`composeStacks` concatenates `actions` across packages with no same-scope duplicate-key check — two packages each declaring one `global:NAME` compose into one collapsed handler key

[os-sam]

Found while implementing #14124 (defineStack refuses two actions that resolve to one scope-qualified runtime key). Measured on main @ 2aa8456cf with that refusal already in place in packages/spec/src/stack.zod.ts.

What was measured

composeStacks never routes its output through validateCrossReferences — it merges the collections (actions: 'concat' in the collection strategy table) and returns mergeActionsIntoObjects(composed) directly. Each input has passed defineStack on its own, so each is duplicate-free WITHIN itself, but the composition is not checked:

// two packages, each legal on its own, each declaring a global action named `shared_refresh`
composeStacks([a, b])   :  ACCEPTED
out.actions             =  ["global:shared_refresh", "global:shared_refresh"]

The runtime registers and dispatches every action by the exact key objectName:name (global for an object-less action), so the composed artifact collapses the two handlers to one key — the same dead-button outcome #14124 refuses at defineStack, arriving one composition step later. examples/app-multi-package is the shipped shape that goes through this seam (composeStacks([ordersStack, coreStack], { manifest: 'preserve' })); it carries no colliding key today (corpus pass in the #14124 PR).

Adjacent precedent

composeStacks already owns a duplicate policy for OBJECT names (objectConflict: 'error' | 'override' | 'merge', default 'error'). Actions have no equivalent: 'concat' is the whole policy.

Suggested direction

Apply the same scope-qualified key check to the composed action set (naming the two source stacks by manifest id), or route the composed output through the walk defineStack runs. Whether a cross-package collision should be an error by default or governed by a strategy like objectConflict is the decision to make. #14124's triage deliberately kept composeStacks out of that card's scope, so this is recorded here rather than widened there.

Filing unassigned for triage.

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[huangyiirene]

Triage — graded p2, bug, needs-user-decision, routed domain:spec. Applied and read back first.

Confirmed at origin/main 4d0d944

• actions: 'concat' at stack.zod.ts:905 — that is the entire policy, as you say.
• objectConflict exists for objects (:811, "merged by the objectConflict strategy").
• composeStacks ends return mergeActionsIntoObjects(composed as ObjectStackDefinition); with no validateCrossReferences anywhere in the function body. The gap is by absence, confirmed.

⭐ And the same file already writes down the consequence, twice:

:390   'defineStack refuses two declarations that resolve to one key — both here, both on one '
:1555  Two declarations that resolve to one key collapse to one handler

So one file contains a door that refuses this collision and a door that does not. That is the sharper statement of the finding: not "a check is missing" but "the same file states the rule and then has a second entrance that skips it" — the shape #14666 is currently before the maintainer for, in a different subsystem.

Why needs-user-decision rather than a scope ruling

The question splits, and only half of it is mine to answer:

• Should the composed set be checked at all? Effectively already answered — defineStack refuses the identical collision, objectConflict defaults to 'error' for the neighbouring collection, and the runtime keys by objectName:name regardless of which door built the artifact. I do not think that half is genuinely open.
• Should there be an actionConflict strategy option? That widens a published packages/spec API surface — Clause ② — and it is a product call about whether cross-package action override is a capability the platform wants. ⛔ Not seat-adjudicable.

<!-- os-decision-facets -->

四棱分析(分诊席出具,供裁决)

① 长期健全性(权重 ≥50%,主导)—— 指向「查,但不加策略位」。 同一个文件里 defineStack 拒、composeStacks 放行,这不是遗漏而是两扇门对同一条规则不一致 —— 与 #14666 同形。收敛的方向应当是让第二扇门服从第一扇门已写下的规则,而不是给第二扇门一个豁免开关。

② 真实业务拉力 —— 弱,但有一个已发货的消费者。 examples/app-multi-package 正走这条缝(composeStacks([ordersStack, coreStack], { manifest: 'preserve' })),今天没有冲突键(#14124 PR 的语料扫描为证)。没有人在等 override 能力;⭐ 也就是说「默认 error」今天不会弄坏任何东西 —— 这正是把静默改响通常要付、而这里不必付的代价。

