The simplest hono app fails to start

[isnifer]

What version of Bun is running?

1.2.3+8c4d3ff80

What platform is your computer?

Darwin 24.3.0 arm64 arm

What steps can reproduce the bug?

1. bun init -y
2. bun add hono
3. Create next script:

import { Hono } from 'hono'

const hono = new Hono()

  /**
   * Default route
   */
  .get('/', c => c.json({ message: 'Hello World' }))

export default hono

What is the expected behavior?

It runs

What do you see instead?

❯ bun run server/test_bun_1.2.3.ts
 7 |       if (typeof entryNamespace?.default?.fetch === 'function')  {
 8 |         const server = Bun.serve(entryNamespace.default);
 9 |         console.debug(`Started ${server.development ? 'development ' : ''}server: ${server.protocol}://${server.hostname}:${server.port}`);
10 |       }
11 |    }, reportError);
12 |    const server = Bun.serve(entryNamespace.default);
               ^
TypeError: Invalid route "0". Path must start with '/'
 code: "ERR_INVALID_ARG_TYPE"

      at bun:main:12:28

Bun v1.2.3 (macOS arm64)

Additional information

No response

[kravetsone]

What version of Bun is running?

1.2.3+8c4d3ff80

What platform is your computer?

Darwin 24.3.0 arm64 arm

What steps can reproduce the bug?

1. bun init -y
2. bun add hono
3. Create next script:

import { Hono } from 'hono'

const hono = new Hono()

/**

• Default route
  */
  .get('/', c => c.json({ message: 'Hello World' }))

export default hono

What is the expected behavior?

It runs

What do you see instead?

❯ bun run server/test_bun_1.2.3.ts
7 | if (typeof entryNamespace?.default?.fetch === 'function') {
8 | const server = Bun.serve(entryNamespace.default);
9 | console.debug(Started ${server.development ? 'development ' : ''}server: ${server.protocol}://${server.hostname}:${server.port});
10 | }
11 | }, reportError);
12 | const server = Bun.serve(entryNamespace.default);
^
TypeError: Invalid route "0". Path must start with '/'
code: "ERR_INVALID_ARG_TYPE"

  at bun:main:12:28

Bun v1.2.3 (macOS arm64)

Additional information

No response

import { Hono } from 'hono'

const hono = new Hono()

  /**
   * Default route
   */
  .get('/', c => c.json({ message: 'Hello World' }))

export default { 
  port: 3000, 
  fetch: hono.fetch, 
} 

use this as workaround

[stefanos82]

I came to report the same thing; with the latest update it breaks like crazy!

This simple code

import { Hono } from 'hono'

type Variables = {
    message: string
};

const app = new Hono<{ Variables: Variables }>()

app.use(async (c, next) => {
    c.set('message', 'Hono is cool!');
    await next();
});

app.get('/', (c) => {
    const message = c.get('message');
    return c.text(`The message is "${message}"`)
});

export default app

throws the following errors:

 7 |       if (typeof entryNamespace?.default?.fetch === 'function')  {
 8 |         const server = Bun.serve(entryNamespace.default);
 9 |         console.debug(`Started ${server.development ? 'development ' : ''}server: ${server.protocol}://${server.hostname}:${server.port}`);
10 |       }
11 |    }, reportError);
12 |    const server = Bun.serve(entryNamespace.default);
               ^
TypeError: Invalid route "0". Path must start with '/'
 code: "ERR_INVALID_ARG_TYPE"

      at bun:main:12:28

Bun v1.2.3 (Linux x64)

[kbrgl]

Best I can tell, this bug was introduced in #17357.

[kravetsone]

Best way to avoid export default like this

[nullmastermind]

Same here, I don't wanna migrate all my projects to export either. 😩

[cstoneham]

Seems like the latest version isn't released yet, I worked around this by just downgrading:

RUN curl -fsSL https://bun.sh/install | bash -s "bun-v1.2.2"