ADR 0115: under a nested project root, every verb works correctly or refuses loudly

Vocabulary amendment: Current pointers use ratchets → standards, finish → done, scopes → impact where it names the verb; the decision and reasoning are unchanged.

Status: accepted. Complements ADR 0011 (the worktree workflow) and ADR 0003 (named-metric standards).

findRoot roots discern at the nearest ancestor holding discern.toml, with no requirement that this directory is also the git repository's top level. So a project can legitimately sit below its repo's root — a standalone discern project folded into a monorepo is the natural way to get there — and every verb will happily run in that shape. The shape had never been deliberately considered, and the engine silently assumed the root IS the top level in the places where git's path conventions make the two differ:

• git resolves a bare rev:path against the repository top level, so the standard baseline read (git show <main>:discern.toml) found nothing, returned "no baseline", and the never-loosen half of every standard — the guarantee the feature exists for — was silently disabled while the measurement half kept passing.
• git diff --name-only, git status --porcelain, and git log --name-only all emit toplevel-relative paths regardless of cwd, while scope globs, coupling queries, and the strand diagnostic all speak root-relative paths. Changed paths carried the subdir prefix, matched no scope glob, and scope gates silently skipped; the co-change miner's baskets could never match a query; sibling projects' changes leaked in as this project's evidence.

Each failure was silent — fewer gates, not more; a quietly missing advisory; a loosened floor waved through. Meanwhile the worktree lifecycle already refused the shape loudly (start names the layout and the fix), and doctor's "repository shape" check reports it — so the repo held both halves of a posture without ever having chosen one.

Under a nested project root, every engine verb either works correctly or refuses loudly. Silent misbehaviour is the defect; the class is guarded by tests/engine_nested_root_test.ts.

• Git-facing readers normalize to root-relative. repoPathPrefix / stripRepoPathPrefix (in src/engine/scopes/scopes.ts, beside parsePorcelainPaths) resolve the root's prefix inside the repo once and normalize every git-emitted path list: the scope classifier (collectPaths, feeding the gate, status, and impact), the co-change miner, and the fix-stage strand snapshot. Paths outside the project subtree are dropped — a sibling project's changes in a shared repository are not this project's. The standard baseline is read with the cwd-relative rev:./path spelling.
• The worktree lifecycle keeps its refusal. A worktree is a whole-repository checkout; a nested root's copy would nest inside the repo with its discern.toml where nothing looks for it. Both start and accept refuse with the move-it message, and doctor's repository-shape check reports the same fact. Acceptance must refuse too: it cannot classify only the nested project subtree and then fast-forward sibling repository changes. This is a deliberate no: the lifecycle is not being taught the shape.
• Repo-wide reads that only tighten stay repo-wide. The clean-tree guards (standards, --pin, receipts) read git status across the whole repository: under a nested root, sibling dirt blocks with a loud message. Conservative and honest, so it stands.

• A monorepo-nested discern project gets a truthful gate: standards hold their never-loosen guarantee, scope gates fire, coupling answers — verified by the nested-root suite, which pins each key engine path (and the refusals) against one shared fixture. A future git-facing reader that skips the normalization seam fails there.
• The worktree workflow remains unavailable in the shape until someone designs it properly; doctor keeps saying so. Users who want it move discern.toml to the top level or split the repo, exactly as the refusal instructs.
• Receipt renderings may show repo-relative paths, and repo-wide clean-tree guards may block on sibling dirt — cosmetic and conservative respectively, accepted residuals of the split.

• Refuse the shape everywhere (make every verb demand the root be the top level). Honest but heavy-handed: the measurement surface has no structural reason not to work, and hard-refusing would brick done/standards for any monorepo fold-in that works today apart from the silent bugs.
• Support the worktree lifecycle nested (worktrees of the whole repo with re-rooting into the subdir). A real feature with real value, but a redesign of worktree placement, identity, and setup — not a bug fix, and not worth blocking the correctness fixes on.