diff --git a/prisma/migrations/0297_managed_profile/migration.sql b/prisma/migrations/0297_managed_profile/migration.sql
index d7d309e46..83b0a252e 100644
--- a/prisma/migrations/0297_managed_profile/migration.sql
+++ b/prisma/migrations/0297_managed_profile/migration.sql
@@ -16,11 +16,10 @@
 --
 -- A timestamp rather than a boolean, deliberately. It says since when, which
 -- the activity trail needs to be readable across the transition, and clearing
--- it is the emancipation act: the day the person takes the record over,
--- credentials attach (`email` and `password_hash` are already nullable, so
--- nothing here has to change for that) and this goes back to NULL. The grants
--- survive untouched — the handover changes who holds the revoke button, not
--- which rows exist.
+-- it leaves a future-compatible NULL state. This migration deliberately adds
+-- no transition route or credential attachment flow. If a later handover is
+-- designed, `email` and `password_hash` are already nullable and the grants
+-- can survive untouched while the product defines who holds the revoke button.
 --
 -- No index. The column is read by primary key, on a row the request already
 -- loaded, and the one enumeration that scans for marked rows (the reminder
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index 651897559..457e3a151 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -62,16 +62,16 @@ model User {
   /// former and stay shut for the latter, and the gate is this column rather
   /// than the grant, so no argument about a grant level can reach them.
   ///
-  /// A timestamp rather than a boolean, for a reason the schema has to keep
-  /// possible: it says since when, and clearing it is the emancipation act —
-  /// the day the person takes their own record over, credentials attach and
-  /// this goes back to NULL, with the grants and the whole activity trail
-  /// spanning the transition untouched.
+  /// A timestamp rather than a boolean: it says since when, and preserves a
+  /// future-compatible null state without adding a transition surface here.
+  /// This release does not expose a way to clear the marker or attach
+  /// credentials; the grants and activity trail remain intact if a later,
+  /// separately designed handover ever needs that state.
   ///
   /// Consumers land in this release: the guardian resolver in
-  /// `src/lib/api-handler.ts` reads it on every guardian request, the
-  /// notification dispatcher fans reminders out to the guardians' channels on
-  /// it, and the creation flow is what writes it.
+  /// `src/lib/api-handler.ts` reads it on every guardian request, and the
+  /// creation flow is what writes it. A later notification plan may add
+  /// delivery fanout after it defines consent and preference semantics.
   managedProfileAt DateTime? @map("managed_profile_at")
 
   // Profile
@@ -6036,7 +6036,10 @@ model AccountGrant {
   revokedBy AccountGrantRevoker? @map("revoked_by")
 
   /// Optional lapse date. Checked live on every resolution, so an expired
-  /// grant stops conferring access without anything having to sweep it.
+  /// grant stops conferring access without anything having to sweep it. A
+  /// managed-profile invitation may carry an expiry while awaiting consent;
+  /// accepting its MANAGE grant clears this field because an active Guardian
+  /// ends only through an explicit lifecycle transition.
   expiresAt  DateTime? @map("expires_at")
   /// Refreshed fire-and-forget when the grant is exercised, the same posture
   /// as `ApiToken.lastUsedAt`. The owner's panel reads it to answer "is this
diff --git a/src/__tests__/managed-profile-contract.test.ts b/src/__tests__/managed-profile-contract.test.ts
new file mode 100644
index 000000000..aff12b1ea
--- /dev/null
+++ b/src/__tests__/managed-profile-contract.test.ts
@@ -0,0 +1,75 @@
+import { readFile, readdir } from "node:fs/promises";
+import path from "node:path";
+import { describe, expect, it } from "vitest";
+
+const root = process.cwd();
+
+describe("managed-profile contract", () => {
+  it("requires a cookie-backed fresh MFA proof for creation", async () => {
+    const source = await readFile(
+      path.join(root, "src/app/api/managed-profiles/route.ts"),
+      "utf8",
+    );
+
+    expect(source).toContain("requireFreshMfa");
+    expect(source).not.toContain("requireFreshMfaIfEnrolled");
+  });
+
+  it("requires a cookie-backed fresh MFA proof for profile deletion", async () => {
+    const source = await readFile(
+      path.join(root, "src/app/api/managed-profiles/[id]/route.ts"),
+      "utf8",
+    );
+
+    expect(source).toContain("requireFreshMfa");
+    expect(source).not.toContain("requireFreshMfaIfEnrolled");
+  });
+
+  it("does not publish an emancipation API surface", async () => {
+    const source = await readFile(
+      path.join(root, "prisma/schema.prisma"),
+      "utf8",
+    );
+
+    expect(source.toLowerCase()).not.toContain("emancipation");
+
+    const routes = await readdir(
+      path.join(root, "src/app/api/managed-profiles"),
+      { recursive: true },
+    );
+    expect(
+      routes.some((entry) => entry.toLowerCase().includes("emancip")),
+    ).toBe(false);
+  });
+
+  it("does not claim notification fanout before its consent plan exists", async () => {
+    const source = await readFile(
+      path.join(root, "prisma/schema.prisma"),
+      "utf8",
+    );
+
+    expect(source).not.toContain("notification dispatcher fans reminders");
+    expect(source).toContain("later notification plan");
+  });
+
+  it("uses the same record lock for every Guardian-reducing transition", async () => {
+    const lifecycle = await readFile(
+      path.join(root, "src/lib/managed-profiles/lifecycle.ts"),
+      "utf8",
+    );
+    const grants = await readFile(
+      path.join(root, "src/lib/sharing/grants.ts"),
+      "utf8",
+    );
+    const accountDeletion = await readFile(
+      path.join(root, "src/app/api/settings/account/route.ts"),
+      "utf8",
+    );
+
+    expect(lifecycle).toContain("pg_advisory_xact_lock");
+    expect(lifecycle).toContain("clearManagedProfileMarker");
+    expect(lifecycle).toContain("deleteManagedProfile");
+    expect(grants).toContain("reduceManagedProfileGuardian");
+    expect(accountDeletion).toContain("deleteGuardianAccountWithLifecycle");
+  });
+});
diff --git a/src/app/api/account/grants/[id]/renounce/route.ts b/src/app/api/account/grants/[id]/renounce/route.ts
index 5ab130a1d..2e5556a07 100644
--- a/src/app/api/account/grants/[id]/renounce/route.ts
+++ b/src/app/api/account/grants/[id]/renounce/route.ts
@@ -35,6 +35,7 @@ import { auditLog } from "@/lib/auth/audit";
 import { prisma } from "@/lib/db";
 import { annotate } from "@/lib/logging/context";
 import { GRANT_PARTY_SELECT, toGrantView } from "@/lib/sharing/grant-view";
+import { LastManagedGuardianError } from "@/lib/managed-profiles/lifecycle";
 import { GrantError, renounceGrantAndClearSwitch } from "@/lib/sharing/grants";
 
 type RouteParams = { params: Promise<{ id: string }> };
@@ -76,6 +77,11 @@ export const POST = apiHandler(
       });
     } catch (err) {
       if (err instanceof GrantError) return renounceErrorResponse(err);
+      if (err instanceof LastManagedGuardianError) {
+        return apiError("Add another Guardian before ending this access", 409, {
+          errorCode: "managed_profile.guardian.required",
+        });
+      }
       throw err;
     }
   },
diff --git a/src/app/api/account/grants/[id]/route.ts b/src/app/api/account/grants/[id]/route.ts
index 0fceca8b0..733098b39 100644
--- a/src/app/api/account/grants/[id]/route.ts
+++ b/src/app/api/account/grants/[id]/route.ts
@@ -34,6 +34,7 @@ import { auditLog } from "@/lib/auth/audit";
 import { prisma } from "@/lib/db";
 import { annotate } from "@/lib/logging/context";
 import { GRANT_PARTY_SELECT, toGrantView } from "@/lib/sharing/grant-view";
+import { LastManagedGuardianError } from "@/lib/managed-profiles/lifecycle";
 import { GrantError, revokeGrantAndClearSwitch } from "@/lib/sharing/grants";
 
