diff --git a/packages/api/src/auth/dev-login.test.ts b/packages/api/src/auth/dev-login.test.ts
index 4230d2af..9ad43930 100644
--- a/packages/api/src/auth/dev-login.test.ts
+++ b/packages/api/src/auth/dev-login.test.ts
@@ -25,6 +25,10 @@ mock.module('@proxy/db/user', () => ({
 
 mock.module('../orgs/provision', () => ({signUp: createUser}));
 
+const markOwnedOrganizationsInsider = mock();
+
+mock.module('@proxy/db/organization', () => ({markOwnedOrganizationsInsider}));
+
 mock.module('../observability/log', () => ({
 	log: {debug: mock(), info: mock(), warn: mock(), error: mock()},
 	serializeError: mock(() => ({})),
@@ -61,6 +65,7 @@ beforeEach(() => {
 	getUserByEmail.mockResolvedValue(Ok(null));
 	createUser.mockResolvedValue(Ok(devUser));
 	createSession.mockResolvedValue(Ok(undefined));
+	markOwnedOrganizationsInsider.mockResolvedValue(Ok(undefined));
 });
 
 describe('handleDevLoginRoute', () => {
@@ -86,6 +91,7 @@ describe('handleDevLoginRoute', () => {
 		expect(createUserArgs.email).toBe('dev@dev.proxy.local');
 		expect(createUserArgs.name).toBe('Dev User');
 		expect(createUserArgs.emailVerified).toBeInstanceOf(Date);
+		expect(markOwnedOrganizationsInsider).toHaveBeenCalledWith(devUser.id);
 
 		const sessionArgs = createSession.mock.calls[0]?.[0] as {tokenHash: string; userId: string; expires: Date};
 		expect(sessionArgs.userId).toBe(devUser.id);
@@ -115,6 +121,7 @@ describe('handleDevLoginRoute', () => {
 		await handleDevLoginRoute({body: {}, headers: {}} as never, res as never);
 
 		expect(createUser).not.toHaveBeenCalled();
+		expect(markOwnedOrganizationsInsider).toHaveBeenCalledWith(devUser.id);
 		const sessionArgs = createSession.mock.calls[0]?.[0] as {userId: string};
 		expect(sessionArgs.userId).toBe(devUser.id);
 		expect(res.json).toHaveBeenCalledWith({ok: true});
@@ -130,6 +137,7 @@ describe('handleDevLoginRoute', () => {
 		expect(getUserByEmail).not.toHaveBeenCalled();
 		const createUserArgs = createUser.mock.calls[0]?.[0] as {email: string};
 		expect(createUserArgs.email).toMatch(/^dev-[0-9a-f]{16}@dev\.proxy\.local$/);
+		expect(markOwnedOrganizationsInsider).not.toHaveBeenCalled();
 		const sessionArgs = createSession.mock.calls[0]?.[0] as {userId: string};
 		expect(sessionArgs.userId).toBe(throwawayUser.id);
 	});
@@ -160,6 +168,19 @@ describe('handleDevLoginRoute', () => {
 		expect(res.cookies).toHaveLength(0);
 	});
 
+	test('insider marking failure → 500, no session', async () => {
+		getUserByEmail.mockResolvedValue(Ok(devUser));
+		markOwnedOrganizationsInsider.mockResolvedValue(Err(ApiErr.dbError(new Error('boom'))));
+
+		const {handleDevLoginRoute} = await import('./dev-login');
+		const res = makeRes();
+		await handleDevLoginRoute({body: {}, headers: {}} as never, res as never);
+
+		expect(res.status).toHaveBeenCalledWith(500);
+		expect(res.json).toHaveBeenCalledWith({error: 'user_creation_failed'});
+		expect(createSession).not.toHaveBeenCalled();
+	});
+
 	test('session creation failure → 500, no cookie', async () => {
 		createSession.mockResolvedValue(Err(ApiErr.dbError(new Error('boom'))));
 
diff --git a/packages/api/src/auth/dev-login.ts b/packages/api/src/auth/dev-login.ts
index 44302722..68501e79 100644
--- a/packages/api/src/auth/dev-login.ts
+++ b/packages/api/src/auth/dev-login.ts
@@ -3,8 +3,9 @@ import {randomBytes} from 'node:crypto';
 import type {Request, Response} from 'express';
 import {Ok, type Result} from 'ts-results-es';
 
+import {markOwnedOrganizationsInsider} from '@proxy/db/organization';
 import {type CreatedUser, getUserByEmail} from '@proxy/db/user';
-import type {ApiError} from '@proxy/utils';
+import {type ApiError, Do} from '@proxy/utils';
 
 import {log} from '../observability/log';
 import {signUp} from '../orgs/provision';
@@ -17,7 +18,9 @@ const DEV_USER_EMAIL = `dev@${DEV_USER_EMAIL_DOMAIN}`;
 
 /**
  * `POST /auth/dev/login` — signs the browser in as the dev user, made on its first sign-in and the
- * same one every time after, skipping Google and the magic link. With `{fresh: true}` it makes a
+ * same one every time after, skipping Google and the magic link. Every organization the dev user
+ * owns is made an insider on each sign-in, so it has every experiment and its personas' model to
+ * choose, one made since too. With `{fresh: true}` it makes a
  * throwaway user instead, whose organization still has the welcome flow ahead of it, as the screen
  * map's crawl needs. Any NODE_ENV but development gets a 404, as if the route did not exist.
  */
@@ -48,6 +51,14 @@ export async function handleDevLoginRoute(req: Request, res: Response): Promise<
 }
 
 async function findOrCreateDevUser(): Promise<Result<CreatedUser, ApiError>> {
+	return Do(async ($) => {
+		const user = $(await getOrSignUpDevUser());
+		$(await markOwnedOrganizationsInsider(user.id));
+		return user;
+	});
+}
+
+async function getOrSignUpDevUser(): Promise<Result<CreatedUser, ApiError>> {
 	const existing = await getUserByEmail(DEV_USER_EMAIL);
 	if (existing.isErr()) {
 		return existing;
diff --git a/packages/db/src/organization.ts b/packages/db/src/organization.ts
index 6ad95439..bcdf0edc 100644
--- a/packages/db/src/organization.ts
+++ b/packages/db/src/organization.ts
@@ -456,3 +456,17 @@ export async function markOrganizationOnboarded(orgId: string): Promise<Result<v
 		)
 	).map(() => undefined);
 }
+
+/** Makes every organization the person owns an insider; development's dev sign-in, never the app's. */
+export async function markOwnedOrganizationsInsider(
+	userId: string,
+): Promise<Result<void, ApiError>> {
+	return (
+		await wrapDb(() =>
+			db.organization.updateMany({
+				where: {ownerUserId: userId, insider: false},
+				data: {insider: true},
+			}),
+		)
+	).map(() => undefined);
+}