diff --git a/api-surface.json b/api-surface.json
index 01741c80..48667ac0 100644
--- a/api-surface.json
+++ b/api-surface.json
@@ -1585,7 +1585,7 @@
       "runBenchmark": "value a00b82e95062",
       "runCancelRequestFile": "value 229aecaab891",
       "runCancellationFile": "value 229aecaab891",
-      "runFinalizer": "value 34d3218fb8ef",
+      "runFinalizer": "value fc5202156e7a",
       "runGraph": "value 7d72ff33c325",
       "runInWorkspace": "value 624b01e4ba38",
       "runIsolatedCheck": "value ebb5d56a353b",
diff --git a/docs/api/runtime.md b/docs/api/runtime.md
index cbfc58b9..d9731cce 100644
--- a/docs/api/runtime.md
+++ b/docs/api/runtime.md
@@ -34436,7 +34436,11 @@ readonly `T`[]
 Run a finalizer over a settled-worker ledger under the delivered-only invariant: filter the
 ledger to structurally delivered children, materialize their outputs, and hand the finalizer a
 blob reader that throws on any ref outside that set. This is the one call site both driver arms
-(the in-process tool-loop and the MCP-mounted harness) finalize through.
+(the in-process tool-loop and the MCP-mounted harness) finalize through. When a parent declares
+a deliverable, its candidate must also pass that check: children may have narrower assignments.
+The default selects the highest-scoring child that passes the parent's check; custom finalizers
+assemble their candidate before the check. A rejection leaves the parent incomplete; a thrown
+oracle surfaces a validation error. Neither changes child validity.
 
 #### Parameters
 
@@ -34462,6 +34466,10 @@ readonly [`FinalizerSettled`](#finalizersettled)[]
 
 `Readonly`\<\{ `resources?`: `Readonly`\<`Record`\<`string`, \{ `unit`: `string`; `limit`: `number`; `remaining`: `number`; `reserved`: `number`; `committed`: `number`; `known`: `boolean`; \}\>\>; `tokensLeft`: `number`; `tokensKnown`: `boolean`; `cacheBreakdownKnown`: `boolean`; `usdLeft`: `number`; `usdCapped`: `boolean`; `usdKnown`: `boolean`; `iterationsLeft`: `number`; `deadlineMs`: `number`; `reservedTokens`: `number`; \}\>
 
+###### deliverable?
+
+[`DeliverableSpec`](#deliverablespec)\<`unknown`\>
+
 #### Returns
 
 `Promise`\<`unknown`\>
diff --git a/docs/canonical-api.md b/docs/canonical-api.md
index 3fc009a2..ef98b093 100644
--- a/docs/canonical-api.md
+++ b/docs/canonical-api.md
@@ -127,6 +127,14 @@ A general "loop" primitive is the single most common modelling error in this rep
 
 **The trap** is a single grammar (`defineLoop`, a `runXxxLoop`) spanning all of the above: there can't be one, because some are code and one is a model deciding. No new loop primitive lands without a tiny executable proof, **over real agents**, of the exact substrate join it claims to simplify.
 
+A child can satisfy its own assignment while its parent's objective remains incomplete.
+When the parent declares a `deliverable`, its finalizer's candidate must pass that check before the parent completes.
+The default selects the highest-scoring child that also passes the parent's check.
+Custom finalizers assemble their candidate before the check.
+Child validity and delivery counts remain unchanged.
+An external director can then use `repromptOnUnmet` to continue from a rejected candidate within its existing resource limits.
+A thrown parent check reports a validation error through the existing driver failure record.
+
 | I want to… | Use (import) | Do NOT build |
 |---|---|---|
 | Run one product chat turn with streamed events, ordered persistence hooks, and stable execution/turn identity | `handleChatTurn(...)` + `deriveExecutionId(...)`: `/durable`; pass the derived id as both `executionId` and `turnId` on initial dispatch | importing the broad package entry from an edge worker, treating `executionId` alone as dispatch idempotency, or rebuilding framing and persistence ordering in the product |
diff --git a/src/runtime/supervise/coordination-driver.ts b/src/runtime/supervise/coordination-driver.ts
index 1d20cd06..605fdecc 100644
--- a/src/runtime/supervise/coordination-driver.ts
+++ b/src/runtime/supervise/coordination-driver.ts
@@ -1289,6 +1289,7 @@ export function driverAgent(opts: DriverAgentOptions): Agent<unknown, unknown> {
         blobs: opts.blobs,
         tree: runTree(scope),
         budget: scope.budget,
+        ...(opts.deliverable ? { deliverable: opts.deliverable } : {}),
       })
     },
   }
diff --git a/src/runtime/supervise/finalizer.ts b/src/runtime/supervise/finalizer.ts
index 4fc072b1..4040ea5e 100644
--- a/src/runtime/supervise/finalizer.ts
+++ b/src/runtime/supervise/finalizer.ts
@@ -19,6 +19,7 @@
  */
 