 type RouteParams = { params: Promise<{ id: string }> };
@@ -75,6 +76,11 @@ export const DELETE = apiHandler(
       });
     } catch (err) {
       if (err instanceof GrantError) return revokeErrorResponse(err);
+      if (err instanceof LastManagedGuardianError) {
+        return apiError("Add another Guardian before ending this access", 409, {
+          errorCode: "managed_profile.guardian.required",
+        });
+      }
       throw err;
     }
   },
diff --git a/src/app/api/managed-profiles/[id]/guardians/[grantId]/route.ts b/src/app/api/managed-profiles/[id]/guardians/[grantId]/route.ts
new file mode 100644
index 000000000..6b33c31d0
--- /dev/null
+++ b/src/app/api/managed-profiles/[id]/guardians/[grantId]/route.ts
@@ -0,0 +1,49 @@
+import { NextRequest } from "next/server";
+
+import {
+  apiHandler,
+  MFA_STEP_UP_MAX_AGE_SECONDS,
+  requireFreshMfa,
+} from "@/lib/api-handler";
+import { apiError, apiSuccess } from "@/lib/api-response";
+import {
+  LastManagedGuardianError,
+  ManagedProfileLifecycleError,
+} from "@/lib/managed-profiles/lifecycle";
+import { revokeManagedProfileGuardian } from "@/lib/sharing/grants";
+import { annotate } from "@/lib/logging/context";
+
+type RouteParams = { params: Promise<{ id: string; grantId: string }> };
+
+/** End another Guardian's access from a freshly verified browser session. */
+export const DELETE = apiHandler(
+  async (_request: NextRequest, { params }: RouteParams) => {
+    const { user } = await requireFreshMfa(MFA_STEP_UP_MAX_AGE_SECONDS);
+    const { id, grantId } = await params;
+
+    try {
+      const grant = await revokeManagedProfileGuardian({
+        profileId: id,
+        guardianId: user.id,
+        grantId,
+      });
+      annotate({
+        action: { name: "managed_profile.guardian.revoked" },
+        meta: { profile_id: id, grant_id: grant.id },
+      });
+      return apiSuccess(grant);
+    } catch (error) {
+      if (error instanceof LastManagedGuardianError) {
+        return apiError("Add another Guardian before ending this access", 409, {
+          errorCode: "managed_profile.guardian.required",
+        });
+      }
+      if (error instanceof ManagedProfileLifecycleError) {
+        return apiError("Managed profile or Guardian not found", 404, {
+          errorCode: "managed_profile.not_found",
+        });
+      }
+      throw error;
+    }
+  },
+);
diff --git a/src/app/api/managed-profiles/[id]/guardians/route.ts b/src/app/api/managed-profiles/[id]/guardians/route.ts
new file mode 100644
index 000000000..80b8a13de
--- /dev/null
+++ b/src/app/api/managed-profiles/[id]/guardians/route.ts
@@ -0,0 +1,102 @@
+import { NextRequest } from "next/server";
+import { z } from "zod/v4";
+
+import {
+  apiHandler,
+  MFA_STEP_UP_MAX_AGE_SECONDS,
+  requireFreshMfa,
+} from "@/lib/api-handler";
+import {
+  apiError,
+  apiSuccess,
+  returnAllZodIssues,
+  safeJson,
+} from "@/lib/api-response";
+import { prisma } from "@/lib/db";
+import { annotate } from "@/lib/logging/context";
+import { ManagedProfileLifecycleError } from "@/lib/managed-profiles/lifecycle";
+import { checkRateLimit } from "@/lib/rate-limit";
+import { GrantError, inviteManagedProfileGuardian } from "@/lib/sharing/grants";
+
+type RouteParams = { params: Promise<{ id: string }> };
+
+const INVITE_LIMIT = 10;
+const INVITE_WINDOW_MS = 60 * 60 * 1000;
+
+const guardianInviteSchema = z
+  .object({
+    identifier: z.string().trim().min(1).max(255),
+    expiresAt: z.iso.datetime({ offset: true }).nullable().optional(),
+  })
+  .strict();
+
+/** Invite another Guardian from a cookie-backed, freshly verified session. */
+export const POST = apiHandler(
+  async (request: NextRequest, { params }: RouteParams) => {
+    const { user } = await requireFreshMfa(MFA_STEP_UP_MAX_AGE_SECONDS);
+    const rateLimit = await checkRateLimit(
+      `managed-profile:guardian-invite:${user.id}`,
+      INVITE_LIMIT,
+      INVITE_WINDOW_MS,
+    );
+    if (!rateLimit.allowed) {
+      return apiError("Too many invitations, try again later", 429);
+    }
+    const { data: body, error: jsonError } = await safeJson(request, {
+      maxBytes: 8 * 1024,
+    });
+    if (jsonError) return jsonError;
+    const parsed = guardianInviteSchema.safeParse(body);
+    if (!parsed.success) return returnAllZodIssues(parsed.error, 422);
+    const { id } = await params;
+
+    const invitee = await prisma.user.findFirst({
+      where: {
+        OR: [
+          { username: { equals: parsed.data.identifier, mode: "insensitive" } },
+          { email: { equals: parsed.data.identifier, mode: "insensitive" } },
+        ],
+      },
+      select: { id: true },
+    });
+    if (!invitee) return apiError("No account with that name or e-mail", 404);
+
+    try {
+      const grant = await inviteManagedProfileGuardian({
+        profileId: id,
+        guardianId: user.id,
+        granteeId: invitee.id,
+        expiresAt: parsed.data.expiresAt
+          ? new Date(parsed.data.expiresAt)
+          : null,
+      });
+      annotate({
+        action: { name: "managed_profile.guardian.invited" },
+        meta: { profile_id: id, grant_id: grant.id },
+      });
+      return apiSuccess(grant, 201);
+    } catch (error) {
+      if (error instanceof GrantError && error.code === "self_grant") {
+        return apiError("An account cannot be shared with itself", 422, {
+          errorCode: "managed_profile.guardian.self",
+        });
+      }
+      if (error instanceof GrantError) {
+        return apiError("That account already has access", 409, {
+          errorCode: "managed_profile.guardian.duplicate",
+        });
+      }
+      if (error instanceof ManagedProfileLifecycleError) {
+        if (error.code === "managed_grantee") {
+          return apiError("A managed profile cannot be a Guardian", 422, {
+            errorCode: "managed_profile.guardian.managed_invitee",
+          });
+        }
+        return apiError("Managed profile not found", 404, {
+          errorCode: "managed_profile.not_found",
+        });
+      }
+      throw error;
+    }
+  },
+);
diff --git a/src/app/api/managed-profiles/[id]/route.ts b/src/app/api/managed-profiles/[id]/route.ts
new file mode 100644
index 000000000..e952f5f80
--- /dev/null
+++ b/src/app/api/managed-profiles/[id]/route.ts
@@ -0,0 +1,40 @@
+import { NextRequest } from "next/server";
+
+import {
+  apiHandler,
+  MFA_STEP_UP_MAX_AGE_SECONDS,
+  requireFreshMfa,
+} from "@/lib/api-handler";
+import { apiError, apiSuccess } from "@/lib/api-response";
+import {
+  deleteManagedProfile,
+  ManagedProfileLifecycleError,
+} from "@/lib/managed-profiles/lifecycle";
+import { annotate } from "@/lib/logging/context";
+
+type RouteParams = { params: Promise<{ id: string }> };
+
+/** Delete a managed record only after its cookie-backed Guardian proves MFA. */
+export const DELETE = apiHandler(
+  async (_request: NextRequest, { params }: RouteParams) => {
+    const { user } = await requireFreshMfa(MFA_STEP_UP_MAX_AGE_SECONDS);
+    const { id } = await params;
+
+    try {
+      await deleteManagedProfile({ profileId: id, guardianId: user.id });
+    } catch (error) {
+      if (error instanceof ManagedProfileLifecycleError) {
+        return apiError("Managed profile not found", 404, {
+          errorCode: "managed_profile.not_found",
+        });
+      }
+      throw error;
+    }
+
+    annotate({
+      action: { name: "managed_profile.delete" },
+      meta: { profile_id: id },
+    });
+    return apiSuccess({ deleted: true });
+  },
+);
diff --git a/src/app/api/managed-profiles/route.ts b/src/app/api/managed-profiles/route.ts
new file mode 100644
index 000000000..964a6e0bf
--- /dev/null
+++ b/src/app/api/managed-profiles/route.ts
@@ -0,0 +1,73 @@
+import { NextRequest } from "next/server";
+import { z } from "zod/v4";
+
+import {
+  apiHandler,
+  MFA_STEP_UP_MAX_AGE_SECONDS,
+  requireFreshMfa,
+} from "@/lib/api-handler";
+import { apiSuccess, returnAllZodIssues, safeJson } from "@/lib/api-response";
+import { auditLog } from "@/lib/auth/audit";
+import { createManagedProfile } from "@/lib/managed-profiles/create";
+import { annotate } from "@/lib/logging/context";
+import { isValidTimezone } from "@/lib/tz/format";
+
+const managedProfileSchema = z
+  .object({
+    displayName: z.string().trim().min(1).max(80),
+    dateOfBirth: z.iso.date().nullable().optional(),
+    locale: z.enum(["de", "en", "es", "fr", "it", "pl"]),
+    timezone: z
+      .string()
+      .min(1)
+      .max(64)
+      .refine(isValidTimezone, "Invalid IANA timezone"),
+  })
+  .strict();
+
+/**
+ * Create a record a Guardian administers. This deliberately uses the
+ * cookie-only fresh-MFA gate: a Bearer token cannot mint a credential-less
+ * person and persistent management relationship.
+ */
+export const POST = apiHandler(async (request: NextRequest) => {
+  const { user } = await requireFreshMfa(MFA_STEP_UP_MAX_AGE_SECONDS);
+  const { data: body, error: jsonError } = await safeJson(request, {
+    maxBytes: 64 * 1024,
+  });
+  if (jsonError) return jsonError;
+
+  const parsed = managedProfileSchema.safeParse(body);
+  if (!parsed.success) return returnAllZodIssues(parsed.error, 422);
+
+  const { profile, creatorGrant } = await createManagedProfile({
+    creatorId: user.id,
+    displayName: parsed.data.displayName,
+    dateOfBirth: parsed.data.dateOfBirth
+      ? new Date(`${parsed.data.dateOfBirth}T00:00:00.000Z`)
+      : null,
+    locale: parsed.data.locale,
+    timezone: parsed.data.timezone,
+  });
+
+  await auditLog("managed_profile.created", {
+    userId: user.id,
+    details: { profileId: profile.id, grantId: creatorGrant.id },
+  }).catch(() => {});
+  annotate({
+    action: { name: "managed_profile.create" },
+    meta: { profile_id: profile.id },
+  });
+
+  return apiSuccess(
+    {
+      id: profile.id,
+      displayName: profile.displayName,
+      dateOfBirth: profile.dateOfBirth,
+      locale: profile.locale,
+      timezone: profile.timezone,
+      recordKind: "managed" as const,
+    },
+    201,
+  );
+});
diff --git a/src/app/api/settings/account/route.ts b/src/app/api/settings/account/route.ts
index 1b6125a76..d976062ab 100644
--- a/src/app/api/settings/account/route.ts
+++ b/src/app/api/settings/account/route.ts
@@ -1,7 +1,6 @@
 import { prisma } from "@/lib/db";
 import { auditLog } from "@/lib/auth/audit";
 import { apiSuccess, apiError, getClientIp } from "@/lib/api-response";
-import { destroyAllSessions } from "@/lib/auth/session";
 import { NextRequest } from "next/server";
 import {
   apiHandler,
@@ -9,6 +8,10 @@ import {
   MFA_STEP_UP_MAX_AGE_SECONDS,
 } from "@/lib/api-handler";
 import { annotate } from "@/lib/logging/context";
+import {
+  deleteGuardianAccountWithLifecycle,
+  LastManagedGuardianError,
+} from "@/lib/managed-profiles/lifecycle";
 
 export const dynamic = "force-dynamic";
 
