10

README.md

@@ -236,7 +236,7 @@ a green scan means safe content. The highest-impact items:
   egress, semantic poisoning, trusted-prose lone-HIGH, lexicon dedup (`count=1`),
   pure beaconing, and short opaque URL segments.
 
-**Full list — 31 items, each with the mechanism, plus the out-of-scope boundary:**
+**Full list — 32 items, each with the mechanism, plus the out-of-scope boundary:**
 [`docs/LIMITATIONS.md`](docs/LIMITATIONS.md). Several carry field measurements from
 consumer corpora, including the false positives the URL-shape rule actually produces.
 

docs/LIMITATIONS.md

@@ -334,6 +334,25 @@ fails the test, forcing this doc to be updated:
 5. **Pure beaconing** — a bare-path remote image on a hostile host is LOW (above).
 6. **Short opaque URL segment (<24 chars)** — below what entropy can resolve (above).
 
+- **`Severity` still carries disposition intent on the detection side.** The
+  0.5.0 axis separation split the *assessment* (`Risk`) from the *action*
+  (`Disposition`), but only on the caller side of the boundary. Inside the
+  detectors, a finding's `Severity` is still calibrated partly for the
+  disposition it will produce rather than purely for what was observed, and two
+  places in the tree say so outright: `calibration.py`'s
+  `ACTIVE_CONTENT_ORDINARY_SEVERITY = LOW` exists because grading an ordinary
+  external image `HIGH` fail-secured ordinary uploads (measured on v0.3.0), and
+  `disposition.py`'s quarantine floor was raised from *any finding* to *MEDIUM+*
+  to repair the same regression from the other end. Both fixes are correct for
+  the dispositions they produce; the cost is that an ordinary external image is
+  recorded as low-severity rather than as *a real outward-fetch capability that
+  is not evidence of an attack* — so no policy, however strict, can act on that
+  capability, because the detector already decided it did not matter. Closing
+  this means giving detectors a channel that says what was seen separately from
+  how bad it is, which changes the grading and therefore fires the
+  consumer-notification promise in `docs/PLAN-v1.md`. Deferred deliberately, not
+  overlooked.
+
 ## Out-of-scope (documented boundary)
 
 Embedding/vector-layer defenses (OWASP LLM08, downstream of persist); multimodal

src/llm_ingestion_guard/__init__.py

@@ -40,8 +40,10 @@ from .disposition import (
     Policy,
     Trust,
     Provenance,
+    Risk,
     Disposition,
     DispositionResult,
+    DEFAULT_ACTION_MAP,
     PRESET_TRUSTED_SOURCE,
     PRESET_USER_UPLOAD,
 )
@@ -135,9 +137,9 @@ __all__ = [
     "neutralize", "NeutralizeResult",
     # output-side
     "scan_output", "scan_secret_egress", "scan_active_content",
-    # disposition
+    # disposition — `Risk` is the assessment axis, `Disposition` the action
     "decide", "guard", "Policy", "Trust", "Provenance",
-    "Disposition", "DispositionResult",
+    "Risk", "Disposition", "DispositionResult", "DEFAULT_ACTION_MAP",
     "PRESET_TRUSTED_SOURCE", "PRESET_USER_UPLOAD",
     # contract asserters
     "assert_tool_less", "assert_credential_allowlist",

src/llm_ingestion_guard/calibration.py

@@ -90,6 +90,34 @@ DISPOSITION_RANK = {
     "fail_secure": 2,
 }
 
+# --- assessment: the risk axis (0.5.0 axis separation) ----------------------
+# Rank of each risk level, same value-keyed convention as DISPOSITION_RANK.
+# ``Risk`` answers *how dangerous is this artifact given its source context*;
+# ``Disposition`` answers *what should the pipeline do*. They were one enum
+# through 0.4.0, which meant a consumer wanting a different action had to
+# re-derive it from the action itself — the assessment was already discarded.
+RISK_RANK = {
+    "none": 0,
+    "low": 1,
+    "elevated": 2,
+    "severe": 3,
+}
+
+# The default risk -> disposition mapping, keyed by both enum *value* strings.
+# This map is what keeps the separation additive: it reproduces every
+# disposition 0.4.0 rendered, so a caller that ignores the new axis sees no
+# change at all. A ``Policy`` may override it; ``None`` means "use this".
+#
+# NONE and LOW both map to ``warn`` deliberately — that collapse is precisely
+# the information 0.4.0 could not express, since a clean document and one
+# carrying only low-severity findings were the same single value.
+DEFAULT_ACTION_MAP = {
+    "none": "warn",
+    "low": "warn",
+    "elevated": "quarantine_review",
+    "severe": "fail_secure",
+}
+
 # --- active_content: per-construct severities -------------------------------
 # Zero-click auto-fetch / auto-execute constructs are HIGH; click-required ones
 # are MEDIUM. Mirrors ``neutralize``'s defang classes. These are the severities

src/llm_ingestion_guard/disposition.py

@@ -23,12 +23,35 @@ from __future__ import annotations
 
 from dataclasses import dataclass
 from enum import Enum
-from typing import Callable, Optional
+from typing import Callable, Mapping, Optional
 
