Reliably healable repairs run silently — the user-gated Repair banner retires

General ruling (2026-07-29): app-initiated covers every reliably healable repair — unambiguous, content-lossless — because heals are auditable: Pro's separate heal commit is the durable trail, base happens quietly, and a heal that changes user content announces with a warning-tone notice, never a consent gate. The user-gated class stays defined but has no current members. Duplicate-id healing goes silent under Lanework-owns-the-board (free to re-mint UUIDs at will): no condition banner, no Repair button — a scheduled heal remints withheld occurrences (memo-guarded, disk re-verified, no-op on vanished duplicates) and posts "Repaired duplicate id — 'Fix login'". Winner rule unchanged: earlier commit on git boards, filesystem birth date then traversal order without history. 06 keeps the Repair verb as the heal commit's name; 13 moves the remint outside undo with all heals. Dissolves the Repair-has-no-Nexus-row contradiction — no command, no row owed.

Board: Contradictions card ce5e7f60 → Resolved (lane now empty); Implementation card 50ed2b5d (Active) retitled "Dedupe duplicate ids and heal them silently" and realigned mid-flight.

Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97
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@@ -43,7 +43,7 @@ The **one named exception** is transient UI state rendering things that don't ex
### Live-reload resilience ### Live-reload resilience
- **A failed reload never replaces a good snapshot.** Fail-fast (01-storage-format.md) is the *initial-load* contract, where there is nothing to fall back on. Once a board is open, a watcher-triggered reload that fails (unparseable YAML, missing required fields — typically a non-atomic external write caught mid-flight) keeps the last good snapshot on screen and raises a **non-modal banner** carrying fail-fast's specifics (offending path + what's wrong). The watcher keeps watching; the next successful reload clears the banner automatically — transient breakage self-heals without the user losing the board, persistent breakage stays loudly visible. Editing is not locked out: writes go through the Writer as usual (the breakage is per-file and localized), and the reload debounce already absorbs most momentary invalid states before they surface. - **A failed reload never replaces a good snapshot.** Fail-fast (01-storage-format.md) is the *initial-load* contract, where there is nothing to fall back on. Once a board is open, a watcher-triggered reload that fails (unparseable YAML, missing required fields — typically a non-atomic external write caught mid-flight) keeps the last good snapshot on screen and raises a **non-modal banner** carrying fail-fast's specifics (offending path + what's wrong). The watcher keeps watching; the next successful reload clears the banner automatically — transient breakage self-heals without the user losing the board, persistent breakage stays loudly visible. Editing is not locked out: writes go through the Writer as usual (the breakage is per-file and localized), and the reload debounce already absorbs most momentary invalid states before they surface.
- **Duplicate-id detection surfaces as a repairable condition** (settled): the loader's board-wide dedupe (01-storage-format.md ▸ Fractal layout rules) withholds losing occurrences from every snapshot; a warning-tone condition banner names them and offers **Repair** — a Writer remint under user intent (the loader itself never writes). The condition heals when the duplicates are gone, however they go — Repair here, a repair elsewhere, a hand-deleted copy. - **Duplicate-id detection heals silently** (re-ruled 2026-07-29, superseding the repairable-condition banner): the loader's board-wide dedupe (01-storage-format.md ▸ Fractal layout rules) withholds losing occurrences from every snapshot; a scheduled heal remints them through the Writer (the loader itself never writes) and a warning-tone notice reports the repair — no banner, no button, nothing waits on consent. The withheld window is one heal cycle, not a standing condition; a remint racing a vanished duplicate (repaired elsewhere, a hand-deleted copy) is a no-op, never an error.