@@ -54,27 +57,41 @@ export const DELETE = apiHandler(async (request: NextRequest) => {
   const userId = user.id;
   const username = user.username;
 
-  // Log BEFORE deletion. The audit row's userId is SetNull post-cascade
-  // (per schema), but we then immediately purge it below for GDPR Art. 17
-  // erasure completeness — see comment further down.
-  await auditLog("user.account.delete", {
-    userId,
-    ipAddress: getClientIp(request),
-    details: { username },
-  });
+  try {
+    await deleteGuardianAccountWithLifecycle(userId, async (tx) => {
+      // The invariant has now passed, so this success event cannot survive a
+      // refusal. It is purged with the rest of the account's audit history.
+      await auditLog("user.account.delete", {
+        userId,
+        ipAddress: getClientIp(request),
+        details: { username },
+        client: tx,
+      });
 
-  // Destroy all sessions first
-  await destroyAllSessions(userId);
+      // Destroy all sessions before the user row goes, inside the same record
+      // lifecycle transaction so a refusal leaves every account state intact.
+      await tx.session.deleteMany({ where: { userId } });
 
-  // Audit V3 NEW-V3-2 / GDPR Art. 17 fix: AuditLog rows have
-  // `onDelete: SetNull` in the schema, which keeps PII (IP addresses, login
-  // city geo) attached to the record after the user is deleted. We explicitly
-  // purge them inside the same logical operation so account deletion is
-  // genuinely complete erasure.
-  await prisma.auditLog.deleteMany({ where: { userId } });
+      // Audit V3 NEW-V3-2 / GDPR Art. 17 fix: AuditLog rows have
+      // `onDelete: SetNull` in the schema, which keeps PII (IP addresses, login
+      // city geo) attached to the record after the user is deleted. We explicitly
+      // purge them inside the same logical operation so account deletion is
+      // genuinely complete erasure.
+      await tx.auditLog.deleteMany({ where: { userId } });
 
-  // Delete user — all other related data is removed via onDelete: Cascade
-  await prisma.user.delete({ where: { id: userId } });
+      // Delete user — all other related data is removed via onDelete: Cascade.
+      await tx.user.delete({ where: { id: userId } });
+    });
+  } catch (error) {
+    if (error instanceof LastManagedGuardianError) {
+      return apiError(
+        "Add another Guardian or delete the managed profile first",
+        409,
+        { errorCode: "managed_profile.guardian.required" },
+      );
+    }
+    throw error;
+  }
 
   annotate({
     action: { name: "settings.account.delete" },
diff --git a/src/lib/managed-profiles/create.ts b/src/lib/managed-profiles/create.ts
new file mode 100644
index 000000000..431e36373
--- /dev/null
+++ b/src/lib/managed-profiles/create.ts
@@ -0,0 +1,88 @@
+import { randomBytes } from "node:crypto";
+
+import { Prisma } from "@/generated/prisma/client";
+import type { AccountGrant, User } from "@/generated/prisma/client";
+import { prisma } from "@/lib/db";
+
+const USERNAME_ATTEMPTS = 4;
+
+export interface CreateManagedProfileInput {
+  creatorId: string;
+  displayName: string;
+  dateOfBirth: Date | null;
+  locale: string;
+  timezone: string;
+}
+
+export interface CreatedManagedProfile {
+  profile: User;
+  creatorGrant: AccountGrant;
+}
+
+export class ManagedProfileCreationError extends Error {
+  constructor() {
+    super("Unable to allocate a managed profile identity");
+    this.name = "ManagedProfileCreationError";
+  }
+}
+
+function managedUsername(): string {
+  return `managed-${randomBytes(18).toString("hex")}`;
+}
+
+function isUniqueViolation(error: unknown): boolean {
+  return (
+    error instanceof Prisma.PrismaClientKnownRequestError &&
+    error.code === "P2002"
+  );
+}
+
+/**
+ * Create the credential-less record and its first Guardian grant together.
+ *
+ * A profile is never useful before the creator can manage it, and a creator
+ * grant without its record is invalid by definition. Keeping both writes in
+ * one transaction makes a failed grant insert leave no login-less user behind.
+ */
+export async function createManagedProfile(
+  input: CreateManagedProfileInput,
+): Promise<CreatedManagedProfile> {
+  for (let attempt = 0; attempt < USERNAME_ATTEMPTS; attempt += 1) {
+    try {
+      return await prisma.$transaction(async (tx) => {
+        const now = new Date();
+        const profile = await tx.user.create({
+          data: {
+            username: managedUsername(),
+            email: null,
+            passwordHash: null,
+            displayName: input.displayName,
+            dateOfBirth: input.dateOfBirth,
+            locale: input.locale,
+            timezone: input.timezone,
+            managedProfileAt: now,
+          },
+        });
+        const creatorGrant = await tx.accountGrant.create({
+          data: {
+            grantorId: profile.id,
+            granteeId: input.creatorId,
+            access: "MANAGE",
+            scopeJson: Prisma.DbNull,
+            invitedAt: now,
+            acceptedAt: now,
+            expiresAt: null,
+          },
+        });
+        return { profile, creatorGrant };
+      });
+    } catch (error) {
+      if (isUniqueViolation(error) && attempt + 1 < USERNAME_ATTEMPTS) {
+        continue;
+      }
+      throw error;
+    }
+  }
+
+  throw new ManagedProfileCreationError();
+}
diff --git a/src/lib/managed-profiles/lifecycle.ts b/src/lib/managed-profiles/lifecycle.ts
new file mode 100644
index 000000000..8bb929660
--- /dev/null
+++ b/src/lib/managed-profiles/lifecycle.ts
@@ -0,0 +1,173 @@
+import { prisma } from "@/lib/db";
+import { auditLog } from "@/lib/auth/audit";
+import type { Prisma } from "@/generated/prisma/client";
+
+type Transaction = Prisma.TransactionClient;
+
+export const activeGuardianWhere = (now: Date) => ({
+  access: "MANAGE" as const,
+  acceptedAt: { not: null },
+  revokedAt: null,
+  OR: [{ expiresAt: null }, { expiresAt: { gt: now } }],
+});
+
+export type ManagedProfileLifecycleErrorCode =
+  "not_found" | "not_managed" | "not_guardian" | "managed_grantee";
+
+export class ManagedProfileLifecycleError extends Error {
+  constructor(readonly code: ManagedProfileLifecycleErrorCode) {
+    super(`managed profile lifecycle refused: ${code}`);
+    this.name = "ManagedProfileLifecycleError";
+  }
+}
+
+/** A refusal the caller can recover from by adding another Guardian. */
+export class LastManagedGuardianError extends Error {
+  constructor() {
+    super("A managed profile needs another Guardian before this change");
+    this.name = "LastManagedGuardianError";
+  }
+}
+
+/**
+ * Serialize lifecycle changes on one managed-record key for the lifetime of
+ * the caller's transaction. The lock is held before re-reading the marker and
+ * every active Guardian row, so a second reducer sees the first committed
+ * change instead of making its decision from a stale count.
+ */
+export async function withManagedProfileLock<T>(
+  tx: Transaction,
+  profileId: string,
+  operation: (
+    profile: { id: string; managedProfileAt: Date | null } | null,
+  ) => Promise<T>,
+): Promise<T> {
+  await tx.$queryRaw`
+    SELECT 1 AS locked
+    FROM pg_advisory_xact_lock(hashtextextended(${`managed-profile:${profileId}`}, 0))
+  `;
+  const profile = await tx.user.findUnique({
+    where: { id: profileId },
+    select: { id: true, managedProfileAt: true },
+  });
+  return operation(profile);
+}
+
+/**
+ * Run one removal of an active Guardian after holding the record lock and
+ * re-reading the invariant in the same transaction.
+ */
+export async function reduceManagedProfileGuardian<T>(
+  tx: Transaction,
+  profileId: string,
+  reduction: () => Promise<T>,
+): Promise<T> {
+  return withManagedProfileLock(tx, profileId, async (profile) => {
+    if (!profile?.managedProfileAt) return reduction();
+
+    const activeGuardians = await tx.accountGrant.count({
+      where: { grantorId: profile.id, ...activeGuardianWhere(new Date()) },
+    });
+    if (activeGuardians <= 1) throw new LastManagedGuardianError();
+
+    return reduction();
+  });
+}
+
+/**
+ * Keep account deletion and its Guardian checks inside the same transaction.
+ * Profiles are locked in id order so an account protecting more than one
+ * profile cannot deadlock with a concurrent lifecycle operation.
+ */
+export async function deleteGuardianAccountWithLifecycle<T>(
+  guardianId: string,
+  deleteAccount: (tx: Transaction) => Promise<T>,
+): Promise<T> {
+  return prisma.$transaction(async (tx) => {
+    const now = new Date();
+    const grants = await tx.accountGrant.findMany({
+      where: {
+        granteeId: guardianId,
+        ...activeGuardianWhere(now),
+        grantor: { managedProfileAt: { not: null } },
+      },
+      select: { grantorId: true },
+      distinct: ["grantorId"],
+      orderBy: { grantorId: "asc" },
+    });
+
+    for (const { grantorId } of grants) {
+      await withManagedProfileLock(tx, grantorId, async (profile) => {
+        if (!profile?.managedProfileAt) return;
+
+        const stillActive = await tx.accountGrant.findFirst({
+          where: {
+            grantorId,
+            granteeId: guardianId,
+            ...activeGuardianWhere(new Date()),
+          },
+          select: { id: true },
+        });
+        if (!stillActive) return;
+
+        const activeGuardians = await tx.accountGrant.count({
+          where: { grantorId, ...activeGuardianWhere(new Date()) },
+        });
+        if (activeGuardians <= 1) throw new LastManagedGuardianError();
+      });
+    }
+
+    return deleteAccount(tx);
+  });
+}
+
+export async function deleteManagedProfile(input: {
+  profileId: string;
+  guardianId: string;
+}): Promise<void> {
+  await prisma.$transaction(async (tx) => {
+    await withManagedProfileLock(tx, input.profileId, async (profile) => {
+      if (!profile) throw new ManagedProfileLifecycleError("not_found");
+      if (!profile.managedProfileAt) {
+        throw new ManagedProfileLifecycleError("not_managed");
+      }
+
+      const guardian = await tx.accountGrant.findFirst({
+        where: {
+          grantorId: profile.id,
+          granteeId: input.guardianId,
+          ...activeGuardianWhere(new Date()),
+        },
+        select: { id: true },
+      });
+      if (!guardian) throw new ManagedProfileLifecycleError("not_guardian");
+
+      await auditLog("managed_profile.deleted", {
+        userId: input.guardianId,
+        details: { profileId: profile.id },
+        client: tx,
+      });
+      await tx.user.delete({ where: { id: profile.id } });
+    });
+  });
+}
+
+/**
+ * Internal-only future compatibility hook. There is intentionally no route for
+ * this state change in the current product; holding the same lock ensures any
+ * later handover cannot race a Guardian reduction.
+ */
+export async function clearManagedProfileMarker(input: {
+  profileId: string;
+}): Promise<void> {
+  await prisma.$transaction(async (tx) => {
+    await withManagedProfileLock(tx, input.profileId, async (profile) => {
+      if (!profile) throw new ManagedProfileLifecycleError("not_found");
+      if (!profile.managedProfileAt) return;
+      await tx.user.update({
+        where: { id: profile.id },
+        data: { managedProfileAt: null },
+      });
+    });
+  });
+}
diff --git a/src/lib/sharing/grants.ts b/src/lib/sharing/grants.ts
index 908294b4e..06fdc954a 100644
--- a/src/lib/sharing/grants.ts
+++ b/src/lib/sharing/grants.ts
@@ -52,8 +52,16 @@
  * transition computed against the stale row.
  */
 import { prisma } from "@/lib/db";
+import { auditLog } from "@/lib/auth/audit";
 import { isP2002 } from "@/lib/prisma-errors";
 import { clearActingSessions } from "@/lib/sharing/acting-session";
+import {
+  activeGuardianWhere,
+  LastManagedGuardianError,
+  ManagedProfileLifecycleError,
+  reduceManagedProfileGuardian,
+  withManagedProfileLock,
+} from "@/lib/managed-profiles/lifecycle";
 import { ENTIRE_RECORD, isShareDomain } from "@/lib/sharing/scope";
 import type { ShareDomain, ShareScope } from "@/lib/sharing/scope";
 import { Prisma } from "@/generated/prisma/client";
@@ -414,25 +422,170 @@ export interface AcceptGrantInput {
  */
 export async function acceptGrant(
   input: AcceptGrantInput,
-  db: GrantDb = prisma,
 ): Promise<AccountGrant> {
-  const now = new Date();
-  const { count } = await db.accountGrant.updateMany({
-    where: {
-      id: input.grantId,
-      granteeId: input.granteeId,
-      acceptedAt: null,
-      revokedAt: null,
-      OR: [{ expiresAt: null }, { expiresAt: { gt: now } }],
-    },
-    data: { acceptedAt: now },
-  });
+  return prisma.$transaction((tx) => acceptGrantInTransaction(input, tx));
+}
 
