diff --git a/packages/@n8n/instance-ai/src/index.ts b/packages/@n8n/instance-ai/src/index.ts
index bc0f05859fe..4be89eb3de9 100644
--- a/packages/@n8n/instance-ai/src/index.ts
+++ b/packages/@n8n/instance-ai/src/index.ts
@@ -27,6 +27,7 @@ import type * as UsageAccumulatorMod from './stream/usage-accumulator';
 import type * as ToolsMod from './tools';
 import type * as AgentPersistenceMod from './tools/orchestration/agent-persistence';
 import type * as SanitizeWebContentMod from './tools/web-research/sanitize-web-content';
+import type * as AgentSnapshotEventMod from './tracing/agent-snapshot-event';
 import type * as LangsmithTracingMod from './tracing/langsmith-tracing';
 import type * as TraceReplayMod from './tracing/trace-replay';
 import type * as AgentTreeMod from './utils/agent-tree';
@@ -88,6 +89,9 @@ const loadLangsmithTracing = lazyModule(
 const loadTraceReplay = lazyModule(
 	() => require('./tracing/trace-replay') as typeof TraceReplayMod,
 );
+const loadAgentSnapshotEvent = lazyModule(
+	() => require('./tracing/agent-snapshot-event') as typeof AgentSnapshotEventMod,
+);
 const loadInstanceAgent = lazyModule(
 	() => require('./agent/instance-agent') as typeof InstanceAgentMod,
 );
@@ -216,6 +220,13 @@ export const createDomainAccessTracker: typeof DomainAccessMod.createDomainAcces
 export type { DomainAccessTracker } from './domain-access';
 export type { SubmitLangsmithUserFeedbackOptions } from './tracing/langsmith-tracing';
 
+export const emitAgentSnapshotTraceEvent: typeof AgentSnapshotEventMod.emitAgentSnapshotTraceEvent =
+	lazyFunction(() => loadAgentSnapshotEvent().emitAgentSnapshotTraceEvent);
+export type {
+	AgentSnapshotArtifact,
+	AgentSnapshotReason,
+} from './tracing/agent-snapshot-event';
+
 export const createInstanceAiTraceContext: typeof LangsmithTracingMod.createInstanceAiTraceContext =
 	lazyFunction(() => loadLangsmithTracing().createInstanceAiTraceContext);
 
diff --git a/packages/@n8n/instance-ai/src/tools/orchestration/__tests__/build-agent.tool.test.ts b/packages/@n8n/instance-ai/src/tools/orchestration/__tests__/build-agent.tool.test.ts
index 017e207fc97..1bf1faa8dbb 100644
--- a/packages/@n8n/instance-ai/src/tools/orchestration/__tests__/build-agent.tool.test.ts
+++ b/packages/@n8n/instance-ai/src/tools/orchestration/__tests__/build-agent.tool.test.ts
@@ -577,6 +577,128 @@ describe('build-agent tool', () => {
 		});
 	});
 
+	// An eval case needs the agent BEFORE the turn and again after a pass that
+	// changed it. Nothing else in the trace records either.
+	describe('agent-snapshot', () => {
+		const ARTIFACT = {
+			config: { name: 'Support Triage' },
+			skills: {},
+			configHash: 'hash-1',
+		} as unknown as Awaited<
+			ReturnType<NonNullable<InstanceAiBuilderDelegate['readAgentArtifact']>>
+		>;
+
+		/** The read only runs under a live trace, so every case here needs one. */
+		function makeTracedContext() {
+			const made = makeContext();
+			made.context.tracing = makeTracingStub().tracing;
+			return made;
+		}
+
+		it('snapshots an adopted agent before the builder can change it', async () => {
+			const { context, delegate } = makeTracedContext();
+			vi.mocked(delegate.readAgentArtifact!).mockResolvedValue(ARTIFACT);
+			vi.mocked(delegate.streamBuild).mockImplementation(async () => {
+				// Ordering is the point: read before the builder runs, or the
+				// "baseline" is the state the turn produced.
+				expect(delegate.readAgentArtifact).toHaveBeenCalledWith('agent-existing');
+				return await Promise.resolve(fakeStream([], 'Editing it.'));
+			});
+
+			await runTool(context, { message: 'Add a tool', agentId: 'agent-existing' });
+
+			expect(delegate.readAgentArtifact).toHaveBeenCalledWith('agent-existing');
+		});
+
+		it('takes no baseline for an agent it just created — there is no prior state', async () => {
+			const { context, delegate } = makeTracedContext();
+			vi.mocked(delegate.createAgent).mockResolvedValue({
+				agentId: 'agent-1',
+				projectId: 'proj-1',
+			});
+			vi.mocked(delegate.readAgentArtifact!).mockResolvedValue(ARTIFACT);
+			vi.mocked(delegate.streamBuild).mockResolvedValue(fakeStream([], 'Built it.'));
+
+			await runTool(context, { message: 'Build it', name: 'New Agent' });
+
+			expect(delegate.readAgentArtifact).not.toHaveBeenCalled();
+		});
+
+		it('snapshots again after a pass that changed the config', async () => {
+			const { context, delegate } = makeTracedContext();
+			vi.mocked(delegate.readAgentArtifact!).mockResolvedValue(ARTIFACT);
+			vi.mocked(delegate.streamBuild).mockResolvedValue(
+				fakeStream(
+					[toolCallChunk('call-1', 'patch_config'), toolResultChunk('call-1')],
+					'Updated the config.',
+				),
+			);
+
+			await runTool(context, { message: 'Add a tool', agentId: 'agent-existing' });
+
+			// Baseline + outcome.
+			expect(delegate.readAgentArtifact).toHaveBeenCalledTimes(2);
+		});
+
+		it('does not re-read after a pass that changed nothing', async () => {
+			const { context, delegate } = makeTracedContext();
+			vi.mocked(delegate.readAgentArtifact!).mockResolvedValue(ARTIFACT);
+			vi.mocked(delegate.streamBuild).mockResolvedValue(fakeStream([], 'Nothing to change.'));
+
+			await runTool(context, { message: 'What does it do?', agentId: 'agent-existing' });
+
+			expect(delegate.readAgentArtifact).toHaveBeenCalledTimes(1);
+		});
+
+		it('reads nothing when tracing is off — there is nowhere to emit', async () => {
+			// Tracing is disabled on most instances, and the read costs a scope
+			// check plus two queries on every non-create build-agent turn.
+			const { context, delegate } = makeContext();
+			vi.mocked(delegate.streamBuild).mockResolvedValue(
+				fakeStream(
+					[toolCallChunk('call-1', 'patch_config'), toolResultChunk('call-1')],
+					'Updated the config.',
+				),
+			);
+
+			await runTool(context, { message: 'Add a tool', agentId: 'agent-existing' });
+
+			expect(delegate.readAgentArtifact).not.toHaveBeenCalled();
+		});
+
+		it('emits the event with the config, the agent id and the reason', async () => {
+			const { context, delegate } = makeContext();
+			const { tracing } = makeTracingStub();
+			context.tracing = tracing;
+			vi.mocked(delegate.readAgentArtifact!).mockResolvedValue(ARTIFACT);
+			vi.mocked(delegate.streamBuild).mockResolvedValue(fakeStream([], 'Editing it.'));
+
+			await runTool(context, { message: 'Add a tool', agentId: 'agent-existing' });
+
+			const snapshotRuns = vi
+				.mocked(tracing.startChildRun)
+				.mock.calls.filter(([, init]) => (init as { name?: string }).name === 'agent-snapshot');
+			expect(snapshotRuns).toHaveLength(1);
+			expect(snapshotRuns[0][1]).toMatchObject({
+				runType: 'chain',
+				metadata: { agent_id: 'agent-existing', snapshot_reason: 'target-resolved' },
+			});
+		});
+
+		it('builds normally on a host whose delegate cannot read agents', async () => {
+			// An older host doesn't implement the read; that must not break building.
+			const delegate = mock<InstanceAiBuilderDelegate>();
+			delegate.readAgentArtifact = undefined;
+			const { context } = makeContext({ delegate });
+			context.tracing = makeTracingStub().tracing;
+			vi.mocked(delegate.streamBuild).mockResolvedValue(fakeStream([], 'Editing it.'));
+
+			const result = await runTool(context, { message: 'Add a tool', agentId: 'agent-existing' });
+
+			expect(result).toMatchObject({ ok: true, builderReply: 'Editing it.' });
+		});
+	});
+
 	describe('configUpdated', () => {
 		it.each(['write_config', 'patch_config', 'publish_agent', 'unpublish_agent'])(
 			'is true when the work summary has a succeeded %s call',
@@ -1771,6 +1893,44 @@ describe('build-agent tool', () => {
 			},
 		);
 
