core/chat/pack_grounding.py
Shay 6207b5fd0e feat(register): R1–R4 register pack subsystem — deterministic surface variation
Introduces the presentation axis as a fourth pack class (sibling to identity /
safety / ethics), orthogonal to the truth path. Same input + same packs +
same register ⇒ bit-for-bit reproducible surface; varying any of the three ⇒
genuinely different output. No stochastic sampling.

ADR-0068 (R1): RegisterPack frozen dataclass, loader, ratify script, seam test.
  - default_neutral_v1 ratified as null register.

ADR-0069 (R2): realizer register parameter threaded through 9 composer entry
  points; RuntimeConfig.register_pack_id; three byte-identity invariants
  (A: None ≡ pre-R2 unregistered; B: None ≡ default_neutral_v1; C: trace_hash
  invariant under register). Amended to default-with-lint after 167-call-site
  scout: composers default to UNREGISTERED, AST lint enforces explicit
  register= at runtime call sites.

ADR-0070 (R3): terse_v1 register, first non-neutral pack. realizer_overrides
  schema with known-keys allow-list (disclosure_domain_count ∈ {1,2,3}).
  build_pack_surface_candidate reads override with fail-soft clamp. New
  invariant register_invariant_grounding asserts grounding_source +
  trace_hash byte-identical across {None, neutral, terse}.

ADR-0071 (R4): seeded surface variation via convivial_v1.
  chat/register_variation.py applies SHA-256-seeded marker selection from
  bounded discourse-marker buckets. ChatResponse.pre_decoration_surface routes
  truth-path surface to core/cognition/pipeline.py so trace_hash stays
  invariant under register (the load-bearing architectural fix — initially
  invariant C failed under convivial because decoration was leaking into
  trace_hash via response.surface). Empty-string marker entries now
  legitimate ("no marker this turn" is a valid seed pick). realizer_overrides
  schema widened with per_intent nested block (validated against IntentTag
  whitelist; wired but not exercised by convivial). Two new invariants:
  seeded_variation_replay_equivalence (fresh runtimes → byte-identical) and
  seeded_variation_turn_distinct (same prompt across turns → ≥2 distinct
  surfaces).

ADR-0072 (R5, draft): telemetry + operator surface — TurnEvent gains
  register_id and register_variant_id, core chat --register flag, core demo
  register-tour. Status: Proposed; not yet implemented.

Three ratified register packs ship: default_neutral_v1 (null), terse_v1
(disclosure_domain_count=1), convivial_v1 (3 openings × 3 closings).

Verification:
  - 84 register tests pass + 1 documented skip
  - Curated lanes green: smoke 67, cognition 120+1s, teaching 17, packs 6,
    runtime 19, algebra 132
  - Cognition eval byte-identical to pre-register baseline:
    public 100/100/91.7/100, holdout 100/100/83.3/100
  - Full lane: 2608 passed, 4 skipped, 1 failed (pre-existing
    test_cli_demo.py "Combined Demo" → "Run Every Demo" rename, unrelated)

Truth-path isolation: chat/register_variation.py is realizer-side; the seam
test (tests/test_register_pack_seam.py) refuses imports of packs.register
from intent classification, propagation, vault recall, trace hashing, and
algebra.
2026-05-19 16:52:36 -07:00

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"""chat/pack_grounding.py — pack-grounded surface for cold-start DEFINITION
and RECALL intents (ADR-0048).
When the ``UnknownDomainGate`` fires with ``source="empty_vault"`` — i.e.
the runtime has no session evidence yet — the runtime would otherwise
emit the universal ``_UNKNOWN_DOMAIN_SURFACE`` disclosure on every turn,
including for terms that are explicitly compiled into the ratified
cognition pack.
This module supplies a narrow, auditable alternative: when the input's
intent is ``DEFINITION`` or ``RECALL`` AND the intent's subject lemma is
present in ``en_core_cognition_v1``, return a deterministic surface
composed from the pack lexicon's ``semantic_domains`` for that lemma,
explicitly tagged as pack-sourced.
Design constraints (matching the seven axioms):
- Geometry-first: the pack lookup is by lemma surface, but the
``semantic_domains`` were curated against the same versors the
vocabulary carries; the surface refers only to the lemma and its
curated descriptors — no synthesis, no LLM fallback.