- **The watcher is self-reconciling, never trusted blindly** (settled): every reload is already a full tree walk producing a value-type snapshot, so recovery from any blind window is always the same act — reload. A **reconciling reload** runs on wake-from-sleep and on app re-activation (debounced; an identical tree swaps in value-equal, so quiet reconciliations cost nothing visible), on any FSEvents flag admitting missed events (`MustScanSubDirs`, queue overflow — degrade to the reload rather than trust the gap), and after any stream re-creation. **Streams die and are recreated, not merely kept**: a volume unmount kills the stream with its root; the vanished-root and rename re-resolution rules (below) attach a *fresh* stream at the current root when it returns, reconciling reload included. A silently stale board — the worst failure for a files-are-truth app — is structurally excluded: every known blind window ends in a reload. **A reconcile request arriving mid-bracket is banked** (settled): the mandatory post-bracket reload delivers as the *reconciling* kind rather than app-mediated — an explicit reconciliation is never silently lost. FSEvents missed-events flags arriving mid-bracket are, by contrast, simply swallowed: the post-bracket reload is a full walk either way, and only the origin tag differs (it feeds commit attribution and the VoiceOver announcement vocabulary — a deliberate asymmetry). - **The watcher is self-reconciling, never trusted blindly** (settled): every reload is already a full tree walk producing a value-type snapshot, so recovery from any blind window is always the same act — reload. A **reconciling reload** runs on wake-from-sleep and on app re-activation (debounced; an identical tree swaps in value-equal, so quiet reconciliations cost nothing visible), on any FSEvents flag admitting missed events (`MustScanSubDirs`, queue overflow — degrade to the reload rather than trust the gap), and after any stream re-creation. **Streams die and are recreated, not merely kept**: a volume unmount kills the stream with its root; the vanished-root and rename re-resolution rules (below) attach a *fresh* stream at the current root when it returns, reconciling reload included. A silently stale board — the worst failure for a files-are-truth app — is structurally excluded: every known blind window ends in a reload. **A reconcile request arriving mid-bracket is banked** (settled): the mandatory post-bracket reload delivers as the *reconciling* kind rather than app-mediated — an explicit reconciliation is never silently lost. FSEvents missed-events flags arriving mid-bracket are, by contrast, simply swallowed: the post-bracket reload is a full walk either way, and only the origin tag differs (it feeds commit attribution and the VoiceOver announcement vocabulary — a deliberate asymmetry).
- **App-initiated git churn is bracketed.** Operations the app runs itself (pull-rebase, branch switch, undo restore — 06-history-undo.md, 07-sync-collab.md) suspend watcher reloads for their duration and finish with one full reload — half-checked-out trees are never rendered. **The bracket also locks writes** (settled): for its duration the board is read-only with exactly the failed-reload lock's scope — mutating commands disable via menu validation, drops are refused, selection/navigation/search/copy-out stay live. 07's interaction-rest rule composes: the bracket starts only at gesture rest, so nothing in flight is interrupted; the lock ends with the final reload — seconds, honestly signaled by the operation's in-progress banner row (▸ The banner surface). External git activity (the user running git in a terminal) can't be bracketed: the debounce coalesces its churn, and a transiently inconsistent but parseable tree may render briefly and heals on the next event — accepted. - **App-initiated git churn is bracketed.** Operations the app runs itself (pull-rebase, branch switch, undo restore — 06-history-undo.md, 07-sync-collab.md) suspend watcher reloads for their duration and finish with one full reload — half-checked-out trees are never rendered. **The bracket also locks writes** (settled): for its duration the board is read-only with exactly the failed-reload lock's scope — mutating commands disable via menu validation, drops are refused, selection/navigation/search/copy-out stay live. 07's interaction-rest rule composes: the bracket starts only at gesture rest, so nothing in flight is interrupted; the lock ends with the final reload — seconds, honestly signaled by the operation's in-progress banner row (▸ The banner surface). External git activity (the user running git in a terminal) can't be bracketed: the debounce coalesces its churn, and a transiently inconsistent but parseable tree may render briefly and heals on the next event — accepted.