+		it('snapshots the config a friendly-mapped resume failure left behind', async () => {
+			// A pass mutated the config, suspended for confirmation, and the resume
+			// failed. The tool still reports configUpdated, so the post-state a
+			// repair-shaped case grades has to exist in the trace.
+			const { context, delegate } = makeContext();
+			const { tracing } = makeTracingStub();
+			context.tracing = tracing;
+			context.domainContext!.agentBuilderTarget = { agentId: 'agent-1', projectId: 'proj-1' };
+			vi.mocked(delegate.findOpenSuspensions).mockResolvedValue([
+				{ runId: 'builder-run-1', toolCallId: 'builder-call-1' },
+			]);
+			vi.mocked(delegate.readAgentArtifact!).mockResolvedValue({
+				config: { name: 'Support Triage' },
+				configHash: 'hash-1',
+			} as unknown as Awaited<
+				ReturnType<NonNullable<InstanceAiBuilderDelegate['readAgentArtifact']>>
+			>);
+			vi.mocked(delegate.resumeBuild).mockResolvedValue(
+				throwingStream(new FakeBuilderCheckpointUnavailableError('Checkpoint expired.')),
+			);
+
+			const result = await runToolWithCtx(
+				context,
+				{ message: 'Build it', name: 'New Agent' },
+				{
+					resumeData: { approved: true },
+					suspendPayload: suspendPayloadWithCheckpoint({ configUpdated: true }),
+				},
+			);
+
+			expect(result).toMatchObject({ ok: false, configUpdated: true });
+			const snapshots = vi
+				.mocked(tracing.startChildRun)
+				.mock.calls.filter(([, init]) => (init as { name?: string }).name === 'agent-snapshot');
+			expect(snapshots).toHaveLength(1);
+			expect(snapshots[0][1]).toMatchObject({ metadata: { snapshot_reason: 'config-updated' } });
+		});
+
 		it('still rethrows an unrelated error thrown mid-stream during resume', async () => {
 			const { context, delegate } = makeContext();
 			context.domainContext!.agentBuilderTarget = { agentId: 'agent-1', projectId: 'proj-1' };
diff --git a/packages/@n8n/instance-ai/src/tools/orchestration/build-agent.tool.ts b/packages/@n8n/instance-ai/src/tools/orchestration/build-agent.tool.ts
index 4c293aaf707..4979af9aa1d 100644
--- a/packages/@n8n/instance-ai/src/tools/orchestration/build-agent.tool.ts
+++ b/packages/@n8n/instance-ai/src/tools/orchestration/build-agent.tool.ts
@@ -47,11 +47,17 @@ import {
 	type AgentBuilderTarget,
 } from './agent-target-binding';
 import { instanceAiBuilderThreadPrefix } from './builder-thread-id';
+import { failTraceRun, finishTraceRun, startSubAgentTrace, withTraceRun } from './tracing-utils';
 import {
 	consumeStreamCascading,
 	type ConsumeStreamCascadingResult,
 } from '../../stream/consume-with-hitl';
 import type { WorkSummary } from '../../stream/work-summary-accumulator';
+import {
+	emitAgentSnapshotTraceEvent,
+	type AgentSnapshotArtifact,
+	type AgentSnapshotReason,
+} from '../../tracing/agent-snapshot-event';
 import type {
 	BuilderTurnStream,
 	InstanceAiBuilderDelegate,
@@ -60,7 +66,6 @@ import type {
 	SessionWorkflowRef,
 } from '../../types';
 import { ORCHESTRATION_TOOL_IDS } from '../tool-ids';
-import { failTraceRun, finishTraceRun, startSubAgentTrace, withTraceRun } from './tracing-utils';
 
 const BUILDER_SUB_AGENT_ROLE = 'agent-builder';
 const BUILDER_SUB_AGENT_KIND = 'agent-builder';
@@ -333,6 +338,36 @@ function publishAgentBuilderCancelled(context: OrchestrationContext, builderAgen
 	});
 }
 
+/** Emit an `agent-snapshot` for the builder's target. Best-effort at both ends. */
+async function snapshotAgent(
+	context: OrchestrationContext,
+	delegate: InstanceAiBuilderDelegate,
+	target: AgentBuilderTarget,
+	reason: AgentSnapshotReason,
+): Promise<void> {
+	// No trace, no read — the delegate read costs a scope check and two queries.
+	// Matches the service-side call site, which early-returns on `!tracing`.
+	if (!context.tracing) return;
+	let artifact: AgentSnapshotArtifact | null = null;
+	try {
+		// An optional method may be absent, or return a non-promise on a mocked host.
+		artifact = (await delegate.readAgentArtifact?.(target.agentId)) ?? null;
+	} catch (error) {
+		context.logger.debug(
+			`[agent-snapshot] ${reason} read for ${target.agentId} failed: ${error instanceof Error ? error.message : String(error)}`,
+		);
+		return;
+	}
+	if (!artifact) return;
+	await emitAgentSnapshotTraceEvent(context.tracing, {
+		agentId: target.agentId,
+		projectId: target.projectId,
+		reason,
+		artifact,
+		logger: context.logger,
+	});
+}
+
 /** Publish the terminal `agent-completed` event and map the result to the tool output.
  *  A cancelled turn is intercepted by the caller, so that status never arrives here. */
 async function finishTurn(
@@ -412,6 +447,15 @@ async function runBuilderConsumeLoop(params: {
 		dedupeBase,
 	} = params;
 