- Reconstruction-over-storage: the surface is reconstructed from the
pack at call time; the lexicon is loaded once and cached because
ratified packs are immutable.
- Dual-correction: any lemma not in the pack returns ``None``;
callers fall through to ``_UNKNOWN_DOMAIN_SURFACE`` unchanged.
- Compilation-last: no tensors, no kernels — JSONL read and string
formatting only.
- Trust boundary: every surface produced here is explicitly tagged
``pack:en_core_cognition_v1`` so the audit contract distinguishes
pack-grounded surfaces from vault-grounded surfaces and from the
universal disclosure.
"""
from __future__ import annotations
import json
from functools import lru_cache
from pathlib import Path
from chat.pack_resolver import (
DEFAULT_RESOLVABLE_PACK_IDS,
mounted_lemmas,
resolve_lemma,
)
from packs.register.loader import RegisterPack, UNREGISTERED
PACK_ID: str = "en_core_cognition_v1"
_PACK_LEXICON_PATH = (
Path(__file__).resolve().parent.parent
/ "language_packs"
/ "data"
/ PACK_ID
/ "lexicon.jsonl"
)
@lru_cache(maxsize=1)
def _pack_index() -> dict[str, tuple[str, ...]]:
"""Load the cognition pack lexicon once and return ``{lemma: semantic_domains}``.
Ratified packs are immutable; safe to cache for the process lifetime.
Returns an empty dict if the pack is unavailable — callers must treat
a missing pack as "no pack-grounded surface available."
"""
if not _PACK_LEXICON_PATH.exists():
return {}
out: dict[str, tuple[str, ...]] = {}
for line in _PACK_LEXICON_PATH.read_text(encoding="utf-8").splitlines():
line = line.strip()
if not line:
continue
try:
entry = json.loads(line)
except json.JSONDecodeError:
continue
lemma = entry.get("lemma") or entry.get("surface")
if not lemma:
continue
domains = tuple(entry.get("semantic_domains", ()))
if domains:
out[lemma.lower()] = domains
return out
def _frame_gloss(lemma: str, pos: str, gloss: str) -> str:
"""Render a fluent sentence from a (lemma, pos, gloss) triple.
POS-aware sentence frames:
NOUN -> "{Lemma} is {gloss}."
VERB -> "To {lemma} means {gloss}."
ADJ -> "Something is {lemma} when it {gloss}."
ADV -> "{Lemma} indicates {gloss}."
ADP -> "{Lemma} is a relation of {gloss}."
SCONJ -> "{Lemma} introduces {gloss}."
PRON -> "{Lemma} asks for {gloss}."
AUX -> "{Lemma} expresses {gloss}."
INTJ -> "{Lemma} is uttered to {gloss}."
DET -> "{Lemma} specifies {gloss}."
NUM -> "{Lemma} is the cardinal value {gloss}."
* (unknown) -> "{Lemma}: {gloss}." (back-compat fallback)
The glosses are authored to match these frames exactly (see
the subagent briefs and ``language_packs/data/<pack>/glosses.jsonl``).
Capitalization is applied only to the framed surface, never to
the lemma in the lexicon (which stays lowercase by convention).
"""
key = lemma.strip()
cap = key[:1].upper() + key[1:] if key else key
pos_u = (pos or "").upper()
if pos_u == "NOUN":
return f"{cap} is {gloss}."
if pos_u == "VERB":
return f"To {key} means {gloss}."
if pos_u == "ADJ":
return f"Something is {key} when it {gloss}."
if pos_u == "ADV":
return f"{cap} indicates {gloss}."
if pos_u == "ADP":
return f"{cap} is a relation of {gloss}."
if pos_u == "SCONJ":
return f"{cap} introduces {gloss}."
if pos_u == "PRON":
return f"{cap} asks for {gloss}."
if pos_u == "AUX":
return f"{cap} expresses {gloss}."
if pos_u == "INTJ":
return f"{cap} is uttered to {gloss}."
if pos_u == "DET":
return f"{cap} specifies {gloss}."
if pos_u == "NUM":
return f"{cap} is the cardinal value {gloss}."
return f"{cap}: {gloss}."
_DEFAULT_DISCLOSURE_DOMAIN_COUNT: int = 3
def _resolve_disclosure_domain_count(
register: RegisterPack,
*,
intent_name: str | None = None,
) -> int:
"""Return clamped disclosure_domain_count for *register*.
