db: agent enrollment schema (M4-4a, migration 0021)

Additive-only DDL per the merged design (docs/plans/
2026-08-29-agent-enrollment-command-design.md SS4): agents gains
nullable harness + enrolled_at (no backfill); new agent_audit_events
(append-only, seq identity, FK-free agent linkage, causation self-FK,
closed event-type CHECK), agent_outbox (hierarchy shape, one row per
event, closed status enum), agent_idempotency_fence (contract 3 SS4.3
shape: UNIQUE (operation, key), replay-mode CHECK, FK-free outcome
reference).

Schema-level witnesses in agent-enrollment.witness.test.ts (PGlite +
real-PostgreSQL legs): nullable enrollment columns, event-type CHECK,
per-agent seq ordering, deletion-safe linkage (events and fence rows
survive agent deletion; information_schema FK probes), causation and
outbox RESTRICT, fence uniqueness and mode CHECK. Command-level
witnesses land with M4-4b.

packages/db/drizzle/0021_agent_enrollment.sql

@@ -0,0 +1,47 @@
+CREATE TYPE "public"."agent_outbox_status" AS ENUM('pending', 'processing', 'delivered');--> statement-breakpoint
+CREATE TABLE "agent_audit_events" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"seq" bigint GENERATED ALWAYS AS IDENTITY (sequence name "agent_audit_events_seq_seq" INCREMENT BY 1 MINVALUE 1 MAXVALUE 9223372036854775807 START WITH 1 CACHE 1),
+	"event_type" text NOT NULL,
+	"actor_id" text NOT NULL,
+	"agent_id" uuid NOT NULL,
+	"correlation_id" text NOT NULL,
+	"causation_id" uuid,
+	"payload" jsonb NOT NULL,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	CONSTRAINT "agent_audit_events_type_check" CHECK (event_type IN ('agent.enrolled', 'agent.enrollment.replayed'))
+);
+--> statement-breakpoint
+CREATE TABLE "agent_idempotency_fence" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"operation" text NOT NULL,
+	"idempotency_key" text NOT NULL,
+	"actor_id" text NOT NULL,
+	"authorization_scope" text NOT NULL,
+	"payload_digest" text NOT NULL,
+	"replay_mode" text DEFAULT 'actor-bound' NOT NULL,
+	"outcome_agent_id" uuid NOT NULL,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	CONSTRAINT "agent_idempotency_fence_replay_mode_check" CHECK (replay_mode IN ('actor-bound', 'shared'))
+);
+--> statement-breakpoint
+CREATE TABLE "agent_outbox" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"event_id" uuid NOT NULL,
+	"correlation_id" text NOT NULL,
+	"status" "agent_outbox_status" DEFAULT 'pending' NOT NULL,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"updated_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"delivered_at" timestamp with time zone
+);
+--> statement-breakpoint
+ALTER TABLE "agents" ADD COLUMN "harness" text;--> statement-breakpoint
+ALTER TABLE "agents" ADD COLUMN "enrolled_at" timestamp with time zone;--> statement-breakpoint
+ALTER TABLE "agent_audit_events" ADD CONSTRAINT "agent_audit_events_causation_id_agent_audit_events_id_fk" FOREIGN KEY ("causation_id") REFERENCES "public"."agent_audit_events"("id") ON DELETE restrict ON UPDATE no action;--> statement-breakpoint
+ALTER TABLE "agent_outbox" ADD CONSTRAINT "agent_outbox_event_id_agent_audit_events_id_fk" FOREIGN KEY ("event_id") REFERENCES "public"."agent_audit_events"("id") ON DELETE restrict ON UPDATE no action;--> statement-breakpoint
+CREATE UNIQUE INDEX "agent_audit_events_seq_idx" ON "agent_audit_events" USING btree ("seq");--> statement-breakpoint
+CREATE INDEX "agent_audit_events_agent_seq_idx" ON "agent_audit_events" USING btree ("agent_id","seq");--> statement-breakpoint