+	// Every settled return goes through here, so the state a pass left behind is
+	// snapshotted on the error returns too — a pass that mutated the config, then
+	// suspended and failed on resume, is exactly the post-state a repair case
+	// grades. A suspend resumes and settles through here; a cancel throws past it.
+	const settle = async (output: BuildAgentOutput): Promise<BuildAgentOutput> => {
+		if (output.configUpdated) await snapshotAgent(context, delegate, target, 'config-updated');
+		return output;
+	};
+
 	const traceRun = await startSubAgentTrace(context, {
 		agentId: builderAgentId,
 		role: BUILDER_SUB_AGENT_ROLE,
@@ -445,12 +489,12 @@ async function runBuilderConsumeLoop(params: {
 		// not from the `delegate.streamBuild`/`resumeBuild` call sites.
 		const message = publishAgentBuilderFailure(context, builderAgentId, error);
 		if (isFriendlyMappableBuilderError(error)) {
-			return {
+			return await settle({
 				ok: false,
 				error: message,
 				configUpdated: carriedConfigUpdated,
 				...targetIdentity(target),
-			};
+			});
 		}
 		throw error;
 	}
@@ -499,7 +543,7 @@ async function runBuilderConsumeLoop(params: {
 			await failTraceRun(context, traceRun, new Error(output.error ?? 'builder run failed'));
 		}
 		await context.claimSubAgentUsage?.(dedupeBase, result.usage?.usage ?? [], result.status);
-		return { ...output, ...targetIdentity(target) };
+		return await settle({ ...output, ...targetIdentity(target) });
 	}
 
 	const configUpdatedSoFar = carriedConfigUpdated || didUpdateConfig(result.workSummary);
@@ -528,12 +572,12 @@ async function runBuilderConsumeLoop(params: {
 			result.usage?.usage ?? [],
 			'errored',
 		);
-		return {
+		return await settle({
 			ok: false,
 			error: message,
 			configUpdated: configUpdatedSoFar,
 			...targetIdentity(target),
-		};
+		});
 	}
 
 	// The builder-level requestId must not leak up: the FE confirms against the
@@ -954,6 +998,12 @@ export function createBuildAgentTool(context: OrchestrationContext) {
 
 			publishAgentSpawned(context, builderAgentId, boundTarget);
 
+			// Before the builder touches it: a repair-shaped eval case seeds from the
+			// state the turn opened on. A new agent has no prior state.
+			if (resolution.mode !== 'create') {
+				await snapshotAgent(context, delegate, boundTarget, 'target-resolved');
+			}
+
 			let turn: BuilderTurnStream;
 			try {
 				turn = await delegate.streamBuild(boundTarget.agentId, outboundMessage, session);
diff --git a/packages/@n8n/instance-ai/src/tools/tool-ids.ts b/packages/@n8n/instance-ai/src/tools/tool-ids.ts
index b4e69c1f7d4..f331bd65311 100644
--- a/packages/@n8n/instance-ai/src/tools/tool-ids.ts
+++ b/packages/@n8n/instance-ai/src/tools/tool-ids.ts
@@ -24,6 +24,10 @@ export const DOMAIN_TOOL_IDS = {
  *  SDK re-parse; excluded by name from rebuilt transcripts. */
 export const COMPILED_WORKFLOW_TRACE_RUN_NAME = 'compiled-workflow';
 
