@@ -0,0 +1,41 @@
+---
+'@objectstack/spec': minor
+---
+
+A flow `approval` node's `config` is judged at parse against the contract the spec declares for it, `ApprovalNodeConfigSchema`, whole: an undeclared key, a refused value and a required key left out are each refused with a location, in the contract's own words.
+
+Clause-②: yes (narrowing)
+
+<!-- adr-0087: registered flow-approval-node-config-contract-refused -->
+
+**BREAKING**: an accept-set narrowing on a published authoring surface, shipped as `minor` under the launch-window convention for accept-set narrowings.
+
+**Why.** The approval node's executor parses `node.config` against `ApprovalNodeConfigSchema` before it does anything else and fails the node on any issue. Registration already refused an undeclared key, but a refused value such as `escalation.timeoutHours: 0.5` registered and then failed every run that reached the node, and no build door asked about either: `objectstack validate` and `objectstack compile` exited 0 on an `escalation.bogusKey` or a `timeoutHours: 0.5`, and compile copied it into `dist/objectstack.json`.
+
+**What is refused.** An `approval` node, at any depth, whose `config` the approval contract refuses. The judge is `flowNodeConfigRefusals`, the one `FlowSchema.parse`, `AutomationEngine.registerFlow` (which parses first) and `objectstack validate` share; the approval contract joins it as a declared contract map beside the builtin executor contracts, with no plugin loaded. Every issue that contract raises is refused, because the executor refuses on every one:
+
+- an undeclared key, at the key (`nodes.N.config.escalation.bogusKey`, one issue per key, the top level included), and a refused value, at its key (`nodes.N.config.escalation.timeoutHours` for `0.5` under its minimum of 1): the new closed-set code `node-config-refused-by-contract`, `params: { nodeType, key }`, whose message carries the contract's own sentence — for an alias, its did-you-mean (`timeout` → `timeoutHours`);
+- a required key left out (`approvers`; `timeoutHours` inside an `escalation` block): `node-config-key-missing`, as for a builtin node, or `node-config-key-required-by-rule` where a rule of the contract requires it.
+
+The issue's `code` is `custom`. That covers `FlowSchema`, `defineFlow()`, `defineStack` (`STACK_SCHEMA_INVALID`, 422, at `flows.N.nodes.M.config.<key>`), `os validate`, `os compile`, an artifact's parse, `registerFlow` and the metadata save door (`422 INVALID_METADATA`).
+
+**What stays accepted, byte for byte.** Every approval node the contract accepts, an `approval_revise` node, and every builtin node: the builtin arm still judges only a key left out, so an undeclared key or a wrong-typed value on a builtin node is judged where it was before. A plugin node type whose contract the spec does not declare stays outside the build doors.
+
+## FROM → TO
+
+| you wrote | write instead |
+|:--|:--|
+| `escalation: { …, bogusKey: 1 }`, or any key the contract does not declare | delete the key, or rename it to the one the refusal's did-you-mean names (`timeout` → `timeoutHours`, `mode` → `behavior`, `quorum` → `minApprovals`) |
+| `escalation: { timeoutHours: 0.5 }` | `escalation: { timeoutHours: 1 }` — whole wall-clock hours, at least 1 |
+| `escalation: { enabled: false }` with no `timeoutHours` | delete the `escalation` block |
+| `steps`, `entryCriteria`, `onApprove`, `onReject` or `rejectionBehavior` on the node | the flow graph, as the refusal's guidance says (successive nodes, the entering edge's `condition`, the `approve` / `reject` out-edges, a back-edge) |
+| an approval node with no `approvers` | `approvers: [{ type: 'position', value: '<position>' }]` (or any approver the contract accepts) |
+
+**The one-line fix: write the shape the approval contract declares at the key the refusal names.** The runtime never ran such a node, so the fix changes nothing a working flow does.
+
+**Who is affected, measured.** At `5e0b489bca`, every approval node `config` authored in this repository parses under the contract: `examples/**` (15 nodes, all in the showcase), `content/docs/**` (6 snippets), `skills/**` (5 snippets) and the `packages/qa/dogfood` fixtures (6 nodes), and so does the Studio designer's approval seed at the pinned objectui commit. Deployed metadata, and repositories other than these two, were not measured. Where such a node already sits in a stored flow, the whole flow is refused at registration: at boot it is skipped with a warn naming it, its trigger not armed, while the flows beside it register.