Resolution order (ADR-0071 per_intent extension):
1. ``realizer_overrides.per_intent[intent_name].disclosure_domain_count``
2. ``realizer_overrides.disclosure_domain_count`` (flat key)
3. Default ``_DEFAULT_DISCLOSURE_DOMAIN_COUNT`` (= 3)
The ratification gate (``scripts/ratify_register_packs.py``) is the
authoritative trust boundary: only known keys with in-bounds values
can ratify. This clamp is fail-soft defense-in-depth for off-path
callers (test fixtures, ad-hoc CLI) — a malformed override should
not crash the realizer hot path. See ADR-0070.
"""
from collections.abc import Mapping as _Mapping
overrides = register.realizer_overrides
n: object = _DEFAULT_DISCLOSURE_DOMAIN_COUNT
if intent_name is not None:
per_intent: object = (
overrides.get("per_intent") if hasattr(overrides, "get") else None
)
if isinstance(per_intent, _Mapping):
sub: object = per_intent.get(intent_name)
if isinstance(sub, _Mapping) and "disclosure_domain_count" in sub:
candidate = sub["disclosure_domain_count"]
if (
isinstance(candidate, int)
and not isinstance(candidate, bool)
and 1 <= candidate <= 3
):
return candidate
flat = overrides.get("disclosure_domain_count") if hasattr(overrides, "get") else None
if flat is not None:
n = flat
if not isinstance(n, int) or isinstance(n, bool) or n < 1 or n > 3:
return _DEFAULT_DISCLOSURE_DOMAIN_COUNT
return n
def build_pack_surface_candidate(
lemma: str,
pack_ids: tuple[str, ...] = DEFAULT_RESOLVABLE_PACK_IDS,
*,
register: RegisterPack = UNREGISTERED,
):
"""Return a :class:`PackSurfaceCandidate` for *lemma*, or ``None``.
This is the selector-ready intermediate that
:func:`pack_grounded_surface` renders to a string. Two grounding
paths feed it:
1. Reviewed gloss (preferred) — when the pack ships a gloss for
the lemma AND the lemma is ratified in the same pack's
lexicon (verified by :func:`resolve_gloss`), the candidate
carries the gloss and ``is_fluent_sentence=True``.
2. Dotted-domain disclosure (fallback) — when no gloss exists
for the lemma, the candidate falls back to the original
"{lemma} — pack-grounded (...): d1; d2; d3. No session
evidence yet." structured form. ``is_fluent_sentence=False``.
When the future :class:`SurfaceSelector` lands, it will consume
this candidate directly without re-rendering; the surface field
is already the final user-facing string.
"""
from chat.pack_resolver import resolve_gloss
from chat.pack_surface_candidate import PackSurfaceCandidate
resolved = resolve_lemma(lemma, pack_ids)
if resolved is None:
return None
resolved_pack_id, domains = resolved
key = lemma.strip().lower()
# Try the gloss path first. resolve_gloss enforces lexicon
# residency, so a gloss that snuck into glosses.jsonl without a
# matching lexicon entry is rejected.
gloss_entry = resolve_gloss(lemma, pack_ids)
if gloss_entry is not None and gloss_entry[0] == resolved_pack_id:
_, gloss_pos, gloss_text = gloss_entry
# Fall back to the pack-resident POS when the gloss carries
# no POS (older gloss files). POS drives the sentence frame.
if not gloss_pos:
# Pull POS from the lexicon entry if we can.
from chat.pack_resolver import _pack_lexicon_for # noqa
# _pack_lexicon_for only stores domains today; POS is not
# in its cached dict. Default to NOUN frame as the safest
# fallback — most lemmas with glosses are nouns.
gloss_pos = "NOUN"
# Use lowercase "pack-grounded" mid-sentence so existing
# substring assertions in tests/test_pack_grounding.py (and
# downstream) continue to match. The marker is a provenance
# tag, not a sentence-starting word.
surface = (
f"{_frame_gloss(key, gloss_pos, gloss_text)} "
f"pack-grounded ({resolved_pack_id})."