+/** Trace-only chain run carrying an agent's config + skills, for seed
+ *  reconstruction — the agent counterpart of the event above. */
+export const AGENT_SNAPSHOT_TRACE_RUN_NAME = 'agent-snapshot';
+
 export const ORCHESTRATION_TOOL_IDS = {
 	CREATE_TASKS: 'create-tasks',
 	TASK_CONTROL: 'task-control',
diff --git a/packages/@n8n/instance-ai/src/tracing/__tests__/agent-snapshot-event.test.ts b/packages/@n8n/instance-ai/src/tracing/__tests__/agent-snapshot-event.test.ts
new file mode 100644
index 00000000000..1df9d067015
--- /dev/null
+++ b/packages/@n8n/instance-ai/src/tracing/__tests__/agent-snapshot-event.test.ts
@@ -0,0 +1,207 @@
+// The `agent-snapshot` trace event. Mirrors the `compiled-workflow` tests in
+// `tools/workflows/__tests__/build-workflow.tool.test.ts`.
+import type { AgentJsonConfig, AgentSkill } from '@n8n/api-types';
+import { describe, expect, it, vi } from 'vitest';
+
+import type { InstanceAiTraceContext } from '../../types';
+import { emitAgentSnapshotTraceEvent } from '../agent-snapshot-event';
+
+const CONFIG = {
+	name: 'Support Triage',
+	instructions: 'You triage inbound support tickets.',
+} as unknown as AgentJsonConfig;
+
+const SKILLS: Record<string, AgentSkill> = {
+	skill_triage_rules: {
+		name: 'Triage rules',
+		instructions: 'Assign every ticket exactly one severity.',
+	} as unknown as AgentSkill,
+};
+
+function makeTracing() {
+	const actorRun = { id: 'actor-run-1' };
+	const startChildRun = vi.fn<
+		(parent: unknown, init: Record<string, unknown>) => Promise<{ id: string }>
+	>(async () => await Promise.resolve({ id: 'snapshot-run-1' }));
+	const finishRun = vi.fn<(run: { id: string }, opts: Record<string, unknown>) => Promise<void>>(
+		async () => await Promise.resolve(),
+	);
+	const tracing = { actorRun, startChildRun, finishRun } as unknown as InstanceAiTraceContext;
+	return { tracing, actorRun, startChildRun, finishRun };
+}
+
+const BASE = {
+	agentId: 'TrIaGe1234567890',
+	projectId: 'proj-1',
+	reason: 'attached' as const,
+};
+
+describe('emitAgentSnapshotTraceEvent', () => {
+	it('emits a trace-only child run carrying the config and skills', async () => {
+		const { tracing, actorRun, startChildRun, finishRun } = makeTracing();
+
+		const outcome = await emitAgentSnapshotTraceEvent(tracing, {
+			...BASE,
+			artifact: { config: CONFIG, skills: SKILLS, configHash: 'hash-1' },
+		});
+
+		expect(outcome).toBe('emitted');
+		expect(startChildRun).toHaveBeenCalledTimes(1);
+		const [parentRun, init] = startChildRun.mock.calls[0];
+		expect(parentRun).toBe(actorRun);
+		expect(init).toMatchObject({
+			name: 'agent-snapshot',
+			// Bookkeeping span: a tool-typed run reads as a real agent tool call.
+			runType: 'chain',
+			metadata: {
+				agent_id: BASE.agentId,
+				config_hash: 'hash-1',
+				snapshot_reason: 'attached',
+				// Lifts the export scrubber's structural depth cap for this payload.
+				raw_trace_payload: true,
+			},
+		});
+		const [, finishOpts] = finishRun.mock.calls[0];
+		expect(finishOpts).toMatchObject({
+			rawOutputs: true,
+			outputs: {
+				agentId: BASE.agentId,
+				projectId: 'proj-1',
+				configHash: 'hash-1',
+				reason: 'attached',
+				config: CONFIG,
+				skills: SKILLS,
+			},
+		});
+	});
+
+	it('emits a truncated marker instead of an oversized payload', async () => {
+		const { tracing, startChildRun, finishRun } = makeTracing();
+		const huge = {
+			name: 'Fat Agent',
+			instructions: 'x'.repeat(1_000_001),
+		} as unknown as AgentJsonConfig;
+
+		const outcome = await emitAgentSnapshotTraceEvent(tracing, {
+			...BASE,
+			artifact: { config: huge, configHash: 'hash-big' },
+		});
+
+		expect(outcome).toBe('emitted');
+		expect(startChildRun).toHaveBeenCalledTimes(1);
+		const [, finishOpts] = finishRun.mock.calls[0];
+		// The marker records that a state existed without shipping a rejected run.
+		expect(finishOpts.outputs).toEqual({
+			agentId: BASE.agentId,
+			projectId: 'proj-1',
+			configHash: 'hash-big',
+			reason: 'attached',
+			truncated: true,
+		});
+		expect(finishOpts).not.toHaveProperty('rawOutputs');
+	});
+
+	it('emits one event per agent+hash on a trace, so two triggers agree', async () => {
+		// Attach + target baselines both fire when a turn attaches then edits.
+		const { tracing, startChildRun } = makeTracing();
+		const artifact = { config: CONFIG, configHash: 'hash-1' };
+
+		expect(await emitAgentSnapshotTraceEvent(tracing, { ...BASE, artifact })).toBe('emitted');
+		expect(
+			await emitAgentSnapshotTraceEvent(tracing, {
+				...BASE,
+				reason: 'target-resolved',
+				artifact,
+			}),
+		).toBe('duplicate');
+		expect(startChildRun).toHaveBeenCalledTimes(1);
+	});
+
+	it('emits again once the config actually changes', async () => {
+		const { tracing, startChildRun } = makeTracing();
+
+		await emitAgentSnapshotTraceEvent(tracing, {
+			...BASE,
+			artifact: { config: CONFIG, configHash: 'hash-1' },
+		});
+		const outcome = await emitAgentSnapshotTraceEvent(tracing, {
+			...BASE,
+			reason: 'config-updated',
+			artifact: { config: CONFIG, configHash: 'hash-2' },
+		});
+
+		expect(outcome).toBe('emitted');
+		expect(startChildRun).toHaveBeenCalledTimes(2);
+	});
+
+	it('emits without a hash rather than treating one snapshot as a duplicate', async () => {
+		const { tracing, startChildRun } = makeTracing();
+		const artifact = { config: CONFIG, configHash: null };
+
+		expect(await emitAgentSnapshotTraceEvent(tracing, { ...BASE, artifact })).toBe('emitted');
+		expect(await emitAgentSnapshotTraceEvent(tracing, { ...BASE, artifact })).toBe('emitted');
+		// No hash means no dedupe key — better a duplicate row than a lost state.
+		expect(startChildRun).toHaveBeenCalledTimes(2);
+	});
+
+	it('reports a broken exporter as skipped instead of failing the caller', async () => {
+		// Tracing is bookkeeping: a broken exporter must not fail an agent build.
+		// The tracing layer swallows its own error, so this reads as "exported
+		// nothing" rather than as a bug here.
+		const tracing = {
+			actorRun: { id: 'actor-run-1' },
+			startChildRun: vi.fn(async () => await Promise.reject(new Error('exporter down'))),
+			finishRun: vi.fn(),
+		} as unknown as InstanceAiTraceContext;
+
+		await expect(
+			emitAgentSnapshotTraceEvent(tracing, {
+				...BASE,
+				artifact: { config: CONFIG, configHash: 'hash-1' },
+			}),
+		).resolves.toBe('skipped');
+	});
+
+	it('retries after a skip instead of burning the hash on a trace that exported nothing', async () => {
+		const { tracing, startChildRun } = makeTracing();
+		const artifact = { config: CONFIG, configHash: 'hash-1' };
+		startChildRun.mockRejectedValueOnce(new Error('exporter down'));
+
+		expect(await emitAgentSnapshotTraceEvent(tracing, { ...BASE, artifact })).toBe('skipped');
+		expect(await emitAgentSnapshotTraceEvent(tracing, { ...BASE, artifact })).toBe('emitted');
+		expect(startChildRun).toHaveBeenCalledTimes(2);
+	});
+
+	it('retries after a failure instead of burning the hash', async () => {
+		const { tracing, startChildRun } = makeTracing();
+		const circular: Record<string, unknown> = { name: 'Looper' };
+		circular.self = circular;
+
+		expect(
+			await emitAgentSnapshotTraceEvent(tracing, {
+				...BASE,
+				artifact: { config: circular as unknown as AgentJsonConfig, configHash: 'hash-1' },
+			}),
+		).toBe('failed');
+		expect(
+			await emitAgentSnapshotTraceEvent(tracing, {
+				...BASE,
+				artifact: { config: CONFIG, configHash: 'hash-1' },
+			}),
+		).toBe('emitted');
+		expect(startChildRun).toHaveBeenCalledTimes(1);
+	});
+
+	it('reports a config it cannot serialize as failed, without throwing', async () => {
+		const { tracing } = makeTracing();
+		const circular: Record<string, unknown> = { name: 'Looper' };
+		circular.self = circular;
+
+		await expect(
+			emitAgentSnapshotTraceEvent(tracing, {
+				...BASE,
+				artifact: { config: circular as unknown as AgentJsonConfig, configHash: 'hash-1' },
+			}),
+		).resolves.toBe('failed');
+	});
+});
diff --git a/packages/@n8n/instance-ai/src/tracing/__tests__/agent-snapshot-trace-fidelity.test.ts b/packages/@n8n/instance-ai/src/tracing/__tests__/agent-snapshot-trace-fidelity.test.ts
new file mode 100644
index 00000000000..6232fd12ec2
--- /dev/null
+++ b/packages/@n8n/instance-ai/src/tracing/__tests__/agent-snapshot-trace-fidelity.test.ts
@@ -0,0 +1,134 @@
+import { jsonParse } from 'n8n-workflow';
+import { describe, it, expect } from 'vitest';
+
+import { AGENT_SNAPSHOT_TRACE_RUN_NAME } from '../../tools/tool-ids';
+import { GEN_AI_COMPLETION, redactLangSmithTelemetrySpan } from '../trace-payloads';
+
+/** A config nested past the sanitizer's depth cap: a node tool's parameters sit
+ *  at depth 5+ under the payload root, and its filter conditions at depth 9+. */
+function deepAgentConfig() {
+	return {
+		name: 'Support Triage',
+		model: 'anthropic/claude-sonnet-4-5',
+		credential: 'cred-anthropic-1',
+		instructions:
+			'Escalate anything a customer marks as production-down to the ops rota before replying. Older key sk-ant-api03-aaaaaaaaaaaaaaaa was rotated.',
+		tools: [
+			{
+				type: 'node',
+				name: 'send_reply',
+				node: {
+					nodeType: 'n8n-nodes-base.gmail',
+					nodeTypeVersion: 2.1,
+					nodeParameters: {
+						resource: 'message',
+						options: {
+							filters: {
+								conditions: [
+									{