+
+### The kit
+
+- **The refusal.** The declared contract map in `automation/flow-node-config-refusals.ts`, read by the same executor-contract arm of `flowNodeConfigRefusals`; the new code joins `FLOW_SLOT_REFUSAL_CODES`.
+- **The ledger.** The D3 semantic entry `flow-approval-node-config-contract-refused` (protocol 18). No key is removed, so there is no tombstone, and there is no D2 conversion: the platform cannot know the approvers, the key or the value the author meant.
@@ -45,7 +45,6 @@ const cleanApprovalFlow = {
       type: 'approval',
       config: {
         approvers: [{ type: 'expression', value: 'current.owner' }],
-        emptyApproverPolicy: 'reject',
       },
     },
   ],
 
@@ -70,7 +70,6 @@ const validApprovalFlow = () => {
     const flow = brokenApprovalFlow();
     flow.nodes[1]!.config = {
         approvers: [{ type: 'expression', value: 'current.owner' }],
-        emptyApproverPolicy: 'reject',
     } as any;
     return flow;
 };
 
@@ -274,7 +274,6 @@ describe('#6710 — the authoring channel is threaded from plugin option to prot
     const flow = brokenApprovalFlow();
     (flow.nodes[1] as any).config = {
       approvers: [{ type: 'expression', value: 'current.owner' }],
-      emptyApproverPolicy: 'reject',
     };
     const result = await (kernel.getService('protocol') as any).saveMetaItem({
       type: 'flow', name: 'leave_approval', item: flow,
 
@@ -2626,7 +2626,7 @@ describe('Action Descriptor Registry (ADR-0018)', () => {
         type: 'autolaunched' as const,
         nodes: [
             { id: 'start', type: 'start', label: 'Start' },
-            { id: 'custom', type, label: 'Custom' },
+            { id: 'custom', type, label: 'Custom', ...(type === 'approval' ? { config: { approvers: [{ type: 'user', value: 'u1' }] } } : {}) },
             { id: 'end', type: 'end', label: 'End' },
         ],
         edges: [
 
@@ -0,0 +1,265 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#21850] The build doors judge an `approval` node's `config` against the
+ * contract the spec declares for it, `ApprovalNodeConfigSchema`, WHOLE — the
+ * declared contract map in `flow-node-config-refusals.ts`, beside the builtin
+ * executor contracts and read by the same judge, `flowNodeConfigRefusals`.
+ *
+ * The approval executor (`plugin-approvals`) parses `node.config ?? {}`
+ * against that contract before it does anything else and fails the node on
+ * ANY issue, so every contract finding is one the run would refuse: a key the
+ * contract requires left out, a key it does not declare, a value it refuses.
+ * `FlowSchema` used to accept all three, so `objectstack validate` and
+ * `objectstack compile` exited 0 on them and compile copied the shape into the
+ * artifact; the author learned otherwise at the first run.
+ *
+ * Every door that parses a flow meets the judge: `FlowSchema` itself,
+ * `defineStack`, the stack parse `objectstack validate` and `compile` run, the
+ * registered `flow` type schema the metadata save door validates against, and
+ * an artifact's parse — pinned here. `registerFlow` parses first, and
+ * `validateStackExpressions` calls the same judge.
+ *
+ * No plugin is loaded for any of it: the contract is the spec's own. The
+ * builtin arm is unchanged, presence-only — a control below holds it there.