)
return PackSurfaceCandidate(
surface=surface,
grounding_source="pack",
pack_id=resolved_pack_id,
gloss=gloss_text,
semantic_domains=tuple(domains),
lemma=key,
pos=gloss_pos,
is_user_facing_safe=True,
is_fluent_sentence=True,
)
# Dotted-domain disclosure fallback. Slice width is the register's
# disclosure_domain_count (ADR-0070); default (3) preserves the
# pre-R3 surface byte-for-byte under the unregistered sentinel and
# under null registers (default_neutral_v1).
n = _resolve_disclosure_domain_count(register)
head = "; ".join(domains[:n])
surface = (
f"{key} — pack-grounded ({resolved_pack_id}): {head}. "
f"No session evidence yet."
)
return PackSurfaceCandidate(
surface=surface,
grounding_source="pack",
pack_id=resolved_pack_id,
gloss=None,
semantic_domains=tuple(domains),
lemma=key,
pos="", # POS unknown via this code path
is_user_facing_safe=True,
is_fluent_sentence=False,
)
def pack_grounded_surface(
lemma: str,
pack_ids: tuple[str, ...] = DEFAULT_RESOLVABLE_PACK_IDS,
*,
register: RegisterPack = UNREGISTERED,
) -> str | None:
"""Return a deterministic pack-grounded surface for *lemma*, or ``None``.
Two surface forms, selected by gloss presence:
With gloss (preferred, lexicon-resident):
"{Lemma} is {gloss}. Pack-grounded ({pack_id})."
(frame varies by POS — see :func:`_frame_gloss`)
Without gloss (dotted-domain disclosure — original ADR-0048 form):
"{lemma} — pack-grounded ({pack_id}): {d1}; {d2}; {d3}. No session evidence yet."
Both forms carry the ``"pack-grounded ({pack_id})"`` provenance
marker so substring-permissive tests continue to pass through
the transition.
The intermediate :class:`PackSurfaceCandidate` is the
selector-ready shape; this function renders the candidate to a
string for current callers. When :class:`SurfaceSelector` lands
the candidate is what the selector consumes directly.
Returns ``None`` when the lemma is empty or doesn't resolve.
"""
candidate = build_pack_surface_candidate(lemma, pack_ids, register=register)
return candidate.surface if candidate is not None else None
def is_pack_lemma(lemma: str) -> bool:
"""Return True iff *lemma* has an entry with ``semantic_domains`` in the
ratified cognition pack (``en_core_cognition_v1``).
Cognition-pack-specific helper retained for back-compat with the
cognition-corpus modules (discovery, contemplation, teaching
chains) whose semantics are scoped to the cognition pack. For
cross-pack residency checks, use
:func:`chat.pack_resolver.is_resolvable`.
"""
if not lemma or not isinstance(lemma, str):
return False
return lemma.strip().lower() in _pack_index()
_CORRECTION_TOPIC_STOPWORDS: frozenset[str] = frozenset({
# The meta-cognition lemma itself — we never echo it as the topic
# because it's already the subject of the acknowledgement template.
"correction",
"correct",
# Common dialogue markers / fillers that classify as pack lemmas
# but don't carry topical signal in a correction utterance.
"be",
"have",
# Polarity markers (en_core_polarity_v1) — pack-resident dialogue
# tokens that carry NO topical signal in a correction utterance.
# "No, my parent disagrees" — ``no`` is the correction marker
# itself, not the topic. Without these stopwords the topic
# extractor would short-circuit on ``no`` and miss ``parent``.
"no",
"yes",
"maybe",
"perhaps",
"hardly",
"indeed",
"surely",
"definitely",
})
def _extract_correction_topic_lemma(text: str) -> str | None:
"""Return the first mounted-pack-resident, topical lemma in *text*, or None.
Deterministic: tokens are processed in left-to-right utterance
order; the first token that is resident in any mounted pack AND not
in the correction-stopword set wins. Stopwords filter out the
meta-cognition lemma itself (``correction``) and dialogue fillers
(``be``, ``have``) that classify as pack lemmas but carry no
topical signal.
ADR-0063 — residency is checked across all mounted lexicon packs
(see :data:`chat.pack_resolver.DEFAULT_RESOLVABLE_PACK_IDS`), so a
kinship correction (``"No, my parent disagrees"``) anchors the
acknowledgement on the kinship topic.
Used by :func:`pack_grounded_correction_surface` to weave the
corrected claim's subject into the acknowledgement template.
