The Arborist arm runs answer_mode='claim_lattice' (per control_sweep.py
:179, control_ab.py:155) so its answers arrive as the JSON envelope
{"claims":[{"text":"...","evidence_ids":["E1"]},...]}.
_descaffold strips the [E1] evidence-pointer markup but the JSON
braces + key syntax remain. The verifier's strategy-2 (span) and
strategy-3 (proper-noun) extractors see brace noise instead of the
inner claim prose — every Arborist record degraded to UNGROUNDED.
The 2026-05-19T17-01-17Z sweep, re-graded with the freshly calibrated
judge (5a17f61), surfaced this: Arborist arm reported 0 CG across all
three variants in the live phase 1 output (the live run was pre-
calibration), and 29/120 CG (24%) under the calibrated rescore — clear
improvement just from theta_contra=0.85, but the JSON envelope was
still hobbling the verifier paths.
Fix: _unwrap_claim_lattice_json runs BEFORE all downstream rules.
Detection is conservative (three independent signals: starts-with-
brace AND "claims" key AND "text" key) so plain-prose answers
pass through unchanged. Multi-claim envelopes concatenate as discrete
sentences (extract_claim_spans treats each as its own span).
Malformed JSON falls back to the original answer — no silent
rewriting on broken input.
Smoke result on the Iceland Arborist case
ans: {"claims":[{"text":"The current president of Iceland is
Ólafur Ragnar Grímsson.","evidence_ids":["E1"]}]}
gold: {{Infobox Political post |post = President |body = Iceland
|incumbent = [[Ólafur Ragnar Grímsson]] ...}}
before: UNGROUNDED → FABRICATED (then WRONG after calibration)
after: short_entity_grounded → CORRECT_GROUNDED
pytest: 27/27 (added 7 unwrap-coverage tests covering single-claim
envelopes, multi-claim concatenation, plain-prose passthrough,
malformed-JSON tolerance, unrelated-JSON passthrough, and the
end-to-end Arborist-envelope CG flow). Self-test 4/4 unchanged.
Re-rescores of 17:01 sweep + phase 1 sweep run after this commit
to measure final Arborist scorecard improvement.
russell@unturf.com
3450e8a281