+										leftValue: '={{ $json.priority }}',
+										rightValue: 'urgent',
+										operator: { type: 'string', operation: 'equals' },
+									},
+								],
+							},
+						},
+					},
+					credentials: { gmailOAuth2: { id: 'cred-2', name: 'Support Inbox' } },
+				},
+			},
+		],
+	} as const;
+}
+
+function deepSkills() {
+	return {
+		skill_triage_rules: {
+			name: 'Triage rules',
+			description: 'How to grade an inbound ticket.',
+			instructions:
+				'Assign every ticket exactly one severity, and never downgrade one a customer raised.',
+			references: [
+				// `agentSkillReferenceSchema` requires a markdown path under `references/`,
+				// so a fixture using anything else isn't the shape a real snapshot carries.
+				{
+					path: 'references/severity.md',
+					content: 'Sev1 means the product is unusable for everyone.',
+				},
+			],
+		},
+	} as const;
+}
+
+function exportSpan(rawPayload: boolean) {
+	const span = redactLangSmithTelemetrySpan({
+		name: AGENT_SNAPSHOT_TRACE_RUN_NAME,
+		attributes: {
+			// Producer-set flag (emitTraceOnlyChildRun with rawOutputs) — the deep
+			// tier keys on this, not on the (claimable) span name.
+			...(rawPayload ? { 'langsmith.metadata.raw_trace_payload': true } : {}),
+			[GEN_AI_COMPLETION]: JSON.stringify({
+				agentId: 'TrIaGe1234567890',
+				projectId: 'proj-1',
+				configHash: 'h1',
+				reason: 'config-updated',
+				config: deepAgentConfig(),
+				skills: deepSkills(),
+			}),
+		},
+	}) as { attributes: Record<string, string> };
+	return span.attributes[GEN_AI_COMPLETION];
+}
+
+type ExportedSnapshot = {
+	agentId: string;
+	configHash: string;
+	config: Omit<ReturnType<typeof deepAgentConfig>, 'credential' | 'tools'> & {
+		credential: string;
+		tools: [{ node: Omit<ReturnType<typeof deepAgentConfig>['tools'][0]['node'], 'credentials'> }];
+	};
+	skills: ReturnType<typeof deepSkills>;
+};
+
+describe('agent-snapshot trace payload fidelity through export scrubbing', () => {
+	it('keeps the config and skill bodies while still scrubbing secrets and credentials', () => {
+		const completion = exportSpan(true);
+		const parsed = jsonParse<ExportedSnapshot>(completion);
+
+		// Consumer keying survives.
+		expect(parsed.agentId).toBe('TrIaGe1234567890');
+		expect(parsed.configHash).toBe('h1');
+
+		// The node tool's parameters survive intact, conditions (depth 9+) included.
+		expect(
+			parsed.config.tools[0].node.nodeParameters.options.filters.conditions[0]?.operator,
+		).toEqual({ type: 'string', operation: 'equals' });
+
+		// Authored prose is NOT scrubbed — a seed carries it, so a case built from
+		// one has to go through the scrub recipe.
+		expect(parsed.config.instructions).toContain('production-down to the ops rota');
+		expect(parsed.skills.skill_triage_rules.instructions).toContain('never downgrade one');
+		expect(parsed.skills.skill_triage_rules.references[0].content).toContain('unusable for');
+
+		// Sensitive-named keys go WHOLESALE, not value-by-value: a consumer gets no
+		// credential id or name back, only the marker.
+		expect(parsed.config.credential).toBe('[redacted]');
+		expect(parsed.config.tools[0].node).not.toHaveProperty('credentials.gmailOAuth2');
+		expect((parsed.config.tools[0].node as { credentials?: unknown }).credentials).toBe(
+			'[redacted]',
+		);
+
+		// Secret patterns still fire inside ordinary prose.
+		expect(parsed.config.instructions).not.toContain('sk-ant-');
+		expect(parsed.config.instructions).toContain('[REDACTED]');
+
+		// No structural placeholders anywhere in the payload.
+		expect(completion).not.toMatch(/\[array\(\d+\)\]|\[object \d+ keys\]|\[redacted-depth-limit\]/);
+	});
+
+	it('keeps the default depth cap without the producer flag — even for a same-named span', () => {
+		// Without the flag the config is destroyed at depth 5, which is the node
+		// tool's parameters: the flag is load-bearing, not decorative.
+		expect(exportSpan(false)).toContain('[redacted-depth-limit]');
+	});
+});
diff --git a/packages/@n8n/instance-ai/src/tracing/agent-snapshot-event.ts b/packages/@n8n/instance-ai/src/tracing/agent-snapshot-event.ts
new file mode 100644
index 00000000000..04706c824fc
--- /dev/null
+++ b/packages/@n8n/instance-ai/src/tracing/agent-snapshot-event.ts
@@ -0,0 +1,105 @@
+/**
+ * Trace-only `agent-snapshot` event — an agent's config + skills at a point in a
+ * conversation, so eval seeding can reconstruct it. Sibling of
+ * `build-workflow`'s `compiled-workflow` event: the agents-module builder is a
+ * separate service, so no tool I/O in the trace carries the config.
+ *
+ * Payload is shaped for `instanceAiEvalSeedAgentSchema` — the consumer maps
+ * `agentId` → `id` and drops the trace-only keys. It carries authored prose that
+ * export scrubbing does NOT remove — scrub anything built from it before it
+ * lands in a case.
+ */
+
+import type { AgentJsonConfig, AgentSkill } from '@n8n/api-types';
+
+import { emitTraceOnlyChildRun } from './langsmith-tracing';
+import { AGENT_SNAPSHOT_TRACE_RUN_NAME } from '../tools/tool-ids';
+import type { InstanceAiTraceContext } from '../types';
+
+/** Matches the compiled-workflow gate: LangSmith rejects an oversized run whole. */
+const MAX_AGENT_SNAPSHOT_TRACE_CHARS = 1_000_000;
+
+/** `attached`/`target-resolved` are BASELINES (state the turn opened on). */
+export type AgentSnapshotReason = 'attached' | 'target-resolved' | 'config-updated';
+
+export interface AgentSnapshotArtifact {
+	config: AgentJsonConfig;
+	skills?: Record<string, AgentSkill>;
+	/** The builder's own hash (`getAgentConfigHash`) — consumers dedupe on it. */
+	configHash?: string | null;
+}
+
+/** Emitted hashes per trace, so two triggers on one turn don't double-emit. */
+const emittedByTrace = new WeakMap<InstanceAiTraceContext, Set<string>>();
+
+/** Emit one snapshot. Best-effort: tracing must never fail a turn. */
+export async function emitAgentSnapshotTraceEvent(
+	tracing: InstanceAiTraceContext | undefined,
+	args: {
+		agentId: string;
+		projectId: string;
+		reason: AgentSnapshotReason;
+		artifact: AgentSnapshotArtifact;
+		logger?: { debug: (message: string) => void };
+	},
+	// `skipped` = the tracing layer exported nothing; `failed` = we threw. Only
+	// the second is our bug.
+): Promise<'emitted' | 'duplicate' | 'skipped' | 'failed'> {
+	const { agentId, projectId, reason, artifact } = args;
+	// Claimed before the emit so two concurrent triggers can't double-write, and
+	// released below unless it landed, so a skip or a throw stays retryable.
+	let claim: { seen: Set<string>; key: string } | undefined;
+	try {
+		const hash = artifact.configHash ?? null;
+		if (tracing && hash) {
+			let seen = emittedByTrace.get(tracing);
+			if (!seen) {
+				seen = new Set();
+				emittedByTrace.set(tracing, seen);
+			}
+			const key = `${agentId}:${hash}`;
+			if (seen.has(key)) return 'duplicate';
+			seen.add(key);
+			claim = { seen, key };
+		}
+
+		const payload = {
+			agentId,
+			projectId,
+			configHash: hash,
+			reason,
+			config: artifact.config,
+			...(artifact.skills ? { skills: artifact.skills } : {}),
+		};
+		const withinSizeGate = JSON.stringify(payload).length <= MAX_AGENT_SNAPSHOT_TRACE_CHARS;
+		const emittedVia = await emitTraceOnlyChildRun(
+			tracing,
+			{
+				name: AGENT_SNAPSHOT_TRACE_RUN_NAME,
+				// 'chain' like the compiled-workflow event: a tool-typed run reads as
+				// a real agent tool call in trace UIs.
+				runType: 'chain',
+				canonicalName: `instance-ai.${AGENT_SNAPSHOT_TRACE_RUN_NAME}`,
+				tags: [AGENT_SNAPSHOT_TRACE_RUN_NAME],
+				metadata: { agent_id: agentId, config_hash: hash, snapshot_reason: reason },
+			},
+			withinSizeGate
+				? { outputs: payload, rawOutputs: true }
+				: { outputs: { agentId, projectId, configHash: hash, reason, truncated: true } },
+		);
+		args.logger?.debug(
+			`[agent-snapshot] ${reason} for ${agentId}: ${emittedVia}${withinSizeGate ? '' : ' (over size gate, emitted truncated marker)'}`,
+		);
+		if (emittedVia === 'skipped') {
+			claim?.seen.delete(claim.key);
+			return 'skipped';
+		}
+		return 'emitted';
+	} catch (error) {
+		claim?.seen.delete(claim.key);
+		args.logger?.debug(
+			`[agent-snapshot] ${reason} for ${agentId} failed: ${error instanceof Error ? error.message : String(error)}`,
+		);
+		return 'failed';
+	}
+}
diff --git a/packages/@n8n/instance-ai/src/types.ts b/packages/@n8n/instance-ai/src/types.ts
index 463209f71f7..ce653e9af0e 100644
--- a/packages/@n8n/instance-ai/src/types.ts
+++ b/packages/@n8n/instance-ai/src/types.ts
@@ -13,6 +13,8 @@ import type {
 	Workspace,
 } from '@n8n/agents';
 import type {
+	AgentJsonConfig,
+	AgentSkill,
 	EvaluationMetric,
 	TaskList,
 	InstanceAiFileAttachment,
@@ -994,6 +996,15 @@ export interface InstanceAiBuilderDelegate {
 	>;
 	/** Current display name of the agent, or undefined when not found. */
 	resolveAgentName(agentId: string): Promise<string | undefined>;
+	/** Config + skills for the `agent-snapshot` trace event; `null` when the agent
+	 *  has no config yet. Optional: the host supplies this delegate across a
+	 *  package boundary, so an unwired host emits no snapshots instead of
+	 *  breaking agent building. */
+	readAgentArtifact?(agentId: string): Promise<{
+		config: AgentJsonConfig;
+		skills: Record<string, AgentSkill>;
+		configHash: string | null;
+	} | null>;
 }
 
