fix: decoding chunks in http event stream #1356

unnoq · 2026-01-13T08:44:14Z

Related: https://discordapp.com/channels/1308966753044398161/1308971636539658260/1460548346702987358

Summary by CodeRabbit

Bug Fixes
- Fixed event parser to properly handle events split across multiple data chunks, ensuring incomplete message fragments are retained until complete event assembly.
Tests
- Restructured decoder tests to validate mixed chunk scenarios and event parsing across multiple feeds.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

coderabbitai · 2026-01-13T08:44:26Z

📝 Walkthrough

Walkthrough

The EventDecoder now persists incomplete data across feed calls instead of clearing it after processing. Tests were restructured to verify mixed-chunk scenarios where events split non-atomically across feeds, with adjusted expectations for field values based on chunk boundaries.

Changes

Cohort / File(s)	Summary
Decoder Implementation `packages/standard-server/src/event-iterator/decoder.ts`	Removed the reset of `this.incomplete` at the end of `feed()`, allowing incomplete message data to persist across multiple feed calls for proper reconstruction of split events.
Decoder Tests `packages/standard-server/src/event-iterator/decoder.test.ts`	Restructured test to feed mixed chunk sequences across multiple feeds; renamed to reflect mixed-chunk scenario; updated expectations to show undefined `id`/`retry` in early events and defined values only after later chunks complete the message.

Estimated Code Review Effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly Related PRs

feat(client, server)!: update event-source errors and decode behavior #182: Modifies SSE/event decoding with similar handling of incomplete chunks retained across feeds and corresponding test updates for split/mixed chunk scenarios.

Poem

🐰 A rabbit hops through streaming threads,
No longer clearing what's not said—
Chunks persist through every feed,
Events split, then fulfilled indeed! ✨

🚥 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 'fix: decoding chunks in http event stream' directly relates to the main change: modifying EventDecoder to persist incomplete data across feed calls, fixing chunk handling in HTTP event streams.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

📝 Generate docstrings

📜 Recent review details

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 95c582a and fd51185.

📒 Files selected for processing (2)

packages/standard-server/src/event-iterator/decoder.test.ts
packages/standard-server/src/event-iterator/decoder.ts

💤 Files with no reviewable changes (1)

packages/standard-server/src/event-iterator/decoder.ts

🧰 Additional context used

🧬 Code graph analysis (1)

packages/standard-server/src/event-iterator/decoder.test.ts (1)

packages/standard-server/src/event-iterator/decoder.ts (1)

EventDecoder (56-88)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (3)

GitHub Check: test
GitHub Check: publish-commit
GitHub Check: lint

🔇 Additional comments (2)

packages/standard-server/src/event-iterator/decoder.test.ts (2)
87-140: LGTM! Comprehensive test for chunked event stream decoding.

The test correctly exercises the decoder's ability to handle:

Events split across multiple feed() calls (lines 92-94)

Complete events in a single feed (line 96)

A chunk containing 1.5 events where an event boundary falls mid-chunk (line 98)

Continuation of partial events with id/retry fields (line 99)

Final termination with just a newline (line 100)

The comment at line 97-98 is helpful for maintainers. The expectations correctly reflect that id and retry are only present on events 4 and 5 where those fields were actually included in the event data.

163-219: Good coverage of stream-based mixed chunk handling.

The test at lines 169-172 specifically validates that events split across multiple stream chunks are correctly reassembled:
controller.enqueue('event: done\n')
controller.enqueue('data: hello4\n')
controller.enqueue('data: world\n\n')
The expected result correctly shows id: undefined and retry: undefined for this event since those fields weren't included in the streamed chunks.

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

gemini-code-assist · 2026-01-13T08:44:30Z

Summary of Changes

Hello @unnoq, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical issue in the HTTP event stream decoder where fragmented event messages were not being correctly processed. By adjusting the buffer management and introducing comprehensive tests for mixed-chunk scenarios, the decoder now reliably reconstructs and emits events even when they arrive in incomplete or interleaved segments, leading to more stable and accurate event stream handling.

Highlights

Event Stream Decoding Fix: The EventDecoder logic has been refined to correctly handle fragmented HTTP event stream chunks, ensuring that partial messages are properly buffered and processed across multiple feed calls.
Improved Test Coverage: New and updated unit tests have been introduced to cover complex scenarios involving mixed and fragmented event data, significantly enhancing the robustness of the event stream decoder.
Buffer Management Correction: The incomplete buffer within the EventDecoder is no longer fully cleared after each processBuffer call, allowing incomplete event messages to persist and be completed by subsequent data chunks.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	`/gemini review`	Performs a code review for the current pull request in its current state.
Pull Request Summary	`/gemini summary`	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	`/gemini help`	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

gemini-code-assist

Code Review

This pull request effectively fixes a bug in the EventDecoder where partial event stream messages at the end of a data chunk were being discarded. The fix correctly preserves the incomplete message part for subsequent data chunks. The accompanying test has been significantly improved to cover various chunking scenarios, including fragmented messages and chunks containing multiple messages, which makes the decoder more robust. The changes are correct and improve the reliability of event stream parsing.

