Strict superset of ADR-0062's depth-1 composer. `max_depth` is the
number of follow-up hops appended beyond the initial chain:
max_depth=0 → byte-identical to single-chain surface
max_depth=1 → byte-identical to ADR-0062 composed
max_depth=2 → byte-identical to ADR-0062 when no second hop
survives, strict superset when one does
The composer surfaces content the realizer was silently dropping
from chains already ratified in `cognition_chains_v1`. Example
live lift on `"Why does light exist?"`:
composed: "light reveals truth, which grounds knowledge."
transitive(2): "...which grounds knowledge, which requires evidence."
Cycle-safe at every depth via a single visited-set; single-corpus
traversal in v1 (cross-corpus transitive deferred to a follow-up
ADR alongside ADR-0064's cross-pack model).
Both flags default False — every existing surface is preserved
byte-identically. When both `composed_surface` and
`transitive_surface` are True, transitive wins.
Implementation:
- `core/config.py`: `transitive_surface: bool = False`,
`transitive_max_depth: int = 2`.
- `chat/teaching_grounding.py`: `_resolve_followup` shared helper
refactored out of the depth-1 composer (no behavioural change),
plus new `teaching_grounded_surface_transitive(subject,
intent_tag, *, max_depth)`.
- `chat/runtime.py`: dispatch order — transitive > composed > single.
Verification:
- tests/test_transitive_surface.py: 16 new tests covering pure-fn
contract, visited-set cycle guard at every depth, runtime
integration, and the cognition-lane null-drop invariant at
`max_depth=2` (public + holdout splits).
- tests/test_composed_surface.py: 11/11 pass after the helper
refactor (ADR-0062 behaviour preserved).
- `core test --suite smoke`: 67 pass.
- `core test --suite cognition`: 120 pass, 1 skipped.
- `core test --suite teaching`: 17 pass.
- `core eval cognition`: 100 / 91.7 / 100 / 100 (byte-identical).
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