+CREATE INDEX "agent_audit_events_correlation_idx" ON "agent_audit_events" USING btree ("correlation_id");--> statement-breakpoint
+CREATE UNIQUE INDEX "agent_idempotency_fence_operation_key_idx" ON "agent_idempotency_fence" USING btree ("operation","idempotency_key");--> statement-breakpoint
+CREATE UNIQUE INDEX "agent_outbox_event_idx" ON "agent_outbox" USING btree ("event_id");--> statement-breakpoint
+CREATE INDEX "agent_outbox_status_created_idx" ON "agent_outbox" USING btree ("status","created_at");

packages/db/drizzle/meta/_journal.json

@@ -148,6 +148,13 @@
       "when": 1787963521142,
       "tag": "0020_special_betty_brant",
       "breakpoints": true
+    },
+    {
+      "idx": 21,
+      "version": "7",
+      "when": 1788053011351,
+      "tag": "0021_agent_enrollment",
+      "breakpoints": true
     }
   ]
 }

packages/db/src/agent-enrollment.witness.test.ts

@@ -0,0 +1,412 @@
+/**
+ * Agent enrollment schema witnesses — M4-4a, the schema-level half of the
+ * witness list in docs/plans/2026-08-29-agent-enrollment-command-design.md §5.
+ *
+ * Witnesses the guarantees migration 0021's tables themselves carry: the
+ * event-type CHECK, monotonic per-agent append order (`seq`), deletion-safe
+ * linkage (no foreign key from the events or fence tables into `agents` —
+ * rows survive a legacy CRUD DELETE of the agent), the causation self-FK,
+ * the outbox's FK/uniqueness/status shape, the fence's UNIQUE
+ * (operation, key) and replay-mode CHECK, and the nullable enrollment
+ * columns on `agents` (legacy rows insert without them). The command-level
+ * witnesses (never-echo, same-tx atomicity, replay semantics, correlation,
+ * CLI parity, fail-closed) belong to the M4-4b implementation slice.
+ *
+ * Two legs run the same witness body:
+ *  - PGlite (WASM Postgres): always runs.
+ *  - Real PostgreSQL: runs when DATABASE_URL is set — the binding witness;
+ *    CI migrates ci-postgres before `pnpm test`.
+ */
+import { randomUUID } from 'node:crypto';
+import { mkdtempSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { sql } from 'drizzle-orm';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { createDb } from './client.js';
+import { createPgliteDb } from './client-pglite.js';
+import { runPgliteMigrations } from './migrate.js';
+import { agentAuditEvents, agentIdempotencyFence, agentOutbox, agents } from './schema.js';
+
+type AnyDb = {
+  db: {
+    insert: (t: unknown) => { values: (v: unknown) => Promise<unknown> };
+    execute: (q: unknown) => Promise<{ rows?: unknown[] } | unknown[]>;
+  };
+  close: () => Promise<void>;
+};
+
+/** Match a constraint failure anywhere along drizzle's cause chain. */
+async function expectViolation(p: Promise<unknown>, re: RegExp, label = ''): Promise<void> {
+  let err: unknown;
+  try {
+    await p;
+  } catch (e) {
+    err = e;
+  }
+  expect(err, label || 'expected the statement to be refused').toBeDefined();
+  const messages: string[] = [];
+  let cur: unknown = err;
+  while (cur instanceof Error) {
+    messages.push(cur.message);
+    cur = (cur as { cause?: unknown }).cause;
+  }
+  expect(messages.join(' | '), label).toMatch(re);
+}
+
+function rows(res: { rows?: unknown[] } | unknown[]): Record<string, unknown>[] {
+  return (Array.isArray(res) ? res : (res.rows ?? [])) as Record<string, unknown>[];
+}
+
+/** Unique per-run prefix so real-PG runs never collide and clean up safely. */
+const T = `agent-e-${randomUUID().slice(0, 8)}`;
+
+type EventInsert = typeof agentAuditEvents.$inferInsert;
+