 import { ValidationError } from '../../errors'
+import type { DeliverableSpec } from './completion-gate'
 import type { ResultBlobStore, Scope, TreeView } from './types'
 
 /** One settled worker as the finalizer sees it — the ledger row (structural fields only). */
@@ -114,7 +115,11 @@ export const collectDelivered: SupervisorFinalizer = (ctx) => {
  * Run a finalizer over a settled-worker ledger under the delivered-only invariant: filter the
  * ledger to structurally delivered children, materialize their outputs, and hand the finalizer a
  * blob reader that throws on any ref outside that set. This is the one call site both driver arms
- * (the in-process tool-loop and the MCP-mounted harness) finalize through.
+ * (the in-process tool-loop and the MCP-mounted harness) finalize through. When a parent declares
+ * a deliverable, its candidate must also pass that check: children may have narrower assignments.
+ * The default selects the highest-scoring child that passes the parent's check; custom finalizers
+ * assemble their candidate before the check. A rejection leaves the parent incomplete; a thrown
+ * oracle surfaces a validation error. Neither changes child validity.
  */
 export async function runFinalizer(
   finalizer: SupervisorFinalizer,
@@ -123,6 +128,7 @@ export async function runFinalizer(
     readonly blobs: ResultBlobStore
     readonly tree: TreeView
     readonly budget: Scope<unknown>['budget']
+    readonly deliverable?: DeliverableSpec
   },
 ): Promise<unknown | undefined> {
   const deliveredRows = args.settled.filter((w) => w.status === 'done' && w.valid === true)
@@ -146,11 +152,31 @@ export async function runFinalizer(
       return args.blobs.get(outRef)
     },
   }
-  return finalizer({
+  const accepted = async (candidate: unknown): Promise<boolean> => {
+    if (candidate === undefined) return false
+    if (args.deliverable === undefined) return true
+    try {
+      return (await args.deliverable.check(candidate)) === true
+    } catch (error) {
+      throw new ValidationError(
+        `finalizer: parent completion check threw: ${error instanceof Error ? error.message : String(error)}`,
+      )
+    }
+  }
+  // A high-scoring partial assignment cannot displace a complete portfolio member. Aggregating
+  // finalizers still need every child-valid component, so their inputs must not be filtered here.
+  if (finalizer === bestDelivered && args.deliverable !== undefined) {
+    for (const output of [...delivered].sort((a, b) => (b.score ?? 0) - (a.score ?? 0))) {
+      if (await accepted(output.out)) return output.out
+    }
+    return undefined
+  }
+  const candidate = await finalizer({
     delivered,
     allSettled: args.settled,
     tree: args.tree,
     blobs: guardedBlobs,
     budget: args.budget,
   })
+  return (await accepted(candidate)) ? candidate : undefined
 }
diff --git a/src/runtime/supervise/supervisor-agent.ts b/src/runtime/supervise/supervisor-agent.ts
index 31387316..5b234bd7 100644
--- a/src/runtime/supervise/supervisor-agent.ts
+++ b/src/runtime/supervise/supervisor-agent.ts
@@ -982,9 +982,18 @@ function buildSupervisorAgent(
         const baseTokensLeft = scope.budget.tokensLeft
         const contractDeclared = deps.deliverable !== undefined
         const maxReprompts = deps.repromptOnUnmet ?? 0
+        let candidate: unknown
+        const finalize = () =>
+          runFinalizer(deps.finalizer ?? bestDelivered, {
+            settled: mcp.settled(),
+            blobs: deps.blobs,
+            tree: runTree(scope),
+            budget: scope.budget,
+            ...(deps.deliverable ? { deliverable: deps.deliverable } : {}),
+          })
         const readProgress = (): DriverProgressMark => {
           const settled = mcp.settled()
-          // The same delivered-only rule the finalizer applies: settled `done` AND check-passed.
+          // Child delivery is progress, but its check may cover only the child's assignment.
           const deliveredCount = settled.filter(
             (w) => w.status === 'done' && w.valid === true,
           ).length
@@ -996,13 +1005,14 @@ function buildSupervisorAgent(
             deliveredCount,
             contract: !contractDeclared
               ? 'none'
-              : submitted || deliveredCount > 0
+              : submitted || candidate !== undefined
                 ? 'met'
                 : 'unmet',
           }
         }
         await runDriverWithRetry({
           drive: async (attempt, reentry) => {
+            candidate = undefined
             if (deps.controlDir !== undefined && deps.abortRun !== undefined) {
               applyRunCancellation(deps.controlDir, deps.abortRun, () => new Date().toISOString())
             }
@@ -1029,6 +1039,12 @@ function buildSupervisorAgent(
               // an accepted submission the backend error propagates into the retry decision.
               if (!mcp.submittedResult() && !mcp.isStopped()) throw error
             }
+            // Decide this parent's completion before the retry loop reads progress. Cache the
+            // checked candidate so neither the finalizer nor its oracle runs twice on return.
+            if (contractDeclared && !mcp.submittedResult()) {
+              await mcp.drainResolved()
+              candidate = await finalize()
+            }
           },
           progress: readProgress,
           budget: () => scope.budget,
@@ -1059,9 +1075,8 @@ function buildSupervisorAgent(
             : {}),
           ...(deps.onDriverAttempt ? { onAttempt: deps.onDriverAttempt } : {}),
         })
-        // Drain settled-but-unpulled children first — a gate-verified delivery the harness never
-        // awaited must still reach the finalize ledger.
-        await mcp.drainResolved()
+        // Without a parent oracle, preserve the single finalization after the driver finishes.
+        if (!contractDeclared) await mcp.drainResolved()
         // Direct work is eligible only through `submit_result`, after the injected independent
         // check passes. Raw harness prose remains ineligible.
         const submitted = mcp.submittedResult()
@@ -1071,12 +1086,7 @@ function buildSupervisorAgent(
         }
         // The deliverable comes from the finalizer seam over DELIVERED children only — never the
         // harness's own output (Foreman 0/18). Default keep-best.
-        return await runFinalizer(deps.finalizer ?? bestDelivered, {
-          settled: mcp.settled(),
-          blobs: deps.blobs,
-          tree: runTree(scope),
-          budget: scope.budget,
-        })
+        return contractDeclared ? candidate : await finalize()
       } finally {
         await mcp.close()
       }
diff --git a/tests/kernel/supervise-convenience.test.ts b/tests/kernel/supervise-convenience.test.ts
index ad65dd36..d3b41c8a 100644
--- a/tests/kernel/supervise-convenience.test.ts
+++ b/tests/kernel/supervise-convenience.test.ts
@@ -251,6 +251,7 @@ describe('supervise — the one-call convenience (defaults blobs/perWorker/journ
 
