fix(typescript-client): bundle patched version of fetch-event-source

[pawelblaszczyk5]

Hello 👋

When liveSse mode got introduced, it included fetch-event-source which is used instead of built-in EventSource because of richer capabilities. However, it had a few assumptions (document/window existence) + bugs when it comes to aborting. This was patched, however, when building typescript-client patched version isn't included and when user uses it - they have unpatched version.

Screenshot from npm published code:

That results in all of these issues being present when consumer installs the library. For example, it's impossible to abort liveSse shapes, which someone spotted here #2322 (comment)

This makes the fetch-event-source library being inlined in the bundled code, with patched changes applied. Example output after my change (I marked some changes which are included in the patch):

Example from the local app I'm working on atm, without the patch - observe shape requests being aborted and then immediately started again

Screen.Recording.2026-01-18.at.14.45.54.mov

While if I used dist built from this branch:

Screen.Recording.2026-01-18.at.14.44.42.mov

That was a bit rough to debug, but I think I've got it right 😄

Summary by CodeRabbit

• Bug Fixes

  • Ensured liveSse mode now includes the correct event-source support across builds so consumers receive the patched runtime behavior (fixes unpatched event handling and abort issues).

• Documentation

  • Added a changeset entry documenting the patch and its impact on liveSse behavior.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds a changeset entry for a patch bump of @electric-sql/client and updates the TypeScript client's build config to include @microsoft/fetch-event-source in bundled outputs so the patched implementation is delivered to consumers.

Changes

Cohort / File(s)	Summary
Build configuration packages/typescript-client/tsup.config.ts	Added noExternal: [\@microsoft/fetch-event-source`]tocommonOptions, causing @microsoft/fetch-event-source` to be bundled into outputs (esm, cjs, legacy esm, browser).
Changeset documentation .changeset/slow-apricots-clean.md	Adds a changeset noting a patch bump for @electric-sql/client and documents that liveSse previously relied on fetch-event-source (with assumptions/bugs around document/window and abort handling) which are intended to be included in the patched client build.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• KyleAMathews

Poem

🐰 I hopped through code to tuck it tight,
Fetch-event-source bundled snug and right,
No loose hops in browsers now, hooray—
Patch in place, I nibble worries away! 🥕✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: bundling a patched version of fetch-event-source into the typescript-client package to fix runtime issues.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between e462b78 and 7b29b8f.

📒 Files selected for processing (2)

• .changeset/slow-apricots-clean.md
• packages/typescript-client/tsup.config.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• .changeset/slow-apricots-clean.md
• packages/typescript-client/tsup.config.ts

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@electric-sql/react@3732

npm i https://pkg.pr.new/@electric-sql/client@3732

npm i https://pkg.pr.new/@electric-sql/y-electric@3732

commit: e462b78

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[pawelblaszczyk5]

I spotted someone running actions here and it failing with some unrelated golang error during build - I rebased the branch to current main, hope it helps 😄 Can I do anything more to help it move forward? Are my findings correct here, or should I dig deeper? Thanks a lot in advance!

[balegas]

Hey, nice catch! Thanks for the contribution.