+function eventRow(overrides: Partial<EventInsert> = {}): EventInsert {
+  return {
+    eventType: 'agent.enrolled',
+    actorId: `${T}-actor`,
+    agentId: randomUUID(),
+    correlationId: `${T}-corr-${randomUUID()}`,
+    payload: {
+      harness: 'claude-code',
+      provider: 'anthropic',
+      name: 'x',
+      credentialMode: 'reference',
+    },
+    ...overrides,
+  };
+}
+
+type FenceInsert = typeof agentIdempotencyFence.$inferInsert;
+
+function fenceRow(overrides: Partial<FenceInsert> = {}): FenceInsert {
+  return {
+    operation: 'agent.enroll',
+    idempotencyKey: `${T}-${randomUUID()}`,
+    actorId: `${T}-actor`,
+    authorizationScope: 'platform-user',
+    payloadDigest: `${T}-digest`,
+    outcomeAgentId: randomUUID(),
+    ...overrides,
+  };
+}
+
+function witnessSuite(getHandle: () => AnyDb): void {
+  const db = () => getHandle().db as unknown as ReturnType<typeof createDb>['db'];
+
+  afterAll(async () => {
+    const d = db();
+    await d.execute(sql`DELETE FROM agent_outbox WHERE correlation_id LIKE ${T + '%'}`);
+    // Caused events first: the causation self-FK is RESTRICT.
+    await d.execute(
+      sql`DELETE FROM agent_audit_events WHERE correlation_id LIKE ${T + '%'} AND causation_id IS NOT NULL`,
+    );
+    await d.execute(sql`DELETE FROM agent_audit_events WHERE correlation_id LIKE ${T + '%'}`);
+    await d.execute(sql`DELETE FROM agent_idempotency_fence WHERE actor_id LIKE ${T + '%'}`);
+    await d.execute(sql`DELETE FROM agents WHERE name LIKE ${T + '%'}`);
+  });
+
+  // ── agents: nullable enrollment columns (no backfill semantics) ────────────
+
+  it('legacy agent rows insert without enrollment columns; enrolled rows carry both', async () => {
+    const legacyId = randomUUID();
+    await db()
+      .insert(agents)
+      .values({
+        id: legacyId,
+        name: `${T}-legacy`,
+        provider: 'anthropic',
+        model: 'claude-fable-5',
+      });
+    const legacy = rows(
+      await db().execute(sql`SELECT harness, enrolled_at FROM agents WHERE id = ${legacyId}`),
+    )[0]!;
+    expect(legacy['harness']).toBeNull();
+    expect(legacy['enrolled_at']).toBeNull();
+
+    const enrolledId = randomUUID();
+    await db()
+      .insert(agents)
+      .values({
+        id: enrolledId,
+        name: `${T}-enrolled`,
+        provider: 'anthropic',
+        model: 'claude-fable-5',
+        harness: 'claude-code',
+        enrolledAt: new Date(),
+      });
+    const enrolled = rows(
+      await db().execute(sql`SELECT harness, enrolled_at FROM agents WHERE id = ${enrolledId}`),
+    )[0]!;
+    expect(enrolled['harness']).toBe('claude-code');
+    expect(enrolled['enrolled_at']).not.toBeNull();
+  });
+
+  // ── agent_audit_events: CHECK, ordering, deletion-safe linkage ─────────────
+
+  it('accepts both declared event types and refuses an undeclared one', async () => {
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ eventType: 'agent.enrolled' }));
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ eventType: 'agent.enrollment.replayed' }));
+    await expectViolation(
+      db()
+        .insert(agentAuditEvents)
+        .values(eventRow({ eventType: 'agent.deleted' })),
+      /type_check|violates check/i,
+      'undeclared event type must be refused',
+    );
+  });
+
+  it('assigns strictly increasing seq in insert order for one agent', async () => {
+    const agentId = randomUUID();
+    const c1 = `${T}-seq-1-${randomUUID()}`;
+    const c2 = `${T}-seq-2-${randomUUID()}`;
