Use when someone asks what an X2 skill does, which skill to run next, how the gates work, or where an artifact lives. A quick in-flight reference; for the method's rationale, read X2.md at the x2-method repo root.
Use immediately after gate 1 (stories approved) to create the project repo from the kernel edition and make the method durable inside it. Also use when an existing X2 project is missing its CLAUDE.md standing constraints or its turn ledger. Do not use before stories are approved, and never use it to modify the kernel itself.
Use after the repo is seeded to run the D-000 five-lens decomposition, record persistent schema decisions, define slice one, and start the deltas file. Also use when a stays-ahead decision (decomposition, schema) must be revisited. Do not use for per-slice implementation decisions; those are D-0xx record-gaps raised during implement.
Use when an X2 project completes (or reaches a major milestone) to run the extraction loop, the quality feedback that folds the project's evidence back into the method. Reads the turn ledger and decision records, computes the metric and the per-decision churn table, distils sanitized candidates, confirmations, and negative-space nominations, and holds everything for a rulings pass. Do not use mid-slice (that is the normal intake flow), and never let raw project material cross into the public method.
Use when the prototype is approved at Claude Design (gate 2a) and a slice's portion must be copied down into the repo and locked. Also use when a spine revision touches an already-locked portion and it must be re-locked. Requests gate 2b (the lock). Do not use before gate 2a, and do not derive tests here; that is derive-tests, after the lock.
Use when starting an X2 project, when the problem domain has no approved epic story set, or when new scope needs stories added to an existing set. Runs problem discovery and produces epic-level stories, then requests gate 1 (stories approved). Do not use to author acceptance criteria or a requirements document, and do not use for anything downstream of gate 1.
Use when an existing project that was not built with X2 must be migrated to run under it, with documentation sprawl to dissolve, stories to harvest at epic altitude, an as-built design to baseline, and existing enforcement to map and arm. Runs the migration on a dedicated branch with three human gates. Do not use for a new project (that is seed), and do not use it to redesign the product or refactor code beyond what arming the enforcement requires.
Use only after the lock (gate 2b) is on record for the slice portion, to derive the fidelity ledger and acceptance scenarios from the locked prototype. Triggers when a portion is newly locked or re-locked. Never use before the lock, and never use it to hand-author prototype-fidelity test cases from prose.