-  if (count === 0) {
-    throw await refusalFor(input.grantId, { granteeId: input.granteeId }, db);
+async function acceptGrantInTransaction(
+  input: AcceptGrantInput,
+  tx: Prisma.TransactionClient,
+): Promise<AccountGrant> {
+  const candidate = await tx.accountGrant.findUnique({
+    where: { id: input.grantId },
+    select: { grantorId: true, access: true },
+  });
+  if (!candidate) {
+    throw await refusalFor(input.grantId, { granteeId: input.granteeId }, tx);
   }
 
-  return db.accountGrant.findUniqueOrThrow({ where: { id: input.grantId } });
+  const accept = async (managedProfile: boolean) => {
+    const now = new Date();
+    const { count } = await tx.accountGrant.updateMany({
+      where: {
+        id: input.grantId,
+        granteeId: input.granteeId,
+        acceptedAt: null,
+        revokedAt: null,
+        OR: [{ expiresAt: null }, { expiresAt: { gt: now } }],
+      },
+      data: {
+        acceptedAt: now,
+        ...(managedProfile ? { expiresAt: null } : {}),
+      },
+    });
+    if (count === 0) {
+      throw await refusalFor(input.grantId, { granteeId: input.granteeId }, tx);
+    }
+    return tx.accountGrant.findUniqueOrThrow({ where: { id: input.grantId } });
+  };
+
+  if (candidate.access !== "MANAGE") return accept(false);
+
+  return withManagedProfileLock(tx, candidate.grantorId, async (profile) =>
+    accept(Boolean(profile?.managedProfileAt)),
+  );
+}
+
+export async function inviteManagedProfileGuardian(input: {
+  profileId: string;
+  guardianId: string;
+  granteeId: string;
+  expiresAt?: Date | null;
+}): Promise<AccountGrant> {
+  return prisma.$transaction(async (tx) => {
+    return withManagedProfileLock(tx, input.profileId, async (profile) => {
+      if (!profile) throw new ManagedProfileLifecycleError("not_found");
+      if (!profile.managedProfileAt) {
+        throw new ManagedProfileLifecycleError("not_managed");
+      }
+      const guardian = await tx.accountGrant.findFirst({
+        where: {
+          grantorId: profile.id,
+          granteeId: input.guardianId,
+          ...activeGuardianWhere(new Date()),
+        },
+        select: { id: true },
+      });
+      if (!guardian) throw new ManagedProfileLifecycleError("not_guardian");
+      const grantee = await tx.user.findUnique({
+        where: { id: input.granteeId },
+        select: { managedProfileAt: true },
+      });
+      if (grantee?.managedProfileAt) {
+        throw new ManagedProfileLifecycleError("managed_grantee");
+      }
+      const grant = await inviteGrant(
+        {
+          grantorId: profile.id,
+          granteeId: input.granteeId,
+          access: "MANAGE",
+          scope: null,
+          expiresAt: input.expiresAt ?? null,
+        },
+        tx,
+      );
+      await auditLog("managed_profile.guardian.invited", {
+        userId: profile.id,
+        actorUserId: input.guardianId,
+        details: { grantId: grant.id },
+        client: tx,
+      });
+      return grant;
+    });
+  });
+}
+
+export async function revokeManagedProfileGuardian(input: {
+  profileId: string;
+  guardianId: string;
+  grantId: string;
+}): Promise<AccountGrant> {
+  return prisma.$transaction(async (tx) => {
+    return withManagedProfileLock(tx, input.profileId, async (profile) => {
+      if (!profile) throw new ManagedProfileLifecycleError("not_found");
+      if (!profile.managedProfileAt) {
+        throw new ManagedProfileLifecycleError("not_managed");
+      }
+      const requester = await tx.accountGrant.findFirst({
+        where: {
+          grantorId: profile.id,
+          granteeId: input.guardianId,
+          ...activeGuardianWhere(new Date()),
+        },
+        select: { id: true },
+      });
+      if (!requester) throw new ManagedProfileLifecycleError("not_guardian");
+
+      const target = await tx.accountGrant.findFirst({
+        where: {
+          id: input.grantId,
+          grantorId: profile.id,
+          access: "MANAGE",
+          revokedAt: null,
+        },
+        select: {
+          id: true,
+          granteeId: true,
+          acceptedAt: true,
+          expiresAt: true,
+        },
+      });
+      if (!target) throw new ManagedProfileLifecycleError("not_guardian");
+      if (target.granteeId === input.guardianId) {
+        throw new ManagedProfileLifecycleError("not_guardian");
+      }
+
+      const now = new Date();
+      const targetIsActive =
+        target.acceptedAt !== null &&
+        (target.expiresAt === null || target.expiresAt > now);
+      if (targetIsActive) {
+        const activeGuardians = await tx.accountGrant.count({
+          where: { grantorId: profile.id, ...activeGuardianWhere(now) },
+        });
+        if (activeGuardians <= 1) throw new LastManagedGuardianError();
+      }
+
+      await tx.accountGrant.update({
+        where: { id: target.id },
+        // `revokedBy` records which grant party withdrew access. The managed
+        // profile is the grantor; the individual Guardian is durable audit
+        // attribution below rather than an overloaded enum value.
+        data: { revokedAt: now, revokedBy: "GRANTOR" },
+      });
+      await clearActingSessions(
+        { grantorId: profile.id, granteeId: target.granteeId },
+        tx,
+      );
+      await auditLog("managed_profile.guardian.revoked", {
+        userId: profile.id,
+        actorUserId: input.guardianId,
+        details: { grantId: target.id },
+        client: tx,
+      });
+      return tx.accountGrant.findUniqueOrThrow({ where: { id: target.id } });
+    });
+  });
 }
 
 export interface RevokeGrantInput {
@@ -451,9 +604,10 @@ export interface RevokeGrantInput {
  */
 export async function revokeGrant(
   input: RevokeGrantInput,
-  db: GrantDb = prisma,
 ): Promise<AccountGrant> {
-  return endGrant(input.grantId, { grantorId: input.grantorId }, "GRANTOR", db);
+  return prisma.$transaction((tx) =>
+    endGrant(input.grantId, { grantorId: input.grantorId }, "GRANTOR", tx),
+  );
 }
 
 export interface RenounceGrantInput {
@@ -472,9 +626,10 @@ export interface RenounceGrantInput {
  */
 export async function renounceGrant(
   input: RenounceGrantInput,
-  db: GrantDb = prisma,
 ): Promise<AccountGrant> {
-  return endGrant(input.grantId, { granteeId: input.granteeId }, "GRANTEE", db);
+  return prisma.$transaction((tx) =>
+    endGrant(input.grantId, { granteeId: input.granteeId }, "GRANTEE", tx),
+  );
 }
 