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ agentId, correlationId: c1 }));
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ agentId, eventType: 'agent.enrollment.replayed', correlationId: c2 }));
+    const res = rows(
+      await db().execute(
+        sql`SELECT correlation_id, seq FROM agent_audit_events WHERE agent_id = ${agentId} ORDER BY seq ASC`,
+      ),
+    );
+    expect(res.map((r) => r['correlation_id'])).toEqual([c1, c2]);
+    expect(Number(res[1]!['seq'])).toBeGreaterThan(Number(res[0]!['seq']));
+  });
+
+  it('has no foreign key into agents, and events survive agent deletion', async () => {
+    const fks = rows(
+      await db().execute(sql`
+        SELECT ccu.table_name AS referenced_table
+        FROM information_schema.table_constraints tc
+        JOIN information_schema.constraint_column_usage ccu
+          ON ccu.constraint_name = tc.constraint_name AND ccu.constraint_schema = tc.constraint_schema
+        WHERE tc.constraint_type = 'FOREIGN KEY' AND tc.table_name = 'agent_audit_events'
+      `),
+    );
+    // The causation self-FK is the ONLY foreign key on the events table.
+    expect([...new Set(fks.map((r) => r['referenced_table']))]).toEqual(['agent_audit_events']);
+
+    const agentId = randomUUID();
+    await db()
+      .insert(agents)
+      .values({ id: agentId, name: `${T}-doomed`, provider: 'anthropic', model: 'claude-fable-5' });
+    const corr = `${T}-survive-${randomUUID()}`;
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ agentId, correlationId: corr }));
+    await db().execute(sql`DELETE FROM agents WHERE id = ${agentId}`);
+    const after = rows(
+      await db().execute(
+        sql`SELECT agent_id FROM agent_audit_events WHERE correlation_id = ${corr}`,
+      ),
+    );
+    expect(after).toHaveLength(1);
+    expect(after[0]!['agent_id']).toBe(agentId);
+  });
+
+  it('enforces the causation self-FK and RESTRICTs deleting a cause', async () => {
+    await expectViolation(
+      db()
+        .insert(agentAuditEvents)
+        .values(eventRow({ causationId: randomUUID() })),
+      /foreign key/i,
+      'causation must reference an existing event',
+    );
+    const causeCorr = `${T}-cause-${randomUUID()}`;
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ correlationId: causeCorr }));
+    const cause = rows(
+      await db().execute(
+        sql`SELECT id FROM agent_audit_events WHERE correlation_id = ${causeCorr}`,
+      ),
+    )[0]!;
+    await db()
+      .insert(agentAuditEvents)
+      .values(
+        eventRow({
+          eventType: 'agent.enrollment.replayed',
+          causationId: cause['id'] as string,
+        }),
+      );
+    await expectViolation(
+      db().execute(sql`DELETE FROM agent_audit_events WHERE id = ${cause['id'] as string}`),
+      /foreign key/i,
+      'a cause with dependent events must not be deletable',
+    );
+  });
+
+  // ── agent_outbox shape ─────────────────────────────────────────────────────
+
+  it('outbox rows require an existing event, one outbox row per event, closed status enum', async () => {
+    await expectViolation(
+      db()
+        .insert(agentOutbox)
+        .values({ eventId: randomUUID(), correlationId: `${T}-corr` }),
+      /foreign key/i,
+      'outbox must reference an existing event',
+    );
+    const corr = `${T}-ob-${randomUUID()}`;
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ correlationId: corr }));
+    const event = rows(
+      await db().execute(sql`SELECT id FROM agent_audit_events WHERE correlation_id = ${corr}`),
