Refactoring the Build Engine Into Concern-Focused Modules

This sprint had to change the shape of the Rust module before any later extraction could be local. Its brief was narrow: turn the flat file into a directory module and move the plan-source identity code, which had no build context dependency. A fresh agent could hold that because the new module root still contained the rest of the engine, so the only real boundary was preserving re-exports for callers outside the module.

The second sprint applied the pattern to the job model and routing cluster. That code was mostly free functions and data types for deciding what kind of run is being resumed or started, which kept the extraction cohesive. It depended on the first sprint's re-export pattern rather than on any new behavioral change, and the gate did not push back.

This sprint was the first to move a build-context method group, but it was still a descendant module of the root that owned the private fields and many called methods. The brief grouped design authorization, view discovery, clean-slate detection, and the design driver together, so the agent had one concern rather than a slice by line number. It stayed green, which matches the intended boundary: method bodies moved, but the calling shape had not yet become a sibling-module problem.

The map driver was larger than the leaf clusters, but its boundary was clear because it owned the worker-pool flow, unit execution, checkpoints, and map-only helper code. Support methods still lived above it, so the agent could move the driver without solving the later sibling visibility problem. Its green boundary says the map driver was a coherent method cluster at this stage.

This sprint repeated the driver extraction pattern for milestone campaigns. Its scope was the planning, announcement, milestone build, review, and future-milestone helper code, all of which belonged to one run mode. Because the support clusters still stayed in the parent module, the agent could focus on relocating the campaign driver rather than changing call semantics.

This was the closing driver extraction for the first milestone. It moved the flat-sprint loop, including execute, gate, repair, investigate, review, replan, and completion checks, while deliberately leaving the support methods and tests for the next milestone. The boundary was narrow enough for one agent because the sprint driver could still call private root methods as a descendant module.

Gate logic was the first support cluster to move because every later sibling extraction would rely on the visibility pattern it established. The sprint moved planning and gate methods plus the small parsing helpers, then let the compiler identify which driver calls now crossed the sibling boundary. It stayed green, so the first support split proved the approach without needing a repair pass.

The agent cluster was broad because dispatch, prompt rendering, confinement checks, support handling, and sub-build execution are called from many other concerns. That made it a visibility-heavy sprint rather than a logic-heavy one: move the bodies, then make only the sibling calls compile. The run facts show no red gate here, which means the call surface was large but still mechanically bounded.

This sprint moved the finish, merge, and conflict-resolution cluster, including helpers consumed outside the build module. Its boundary was sharper than the agent cluster because it owned the run endgame: merge back, partial finish, resolver handling, and resolver logs. The hard part was preserving public crate paths while moving code, and the sprint landed green.

The final production-code extraction was small in domain but important for completing the method split. It moved commit message generation, card decoration, fallback cards, tree snapshots, and diff helpers out of the root. Because the previous support clusters were already siblings, this sprint mostly finished the same visibility exercise on a narrower plumbing surface.

This sprint carried the last and most verification-sensitive move: the inline test module had to become a test directory without deleting, renaming, weakening, or duplicating tests. The run came under stress here. Its first execute did not finish cleanly, the milestone gate went red, and then the sprint resumed and passed, locating the job's real difficulty in preserving the test suite while changing its shape.