EviScope: Paired Counterfactual Evidence Diagnostics for Faithful and Efficient Grounded Language Models

Suryadeep Singh Deswal


Abstract
Grounded language-model systems are often evaluated by final answer accuracy, yet a correct answer can be unsupported, drawn from the wrong source, or produced when evidence is insufficient or contradictory. We introduce EviScope, a paired counterfactual benchmark that holds the question fixed while adding, removing, distracting, or contradicting its evidence. EviScope-v1.1 contains 40 four-condition quartets with repaired counterfactual claims and span-level support labels for automatic evaluation. Across 960 gold-blind generations from Qwen2.5-7B, Llama 3.1 8B, and Gemini 3.5 Flash, paired metrics expose model-dependent grounding behavior that answer accuracy hides. On two local open models, an explicit evidence-action gate underperforms vanilla RAG on QCS: 0.15 vs. 0.50 for Qwen and 0.10 vs. 0.375 for Llama. Gemini reaches 0.944 joint success under both prompts, yet still answers 5% of conflict cases after contradiction insertion. EviScope therefore distinguishes unsupported answering, conflict blindness, and wrong non-answer actions rather than scoring answers alone.
Anthology ID:
2026.groundlm-1.20
Volume:
Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Yimu Wang, Yee Man Choi, Di Wu, Siqi Ouyang, Mozhgan Nasr Azadani, Yi R. (May) Fung
Venues:
GroundLM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
257–262
Language:
URL:
https://aclanthology.org/2026.groundlm-1.20/
DOI:
Bibkey:
Cite (ACL):
Suryadeep Singh Deswal. 2026. EviScope: Paired Counterfactual Evidence Diagnostics for Faithful and Efficient Grounded Language Models. In Proceedings of the 1st Workshop on Grounding Language Models: Learning Faithfully and Efficiently (GroundLM 2026), pages 257–262, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
EviScope: Paired Counterfactual Evidence Diagnostics for Faithful and Efficient Grounded Language Models (Deswal, GroundLM 2026)
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https://aclanthology.org/2026.groundlm-1.20.pdf
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