+    )[0]!;
+    const eventId = event['id'] as string;
+    await db().insert(agentOutbox).values({ eventId, correlationId: corr });
+    await expectViolation(
+      db()
+        .insert(agentOutbox)
+        .values({ eventId, correlationId: `${T}-ob2` }),
+      /duplicate key|unique/i,
+      'one outbox record per event',
+    );
+    await expectViolation(
+      db().execute(
+        sql`INSERT INTO agent_outbox (event_id, correlation_id, status)
+            VALUES (${eventId}, ${`${T}-ob3`}, 'failed')`,
+      ),
+      /invalid input value for enum|22P02/i,
+      'status outside pending/processing/delivered must be refused',
+    );
+  });
+
+  it('outbox FK RESTRICTs event deletion while the outbox row exists', async () => {
+    const corr = `${T}-obr-${randomUUID()}`;
+    await db()
+      .insert(agentAuditEvents)
+      .values(eventRow({ correlationId: corr }));
+    const event = rows(
+      await db().execute(sql`SELECT id FROM agent_audit_events WHERE correlation_id = ${corr}`),
+    )[0]!;
+    await db()
+      .insert(agentOutbox)
+      .values({ eventId: event['id'] as string, correlationId: corr });
+    await expectViolation(
+      db().execute(sql`DELETE FROM agent_audit_events WHERE id = ${event['id'] as string}`),
+      /foreign key/i,
+    );
+  });
+
+  // ── agent_idempotency_fence: (operation, key) uniqueness, mode CHECK ───────
+
+  it('refuses a duplicate (operation, key) pair but allows the same key under another operation', async () => {
+    const key = `${T}-fence-${randomUUID()}`;
+    await db()
+      .insert(agentIdempotencyFence)
+      .values(fenceRow({ idempotencyKey: key }));
+    await expectViolation(
+      db()
+        .insert(agentIdempotencyFence)
+        .values(fenceRow({ idempotencyKey: key })),
+      /duplicate key|unique/i,
+      'fence uniqueness is (operation, key)',
+    );
+    // Same key, different operation identifier: a distinct fence.
+    await db()
+      .insert(agentIdempotencyFence)
+      .values(fenceRow({ idempotencyKey: key, operation: 'agent.other' }));
+  });
+
+  it('defaults replay mode to actor-bound and refuses an undeclared mode', async () => {
+    const key = `${T}-mode-${randomUUID()}`;
+    await db()
+      .insert(agentIdempotencyFence)
+      .values(fenceRow({ idempotencyKey: key }));
+    const row = rows(
+      await db().execute(
+        sql`SELECT replay_mode FROM agent_idempotency_fence WHERE idempotency_key = ${key}`,
+      ),
+    )[0]!;
+    expect(row['replay_mode']).toBe('actor-bound');
+    await expectViolation(
+      db()
+        .insert(agentIdempotencyFence)
+        .values(fenceRow({ replayMode: 'unbound' as 'actor-bound' })),
+      /replay_mode_check|violates check/i,
+      'a mode outside actor-bound/shared must be refused',
+    );
+  });
+
+  it('fence has no foreign key at all, and rows survive agent deletion', async () => {
+    const fks = rows(
+      await db().execute(sql`
+        SELECT ccu.table_name AS referenced_table
+        FROM information_schema.table_constraints tc
+        JOIN information_schema.constraint_column_usage ccu
+          ON ccu.constraint_name = tc.constraint_name AND ccu.constraint_schema = tc.constraint_schema
+        WHERE tc.constraint_type = 'FOREIGN KEY' AND tc.table_name = 'agent_idempotency_fence'
+      `),
+    );
+    expect(fks).toHaveLength(0);
+
+    const agentId = randomUUID();
+    await db()
+      .insert(agents)
+      .values({
+        id: agentId,
