diff --git a/src/api/capacity/services/capacity/assignments/lifecycle/assignment-lifecycle-service.ts b/src/api/capacity/services/capacity/assignments/lifecycle/assignment-lifecycle-service.ts
index 3ad51863..36407770 100644
--- a/src/api/capacity/services/capacity/assignments/lifecycle/assignment-lifecycle-service.ts
+++ b/src/api/capacity/services/capacity/assignments/lifecycle/assignment-lifecycle-service.ts
@@ -16,6 +16,7 @@ import { resolveProposalReviewDisposition, resolveReviewDisposition } from '../c
 import { livingExecutionLifecycleOperations } from './execution/living-execution-lifecycle.ts';
 import type { ProviderAssignmentExplanationWrite } from '../observability/assignment-explanation-service.ts';
 import { projectCompletedPlanningOutputs,type AssignmentPlanningOutputStore } from '../planning/assignment-planning-output-service.ts';
+import { integrateAssignmentEstimate } from '../planning/estimates/integration.ts';
 import { normalizeProviderAssignmentLeaseSeconds } from './assignment-lease-service.ts';
 import { terminalAssignmentAuthority } from './assignment-terminal-authority.ts';
 import { composeAssignmentLifecycleOutput } from './assignment-lifecycle-output.ts';
@@ -290,6 +291,7 @@ export class ProviderAssignmentLifecycleService {
 		const assignmentResult = assignment.assignmentAttempt
 			? validateAssignmentResultCompletion(assignment, terminalInput as JsonRecord)
 			: null;
+		if (assignmentResult) await integrateAssignmentEstimate(this.store, assignment, assignmentResult);
 		const reviewDisposition = assignmentResult
 			? await resolveReviewDisposition(this.store, assignment, assignmentResult)
 			: null;
diff --git a/src/api/capacity/services/capacity/assignments/planning/estimates/integration.ts b/src/api/capacity/services/capacity/assignments/planning/estimates/integration.ts
new file mode 100644
index 00000000..220714e4
--- /dev/null
+++ b/src/api/capacity/services/capacity/assignments/planning/estimates/integration.ts
@@ -0,0 +1,114 @@
+import { validatePortableContentData } from '@treeseed/sdk/content-validation';
+import type { AssignmentResult } from '@treeseed/sdk/agent-capacity';
+import { CapacityGovernanceError } from '../../../../../database.ts';
+import type { DurableProviderAssignment } from '../../../../../repositories/capacity/assignments/assignment.ts';
+import { readExactProposal } from '../../../../../../governance/executable-proposal.ts';
+import { commitProposalVersionContent } from '../../../../../../control-plane/governance/proposal-version-content.ts';
+import { resolveKnowledgeGatewayConnection } from '../../../../../../knowledge/gateway-treedx-connection.ts';
+import type { AssignmentPlanningOutputStore } from '../assignment-planning-output-service.ts';
+
+type Row = Record<string, unknown>;
+const record = (value: unknown): Row => value && typeof value === 'object' && !Array.isArray(value) ? value as Row : {};
+const text = (value: unknown): string => typeof value === 'string' ? value.trim() : '';
+const stable = (value: unknown): string => Array.isArray(value) ? `[${value.map(stable).join(',')}]`
+	: value && typeof value === 'object' ? `{${Object.entries(value as Row).sort(([a], [b]) => a.localeCompare(b))
+		.map(([key, item]) => `${JSON.stringify(key)}:${stable(item)}`).join(',')}}` : JSON.stringify(value);
+
+function workItems(value: Row): Row[] {
+	return Array.isArray(record(value.executionPlan).workItems) ? record(value.executionPlan).workItems as Row[] : [];
+}
+
+/** One estimate belongs to the exact work item selected by the graph, not to a new plan authority. */
+export function mergeAssignmentEstimate(input: {
+	frozen: Row; candidate: Row; current: Row; workItemId: string | null;
+}): Row {
+	const frozenItems = workItems(input.frozen);
+	const candidateItems = workItems(input.candidate);
+	const currentItems = workItems(input.current);
