Graphite Stack

Validate a declared multi-PR stack plan and persist it as the stack-plan-<stack> resource: enforces a strict linear chain via validateStackShape (base relations are explicit fields, never inferred) AND a complete, non-overlapping acceptance-criterion partition (every criterion maps to exactly one unit). Throws-and-writes-nothing on any inferred/ambiguous/cyclic/gapped/duplicate ordering or a criterion assigned to two units or to none; a degenerate one-unit plan is legal and matches the single-PR

Finalize one stack unit's commit: reuses the single-commit invariant PER UNIT — asserts the worktree is clean, HEAD^ === unitBaseSha (the unit's declared parent head, or the repo base for unit 0), and exactly one commit ahead (git rev-list --count unitBaseSha..HEAD === 1) — then persists a per-unit stack-unit-<stack>-<index> evidence record pinned to the unit's base and head SHA. Fail-closed on a multi-commit unit (must be re-scoped into two units) or a unit whose parent SHA differs from its dec

Restack every unit above a patched unit: after a patch to unit k rewrites its head SHA, rebases each unit k+1..n onto its (new) parent head via `git rebase --onto` (gt-version-independent), asserts each restacked unit is STILL exactly one commit ahead of its new parent and the chain stays linear, recomputes each unit's head SHA, and records a stack-restack-<stack> audit trail of old->new SHA per unit, marking unit k and every restacked unit stale so their evidence is regenerated. The cascade is

Validate that the whole stack works as a whole: asserts the live stack is linear and each unit's actual parent matches the DECLARED plan baseUnit (parentage read from git, compared to the plan — never `gt log`), computes the composed head = the topmost unit's tip, asserts the supplied unitTipShas equals the restacked reality in order (rejecting any mixed/stale SHA), and persists a composed-head-validation-<stack> artifact pinning composedHeadSha AND the ordered unitTipShas. A degenerate one-unit

Submit a validated stack as gated, idempotent, ordered draft PRs: bottom-up per unit, `gt track <branch> --parent <parentBranch> --no-interactive` with the parent read from the DECLARED plan (never inferred); then checks `gh pr list --head <branch>` ground truth — if a conforming OPEN DRAFT PR already exists at the unit's expected head+base it is recorded as reused (skip submit, no duplicate), else `gt submit --draft` and the resulting PR is verified per unit (headRefName/headRefOid/baseRefName/