+        name: `${T}-fdoomed`,
+        provider: 'anthropic',
+        model: 'claude-fable-5',
+      });
+    const key = `${T}-fsurvive-${randomUUID()}`;
+    await db()
+      .insert(agentIdempotencyFence)
+      .values(fenceRow({ idempotencyKey: key, outcomeAgentId: agentId }));
+    await db().execute(sql`DELETE FROM agents WHERE id = ${agentId}`);
+    const after = rows(
+      await db().execute(
+        sql`SELECT outcome_agent_id FROM agent_idempotency_fence WHERE idempotency_key = ${key}`,
+      ),
+    );
+    expect(after).toHaveLength(1);
+    expect(after[0]!['outcome_agent_id']).toBe(agentId);
+  });
+}
+
+// ── Leg 1: PGlite (always runs — local witness signal) ───────────────────────
+
+describe('agent enrollment schema witnesses — PGlite', () => {
+  let dir: string;
+  let handle: ReturnType<typeof createPgliteDb>;
+
+  beforeAll(async () => {
+    dir = mkdtempSync(join(tmpdir(), 'agent-enroll-witness-'));
+    handle = createPgliteDb(dir);
+    await runPgliteMigrations(handle);
+  });
+
+  afterAll(async () => {
+    await handle.close();
+    rmSync(dir, { recursive: true, force: true });
+  });
+
+  witnessSuite(() => handle as unknown as AnyDb);
+});
+
+// ── Leg 2: real PostgreSQL (binding witness, ci-postgres in CI) ──────────────
+
+const hasPostgres = Boolean(process.env['DATABASE_URL']);
+
+describe.skipIf(!hasPostgres)('agent enrollment schema witnesses — real PostgreSQL', () => {
+  let handle: ReturnType<typeof createDb>;
+
+  beforeAll(() => {
+    handle = createDb(process.env['DATABASE_URL']!);
+  });
+
+  afterAll(async () => {
+    await handle.close();
+  });
+
+  witnessSuite(() => handle as unknown as AnyDb);
+});

packages/db/src/schema.ts

@@ -302,6 +302,11 @@ export const agents = pgTable(
     skills: jsonb('skills').$type<string[]>(),
     isSystem: boolean('is_system').notNull().default(false),
     config: jsonb('config'),
+    // Enrollment (M4-4, docs/plans/2026-08-29-agent-enrollment-command-design.md §4).
+    // NULL on both marks a legacy (non-enrolled) row; no backfill — enrollment
+    // is a fact the rank-4 command creates, not one to invent for existing rows.
+    harness: text('harness'),
+    enrolledAt: timestamp('enrolled_at', { withTimezone: true }),
     createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
     updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
   },
@@ -1279,3 +1284,109 @@ export const hierarchyOutbox = pgTable(
     index('hierarchy_outbox_status_created_idx').on(t.status, t.createdAt),
   ],
 );
+
+// ---------------------------------------------------------------------------
+// Agent enrollment (M4-4) — rank-4 command family audit/outbox/fence stores.
+// Design: docs/plans/2026-08-29-agent-enrollment-command-design.md §4.
+// Pattern reuse from the hierarchy audit/outbox pair, separate store. Audit
+// rows reference the agent by snapshot id, deliberately with NO FK, so audit
+// history survives agent deletion through the legacy CRUD DELETE path.
+// Idempotency for this family lives in agent_idempotency_fence (contract 3
+// §4.3 envelope, ratified into contract 5 §4 via contract 3 §7 item 4) — the
+// audit and outbox tables carry no idempotency key of their own.
+
+export const AGENT_AUDIT_EVENT_TYPES = [
+  // Semantic mutation event of agent.enroll.
+  'agent.enrolled',
+  // Non-mutation access class: a passing idempotent replay appends this and
+  // nothing else (accessing principal, current correlation id, fence-row
+  // reference in the payload).