+	const reviewer = input.workItemId === null;
+	const index = reviewer ? -1 : frozenItems.findIndex((item) => item.id === input.workItemId);
+	if ((!reviewer && index < 0) || !frozenItems.length || frozenItems.length !== candidateItems.length || frozenItems.length !== currentItems.length
+		|| new Set(frozenItems.map((item) => item.id)).size !== frozenItems.length) {
+		throw new CapacityGovernanceError('assignment_estimate_work_item_invalid', 'Estimator result does not target one frozen proposal work item.', 409);
+	}
+	const withoutEstimate = (item: Row): Row => { const { estimate: _estimate, reviewEstimate: _reviewEstimate, ...rest } = item; return rest; };
+	if (stable({ ...input.candidate, executionPlan: { ...record(input.candidate.executionPlan), workItems: candidateItems.map(withoutEstimate) } })
+		!== stable({ ...input.frozen, executionPlan: { ...record(input.frozen.executionPlan), workItems: frozenItems.map(withoutEstimate) } })) {
+		throw new CapacityGovernanceError('assignment_estimate_unrelated_change', 'Estimator result changed proposal fields outside its assigned estimate.', 409);
+	}
+	if (candidateItems.some((item, itemIndex) =>
+		stable(reviewer ? item.estimate : item.reviewEstimate) !== stable(reviewer ? frozenItems[itemIndex].estimate : frozenItems[itemIndex].reviewEstimate)
+		|| (!reviewer && itemIndex !== index && stable(item.estimate) !== stable(frozenItems[itemIndex].estimate)))) {
+		throw new CapacityGovernanceError('assignment_estimate_unrelated_change', 'Estimator result changed another work item estimate.', 409);
+	}
+	if (currentItems.some((item, itemIndex) => item.id !== frozenItems[itemIndex].id
+		|| stable(withoutEstimate(item)) !== stable(withoutEstimate(frozenItems[itemIndex])))) {
+		throw new CapacityGovernanceError('assignment_estimate_source_changed', 'Current proposal work items no longer match the frozen assignment source.', 409);
+	}
+	const field = reviewer ? 'reviewEstimate' : 'estimate';
+	const targets = reviewer ? frozenItems.map((_, itemIndex) => itemIndex) : [index];
+	for (const target of targets) {
+		const estimate = record(candidateItems[target][field]);
+		if (!Object.keys(estimate).length || !text(estimate.rationale)) throw new CapacityGovernanceError(
+			'assignment_estimate_missing', 'Estimator result must include a structured estimate and rationale for each assigned work item.', 409);
+		const existing = currentItems[target][field];
+		if (existing !== undefined && stable(existing) !== stable(estimate)) throw new CapacityGovernanceError(
+			'assignment_estimate_conflict', 'The assigned work item already has a different estimate.', 409);
+	}
+	return { ...input.current, executionPlan: { ...record(input.current.executionPlan),
+		workItems: currentItems.map((item, itemIndex) => targets.includes(itemIndex)
+			? { ...item, [field]: candidateItems[itemIndex][field] } : item) } };
+}
+
+export async function integrateAssignmentEstimate(
+	store: AssignmentPlanningOutputStore, assignment: DurableProviderAssignment, result: AssignmentResult,
+): Promise<void> {
+	if (assignment.assignmentAttempt?.effectiveProfile.activity !== 'estimating') return;
+	const attempt = assignment.assignmentAttempt;
+	if (attempt.sourceRef.model !== 'proposal' || !assignment.agentId) throw new CapacityGovernanceError(
+		'assignment_estimate_source_missing', 'Estimating assignment lacks a frozen proposal, work item, or agent.', 409);
+	const proposal = await store.getGovernanceProposal(attempt.sourceRef.id);
+	if (!proposal || proposal.projectId !== assignment.projectId || proposal.teamId !== assignment.teamId) throw new CapacityGovernanceError(
+		'assignment_estimate_proposal_mismatch', 'Estimating assignment proposal is outside its project and team.', 409);
+	const frozen = await readExactProposal(store, proposal, attempt.sourceRef);
+	const current = await readExactProposal(store, proposal);