- **Selection survives reloads by UUID.** Selection — and every transient state that references items (drag state, pending cut) — is a set of UUIDs over the snapshot, re-resolved when a reload swaps it: items still present stay selected; items that vanished leave the selection silently, no substitute invented — the search filter's hidden-cards-leave-the-selection rule (04-interactions.md) applied to external change. **A container crossing is a vanish for this purpose** (resettled 2026-07-28 — the materialized trash): re-resolution matches UUID *and* container side (board vs `.trash/`), so a foreign move that trashes a selected board card — or restores a selected trash card — ejects it from the selection (and from the pending cut, which 04-interactions.md ▸ Clipboard already states), keeping 04's container-boundary invariant true across reloads. The old effective-liveness ancestor walk is retired with the tombstone model — presence in the snapshot is the whole question. The search filter is deliberately absent from that list: the query string is transient state, but its result set is *derived* — the predicate re-runs against each new snapshot (04's live filter), so a card an agent files mid-search appears the moment the reload lands, and a card edited to no longer match animates out. Kin rules elsewhere: card windows dismiss when their card is deleted or moved to the trash (05-card-window.md), the placeholder is discarded when its lane vanishes (above), and VoiceOver announces a vanished focused card and recovers focus to its lane (10-accessibility.md). App-mediated deletion is deliberately different — an act, not a surprise: ⌫ selects the successor sibling (04-interactions.md ▸ The map). - **Selection survives reloads by UUID.** Selection — and every transient state that references items (drag state, pending cut) — is a set of UUIDs over the snapshot, re-resolved when a reload swaps it: items still present stay selected; items that vanished leave the selection silently, no substitute invented — the search filter's hidden-cards-leave-the-selection rule (04-interactions.md) applied to external change. **A container crossing is a vanish for this purpose** (resettled 2026-07-28 — the materialized trash): re-resolution matches UUID *and* container side (board vs `.trash/`), so a foreign move that trashes a selected board card — or restores a selected trash card — ejects it from the selection (and from the pending cut, which 04-interactions.md ▸ Clipboard already states), keeping 04's container-boundary invariant true across reloads. The old effective-liveness ancestor walk is retired with the tombstone model — presence in the snapshot is the whole question. The search filter is deliberately absent from that list: the query string is transient state, but its result set is *derived* — the predicate re-runs against each new snapshot (04's live filter), so a card an agent files mid-search appears the moment the reload lands, and a card edited to no longer match animates out. Kin rules elsewhere: card windows dismiss when their card is deleted or moved to the trash (05-card-window.md), the placeholder is discarded when its lane vanishes (above), and VoiceOver announces a vanished focused card and recovers focus to its lane (10-accessibility.md). App-mediated deletion is deliberately different — an act, not a surprise: ⌫ selects the successor sibling (04-interactions.md ▸ The map).
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@@ -30,7 +30,7 @@ Git is the undo substrate — on boards that have git. **Git is opt-in per board
The pathfinder's message engine carries over as the model — it is what earns the "semantic" in semantic commit messages, and it stays a pure, testable function: The pathfinder's message engine carries over as the model — it is what earns the "semantic" in semantic commit messages, and it stays a pure, testable function:
- **Pure snapshot diff, no write-site tagging.** Messages compose at commit time from a structural diff of two board snapshots (last-committed vs. current) — never by intercepting operations. Items match by id across the *whole* board, so a lane change is distinguishable from delete+add and a cross-lane move reads as a move. Bookkeeping — `order` changes that preserve sibling sequence (a renumber's rescale — 01-storage-format.md), `modified`/`created`, and an on-touch heal's backfilled `kind` (01-storage-format.md ▸ Validation and healing) — produces no events: a diff touching only those composes nothing. Sequence is what the diff compares, not raw `order` values: an order change that *repositions* an item among its siblings composes Reorder, so a foreign writer's single-file reorder still reads as one. A midpoint-exhaustion renumber batches with the insert or move that triggered it, so its commit reads as that event. - **Pure snapshot diff, no write-site tagging.** Messages compose at commit time from a structural diff of two board snapshots (last-committed vs. current) — never by intercepting operations. Items match by id across the *whole* board, so a lane change is distinguishable from delete+add and a cross-lane move reads as a move. Bookkeeping — `order` changes that preserve sibling sequence (a renumber's rescale — 01-storage-format.md), `modified`/`created`, and an on-touch heal's backfilled `kind` (01-storage-format.md ▸ Validation and healing) — produces no events: a diff touching only those composes nothing. Sequence is what the diff compares, not raw `order` values: an order change that *repositions* an item among its siblings composes Reorder, so a foreign writer's single-file reorder still reads as one. A midpoint-exhaustion renumber batches with the insert or move that triggered it, so its commit reads as that event.