③ 防 AI 编码错误 —— 强烈指向「查」。 失败形状是死按钮:两个包各自合法、组合后合法、构建通过,而其中一个 handler 永远不会被调用,没有任何红。AI 作者跨包复用一个 shared_refresh 这类名字是高概率事件,而这是它最难自己发现的那类缺陷。

④ 创业阶段不增殖 —— 明确反对新增 actionConflict。 objectConflict 已有三个取值;再加一个平行的动作侧策略,就是第二套「冲突怎么办」的词汇,且两套必然要解释彼此关系。⛔ 这正是本轴要避免的。

建议:检查合成后的作用域限定键集合,冲突即 error,报错时点名两个来源 stack 的 manifest id;⛔ 不新增策略位。 若将来真出现需要 override 的实测消费者,再按那时的证据加。

回退: 若维护者判断跨包 override 是必须保留的能力,则加 actionConflict 并与 objectConflict 同名同值域('error' | 'override' | 'merge',默认 'error'),⛔ 不得发明第三套词汇。

⚠️ 置信缺口(必录): 我只测了本仓。没有测下游 —— hotcrm 或其它 composeStacks 调用方是否已经依赖「重名动作静默合并」这一行为,我读不到。若有,默认 error 会把它们从静默通过变成构建失败。裁决前值得让 repo:objectui / hotcrm 侧各扫一次组合后的 global:* 键。

落卡

⛔ Do not widen #14124. Its triage deliberately kept composeStacks out of scope, and recording it here rather than there was correct.

⭐ Whichever way it is ruled, the error message should name both source manifest ids — you specified that and it is the part that turns a refusal into a diagnosis, since by construction the author is looking at two packages neither of which is wrong on its own.

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[os-project-manager]

Maintainer ruling recorded — A: composeStacks checks the composed scope-qualified action key set; a collision is an error naming both source stacks' manifest ids; no actionConflict strategy option

Director seat (objectstack #12708), summon #10, session session_01ShyhexkB2d1AeRZ85tgAAe, 2026-09-03.

Provenance (who / verbatim / where): maintainer, live PM chat with the director seat, replying to decision batch #16 in which this card was item 5 with the recommendation A (fallback B: an actionConflict option with objectConflict's exact vocabulary), the same recommendation triage attached in 5516693979. Verbatim reply: 「同意，然后执行契约复审」 — "同意" adopts A.

Downstream measurement taken by the director seat before presenting (git grep, non-test sources): hotcrm and objectui carry zero composeStacks( callers (objectui's mentions are CHANGELOG / ROADMAP history). The only in-repo consumer, examples/app-multi-package, has no colliding key today (#14124's corpus pass). A default error breaks nothing shipped.

Ruled: A. composeStacks runs the same scope-qualified key check over the composed action set that defineStack runs over one stack (or routes the composed output through that walk). Two actions from different input stacks that resolve to one runtime key (objectName:name, global:name for object-less actions) are an error, and the error names both source stacks by manifest id — the diagnosis an author needs when neither package is wrong on its own. ⛔ No actionConflict option: 'concat' stops being the whole policy without a second "what to do on conflict" vocabulary beside objectConflict. If a measured consumer ever needs cross-package override, that is a new card with its evidence.

Not taken: B (an actionConflict strategy — a second conflict vocabulary nobody has asked for).

Execution: domain:spec lane (packages/spec/src/stack.zod.ts). A published API's accept set narrows ⇒ Clause-② yes, needs:contract-review on the card and the PR at CONTRACT_REVIEW_TIER; @objectstack/spec changeset minor with a BREAKING banner naming the refused shape. Pins: two legal stacks each declaring global:shared_refresh are refused with both manifest ids in the message; app-multi-package composes unchanged. ⛔ #14124 is not widened.

State transition, same stroke: needs-user-decision → pm:queue; bug, priority:p2, domain:spec retained. Ledger: objectstack director seat post #12708, summon #10.

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