 /**
@@ -511,7 +666,9 @@ export interface EndedGrant {
 export async function revokeGrantAndClearSwitch(
   input: RevokeGrantInput,
 ): Promise<EndedGrant> {
-  return endAndClear((tx) => revokeGrant(input, tx));
+  return endAndClear((tx) =>
+    endGrant(input.grantId, { grantorId: input.grantorId }, "GRANTOR", tx),
+  );
 }
 
 /**
@@ -525,7 +682,9 @@ export async function revokeGrantAndClearSwitch(
 export async function renounceGrantAndClearSwitch(
   input: RenounceGrantInput,
 ): Promise<EndedGrant> {
-  return endAndClear((tx) => renounceGrant(input, tx));
+  return endAndClear((tx) =>
+    endGrant(input.grantId, { granteeId: input.granteeId }, "GRANTEE", tx),
+  );
 }
 
 // ── Resolution ──────────────────────────────────────────────────────────────
@@ -603,16 +762,42 @@ async function endGrant(
   grantId: string,
   actor: { grantorId: string } | { granteeId: string },
   revokedBy: "GRANTOR" | "GRANTEE",
-  db: GrantDb,
+  db: Prisma.TransactionClient,
 ): Promise<AccountGrant> {
-  const { count } = await db.accountGrant.updateMany({
-    where: { id: grantId, ...actor, revokedAt: null },
-    data: { revokedAt: new Date(), revokedBy },
+  const current = await db.accountGrant.findUnique({
+    where: { id: grantId },
+    select: {
+      grantorId: true,
+      granteeId: true,
+      access: true,
+      acceptedAt: true,
+      revokedAt: true,
+      expiresAt: true,
+    },
   });
 
-  if (count === 0) throw await refusalFor(grantId, actor, db);
+  const end = async () => {
+    const { count } = await db.accountGrant.updateMany({
+      where: { id: grantId, ...actor, revokedAt: null },
+      data: { revokedAt: new Date(), revokedBy },
+    });
+    if (count === 0) throw await refusalFor(grantId, actor, db);
+    return db.accountGrant.findUniqueOrThrow({ where: { id: grantId } });
+  };
 
-  return db.accountGrant.findUniqueOrThrow({ where: { id: grantId } });
+  const actorOwnsGrant =
+    current &&
+    ("grantorId" in actor
+      ? current.grantorId === actor.grantorId
+      : current.granteeId === actor.granteeId);
+  const isActiveManagedGuardian =
+    current?.access === "MANAGE" &&
+    current.acceptedAt !== null &&
+    current.revokedAt === null &&
+    (current.expiresAt === null || current.expiresAt > new Date());
+
+  if (!actorOwnsGrant || !isActiveManagedGuardian) return end();
+  return reduceManagedProfileGuardian(db, current.grantorId, end);
 }
 