 // ── Local gateway status ─────────────────────────────────────────────────────
diff --git a/packages/cli/src/modules/agents/__tests__/instance-ai-builder-delegate.adapter.test.ts b/packages/cli/src/modules/agents/__tests__/instance-ai-builder-delegate.adapter.test.ts
index a75adf15f90..89be4c26121 100644
--- a/packages/cli/src/modules/agents/__tests__/instance-ai-builder-delegate.adapter.test.ts
+++ b/packages/cli/src/modules/agents/__tests__/instance-ai-builder-delegate.adapter.test.ts
@@ -4,11 +4,14 @@ import type {
 	SerializableAgentState,
 	StreamChunk,
 } from '@n8n/agents';
+import type { AgentJsonConfig, AgentSkill } from '@n8n/api-types';
 import type { User } from '@n8n/db';
 import { Like } from '@n8n/typeorm';
+import { UserError } from 'n8n-workflow';
 import { mock } from 'vitest-mock-extended';
 
 import { ForbiddenError } from '@/errors/response-errors/forbidden.error';
+import { NotFoundError } from '@/errors/response-errors/not-found.error';
 import * as checkAccess from '@/permissions.ee/check-access';
 
 import type { AgentsService } from '../agents.service';
@@ -19,6 +22,9 @@ import {
 	INSTANCE_AI_BUILDER_ADDENDUM,
 	InstanceAiBuilderDelegateAdapterService,
 } from '../instance-ai-builder-delegate.adapter';
+import type { AgentConfigService } from '../agent-config.service';
+import { getAgentConfigHash } from '../utils/agent-config-hash';
+import type { AgentSkillsService } from '../agent-skills.service';
 import type { N8nMemory, N8nMemoryImpl } from '../integrations/n8n-memory';
 import type { AgentThreadRepository } from '../repositories/agent-thread.repository';
 
@@ -27,12 +33,16 @@ function setup() {
 	const agentsBuilderService = mock<AgentsBuilderService>();
 	const n8nMemory = mock<N8nMemory>();
 	const agentThreadRepository = mock<AgentThreadRepository>();
+	const agentConfig = mock<AgentConfigService>();
+	const agentSkills = mock<AgentSkillsService>();
 
 	const service = new InstanceAiBuilderDelegateAdapterService(
 		agentsService,
 		agentsBuilderService,
 		n8nMemory,
 		agentThreadRepository,
+		agentConfig,
+		agentSkills,
 	);
 
 	const user = mock<User>({ id: 'user-1' });
@@ -47,6 +57,8 @@ function setup() {
 		agentsBuilderService,
 		n8nMemory,
 		agentThreadRepository,
+		agentConfig,
+		agentSkills,
 		credentialProvider,
 	};
 }
@@ -353,6 +365,54 @@ describe('InstanceAiBuilderDelegateAdapterService', () => {
 		});
 	});
 