+	const matches = result.references.filter((reference): reference is Extract<AssignmentResult['references'][number], { kind: 'treedx' }> => reference.kind === 'treedx'
+		&& reference.projectId === assignment.projectId && reference.repository === attempt.sourceRef.repository
+		&& reference.path === attempt.sourceRef.path);
+	if (matches.length !== 1) throw new CapacityGovernanceError('assignment_estimate_reference_invalid',
+		'Estimator result must cite exactly one proposal commit in its authorized project library.', 409);
+	const reference = matches[0]!;
+	if (attempt.workspace.mode !== 'treedx' || reference.workspaceId !== attempt.workspace.workspaceId) throw new CapacityGovernanceError(
+		'assignment_estimate_workspace_mismatch', 'Estimator result did not originate from its authorized workspace.', 409);
+	const connection = await resolveKnowledgeGatewayConnection(store, { projectId: assignment.projectId,
+		write: false, relationPaths: true, readRefs: [reference.commit] });
+	if (!connection || connection.repositoryId !== reference.repository) throw new CapacityGovernanceError(
+		'assignment_estimate_repository_changed', 'Estimator proposal repository binding changed.', 409);
+	const response = record(await connection.client.readRepositoryFile({ repoId: reference.repository,
+		ref: reference.commit, path: reference.path, encoding: 'utf8', parseFrontmatter: true, allowProtected: true }));
+	if (text(response.resolvedRef) !== reference.commit) throw new CapacityGovernanceError(
+		'assignment_estimate_ref_moved', 'Estimator proposal result did not resolve to its exact commit.', 409);
+	const file = record(response.file ?? (Array.isArray(response.files) ? response.files[0] : null));
+	const source = text(file.content);
+	if (!source) throw new CapacityGovernanceError(
+		'assignment_estimate_content_missing', 'Estimator proposal result has no content.', 409);
+	const parsed = validatePortableContentData('proposal', record(file.frontmatter));
+	if (!parsed.ok || !parsed.data) throw new CapacityGovernanceError('assignment_estimate_content_invalid',
+		'Estimator proposal content is invalid.', 409, { diagnostics: parsed.diagnostics });
+	const candidate = parsed.data as Row;
+	const merged = mergeAssignmentEstimate({ frozen: frozen.definition, candidate, current: current.definition,
+		workItemId: attempt.workItemId ?? null });
+	if (stable(merged) === stable(current.definition)) return;
+	const allEstimated = workItems(merged).every((item) => Object.keys(record(item.estimate)).length > 0
+		&& (item.review !== 'required' || Object.keys(record(item.reviewEstimate)).length > 0));
+	const authored = await commitProposalVersionContent({ store, proposal,
+		principal: { id: assignment.agentId, name: assignment.agentId },
+		update: { title: proposal.title, summary: proposal.summary, body: proposal.body,
+			proposalTypes: proposal.proposalTypes, status: allEstimated ? 'ready' : merged.status,
+			objectiveRefs: merged.objectiveRefs, evidenceRefs: merged.evidenceRefs,
+			discussionRef: merged.discussionRef, executionPlan: merged.executionPlan,
+			workdayId: assignment.workDayId, expectedProposalVersion: proposal.activeVersion,
+			changeReason: `Integrate ${attempt.workItemId ?? 'review'} estimate from assignment ${assignment.id}.` } });
+	await store.updateGovernanceProposalDraft({ id: assignment.agentId, type: 'agent' }, text(proposal.id),
+		{ ...authored.update, createdByType: 'agent', createdById: assignment.agentId });
+}
diff --git a/tests/unit/control-plane/capacity/planning/assignment-estimate-integration.test.ts b/tests/unit/control-plane/capacity/planning/assignment-estimate-integration.test.ts
new file mode 100644
index 00000000..379a668c
--- /dev/null
+++ b/tests/unit/control-plane/capacity/planning/assignment-estimate-integration.test.ts
@@ -0,0 +1,59 @@
+import { describe, expect, it } from 'vitest';