-from .calibration import DISPOSITION_RANK
+from .calibration import DEFAULT_ACTION_MAP as _DEFAULT_ACTION_MAP_VALUES
+from .calibration import DISPOSITION_RANK, RISK_RANK
 from .report import Report, Severity, severity_rank
 
 
+class Risk(str, Enum):
+    """How dangerous the artifact is *given its source context* — the assessment.
+
+    The other half of the 0.5.0 axis separation. :class:`Disposition` names an
+    **action**; ``Risk`` names the **judgement that action was derived from**.
+    Through 0.4.0 only the action was returned, which had two costs: a consumer
+    who wanted different behaviour had to reinterpret an action whose reasoning
+    was already gone, and ``NONE`` vs ``LOW`` — a clean document versus one
+    carrying only low-severity findings — were indistinguishable, since both
+    render as ``WARN``.
+
+    Risk is **trust-aware**, exactly as BRIEF §4.7 describes the domain: the
+    same finding genuinely *is* a different judgement in authored prose than in
+    a code fence, not merely a different action taken on one shared judgement.
+    """
+
+    NONE = "none"          # no findings at all
+    LOW = "low"            # findings present, none dispositive in this context
+    ELEVATED = "elevated"  # suspicious enough to hold for a human
+    SEVERE = "severe"      # treat as a real payload
+
+
 class Disposition(str, Enum):
     """The gate decision, ordered by :data:`_DISPOSITION_RANK`."""
 
@@ -54,19 +77,41 @@ class Provenance(str, Enum):
 
 @dataclass(frozen=True)
 class Policy:
-    """A named source-trust policy. See the ``PRESET_*`` constants."""
+    """A named source-trust policy. See the ``PRESET_*`` constants.
+
+    ``action_map`` overrides how an assessed :class:`Risk` becomes a
+    :class:`Disposition`. ``None`` — the default — means
+    :data:`DEFAULT_ACTION_MAP`, which reproduces every disposition 0.4.0
+    rendered. It is deliberately ``None`` rather than the map itself so an
+    untouched ``Policy`` stays hashable exactly as before.
+
+    This is the seam a consumer needs: wanting *hold for review* where we
+    render *fail secure* is now a policy statement, not a reason to pin our
+    grading.
+    """
 
     trust: Trust
     quarantine_default: bool = False  # any finding -> at least QUARANTINE_REVIEW
+    action_map: Optional[Mapping[Risk, Disposition]] = None
 
 
 @dataclass(frozen=True)
 class DispositionResult:
-    """The decision plus an auditable trail of which rules fired."""
+    """The decision plus an auditable trail of which rules fired.
+
+    ``assessment`` is the risk the rules actually established; ``disposition``
+    is that risk mapped through the policy's action map. Consumers that gate on
+    the assessment are insulated from a later recalibration of the mapping.
+    """
 
     disposition: Disposition
     reasons: tuple[str, ...]
     max_severity: Optional[Severity]
+    assessment: Risk
+    # Deliberately *required*, with no default. ``Risk.NONE`` would be the
+    # natural-looking default and is precisely the wrong one: a construction
+    # site that forgot the field would report a clean assessment, so the axis
+    # would fail open. Fail-loud beats fail-silent for a gate (BRIEF §4.7).
 
 
 # Invisible carriers have no legitimate place in a reference file: they block in
@@ -83,20 +128,52 @@ _CARRIER_LABELS = frozenset({
     "lexicon:unicode-tags-present",
 })
 