+	describe('readAgentArtifact', () => {
+		const CONFIG = { name: 'Support Triage' } as unknown as AgentJsonConfig;
+
+		it('returns the config, the skill bodies, and the builder-s own config hash', async () => {
+			const { delegate, agentConfig, agentSkills } = setup();
+			vi.spyOn(checkAccess, 'userHasScopes').mockResolvedValue(true);
+			agentConfig.getConfig.mockResolvedValue(CONFIG);
+			const skills = { skill_triage_rules: mock<AgentSkill>({ name: 'Triage rules' }) };
+			agentSkills.listSkills.mockResolvedValue(skills);
+
+			const result = await delegate.readAgentArtifact!('agent-1');
+
+			expect(agentConfig.getConfig).toHaveBeenCalledWith('agent-1', 'project-1');
+			expect(agentSkills.listSkills).toHaveBeenCalledWith('agent-1', 'project-1');
+			// The same value read_config hands the model, so a consumer can dedupe on it.
+			expect(result).toEqual({ config: CONFIG, skills, configHash: getAgentConfigHash(CONFIG) });
+		});
+
+		it('returns null for an agent with no config yet, rather than throwing', async () => {
+			// A freshly created agent the builder has not written to: nothing to
+			// snapshot, and not a failure worth surfacing on a build.
+			const { delegate, agentConfig, agentSkills } = setup();
+			vi.spyOn(checkAccess, 'userHasScopes').mockResolvedValue(true);
+			agentConfig.getConfig.mockRejectedValue(new UserError('Agent has no JSON config yet.'));
+
+			await expect(delegate.readAgentArtifact!('agent-1')).resolves.toBeNull();
+			expect(agentSkills.listSkills).not.toHaveBeenCalled();
+		});
+
+		it('propagates a read failure instead of reporting it as no config', async () => {
+			// A missing agent or a dead DB is not "nothing to snapshot" — the callers
+			// treat a throw as no snapshot and log it, so it stays diagnosable.
+			const { delegate, agentConfig } = setup();
+			vi.spyOn(checkAccess, 'userHasScopes').mockResolvedValue(true);
+			agentConfig.getConfig.mockRejectedValue(new NotFoundError('Agent not found'));
+
+			await expect(delegate.readAgentArtifact!('agent-1')).rejects.toThrow('Agent not found');
+		});
+
+		it('rejects when the user lacks agent:read scope', async () => {
+			const { delegate, agentConfig } = setup();
+			vi.spyOn(checkAccess, 'userHasScopes').mockResolvedValue(false);
+
+			await expect(delegate.readAgentArtifact!('agent-1')).rejects.toThrow(ForbiddenError);
+			expect(agentConfig.getConfig).not.toHaveBeenCalled();
+		});
+	});
+
 	describe('createAgent', () => {
 		it('enforces agent:create scope and delegates to AgentsService', async () => {
 			const { delegate, agentsService } = setup();
diff --git a/packages/cli/src/modules/agents/instance-ai-builder-delegate.adapter.ts b/packages/cli/src/modules/agents/instance-ai-builder-delegate.adapter.ts
index 3356a83a2c2..291fb6fa3db 100644
--- a/packages/cli/src/modules/agents/instance-ai-builder-delegate.adapter.ts
+++ b/packages/cli/src/modules/agents/instance-ai-builder-delegate.adapter.ts
@@ -9,15 +9,19 @@ import type {
 } from '@n8n/instance-ai';
 import { type Scope } from '@n8n/permissions';
 import { Like } from '@n8n/typeorm';
+import { UserError } from 'n8n-workflow';
 
 import { ForbiddenError } from '@/errors/response-errors/forbidden.error';
 import { userHasScopes } from '@/permissions.ee/check-access';
 
+import { AgentConfigService } from './agent-config.service';
+import { AgentSkillsService } from './agent-skills.service';
 import { AgentsService } from './agents.service';
 import { AgentsBuilderService } from './builder/agents-builder.service';
 import type { InstanceAiBuilderSessionOptions } from './builder/agents-builder.service';
 import { N8nMemory } from './integrations/n8n-memory';
 import { AgentThreadRepository } from './repositories/agent-thread.repository';
+import { getAgentConfigHash } from './utils/agent-config-hash';
 
 /** Prompt addendum for sub-agent runs; exported for tests. */
 export const INSTANCE_AI_BUILDER_ADDENDUM = `## Instance AI session rules
@@ -78,6 +82,8 @@ export class InstanceAiBuilderDelegateAdapterService {
 		private readonly agentsBuilderService: AgentsBuilderService,
 		private readonly n8nMemory: N8nMemory,
 		private readonly agentThreadRepository: AgentThreadRepository,
+		private readonly agentConfig: AgentConfigService,
+		private readonly agentSkills: AgentSkillsService,
 	) {}
 
 	/** Builder session options for the sub-agent surface: appends the sub-agent prompt rules. */
@@ -181,6 +187,23 @@ export class InstanceAiBuilderDelegateAdapterService {
 				await assertProjectScope('agent:read');
 				return (await this.agentsService.findById(agentId, projectId))?.name;
 			},
+			readAgentArtifact: async (agentId) => {
+				await assertProjectScope('agent:read');
+				// No JSON config yet (freshly created) is an empty snapshot, not an error.
+				// Anything else propagates: the callers already treat a throw as "no
+				// snapshot", and it gets logged there instead of vanishing here.
+				const config = await this.agentConfig.getConfig(agentId, projectId).catch((error) => {
+					if (error instanceof UserError) return null;
+					throw error;
+				});
+				if (!config) return null;
+				return {
+					config,
+					skills: await this.agentSkills.listSkills(agentId, projectId),
+					// The same hash `read_config` hands the model, so consumers can dedupe.
+					configHash: getAgentConfigHash(config),
+				};
+			},
 		};
 	}
 
diff --git a/packages/cli/src/modules/instance-ai/__tests__/instance-ai.service.test.ts b/packages/cli/src/modules/instance-ai/__tests__/instance-ai.service.test.ts
index 228e9fc207d..0a12d98d21d 100644
--- a/packages/cli/src/modules/instance-ai/__tests__/instance-ai.service.test.ts
+++ b/packages/cli/src/modules/instance-ai/__tests__/instance-ai.service.test.ts
@@ -13,6 +13,7 @@ vi.mock('@n8n/instance-ai', async () => {
 			disconnect = vi.fn();
 		},
 		createDomainAccessTracker: vi.fn(),
+		emitAgentSnapshotTraceEvent: vi.fn(async () => await Promise.resolve('emitted')),
 		createSandbox: vi.fn(),
 		createWorkspace: vi.fn(),
 		createLazyRuntimeWorkspace: vi.fn(
@@ -196,6 +197,7 @@ import {
 	resumeAgentRun,
 	setupSandboxWorkspace,
 	shutdownProductTelemetryProviders,
+	emitAgentSnapshotTraceEvent,
 	type BuilderUsageItem,
 	type ManagedBackgroundTask,
 	type InstanceAiTraceContext,
@@ -3926,6 +3928,117 @@ describe('InstanceAiService — editor handoff context resources', () => {
 	});
 });
 