   it('uses a child-specific completion check when a managed child submits its own result', async () => {
     let childCheckCalls = 0
+    const journal = new InMemorySpawnJournal()
     const child = testAgentProfile('specialist', {
       harness: 'opencode',
       tools: runtimeToolDeclarations('submit_result'),
@@ -288,6 +289,8 @@ describe('supervise — the one-call convenience (defaults blobs/perWorker/journ
         perWorker: { maxIterations: 4, maxTokens: 10_000 },
         makeLeafAgent: () => deliveringLeaf('unused', {}),
         driveHarness,
+        journal,
+        runId: 'parent-contract',
         // The run-wide check deliberately rejects the child's output. A profile-managed child
         // must instead receive the check selected for its exact authorized assignment.
         deliverable: { check: () => false },
@@ -307,9 +310,22 @@ describe('supervise — the one-call convenience (defaults blobs/perWorker/journ
       },
     )
 
-    expect(result.kind).toBe('winner')
-    if (result.kind === 'winner') expect(result.out).toEqual({ answer: 42 })
+    // The child's own check is what judged the child: consulted exactly once, and it passed.
     expect(childCheckCalls).toBe(1)
+    expect(await journal.loadTree('parent-contract')).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          kind: 'settled',
+          id: 'parent-contract:s0',
+          status: 'done',
+          verdict: expect.objectContaining({ valid: true }),
+        }),
+      ]),
+    )
+    // A child that satisfies its narrower assignment does not complete the parent. The run-wide
+    // check rejects the child's output, no continuation is configured, so the parent's contract
+    // stays unmet and the partial component is not promoted to the winner.
+    expect(result.kind).toBe('no-winner')
   })
 
   it('runDir makes the run durable and resumable; unset stays in-memory', async () => {
diff --git a/tests/kernel/supervisor-agent.test.ts b/tests/kernel/supervisor-agent.test.ts
index 4447e587..2b512a77 100644
--- a/tests/kernel/supervisor-agent.test.ts
+++ b/tests/kernel/supervisor-agent.test.ts
@@ -1515,6 +1515,161 @@ describe('supervisorAgent — coordination bind + prompt hoisting on the harness
     expect(tasks).toHaveLength(1)
   })
 