pkg-pr-new · 2026-01-13T08:47:08Z

More templates

@orpc/ai-sdk

npm i https://pkg.pr.new/@orpc/ai-sdk@1356

@orpc/arktype

npm i https://pkg.pr.new/@orpc/arktype@1356

@orpc/client

npm i https://pkg.pr.new/@orpc/client@1356

@orpc/contract

npm i https://pkg.pr.new/@orpc/contract@1356

@orpc/experimental-durable-iterator

npm i https://pkg.pr.new/@orpc/experimental-durable-iterator@1356

@orpc/hey-api

npm i https://pkg.pr.new/@orpc/hey-api@1356

@orpc/interop

npm i https://pkg.pr.new/@orpc/interop@1356

@orpc/json-schema

npm i https://pkg.pr.new/@orpc/json-schema@1356

@orpc/nest

npm i https://pkg.pr.new/@orpc/nest@1356

@orpc/openapi

npm i https://pkg.pr.new/@orpc/openapi@1356

@orpc/openapi-client

npm i https://pkg.pr.new/@orpc/openapi-client@1356

@orpc/otel

npm i https://pkg.pr.new/@orpc/otel@1356

@orpc/experimental-pino

npm i https://pkg.pr.new/@orpc/experimental-pino@1356

@orpc/experimental-publisher

npm i https://pkg.pr.new/@orpc/experimental-publisher@1356

@orpc/experimental-publisher-durable-object

npm i https://pkg.pr.new/@orpc/experimental-publisher-durable-object@1356

@orpc/experimental-ratelimit

npm i https://pkg.pr.new/@orpc/experimental-ratelimit@1356

@orpc/react

npm i https://pkg.pr.new/@orpc/react@1356

@orpc/react-query

npm i https://pkg.pr.new/@orpc/react-query@1356

@orpc/experimental-react-swr

npm i https://pkg.pr.new/@orpc/experimental-react-swr@1356

@orpc/server

npm i https://pkg.pr.new/@orpc/server@1356

@orpc/shared

npm i https://pkg.pr.new/@orpc/shared@1356

@orpc/solid-query

npm i https://pkg.pr.new/@orpc/solid-query@1356

@orpc/standard-server

npm i https://pkg.pr.new/@orpc/standard-server@1356

@orpc/standard-server-aws-lambda

npm i https://pkg.pr.new/@orpc/standard-server-aws-lambda@1356

@orpc/standard-server-fastify

npm i https://pkg.pr.new/@orpc/standard-server-fastify@1356

@orpc/standard-server-fetch

npm i https://pkg.pr.new/@orpc/standard-server-fetch@1356

@orpc/standard-server-node

npm i https://pkg.pr.new/@orpc/standard-server-node@1356

@orpc/standard-server-peer

npm i https://pkg.pr.new/@orpc/standard-server-peer@1356

@orpc/svelte-query

npm i https://pkg.pr.new/@orpc/svelte-query@1356

@orpc/tanstack-query

npm i https://pkg.pr.new/@orpc/tanstack-query@1356

@orpc/trpc

npm i https://pkg.pr.new/@orpc/trpc@1356

@orpc/valibot

npm i https://pkg.pr.new/@orpc/valibot@1356

@orpc/vue-colada

npm i https://pkg.pr.new/@orpc/vue-colada@1356

@orpc/vue-query

npm i https://pkg.pr.new/@orpc/vue-query@1356

@orpc/zod

npm i https://pkg.pr.new/@orpc/zod@1356

commit: fd51185

codecov · 2026-01-13T08:47:13Z

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

fix: decoding chunks in event http stream

fd51185

gemini-code-assist bot reviewed Jan 13, 2026

View reviewed changes

unnoq merged commit da9af8b into middleapi:main Jan 13, 2026
6 checks passed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Uh oh!

fix: decoding chunks in http event stream #1356

fix: decoding chunks in http event stream #1356

unnoq commented Jan 13, 2026 •

edited by coderabbitai bot

Loading

Uh oh!

coderabbitai bot commented Jan 13, 2026 •

edited

Loading

Walkthrough

Changes

Estimated Code Review Effort

Possibly Related PRs

Poem

Uh oh!

gemini-code-assist bot commented Jan 13, 2026

Uh oh!

gemini-code-assist bot left a comment

Uh oh!

pkg-pr-new bot commented Jan 13, 2026

Uh oh!

codecov bot commented Jan 13, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

Uh oh!

fix: decoding chunks in http event stream #1356

fix: decoding chunks in http event stream #1356

Conversation

unnoq commented Jan 13, 2026 • edited by coderabbitai bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary by CodeRabbit

Uh oh!

coderabbitai bot commented Jan 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Walkthrough

Changes

Estimated Code Review Effort

Possibly Related PRs

Poem

Uh oh!

gemini-code-assist bot commented Jan 13, 2026

Summary of Changes

Highlights

Footnotes

Uh oh!

gemini-code-assist bot left a comment

Choose a reason for hiding this comment

Code Review

Uh oh!

pkg-pr-new bot commented Jan 13, 2026

Uh oh!

codecov bot commented Jan 13, 2026

Codecov Report

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

unnoq commented Jan 13, 2026 •

edited by coderabbitai bot

Loading

coderabbitai bot commented Jan 13, 2026 •

edited

Loading