+ */
+
+import { describe, expect, it } from 'vitest';
+
+import { getMetadataTypeSchema } from '../kernel/metadata-type-schemas';
+import { MIGRATIONS_BY_MAJOR, RETIRED_KEYS_BY_MAJOR } from '../migrations/registry';
+import { ArtifactStagePackageBodySchema, ObjectStackDefinitionSchema, defineStack } from '../stack.zod';
+import { ApprovalEscalationSchema, ApprovalNodeConfigSchema } from './approval.zod';
+import { flowNodeConfigRefusals, getBuiltinNodeConfigContracts } from './flow-node-config-refusals';
+import { FlowSchema } from './flow.zod';
+
+const ENTRY_ID = 'flow-approval-node-config-contract-refused';
+
+type Config = Record<string, unknown>;
+
+const APPROVERS = [{ type: 'position', value: 'finance_reviewer' }];
+
+/** A whole approval config the contract accepts — the accept control, and the base every probe edits. */
+const VALID: Config = {
+  approvers: APPROVERS,
+  behavior: 'first_response',
+  lockRecord: true,
+  escalation: { enabled: true, timeoutHours: 4, action: 'notify', notifySubmitter: true },
+};
+
+const withEscalation = (escalation: Config): Config => ({ ...VALID, escalation });
+
+/** start → the approval node → approve / reject ends. */
+function flowWith(config: unknown, name = 'approval_probe') {
+  return {
+    name,
+    label: 'Approval probe',
+    type: 'autolaunched',
+    nodes: [
+      { id: 'start', type: 'start', label: 'Start' },
+      { id: 'gate', type: 'approval', label: 'Gate', ...(config === undefined ? {} : { config }) },
+      { id: 'approved', type: 'end', label: 'Approved' },
+      { id: 'rejected', type: 'end', label: 'Rejected' },
+    ],
+    edges: [
+      { id: 'e1', source: 'start', target: 'gate' },
+      { id: 'e2', source: 'gate', target: 'approved', label: 'approve' },
+      { id: 'e3', source: 'gate', target: 'rejected', label: 'reject' },
+    ],
+  };
+}
+
+interface IssueSig { code: string; path: string; message: string }
+
+function issuesOf(flow: unknown): IssueSig[] {
+  const r = FlowSchema.safeParse(flow);
+  return r.success ? [] : r.error.issues.map((i) => ({ code: i.code, path: i.path.join('.'), message: i.message }));
+}
+
+/** The approval contract's own sentence at one issue path — read, never re-spelled. */
+function contractSentence(schema: { safeParse(v: unknown): { success: boolean; error?: { issues: Array<{ path: PropertyKey[]; message: string }> } } }, value: unknown, path: string): string {
+  const own = schema.safeParse(value);
+  return own.success ? '' : own.error?.issues.find((i) => i.path.join('.') === path)?.message ?? '';
+}
+
+describe('FlowSchema judges an approval node config against its declared contract, whole', () => {
+  it('an undeclared escalation key is refused at nodes.1.config.escalation.bogusKey', () => {
+    const config = withEscalation({ timeoutHours: 2, action: 'notify', bogusKey: 1 });
+    const issues = issuesOf(flowWith(config));
+    expect(issues.map(({ code, path }) => ({ code, path }))).toEqual([
+      { code: 'custom', path: 'nodes.1.config.escalation.bogusKey' },
+    ]);
+    // The judge's own words, never re-spelled, carrying the contract's own sentence.
+    expect(issues[0]!.message).toBe(flowNodeConfigRefusals('approval', config)[0]!.message);
+    expect(issues[0]!.message).toContain(contractSentence(ApprovalEscalationSchema, config.escalation, ''));
+  });
+
+  it('a timeoutHours under the contract minimum is refused at nodes.1.config.escalation.timeoutHours', () => {
+    const issues = issuesOf(flowWith(withEscalation({ timeoutHours: 0.5, action: 'notify' })));
+    expect(issues.map(({ code, path }) => ({ code, path }))).toEqual([
+      { code: 'custom', path: 'nodes.1.config.escalation.timeoutHours' },
+    ]);
+  });
+
+  it('the judge answers both with its code, params and path', () => {
+    const bogus = flowNodeConfigRefusals('approval', withEscalation({ timeoutHours: 2, bogusKey: 1 }));
+    const halfHour = flowNodeConfigRefusals('approval', withEscalation({ timeoutHours: 0.5 }));
+    expect([...bogus, ...halfHour].map(({ code, params, path, source }) => ({ code, params, path, source }))).toEqual([