+  'agent.enrollment.replayed',
+] as const;
+
+export const agentAuditEvents = pgTable(
+  'agent_audit_events',
+  {
+    id: uuid('id').primaryKey().defaultRandom(),
+    // Global append order; per-agent ordering is a filter on agent_id ordered
+    // by seq.
+    seq: bigint('seq', { mode: 'number' }).notNull().generatedAlwaysAsIdentity(),
+    eventType: text('event_type').notNull(),
+    // No FK: audit events outlive every principal and every target.
+    actorId: text('actor_id').notNull(),
+    agentId: uuid('agent_id').notNull(),
+    correlationId: text('correlation_id').notNull(),
+    causationId: uuid('causation_id').references((): AnyPgColumn => agentAuditEvents.id, {
+      onDelete: 'restrict',
+    }),
+    // Immutable snapshot at event time; never carries credential material
+    // (§3.1 rule 1: actor, agent id, harness, provider, name, credentialMode).
+    payload: jsonb('payload').notNull(),
+    createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  },
+  (t) => [
+    uniqueIndex('agent_audit_events_seq_idx').on(t.seq),
+    index('agent_audit_events_agent_seq_idx').on(t.agentId, t.seq),
+    index('agent_audit_events_correlation_idx').on(t.correlationId),
+    check(
+      'agent_audit_events_type_check',
+      sql`event_type IN ('agent.enrolled', 'agent.enrollment.replayed')`,
+    ),
+  ],
+);
+
+export const agentOutboxStatusEnum = pgEnum('agent_outbox_status', [
+  'pending',
+  'processing',
+  'delivered',
+]);
+
+export const agentOutbox = pgTable(
+  'agent_outbox',
+  {
+    id: uuid('id').primaryKey().defaultRandom(),
+    // FK into the append-only events table: never dangles, RESTRICT is safe.
+    eventId: uuid('event_id')
+      .notNull()
+      .references(() => agentAuditEvents.id, { onDelete: 'restrict' }),
+    correlationId: text('correlation_id').notNull(),
+    status: agentOutboxStatusEnum('status').notNull().default('pending'),
+    createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+    updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+    deliveredAt: timestamp('delivered_at', { withTimezone: true }),
+  },
+  (t) => [
+    uniqueIndex('agent_outbox_event_idx').on(t.eventId),
+    index('agent_outbox_status_created_idx').on(t.status, t.createdAt),
+  ],
+);
+
+// Contract 3 §4.3 fence shape. Uniqueness is (operation, key); the recorded
+// replay mode is always 'actor-bound' for this family (`shared` is seed-only
+// and refused at validation — design §3.1), but the column keeps the ratified
+// envelope shape and serves the mode-mismatch collision check. The payload
+// digest input EXCLUDES the credential value (design §3.1 rule 5).
+export const agentIdempotencyFence = pgTable(
+  'agent_idempotency_fence',
+  {
+    id: uuid('id').primaryKey().defaultRandom(),
+    operation: text('operation').notNull(),
+    idempotencyKey: text('idempotency_key').notNull(),
+    // No FK: fence rows outlive principals, mirroring the audit tables.
+    actorId: text('actor_id').notNull(),
+    authorizationScope: text('authorization_scope').notNull(),
+    payloadDigest: text('payload_digest').notNull(),
+    replayMode: text('replay_mode').notNull().default('actor-bound'),
+    // Committed-outcome reference (the enrolled agent's id). Snapshot value,
+    // no FK: the fence must keep answering replays after a legacy DELETE.
+    outcomeAgentId: uuid('outcome_agent_id').notNull(),
+    createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  },
+  (t) => [
+    uniqueIndex('agent_idempotency_fence_operation_key_idx').on(t.operation, t.idempotencyKey),
+    check(
+      'agent_idempotency_fence_replay_mode_check',
+      sql`replay_mode IN ('actor-bound', 'shared')`,
+    ),
+  ],
+);