suaveplan/openspec/changes/enterprise-gaming-ik-solver/tasks.md

Tasks: enterprise-gaming-ik-solver

0. Pre-flight (non-negotiable)

• 0.1 Confirm clean working tree (git status reports nothing) and no in-flight worktrees with uncommitted work (git worktree list then git status in each)
• 0.2 If any worktrees exist under .claude/worktrees/, account for each one: still-active agent, work-pending-merge, or stale-and-prune. Stale worktrees MUST be removed (git worktree remove) before opening a new one — code that has been lost twice on main is the failure mode this guards against.
• 0.3 Confirm the package set in MANIFEST.md matches find packages -maxdepth 3 -name package.json count. Drift here means a prior change archived without regenerating the manifest.

Phase 1 — Scaffold

• Create gaming/rigs/ik-solver/ (@suaveplan/ik-solver, 0.1.0, sideEffects: false)
• tsconfig.json, vitest.config.ts

Phase 2 — Error codes & constants

• src/error-codes.ts + src/constants/index.ts — DEFAULT_MAX_ITERATIONS, DEFAULT_TOLERANCE

Phase 3 — Types

• src/types/common.ts + common.md

Phase 4 — Vec3 math utils

• src/utils/vec3-math.ts — add/sub/scale/dot/cross/normalize/distance/lerp
• Tests + docs

Phase 5 — Two-bone solver

• src/solvers/two-bone/two-bone.ts — law of cosines analytic solution + pole hint
• Tests (reachable/unreachable targets, degenerate chain)
• Docs

Phase 6 — Look-at solver

• src/solvers/look-at/look-at.ts — quaternion from-to with up-vector and angle clamp
• Tests + docs

Phase 7 — FABRIK solver

• src/solvers/fabrik/fabrik.ts — forward/backward pass, joint constraints, convergence check
• Tests + docs

Phase 8 — Property tests

• tests/property.test.ts — two-bone reach, look-at alignment, FABRIK convergence

Phase 9 — Pre-publish gate

• bunx turbo lint typecheck test --filter=@suaveplan/ik-solver green
• 100% coverage
• Publish: bun scripts/publish.ts --package @suaveplan/ik-solver