+  it('EXTERNAL arm: a valid partial child leaves the parent contract unmet and re-enters its director', async () => {
+    const blobs = new InMemoryResultBlobStore()
+    const journal = new InMemorySpawnJournal()
+    const checked: unknown[] = []
+    const progress: unknown[] = []
+    let drives = 0
+    let finalizations = 0
+    const partial = { component: 'database', ready: true }
+    const complete = { answer: 42 }
+    const root = supervisorAgent(
+      testAgentProfile('sup', {
+        harness: 'pi',
+        tools: runtimeToolDeclarations('spawn_worker', 'await_event', 'submit_result'),
+      }),
+      {
+        blobs,
+        makeWorkerAgent: () => deliveringLeaf('component', partial),
+        perWorker,
+        driveHarness: async ({ coordinationMcpUrl }) => {
+          drives += 1
+          if (drives === 1) {
+            await jsonRpc(coordinationMcpUrl, 'tools/call', {
+              name: 'spawn_worker',
+              arguments: { profile: testAgentProfile('component'), task: 'build the database' },
+            })
+            await jsonRpc(coordinationMcpUrl, 'tools/call', {
+              name: 'await_event',
+              arguments: {},
+            })
+            return
+          }
+          await jsonRpc(coordinationMcpUrl, 'tools/call', {
+            name: 'submit_result',
+            arguments: { result: complete },
+          })
+        },
+        finalizer: ({ delivered }) => {
+          finalizations += 1
+          expect(delivered).toHaveLength(1)
+          return delivered[0]?.out
+        },
+        deliverable: {
+          check: (out) => {
+            checked.push(out)
+            return JSON.stringify(out) === JSON.stringify(complete)
+          },
+        },
+        repromptOnUnmet: 1,
+        onUnmetContract: (context) => {
+          progress.push(context.progress)
+          return { steer: 'Integrate the database into the complete product.' }
+        },
+      },
+    )
+
+    const result = await runSupervisor(root, blobs, journal)
+    expect(result.kind).toBe('winner')
+    if (result.kind === 'winner') expect(result.out).toEqual(complete)
+    expect(drives).toBe(2)
+    expect(finalizations).toBe(1)
+    expect(checked).toEqual([partial, complete])
+    expect(progress).toEqual([expect.objectContaining({ deliveredCount: 1, contract: 'unmet' })])
+    expect(await journal.loadTree('sup')).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          kind: 'settled',
+          id: 'sup:s0',
+          status: 'done',
+          verdict: expect.objectContaining({ valid: true }),
+        }),
+      ]),
+    )
+  })
+
+  it.each([
+    { name: 'partial', out: { component: 'database' }, valid: false },
+    { name: 'complete', out: { answer: 42 }, valid: true },
+    { name: 'throwing check', out: { throw: true }, valid: false },
+    { name: 'aggregate', out: { component: 'database' }, aggregate: true, valid: true },
+  ])('both arms check the parent contract for a $name child candidate', async (scenario) => {
+    for (const harness of ['pi', 'cli-base'] as const) {
+      const blobs = new InMemoryResultBlobStore()
+      const journal = new InMemorySpawnJournal()
+      let checks = 0
+      let finalizations = 0
+      const root = supervisorAgent(
+        testAgentProfile('sup', {
+          harness,
+          tools: runtimeToolDeclarations('spawn_worker', 'await_event'),
+        }),
+        {
+          blobs,
+          makeWorkerAgent: () => deliveringLeaf('component', scenario.out),
+          perWorker,
+          ...(harness === 'pi'
+            ? {
+                driveHarness: async ({ coordinationMcpUrl }: Parameters<DriveHarness>[0]) => {
+                  await jsonRpc(coordinationMcpUrl, 'tools/call', {
+                    name: 'spawn_worker',
+                    arguments: { profile: testAgentProfile('component'), task: 'build component' },
+                  })