"""
if not text or not isinstance(text, str):
return None
lemmas = mounted_lemmas()
raw = text.lower()
for ch in ",.;:!?\"'()[]{}":
raw = raw.replace(ch, " ")
for token in raw.split():
if not token:
continue
if token in _CORRECTION_TOPIC_STOPWORDS:
continue
if token in lemmas:
return token
return None
def pack_grounded_correction_surface(
text: str | None = None,
*,
register: RegisterPack = UNREGISTERED,
) -> str | None:
"""ADR-0053 + ADR-0060 — cold-start CORRECTION acknowledgement.
A CORRECTION intent (``"No, that's wrong"``, ``"Actually, X means Y"``)
is meta-cognitive: it claims the previous turn was incorrect. On a
cold-start session there is no prior turn to apply the correction
to, so the doctrine-aligned response is **not** to define what
correction is (that would be the DEFINITION path) but to
acknowledge receipt and state explicitly that no prior turn exists
in this session.
Surface format (fixed templates, all atoms pack-sourced):
- **Without topic** (text=None or no pack-resident lemma found):
"correction received — pack-grounded ({pack_id}): {d1}; {d2}; {d3}.
No prior turn in this session to correct yet."
- **With topic** (text supplied AND pack lemma found):
"correction received — pack-grounded ({pack_id}): {d1}; {d2}; {d3}.
Noted topic: {lemma} ({td1}; {td2}).
No prior turn in this session to correct yet."
Every visible non-template token is either the lemma ``correction``,
the corrected-topic lemma, or a verbatim ``semantic_domains`` string
from the ratified pack. No inference; no rewording.
The trailing disclosure (``No prior turn in this session to correct
yet.``) is the constant trust-boundary label distinguishing this
cold-start acknowledgement from the post-correction teaching
repair path (``teaching/correction.py``) which engages once a
prior turn exists.
Returns ``None`` if the pack is unavailable or has no entry for
``correction`` — callers fall through to the universal disclosure
unchanged.
"""
index = _pack_index()
domains = index.get("correction")
if not domains:
return None
head = "; ".join(domains[:3])
topic_lemma = _extract_correction_topic_lemma(text) if text else None
if topic_lemma is not None:
# ADR-0063 — topic_lemma may resolve in a non-cognition pack
# (e.g. ``parent`` in en_core_relations_v1). Anchor pack stays
# cognition (``correction`` is a cognition lemma), topic domains
# come from whichever pack resolves the topic.
topic_resolved = resolve_lemma(topic_lemma)
topic_domains = topic_resolved[1] if topic_resolved is not None else ()
topic_head = "; ".join(topic_domains[:2]) if topic_domains else ""
if topic_head:
return (
f"correction received — pack-grounded ({PACK_ID}): {head}. "
f"Noted topic: {topic_lemma} ({topic_head}). "
f"No prior turn in this session to correct yet."
)
return (
f"correction received — pack-grounded ({PACK_ID}): {head}. "
f"Noted topic: {topic_lemma}. "
f"No prior turn in this session to correct yet."
)
return (
f"correction received — pack-grounded ({PACK_ID}): {head}. "
f"No prior turn in this session to correct yet."
)
_PROCEDURE_TOPIC_STOPWORDS: frozenset[str] = frozenset({
# Pack-resident lemmas that classify but carry no topical signal
# in a procedure utterance — dialogue fillers / copulae.
"be",
"have",
})
def _extract_procedure_topic_lemma(subject_text: str) -> str | None:
"""Return the **last** pack-resident topical lemma in *subject_text*.
Procedure subjects emerge from the intent classifier as verb
phrases (e.g. ``"define a concept"``, ``"correct an error"``,
``"verify a claim"``). The procedure verb tends to be the
first pack-resident lemma; the *topic* of the procedure tends
to be the last. Selecting the last pack-resident lemma
captures the user's actual subject of interest without requiring
POS tagging or syntactic analysis.
Deterministic: tokens are processed left-to-right; the *last*
token that is pack-resident AND not in the stopword set wins.
Stopwords filter only dialogue fillers (``be`` / ``have``);
pack-resident verbs (``define``, ``verify``, ``correct``, etc.)
are NOT stopworded — when a procedure utterance contains only
one pack-resident lemma and that lemma is the verb, the verb
is the topical anchor by elimination.
