Routing Ceilings Are Domain-Independent: Structural Prior Injection in Code Security Vulnerability Detection
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Computer Science > Computation and Language
Title:Routing Ceilings Are Domain-Independent: Structural Prior Injection in Code Security Vulnerability Detection
Abstract:Large language models (LLMs) exhibit a well-documented gap between latent capability and consistent activation: the router hypothesis posits that models possess the knowledge to solve a task but lack reliable internal routing to activate it. Prior work in formal mathematical reasoning (SAIR, Cázares 2026) reports that structural priors (cheatsheets) raise in-distribution performance dramatically, yet collapse below the zero-shot baseline out-of-distribution (OOD) -- and that iterative recalibration amplifies rather than corrects the collapse.
We test whether this phenomenon is cross-domain by reproducing the SAIR design in source-code security vulnerability detection, evaluating three LLMs (GPT-OSS-120B, Llama-3.3-70B, Gemma-4-31B) across three vulnerability categories (CWE-798, CWE-284, and the non-CWE N+1 anti-pattern) spanning syntactic, contextual, and semantic complexity, then transferring cheatsheet-augmented prompts to real-world CVE data from VUDENC (CWE-89, CWE-22).
Our findings replicate and extend SAIR: (F1) structural priors lift semantic-vulnerability recall from 20.0% to 100.0% across all models; (F2) zero-shot performance degrades along a semantic complexity gradient; (F3) the same cheatsheets that saturate synthetic performance amplify distribution-shift collapse on real CVE data (CWE-89: 100% synthetic F1 to 48.9% on VUDENC, -51.1pp); (F5) iterative recalibration produces a v2 cheatsheet that performs worse than v1 on real data, mirroring SAIR's AN45c-vs-AN38 finding.
These results provide evidence that the cross-distribution trade-off surface documented in SAIR generalises to code security, and that the router hypothesis is cross-domain. We argue the structural nature of the collapse motivates distribution-aware training over prompt calibration. Code and evaluation scripts: this https URL
| Comments: | 12 pages, 5 tables |
| Subjects: | Computation and Language (cs.CL); Cryptography and Security (cs.CR) |
| ACM classes: | D.2.5; K.6.5; I.2.7 |
| Cite as: | arXiv:2607.14628 [cs.CL] |
| (or arXiv:2607.14628v1 [cs.CL] for this version) | |
| https://doi.org/10.48550/arXiv.2607.14628
arXiv-issued DOI via DataCite (pending registration)
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Submission history
From: Manuel Israel Cazares [view email][v1] Thu, 16 Jul 2026 06:45:08 UTC (15 KB)
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