+                  await jsonRpc(coordinationMcpUrl, 'tools/call', {
+                    name: 'await_event',
+                    arguments: {},
+                  })
+                },
+              }
+            : {
+                brain: scriptedBrain([
+                  {
+                    toolCalls: [
+                      {
+                        name: 'spawn_worker',
+                        arguments: {
+                          profile: testAgentProfile('component'),
+                          task: 'build component',
+                        },
+                      },
+                    ],
+                  },
+                  { toolCalls: [{ name: 'await_event', arguments: {} }] },
+                  { content: 'done' },
+                ]),
+              }),
+          finalizer: ({ delivered }) => {
+            finalizations += 1
+            return scenario.aggregate ? { answer: 42 } : delivered[0]?.out
+          },
+          deliverable: {
+            check: (out) => {
+              checks += 1
+              if (scenario.name === 'throwing check') throw new Error('oracle unavailable')
+              return JSON.stringify(out) === JSON.stringify({ answer: 42 })
+            },
+          },
+        },
+      )
+
+      const result = await runSupervisor(root, blobs, journal)
+      expect(result.kind, `${harness}: ${scenario.name}`).toBe(
+        scenario.valid ? 'winner' : 'no-winner',
+      )
+      if (scenario.name === 'throwing check' && result.kind === 'no-winner') {
+        expect(result.reason).toBe('driver-failed')
+        if (result.reason === 'driver-failed') {
+          expect(result.error.message).toContain(
+            'parent completion check threw: oracle unavailable',
+          )
+        }
+      }
+      expect(checks).toBe(1)
+      expect(finalizations).toBe(1)
+    }
+  })
+
   it('EXTERNAL arm: a run the coordination server STOPPED is never re-prompted', async () => {
     // The driver called `stop`. That was a decision, and Runtime refuses the re-prompt before the
     // product hook is consulted, so no hook can talk the run past its own stop.
diff --git a/tests/runtime/supervisor-finalizer.test.ts b/tests/runtime/supervisor-finalizer.test.ts
index 98f4ce26..a605c668 100644
--- a/tests/runtime/supervisor-finalizer.test.ts
+++ b/tests/runtime/supervisor-finalizer.test.ts
@@ -138,6 +138,42 @@ describe('SupervisorFinalizer — bestDelivered is the unchanged default', () =>
     expect(await runWith(bestDelivered, fx)).toBeUndefined()
     expect(await runWith(collectDelivered, fx)).toBeUndefined()
   })
+
+  it.each([true, false])(
+    'checks the parent objective in score order with a complete sibling present: %s',
+    async (completeSibling) => {
+      const fx = await ledgerFixture([
+        { id: 'component', status: 'done', valid: true, score: 0.9, payload: 'database ready' },
+        {
+          id: 'product',
+          status: 'done',
+          valid: true,
+          score: 0.5,
+          payload: completeSibling ? 'product verified' : 'api ready',
+        },
+        { id: 'invalid', status: 'done', valid: false, score: 1, payload: 'product verified' },
+      ])
+      const checked: unknown[] = []
+      const result = await runFinalizer(bestDelivered, {
+        settled: fx.rows,
+        blobs: fx.blobs,
+        tree: emptyTree,
+        budget: poolReadout,
+        deliverable: {
+          check: (candidate) => {
+            checked.push(candidate)
+            return candidate === 'product verified'
+          },
+        },
+      })
+      expect(result).toBe(completeSibling ? 'product verified' : undefined)
+      expect(checked).toEqual([
+        'database ready',
+        completeSibling ? 'product verified' : 'api ready',
+      ])
+      expect(fx.rows.map((row) => row.valid)).toEqual([true, true, false])
+    },
+  )
 })
 
 describe('SupervisorFinalizer — collectDelivered is the second implementation', () => {