"""
if not subject_text or not isinstance(subject_text, str):
return None
lemmas = mounted_lemmas()
raw = subject_text.lower()
for ch in ",.;:!?\"'()[]{}":
raw = raw.replace(ch, " ")
last_match: str | None = None
for token in raw.split():
if not token:
continue
if token in _PROCEDURE_TOPIC_STOPWORDS:
continue
if token in lemmas:
last_match = token
return last_match
def pack_grounded_procedure_surface(
subject_text: str,
*,
register: RegisterPack = UNREGISTERED,
) -> str | None:
"""ADR-0061 — cold-start PROCEDURE pack-grounded surface.
A PROCEDURE intent (``"How do I X?"``, ``"How can I Y?"``) requests
step-by-step guidance. Procedural chains are not part of the
reviewed teaching corpus today (teaching chains cover CAUSE and
VERIFICATION intents only — see
``chat.teaching_grounding._VALID_INTENTS``). Rather than fall
through to the universal disclosure on every procedure question,
this composer emits a pack-grounded acknowledgement that surfaces
the topical lemma of the procedure and notes explicitly that
step-by-step guidance is not yet ratified — preserving honesty
while grounding the user's topic in pack semantics.
Surface format (fixed template, all atoms pack-sourced):
"procedure-grounded ({pack_id}): {lemma} ({d1}; {d2}).
Step-by-step guidance for {lemma} is not yet ratified
in this session."
The trailing clause is the constant trust-boundary label,
analogous to ``"No prior turn in this session to correct yet."``
in the CORRECTION acknowledgement (ADR-0053 / ADR-0060).
Returns ``None`` if no pack-resident lemma is found in
*subject_text* — callers fall through to the universal disclosure
unchanged (preserves the ADR-0053 honesty contract for the
fully-unknown case).
"""
lemma = _extract_procedure_topic_lemma(subject_text)
if lemma is None:
return None
# ADR-0063 — resolve topic across all mounted lexicon packs. The
# surface tag follows the resolving pack id so a kinship procedure
# (``"How do I trace my ancestor?"``) emits
# ``procedure-grounded (en_core_relations_v1)``.
resolved = resolve_lemma(lemma)
if resolved is None:
return None
resolved_pack_id, domains = resolved
head = "; ".join(domains[:2])
return (
f"procedure-grounded ({resolved_pack_id}): {lemma} ({head}). "
f"Step-by-step guidance for {lemma} is not yet ratified in this session."
)
def pack_grounded_comparison_surface(
lemma_a: str,
lemma_b: str,
*,
register: RegisterPack = UNREGISTERED,
) -> str | None:
"""ADR-0050 — deterministic pack-grounded surface for COMPARISON intent.
Returns a surface that composes each lemma's pack semantic_domains
side-by-side, with no rewording or inference:
"{a} (d_a1; d_a2) contrasts with {b} (d_b1; d_b2) — pack-grounded
({pack_id}). No session evidence yet."
Up to two semantic_domains per side are emitted to keep the surface
compact. All visible tokens are either the lemmas themselves or
verbatim pack strings; the verb "contrasts with" is the fixed
COMPARISON template constant (mirroring the relation predicate
`contrasts_with` already humanised by ``humanize_predicate``).
Returns ``None`` when:
- either lemma is empty or not a string,
- either lemma is not present in the pack,
- the two lemmas are identical (a comparison between a term
and itself carries no contrastive evidence — defer to the
single-lemma ``pack_grounded_surface`` path or to the
universal disclosure).
"""
if not lemma_a or not isinstance(lemma_a, str):
return None
if not lemma_b or not isinstance(lemma_b, str):
return None
key_a = lemma_a.strip().lower()
key_b = lemma_b.strip().lower()
if not key_a or not key_b:
return None
if key_a == key_b:
return None
resolved_a = resolve_lemma(key_a)
resolved_b = resolve_lemma(key_b)
if resolved_a is None or resolved_b is None:
return None
pack_a, domains_a = resolved_a
pack_b, domains_b = resolved_b
head_a = "; ".join(domains_a[:2])
head_b = "; ".join(domains_b[:2])
# ADR-0063 — tag follows the resolving pack ids. Cognition-only
# comparisons stay byte-identical (both sides resolve to cognition);
# cross-pack comparisons render the composite tag explicitly.
if pack_a == pack_b:
tag = f"pack-grounded ({pack_a})"
else:
tag = f"pack-grounded ({pack_a} × {pack_b})"
return (
f"{key_a} ({head_a}) contrasts with {key_b} ({head_b}) "
f"{tag}. No session evidence yet."
)