 /**
diff --git a/tests/integration/managed-profile-guardian-concurrency.test.ts b/tests/integration/managed-profile-guardian-concurrency.test.ts
new file mode 100644
index 000000000..274f943a8
--- /dev/null
+++ b/tests/integration/managed-profile-guardian-concurrency.test.ts
@@ -0,0 +1,82 @@
+import { beforeEach, describe, expect, it } from "vitest";
+
+import { createManagedProfile } from "@/lib/managed-profiles/create";
+import {
+  acceptGrant,
+  inviteGrant,
+  renounceGrant,
+  revokeGrant,
+} from "@/lib/sharing/grants";
+
+import { getPrismaClient, truncateAllTables } from "./setup";
+
+let sequence = 0;
+
+async function makeAdult(label: string) {
+  const suffix = sequence++;
+  return getPrismaClient().user.create({
+    data: {
+      username: `${label}-${suffix}`,
+      email: `${label}-${suffix}@example.test`,
+    },
+  });
+}
+
+async function twoGuardians() {
+  const creator = await makeAdult("creator");
+  const secondGuardian = await makeAdult("second-guardian");
+  const { profile, creatorGrant } = await createManagedProfile({
+    creatorId: creator.id,
+    displayName: "Managed profile",
+    dateOfBirth: null,
+    locale: "en",
+    timezone: "UTC",
+  });
+  const invitation = await inviteGrant({
+    grantorId: profile.id,
+    granteeId: secondGuardian.id,
+    access: "MANAGE",
+    scope: null,
+  });
+  const secondGrant = await acceptGrant({
+    grantId: invitation.id,
+    granteeId: secondGuardian.id,
+  });
+  return { creator, secondGuardian, profile, creatorGrant, secondGrant };
+}
+
+beforeEach(async () => {
+  await truncateAllTables(getPrismaClient());
+});
+
+describe("managed profile Guardian concurrency (real Postgres)", () => {
+  it("allows only one concurrent reduction of the final two Guardians", async () => {
+    const { creatorGrant, secondGuardian, secondGrant, profile } =
+      await twoGuardians();
+
+    const results = await Promise.allSettled([
+      revokeGrant({ grantId: creatorGrant.id, grantorId: profile.id }),
+      renounceGrant({
+        grantId: secondGrant.id,
+        granteeId: secondGuardian.id,
+      }),
+    ]);
+
+    expect(
+      results.filter((result) => result.status === "fulfilled"),
+    ).toHaveLength(1);
+    expect(
+      results.filter((result) => result.status === "rejected"),
+    ).toHaveLength(1);
+    expect(
+      await getPrismaClient().accountGrant.count({
+        where: {
+          grantorId: profile.id,
+          access: "MANAGE",
+          acceptedAt: { not: null },
+          revokedAt: null,
+        },
+      }),
+    ).toBe(1);
+  });
+});
diff --git a/tests/integration/managed-profile-lifecycle.test.ts b/tests/integration/managed-profile-lifecycle.test.ts
new file mode 100644
index 000000000..39c7219e2
--- /dev/null
+++ b/tests/integration/managed-profile-lifecycle.test.ts
@@ -0,0 +1,882 @@
+import { NextRequest } from "next/server";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { cookieJar, headerJar, queuedSessionIds } from "./mock-next-headers";
+import { getPrismaClient, truncateAllTables } from "./setup";
+import { createManagedProfile } from "@/lib/managed-profiles/create";
+import {
+  acceptGrant,
+  findActiveGrant,
+  inviteGrant,
+} from "@/lib/sharing/grants";
+import {
+  clearManagedProfileMarker,
+  ManagedProfileLifecycleError,
+} from "@/lib/managed-profiles/lifecycle";
+
+vi.mock("next/headers", async () => {
+  const { cookieJar, headerJar, queuedSessionIds } =
+    await import("./mock-next-headers");
+  return {
+    headers: vi.fn(async () => ({
+      get: (name: string) => headerJar.get(name.toLowerCase()) ?? null,
+    })),
+    cookies: vi.fn(async () => {
+      const snapshot = new Map(cookieJar);
+      const queuedSessionId = queuedSessionIds.shift();
+      if (queuedSessionId) {
+        snapshot.set("healthlog_session", queuedSessionId);
+      }
+      return {
+        get: (name: string) => {
+          const value = snapshot.get(name);
+          return value ? { name, value } : undefined;
+        },
+        set: (name: string, value: string) => {
+          cookieJar.set(name, value);
+        },
+        delete: (name: string) => {
+          cookieJar.delete(name);
+        },
+      };
+    }),
+  };
+});
+
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+
+let sequence = 0;
+
+async function createFreshMfaUser(label = "guardian") {
+  const suffix = sequence++;
+  const prisma = getPrismaClient();
+  const user = await prisma.user.create({
+    data: {
+      username: `${label}-${suffix}`,
+      email: `${label}-${suffix}@example.test`,
+      totpConfirmedAt: new Date(),
+    },
+  });
+  const session = await prisma.session.create({
+    data: {
+      userId: user.id,
+      expiresAt: new Date(Date.now() + 60 * 60 * 1000),
+      mfaVerifiedAt: new Date(),
+    },
+  });
+  return { user, sessionId: session.id };
+}
+
+async function signInWithFreshMfa() {
+  const { user, sessionId } = await createFreshMfaUser();
+  cookieJar.set("healthlog_session", sessionId);
+  return user;
+}
+
+async function makeAdult(label: string) {
+  const suffix = sequence++;
+  return getPrismaClient().user.create({
+    data: {
+      username: `${label}-${suffix}`,
+      email: `${label}-${suffix}@example.test`,
+    },
+  });
+}
+
+async function createTwoGuardians() {
+  const creator = await createFreshMfaUser("creator");
+  const secondGuardian = await createFreshMfaUser("second-guardian");
+  const { profile, creatorGrant } = await createManagedProfile({
+    creatorId: creator.user.id,
+    displayName: "Managed profile",
+    dateOfBirth: null,
+    locale: "en",
+    timezone: "UTC",
+  });
+  const invitation = await inviteGrant({
+    grantorId: profile.id,
+    granteeId: secondGuardian.user.id,
+    access: "MANAGE",
+    scope: null,
+  });
+  const secondGrant = await acceptGrant({
+    grantId: invitation.id,
+    granteeId: secondGuardian.user.id,
+  });
+  return { creator, secondGuardian, profile, creatorGrant, secondGrant };
+}
+
+function createRequest(body: unknown): NextRequest {
+  return new NextRequest("http://localhost/api/managed-profiles", {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+beforeEach(async () => {
+  await truncateAllTables(getPrismaClient());
+  cookieJar.clear();
+  headerJar.clear();
+  queuedSessionIds.length = 0;
+});
+
+afterEach(async () => {
+  const prisma = getPrismaClient();
+  await prisma.$executeRawUnsafe(
+    'DROP TRIGGER IF EXISTS managed_profile_creation_failure ON "account_grants"',
+  );
+  await prisma.$executeRawUnsafe(
+    "DROP FUNCTION IF EXISTS fail_managed_profile_creation()",
+  );
+  await prisma.$executeRawUnsafe(
+    'DROP TRIGGER IF EXISTS managed_profile_acceptance_failure ON "account_grants"',
+  );
+  await prisma.$executeRawUnsafe(
+    "DROP FUNCTION IF EXISTS fail_managed_profile_acceptance()",
+  );
+  await prisma.$executeRawUnsafe(
+    "DROP TRIGGER IF EXISTS managed_profile_delete_audit_failure ON audit_logs",
+  );
+  await prisma.$executeRawUnsafe(
+    "DROP FUNCTION IF EXISTS fail_managed_profile_delete_audit()",
+  );
+  await prisma.$executeRawUnsafe(
+    "DROP TRIGGER IF EXISTS managed_guardian_audit_failure ON audit_logs",
+  );
+  await prisma.$executeRawUnsafe(
+    "DROP FUNCTION IF EXISTS fail_managed_guardian_audit()",
+  );
+});
+
+describe("managed profile lifecycle (real Postgres)", () => {
+  it("creation records a complete DOB and one accepted non-expiring Guardian grant", async () => {
+    const guardian = await signInWithFreshMfa();
+    const { POST } = await import("@/app/api/managed-profiles/route");
+
+    const response = await POST(
+      createRequest({
+        displayName: "Managed profile",
+        dateOfBirth: "2012-03-04",
+        locale: "de",
+        timezone: "Europe/Zurich",
+      }),
+    );
+    expect(response.status).toBe(201);
+
+    const body = await response.json();
+    const profile = await getPrismaClient().user.findUniqueOrThrow({
+      where: { id: body.data.id },
+    });
+    expect(profile.username).toMatch(/^managed-/);
+    expect(profile.username).not.toContain("Managed profile");
+    expect(profile.email).toBeNull();
+    expect(profile.passwordHash).toBeNull();
+    expect(profile.dateOfBirth?.toISOString().slice(0, 10)).toBe("2012-03-04");
+    expect(profile.locale).toBe("de");
+    expect(profile.timezone).toBe("Europe/Zurich");
+    expect(profile.managedProfileAt).not.toBeNull();
+
+    const grant = await getPrismaClient().accountGrant.findFirstOrThrow({
+      where: { grantorId: profile.id, granteeId: guardian.id },
+    });
+    expect(grant.access).toBe("MANAGE");
+    expect(grant.acceptedAt).not.toBeNull();
+    expect(grant.expiresAt).toBeNull();
+  });
+
+  it("creation accepts an absent DOB without fabricating one", async () => {
+    await signInWithFreshMfa();
+    const { POST } = await import("@/app/api/managed-profiles/route");
+
+    const response = await POST(
+      createRequest({
+        displayName: "No birth date",
+        locale: "en",
+        timezone: "UTC",
+      }),
+    );
+    expect(response.status).toBe(201);
+    const body = await response.json();
+    const profile = await getPrismaClient().user.findUniqueOrThrow({
+      where: { id: body.data.id },
+    });
+    expect(profile.dateOfBirth).toBeNull();
+  });
+
+  it("creation rolls the profile back when its Guardian grant fails", async () => {
+    await signInWithFreshMfa();
+    const prisma = getPrismaClient();
+    await prisma.$executeRawUnsafe(
+      "CREATE FUNCTION fail_managed_profile_creation() RETURNS trigger LANGUAGE plpgsql AS $$ BEGIN RAISE EXCEPTION 'managed profile grant failure'; END; $$",
+    );
+    await prisma.$executeRawUnsafe(
+      'CREATE TRIGGER managed_profile_creation_failure BEFORE INSERT ON "account_grants" FOR EACH ROW EXECUTE FUNCTION fail_managed_profile_creation()',
+    );
+
+    const { POST } = await import("@/app/api/managed-profiles/route");
+    const response = await POST(
+      createRequest({
+        displayName: "Must roll back",
+        locale: "en",
+        timezone: "UTC",
+      }),
+    );
+    expect(response.status).toBe(500);
+    expect(
+      await prisma.user.count({
+        where: { managedProfileAt: { not: null } },
+      }),
+    ).toBe(0);
+    expect(await prisma.accountGrant.count()).toBe(0);
+  });
+
+  it("second Guardian accepts through the ordinary invitation and does not expire", async () => {
+    const creator = await signInWithFreshMfa();
+    const secondGuardian = await makeAdult("second-guardian");
+    const { profile } = await createManagedProfile({
+      creatorId: creator.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const invitationExpiry = new Date(Date.now() + 60 * 60 * 1000);
+
+    const invitation = await inviteGrant({
+      grantorId: profile.id,
+      granteeId: secondGuardian.id,
+      access: "MANAGE",
+      scope: null,
+      expiresAt: invitationExpiry,
+    });
+    expect(invitation.acceptedAt).toBeNull();
+    expect(invitation.expiresAt).toEqual(invitationExpiry);
+
+    const accepted = await acceptGrant({
+      grantId: invitation.id,
+      granteeId: secondGuardian.id,
+    });
+    expect(accepted.acceptedAt).not.toBeNull();
+    expect(accepted.expiresAt).toBeNull();
+    expect(
+      await findActiveGrant(
+        { grantorId: profile.id, granteeId: secondGuardian.id },