+      { code: 'node-config-refused-by-contract', params: { nodeType: 'approval', key: 'escalation.bogusKey' }, path: 'escalation.bogusKey', source: '' },
+      { code: 'node-config-refused-by-contract', params: { nodeType: 'approval', key: 'escalation.timeoutHours' }, path: 'escalation.timeoutHours', source: '' },
+    ]);
+  });
+
+  it('an alias keeps the contract\'s own did-you-mean, beside the key it leaves out', () => {
+    const config = withEscalation({ timeout: 2 });
+    const issues = issuesOf(flowWith(config));
+    expect(issues.map(({ path }) => path).sort()).toEqual([
+      'nodes.1.config.escalation.timeout',
+      'nodes.1.config.escalation.timeoutHours',
+    ]);
+    const aliasSentence = contractSentence(ApprovalEscalationSchema, config.escalation, '');
+    expect(aliasSentence).toContain('`timeoutHours`');
+    expect(issues.find((i) => i.path.endsWith('.timeout'))!.message).toContain(aliasSentence);
+  });
+
+  it('an undeclared top-level key is refused at the key, one refusal per key', () => {
+    const issues = issuesOf(flowWith({ ...VALID, steps: [], quorum: 2 }));
+    expect(issues.map(({ path }) => path)).toEqual(['nodes.1.config.steps', 'nodes.1.config.quorum']);
+  });
+
+  it('a key the contract requires, left out, is refused with the builtin arm\'s code', () => {
+    for (const config of [undefined, {}]) {
+      expect(issuesOf(flowWith(config)).map(({ path }) => path), JSON.stringify(config)).toEqual(['nodes.1.config.approvers']);
+      expect(flowNodeConfigRefusals('approval', config).map(({ code }) => code)).toEqual(['node-config-key-missing']);
+    }
+  });
+
+  it('a value a rule of the contract refuses is refused in the rule\'s own words', () => {
+    const config = { ...VALID, onEmptyApprovers: 'fail', fallbackApprovers: APPROVERS };
+    const [refusal] = flowNodeConfigRefusals('approval', config);
+    expect(refusal!.path).toBe('onEmptyApprovers');
+    expect(refusal!.message).toContain(contractSentence(ApprovalNodeConfigSchema, config, 'onEmptyApprovers'));
+  });
+
+  it('the judge refuses exactly what the contract refuses, over a sweep of configs', () => {
+    const sweep: unknown[] = [
+      undefined, {}, VALID,
+      { approvers: [] },
+      { approvers: 'u1' },
+      { approvers: [{ type: 'user', value: 'u1' }] },
+      { ...VALID, behavior: 'weighted' },
+      { ...VALID, minApprovals: 0 },
+      { ...VALID, maxRevisions: 1.5 },
+      { ...VALID, decisionOutputs: ['note', { key: 'picked', type: 'user', multiple: true }] },
+      withEscalation({ timeoutHours: 1 }),
+      withEscalation({ enabled: false }),
+      withEscalation({ timeoutHours: 2, action: 'escalate' }),
+      withEscalation({ timeoutHours: '2' }),
+    ];
+    for (const config of sweep) {
+      const refused = flowNodeConfigRefusals('approval', config).length > 0;
+      expect(refused, JSON.stringify(config)).toBe(!ApprovalNodeConfigSchema.safeParse(config ?? {}).success);
+    }
+  });
+});
+
+describe('what stays accepted (lit controls)', () => {
+  it('CONTROL: a valid approval node parses', () => {
+    expect(issuesOf(flowWith(VALID))).toEqual([]);
+    expect(flowNodeConfigRefusals('approval', VALID)).toEqual([]);
+  });
+
+  it('CONTROL: an escalation at the contract minimum, and a node with no escalation block, parse', () => {
+    expect(issuesOf(flowWith(withEscalation({ timeoutHours: 1 })))).toEqual([]);
+    expect(issuesOf(flowWith({ approvers: APPROVERS }))).toEqual([]);
+  });
+
+  it('CONTROL: the builtin arm stays presence-only — an undeclared key on a builtin node still parses', () => {
+    const flow = {
+      ...flowWith(VALID),
+      nodes: [
+        { id: 'start', type: 'start', label: 'Start' },
+        { id: 'call', type: 'http', label: 'Call', config: { url: 'https://example.test', bogusKey: 1 } },
+        { id: 'done', type: 'end', label: 'Done' },
+      ],
+      edges: [{ id: 'e1', source: 'start', target: 'call' }, { id: 'e2', source: 'call', target: 'done' }],
+    };
+    expect(issuesOf(flow)).toEqual([]);
+    // …and the builtin map, the executor-reconciled one, did not gain the plugin type.