-# Enum-keyed rank rebuilt from calibration's value-keyed source of truth
+# Enum-keyed ranks rebuilt from calibration's value-keyed source of truth
-# (calibration is a leaf module and cannot import the Disposition enum without a
+# (calibration is a leaf module and cannot import these enums without a cycle).
-# cycle). Higher = more severe.
+# Higher = more severe.
 _DISPOSITION_RANK = {d: DISPOSITION_RANK[d.value] for d in Disposition}
+_RISK_RANK = {r: RISK_RANK[r.value] for r in Risk}
+
+DEFAULT_ACTION_MAP: Mapping[Risk, Disposition] = {
+    Risk(risk_value): Disposition(disposition_value)
+    for risk_value, disposition_value in _DEFAULT_ACTION_MAP_VALUES.items()
+}
+"""The default :class:`Risk` -> :class:`Disposition` mapping.
+
+Reproduces every disposition 0.4.0 rendered, so the axis separation is additive:
+a caller that never reads ``assessment`` sees no behavioural change.
+"""
 
 
-def _more_severe(a: Disposition, b: Disposition) -> Disposition:
+def _more_severe(a: Risk, b: Risk) -> Risk:
-    return a if _DISPOSITION_RANK[a] >= _DISPOSITION_RANK[b] else b
+    return a if _RISK_RANK[a] >= _RISK_RANK[b] else b
 
 
-def _escalate(disposition: Disposition) -> Disposition:
+def _escalate(risk: Risk) -> Risk:
-    if disposition is Disposition.WARN:
+    """Escalate one tier on the assessment axis.
-        return Disposition.QUARANTINE_REVIEW
+
-    return Disposition.FAIL_SECURE
+    ``NONE`` is unreachable here — the only caller is the compound overlay,
+    which needs two MEDIUM+ findings and so implies at least ``LOW`` — but it
+    escalates rather than being a no-op, so the function is total.
+    """
+    if risk is Risk.SEVERE:
+        return Risk.SEVERE
+    return Risk(next(
+        r for r in Risk if _RISK_RANK[r] == _RISK_RANK[risk] + 1
+    ))
+
+
+def _action(risk: Risk, policy: Policy) -> Disposition:
+    """Map an assessed ``risk`` to an action under ``policy``.
+
+    An action map that omits a risk level falls back to the default rather than
+    raising: a partial override is a likely way to use this, and a ``KeyError``
+    from inside the gate would be turned into a fail-closed by :func:`guard`
+    anyway — silently, and with a useless reason.
+    """
+    if policy.action_map is not None and risk in policy.action_map:
+        return policy.action_map[risk]
+    return DEFAULT_ACTION_MAP[risk]
 
 
 def _carrier_label(report: Report) -> Optional[str]:
@@ -126,21 +203,24 @@ def decide(
     reasons: list[str] = []
     max_sev = report.max_severity()
 
+    def result(risk: Risk) -> DispositionResult:
+        return DispositionResult(_action(risk, policy), tuple(reasons), max_sev, risk)
+
     # Overlay A — compound forced-fallback (§4.6): a scan hit plus a failed
     # transform is a probable forced-fallback attack. Overrides everything.
     if transform_failed and report.found:
         reasons.append("compound-forced-fallback: transform failed with active findings")
-        return DispositionResult(Disposition.FAIL_SECURE, tuple(reasons), max_sev)
+        return result(Risk.SEVERE)
 
     # Any-tier exceptions (§4.7): invisible carriers and CRITICAL findings block
     # regardless of trust or provenance.
     carrier = _carrier_label(report)
     if carrier is not None:
         reasons.append(f"any-tier: invisible carrier ({carrier})")
-        return DispositionResult(Disposition.FAIL_SECURE, tuple(reasons), max_sev)
+        return result(Risk.SEVERE)
     if max_sev is Severity.CRITICAL:
         reasons.append("any-tier: CRITICAL finding")
-        return DispositionResult(Disposition.FAIL_SECURE, tuple(reasons), max_sev)
+        return result(Risk.SEVERE)
 
     # Effective low-trust: an untrusted source, or a low-trust region within an
     # otherwise-trusted document (a code fence or a localized string).
@@ -149,38 +229,47 @@ def decide(
         Provenance.LOCALIZED,
     )
 
-    disposition = _base_disposition(report, max_sev, low_trust, policy, reasons)
+    risk = _base_risk(report, max_sev, low_trust, policy, reasons)
 
     # Overlay B — compound escalation (§4.6): several weaker signals escalate one
-    # tier even when each alone would only WARN.
+    # tier even when each alone would only WARN. Escalating the *assessment*
+    # rather than the action is what keeps the overlay from being silently lost
+    # under a custom action map.
     if _is_compound(report):
-        escalated = _escalate(disposition)
+        escalated = _escalate(risk)
-        if escalated is not disposition:
+        if escalated is not risk:
             reasons.append("compound: >=2 findings at MEDIUM+ -> escalated one tier")
-            disposition = escalated
+            risk = escalated
 
-    return DispositionResult(disposition, tuple(reasons), max_sev)
+    return result(risk)
 
