Forge: Fault-Oriented Rework Code Generation for Executable Interlocking Assembly

Large language models have demonstrated strong capabilities in structured rea- soning and code generation, yet identifying an assembly fault does not guarantee the ability to generate executable rework programs. In interlocking assemblies, a locally plausible repair program may violate blocking dependencies, omit required recovery operations, or terminate in an incorrect configuration. We identify this challenge as fault-conditioned executable rework generation, where models must jointly reason about structural failures and generate programs that restore con- strained assembly states. To benchmark this capability, we introduce FORGE- Bench, containing 4,000 tasks across 26 interlocking assemblies with five as- semblies held out for evaluating generalization to unseen structures. We further propose FORGE (Fault-Oriented Rework Code Generation for Executable In- terlocking Assembly), a structured state-to-program framework that decomposes rework generation into Rework Structuring and Action Grounding. Rework Structuring captures fault-induced recovery dependencies, while Action Ground- ing maps these dependencies into state-conditioned executable actions. Experi- ments show that locally reasonable repair code is insufficient for reliable assembly recovery, and that connecting structural recovery reasoning with executable action realization is essential for verified target restoration.