@@ -0,0 +1,57 @@
+---
+'@objectstack/spec': minor
+---
+
+feat(spec): every `composeStacks` conflict refusal carries an ADR-0112 envelope — six new `STACK_COMPOSE_*` codes beside the `defineStack` family
+
+`composeStacks` refuses six authored-entity conflicts, and until now every one of them threw
+`new Error(message)` with `code` and `status` both `undefined`. The `defineStack` family in the
+same file has carried the envelope since #15963, so `packages/spec/src/stack.zod.ts` held two
+refusal families that are the same thing to an author — a stack refused at authoring time,
+through the same callers — and two different things to a consumer branching on `error.code`.
+
+Every message in the family carries the literal `composeStacks conflict:` prefix, which is how it
+is located: FIVE of the six raise inside helper functions 300-800 lines above `composeStacks`'
+own body, so reading the function the defect is named after finds one of them.
+
+| refusal | raised by | code |
+| :--- | :--- | :--- |
+| a single-valued top-level key declared with different values by two stacks | `composeSingleValue` | `STACK_COMPOSE_KEY_CONFLICT` |
+| `functions` authored in the map form by one stack, the array form by another | `composeFunctions` | `STACK_COMPOSE_FUNCTIONS_SHAPE_CONFLICT` |
+| two stacks defining one handler name | `composeFunctions` | `STACK_COMPOSE_FUNCTION_CONFLICT` |
+| under `objectConflict: 'merge'`, an object-level collection other than `fields` declared differently | `refuseUnmergeableCollections` | `STACK_COMPOSE_COLLECTION_CONFLICT` |
+| the same object name in two stacks under the default `objectConflict: 'error'` | `mergeObjects` | `STACK_COMPOSE_OBJECT_CONFLICT` |
+| a cross-stack action key collision | `collectComposedActionKeyCollisions` | `STACK_COMPOSE_ACTION_KEY_COLLISION` |
+
+Each carries `status: 422` — an unprocessable authored entity, not a server fault — and the
+findings the site collected in `issues`, one entry per finding. **Message text is byte-for-byte
+unchanged at every site**: this adds the machine-readable half, it rewords no sentence, and the
+message pins across the repo read the prose they always did.
+
+One code per refusal site rather than a shared `STACK_COMPOSE_CONFLICT` catch-all — the
+granularity the `defineStack` family landed with, and the granularity the ADR-0112 ledger's
+boot-refusal class already had before it. The `STACK_COMPOSE_*` spelling says what the
+per-stack family's spellings cannot: the defect is a disagreement BETWEEN stacks, each of which
+is legal on its own, so the fix is in the composition rather than in one malformed stack.
+`STACK_CROSS_REFERENCE_INVALID` stays the deliberate exception in the other direction — its
+per-stack and artifact passes share one code because they are one rule family over two scopes.
+
+All six are registered in `ERROR_CODE_LEDGER` under `@objectstack/spec`, under the ruling that
+every code shipped in `dist` is the published face, door or no door. No wire door raises them:
+`composeStacks` runs at authoring and boot time, and the reading was re-measured here — zero
+`composeStacks` call sites under `packages/runtime/src` + `packages/rest/src` (7 non-test
+occurrences, all doc comments or message prose in one file), with `defineStack` lighting the
+same probe 31 times across 8 files as the positive control.
+
+Not narrowed: `composeStacks` accepts and refuses exactly the inputs it did before, and no export
+changes — the error classes stay module-local, as every member of the `defineStack` family is,
+because `packages/spec/src/index.ts` re-exports the module with `export *` and the ADR-0112
+contract is the `code` / `status` pair read structurally.
+
+⛔ The seventh bare `Error` in that file is deliberately untouched:
+`composeStacks internal error: no source stack recorded for composed object …` is the code
+discovering its own bookkeeping is inconsistent, not an authored entity being refused. Filing it
+at 422 would tell an author their stack is invalid when the defect is ours. Whether it takes a
+500-class envelope of its own is a separate decision.
+
+Clause-②: yes