- **Vocabulary**: Add / Delete / Move / Rename / Edit / Restyle / Resize / Reorder over cards, lanes, and the board, plus Attach / Remove for attachment files ("Move card 'Fix login' to Doing", "Rename lane 'Todo' → 'Doing'"), plus **Repair** for the duplicate-id remint ("Repair duplicate of 'Fix login'" — 01-storage-format.md's banner-gated fix; app-mediated, so the composer names it directly instead of reading the folder swap as Permanently delete + Add), plus the trash pair (settled) — **Restore** and **Permanently delete** — distinguished by diff shape alone, keeping the composer a pure snapshot diff: a move into `.trash/` is Delete, a move out of it is Restore ("Restore card 'X'" — drag-to-restore, cut+paste), and an item *leaving the tree entirely* is Permanently delete ("Permanently delete card 'X'" — Delete Immediately, Empty Trash, and any foreign hard removal, which the shape rule catches and describes accurately for free). The trail thereby tells moved-to-trash from gone-forever — the distinction Deleting never forgets (below) asks users to learn. Plural folding applies as usual: Empty Trash reads "Permanently delete 12 cards", cleanly distinct from a multi-select ⌫'s "Delete 12 cards". One commit per debounce window: a single event is the subject (with a detail body where one helps); several events of one kind fold into a plural subject, with shared destinations preserved ("Move 3 cards to Done"); genuinely mixed windows fall back to "Update board" — always with a bulleted body naming every event, so the oneline log stays scannable and the full message stays complete. - **Vocabulary**: Add / Delete / Move / Rename / Edit / Restyle / Resize / Reorder over cards, lanes, and the board, plus Attach / Remove for attachment files ("Move card 'Fix login' to Doing", "Rename lane 'Todo' → 'Doing'"), plus **Repair** for the duplicate-id remint ("Repair duplicate of 'Fix login'" — 01-storage-format.md's silent scheduled heal, re-ruled 2026-07-29 from its former banner gate; app-mediated and heal-marked, so its separate heal commit names the remint directly instead of reading the folder swap as Permanently delete + Add), plus the trash pair (settled) — **Restore** and **Permanently delete** — distinguished by diff shape alone, keeping the composer a pure snapshot diff: a move into `.trash/` is Delete, a move out of it is Restore ("Restore card 'X'" — drag-to-restore, cut+paste), and an item *leaving the tree entirely* is Permanently delete ("Permanently delete card 'X'" — Delete Immediately, Empty Trash, and any foreign hard removal, which the shape rule catches and describes accurately for free). The trail thereby tells moved-to-trash from gone-forever — the distinction Deleting never forgets (below) asks users to learn. Plural folding applies as usual: Empty Trash reads "Permanently delete 12 cards", cleanly distinct from a multi-select ⌫'s "Delete 12 cards". One commit per debounce window: a single event is the subject (with a detail body where one helps); several events of one kind fold into a plural subject, with shared destinations preserved ("Move 3 cards to Done"); genuinely mixed windows fall back to "Update board" — always with a bulleted body naming every event, so the oneline log stays scannable and the full message stays complete.
- **Implied events don't steal the subject**: deleting a lane with five cards reads "Delete lane 'X'" with the card deletions as body bullets — not "Update board". - **Implied events don't steal the subject**: deleting a lane with five cards reads "Delete lane 'X'" with the card deletions as body bullets — not "Update board".
- **Non-snapshot files commit too** (settled — the repo tracks more than the model: the agent guide, `CLAUDE.user.md`, the seeded `.gitignore`, and strays at every level): the committer **stages the whole board root** — whatever `git status` shows, `.gitignore` respected, **open Edit sessions still staged around** (settled): the session card's folder stays excluded exactly as in Rules ▸ Auto-commit, whole-root staging widening *what* commits, never overriding the exclusion — and its commit condition is the *tree*, not the snapshot diff, so a stray-only window commits rather than leaving the tree dirty (firing mid-session, it commits the strays and leaves the session folder untouched) (a permanently dirty stray would break branch switch's cannot-fail-dirty guarantee and void flush-before-overwrite for every file the model can't see). The composer's input extends accordingly: beside the snapshot diff it receives the changed-path list, and non-snapshot paths compose **path-shaped events**`CLAUDE.md` composes "Update agent guide (vN)", the version read from the guide's marker first line (a pure function of file content, *not* write-site tagging — the no-interception rule stands); any other non-snapshot path composes "Update '⟨path⟩'", folding plural ("Update 3 files"). Model events keep the subject when present; non-snapshot changes then ride as body bullets — recorded, never silently absorbed under an unrelated subject. Attribution needs no new rule: the EchoLedger (02-architecture.md) is path-keyed, so the app's guide write