 
-def _base_disposition(
+def _base_risk(
     report: Report,
     max_sev: Optional[Severity],
     low_trust: bool,
     policy: Policy,
     reasons: list[str],
-) -> Disposition:
+) -> Risk:
+    """Assess ``report`` before the overlays, on the risk axis.
+
+    The reason strings still name the *disposition* each branch yields, because
+    they are an audit trail consumers already read; the axis separation must not
+    silently reword it. They are rendered through :func:`_action` so a policy
+    that remaps an action gets a trail that matches what it actually did.
+    """
     tier = "low" if low_trust else "high"
     if max_sev is None:
-        disposition = Disposition.WARN
+        risk = Risk.NONE
         reasons.append("clean: no findings")
     elif max_sev is Severity.HIGH:
-        disposition = Disposition.FAIL_SECURE if low_trust else Disposition.WARN
+        risk = Risk.SEVERE if low_trust else Risk.LOW
-        reasons.append(f"HIGH under {tier}-trust -> {disposition.value}")
+        reasons.append(f"HIGH under {tier}-trust -> {_action(risk, policy).value}")
     elif max_sev is Severity.MEDIUM:
-        disposition = Disposition.QUARANTINE_REVIEW if low_trust else Disposition.WARN
+        risk = Risk.ELEVATED if low_trust else Risk.LOW
-        reasons.append(f"MEDIUM under {tier}-trust -> {disposition.value}")
+        reasons.append(f"MEDIUM under {tier}-trust -> {_action(risk, policy).value}")
     else:  # LOW or INFO
-        disposition = Disposition.WARN
+        risk = Risk.LOW
         reasons.append(f"{max_sev.value} -> WARN")
 
     # quarantine_default floor: a finding at MEDIUM+ is held for review.
@@ -194,12 +283,12 @@ def _base_disposition(
     if policy.quarantine_default and max_sev is not None and (
         severity_rank(max_sev) >= severity_rank(Severity.MEDIUM)
     ):
-        floored = _more_severe(disposition, Disposition.QUARANTINE_REVIEW)
+        floored = _more_severe(risk, Risk.ELEVATED)
-        if floored is not disposition:
+        if floored is not risk:
             reasons.append("quarantine-floor: MEDIUM+ finding -> QUARANTINE_REVIEW")
-            disposition = floored
+            risk = floored
 
-    return disposition
+    return risk
 
 
 def guard(
@@ -221,10 +310,16 @@ def guard(
         report = scan_fn()
         return decide(report, policy, provenance=provenance, transform_failed=transform_failed)
     except Exception as exc:  # noqa: BLE001 — fail closed on ANY scan/dispose error
+        # Both axes are pinned to their most severe value, and deliberately NOT
+        # routed through the policy's action map: an un-scannable artifact is
+        # not a risk judgement a caller gets to remap. A policy that downgrades
+        # SEVERE means "I accept this class of finding", never "I accept a
+        # scanner that crashed on crafted input" (BRIEF §4.6, fail closed).
         return DispositionResult(
             Disposition.FAIL_SECURE,
             (f"fail-closed: scan/dispose error: {type(exc).__name__}",),
             None,
+            Risk.SEVERE,
         )
 
 

