Built with Claude: Japan 2026 hackathon: dates and prizes

Anthropic is holding a Claude Code hackathon for people who live in Japan. Its official developer account announced it on X on the morning of October 14. The event is called “Built with Claude: Japan 2026” and is co-hosted by Anthropic and the AI community Cerebral Valley. I am applying too. Who can enter, what participants get, and what to build: these are the things I wanted to check before deciding to apply, so I went through the event page, the official rules posted there, and the official information on past events in the same series.

Dates and eligibility#

The event page and the official rules give these conditions.

Item	Details
Application deadline	Monday, October 26, 23:59 (JST)
Event dates	Monday, November 2, 12:00 to Tuesday, November 10, 14:00 (JST)
Format	Fully online
Eligibility	18 or older and living in Japan
Capacity	250 participants (selective)
Teams	Up to two people. Every team member must apply and be selected
Judges	To be announced

You apply through the Cerebral Valley event page, and the organizers must approve you. According to Techno-Edge (Japanese), you need to create a Cerebral Valley account to apply.

The English rules give the event dates as “November 2 to 8”. That does not match the dates at the top of the page (until 14:00 on November 10), but the submission deadline set on the page is November 10 (UTC).

The announcement says any builder living in Japan can apply, engineer or not. Its pitch is that with Claude Code, seasoned engineers and people touching code for the first time alike can turn an idea into something that works.

What the application form asks#

The required fields on the form are:

• Affiliation (school or company name)
• Where you live (city and prefecture)
• Your experience building with Claude Code (choose beginner, experienced, or expert)
• The thing you are proudest of having built with Claude Code (who uses it and what impact it had)
• What you want to build at this hackathon, and why
• Your Anthropic API organization UUID
• Your Discord username (used for communication during the event)

How you heard about the hackathon is also required. A GitHub URL is optional when you apply and becomes required when you submit your project. LinkedIn, X, and personal website URLs are optional.

You need to have decided what to build by the time you apply. The form says you can find the API organization UUID in the organization settings of the Claude developer console. It does not say what the UUID is used for. Because there is a field for what you have built with Claude Code, first-timers can still apply, but people who have already built something will have more to write.

What participants get#

Each selected participant gets one month of “Max 5x” and $500 in Claude API credits. The rules say both are given for building during the event. Max 5x is a paid individual plan: on the pricing page, it is one tier of the Max plan, which lets you choose five times the usage of Pro. According to Techno-Edge, it costs $100 a month.

The pricing page says Max 5x comes with $100 a month in API credits. The rules do not say whether the Max 5x given at the hackathon includes this as well.

Prizes are API credits#

Winners receive Claude API credits worth $50,000 in total (about ¥8 million, as the event page puts it). The prizes are not cash. According to the rules, a panel of judges picks the finalists, and up to six teams receive prizes. The amount for each prize will be announced on the event page later.

You submit your project through the Cerebral Valley portal. Under the rules, you grant the organizers a royalty-free, irrevocable, perpetual license to use what you submit. You keep ownership, but if you build with work materials or internal company data, it is worth being careful.

For past events, Anthropic’s official blog described the prize credits as being “for project development.” I read that as prizes aimed at people who will keep developing their winning project.

How it differs from past events#

“Built with” is a series of online hackathons that Anthropic and Cerebral Valley have run together. Past events had these terms.

Event	When	Capacity	Given to participants	Total prizes
Built with Opus 4.6	February 2026	500	$500 in API credits	$100,000 in API credits
Built with Opus 4.7	April 2026	500	$500 in API credits	$100,000 in API credits
Built with Claude: Life Sciences	July 2026	500	One month of Max 20x and $200 in API credits	$100,000 in API and usage credits
Built with Claude: Japan 2026	November 2026	250	One month of Max 5x and $500 in API credits	$50,000 in API credits

The Japan edition has half the capacity and half the total prizes of past events. On the other hand, participants get Max 5x on top of the $500 in API credits that the Opus 4.6 and 4.7 events gave. The pricing page says Claude Code is available on Pro and higher plans, so people who usually use the free plan can use Claude Code on Max 5x during the event.

How competitive selection will be can only be estimated from past events. According to GIGAZINE (Japanese), about 13,000 people applied to the Opus 4.6 event and 500 were selected. The Japan edition has 250 seats, half of what past events offered.

In Japan, Anthropic and KERNEL already co-hosted “Claude Hackathon 2025 in Tokyo” (Japanese) in September 2025. It ran for three days, combining a venue in Tokyo with online participation, with 100 participants and a top prize of $3,000 in API credits. The Japan edition’s announcement calls this event “Anthropic’s first hackathon that people from all over Japan can join online.”

What to build#

The event page does not set a single theme. Instead, it names two starting points for what to build.

The first is something born from one person’s deep knowledge. Starting from what you know best, it gives examples such as passed-down craft skills or the frictions of your daily work. The second is something that removes barriers that have held many people back, making what only a few could reach available to everyone. Here it gives examples of challenges shared across Japanese society, such as the aging population and labor shortages. Anthropic says it will introduce the resulting projects and their builders to the world.

In past events, too, people who built from their own field, like the first starting point, have won. The five winners of the Opus 4.6 event were a lawyer, a cardiologist, a roads and infrastructure specialist, an electronic musician, and one software engineer. Four of the five are not professional developers. The first-place lawyer built a tool that helps with the permitting process for building a home in California, and says they did not write or even read a single line of code. At the Opus 4.7 event, first place also went to a physician turned software engineer, with a tool for residents to practice patient encounters.

What is still unknown#

Of the things I wanted to confirm before applying, I could not find the following anywhere in the event page, the rules, the X post, or press coverage.

• Who the judges are, and the judging criteria
• Whether a demo video is required, or whether the source code must be public
• What selection weighs most
• What happens if only one member of a team is selected

The Opus 4.6 event page lists six judges from the Claude team. The Japan edition’s judges are also “to be announced”, so the page will likely be updated. I plan to check it again before the deadline.