the onEmptyApprovers: 'fallback' / fallbackApprovers pairing is statically provable but has no lint arm — it is refused only at node entry, so the typo class stays a run-time discovery #18873

⛔ Recorded for triage; no severity asserted, no domain:*, no type — routing and grading are triage's. Filed by the domain:devx execution PM seat (post #6023, session session_017ef78bLdybu3AffehKkhfk), round 38, as arm (b) of #18551. ⛔ Not claiming.

⚠️ This card exists because #18551's own text forbade dropping it. That card offered two arms and said, verbatim: 「⛔ Do not do (a) and silently drop (b): if (b) is wanted, (a)'s wording has to be re-reverted when it lands. Whoever takes this should say which one they are doing.」 ⇒ The seat took (a) (PR #18868, wording only) and declared (b) would get its own carrier. This is that carrier.

The gap

The pairing between onEmptyApprovers: 'fallback' and a sibling fallbackApprovers list is enforced in both directions — and only at flow execution, when the approval node parses its config on entry. Read on origin/main @ a09d79708 at 2026-09-18T03:11Z:

packages/spec/src/automation/approval.zod.ts:728   function checkFallbackApproversPairing(
packages/spec/src/automation/approval.zod.ts:947   }).superRefine(checkFallbackApproversPairing));
packages/plugins/plugin-approvals/src/approval-node.ts:133
    const parsed = ApprovalNodeConfigSchema.safeParse(node.config ?? {});   ← the only non-test parser

And no author-time arm exists: packages/lint/src/validate-approval-approvers.ts declares 10 rule ids and none of them is the pairing —

approval-approver-cross-org-unsupported · approval-approver-not-membership-tier
approval-approver-type-deprecated · approval-approver-type-unknown
approval-approver-type-unsupported · approval-approvers-may-resolve-empty
approval-decision-outputs-reserved · approval-escalation-reassign-no-target
approval-expression-invalid · approval-expression-no-empty-policy

⭐ Why it is worth building rather than leaving

The pairing is statically provable. #18551 measured the reason in one line: both keys sit in the same object. ⇒ Nothing about this needs run-time knowledge — unlike its neighbour at approvals.mdx:27, where whether a write carries a user is genuinely only knowable at run time, and the page says so correctly.

⇒ Building it moves a whole typo class from run time to author time. Today the author learns at the moment a real flow reaches a real approval node; with the arm, os lint says it before anything runs.

⚠️ The current behaviour is not a hole — triage graded #18551 p3 on exactly that: 「契约是被兑现的,只是时刻不同 …… 拒绝是响亮的、点名两个键、且在任何审批请求打开之前」. ⇒ This card is an improvement, ⛔ not a defect report, and it should be graded as one.

⛔ Why the seat did not just dispatch it

It sits on the manual floor: SKILL.md's floor list names 「新增必需门禁/hook/棘轮」. A new author-time rule that fails a run is a new gate, and the floor is a maintainer's to set — ⛔ not a dispatching seat's, and ⛔ not reachable by folding it into a p3 prose fix. Folding it in would also have let the easy half carry the hard half, which is the shape #18551's own text was written to prevent.

What it needs decided before anyone builds it — ⛔ the seat does not pre-empt these

1. Rule id. The 10 above establish the approval-* naming; a pairing arm needs one that does not read as a duplicate of approval-expression-no-empty-policy.
2. Severity. ⚠️ This is the load-bearing one: error makes the sentence docs(automation): say when the fallbackApprovers pairing is actually enforced #18868 just corrected true as written again (and that wording would then need reverting — [finding] approvals.mdx:302 says the fallback pairing is "refused at authoring time" — nothing parses the node config before flow execution, so the refusal fires at node entry #18551 said so explicitly); warning leaves the doc correct as it now stands.
3. Scope against approval-approvers-may-resolve-empty. That rule already reasons about empty approver sets. ⚠️ approval-approvers-may-resolve-empty covers position and not manager — the rung whose column no product surface can write is the one the rule stays silent on #16748 (closed) records it covering position and not manager — so its boundary is already known to be uneven, and a new arm must say where it stops rather than overlapping silently.

⚠️ The coupling to #18868, stated so it is not discovered later

PR #18868 reworded approvals.mdx to say the refusal fires at flow execution and that os lint has no pairing arm for this one. ⇒ If this card is built, that sentence becomes false and must be re-reverted in the same PR. #18551 named this consequence up front; it is recorded here so the coupling travels with the work rather than with anyone's memory.

⛔ What is NOT claimed

• ⛔ Not that the runtime refusal is inadequate. It is loud, names both keys, and lands before any approval request opens.
• ⛔ Not that severity should be error — that is item 2 above, undecided.
• ⛔ Not measured: how many authored flows in this repo or in examples/** would actually trip such a rule today. ⚠️ A zero there would be a real argument against building it, and nobody has looked.

Duplicate check — method stated

One targeted MCP search_issues call over this repository (repo-scoped REST /search/* answers 403 for this seat, so the channel is declared).

• No card asks for a pairing lint arm.
• Live positive control, same call: spec: approval onEmptyApprovers gains 'fallback' with a sibling fallbackApprovers at the node level — the empty { type: 'manager' } rung becomes survivable (from #16678 Phase 2 §8.2, ruled) #17931 (the card that introduced fallbackApprovers) and approval-approvers-may-resolve-empty covers position and not manager — the rung whose column no product surface can write is the one the rule stays silent on #16748 (the approval-approvers-may-resolve-empty coverage card) both had to hit, and both did ⇒ the zero is a reading, not a dead index.

Dedupe words: fallbackApprovers pairing lint arm · checkFallbackApproversPairing · onEmptyApprovers fallback author-time · approval-approvers-may-resolve-empty scope · approvals.mdx refusal timing

Refs

#18551 · PR #18868 · #17931 · #16748 · approval.zod.ts:728 / :947 · approval-node.ts:133

Generated by Claude Code