The paper introduces a specification-guided decoding framework that blends large language model generation with symbolic reasoning to enforce formal specifications during output generation. It offers a forward-only variant that guarantees compliance by construction and a backtracking variant that revises earlier choices when later constraints become unsatisfiable. The approach is model-agnostic, requires no retraining, and improves compliance on configuration and constraint-solving benchmarks while reducing repeated inference compared to rejection sampling.
arXiv:2603. 03305v2 Announce Type: replace-cross Abstract: Large language models (LLMs) are increasingly used to generate executable outputs, JSON objects, and API calls, where a single syntax error can make the output unusable.
The paper investigates whether constrained decoding harms or helps large language model (LLM) performance. It introduces a taxonomy of three constraint types—format, validity, and reasoning—and shows that suitable constraints can preserve or even improve performance by eliminating invalid paths. Experiments across multiple model families reveal that perceived performance drops are mainly due to non-equivalent prompting and output formats, while validity constraints boost reliability and reasoning constraints can enhance accuracy when they guide beneficial reasoning trajectories.
arXiv:2601. 22642v2 Announce Type: replace Abstract: Large Language Models (LLMs) show remarkable capabilities, yet their stochastic next-token prediction creates logical inconsistencies and reward hacking that formal symbolic systems avoid.
arXiv:2602. 15983v3 Announce Type: replace-cross Abstract: Large language models (LLMs) can translate natural language into optimization code, but silent failures pose a critical risk: code that executes and returns solver-feasible solutions may encode semantically incorrect formulations---a feasibility--correctness gap reaching 90 percentage points on compositional problems.
RECAST is a new framework that generates datasets with far more constraints per example than existing benchmarks, aiming to push large language models (LLMs) to better follow complex instructions. The authors built RECAST-30K, a 30,000‑instance dataset covering 19 constraint types extracted from real prompt‑response pairs, and showed that fine‑tuning on it improves LLMs’ ability to handle complex tasks without harming general performance. RECAST also provides rule‑based and LLM‑based validators for automatic constraint verification, enabling reward‑based reinforcement learning to further enhance model performance on challenging tasks.
arXiv:2610.01519v1 Announce Type: cross Abstract: Neuro-Symbolic (NeSy) predictors incorporate prior knowledge into the prediction process of neural networks, ensuring that outputs satisfy specified...
The paper introduces MeMoDecode, a decoding framework that enforces both concrete and abstract syntax as well as well‑formedness constraints for domain‑specific languages (DSLs) during large language model generation. By mapping generated text to partial metamodel instances and retrying from the last consistent snapshot, MeMoDecode guarantees consistency without sacrificing alignment metrics. Experiments on four DSLs and six open‑weight LLMs show a 23% average improvement over unconstrained decoding and an 8% improvement over grammar‑constrained decoding, with modest runtime overhead.
arXiv:2602.00612v3 Announce Type: replace Abstract: Diffusion Large Language Models (dLLMs) have demonstrated promising generative capabilities and are increasingly used to produce formal languages d...
Instruction-following ability is critical for deploying large language models in real-world applications, where downstream components depend on the output satisfying specific constraints. Modern deployments increasingly handle the full task in a single LLM call, with one prompt specifying a layered output whose overall artifact, structural sections, and nested fields must each satisfy concrete constraints.
arXiv:2607. 20483v1 Announce Type: new Abstract: Constraining the generation of autoregressive large language models (LLMs) is an important component of integrating language models into formal systems.
The paper examines the limitations of using large language models (LLMs) to translate natural language planning problems into PDDL representations, noting that standard benchmarks often map directly to PDDL and may overstate success. It introduces the concept of "unraveling problems," where concise natural language descriptions correspond to large PDDL structures, and shows that traditional LLM formalizers struggle to scale on such variants. To address this, the authors propose a new paradigm, LLM-as-Higher-Order-Formalizer, where the LLM first generates a high‑level program that encapsulates recurrent logic, which then produces the full PDDL representation, thereby decoupling token output from combinatorial explosion and improving performance on complex tasks.
arXiv:2608. 12426v1 Announce Type: new Abstract: Large language models are increasingly deployed in settings that require simultaneous adherence to multiple explicit constraints - reasoning structure, safety boundaries, output schemas.