+import { mergeAssignmentEstimate } from '../../../../../src/api/capacity/services/capacity/assignments/planning/estimates/integration.ts';
+
+const estimate = { minimumSeconds: 100, expectedSeconds: 200, maximumSeconds: 300, rationale: 'Exact source inspection.' };
+const frozen = { id: 'proposal-1', projectId: 'project-1', status: 'draft', executionPlan: { workItems: [
+	{ id: 'research', objective: 'Inspect the source.' },
+	{ id: 'implementation', objective: 'Implement the contract.' },
+] } };
+const candidate = { ...frozen, executionPlan: { workItems: [
+	frozen.executionPlan.workItems[0], { ...frozen.executionPlan.workItems[1], estimate },
+] } };
+
+describe('exact estimator result integration', () => {
+	it('merges only the assigned estimate while preserving another completed estimate', () => {
+		const prior = { minimumSeconds: 60, expectedSeconds: 120, maximumSeconds: 180, rationale: 'Research evidence.' };
+		const current = { ...frozen, executionPlan: { workItems: [
+			{ ...frozen.executionPlan.workItems[0], estimate: prior }, frozen.executionPlan.workItems[1],
+		] } };
+		const merged = mergeAssignmentEstimate({ frozen, candidate, current, workItemId: 'implementation' });
+		expect(merged.executionPlan).toEqual({ workItems: [
+			{ ...frozen.executionPlan.workItems[0], estimate: prior },
+			{ ...frozen.executionPlan.workItems[1], estimate },
+		] });
+		expect(mergeAssignmentEstimate({ frozen, candidate, current: merged, workItemId: 'implementation' })).toEqual(merged);
+	});
+	it('rejects unrelated content and a competing estimate', () => {
+		expect(() => mergeAssignmentEstimate({ frozen, candidate: { ...candidate, title: 'New authority' }, current: frozen,
+			workItemId: 'implementation' })).toThrow('outside its assigned estimate');
+		const current = { ...frozen, executionPlan: { workItems: [frozen.executionPlan.workItems[0],
+			{ ...frozen.executionPlan.workItems[1], estimate: { ...estimate, expectedSeconds: 250 } }] } };
+		expect(() => mergeAssignmentEstimate({ frozen, candidate, current, workItemId: 'implementation' })).toThrow('different estimate');
+	});
+	it('rejects missing, mistargeted, or changed work items', () => {
+		expect(() => mergeAssignmentEstimate({ frozen, candidate: frozen, current: frozen,
+			workItemId: 'implementation' })).toThrow('structured estimate');
+		expect(() => mergeAssignmentEstimate({ frozen, candidate, current: frozen,
+			workItemId: 'unknown' })).toThrow('frozen proposal work item');
+		const changed = { ...frozen, executionPlan: { workItems: [frozen.executionPlan.workItems[0],
+			{ ...frozen.executionPlan.workItems[1], objective: 'Changed objective.' }] } };
+		expect(() => mergeAssignmentEstimate({ frozen, candidate, current: changed,
+			workItemId: 'implementation' })).toThrow('no longer match');
+	});
+	it('merges Reviewer estimates for every work item without replacing actor estimates', () => {
+		const current = { ...frozen, executionPlan: { workItems: [
+			{ ...frozen.executionPlan.workItems[0], estimate }, frozen.executionPlan.workItems[1],
+		] } };
+		const reviewEstimate = { ...estimate, rationale: 'Independent review of the work.' };
+		const reviewCandidate = { ...frozen, executionPlan: { workItems: frozen.executionPlan.workItems.map((item) =>
+			({ ...item, reviewEstimate })) } };
+		const merged = mergeAssignmentEstimate({ frozen, candidate: reviewCandidate, current, workItemId: null });
+		expect((merged.executionPlan as { workItems: unknown[] }).workItems).toEqual([
+			{ ...current.executionPlan.workItems[0], reviewEstimate },
+			{ ...current.executionPlan.workItems[1], reviewEstimate },
+		]);
+		expect(() => mergeAssignmentEstimate({ frozen, candidate: { ...reviewCandidate,
+			executionPlan: { workItems: [reviewCandidate.executionPlan.workItems[0], frozen.executionPlan.workItems[1]] } },
+			current, workItemId: null })).toThrow('each assigned work item');
+	});
+});