[@sentry/bun] Recent update breaks bun integration

[ShaneIsrael]

Is there an existing issue for this?

• I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
• I have reviewed the documentation https://docs.sentry.io/
• I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/bun

SDK Version

8.50.0

Framework Version

No response

Link to Sentry event

No response

Reproduction Example/SDK Setup

No response

Steps to Reproduce

1. Use bun as your nodejs server
2. Setup sentry

Expected Result

The application stands up without issue and sentry initializes correctly.

Actual Result

The application crashes with a TypeError error.

[2025-03-25 18:00:50] [Sentry] express is not instrumented. This is likely because you required/imported express before calling `Sentry.init()`.
[2025-03-25 18:00:50] 40 | 
[2025-03-25 18:00:50] 41 | /**
[2025-03-25 18:00:50] 42 |  * Instruments Bun.serve `fetch` option to automatically create spans and capture errors.
[2025-03-25 18:00:50] 43 |  */
[2025-03-25 18:00:50] 44 | function instrumentBunServeOptions(serveOptions) {
[2025-03-25 18:00:50] 45 |   serveOptions.fetch = new Proxy(serveOptions.fetch, {
[2025-03-25 18:00:50]                                 ^
[2025-03-25 18:00:50] TypeError: A Proxy's 'target' should be an Object
[2025-03-25 18:00:50]       at Proxy (/app/node_modules/@sentry/bun/build/esm/integrations/bunserver.js:45:28)
[2025

[AbhiPrasad]

@ShaneIsrael thanks for writing in.

You said the version you were using was 8.50.0. If you upgrade to 9.x of the SDK, does the issue still occur?

[ShaneIsrael]

@AbhiPrasad Same exact error with 9.9.0 as well.

[AbhiPrasad]

Could you share how you import and initialize Sentry? Also how you are running bun (in the CLI)? Just want to see what the exact starting conditions are.

[ShaneIsrael]

The server is built in a docker image.

# use the official Bun image
# see all versions at https://hub.docker.com/r/oven/bun/tags
FROM oven/bun:1 AS base
WORKDIR /app

FROM base AS install
RUN mkdir -p /temp/dev
COPY package.json bun.lockb /temp/dev/
RUN cd /temp/dev && bun install --frozen-lockfile

# install with --production (exclude devDependencies)
RUN mkdir -p /temp/prod
COPY package.json bun.lockb /temp/prod/
RUN cd /temp/prod && bun install --frozen-lockfile --production

# copy node_modules from temp directory
# then copy all (non-ignored) project files into the image
FROM base AS prerelease
COPY --from=install /temp/dev/node_modules node_modules
COPY . .

# copy production dependencies and source code into final image
FROM base AS release
COPY --from=install /temp/prod/node_modules node_modules
COPY --from=prerelease /app/src src
COPY --from=prerelease /app/server.ts .
COPY --from=prerelease /app/package.json .
COPY --from=prerelease /app/entrypoint.sh .

# run the app
USER bun
EXPOSE 3000/tcp
ENTRYPOINT [ "bash", "entrypoint.sh" ]

// entrypoint.sh

#!/bin/bash
bun run migration:up && bun server.ts

// server.ts file

import 'dotenv/config'
import * as Sentry from '@sentry/bun'
import 'reflect-metadata'

Sentry.init({
  dsn: process.env.SENTRY_DSN,
  tracesSampleRate: 1.0,
  enabled: process.env.ENVIRONMENT !== 'development',
})

import express, { type Application } from 'express'
import Server from './src/index'

process.env.TZ = 'GMT'

const PORT: number = process.env.PORT ? Number.parseInt(process.env.PORT, 10) : 3000

const app: Application = express()
new Server(app, PORT)

// in the src/index file

Sentry.setupExpressErrorHandler(app)