+    expect(getBuiltinNodeConfigContracts().has('approval')).toBe(false);
+  });
+
+  it('CONTROL: approval_revise carries no config contract and is not judged', () => {
+    expect(flowNodeConfigRefusals('approval_revise', { anything: 1 })).toEqual([]);
+  });
+});
+
+describe('every door that parses a flow refuses it', () => {
+  const stackWith = (flows: unknown[]) => ({
+    manifest: { id: 'com.example.approvals', name: 'approvals', version: '1.0.0', type: 'app', namespace: 'apv' },
+    objects: [{ name: 'apv_request', label: 'Request', fields: { title: { type: 'text', label: 'Title' } } }],
+    flows,
+  });
+  const refused = flowWith(withEscalation({ timeoutHours: 2, bogusKey: 1 }), 'apv_refused');
+  const accepted = flowWith(VALID, 'apv_ok');
+
+  it('defineStack wraps the refusal in its ADR-0112 envelope, at flows.N.nodes.1.config.escalation.bogusKey', () => {
+    let refusal: { code?: unknown; status?: unknown; issues?: Array<{ path: unknown[]; code: string }> } | undefined;
+    try {
+      defineStack(stackWith([accepted, refused]) as never);
+    } catch (e) {
+      refusal = e as typeof refusal;
+    }
+    expect(refusal, 'defineStack must refuse the approval flow').toBeDefined();
+    expect({ code: refusal!.code, status: refusal!.status }).toEqual({ code: 'STACK_SCHEMA_INVALID', status: 422 });
+    expect(refusal!.issues!.map((i) => ({ path: i.path.join('.'), code: i.code }))).toEqual([
+      { path: 'flows.1.nodes.1.config.escalation.bogusKey', code: 'custom' },
+    ]);
+  });
+
+  it('CONTROL: defineStack accepts the valid approval flow alone', () => {
+    expect(() => defineStack(stackWith([accepted]) as never)).not.toThrow();
+  });
+
+  it('ObjectStackDefinitionSchema — the stack parse validate and compile run — refuses it at the same path', () => {
+    const r = ObjectStackDefinitionSchema.safeParse(stackWith([flowWith(withEscalation({ timeoutHours: 0.5 }), 'apv_half')]));
+    expect(r.success).toBe(false);
+    expect(r.success ? [] : r.error.issues.map((i) => i.path.join('.'))).toEqual(['flows.0.nodes.1.config.escalation.timeoutHours']);
+    expect(ObjectStackDefinitionSchema.safeParse(stackWith([accepted])).success).toBe(true);
+  });
+
+  it('the registered `flow` type schema — what the metadata save door validates against — refuses it too', () => {
+    const schema = getMetadataTypeSchema('flow') as unknown as typeof FlowSchema;
+    expect(schema).toBeDefined();
+    const r = schema.safeParse(refused);
+    expect(r.success).toBe(false);
+    expect(r.success ? [] : r.error.issues.map((i) => i.path.join('.'))).toEqual(['nodes.1.config.escalation.bogusKey']);
+    expect(schema.safeParse(accepted).success).toBe(true);
+  });
+
+  it('an artifact\'s parse refuses it', () => {
+    const body = { id: 'com.example.approvals', name: 'approvals', version: '1.0.0', type: 'app' };
+    const r = ArtifactStagePackageBodySchema.safeParse({ ...body, flows: [refused] });
+    expect(r.success).toBe(false);
+    expect(r.success ? [] : r.error.issues.map((i) => i.path.join('.'))).toEqual(['flows.0.nodes.1.config.escalation.bogusKey']);
+    const ok = ArtifactStagePackageBodySchema.safeParse({ ...body, flows: [accepted] });
+    expect(ok.success, JSON.stringify(ok.error?.issues ?? [])).toBe(true);
+  });
+});
+
+describe('the ADR-0087 ledger', () => {
+  it('registers one D3 entry at protocol 18, with no D2 conversion', () => {
+    const entries = MIGRATIONS_BY_MAJOR[18]!.semantic.filter((e) => e.id === ENTRY_ID);
+    expect(entries, 'the narrowing needs its own D3 entry').toHaveLength(1);
+    const [entry] = entries;
+    expect(entry!.conversionIds ?? []).toEqual([]);
+    expect(entry!.acceptanceCriteria.length).toBeGreaterThan(0);
+  });
+
+  it('registers no tombstone: no approval config key is removed', () => {
+    const all = Object.values(RETIRED_KEYS_BY_MAJOR).flat();
+    expect(all.filter((k) => /Approval(NodeConfig|Escalation)[^:]*:/.test(k))).toEqual([]);
+    // CONTROL: the flattened table is the real one — it carries a known step-18 tombstone.
+    expect(all).toContain('api/RestApiEndpoint:timeout');
+  });
+});