diff --git a/src/backend/clients/event/types.ts b/src/backend/clients/event/types.ts
index ed24e5d43..a572fbb50 100644
--- a/src/backend/clients/event/types.ts
+++ b/src/backend/clients/event/types.ts
@@ -227,8 +227,40 @@ export type EventMap = {
         fingerprint?: string | null;
         /** True when the created account is a temp user (no email/password). */
         is_temp?: boolean;
+        /** The bonus code `puter.signup-bonus.validate` accepted, if any. */
+        bonus_code?: string;
         [key: string]: unknown;
     };
+    // Signup bonus codes are pure mechanism here: an extension decides what a
+    // code is worth and fills these in (both emitted via `emitAndWait`).
+    'puter.signup-bonus.check': {
+        code: string;
+        ip: string | null;
+        fingerprint: string | null;
+        valid: boolean;
+        /** Opaque to core; forwarded to the client when `valid` is false. */
+        reason: string | null;
+        display: { title: string; description: string } | null;
+        /** Verification the code will require after signup. */
+        requirements: { phone: boolean; card: boolean } | null;
+    };
+    /**
+     * Emitted once a signup has passed `puter.signup.validate`, so listeners
+     * see the harness's verdict. A listener sets `accepted` to honor the code,
+     * and may raise (never lower) the verification requirements.
+     */
+    'puter.signup-bonus.validate': {
+        code: string;
+        email?: string;
+        clean_email?: string;
+        ip?: string | null;
+        fingerprint?: string | null;
+        reputation?: number | null;
+        source?: 'oidc';
+        requires_phone_verification: boolean;
+        requires_card_verification: boolean;
+        accepted: boolean;
+    };
     'email.validate': {
         email: string;
         allow: boolean;
diff --git a/src/backend/controllers/auth/AuthController.signupBonus.test.ts b/src/backend/controllers/auth/AuthController.signupBonus.test.ts
new file mode 100644
index 000000000..4eec946c3
--- /dev/null
+++ b/src/backend/controllers/auth/AuthController.signupBonus.test.ts
@@ -0,0 +1,413 @@
+/*
+ * Copyright (C) 2024-present Puter Technologies Inc.
+ *
+ * This file is part of Puter.
+ *
+ * Puter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Signup bonus codes through the real controller: the check route, the signup
+ * hand-off to `puter.signup-bonus.validate`, and the awaited
+ * `user.card-verified` a grant on card verification depends on. Tests stand in
+ * for the extension with shared listeners (EventClient has no `off()`).
+ */
+
+import { afterAll, afterEach, beforeAll, describe, expect, it } from 'vitest';
+import type { Actor } from '../../core/actor.js';
+import type { EventMap } from '../../clients/event/types.js';
+import type { PuterServer } from '../../server.js';
+import { setupTestServer } from '../../testUtil.js';
+
+let server: PuterServer;
+let controller: any;
+
+type Handler<K extends keyof EventMap> = ((data: EventMap[K]) => void) | null;
+
+let onBonusCheck: Handler<'puter.signup-bonus.check'> = null;
+let onBonusValidate: Handler<'puter.signup-bonus.validate'> = null;
+let onSignupValidate: ((data: Record<string, unknown>) => void) | null = null;
+let onCardConfirm: ((data: Record<string, unknown>) => void) | null = null;
+let onCardVerified: (() => Promise<void>) | null = null;
+const heardSignupSuccess: Array<Record<string, unknown>> = [];
+
+beforeAll(async () => {
+    server = await setupTestServer();
+    controller = server.controllers.auth;
+    const events = server.clients.event;
+    events.on('puter.signup-bonus.check', (_k, data) => onBonusCheck?.(data));
+    events.on('puter.signup-bonus.validate', (_k, data) =>
+        onBonusValidate?.(data),
+    );
+    events.on('puter.signup.validate', (_k, data) =>
+        onSignupValidate?.(data as Record<string, unknown>),
+    );
+    events.on('puter.signup.success', (_k, data) => {
+        heardSignupSuccess.push(data as Record<string, unknown>);
+    });
+    events.on('puter.card-verification.confirm', (_k, data) =>
+        onCardConfirm?.(data as Record<string, unknown>),
+    );
+    events.on('user.card-verified' as never, async () => {
+        await onCardVerified?.();
+    });
+});
+
+afterAll(async () => {
+    await server?.shutdown();
+});
+
+afterEach(() => {
+    onBonusCheck = null;
+    onBonusValidate = null;
+    onSignupValidate = null;
+    onCardConfirm = null;
+    onCardVerified = null;
+});
+
+const uniq = () => Math.random().toString(36).slice(2, 10);
+
+/** A check listener that finds the code open, as an extension would. */
+const openCheck: Handler<'puter.signup-bonus.check'> = (data) => {
+    data.valid = true;
+    data.display = { title: 'T', description: 'D' };
+};
+
+const makeReq = (
+    body: Record<string, unknown> = {},
+    extra: { actor?: Actor; ip?: string } = {},
+) => ({
+    body,
+    headers: {},
+    connection: { remoteAddress: extra.ip ?? '127.0.0.1' },
+    socket: { remoteAddress: extra.ip ?? '127.0.0.1' },
+    ip: extra.ip ?? '127.0.0.1',
+    params: {},
+    actor: extra.actor,
+});
+
+const makeRes = () => {
+    const res = {
+        statusCode: 200,
+        body: undefined as unknown,
+        status(code: number) {
+            this.statusCode = code;
+            return this;
+        },
+        json(b: unknown) {
+            this.body = b;
+            return this;
+        },
+        cookie() {
+            return this;
+        },
+        clearCookie() {
+            return this;
+        },
+        send() {
+            return this;
+        },
+        end() {
+            return this;
+        },
+    };
+    return res;
+};
+
+const signupBody = (extra: Record<string, unknown> = {}) => {
+    const username = `b_${uniq()}`;
+    return {
+        username,
+        email: `${username}@test.local`,
+        password: 'correct-horse-battery',
+        ...extra,
+    };
+};
+
+const signup = async (body: Record<string, unknown>) => {
+    const res = makeRes();
+    await controller.handleSignup(makeReq(body), res);
+    return res;
+};
+
+const findUser = (username: unknown) =>
+    server.stores.user.getByUsername(username as string, { force: true });
+
+/** `puter.signup.success` is fire-and-forget; wait for it to land. */
+const waitForSuccess = async (userUuid: string) => {
+    const deadline = Date.now() + 2000;
+    while (Date.now() < deadline) {
+        const hit = heardSignupSuccess.find((e) => e.user_uuid === userUuid);
+        if (hit) return hit;
+        await new Promise((r) => setTimeout(r, 10));
+    }
+    throw new Error('puter.signup.success never arrived');
+};
+
+// -- POST /signup/bonus-code/check -----------------------------------
+
+describe('AuthController.handleSignupBonusCheck', () => {
+    const check = async (body: Record<string, unknown>) => {
+        const res = makeRes();
+        await controller.handleSignupBonusCheck(makeReq(body), res);
+        return res.body;
+    };
+
+    it('answers invalid when no extension is listening', async () => {
+        expect(await check({ bonusCode: 'startup3m-abcd1234' })).toEqual({
+            valid: false,
+        });
+    });
+
+    it('returns the display and requirements a listener fills in', async () => {
+        let seen: EventMap['puter.signup-bonus.check'] | null = null;
+        onBonusCheck = (data) => {
+            seen = { ...data };
+            data.valid = true;
+            data.display = { title: '3 months of Basic', description: 'Free' };
+            data.requirements = { phone: true, card: false };
+        };
+        expect(
+            await check({
+                bonusCode: 'Startup3M-ABCD1234',
+                fingerprint: 'fp1',
+            }),
+        ).toEqual({
+            valid: true,
+            display: { title: '3 months of Basic', description: 'Free' },
+            requirements: { phone: true, card: false },
+        });
+        // Listeners only ever see the canonical form.
+        expect(seen).toMatchObject({
+            code: 'startup3mabcd1234',
+            fingerprint: 'fp1',
+            ip: '127.0.0.1',
+        });
+    });
+
+    it('forwards an opaque reason for a refused code', async () => {
+        onBonusCheck = (data) => {
+            data.reason = 'ended';
+        };
+        expect(await check({ bonusCode: 'startup3m-abcd1234' })).toEqual({
+            valid: false,
+            reason: 'ended',
+        });
+    });
+
+    it('treats valid without display as invalid', async () => {
+        onBonusCheck = (data) => {
+            data.valid = true;
+        };
+        expect(await check({ bonusCode: 'startup3m-abcd1234' })).toEqual({
+            valid: false,
+        });
+    });
+
+    it('answers a malformed code without consulting listeners', async () => {
+        let called = false;
+        onBonusCheck = () => {
+            called = true;
+        };
+        expect(await check({ bonusCode: 'a:b' })).toEqual({ valid: false });
+        expect(called).toBe(false);
+    });
+
+    it('400s a non-string bonusCode', async () => {
+        await expect(
+            controller.handleSignupBonusCheck(
+                makeReq({ bonusCode: 42 }),
+                makeRes(),
+            ),
+        ).rejects.toMatchObject({ statusCode: 400 });
+    });
+});
+
+// -- POST /signup with bonusCode -------------------------------------
+
+describe('AuthController.handleSignup with a bonus code', () => {
+    it('refuses the signup when nothing accepts the code', async () => {
+        const body = signupBody({ bonusCode: 'startup3m-abcd1234' });
+        await expect(signup(body)).rejects.toMatchObject({
+            statusCode: 400,
+            legacyCode: 'bonus_code_invalid',
+        });
+        expect(await findUser(body.username)).toBeFalsy();
+    });
+
+    it('refuses a dead code before the abuse gate records the attempt', async () => {
+        let validated = false;
+        onSignupValidate = () => {
+            validated = true;
+        };
+        await expect(
+            signup(signupBody({ bonusCode: 'startup3m-abcd1234' })),
+        ).rejects.toMatchObject({ legacyCode: 'bonus_code_invalid' });
+        expect(validated).toBe(false);
+    });
+
+    it('still refuses a code that passed the check but is refused after the gate', async () => {
+        onBonusCheck = openCheck;
+        const body = signupBody({ bonusCode: 'startup3m-abcd1234' });
+        await expect(signup(body)).rejects.toMatchObject({
+            legacyCode: 'bonus_code_invalid',
+        });
+        expect(await findUser(body.username)).toBeFalsy();
+    });
+
+    it('refuses a malformed code before any listener runs', async () => {
+        let called = false;
+        onBonusValidate = () => {
+            called = true;
+        };
+        await expect(
+            signup(signupBody({ bonusCode: 'nope' + '!'.repeat(3) })),
+        ).rejects.toMatchObject({ legacyCode: 'bonus_code_invalid' });
+        expect(called).toBe(false);
+    });
+
+    it('400s a non-string bonusCode', async () => {
+        await expect(
+            signup(signupBody({ bonusCode: ['startup3m'] })),
+        ).rejects.toMatchObject({ statusCode: 400, legacyCode: 'bad_request' });
+    });
+
+    it('applies the requirements an accepted code raises and reports the code', async () => {
+        onBonusCheck = openCheck;
+        let seen: EventMap['puter.signup-bonus.validate'] | null = null;
+        onBonusValidate = (data) => {
+            seen = { ...data };
+            data.accepted = true;
+            data.requires_card_verification = true;
+        };
+        const body = signupBody({
+            bonusCode: 'STARTUP6M-abcd1234',
+            fingerprint: 'fp-bonus',
+        });
+        const res = await signup(body);
+        expect(
+            (res.body as { user: Record<string, unknown> }).user,
+        ).toMatchObject({ requires_card_verification: true });
+
+        expect(seen).toMatchObject({
+            code: 'startup6mabcd1234',
+            email: body.email,
+            fingerprint: 'fp-bonus',
+            requires_phone_verification: false,
+            requires_card_verification: false,
+        });
+        const user = await findUser(body.username);
+        expect(Boolean(user!.requires_card_verification)).toBe(true);
+        expect(Boolean(user!.requires_phone_verification)).toBe(false);
+        const success = await waitForSuccess(user!.uuid);
+        expect(success.bonus_code).toBe('startup6mabcd1234');
+    });
+
+    it('keeps a requirement the abuse harness set even if the listener clears it', async () => {
+        onBonusCheck = openCheck;
+        onSignupValidate = (data) => {
+            data.requires_phone_verification = true;
+        };
+        onBonusValidate = (data) => {
+            expect(data.requires_phone_verification).toBe(true);
+            data.accepted = true;
+            data.requires_phone_verification = false;
+        };
+        const body = signupBody({ bonusCode: 'startup3m-abcd1234' });
+        await signup(body);
+        const user = await findUser(body.username);
+        expect(Boolean(user!.requires_phone_verification)).toBe(true);
+    });
+
+    it('never offers the code for a signup the abuse harness blocked', async () => {
+        onBonusCheck = openCheck;
+        let called = false;
+        onSignupValidate = (data) => {
+            data.allow = false;
+            data.message = 'Signup blocked';
+        };
+        onBonusValidate = () => {
+            called = true;
+        };
+        await expect(
+            signup(signupBody({ bonusCode: 'startup3m-abcd1234' })),
+        ).rejects.toMatchObject({ statusCode: 403 });
+        expect(called).toBe(false);
+    });
+
+    it('leaves the success event without a code when none was presented', async () => {
+        const body = signupBody();
+        await signup(body);
+        const user = await findUser(body.username);
+        const success = await waitForSuccess(user!.uuid);
+        expect(success).not.toHaveProperty('bonus_code');
+    });
+
+    it('ignores a bonus code on a temp signup', async () => {
+        let called = false;
+        onBonusValidate = () => {
+            called = true;
+        };
+        const res = makeRes();
+        await controller.handleSignup(
+            makeReq({ is_temp: true, bonusCode: 'startup3m-abcd1234' }),
+            res,
+        );
+        expect((res.body as { user: { is_temp: boolean } }).user.is_temp).toBe(
+            true,
+        );
+        expect(called).toBe(false);
+    });
+});
+
+// -- /card-verification/confirm awaits user.card-verified ------------
+
+describe('AuthController.handleCardVerificationConfirm', () => {
+    it('finishes user.card-verified listeners before responding', async () => {
+        const body = signupBody();
+        await signup(body);
+        const created = await findUser(body.username);
+        await server.stores.user.update(created!.id, {
+            requires_card_verification: 1,
+        });
+        const actor = {
+            user: {
+                id: created!.id,
+                uuid: created!.uuid,
+                username: created!.username,
+                email: created!.email ?? null,
+                email_confirmed: false,
+            },
+        } as Actor;
+
+        onCardConfirm = (data) => {
+            data.enabled = true;
+            data.verified = true;
+            data.fingerprint = 'fp_card_1';
+        };
+        let listenerDone = false;
+        onCardVerified = async () => {
+            await new Promise((r) => setTimeout(r, 30));
+            listenerDone = true;
+        };
+
+        const res = makeRes();
+        await controller.handleCardVerificationConfirm(
+            makeReq({ setup_intent_id: 'seti_1' }, { actor }),
+            res,
+        );
+        expect(res.body).toMatchObject({ card_verified: true });
+        expect(listenerDone).toBe(true);
+    });
+});
diff --git a/src/backend/controllers/auth/AuthController.ts b/src/backend/controllers/auth/AuthController.ts
index 32afce2b2..e3e11570d 100644
--- a/src/backend/controllers/auth/AuthController.ts
+++ b/src/backend/controllers/auth/AuthController.ts
@@ -76,6 +76,13 @@ import { sessionCookieFlags } from '../../util/cookieFlags.js';
 import { cleanEmail, isBlockedEmail } from '../../util/email.js';
 import { generate_identifier } from '../../util/identifier.js';
 import { parsePhone } from '../../util/phone.js';
+import {
+    bonusCodeInvalidError,
+    checkSignupBonus,
+    isAbsentBonusCode,
+    normalizeBonusCode,
+    validateSignupBonus,
+} from '../../util/signupBonus.js';
 import { isTemporaryPasswordExpired } from '../../util/temporaryPassword.js';
 import { getTaskbarItems } from '../../util/taskbarItems.js';
 import {
@@ -815,6 +822,18 @@ export class AuthController extends PuterController {
             }
         }
 
+        // Only the shape is judged here; whether the code is honored is up to
+        // `puter.signup-bonus.validate`, after the abuse checks below.
+        let bonusCode: string | null = null;
+        if (!is_temp && !isAbsentBonusCode(body.bonusCode)) {
+            if (typeof body.bonusCode !== 'string')
+                throw new HttpError(400, 'bonusCode must be a string.', {
+                    legacyCode: 'bad_request',
+                });
+            bonusCode = normalizeBonusCode(body.bonusCode);
+            if (!bonusCode) throw bonusCodeInvalidError();
+        }
+
         // Signup-disabled gate. Runs before the duplicate checks so a
         // disabled endpoint doesn't reveal which usernames or emails
         // exist. Claiming a pre-existing placeholder row is still
@@ -888,6 +907,20 @@ export class AuthController extends PuterController {
             ? null
             : await this.#resolveSignupEmailClaim(body.email);
 
+        // A dead code fails here rather than after the gate below, which records
+        // an allowed attempt against the address as if an account followed.
+        if (
+            bonusCode &&
+            !(
+                await checkSignupBonus(this.clients.event, bonusCode, {
+                    ip: clientIp,
+                    fingerprint,
+                })
+            ).valid
+        ) {
+            throw bonusCodeInvalidError();
+        }
+
         // Extension-level validation gate. Abuse-prevention extensions
         // inspect the incoming signup and can:
         //   - block it outright via `event.allow = false`
@@ -974,18 +1007,37 @@ export class AuthController extends PuterController {
         const force_email_confirmation = Boolean(
             validateEvent.requires_email_confirmation,
         );
-        const force_phone_verification =
+        let force_phone_verification =
             Boolean(validateEvent.requires_phone_verification) ||
             // Test/QA switch: force the SMS gate on every signup regardless of
             // reputation (see config.always_require_phone_verification).
             Boolean(this.config.always_require_phone_verification);
-        const force_card_verification = Boolean(
+        let force_card_verification = Boolean(
             validateEvent.requires_card_verification ||
             // Test/QA switch: force the card gate on every signup regardless of
             // reputation (see config.always_require_card_verification).
             this.config.always_require_card_verification,
         );
 
+        if (bonusCode) {
+            const verdict = await validateSignupBonus(
+                this.clients.event,
+                bonusCode,
+                {
+                    email: body.email,
+                    clean_email: cleanEmail(body.email),
+                    ip: clientIp,
+                    fingerprint,
+                    reputation: validateEvent.reputation,
+                    requires_phone_verification: force_phone_verification,
+                    requires_card_verification: force_card_verification,
+                },
+            );
+            if (!verdict.accepted) throw bonusCodeInvalidError();
+            force_phone_verification = verdict.requiresPhoneVerification;
+            force_card_verification = verdict.requiresCardVerification;
+        }
+
         // Prepare shared fields
         const user_uuid = uuidv4();
         const email_confirm_code = String(crypto.randomInt(100000, 1000000));
@@ -1206,6 +1258,7 @@ export class AuthController extends PuterController {
                     // have to agree or per-IP counters are written under one
                     // key and read under another.
                     ip: clientIp,
+                    ...(bonusCode ? { bonus_code: bonusCode } : {}),
                 } as never,
                 {},
             );
@@ -1227,6 +1280,64 @@ export class AuthController extends PuterController {
         await this.#completeLogin(req, res, user!);
     }
 
+    /**
+     * Preview a signup bonus code before the account exists, so the signup form
+     * can say what it grants. Answers only valid/invalid: an extension owns the
+     * codes, and with none installed every code is invalid.
+     */
+    @Post('/signup/bonus-code/check', {
+        rateLimit: [
+            { scope: 'signup-bonus-check', limit: 20, window: 15 * 60_000 },
+            {
+                scope: 'signup-bonus-check-ip',
+                limit: 60,
+                window: 15 * 60_000,
+                key: 'ip',
+            },
+        ],
+    })
+    async handleSignupBonusCheck(req: Request, res: Response): Promise<void> {
+        const raw = req.body?.bonusCode;
+        if (typeof raw !== 'string')
+            throw new HttpError(400, 'bonusCode must be a string.', {
+                legacyCode: 'bad_request',
+            });
+        const code = normalizeBonusCode(raw);
+        if (!code) {
+            res.json({ valid: false });
+            return;
+        }
+
+        const fingerprint =
+            typeof req.body?.fingerprint === 'string' &&
+            req.body.fingerprint.length <= FINGERPRINT_MAX_LENGTH
+                ? req.body.fingerprint
+                : null;
+        const checkEvent = await checkSignupBonus(this.clients.event, code, {
+            ip: (req.ip || req.socket?.remoteAddress || null) as string | null,
+            fingerprint,
+        });
+
+        if (checkEvent.valid !== true || !checkEvent.display) {
+            res.json({
+                valid: false,
+                ...(checkEvent.reason ? { reason: checkEvent.reason } : {}),
+            });
+            return;
+        }
+        res.json({
+            valid: true,
+            display: {
+                title: String(checkEvent.display.title),
+                description: String(checkEvent.display.description),
+            },
+            requirements: {
+                phone: checkEvent.requirements?.phone === true,
+                card: checkEvent.requirements?.card === true,
+            },
+        });
+    }
+
     // -- Logout ------------------------------------------------------
 
     @Post('/logout', {
@@ -2220,8 +2331,11 @@ export class AuthController extends PuterController {
             ...(clearedPhoneGate ? { requires_phone_verification: 0 } : {}),
         });
 
+        // Awaited like `user.phone-verified`, so whatever a listener grants on
+        // verification is in place before the client refreshes. emitAndWait
+        // swallows listener errors, so confirm never fails on one.
         try {
-            this.clients.event?.emit(
+            await this.clients.event?.emitAndWait(
                 'user.card-verified' as never,
                 {
                     user_id: user.id,
@@ -2234,7 +2348,7 @@ export class AuthController extends PuterController {
                 {},
             );
         } catch {
-            // ignore — event is a side-channel signal, not load-bearing
+            // ignore — listeners are best-effort
         }
         // Notify other tabs/devices for this user so they refresh + drop the gate.
         try {
diff --git a/src/backend/controllers/oidc/OIDCController.test.ts b/src/backend/controllers/oidc/OIDCController.test.ts
index 71944e733..04d9b9e7c 100644
--- a/src/backend/controllers/oidc/OIDCController.test.ts
+++ b/src/backend/controllers/oidc/OIDCController.test.ts
@@ -58,6 +58,10 @@ let router: PuterRouter;
 // override in and out (same pattern as AuthController.test.ts).
 type SignupValidateOverride = (data: Record<string, unknown>) => void;
 let signupValidateOverride: SignupValidateOverride | null = null;
+// Stand-in for the extension that honors signup bonus codes.
+let bonusValidateOverride: SignupValidateOverride | null = null;
+let bonusCheckOverride: SignupValidateOverride | null = null;
+const heardSignupSuccess: Array<Record<string, unknown>> = [];
 
 beforeAll(async () => {
     server = await setupTestServer({
@@ -90,6 +94,24 @@ beforeAll(async () => {
             }
         },
     );
+    server.clients.event.on(
+        'puter.signup-bonus.check',
+        (_k: unknown, data: unknown) => {
+            bonusCheckOverride?.(data as Record<string, unknown>);
+        },
+    );
+    server.clients.event.on(
+        'puter.signup-bonus.validate',
+        (_k: unknown, data: unknown) => {
+            bonusValidateOverride?.(data as Record<string, unknown>);
+        },
+    );
+    server.clients.event.on(
+        'puter.signup.success',
+        (_k: unknown, data: unknown) => {
+            heardSignupSuccess.push(data as Record<string, unknown>);
+        },
+    );
 });
 
 afterAll(async () => {
@@ -99,6 +121,8 @@ afterAll(async () => {
 afterEach(() => {
     vi.restoreAllMocks();
     signupValidateOverride = null;
+    bonusValidateOverride = null;
+    bonusCheckOverride = null;
 });
 
 interface CapturedResponse {
@@ -1965,3 +1989,143 @@ describe('OIDCController rate limits', () => {
         expect(rateLimitOf('get', '/auth/oidc/providers').limit).toBe(1_200);
     });
 });
+
+// -- Signup bonus codes ----------------------------------------------
+
+describe('OIDC signup bonus codes', () => {
+    const rand = () => Math.random().toString(36).slice(2, 8);
+
+    const startState = async (query: Record<string, unknown>) => {
+        const { res, captured } = makeRes();
+        await callRoute(
+            'get',
+            '/auth/oidc/:provider/start',
+            makeReq({ params: { provider: 'custom' }, query }),
+            res,
+        );
+        const state = new URL(captured.redirectUrl ?? '').searchParams.get(
+            'state',
+        );
+        return oidc().verifyState(state!) as Record<string, unknown>;
+    };
+
+    const stubIdp = (sub: string, email: string) => {
+        vi.spyOn(oidc(), 'exchangeCodeForTokens').mockResolvedValue({
+            access_token: 'access',
+            id_token: 'id',
+        } as never);
+        vi.spyOn(oidc(), 'getUserInfo').mockResolvedValue({
+            sub,
+            email,
+            email_verified: true,
+        } as never);
+    };
+
+    const openCheck = (data: Record<string, unknown>) => {
+        data.valid = true;
+        data.display = { title: 'T', description: 'D' };
+    };
+
+    const signupCallback = async (bonusCode: string) => {
+        const state = oidc().signState({
+            provider: 'custom',
+            redirect_uri: TEST_ORIGIN + '/',
+            bonus_code: bonusCode,
+        });
+        const { res, captured } = makeRes();
+        await callRoute(
+            'get',
+            '/auth/oidc/callback/signup',
+            makeReq({ query: { code: 'c', state } }),
+            res,
+        );
+        return captured;
+    };
+
+    it('carries a canonical code in the signed state', async () => {
+        const decoded = await startState({
+            flow: 'signup',
+            bonusCode: 'Startup3M-ABCD1234',
+        });
+        expect(decoded.bonus_code).toBe('startup3mabcd1234');
+    });
+
+    it('drops a malformed code at start', async () => {
+        const decoded = await startState({ flow: 'signup', bonusCode: 'a:b' });
+        expect(decoded).not.toHaveProperty('bonus_code');
+    });
+
+    it('creates the account with the requirements an accepted code raises', async () => {
+        const email = `bonus-${rand()}@test.local`;
+        stubIdp(`sub-${rand()}`, email);
+        bonusCheckOverride = openCheck;
+        let seen: Record<string, unknown> | null = null;
+        bonusValidateOverride = (data) => {
+            seen = { ...data };
+            data.accepted = true;
+            data.requires_phone_verification = true;
+        };
+
+        const captured = await signupCallback('startup3mabcd1234');
+
+        expect(captured.cookies).toHaveLength(1);
+        expect(seen).toMatchObject({
+            code: 'startup3mabcd1234',
+            source: 'oidc',
+            email,
+        });
+        const user = await server.stores.user.findEmailOwner(email, {
+            force: true,
+        });
+        expect(Boolean(user!.requires_phone_verification)).toBe(true);
+        const deadline = Date.now() + 2000;
+        let success: Record<string, unknown> | undefined;
+        while (!success && Date.now() < deadline) {
+            success = heardSignupSuccess.find((e) => e.email === email);
+            if (!success) await new Promise((r) => setTimeout(r, 10));
+        }
+        expect(success?.bonus_code).toBe('startup3mabcd1234');
+    });
+
+    it('refuses a dead code before the validate hook runs', async () => {
+        const email = `bonus-${rand()}@test.local`;
+        stubIdp(`sub-${rand()}`, email);
+        let validated = false;
+        signupValidateOverride = (data) => {
+            if (data.email === email) validated = true;
+        };
+
+        const captured = await signupCallback('startup3mabcd1234');
+
+        expect(captured.redirectUrl).toContain('message=bonus_code_invalid');
+        expect(validated).toBe(false);
+    });
+
+    it('refuses the account when nothing accepts the code, without echoing it', async () => {
+        const email = `bonus-${rand()}@test.local`;
+        stubIdp(`sub-${rand()}`, email);
+
+        const captured = await signupCallback('startup3mabcd1234');
+
+        expect(captured.redirectUrl).toContain('message=bonus_code_invalid');
+        expect(captured.redirectUrl).not.toContain('bonusCode=');
+        expect(captured.cookies).toHaveLength(0);
+        expect(
+            await server.stores.user.findEmailOwner(email, { force: true }),
+        ).toBeFalsy();
+    });
+
+    it('keeps the code on the retry redirect when something else failed', async () => {
+        const email = `bonus-${rand()}@test.local`;
+        stubIdp(`sub-${rand()}`, email);
+        bonusCheckOverride = openCheck;
+        signupValidateOverride = (data) => {
+            if (data.email === email) data.allow = false;
+        };
+
+        const captured = await signupCallback('startup3mabcd1234');
+
+        expect(captured.redirectUrl).toContain('message=signup_blocked');
+        expect(captured.redirectUrl).toContain('bonusCode=startup3mabcd1234');
+    });
+});
diff --git a/src/backend/controllers/oidc/OIDCController.ts b/src/backend/controllers/oidc/OIDCController.ts
index a73f9a3bf..9b1cbd1df 100644
--- a/src/backend/controllers/oidc/OIDCController.ts
+++ b/src/backend/controllers/oidc/OIDCController.ts
@@ -23,6 +23,7 @@ import { HttpError } from '../../core/http/HttpError.js';
 import type { PuterRouter } from '../../core/http/PuterRouter.js';
 import { PuterController } from '../types.js';
 import { sessionCookieFlags } from '../../util/cookieFlags.js';
+import { normalizeBonusCode } from '../../util/signupBonus.js';
 import { parseMaskedSharePath } from '../../services/fs/sharePathMask.js';
 import {
     SHARE_DEEP_LINK_ITEMS_LIMIT,
@@ -50,6 +51,7 @@ const ALLOWED_ERRORS = [
     'account_suspended',
     'unauthorized',
     'signup_blocked',
+    'bonus_code_invalid',
 ] as const;
 
 /**
@@ -69,6 +71,23 @@ function resolutionErrorCode(code: string | undefined): string {
         : 'signup_blocked';
 }
 
+/** What a new account created by an OIDC callback inherits from its flow. */
+interface OIDCSignupOptions {
+    referrer?: string | null;
+    bonusCode?: string | null;
+}
+
+function signupOptionsFromState(
+    stateDecoded: Record<string, unknown>,
+): OIDCSignupOptions {
+    return {
+        referrer: (stateDecoded.referrer as string) ?? null,
+        // Normalized when the state was signed; re-checked since this is the
+        // value signup acts on.
+        bonusCode: normalizeBonusCode(stateDecoded.bonus_code),
+    };
+}
+
 // GUI pages an OIDC flow may return to: the root (where a share email lands),
 // /desktop, /dashboard, and direct app landings (/app/<name> and its
 // desktop-booted twin /desktop/app/<name>, mirroring APP_NAME_REGEX in
@@ -222,6 +241,13 @@ function buildErrorRedirectUrl(
     if (requestCode) {
         params.set('request_code', requestCode);
     }
+    // A retry from the error page keeps the bonus code, unless it's what failed.
+    if (
+        typeof stateDecoded?.bonus_code === 'string' &&
+        clamped !== 'bonus_code_invalid'
+    ) {
+        params.set('bonusCode', stateDecoded.bonus_code);
+    }
     for (const path of sharedPaths) {
         params.append(SHARE_DEEP_LINK_PARAM, path);
     }
@@ -423,6 +449,15 @@ export class OIDCController extends PuterController {
                     redirect_uri: appRedirectUri,
                 };
                 if (referrer) statePayload.referrer = referrer ?? openerOrigin;
+                // Login can create an account too, so both flows carry it. A
+                // malformed code is dropped here and never reaches signup.
+                const rawBonusCode = Array.isArray(req.query.bonusCode)
+                    ? req.query.bonusCode[0]
+                    : req.query.bonusCode;
+                const bonusCode = normalizeBonusCode(rawBonusCode);
+                if (bonusCode && (flow === 'login' || flow === 'signup')) {
+                    statePayload.bonus_code = bonusCode;
+                }
                 if (embeddedInPopup && msgId) {
                     statePayload.embedded_in_popup = true;
                     statePayload.msg_id = msgId;
@@ -507,7 +542,7 @@ export class OIDCController extends PuterController {
             const resolved = await this.#resolveOrCreateOIDCUser(
                 provider,
                 userinfo,
-                (stateDecoded.referrer as string) ?? null,
+                signupOptionsFromState(stateDecoded),
             );
             if ('error' in resolved) {
                 console.warn(
@@ -574,7 +609,7 @@ export class OIDCController extends PuterController {
             const resolved = await this.#resolveOrCreateOIDCUser(
                 provider,
                 userinfo,
-                (stateDecoded.referrer as string) ?? null,
+                signupOptionsFromState(stateDecoded),
             );
             if ('error' in resolved) {
                 console.warn(
@@ -742,7 +777,7 @@ if (window.opener) {
     async #resolveOrCreateOIDCUser(
         provider: string,
         userinfo: { sub: string; email?: unknown; [k: string]: unknown },
-        referrer?: string | null,
+        signup: OIDCSignupOptions = {},
         attempt = 0,
     ): Promise<
         | { error: string; code?: string; requestCode?: string }
@@ -792,7 +827,8 @@ if (window.opener) {
         const outcome = await this.services.oidc.createUserFromOIDC(
             provider,
             userinfo as { sub: string; email?: string },
-            referrer,
+            signup.referrer ?? null,
+            { bonusCode: signup.bonusCode ?? null },
         );
         // A concurrent callback (a second tab, a provider retry) created the
         // account between step 2 and the insert. Nothing went wrong for the
@@ -802,7 +838,7 @@ if (window.opener) {
             return this.#resolveOrCreateOIDCUser(
                 provider,
                 userinfo,
-                referrer,
+                signup,
                 attempt + 1,
             );
         }
diff --git a/src/backend/services/auth/OIDCService.ts b/src/backend/services/auth/OIDCService.ts
index 8fbe2d8c1..e7669f0b6 100644
--- a/src/backend/services/auth/OIDCService.ts
+++ b/src/backend/services/auth/OIDCService.ts
@@ -24,6 +24,10 @@ import { isOwnedEmailConflict } from '../../stores/user/UserStore.js';
 import { PuterService } from '../types';
 import { cleanEmail, isBlockedEmail } from '../../util/email.js';
 import { generate_identifier } from '../../util/identifier.js';
+import {
+    checkSignupBonus,
+    validateSignupBonus,
+} from '../../util/signupBonus.js';
 import { generateDefaultFsentries } from '../../util/userProvisioning.js';
 import { Context } from '../../core';
 import crypto from 'node:crypto';
@@ -456,11 +460,14 @@ export class OIDCService extends PuterService {
      * `raced` means a concurrent callback got there first and the caller should
      * re-resolve rather than surface an error — see
      * `#resolveOrCreateOIDCUser`.
+     *
+     * `bonusCode` must already be canonical (`normalizeBonusCode`).
      */
     async createUserFromOIDC(
         providerId: string,
         claims: OIDCUserInfo,
         referrer?: string | null,
+        { bonusCode = null }: { bonusCode?: string | null } = {},
     ): Promise<{
         success: boolean;
         user?: UserRow;
@@ -525,7 +532,7 @@ export class OIDCService extends PuterService {
             // IdP already authenticated the user, so captcha listeners
             // (e.g. Turnstile) should skip — abuse/IP/email checks still run.
             source: 'oidc' as const,
-            data: { username, email },
+            data: { username, email, ...(bonusCode ? { bonusCode } : {}) },
             // `req.ip` honors `trust proxy`; reading x-forwarded-for directly
             // would let a client pick its own per-IP abuse bucket.
             ip: clientIp,
@@ -586,6 +593,24 @@ export class OIDCService extends PuterService {
             };
         }
 
+        // Refuse a dead code before the validate hook records the attempt; see
+        // the same check in AuthController.
+        if (
+            bonusCode &&
+            !(
+                await checkSignupBonus(this.clients.event, bonusCode, {
+                    ip: clientIp,
+                    fingerprint: null,
+                })
+            ).valid
+        ) {
+            return {
+                success: false,
+                error: 'This bonus code is invalid or no longer available.',
+                code: 'bonus_code_invalid',
+            };
+        }
+
         try {
             await this.clients.event?.emitAndWait(
                 'puter.signup.validate',
@@ -608,13 +633,38 @@ export class OIDCService extends PuterService {
             always_require_phone_verification?: boolean;
             always_require_card_verification?: boolean;
         };
-        const force_phone_verification =
+        let force_phone_verification =
             Boolean(validateEvent.requires_phone_verification) ||
             Boolean(cfg.always_require_phone_verification);
-        const force_card_verification =
+        let force_card_verification =
             Boolean(validateEvent.requires_card_verification) ||
             Boolean(cfg.always_require_card_verification);
 
+        if (bonusCode) {
+            const verdict = await validateSignupBonus(
+                this.clients.event,
+                bonusCode,
+                {
+                    source: 'oidc',
+                    email,
+                    clean_email: cleanEmail(email),
+                    ip: clientIp,
+                    reputation: validateEvent.reputation,
+                    requires_phone_verification: force_phone_verification,
+                    requires_card_verification: force_card_verification,
+                },
+            );
+            if (!verdict.accepted) {
+                return {
+                    success: false,
+                    error: 'This bonus code is invalid or no longer available.',
+                    code: 'bonus_code_invalid',
+                };
+            }
+            force_phone_verification = verdict.requiresPhoneVerification;
+            force_card_verification = verdict.requiresCardVerification;
+        }
+
         // The caller checked this email was free before we got here, but the
         // validate hook and the blocklist checks above sit in between — long
         // enough for a second callback (another tab, a provider retry) to have
@@ -765,6 +815,7 @@ export class OIDCService extends PuterService {
                     // have to agree or per-IP counters are written under one
                     // key and read under another.
                     ip: clientIp,
+                    ...(bonusCode ? { bonus_code: bonusCode } : {}),
                 },
                 {},
             );
diff --git a/src/backend/util/signupBonus.test.ts b/src/backend/util/signupBonus.test.ts
new file mode 100644
index 000000000..8fe8203bb
--- /dev/null
+++ b/src/backend/util/signupBonus.test.ts
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2024-present Puter Technologies Inc.
+ *
+ * This file is part of Puter.
+ *
+ * Puter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import { describe, expect, it } from 'vitest';
+import { EventClient } from '../clients/event/EventClient.js';
+import type { EventMap } from '../clients/event/types.js';
+import {
+    bonusCodeInvalidError,
+    isAbsentBonusCode,
+    normalizeBonusCode,
+    validateSignupBonus,
+} from './signupBonus.js';
+
+const baseContext = {
+    email: 'a@test.local',
+    ip: '203.0.113.1',
+    requires_phone_verification: false,
+    requires_card_verification: false,
+};
+
+const clientWith = (
+    listener: (data: EventMap['puter.signup-bonus.validate']) => void,
+) => {
+    const client = new EventClient({} as never);
+    client.on('puter.signup-bonus.validate', (_k, data) => listener(data));
+    return client;
+};
+
+describe('normalizeBonusCode', () => {
+    it('lowercases and drops separators', () => {
+        expect(normalizeBonusCode('Startup3M-7KQ2_9XPA')).toBe(
+            'startup3m7kq29xpa',
+        );
+        expect(normalizeBonusCode(' abcd 1234 ')).toBe('abcd1234');
+    });
+
+    it('rejects anything that cannot be a code', () => {
+        for (const bad of [
+            undefined,
+            null,
+            42,
+            {},
+            '',
+            'abc',
+            'a'.repeat(65),
+            'x'.repeat(129),
+            'abcd.1234',
+            'abcd:1234',
+            'ábcd1234',
+        ]) {
+            expect(normalizeBonusCode(bad)).toBeNull();
+        }
+    });
+});
+
+describe('isAbsentBonusCode', () => {
+    it('treats undefined, null and empty string as absent', () => {
+        expect(isAbsentBonusCode(undefined)).toBe(true);
+        expect(isAbsentBonusCode(null)).toBe(true);
+        expect(isAbsentBonusCode('')).toBe(true);
+        expect(isAbsentBonusCode('abcd')).toBe(false);
+        expect(isAbsentBonusCode(0)).toBe(false);
+    });
+});
+
+describe('bonusCodeInvalidError', () => {
+    it('is a 400 with the stable code', () => {
+        const err = bonusCodeInvalidError();
+        expect(err.statusCode).toBe(400);
+        expect(err.legacyCode).toBe('bonus_code_invalid');
+    });
+});
+
+describe('validateSignupBonus', () => {
+    it('refuses when nothing is listening', async () => {
+        expect(
+            await validateSignupBonus(undefined, 'abcd1234', baseContext),
+        ).toEqual({ accepted: false });
+    });
+
+    it('refuses when the listener leaves the code unaccepted', async () => {
+        const client = clientWith(() => {});
+        expect(
+            await validateSignupBonus(client, 'abcd1234', baseContext),
+        ).toEqual({ accepted: false });
+    });
+
+    it('hands the listener the code and the current requirements', async () => {
+        let seen: EventMap['puter.signup-bonus.validate'] | null = null;
+        const client = clientWith((data) => {
+            seen = { ...data };
+        });
+        await validateSignupBonus(client, 'abcd1234', {
+            ...baseContext,
+            requires_card_verification: true,
+        });
+        expect(seen).toMatchObject({
+            code: 'abcd1234',
+            email: 'a@test.local',
+            requires_phone_verification: false,
+            requires_card_verification: true,
+            accepted: false,
+        });
+    });
+
+    it('returns the requirements a listener raises', async () => {
+        const client = clientWith((data) => {
+            data.accepted = true;
+            data.requires_phone_verification = true;
+        });
+        expect(
+            await validateSignupBonus(client, 'abcd1234', baseContext),
+        ).toEqual({
+            accepted: true,
+            requiresPhoneVerification: true,
+            requiresCardVerification: false,
+        });
+    });
+
+    it('never lets a listener lower a requirement', async () => {
+        const client = clientWith((data) => {
+            data.accepted = true;
+            data.requires_phone_verification = false;
+            data.requires_card_verification = false;
+        });
+        expect(
+            await validateSignupBonus(client, 'abcd1234', {
+                ...baseContext,
+                requires_phone_verification: true,
+                requires_card_verification: true,
+            }),
+        ).toEqual({
+            accepted: true,
+            requiresPhoneVerification: true,
+            requiresCardVerification: true,
+        });
+    });
+
+    it('treats a throwing listener as not accepting', async () => {
+        const client = clientWith(() => {
+            throw new Error('boom');
+        });
+        expect(
+            await validateSignupBonus(client, 'abcd1234', baseContext),
+        ).toEqual({ accepted: false });
+    });
+});
diff --git a/src/backend/util/signupBonus.ts b/src/backend/util/signupBonus.ts
new file mode 100644
index 000000000..0ddb4863c
--- /dev/null
+++ b/src/backend/util/signupBonus.ts
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2024-present Puter Technologies Inc.
+ *
+ * This file is part of Puter.
+ *
+ * Puter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Signup bonus codes: the shape a code may take, and the hand-off to whatever
+ * extension decides what a code is worth. Core holds no codes and grants
+ * nothing.
+ *
+ * Codes have one canonical form (lower case, separators dropped) so a code
+ * typed as `ABC-123` and linked as `abc123` is one code to every counter keyed
+ * on it.
+ */
+import type { EventClient } from '../clients/event/EventClient';
+import type { EventMap } from '../clients/event/types';
+import { HttpError } from '../core/http/HttpError.js';
+
+const CANONICAL_BONUS_CODE = /^[a-z0-9]{4,64}$/;
+/** Raw input is capped before normalizing so a huge string is never scanned. */
+const RAW_BONUS_CODE_MAX_LENGTH = 128;
+
+/** The canonical form of `raw`, or null when it can't be a bonus code. */
+export function normalizeBonusCode(raw: unknown): string | null {
+    if (typeof raw !== 'string' || raw.length > RAW_BONUS_CODE_MAX_LENGTH) {
+        return null;
+    }
+    const canonical = raw.toLowerCase().replace(/[\s_-]/g, '');
+    return CANONICAL_BONUS_CODE.test(canonical) ? canonical : null;
+}
+
+/** Whether a request body field counts as "no bonus code presented". */
+export const isAbsentBonusCode = (raw: unknown): boolean =>
+    raw === undefined || raw === null || raw === '';
+
+/**
+ * One answer for every way a code can fail — unknown, expired, used up — so
+ * signup can't be used to tell them apart.
+ */
+export const bonusCodeInvalidError = (): HttpError =>
+    new HttpError(400, 'This bonus code is invalid or no longer available.', {
+        legacyCode: 'bonus_code_invalid',
+    });
+
+/**
+ * Ask listeners what a canonical code grants right now — the preview the signup
+ * form shows. Signup asks it too, before its abuse checks, so a dead code is
+ * refused before those checks record the attempt against the address.
+ */
+export async function checkSignupBonus(
+    events: EventClient | undefined,
+    code: string,
+    { ip, fingerprint }: { ip: string | null; fingerprint: string | null },
+): Promise<EventMap['puter.signup-bonus.check']> {
+    const event: EventMap['puter.signup-bonus.check'] = {
+        code,
+        ip,
+        fingerprint,
+        valid: false,
+        reason: null,
+        display: null,
+        requirements: null,
+    };
+    try {
+        await events?.emitAndWait('puter.signup-bonus.check', event, {});
+    } catch (e) {
+        console.warn('[signup] bonus check hook failed:', e);
+    }
+    return event;
+}
+
+export type SignupBonusContext = Omit<
+    EventMap['puter.signup-bonus.validate'],
+    'code' | 'accepted'
+>;
+
+export type SignupBonusVerdict =
+    | { accepted: false }
+    | {
+          accepted: true;
+          requiresPhoneVerification: boolean;
+          requiresCardVerification: boolean;
+      };
+
+/**
+ * Offer a canonical bonus code to listeners for a signup that already passed
+ * `puter.signup.validate`. With no listener installed nothing accepts, so a
+ * code is refused rather than silently ignored.
+ */
+export async function validateSignupBonus(
+    events: EventClient | undefined,
+    code: string,
+    context: SignupBonusContext,
+): Promise<SignupBonusVerdict> {
+    const event: EventMap['puter.signup-bonus.validate'] = {
+        ...context,
+        code,
+        accepted: false,
+    };
+    try {
+        await events?.emitAndWait('puter.signup-bonus.validate', event, {});
+    } catch (e) {
+        console.warn('[signup] bonus validate hook failed:', e);
+    }
+    if (event.accepted !== true) return { accepted: false };
+    return {
+        accepted: true,
+        requiresPhoneVerification:
+            context.requires_phone_verification ||
+            event.requires_phone_verification === true,
+        requiresCardVerification:
+            context.requires_card_verification ||
+            event.requires_card_verification === true,
+    };
+}
diff --git a/src/gui/src/UI/UIWindowLogin.js b/src/gui/src/UI/UIWindowLogin.js
index 5e912e262..3a3e0e95b 100644
--- a/src/gui/src/UI/UIWindowLogin.js
+++ b/src/gui/src/UI/UIWindowLogin.js
@@ -440,6 +440,10 @@ async function UIWindowLogin (options) {
                         if ( referrer ) {
                             url += `&referrer=${encodeURIComponent(referrer)}`;
                         }
+                        // A provider login can create the account, so a signup link's code rides along.
+                        if ( window.signup_bonus_code ) {
+                            url += `&bonusCode=${encodeURIComponent(window.signup_bonus_code)}`;
+                        }
                         if ( window.embedded_in_popup && window.url_query_params?.get('msg_id') ) {
                             url += `&embedded_in_popup=true&msg_id=${encodeURIComponent(window.url_query_params.get('msg_id'))}`;
                             if ( window.openerOrigin ) {
diff --git a/src/gui/src/UI/UIWindowSignup.js b/src/gui/src/UI/UIWindowSignup.js
index 5ec4316dc..2ab4c0115 100644
--- a/src/gui/src/UI/UIWindowSignup.js
+++ b/src/gui/src/UI/UIWindowSignup.js
@@ -27,6 +27,30 @@ import { KNOWN_OIDC_PROVIDERS, OIDC_GENERIC_PROVIDER_ICON, humanizeOidcProviderI
 import { offersFederatedSignInInPopup } from '../util/popupAuth.js';
 import { get_auth_redirect_url, get_oidc_return_to } from '../helpers/authRedirect.js';
 import { authLogoHeader, wireAuthLogoHeader } from '../helpers/authLogoHeader.js';
+import { bonusRequirementsKey, checkSignupBonusCode } from '../helpers/signupBonusCode.js';
+
+// What a checked bonus code grants, above the form (and the provider buttons).
+function renderBonusNotice(el_window, result) {
+    const $notice = $(el_window).find('.signup-bonus-notice');
+    if (!result) {
+        $notice.hide().empty();
+        return;
+    }
+    if (!result.valid) {
+        $notice
+            .addClass('signup-bonus-notice-invalid')
+            .html(`<p>${i18n('signup_bonus_code_invalid_retry')}</p>`)
+            .show();
+        return;
+    }
+    const requirementsKey = bonusRequirementsKey(result.requirements);
+    let h = `<strong>${html_encode(result.display.title)}</strong>`;
+    h += `<p>${html_encode(result.display.description)}</p>`;
+    if (requirementsKey) {
+        h += `<p class="signup-bonus-requirements">${i18n(requirementsKey)}</p>`;
+    }
+    $notice.removeClass('signup-bonus-notice-invalid').html(h).show();
+}
 
 function UIWindowSignup(options) {
     options = options ?? {};
@@ -70,6 +94,7 @@ function UIWindowSignup(options) {
         if (window.embedded_in_popup && window.openerOrigin) {
             h += `<p class="auth-opener-notice">${i18n('popup_opener_uses_puter', [new URL(window.openerOrigin).hostname])}</p>`;
         }
+        h += '<div class="signup-bonus-notice" style="display:none;"></div>';
         // signup form
         h += '<form class="signup-form">';
         // error msg
@@ -232,6 +257,27 @@ function UIWindowSignup(options) {
 
                 initTurnstile();
 
+                if (window.signup_bonus_code) {
+                    (async () => {
+                        let fingerprint = null;
+                        try {
+                            fingerprint =
+                                await window.getDeviceFingerprint?.();
+                        } catch (_) {
+                            // the check works without device signals
+                        }
+                        const result = await checkSignupBonusCode(
+                            window.signup_bonus_code,
+                            { origin: window.gui_origin, fingerprint },
+                        );
+                        // Unknown (null) keeps the code; signup has the final say.
+                        if (result && !result.valid) {
+                            window.signup_bonus_code = null;
+                        }
+                        renderBonusNotice(el_window, result);
+                    })();
+                }
+
                 (async () => {
                     try {
                         // A federated hop navigates this popup away and the
@@ -268,6 +314,9 @@ function UIWindowSignup(options) {
                                     if (referrer) {
                                         url += `&referrer=${encodeURIComponent(referrer)}`;
                                     }
+                                    if (window.signup_bonus_code) {
+                                        url += `&bonusCode=${encodeURIComponent(window.signup_bonus_code)}`;
+                                    }
                                     if (
                                         window.embedded_in_popup &&
                                         window.url_query_params?.get('msg_id')
@@ -515,6 +564,9 @@ function UIWindowSignup(options) {
                 if (fingerprint) {
                     requestData.fingerprint = fingerprint;
                 }
+                if (window.signup_bonus_code) {
+                    requestData.bonusCode = window.signup_bonus_code;
+                }
 
                 $.ajax({
                     url: `${window.gui_origin}/signup`,
@@ -669,6 +721,18 @@ function UIWindowSignup(options) {
                                 return;
                             }
 
+                            // Drop the code so the next attempt signs up without it.
+                            if (errorJson?.code === 'bonus_code_invalid') {
+                                window.signup_bonus_code = null;
+                                // The error below says it; the offer no longer applies.
+                                renderBonusNotice(el_window, null);
+                                $(el_window)
+                                    .find('.signup-error-msg')
+                                    .html(i18n('signup_bonus_code_invalid_retry'));
+                                $(el_window).find('.signup-error-msg').fadeIn();
+                                return;
+                            }
+
                             // Handle timeout specifically
                             if (
                                 errorJson?.code === 'response_timeout' ||
diff --git a/src/gui/src/css/style.css b/src/gui/src/css/style.css
index e76305b66..fecd43aad 100644
--- a/src/gui/src/css/style.css
+++ b/src/gui/src/css/style.css
@@ -2241,6 +2241,25 @@ label {
     color: #5f6368;
 }
 
+.signup-bonus-notice {
+    text-align: center;
+    margin: 15px 0;
+    padding: 12px;
+    border-radius: 4px;
+    background-color: #eaf5ee;
+    color: #1e4620;
+    font-size: 14px;
+}
+
+.signup-bonus-notice p {
+    margin: 6px 0 0;
+}
+
+.signup-bonus-notice-invalid {
+    background-color: #fdecea;
+    color: #611a15;
+}
+
 /* -- Logo strip above the login / signup forms -- */
 .auth-logo-header {
     display: flex;
diff --git a/src/gui/src/helpers/signupBonusCode.js b/src/gui/src/helpers/signupBonusCode.js
new file mode 100644
index 000000000..cbc70b03c
--- /dev/null
+++ b/src/gui/src/helpers/signupBonusCode.js
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2024-present Puter Technologies Inc.
+ *
+ * This file is part of Puter.
+ *
+ * Puter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * Signup bonus codes arrive as `?bonusCode=` on a signup link. The GUI only
+ * carries the code; the backend decides what, if anything, it grants.
+ */
+
+export const BONUS_CODE_PARAM = 'bonusCode';
+
+// Loose on purpose: the backend owns the canonical form. This only keeps
+// arbitrary text out of requests and the page.
+const BONUS_CODE_SHAPE = /^[A-Za-z0-9_-]{4,128}$/;
+
+/** The bonus code a URL's query carries, or null. */
+export function readSignupBonusCode(params) {
+    const raw = params?.get?.(BONUS_CODE_PARAM);
+    return typeof raw === 'string' && BONUS_CODE_SHAPE.test(raw) ? raw : null;
+}
+
+/**
+ * Ask the backend what a code grants. Resolves `{ valid: true, display,
+ * requirements }`, `{ valid: false }`, or null when the answer is unknown
+ * (offline, rate limited) — callers keep the code then and let signup decide.
+ */
+export async function checkSignupBonusCode(
+    code,
+    { origin, fingerprint, fetchImpl = fetch } = {},
+) {
+    try {
+        const res = await fetchImpl(`${origin}/signup/bonus-code/check`, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({
+                bonusCode: code,
+                ...(fingerprint ? { fingerprint } : {}),
+            }),
+        });
+        if (!res.ok) return null;
+        const data = await res.json();
+        if (data?.valid === true && data.display) return data;
+        return { valid: false };
+    } catch {
+        return null;
+    }
+}
+
+/** I18n key describing the verification a code requires, or null. */
+export function bonusRequirementsKey(requirements) {
+    const phone = requirements?.phone === true;
+    const card = requirements?.card === true;
+    if (phone && card) return 'signup_bonus_requires_phone_and_card';
+    if (card) return 'signup_bonus_requires_card';
+    if (phone) return 'signup_bonus_requires_phone';
+    return null;
+}
diff --git a/src/gui/src/helpers/signupBonusCode.test.js b/src/gui/src/helpers/signupBonusCode.test.js
new file mode 100644
index 000000000..174155f7d
--- /dev/null
+++ b/src/gui/src/helpers/signupBonusCode.test.js
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2024-present Puter Technologies Inc.
+ *
+ * This file is part of Puter.
+ *
+ * Puter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import { describe, it, expect } from 'vitest';
+import {
+    bonusRequirementsKey,
+    checkSignupBonusCode,
+    readSignupBonusCode,
+} from './signupBonusCode.js';
+
+const query = (search) => new URLSearchParams(search);
+
+describe('readSignupBonusCode', () => {
+    it('reads a well-shaped code from the query', () => {
+        expect(readSignupBonusCode(query('?bonusCode=startup3m-7KQ2'))).toBe(
+            'startup3m-7KQ2',
+        );
+    });
+
+    it('ignores a missing or ill-shaped code', () => {
+        expect(readSignupBonusCode(query(''))).toBeNull();
+        expect(readSignupBonusCode(query('?bonusCode=abc'))).toBeNull();
+        expect(
+            readSignupBonusCode(query('?bonusCode=<script>1234</script>')),
+        ).toBeNull();
+        expect(readSignupBonusCode(undefined)).toBeNull();
+    });
+});
+
+describe('checkSignupBonusCode', () => {
+    const respond = (status, body) => {
+        const calls = [];
+        const fetchImpl = async (url, init) => {
+            calls.push({ url, init });
+            return {
+                ok: status >= 200 && status < 300,
+                json: async () => body,
+            };
+        };
+        return { fetchImpl, calls };
+    };
+
+    it('posts the code (and fingerprint) to the check route', async () => {
+        const { fetchImpl, calls } = respond(200, { valid: false });
+        await checkSignupBonusCode('startup3m-7kq2', {
+            origin: 'https://puter.test',
+            fingerprint: 'fp1',
+            fetchImpl,
+        });
+        expect(calls[0].url).toBe('https://puter.test/signup/bonus-code/check');
+        expect(JSON.parse(calls[0].init.body)).toEqual({
+            bonusCode: 'startup3m-7kq2',
+            fingerprint: 'fp1',
+        });
+    });
+
+    it('returns a valid answer as-is', async () => {
+        const answer = {
+            valid: true,
+            display: { title: 'T', description: 'D' },
+            requirements: { phone: true, card: false },
+        };
+        const { fetchImpl } = respond(200, answer);
+        expect(await checkSignupBonusCode('abcd', { fetchImpl })).toEqual(
+            answer,
+        );
+    });
+
+    it('collapses a refusal to invalid', async () => {
+        const { fetchImpl } = respond(200, { valid: false, reason: 'ended' });
+        expect(await checkSignupBonusCode('abcd', { fetchImpl })).toEqual({
+            valid: false,
+        });
+    });
+
+    it('returns null when the answer is unknown', async () => {
+        const { fetchImpl } = respond(429, {});
+        expect(await checkSignupBonusCode('abcd', { fetchImpl })).toBeNull();
+        const offline = async () => {
+            throw new Error('offline');
+        };
+        expect(
+            await checkSignupBonusCode('abcd', { fetchImpl: offline }),
+        ).toBeNull();
+    });
+});
+
+describe('bonusRequirementsKey', () => {
+    it('names the verification a code requires', () => {
+        expect(bonusRequirementsKey({ phone: true, card: false })).toBe(
+            'signup_bonus_requires_phone',
+        );
+        expect(bonusRequirementsKey({ phone: false, card: true })).toBe(
+            'signup_bonus_requires_card',
+        );
+        expect(bonusRequirementsKey({ phone: true, card: true })).toBe(
+            'signup_bonus_requires_phone_and_card',
+        );
+        expect(bonusRequirementsKey({ phone: false, card: false })).toBeNull();
+        expect(bonusRequirementsKey(null)).toBeNull();
+    });
+});
diff --git a/src/gui/src/i18n/translations/en.js b/src/gui/src/i18n/translations/en.js
index b47923604..c0d6110be 100644
--- a/src/gui/src/i18n/translations/en.js
+++ b/src/gui/src/i18n/translations/en.js
@@ -843,6 +843,11 @@ const en = {
         'signup_blocked_message': 'Your account could not be created.',
         'contact_support': 'Please contact support@puter.com.',
         'contact_support_with_code': 'Please contact support@puter.com and include this code: {{id}}.',
+        'signup_bonus_code_invalid': 'This bonus code is invalid or no longer available.',
+        'signup_bonus_code_invalid_retry': 'This bonus code is invalid or no longer available. You can still create your account without it.',
+        'signup_bonus_requires_phone': 'To claim it, you\'ll verify your phone number after signing up.',
+        'signup_bonus_requires_card': 'To claim it, you\'ll verify a card after signing up.',
+        'signup_bonus_requires_phone_and_card': 'To claim it, you\'ll verify your phone number and a card after signing up.',
 
         // Welcome Window
         'welcome': 'Welcome',
diff --git a/src/gui/src/initgui.js b/src/gui/src/initgui.js
index 6e16c1f64..916bf53c3 100644
--- a/src/gui/src/initgui.js
+++ b/src/gui/src/initgui.js
@@ -59,6 +59,7 @@ import item_icon from './helpers/itemIcon.js';
 import { installAppIconFallback } from './helpers/appIcon.js';
 import launch_app from './helpers/launchApp.js';
 import { urlFileLaunchOptions } from './helpers/confirmUrlFileAccess.js';
+import { readSignupBonusCode } from './helpers/signupBonusCode.js';
 import { parse_url_paths } from './helpers/urlPaths.js';
 import update_last_touch_coordinates from './helpers/updateLastTouchCoordinates.js';
 import update_mouse_position from './helpers/updateMousePosition.js';
@@ -1025,6 +1026,9 @@ function authErrorDisplayMessage() {
     if (code === 'account_suspended') {
         return i18n('account_suspended_message', [], false);
     }
+    if (code === 'bonus_code_invalid') {
+        return i18n('signup_bonus_code_invalid_retry', [], false);
+    }
     return i18n('auth_error_generic', [], false);
 }
 
@@ -1200,6 +1204,7 @@ window.initgui = async function (options) {
 
     // GET query params provided
     window.url_query_params = new URLSearchParams(window.location.search);
+    window.signup_bonus_code = readSignupBonusCode(window.url_query_params);
 
     // Install device signal helpers; collection is lazy. The fingerprint is
     // on by default (gui_params.thumbmarkEnabled = false kills it); the Prelude