+        getPrismaClient(),
+        new Date(Date.now() + 24 * 60 * 60 * 1000),
+      ),
+    ).not.toBeNull();
+  });
+
+  it("lets a cookie-authenticated Guardian invite and revoke another Guardian", async () => {
+    const creator = await createFreshMfaUser("creator");
+    const secondGuardian = await createFreshMfaUser("second-guardian");
+    cookieJar.set("healthlog_session", creator.sessionId);
+    const { profile } = await createManagedProfile({
+      creatorId: creator.user.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const invitationExpiry = new Date(Date.now() + 60 * 60 * 1000);
+
+    const { POST: inviteGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/route");
+    const invited = await inviteGuardian(
+      new NextRequest(
+        `http://localhost/api/managed-profiles/${profile.id}/guardians`,
+        {
+          method: "POST",
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({
+            identifier: secondGuardian.user.username,
+            expiresAt: invitationExpiry.toISOString(),
+          }),
+        },
+      ),
+      { params: Promise.resolve({ id: profile.id }) },
+    );
+    expect(invited.status).toBe(201);
+    const invitation = (await invited.json()).data;
+    expect(invitation.acceptedAt).toBeNull();
+    expect(new Date(invitation.expiresAt).getTime()).toBe(
+      invitationExpiry.getTime(),
+    );
+
+    cookieJar.set("healthlog_session", secondGuardian.sessionId);
+    const { POST: acceptInvitation } =
+      await import("@/app/api/account/grants/[id]/accept/route");
+    const accepted = await acceptInvitation(
+      new NextRequest(
+        `http://localhost/api/account/grants/${invitation.id}/accept`,
+        {
+          method: "POST",
+        },
+      ),
+      { params: Promise.resolve({ id: invitation.id }) },
+    );
+    expect(accepted.status).toBe(200);
+    expect(
+      await getPrismaClient().accountGrant.findUniqueOrThrow({
+        where: { id: invitation.id },
+      }),
+    ).toMatchObject({ acceptedAt: expect.any(Date), expiresAt: null });
+    await getPrismaClient().session.update({
+      where: { id: secondGuardian.sessionId },
+      data: { actingAsUserId: profile.id },
+    });
+
+    cookieJar.set("healthlog_session", creator.sessionId);
+    const { DELETE: revokeGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/[grantId]/route");
+    const revoked = await revokeGuardian(
+      new NextRequest(
+        `http://localhost/api/managed-profiles/${profile.id}/guardians/${invitation.id}`,
+        { method: "DELETE" },
+      ),
+      { params: Promise.resolve({ id: profile.id, grantId: invitation.id }) },
+    );
+    expect(revoked.status).toBe(200);
+    expect(
+      await getPrismaClient().accountGrant.findUniqueOrThrow({
+        where: { id: invitation.id },
+      }),
+    ).toMatchObject({ revokedBy: "GRANTOR" });
+    expect(
+      await getPrismaClient().session.findUniqueOrThrow({
+        where: { id: secondGuardian.sessionId },
+      }),
+    ).toMatchObject({ actingAsUserId: null });
+    const audit = await getPrismaClient().auditLog.findMany({
+      where: {
+        userId: profile.id,
+        action: {
+          in: [
+            "managed_profile.guardian.invited",
+            "managed_profile.guardian.revoked",
+          ],
+        },
+      },
+      orderBy: { createdAt: "asc" },
+    });
+    expect(audit).toHaveLength(2);
+    expect(audit.map((entry) => entry.actorUserId)).toEqual([
+      creator.user.id,
+      creator.user.id,
+    ]);
+    expect(audit.map((entry) => JSON.parse(entry.details ?? "{}"))).toEqual([
+      { grantId: invitation.id },
+      { grantId: invitation.id },
+    ]);
+  });
+
+  it("withdraws a pending Guardian invitation without touching the active count and permits re-invitation", async () => {
+    const creator = await createFreshMfaUser("creator");
+    const secondGuardian = await createFreshMfaUser("second-guardian");
+    cookieJar.set("healthlog_session", creator.sessionId);
+    const { profile } = await createManagedProfile({
+      creatorId: creator.user.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const { POST: inviteGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/route");
+    const { DELETE: revokeGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/[grantId]/route");
+    const invite = async () => {
+      const response = await inviteGuardian(
+        new NextRequest(
+          `http://localhost/api/managed-profiles/${profile.id}/guardians`,
+          {
+            method: "POST",
+            headers: { "content-type": "application/json" },
+            body: JSON.stringify({ identifier: secondGuardian.user.username }),
+          },
+        ),
+        { params: Promise.resolve({ id: profile.id }) },
+      );
+      expect(response.status).toBe(201);
+      return (await response.json()).data;
+    };
+
+    const pending = await invite();
+    const withdrawn = await revokeGuardian(
+      new NextRequest(
+        `http://localhost/api/managed-profiles/${profile.id}/guardians/${pending.id}`,
+        { method: "DELETE" },
+      ),
+      { params: Promise.resolve({ id: profile.id, grantId: pending.id }) },
+    );
+    expect(withdrawn.status).toBe(200);
+    expect(
+      await getPrismaClient().accountGrant.findUniqueOrThrow({
+        where: { id: pending.id },
+      }),
+    ).toMatchObject({ acceptedAt: null, revokedAt: expect.any(Date) });
+
+    const replacement = await invite();
+    expect(replacement.id).not.toBe(pending.id);
+    expect(replacement.acceptedAt).toBeNull();
+  });
+
+  it("refuses a managed profile as a Guardian invitee", async () => {
+    const creator = await createFreshMfaUser("creator");
+    cookieJar.set("healthlog_session", creator.sessionId);
+    const { profile } = await createManagedProfile({
+      creatorId: creator.user.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const { profile: managedInvitee } = await createManagedProfile({
+      creatorId: creator.user.id,
+      displayName: "Another managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const { POST: inviteGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/route");
+
+    const response = await inviteGuardian(
+      new NextRequest(
+        `http://localhost/api/managed-profiles/${profile.id}/guardians`,
+        {
+          method: "POST",
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({ identifier: managedInvitee.username }),
+        },
+      ),
+      { params: Promise.resolve({ id: profile.id }) },
+    );
+    expect(response.status).toBe(422);
+    expect(
+      await getPrismaClient().accountGrant.count({
+        where: { grantorId: profile.id },
+      }),
+    ).toBe(1);
+  });
+
+  it("rolls Guardian invitations back when their audit entry fails", async () => {
+    const creator = await createFreshMfaUser("creator");
+    const secondGuardian = await createFreshMfaUser("second-guardian");
+    cookieJar.set("healthlog_session", creator.sessionId);
+    const { profile } = await createManagedProfile({
+      creatorId: creator.user.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const prisma = getPrismaClient();
+    await prisma.$executeRawUnsafe(
+      "CREATE FUNCTION fail_managed_guardian_audit() RETURNS trigger LANGUAGE plpgsql AS $$ BEGIN IF NEW.action = 'managed_profile.guardian.invited' THEN RAISE EXCEPTION 'managed Guardian audit failure'; END IF; RETURN NEW; END; $$",
+    );
+    await prisma.$executeRawUnsafe(
+      "CREATE TRIGGER managed_guardian_audit_failure BEFORE INSERT ON audit_logs FOR EACH ROW EXECUTE FUNCTION fail_managed_guardian_audit()",
+    );
+    const { POST: inviteGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/route");
+
+    const response = await inviteGuardian(
+      new NextRequest(
+        `http://localhost/api/managed-profiles/${profile.id}/guardians`,
+        {
+          method: "POST",
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({ identifier: secondGuardian.user.username }),
+        },
+      ),
+      { params: Promise.resolve({ id: profile.id }) },
+    );
+    expect(response.status).toBe(500);
+    expect(
+      await prisma.accountGrant.count({ where: { grantorId: profile.id } }),
+    ).toBe(1);
+  });
+
+  it("rolls active Guardian revocation back when its audit entry fails", async () => {
+    const { creator, profile, secondGuardian, secondGrant } =
+      await createTwoGuardians();
+    cookieJar.set("healthlog_session", creator.sessionId);
+    await getPrismaClient().session.update({
+      where: { id: secondGuardian.sessionId },
+      data: { actingAsUserId: profile.id },
+    });
+    const prisma = getPrismaClient();
+    await prisma.$executeRawUnsafe(
+      "CREATE FUNCTION fail_managed_guardian_audit() RETURNS trigger LANGUAGE plpgsql AS $$ BEGIN IF NEW.action = 'managed_profile.guardian.revoked' THEN RAISE EXCEPTION 'managed Guardian audit failure'; END IF; RETURN NEW; END; $$",
+    );
+    await prisma.$executeRawUnsafe(
+      "CREATE TRIGGER managed_guardian_audit_failure BEFORE INSERT ON audit_logs FOR EACH ROW EXECUTE FUNCTION fail_managed_guardian_audit()",
+    );
+    const { DELETE: revokeGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/[grantId]/route");
+
+    const response = await revokeGuardian(
+      new NextRequest(
+        `http://localhost/api/managed-profiles/${profile.id}/guardians/${secondGrant.id}`,
+        { method: "DELETE" },
+      ),
+      { params: Promise.resolve({ id: profile.id, grantId: secondGrant.id }) },
+    );
+    expect(response.status).toBe(500);
+    expect(
+      await prisma.accountGrant.findUniqueOrThrow({
+        where: { id: secondGrant.id },
+      }),
+    ).toMatchObject({ revokedAt: null });
+    expect(
+      await prisma.session.findUniqueOrThrow({
+        where: { id: secondGuardian.sessionId },
+      }),
+    ).toMatchObject({ actingAsUserId: profile.id });
+  });
+
+  it("rolls managed Guardian acceptance back when the grant update fails", async () => {
+    const creator = await signInWithFreshMfa();
+    const secondGuardian = await makeAdult("second-guardian");
+    const { profile } = await createManagedProfile({
+      creatorId: creator.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const expiresAt = new Date(Date.now() + 60 * 60 * 1000);
+    const invitation = await inviteGrant({
+      grantorId: profile.id,
+      granteeId: secondGuardian.id,
+      access: "MANAGE",
+      scope: null,
+      expiresAt,
+    });
+    const prisma = getPrismaClient();
+    await prisma.$executeRawUnsafe(
+      "CREATE FUNCTION fail_managed_profile_acceptance() RETURNS trigger LANGUAGE plpgsql AS $$ BEGIN IF NEW.accepted_at IS NOT NULL AND OLD.accepted_at IS NULL THEN RAISE EXCEPTION 'managed profile acceptance failure'; END IF; RETURN NEW; END; $$",
+    );
+    await prisma.$executeRawUnsafe(
+      'CREATE TRIGGER managed_profile_acceptance_failure BEFORE UPDATE ON "account_grants" FOR EACH ROW EXECUTE FUNCTION fail_managed_profile_acceptance()',
+    );
+
+    await expect(
+      acceptGrant({ grantId: invitation.id, granteeId: secondGuardian.id }),
+    ).rejects.toThrow("managed profile acceptance failure");
+    expect(
+      await prisma.accountGrant.findUniqueOrThrow({
+        where: { id: invitation.id },
+      }),
+    ).toMatchObject({ acceptedAt: null, expiresAt });