+describe('InstanceAiService — agent snapshots for attached agents', () => {
+	type SnapshotService = {
+		logger: { debug: Mock };
+		snapshotAttachedAgents: (
+			attachments: Array<Record<string, unknown>>,
+			orchestrationContext: Record<string, unknown>,
+			tracing: unknown,
+		) => Promise<void>;
+	};
+
+	const emitSnapshot = emitAgentSnapshotTraceEvent as unknown as Mock;
+	const TRACING = { actorRun: { id: 'actor-1' } };
+	const ARTIFACT = { config: { name: 'Support Triage' }, skills: {}, configHash: 'hash-1' };
+
+	function createService(): SnapshotService {
+		const service = Object.create(InstanceAiService.prototype) as unknown as SnapshotService;
+		service.logger = { debug: vi.fn() };
+		return service;
+	}
+
+	function makeContext(readAgentArtifact?: Mock) {
+		return {
+			domainContext: readAgentArtifact ? { builderDelegate: { readAgentArtifact } } : {},
+		};
+	}
+
+	beforeEach(() => emitSnapshot.mockClear());
+
+	it('snapshots an attached agent as it stood when the turn opened', async () => {
+		const service = createService();
+		const readAgentArtifact = vi.fn(async () => await Promise.resolve(ARTIFACT));
+
+		await service.snapshotAttachedAgents(
+			[{ type: 'agent', id: 'agent-1', projectId: 'proj-1' }],
+			makeContext(readAgentArtifact),
+			TRACING,
+		);
+
+		expect(readAgentArtifact).toHaveBeenCalledWith('agent-1');
+		expect(emitSnapshot).toHaveBeenCalledTimes(1);
+		expect(emitSnapshot.mock.calls[0][1]).toMatchObject({
+			agentId: 'agent-1',
+			projectId: 'proj-1',
+			reason: 'attached',
+			artifact: ARTIFACT,
+		});
+	});
+
+	it('ignores a workflow attachment — the workflow side has its own event', async () => {
+		const service = createService();
+		const readAgentArtifact = vi.fn();
+
+		await service.snapshotAttachedAgents(
+			[{ type: 'workflow', id: 'wf-1' }],
+			makeContext(readAgentArtifact),
+			TRACING,
+		);
+
+		expect(readAgentArtifact).not.toHaveBeenCalled();
+		expect(emitSnapshot).not.toHaveBeenCalled();
+	});
+
+	it('does nothing when the agents module is off, rather than failing the turn', async () => {
+		const service = createService();
+
+		await expect(
+			service.snapshotAttachedAgents(
+				[{ type: 'agent', id: 'agent-1', projectId: 'proj-1' }],
+				makeContext(undefined),
+				TRACING,
+			),
+		).resolves.toBeUndefined();
+		expect(emitSnapshot).not.toHaveBeenCalled();
+	});
+
+	it('does nothing without a trace to attach the event to', async () => {
+		const service = createService();
+		const readAgentArtifact = vi.fn();
+
+		await service.snapshotAttachedAgents(
+			[{ type: 'agent', id: 'agent-1', projectId: 'proj-1' }],
+			makeContext(readAgentArtifact),
+			undefined,
+		);
+
+		expect(readAgentArtifact).not.toHaveBeenCalled();
+		expect(emitSnapshot).not.toHaveBeenCalled();
+	});
+
+	it('skips an agent it cannot read and keeps going', async () => {
+		const service = createService();
+		const readAgentArtifact = vi.fn(async (agentId: string) =>
+			agentId === 'agent-broken'
+				? await Promise.reject(new Error('gone'))
+				: await Promise.resolve(ARTIFACT),
+		);
+
+		await service.snapshotAttachedAgents(
+			[
+				{ type: 'agent', id: 'agent-broken', projectId: 'proj-1' },
+				{ type: 'agent', id: 'agent-ok', projectId: 'proj-1' },
+			],
+			makeContext(readAgentArtifact),
+			TRACING,
+		);
+
+		expect(emitSnapshot).toHaveBeenCalledTimes(1);
+		expect(emitSnapshot.mock.calls[0][1]).toMatchObject({ agentId: 'agent-ok' });
+	});
+});
+
 describe('InstanceAiService — workflow verification follow-up gate', () => {
 	type VerificationGateService = {
 		workflowObligations: { getObligation: Mock };
diff --git a/packages/cli/src/modules/instance-ai/instance-ai.service.ts b/packages/cli/src/modules/instance-ai/instance-ai.service.ts
index 78644c01e74..e0e359f9494 100644
--- a/packages/cli/src/modules/instance-ai/instance-ai.service.ts
+++ b/packages/cli/src/modules/instance-ai/instance-ai.service.ts
@@ -39,6 +39,7 @@ import {
 	disabledInstanceAiSkillIds,
 	createInstanceAiTraceContext,
 	createInternalOperationTraceContext,
+	emitAgentSnapshotTraceEvent,
 	createInstanceAiLivenessPolicyConfig,
 	InstanceAiLivenessPolicy,
 	McpClientManager,
@@ -77,6 +78,7 @@ import {
 	type ManagedBackgroundTask,
 	type McpServerConfig,
 	type ModelConfig,
+	type AgentSnapshotArtifact,
 	type OrchestrationContext,
 	type InstanceAiTraceContext,
 	type PlannedTaskGraph,
@@ -3499,6 +3501,10 @@ export class InstanceAiService {
 				}
 			}
 
+			// The builder never sees an attach-only turn, so nothing else records what
+			// the attached agent looked like when the conversation opened.
+			await this.snapshotAttachedAgents(contextAttachments, orchestrationContext, tracing);
+
 			const enrichedMessage = await this.buildMessageWithRunningTasks(threadId, message);
 			const contextResourcesBlock = buildContextResourcesBlock(contextAttachments);
 
@@ -5726,6 +5732,37 @@ export class InstanceAiService {
 		return { status: 'limit-reached' };
 	}
 
+	/** Snapshot every Agent the editor attached, as it stands before this turn
+	 *  acts on it. Best-effort: it only feeds eval-seed authoring. */
+	private async snapshotAttachedAgents(
+		attachments: InstanceAiResourceAttachment[],
+		orchestrationContext: OrchestrationContext,
+		tracing: InstanceAiTraceContext | undefined,
+	): Promise<void> {
+		const delegate = orchestrationContext.domainContext?.builderDelegate;
+		if (!delegate || !tracing) return;
+		for (const attachment of attachments) {
+			if (attachment.type !== 'agent') continue;
+			let artifact: AgentSnapshotArtifact | null = null;
+			try {
+				artifact = (await delegate.readAgentArtifact?.(attachment.id)) ?? null;
+			} catch (error) {
+				this.logger.debug(
+					`[agent-snapshot] attached read for ${attachment.id} failed: ${error instanceof Error ? error.message : String(error)}`,
+				);
+				continue;
+			}
+			if (!artifact) continue;
+			await emitAgentSnapshotTraceEvent(tracing, {
+				agentId: attachment.id,
+				projectId: attachment.projectId,
+				reason: 'attached',
+				artifact,
+				logger: this.logger,
+			});
+		}
+	}
+
 	private async buildMessageWithRunningTasks(threadId: string, message: string): Promise<string> {
 		return await enrichMessageWithBackgroundTasks(
 			message,