ReqWeaver: Stage-Aligned Requirement Management for Greenfield Repository Generation

Building a repository from scratch relies on a requirements document, but the requirements that need to be considered together change as development proceeds. Full-document input leaves agents to identify these combinations for each task, while reading on demand requires them to recognize missing information. We introduce ReqWeaver, which freezes exact source-to-stage bindings before coding and delivers the assigned passages at stage entry without a retrieval query. Completed-stage packets are retired and selected past outputs compacted; shared requirements can reappear in later packets. Optional contract compilation organizes dispersed requirements and records supplementary design choices. We evaluate ReqWeaver with three stochastic generation runs on 36 NL2Repo-Bench and 30 RepoGenesis tasks. With GPT-5.4-mini and OpenHands, ReqWeaver reaches 46.47% versus 37.20% NL2Repo-Bench Pass ($+9.28$ percentage points; 95% confidence interval (CI), $+0.79$ to $+17.83$) and 78.45% versus 55.03% RepoGenesis Pass ($+23.42$ percentage points; 95% CI, $+2.22$ to $+44.18$). Using the third ReqWeaver run block in the main evaluation and controls with the same frozen plans, evidence binding and Projection jointly reduce total tokens, including planning, by 10.56% relative to disabling both. Code is available at https://anonymous.4open.science/r/ReqWeaver-72D4/.