Preprint · 2026
The Specification Gap: Coordination Failure Under Partial Knowledge in Code Agents
Camilo Chacón Sartori
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra
Abstract
LLM-based code agents are increasingly used to divide and independently implement parts of a software class — yet how specification completeness shapes their coordination under partial knowledge remains poorly understood from a software engineering perspective. We treat this as an integration problem: when two agents independently generate code for disjoint method groups, they must agree on shared internal data structures without runtime communication. We study this coordination problem across 51 class-generation tasks, varying specification completeness from full docstrings (L0) to bare signatures (L3) and introducing opposing structural biases to stress-test integration. Three findings emerge across three models from two families. First, a persistent specification gap: two-agent integration pass rate drops from 58% to 25% as specification detail is removed, leaving a 25–49pp coordination penalty that persists at every level. Second, an AST-based conflict detector flags structural mismatches at zero LLM cost, reaching 97% precision at L3 — diagnosing where coordination fails but not improving merger-agent repair. Third, a 2×2 factorial recovery experiment shows that restoring the full specification to a merger agent recovers the single-agent ceiling (89%) in our experimental setting, while conflict reports are not statistically distinguishable from zero effect. A gap-decomposition experiment further isolates coordination cost (+16pp) from information asymmetry (+11pp), confirming the two effects are approximately additive. These results support a specification-first view: the specification functions as a coordination contract, and investing in richer specifications is more consequential than post-hoc conflict detection.
Keywords
multi-agent code generation · specification completeness · LLM coordination · conflict detection · software engineering
Cite
@misc{chaconsartori2026specgap,
author = {Chac\'{o}n Sartori, Camilo},
title = {The Specification Gap: Coordination Failure Under
Partial Knowledge in Code Agents},
year = {2026},
note = {Preprint}
}