Spec-Harness: Measuring and Improving Behavioral Adequacy of LLM-Synthesized Formal Specifications — Paper

Abstract

-cross Abstract: Formal specifications play a central role in ensuring software reliability, yet automatically synthesizing high-quality specifications remains difficult and often requires domain expertise. Recent work has applied large language models to generate specifications in the Java Modeling Language (JML), reporting high verifier pass rates. But passing a verifier only confirms that an implementation is consistent with a specification, not that the specification is meaningful. A trivial postcondition such as ensures true satisfies any verifier while saying nothing about the code. How much behavior, then, does a verifier-accepted specification actually capture? In this work, we first compare classical and prompt-based JML synthesis approaches under a unified setup, and find that prompt optimization through verification feedback raises pass rates but reaches a clear ceiling. We then introduce Spec-Harness, a framework that measures the behavioral adequacy of a specification along four dimensions of precondition and postcondition correctness and completeness, using Hoare-triple based symbolic verification and input/output mutation. Spec-Harness reveals that many verifier-accepted specifications, including optimized ones, are behaviorally weak, over- or under-constraining inputs and outputs in ways the verifier cannot see. Finally, we show that Spec-Harness works as a feedback signal that helps coding agents synthesize specifications with higher behavioral adequacy, including general-purpose agents such as Codex CLI and Claude Code, as well as VeriAct, a JML-specialized agent we build for this study.

Authors 3

Md Rakib Hossain Misu, Iris Ma, Cristina V. Lopes

Specification

Official page: arxiv.org/abs/2604.00280
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh
Arxiv announce type: replace
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh
arXiv id: 2604.00280
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh
Categories: cs.SE, cs.AI
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh
PDF: arxiv.org/pdf/2604.00280
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh
Primary category: cs.SE
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh
Published: 11 Sept 2026
Source:arXiv (Atom API + RSS)T1observed 2 h agohigh

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T19

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2 h ago

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Authors: Md Rakib Hossain Misu, Iris Ma, Cristina V. Lopes

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Value	Valid from → to	Status	Source	Confidence	Extractor
Md Rakib Hossain Misu, Iris Ma, Cristina V. Lopes	11 Sept 2026 21:03 UTC → current	current	arXiv (Atom API + RSS)T1	high	deterministic

Claims are temporal and append-only: a new observation closes the previous claim (valid_to) instead of overwriting it. Conflicting claims from different sources are kept side by side and flagged — never averaged. Methodology →

11 Sept 2026
New paperPaperSpec-Harness: Measuring and Improving Behavioral Adequacy of LLM-Synthesized Formal Specifications
New paper: Spec-Harness: Measuring and Improving Behavioral Adequacy of LLM-Synthesized Formal Specifications
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Source	Document	Type	Tier	Last observed	Snapshots
arXiv (Atom API + RSS)	rss.arxiv.org/rss/cs.AI	feed	T1· Official	2 min ago	1

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