Back to Blogs
#devchallenge#hf26challenge#hacktoberfest#ai

Join the Hacktoberfest Open-Source AI Challenge: Ghost in the Machine! $2,850 in Prizes Across 21 Winners.

Week 4 of our Hacktoberfest DEV Challenges starts today, and it's our final challenge of the series!...

Updated 7 min read
Cover for Join the Hacktoberfest Open-Source AI Challenge: Ghost in the Machine! $2,850 in Prizes Across 21 Winners.

Week 4 of our Hacktoberfest DEV Challenges starts today, and it's our final challenge of the series! Running through October 31, the Hacktoberfest Open-Source AI Challenge: Week 4 gives you the week to build, wrapping up on Halloween night just as Día de los Muertos begins. 🎃🌼

This year's Hacktoberfest is all about building brand-new projects with open-source AI and open-weight models. Here's everything you need to know about Hacktoberfest 2026.

Missed Week 3: Slow and Steady? No problem. Every challenge is a fresh start, so you're competing on the same footing as everyone else.

This week, we'll select one overall winner and a winner in each of our 20 partner categories. See all the challenges and current partner categories on the HF26 DEV Challenge Hub.

Let's get to it! 👻

This week's theme: Ghost in the Machine

Build something spooky, or something that honors the past in the spirit of Día de los Muertos, with open-weight models or open-source AI.

This week brings us Halloween on October 31 and Día de los Muertos on November 1 and 2, a stretch of the calendar when the line between past and present feels a little thinner. Whether that brings to mind things that go bump in the night, ofrendas glowing with candlelight and marigolds, or the memories and stories we carry with us, we want to see what it inspires you to build. The theme is intentionally broad, so interpret it however you'd like!

That can mean running an open-weight model, building on an open-source agent harness or framework, running inference locally, or all three. Whatever you pick, the open pieces should be what makes your project work.

A few ideas to get you going:

  • A haunted terminal that "possesses" your shell and whispers back eerie commentary on the commands you run
  • A virtual ofrenda builder that helps you write a remembrance for a loved one and gather their favorite foods, songs, and stories
  • An offline séance chatbot that channels the spirit of a long-dead programming language
  • A local oral history tool that records and transcribes family stories so they're never lost
  • A ghost story generator that weaves your smart home's sensor logs into a creepy tale of what happened while you were asleep
  • A project that brings an abandoned open-source tool or a forgotten corner of internet history back to life

In your post, tell us why open innovation matters for what you built. Does running your own model mean your project works with the lights (and the internet) off? Keep your family's photos and stories private and on your own machine? Make sure what you build isn't locked inside a service that might disappear someday? Tell us where your open-based approach worked better than a closed one.

Ghost in the Machine Submission Template

Prize Categories

Alongside our overall winner, we have 20 prize categories for projects that use a specific partner's technology. You don't need to use any of these to win the overall prize, but if you've been curious about any of this tech, this is a great excuse to give one a try. Full descriptions are on the hub.

Featured categories:

Partner categories:

Pro Tip: Partner category winners come from a smaller pool of submissions, so your odds are meaningfully higher.

Note: One project can enter every category it genuinely uses, but you can only win once per challenge, and we'll aim to celebrate as many different builders as possible across the month.

Free credits: several partners are giving participants credits and promo codes. Claim yours at hacktoberfest.com/my.

A huge thank you to our partners for making these prizes possible!

Judging Criteria

This is DEV, so your write-up matters most.

  • Writing Quality (weighted most heavily): Is the post clear and engaging? Does it explain what you built, who it's for, and why open innovation matters?
  • Relevance to the Prompt and Theme: Is open-source AI or open-weight models at the core of the project? Does it capture the spirit of the theme in a thoughtful way?
  • Creativity: Is it an original idea, or a fresh take on a familiar problem?
  • Technical Execution: Does it work, and is it well built?
  • Use of Partner Technology (optional): If you're entering a partner category, does the project use that technology in a meaningful way?

Show your work. We'd love to see how you built it. Save your agent session with DevRelay and embed it in your post, or link to it. It's optional, but it helps the judges understand your process.

Prizes

  • Overall winner (1): $250 USD, a DEV++ membership, and an exclusive DEV badge
  • Featured category winners (6): $200 USD and an exclusive DEV badge each
  • Partner category winners (14): $100 USD and an exclusive DEV badge each

All participants with a valid submission will receive a completion badge.

How To Participate

Publish a post on DEV using the submission template above. Tell us what you built and how you interpreted the theme, show us a demo, and explain why open innovation matters for what you built. If you can show us the moment your project landed, whether it gave someone chills or brought back a memory, even better!

Please review our judging criteria, rules, guidelines, and FAQ page before submitting so you understand our participation guidelines and official contest rules, such as eligibility requirements.

Need Help?

Important Dates

  • October 26: Hacktoberfest Open-Source AI Challenge: Week 4 begins!
  • October 31: Submissions due at 11:59 PM PDT 🎃
  • November 1 - 2: Día de los Muertos 🌼
  • Week of November 2: Winners announced

Thank You for an Amazing Hacktoberfest

This is the last challenge of our Hacktoberfest series, and we've loved seeing everything you've built with open-source AI this month. Thank you to every participant, partner, and community member who showed up week after week. Let's make this final week one to remember!

Questions about the challenge? Drop them in the comments below.

Happy Hacktoberfest, and good luck! 👻🌼