[@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)

[ShaneIsrael]

I should note, nothing in any of these files I shared has changed code wise in probably 2 months and we've had new builds and deploys going out daily without issue until this morning.

[AbhiPrasad]

Did the version of bun change? Looks like https://bun.sh/blog/bun-v1.2.6 came out today. If you force pin to Bun v1.2.5, do you get the same error?

[paulxuca]

It only happens on the new version of bun released today. It looks like a change related to https://bun.sh/blog/bun-v1.2.6#faster-express-fastify broke the sentry integration

[AbhiPrasad]

Ah that seems like it. We should file a bug with bun!

@ShaneIsrael or @paulxuca could you open a GH issue with them and fill in the details about your apps? I can also leave a comment there too.

[ShaneIsrael]

Sorry for the late reply, been busy trying to get a work around our. I did end up pinning bun to v1.2.3 for the time being is working. I think this bun update may have also broke Express. Thus my late responses. As soon as I switch v1.2.3 Express seems to be working fine. I haven't tested Sentry yet but will do so in the morning but I'm guessing that will solve the problem. Will try to open an issue with them as well.

…

On Tue, Mar 25, 2025, 4:47 PM Abhijeet Prasad ***@***.***> wrote: Ah that seems like it. We should file a bug with bun! @ShaneIsrael <https://github.com/ShaneIsrael> or @paulxuca <https://github.com/paulxuca> could you open a GH issue with them and fill in the details about your apps? I can also leave a comment there too. — Reply to this email directly, view it on GitHub <#15827 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAMZPDZVFY7OVBQAH2DW2WD2WHMI7AVCNFSM6AAAAABZYLAPZOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDONJSG4YTEMBUGY> . You are receiving this because you were mentioned.Message ID: ***@***.***> [image: AbhiPrasad]*AbhiPrasad* left a comment (getsentry/sentry-javascript#15827) <#15827 (comment)> Ah that seems like it. We should file a bug with bun! @ShaneIsrael <https://github.com/ShaneIsrael> or @paulxuca <https://github.com/paulxuca> could you open a GH issue with them and fill in the details about your apps? I can also leave a comment there too. — Reply to this email directly, view it on GitHub <#15827 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAMZPDZVFY7OVBQAH2DW2WD2WHMI7AVCNFSM6AAAAABZYLAPZOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDONJSG4YTEMBUGY> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[ShaneIsrael]

I have made a report here: oven-sh/bun#18496

[dzkfzn]

same, I also experienced the same issue.

[AbhiPrasad]

The current workaround is to either revert Bun to 1.2.3 OR remove the BunServer integration like so:

import * as Sentry from '@sentry/bun';

Sentry.init({
  dsn: '__MY_DSN__',
  integrations: function (integrations) {
    // integrations will be all default integrations
    return integrations.filter(function (integration) {
      return integration.name !== "BunServer";
    });
  },
  tracesSampleRate: 1.0,
});