+    expect(
+      await prisma.user.findUniqueOrThrow({ where: { id: profile.id } }),
+    ).toMatchObject({ managedProfileAt: expect.any(Date) });
+  });
+
+  it("serializes Guardian acceptance against marker clearing", async () => {
+    const creator = await signInWithFreshMfa();
+    const secondGuardian = await makeAdult("second-guardian");
+    const { profile } = await createManagedProfile({
+      creatorId: creator.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const expiresAt = new Date(Date.now() + 60 * 60 * 1000);
+    const invitation = await inviteGrant({
+      grantorId: profile.id,
+      granteeId: secondGuardian.id,
+      access: "MANAGE",
+      scope: null,
+      expiresAt,
+    });
+
+    await Promise.all([
+      acceptGrant({ grantId: invitation.id, granteeId: secondGuardian.id }),
+      clearManagedProfileMarker({ profileId: profile.id }),
+    ]);
+
+    const [profileAfter, grantAfter] = await Promise.all([
+      getPrismaClient().user.findUniqueOrThrow({ where: { id: profile.id } }),
+      getPrismaClient().accountGrant.findUniqueOrThrow({
+        where: { id: invitation.id },
+      }),
+    ]);
+    expect(profileAfter.managedProfileAt).toBeNull();
+    expect(grantAfter.acceptedAt).toEqual(expect.any(Date));
+    expect([null, expiresAt.getTime()]).toContain(
+      grantAfter.expiresAt?.getTime() ?? null,
+    );
+  });
+
+  it("refuses to delete a Guardian account when it would leave a managed profile behind", async () => {
+    const guardian = await signInWithFreshMfa();
+    const { profile } = await createManagedProfile({
+      creatorId: guardian.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const { DELETE } = await import("@/app/api/settings/account/route");
+
+    const response = await DELETE(
+      new NextRequest("http://localhost/api/settings/account", {
+        method: "DELETE",
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({ confirm: "DELETE_ACCOUNT" }),
+      }),
+    );
+    expect(response.status).toBe(409);
+    expect(
+      await getPrismaClient().user.findUnique({ where: { id: guardian.id } }),
+    ).not.toBeNull();
+    expect(
+      await getPrismaClient().user.findUnique({ where: { id: profile.id } }),
+    ).not.toBeNull();
+  });
+
+  it("preserves account, session, and audit rows when last-Guardian deletion is refused", async () => {
+    const guardian = await signInWithFreshMfa();
+    const prisma = getPrismaClient();
+    await createManagedProfile({
+      creatorId: guardian.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    await prisma.auditLog.create({
+      data: { action: "test.before.guardian.refusal", userId: guardian.id },
+    });
+    const [sessionsBefore, auditsBefore] = await Promise.all([
+      prisma.session.count({ where: { userId: guardian.id } }),
+      prisma.auditLog.count({ where: { userId: guardian.id } }),
+    ]);
+    const { DELETE } = await import("@/app/api/settings/account/route");
+
+    const response = await DELETE(
+      new NextRequest("http://localhost/api/settings/account", {
+        method: "DELETE",
+        headers: { "content-type": "application/json" },
+        body: JSON.stringify({ confirm: "DELETE_ACCOUNT" }),
+      }),
+    );
+    expect(response.status).toBe(409);
+    await expect(
+      Promise.all([
+        prisma.session.count({ where: { userId: guardian.id } }),
+        prisma.auditLog.count({ where: { userId: guardian.id } }),
+        prisma.auditLog.count({
+          where: { userId: guardian.id, action: "user.account.delete" },
+        }),
+      ]),
+    ).resolves.toEqual([sessionsBefore, auditsBefore, 0]);
+  });
+
+  it("deletes a managed profile through its fresh-MFA Guardian route", async () => {
+    const guardian = await signInWithFreshMfa();
+    const { profile } = await createManagedProfile({
+      creatorId: guardian.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+
+    const { DELETE } = await import("@/app/api/managed-profiles/[id]/route");
+    const response = await DELETE(
+      new NextRequest(`http://localhost/api/managed-profiles/${profile.id}`, {
+        method: "DELETE",
+      }),
+      { params: Promise.resolve({ id: profile.id }) },
+    );
+    expect(response.status).toBe(200);
+    expect(
+      await getPrismaClient().user.findUnique({ where: { id: profile.id } }),
+    ).toBeNull();
+  });
+
+  it("rolls profile deletion back when its audit entry fails", async () => {
+    const guardian = await signInWithFreshMfa();
+    const { profile } = await createManagedProfile({
+      creatorId: guardian.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+    const prisma = getPrismaClient();
+    await prisma.$executeRawUnsafe(
+      "CREATE FUNCTION fail_managed_profile_delete_audit() RETURNS trigger LANGUAGE plpgsql AS $$ BEGIN IF NEW.action = 'managed_profile.deleted' THEN RAISE EXCEPTION 'managed profile deletion audit failure'; END IF; RETURN NEW; END; $$",
+    );
+    await prisma.$executeRawUnsafe(
+      "CREATE TRIGGER managed_profile_delete_audit_failure BEFORE INSERT ON audit_logs FOR EACH ROW EXECUTE FUNCTION fail_managed_profile_delete_audit()",
+    );
+    const { DELETE } = await import("@/app/api/managed-profiles/[id]/route");
+
+    const response = await DELETE(
+      new NextRequest(`http://localhost/api/managed-profiles/${profile.id}`, {
+        method: "DELETE",
+      }),
+      { params: Promise.resolve({ id: profile.id }) },
+    );
+    expect(response.status).toBe(500);
+    expect(
+      await prisma.user.findUnique({ where: { id: profile.id } }),
+    ).not.toBeNull();
+    expect(
+      await prisma.accountGrant.count({ where: { grantorId: profile.id } }),
+    ).toBe(1);
+  });
+
+  it("serializes a Guardian renunciation against that Guardian's account deletion", async () => {
+    const { profile, secondGuardian, secondGrant } = await createTwoGuardians();
+    const { POST: renounce } =
+      await import("@/app/api/account/grants/[id]/renounce/route");
+    const { DELETE: deleteAccount } =
+      await import("@/app/api/settings/account/route");
+    queuedSessionIds.push(
+      secondGuardian.sessionId,
+      secondGuardian.sessionId,
+      secondGuardian.sessionId,
+    );
+
+    const [renounced, deleted] = await Promise.all([
+      renounce(
+        new NextRequest(
+          `http://localhost/api/account/grants/${secondGrant.id}/renounce`,
+          { method: "POST" },
+        ),
+        { params: Promise.resolve({ id: secondGrant.id }) },
+      ),
+      deleteAccount(
+        new NextRequest("http://localhost/api/settings/account", {
+          method: "DELETE",
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({ confirm: "DELETE_ACCOUNT" }),
+        }),
+      ),
+    ]);
+
+    expect([200, 404]).toContain(renounced.status);
+    expect(deleted.status).toBe(200);
+    await expect(
+      Promise.all([
+        getPrismaClient().user.findUnique({
+          where: { id: secondGuardian.user.id },
+        }),
+        getPrismaClient().session.count({
+          where: { userId: secondGuardian.user.id },
+        }),
+        getPrismaClient().accountGrant.count({
+          where: {
+            grantorId: profile.id,
+            access: "MANAGE",
+            acceptedAt: { not: null },
+            revokedAt: null,
+          },
+        }),
+      ]),
+    ).resolves.toEqual([null, 0, 1]);
+  });
+
+  it("serializes a Guardian renunciation against managed profile deletion", async () => {
+    const { creator, profile, secondGuardian, secondGrant } =
+      await createTwoGuardians();
+    const { POST: renounce } =
+      await import("@/app/api/account/grants/[id]/renounce/route");
+    const { DELETE: deleteProfile } =
+      await import("@/app/api/managed-profiles/[id]/route");
+    queuedSessionIds.push(secondGuardian.sessionId, creator.sessionId);
+
+    const [renounced, deleted] = await Promise.all([
+      renounce(
+        new NextRequest(
+          `http://localhost/api/account/grants/${secondGrant.id}/renounce`,
+          { method: "POST" },
+        ),
+        { params: Promise.resolve({ id: secondGrant.id }) },
+      ),
+      deleteProfile(
+        new NextRequest(`http://localhost/api/managed-profiles/${profile.id}`, {
+          method: "DELETE",
+        }),
+        { params: Promise.resolve({ id: profile.id }) },
+      ),
+    ]);
+
+    expect([200, 404]).toContain(renounced.status);
+    expect(deleted.status).toBe(200);
+    await expect(
+      Promise.all([
+        getPrismaClient().user.findUnique({ where: { id: profile.id } }),
+        getPrismaClient().accountGrant.count({
+          where: { grantorId: profile.id },
+        }),
+        getPrismaClient().auditLog.count({
+          where: {
+            userId: creator.user.id,
+            action: "managed_profile.deleted",
+          },
+        }),
+      ]),
+    ).resolves.toEqual([null, 0, 1]);
+  });
+
+  it("serializes a Guardian revocation route against internal marker clearing", async () => {
+    const { creator, profile, secondGrant } = await createTwoGuardians();
+    const { DELETE: revokeGuardian } =
+      await import("@/app/api/managed-profiles/[id]/guardians/[grantId]/route");
+    queuedSessionIds.push(creator.sessionId);
+
+    const [revoked] = await Promise.all([
+      revokeGuardian(
+        new NextRequest(
+          `http://localhost/api/managed-profiles/${profile.id}/guardians/${secondGrant.id}`,
+          { method: "DELETE" },
+        ),
+        {
+          params: Promise.resolve({ id: profile.id, grantId: secondGrant.id }),
+        },
+      ),
+      clearManagedProfileMarker({ profileId: profile.id }),
+    ]);
+
+    expect([200, 404]).toContain(revoked.status);
+    const [profileAfter, grantAfter] = await Promise.all([
+      getPrismaClient().user.findUniqueOrThrow({ where: { id: profile.id } }),
+      getPrismaClient().accountGrant.findUniqueOrThrow({
+        where: { id: secondGrant.id },
+      }),
+    ]);
+    expect(profileAfter.managedProfileAt).toBeNull();
+    expect([null, "GRANTOR"]).toContain(grantAfter.revokedBy);
+  });
+
+  it("keeps marker clearing internal while stopping managed behavior", async () => {
+    const guardian = await signInWithFreshMfa();
+    const { profile } = await createManagedProfile({
+      creatorId: guardian.id,
+      displayName: "Managed profile",
+      dateOfBirth: null,
+      locale: "en",
+      timezone: "UTC",
+    });
+
+    await clearManagedProfileMarker({ profileId: profile.id });
+    const cleared = await getPrismaClient().user.findUniqueOrThrow({
+      where: { id: profile.id },
+    });
+    expect(cleared.managedProfileAt).toBeNull();
+    await expect(
+      clearManagedProfileMarker({ profileId: "missing-profile" }),
+    ).rejects.toBeInstanceOf(ManagedProfileLifecycleError);
+  });
+});
diff --git a/tests/integration/mock-next-headers.ts b/tests/integration/mock-next-headers.ts
index e2acd04f0..edce8a7cc 100644
--- a/tests/integration/mock-next-headers.ts
+++ b/tests/integration/mock-next-headers.ts
@@ -18,3 +18,9 @@
  */
 export const cookieJar = new Map<string, string>();
 export const headerJar = new Map<string, string>();
+
+/**
+ * Session snapshots for invoking concurrent route handlers as different users.
+ * A request consumes one entry when its mocked cookie store is created.
+ */
+export const queuedSessionIds: string[] = [];