classifies app-mediated by its receipt (the mechanism behind the guide-attribution exception below) and a stray edit classifies foreign, the two-commit split applying per file as everywhere else. - **Non-snapshot files commit too** (settled — the repo tracks more than the model: the agent guide, `CLAUDE.user.md`, the seeded `.gitignore`, and strays at every level): the committer **stages the whole board root** — whatever `git status` shows, `.gitignore` respected, **open Edit sessions still staged around** (settled): the session card's folder stays excluded exactly as in Rules ▸ Auto-commit, whole-root staging widening *what* commits, never overriding the exclusion — and its commit condition is the *tree*, not the snapshot diff, so a stray-only window commits rather than leaving the tree dirty (firing mid-session, it commits the strays and leaves the session folder untouched) (a permanently dirty stray would break branch switch's cannot-fail-dirty guarantee and void flush-before-overwrite for every file the model can't see). The composer's input extends accordingly: beside the snapshot diff it receives the changed-path list, and non-snapshot paths compose **path-shaped events**`CLAUDE.md` composes "Update agent guide (vN)", the version read from the guide's marker first line (a pure function of file content, *not* write-site tagging — the no-interception rule stands); any other non-snapshot path composes "Update '⟨path⟩'", folding plural ("Update 3 files"). Model events keep the subject when present; non-snapshot changes then ride as body bullets — recorded, never silently absorbed under an unrelated subject. Attribution needs no new rule: the EchoLedger (02-architecture.md) is path-keyed, so the app's guide write classifies app-mediated by its receipt (the mechanism behind the guide-attribution exception below) and a stray edit classifies foreign, the two-commit split applying per file as everywhere else.
- **Healing mutations commit separately** (ruled 2026-07-29 — 01-storage-format.md ▸ Validation and healing): a debounce window holding a scheduled heal's changes alongside anyone else's splits the heal's paths into their own commit — the two-commit split's mechanism with a third class, keyed by the Writer's heal-marked receipts in the EchoLedger (attribution machinery, like the author split; the composer stays a pure diff reader and names the heal commit from its own diff shape — a loose-file relocation reads as its Attach-shaped event, a legacy migration's move into `.trash/` as Delete, the guide as "Update agent guide (vN)"; that the shape vocabulary doesn't say "healed" is accepted, the banner already told the user). Mostly redundant — each scheduled healer runs its own bracket at the reload tail, normally its own window — but the split makes separation a guarantee rather than a timing accident. On-touch and inline heals are structurally exempt: each lives inside a host write or its triggering gesture and rides that commit, the backfilled `kind` composing no event per the bookkeeping rule above. - **Healing mutations commit separately** (ruled 2026-07-29 — 01-storage-format.md ▸ Validation and healing): a debounce window holding a scheduled heal's changes alongside anyone else's splits the heal's paths into their own commit — the two-commit split's mechanism with a third class, keyed by the Writer's heal-marked receipts in the EchoLedger (attribution machinery, like the author split; the composer stays a pure diff reader and names the heal commit from its own diff shape — a loose-file relocation reads as its Attach-shaped event, a legacy migration's move into `.trash/` as Delete, the guide as "Update agent guide (vN)"; that the shape vocabulary doesn't say "healed" is accepted, the banner already told the user). Mostly redundant — each scheduled healer runs its own bracket at the reload tail, normally its own window — but the split makes separation a guarantee rather than a timing accident. On-touch and inline heals are structurally exempt: each lives inside a host write or its triggering gesture and rides that commit, the backfilled `kind` composing no event per the bookkeeping rule above.
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@@ -6,7 +6,7 @@ The undo/redo substrate for base Lanework (12-editions.md), filling the one gap
- **One stack per board, owned by the board session.** Not per-window: every window over a board (board window, its card windows) shares the store and shares the stack. `window.undoManager` for board surfaces returns the session's manager; 06 ▸ Undo routing applies unchanged — text-editing surfaces get their session-scoped text undo, everywhere else ⌘Z/⇧⌘Z hit the board stack. Undo is board-local, exactly as git undo was. - **One stack per board, owned by the board session.** Not per-window: every window over a board (board window, its card windows) shares the store and shares the stack. `window.undoManager` for board surfaces returns the session's manager; 06 ▸ Undo routing applies unchanged — text-editing surfaces get their session-scoped text undo, everywhere else ⌘Z/⇧⌘Z hit the board stack. Undo is board-local, exactly as git undo was.
