Come join us for Haunted Hacks to kick off Halloween this year. Hosted by Terse (F26) and AgentRelay (F26), brought to you by OpenAI, Mastra (W25) and Supabase (S20).

OpenAI is offering $100 in OpenAI API credits per participant.

Love Durable Objects? Come build with our Open Source alternative!

Tired of copy/pasting messages between your agents? Come see how much you can build when you let agents collaborate directly with Agent Relay!

Want to do both at the same time? Even better!

Lunch, snacks, candy, bad Halloween/AI puns, swag, coffee, and prizes are all included.

Tracks include:

Hackathon winner: A guaranteed YC interview
Stateful Apps: Build with durable-actors from Terse - iPhone Duo
Agent to agent communication built with Agent Relay: Mac Mini
Costume contest: Bragging rights

October 31, 2026 · YC Office · San Francisco, CA Eligibility

We recommend working in groups, and we're happy to help you form a team if you're coming on your own.

This is an in-person event in San Francisco. You must be able to attend on-site to participate.

Attendees must be 16 or older.

Schedule

10:00am - 11:00am: Doors Open + Registration
11:00am: Hacking begins
1:00pm: Lunch
4:00pm: Submission deadline
4:00pm - 5:00pm: Judging
5:00pm - 6:00pm: Award Ceremony

What to build

The Actor world is hot right now. Come build your own Software Factory, long-running agent, multiplayer AI system or something super creative you've been itching to try out.

Projects should ideally use either Durable actors, or Agent Relay (bonus points if you use both at the same time).\

Rules

All code must be created at the hackathon.

Thinking of ideas before the hackathon is fine.

Judging

We will be using devpost! We recommend setting up your account ahead of time.

The top entries will demo live at the end of the event, and judges will select winners from those demos.

Judges are looking for either very well-executed products or incredibly creative use cases using Durable Actors and Agent Relay. Again, bonus points if you can do both!

Judges will be announced soon.

Prizes

The best overall project will receive a guaranteed YC Interview, $5k in OpenAI API credits and 3 months free of Mastra Platform.

The second place team will receive $2.5k in OpenAI API Credits and 2 months free of Mastra Platform.

The third place team will receive $1k in OpenAI API Credits and 1 month free of Mastra Platform.

The best project using Durable Actors will get an iPhone duo.

The best project built using Agent Relay will get a Mac mini.

The project deemed the “most likely to scale to millions” will receive $1K in credits from Supabase

More prizes will be announced!

Don’t Know What Actors/Durable Objects Are?

Here are some great resources:
- https://boristane.com/blog/what-are-cloudflare-durable-objects/

- https://x.com/aboodman/status/2088155104851657110