tests/test_disposition.py

@@ -5,10 +5,12 @@ import pytest
 
 from llm_ingestion_guard.report import Finding, Report, Severity, Source
 from llm_ingestion_guard.disposition import (
+    DEFAULT_ACTION_MAP,
     Disposition,
     DispositionResult,
     Policy,
     Provenance,
+    Risk,
     Trust,
     decide,
     guard,
@@ -258,3 +260,99 @@ def test_floor_and_escalation_compose_to_fail_secure():
         _finding(severity=Severity.MEDIUM, label="entropy:base64", detector="entropy"),
     )
     assert decide(report, PRESET_USER_UPLOAD).disposition is Disposition.FAIL_SECURE
+
+
+# --- 0.5.0 axis separation: assessment (how dangerous) vs disposition (what to
+# --- do). PLAN-v1.md:294/:380 — change DISPOSITION, never the grading.
+#
+# `Disposition` is three *actions*, but BRIEF principle 4 says the library
+# reports and the *pipeline* decides. `decide` therefore returned an action it
+# cannot enforce, and a consumer wanting a different action had to re-derive it
+# from that action — the assessment which produced it was already gone. That is
+# why a consumer ends up pinning the *grading*: the action is all they get. The
+# assessment axis hands them the input instead of the verdict.
+
+
+def test_result_carries_an_assessment_distinct_from_the_disposition():
+    # The payoff: a clean report and a LOW-severity report are BOTH `WARN`
+    # today, and indistinguishable without re-reading the report. The assessment
+    # axis separates them while leaving the action identical.
+    clean = decide(_report(), UNTRUSTED)
+    low = decide(_report(_finding(severity=Severity.LOW, label="active:markdown-link")),
+                 UNTRUSTED)
+
+    assert clean.disposition is Disposition.WARN
+    assert low.disposition is Disposition.WARN          # action: identical
+    assert clean.assessment is Risk.NONE
+    assert low.assessment is Risk.LOW                   # assessment: distinct
+
+
+def test_default_action_map_reproduces_todays_outcomes():
+    # The default mapping is a no-op by construction: this is the contract that
+    # keeps `PRESET_USER_UPLOAD` grading untouched (locked promise 1).
+    assert DEFAULT_ACTION_MAP == {
+        Risk.NONE: Disposition.WARN,
+        Risk.LOW: Disposition.WARN,
+        Risk.ELEVATED: Disposition.QUARANTINE_REVIEW,
+        Risk.SEVERE: Disposition.FAIL_SECURE,
+    }
+
+
+@pytest.mark.parametrize("severity,policy,provenance,expected_risk", [
+    (Severity.CRITICAL, TRUSTED, Provenance.PROSE, Risk.SEVERE),
+    (Severity.HIGH, TRUSTED, Provenance.PROSE, Risk.LOW),
+    (Severity.HIGH, TRUSTED, Provenance.CODE_FENCE, Risk.SEVERE),
+    (Severity.HIGH, UNTRUSTED, Provenance.PROSE, Risk.SEVERE),
+    (Severity.MEDIUM, TRUSTED, Provenance.PROSE, Risk.LOW),
+    (Severity.MEDIUM, UNTRUSTED, Provenance.PROSE, Risk.ELEVATED),
+    (Severity.LOW, UNTRUSTED, Provenance.PROSE, Risk.LOW),
+])
+def test_assessment_tracks_danger_given_trust(severity, policy, provenance, expected_risk):
+    # The assessment is trust-aware, exactly as BRIEF §4.7 describes: the *same*
+    # hit is a different assessment in prose vs a code fence — not merely a
+    # different action on one shared assessment.
+    result = decide(_report(_finding(severity=severity)), policy, provenance=provenance)
+    assert result.assessment is expected_risk
+    assert result.disposition is DEFAULT_ACTION_MAP[expected_risk]
+
+
+def test_custom_action_map_changes_the_action_not_the_assessment():
+    # THE point of the separation. A consumer that wants to hold for review
+    # rather than block says so in the policy, and the assessment it was derived
+    # from is unchanged — so they never have to pin our grading to get their
+    # behaviour.
+    report = _report(_finding(severity=Severity.HIGH))
+    strict = Policy(trust=Trust.UNTRUSTED)
+    lenient = Policy(trust=Trust.UNTRUSTED, action_map={
+        **DEFAULT_ACTION_MAP,
+        Risk.SEVERE: Disposition.QUARANTINE_REVIEW,
+    })
+
+    assert decide(report, strict).disposition is Disposition.FAIL_SECURE
+    assert decide(report, lenient).disposition is Disposition.QUARANTINE_REVIEW
+    assert decide(report, strict).assessment is Risk.SEVERE
+    assert decide(report, lenient).assessment is Risk.SEVERE
+
+
+def test_overlays_escalate_the_assessment_not_only_the_action():
+    # Compound escalation and the quarantine floor are assessment-level moves;
+    # if they only moved the action, a custom action_map would silently drop
+    # them. Two MEDIUM findings untrusted: ELEVATED escalated to SEVERE.
+    report = _report(
+        _finding(severity=Severity.MEDIUM, label="lexicon:config"),
+        _finding(severity=Severity.MEDIUM, label="entropy:base64", detector="entropy"),
+    )
+    result = decide(report, PRESET_USER_UPLOAD)
+    assert result.assessment is Risk.SEVERE
+    assert result.disposition is Disposition.FAIL_SECURE
+
+
+def test_guard_fails_closed_with_a_severe_assessment():
+    # The fail-closed path must not leave the assessment unset, or a consumer
+    # mapping on the assessment alone would read a scanner crash as clean.
+    def boom() -> Report:
+        raise RuntimeError("detector exploded")
+
+    result = guard(boom, PRESET_USER_UPLOAD)
+    assert result.disposition is Disposition.FAIL_SECURE
+    assert result.assessment is Risk.SEVERE