- **Registration at the Writer boundary.** Every app-mediated mutation already passes through the Writer as a `WriteOperation` (02-architecture.md) — that closed enum is the exact inventory of undoable operations. Each Writer call site registers the inverse operation, computed from the pre-write snapshot the store already holds: move → move back (original lane, original `order`); reorder → restore original `order`; rename → restore title; restyle → restore prior style; resize → restore prior width; Edit-session body save → restore prior body bytes; card or lane delete (⌫) → move back out of `.trash/` (lanes rejoined the trash 2026-07-29 — the recreate-from-capture inverse retires with the last destructive delete); restore-by-move → move back in; create → remove the created folder. - **Registration at the Writer boundary.** Every app-mediated mutation already passes through the Writer as a `WriteOperation` (02-architecture.md) — that closed enum is the exact inventory of undoable operations. Each Writer call site registers the inverse operation, computed from the pre-write snapshot the store already holds: move → move back (original lane, original `order`); reorder → restore original `order`; rename → restore title; restyle → restore prior style; resize → restore prior width; Edit-session body save → restore prior body bytes; card or lane delete (⌫) → move back out of `.trash/` (lanes rejoined the trash 2026-07-29 — the recreate-from-capture inverse retires with the last destructive delete); restore-by-move → move back in; create → remove the created folder.
- **What is not undoable** (settled): **Permanently delete** (Delete Immediately, Empty Trash) — `purgeIsUnrecoverable` stays true in base, and the existing confirmation rule (03-board-ui.md) already fires on all base boards, since none have git history: the confirm *is* the safety. **Repair** (01-storage-format.md's duplicate-id remint) — undoing a remint would recreate the duplicate id the operation exists to remove. Both match their existing "destructive, confirmed, final" posture. - **What is not undoable** (settled): **Permanently delete** (Delete Immediately, Empty Trash) — `purgeIsUnrecoverable` stays true in base, and the existing confirmation rule (03-board-ui.md) already fires on all base boards, since none have git history: the confirm *is* the safety. **The duplicate-id remint** (01-storage-format.md — a silent scheduled heal since 2026-07-29, formerly the user-gated Repair) — heals aren't user gestures, so nothing enters the stack, and undoing one would recreate the duplicate id it exists to remove. Permanently delete matches its existing "destructive, confirmed, final" posture; the remint sits outside undo as all heals do.
- **Coalescing follows commit granularity** (settled): one gesture, one undo step — a multi-card move is one step with a plural title; an Edit session is one step, registered at the Edit→Preview flip (the effective Save — 05-card-window.md); a styling batch is one step (03's one-gesture-one-commit rule, substrate swapped). The 06 vocabulary supplies menu titles ("Undo Move 3 Cards"), via NSUndoManager's dynamic retitling — the same naming machinery both editions use. - **Coalescing follows commit granularity** (settled): one gesture, one undo step — a multi-card move is one step with a plural title; an Edit session is one step, registered at the Edit→Preview flip (the effective Save — 05-card-window.md); a styling batch is one step (03's one-gesture-one-commit rule, substrate swapped). The 06 vocabulary supplies menu titles ("Undo Move 3 Cards"), via NSUndoManager's dynamic retitling — the same naming machinery both editions use.
- **Session-only persistence** (settled): the stack lives with the board session and dies at close/quit — standard macOS behavior. Git undo's survive-relaunch property is a Pro difference, stated honestly (12's matrix). - **Session-only persistence** (settled): the stack lives with the board session and dies at close/quit — standard macOS behavior. Git undo's survive-relaunch property is a Pro difference, stated honestly (12's matrix).
- **Foreign writes never join the stack** (settled): NSUndoManager can only undo what the app mediated. An agent's or hand edit is not a step — the honest capability gap vs Pro (12's matrix). Foreign changes also do not clear the stack wholesale; collisions are handled lazily, per step, by validation: - **Foreign writes never join the stack** (settled): NSUndoManager can only undo what the app mediated. An agent's or hand edit is not a step — the honest capability gap vs Pro (12's matrix). Foreign changes also do not clear the stack wholesale; collisions are handled lazily, per step, by validation: