Terms of Service

Last updated: March 12, 2026

1. Introduction and Acceptance

These Terms of Service (“Terms”) constitute a legally binding agreement between you (“User,” “you,” or “your”) and Heart Engineer LLC (“HeartStack,” “we,” “our,” or “us”), governing your access to and use of the HeartStack AI platform, including our website at heartstack.ai, our web application, and all related services (collectively, the “Service”).

By creating an account, accessing, or using HeartStack, you acknowledge that you have read, understood, and agree to be bound by these Terms and our Privacy Policy. If you do not agree to these Terms, do not use the Service.

We reserve the right to modify these Terms at any time. We will notify you of material changes via email or through the Service. Your continued use of HeartStack after such modifications constitutes your acceptance of the updated Terms.

2. Description of Service

HeartStack AI is an AI-powered content creation platform designed for founders and professionals. The Service provides AI agents that assist users in capturing ideas, developing content strategy, generating written drafts, and reviewing content quality for platforms including LinkedIn. Content captures can be submitted through the web application or via WhatsApp messaging (an optional feature).

HeartStack uses artificial intelligence, including Anthropic's Claude API, to process your inputs and generate content recommendations and drafts. The Service is a tool that assists your content creation process — it does not replace your judgment, and all content decisions remain yours.

3. Eligibility

To use HeartStack, you must:

  • Be at least 18 years of age.
  • Have the legal capacity to enter into a binding agreement.
  • Provide accurate and complete registration information.
  • Not have been previously suspended or removed from the Service.

HeartStack is designed for business professionals and is not intended for use by consumers under 18.

4. Account Registration and Security

When you create an account, you agree to:

  • Provide accurate, current, and complete information during registration.
  • Maintain and promptly update your account information.
  • Keep your password secure and confidential.
  • Not share your account credentials with any third party.
  • Notify us immediately of any unauthorized use of your account.

You are responsible for all activity that occurs under your account. HeartStack is not liable for any loss or damage arising from your failure to maintain the security of your account credentials.

5. Subscription Terms and Payment

5.1 Pricing

HeartStack offers a paid subscription plan at the pricing displayed at the time of your purchase. Current pricing is $79 per month. We reserve the right to change pricing with 30 days' advance notice to existing subscribers.

5.2 Free Trial

New subscribers may receive a 7-day free trial with full access to all features. Your payment method will be charged automatically at the end of the trial period unless you cancel before the trial expires. You will receive a reminder email before your trial ends.

5.3 Billing

Subscriptions are billed monthly in advance on the calendar date corresponding to the start of your subscription. All payments are processed through Stripe. By subscribing, you authorize us to charge your payment method on a recurring basis.

5.4 Cancellation

You may cancel your subscription at any time through your account settings or the Stripe billing portal. Upon cancellation:

  • You retain access to the Service through the end of your current billing period.
  • No further charges will be made after the current period ends.
  • Your account data is retained for 90 days after cancellation, during which you may reactivate your subscription. After 90 days, your data may be permanently deleted.

5.5 Refunds

Refund requests made within 30 days of a charge will be considered on a case-by-case basis. To request a refund, contact us at hello@heartstack.ai. We are not obligated to provide refunds but will make reasonable efforts to resolve billing concerns.

5.6 Failed Payments

If a payment fails, we will attempt to process the charge again and notify you via email. You will have a grace period of up to 7 days to update your payment method. If payment is not resolved within the grace period, your access to paid features will be suspended until payment is successfully processed.

6. Beta Program

HeartStack may offer beta access to select users at our discretion. Beta users may receive access to the Service without a paid subscription for a limited period. Beta access may be revoked or converted to a paid subscription at any time with reasonable notice. Beta users agree to provide feedback and acknowledge that the Service may contain bugs or incomplete features during the beta period.

7. Acceptable Use

You agree to use HeartStack only for lawful purposes and in accordance with these Terms. You agree NOT to:

  • Use the Service to generate, store, or distribute content that is illegal, defamatory, harassing, threatening, obscene, or otherwise objectionable.
  • Use the Service to create spam, bulk unsolicited messages, or misleading content.
  • Impersonate any person or entity, or misrepresent your affiliation with any person or entity.
  • Attempt to gain unauthorized access to any part of the Service, other users' accounts, or any systems or networks connected to the Service.
  • Use automated scripts, bots, scrapers, or other automated means to access or interact with the Service, except through our official API if provided.
  • Reverse engineer, decompile, disassemble, or attempt to derive the source code of the Service.
  • Interfere with or disrupt the integrity or performance of the Service.
  • Use the Service in any manner that could damage, disable, overburden, or impair our servers or networks.
  • Resell, sublicense, or commercially exploit access to the Service without our written consent.
  • Use the Service to develop a competing product or service.
  • Attempt to manipulate or circumvent AI agent instructions, safety measures, or usage limits.
  • Use the WhatsApp capture feature for any purpose other than submitting content captures to your HeartStack vault, including attempting to use it as a customer support channel, chatbot, or for sending messages to other users.
  • Connect a phone number that does not belong to you or that you do not have authorization to use with the WhatsApp capture feature.

We reserve the right to investigate and take appropriate action against anyone who violates these Terms, including suspending or terminating their account without notice or refund.

8. Intellectual Property and Content Ownership

8.1 Your Content

You retain full ownership of all content you input into HeartStack, including voice memos, text notes, documents, and URLs (“Your Content”). You also retain full ownership of all content generated by HeartStack's AI agents based on Your Content (“Generated Content”).

You grant HeartStack a limited, non-exclusive, non-transferable license to process Your Content solely for the purpose of providing the Service to you. This license terminates when you delete Your Content or close your account.

8.2 Responsibility for Content

You are solely responsible for:

  • The accuracy, legality, and appropriateness of Your Content and any Generated Content you choose to publish.
  • Reviewing and editing all Generated Content before publishing. AI-generated content may contain errors, inaccuracies, or content that does not reflect your views.
  • Ensuring that your use of Generated Content complies with the terms of service of any platform where you publish it, including LinkedIn.
  • Ensuring that Your Content and Generated Content does not infringe upon the intellectual property rights of any third party.

HeartStack does not guarantee the accuracy, completeness, or suitability of any Generated Content. The Service is a tool — you are the publisher.

8.3 Our Intellectual Property

The Service, including its software, design, features, documentation, AI agent architectures, system prompts, and branding (including the HeartStack name, logo, and agent names Mika, Sage, Kai, and Reva), is owned by Heart Engineer LLC and protected by intellectual property laws.

You may not copy, modify, distribute, sell, or lease any part of the Service or its underlying technology without our written permission.

9. AI-Generated Content Disclaimer

HeartStack uses artificial intelligence to assist in content creation. You acknowledge and agree that:

  • AI-generated content is produced by machine learning models and may contain errors, inaccuracies, biases, or content that does not reflect your intended message.
  • You are responsible for reviewing, editing, and approving all content before publication.
  • HeartStack does not guarantee that Generated Content will achieve any particular result, engagement level, or business outcome.
  • AI models may occasionally produce unexpected or inappropriate outputs despite safety measures. You agree to report any such outputs to us.
  • HeartStack is not responsible for any consequences arising from your decision to publish AI-generated content without adequate review.

10. Third-Party Services

HeartStack integrates with third-party services to provide the Service, including:

  • Anthropic (Claude API): For AI processing of your content. Anthropic's terms and privacy policy apply to data processed through their API.
  • Stripe: For payment processing. Stripe's terms and privacy policy apply to your payment information.
  • Supabase: For data storage and authentication.
  • LinkedIn: If you connect your LinkedIn account for analytics and publishing features, LinkedIn's terms of service apply.
  • Unipile: For LinkedIn analytics aggregation. If you connect your LinkedIn account for analytics, Unipile accesses your post metrics and engagement data with your authorization. Unipile's terms and privacy policy apply.
  • Meta (WhatsApp Business): If you enable WhatsApp capture, your messages are delivered through Meta's WhatsApp Business Cloud API. Meta's WhatsApp Business Policy and WhatsApp Privacy Policy apply to message delivery.

We are not responsible for the practices, policies, or availability of third-party services. Your use of these services is subject to their respective terms.

11. Privacy

Your privacy is important to us. Our collection, use, and protection of your personal information is governed by our Privacy Policy. The Privacy Policy is incorporated into these Terms by reference.

12. Limitation of Liability

TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW:

HeartStack, Heart Engineer LLC, and its officers, directors, employees, and agents shall not be liable for any indirect, incidental, special, consequential, or punitive damages, including but not limited to loss of profits, revenue, data, business opportunities, or goodwill, arising out of or related to your use of or inability to use the Service, regardless of the theory of liability.

Our total aggregate liability arising out of or related to these Terms or the Service shall not exceed the amount you have paid to HeartStack in the twelve (12) months immediately preceding the event giving rise to the claim.

These limitations apply even if HeartStack has been advised of the possibility of such damages and even if any remedy fails of its essential purpose.

13. Indemnification

You agree to indemnify, defend, and hold harmless Heart Engineer LLC, its officers, directors, employees, and agents from and against any and all claims, damages, losses, liabilities, costs, and expenses (including reasonable attorneys' fees) arising out of or related to:

  • Your use of the Service.
  • Your Content or Generated Content that you publish.
  • Your violation of these Terms.
  • Your violation of any third-party rights, including intellectual property rights.
  • Any claim that content you published using the Service caused damage to a third party.

14. Disclaimer of Warranties

THE SERVICE IS PROVIDED “AS IS” AND “AS AVAILABLE” WITHOUT WARRANTIES OF ANY KIND, WHETHER EXPRESS, IMPLIED, OR STATUTORY, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND NON-INFRINGEMENT.

HeartStack does not warrant that:

  • The Service will be uninterrupted, secure, or error-free.
  • The results obtained from the Service will be accurate or reliable.
  • AI-generated content will be free from errors, biases, or inappropriate content.
  • The Service will meet your specific requirements or expectations.

15. Account Termination

15.1 Termination by You

You may close your account at any time by contacting us at hello@heartstack.ai or through your account settings. Closing your account will cancel any active subscription at the end of the current billing period.

15.2 Termination by Us

We may suspend or terminate your account at any time, with or without cause, and with or without notice, including but not limited to:

  • Violation of these Terms or the Acceptable Use policy.
  • Non-payment of subscription fees.
  • Conduct that we determine, in our sole discretion, is harmful to other users, us, or third parties.
  • Extended inactivity.

Upon termination, your right to use the Service immediately ceases. We may delete your data in accordance with our Privacy Policy.

16. Dispute Resolution

16.1 Governing Law

These Terms are governed by and construed in accordance with the laws of the State of California, without regard to its conflict of law provisions.

16.2 Informal Resolution

Before filing any formal claim, you agree to attempt to resolve any dispute informally by contacting us at hello@heartstack.ai. We will attempt to resolve the dispute within 30 days.

16.3 Jurisdiction

If informal resolution is unsuccessful, any legal action or proceeding arising under these Terms shall be brought exclusively in the state or federal courts located in Santa Clara County, California, and you consent to the personal jurisdiction of such courts.

17. General Provisions

Entire Agreement. These Terms, together with the Privacy Policy, constitute the entire agreement between you and HeartStack regarding the Service and supersede all prior agreements and understandings.

Severability. If any provision of these Terms is held to be invalid or unenforceable, the remaining provisions shall continue in full force and effect.

Waiver. Our failure to enforce any right or provision of these Terms shall not constitute a waiver of such right or provision.

Assignment. You may not assign or transfer your rights under these Terms without our prior written consent. We may assign our rights and obligations without restriction.

Force Majeure. HeartStack shall not be liable for any failure or delay in performance due to circumstances beyond our reasonable control, including natural disasters, acts of government, internet disruptions, or third-party service outages.

Notices. We may provide notices to you via email to the address associated with your account or through the Service. You may provide notices to us at the contact information below.

18. Contact Us

If you have any questions about these Terms of Service, please contact us:

Heart Engineer LLC

HeartStack AI

Email: hello@heartstack.ai

Website: heartstack.ai

© 2026 Heart Engineer LLC. All rights reserved.

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