diff --git a/db/services/user-profile.ts b/db/services/user-profile.ts
index f9fe1bb4..b71eba51 100644
--- a/db/services/user-profile.ts
+++ b/db/services/user-profile.ts
@@ -48,13 +48,25 @@ export async function patchUserProfile(
   input: UserProfilePatch
 ) {
   const patch = userProfilePatchSchema.parse(input);
-  const profile = parseUserProfile({
-    ...(await readUserProfile(scope)),
-    ...patch,
-  });
+  if (patch.countryCode) patch.countryCode = patch.countryCode.toUpperCase();
   await ensureScope(scope);
-  await writeUserProfile(scope, profile);
-  return profile;
+  const updatedAt = new Date();
+  // A field patch must not replace values read before another conversation's update.
+  const [profile] = await db
+    .insert(userProfiles)
+    .values({
+      ...emptyUserProfile,
+      ...patch,
+      updatedAt,
+      workspaceId: scope.workspaceId,
+    })
+    .onConflictDoUpdate({
+      target: userProfiles.workspaceId,
+      set: { ...patch, updatedAt },
+    })
+    .returning(selection);
+  if (!profile) throw new Error("Personal Info could not be updated.");
+  return parseUserProfile(profile);
 }
 
 async function writeUserProfile(scope: AccessScope, profile: UserProfile) {
diff --git a/tests/agent/profile-concurrency.test.ts b/tests/agent/profile-concurrency.test.ts
new file mode 100644
index 00000000..dd818060
--- /dev/null
+++ b/tests/agent/profile-concurrency.test.ts
@@ -0,0 +1,148 @@
+import { PGlite } from "@electric-sql/pglite";
+import { drizzle } from "drizzle-orm/pglite";
+import { migrate } from "drizzle-orm/pglite/migrator";
+import type { MemoryToolsContext } from "eve/memory";
+import {
+  afterAll,
+  beforeAll,
+  beforeEach,
+  describe,
+  expect,
+  it,
+  vi,
+} from "vitest";
+import * as Database from "@db";
+import * as schema from "@db/schema";
+import {
+  patchUserProfile,
+  readUserProfile,
+  replaceUserProfile,
+} from "@db/services/user-profile";
+import personalInfoMemory from "@agent/memory/personal_info";
+import { accessScopeForUser } from "@shared/identity/access-scope";
+import { emptyUserProfile } from "@shared/user-profile/schema";
+import { toolContextFor } from "@tests/helpers/tool-context";
+
+const client = new PGlite();
+const database = drizzle(client, { schema });
+const scope = accessScopeForUser("profile-fixture");
+
+beforeAll(async () => {
+  await migrate(database, { migrationsFolder: "db/migrations" });
+  // SAFETY: PGlite supplies the real Drizzle query-builder contract used by the service; only the database driver changes.
+  // oxlint-disable-next-line typescript/no-unsafe-type-assertion -- Exercise the real migrations and service against an isolated PostgreSQL-compatible database.
+  vi.spyOn(Database, "db", "get").mockReturnValue(database as never);
+}, 20_000);
+
+beforeEach(async () => {
+  await database.delete(schema.workspaces);
+});
+
+afterAll(async () => {
+  vi.restoreAllMocks();
+  await client.close();
+});
+
+describe("Personal Info field updates", () => {
+  it("preserves unrelated fields when two conversations update an existing profile", async () => {
+    await replaceUserProfile(scope, { ...emptyUserProfile, firstName: "Ada" });
+    const firstTools = await personalInfoMemory.provider.tools(
+      memoryContext("city-session")
+    );
+    const secondTools = await personalInfoMemory.provider.tools(
+      memoryContext("region-session")
+    );
+    if (!firstTools || !secondTools)
+      throw new Error("Expected the interactive profile update tool.");
+    await Promise.all([
+      firstTools.update.execute(
+        { city: "London" },
+        toolContextFor({ callId: "city", sessionId: "city-session" })
+      ),
+      secondTools.update.execute(
+        { region: "Greater London" },
+        toolContextFor({ callId: "region", sessionId: "region-session" })
+      ),
+    ]);
+    expect(await readUserProfile(scope)).toMatchObject({
+      city: "London",
+      firstName: "Ada",
+      region: "Greater London",
+    });
+  });
+
+  it("preserves both fields when concurrent patches create the first profile", async () => {
+    await Promise.all([
+      patchUserProfile(scope, { firstName: "Ada" }),
+      patchUserProfile(scope, { lastName: "Lovelace" }),
+    ]);
+    expect(await readUserProfile(scope)).toMatchObject({
+      firstName: "Ada",
+      lastName: "Lovelace",
+    });
+  });
+
+  it("normalizes values and removes only an explicitly cleared field", async () => {
+    await replaceUserProfile(scope, {
+      ...emptyUserProfile,
+      city: "London",
+      firstName: "Ada",
+    });
+    expect(
+      await patchUserProfile(scope, { countryCode: " gb ", firstName: null })
+    ).toMatchObject({
+      city: "London",
+      countryCode: "GB",
+      firstName: null,
+    });
+  });
+
+  it("creates a normalized profile without changing replacement semantics", async () => {
+    expect(
+      await patchUserProfile(scope, { firstName: " Ada ", countryCode: "gb" })
+    ).toMatchObject({
+      countryCode: "GB",
+      firstName: "Ada",
+      lastName: null,
+    });
+    expect(
+      await replaceUserProfile(scope, {
+        ...emptyUserProfile,
+        lastName: "Lovelace",
+      })
+    ).toMatchObject({
+      countryCode: null,
+      firstName: null,
+      lastName: "Lovelace",
+    });
+  });
+});
+
+function memoryContext(sessionId: string): MemoryToolsContext {
+  return {
+    channel: {},
+    memory: {
+      scope: {
+        key: "profile-key",
+        namespace: "openinstinct-personal-info-v1",
+        value: scope.workspaceId,
+      },
+      slot: "personal_info",
+    },
+    messages: [],
+    model: null,
+    session: {
+      auth: {
+        current: {
+          attributes: { workspaceId: scope.workspaceId },
+          authenticator: "fixture",
+          principalId: scope.userId,
+          principalType: "user",
+        },
+        initiator: null,
+      },
+      id: sessionId,
+    },
+    turn: { id: "profile-turn", input: [], sequence: 1 },
+  };
+}