feat(a2ui): add server stream performance logs by Sherry-hue · Pull Request #2721 · lynx-family/lynx-stack

Sherry-hue · 2026-05-27T05:56:11Z

Summary

Add targeted server-side performance logs around the A2UI streaming APIs so production latency can be broken down by request body handling, validation, agent setup, upstream stream invocation, and first streamed chunk.

Details

Report request body metrics from readJsonBodyWithLimit, including declared/raw byte size plus read and JSON parse timings.
Log /a2ui/stream and /a2ui/action/stream phases from request receipt through validation, agent connection, first upstream chunk, validation, repair, and completion.
Add agent service performance callbacks for cache hit/miss, conversation message construction, model message conversion, and agent.stream() invocation timing.

Validation

pnpm -C packages/genui/server exec tsc --noEmit
pnpm dprint check packages/genui/server/app/a2ui/_shared.ts packages/genui/server/app/a2ui/stream/route.ts packages/genui/server/app/a2ui/action/stream/route.ts packages/genui/server/service/a2ui-agent.ts
pre-commit hooks ran eslint --cache --fix, biome lint --write, and dprint fmt on staged files

Summary by CodeRabbit

Release Notes

Chores
- Enhanced request monitoring with detailed performance metrics collection across the streaming pipeline.
- Added structured event logging throughout request lifecycle and streaming operations for improved operational visibility.

changeset-bot · 2026-05-27T05:56:16Z

⚠️ No Changeset found

Latest commit: e955c3f

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coderabbitai · 2026-05-27T05:56:18Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 45d90240-f4ea-4ab3-9913-a1d1c112a237

📥 Commits

Reviewing files that changed from the base of the PR and between 6a293cb and 054575f.

📒 Files selected for processing (4)

packages/genui/server/app/a2ui/_shared.ts
packages/genui/server/app/a2ui/action/stream/route.ts
packages/genui/server/app/a2ui/stream/route.ts
packages/genui/server/service/a2ui-agent.ts

📝 Walkthrough

Walkthrough

This PR adds comprehensive structured instrumentation and performance event logging across the A2UI server stack. JSON body metrics (size and timing) are collected at the shared parsing layer, exposed through updated return types, and logged by route handlers. The service layer emits performance events at key points (cache hits/misses, message preparation, stream invocation), and both action and standard stream routes wire callback handlers to capture and log these events alongside request lifecycle checkpoints.

Changes

A2UI Server Instrumentation and Performance Event Logging

Layer / File(s)	Summary
JSON body metrics contract and collection `packages/genui/server/app/a2ui/_shared.ts`	Introduces `JsonBodyMetrics` interface and extends `readJsonBodyWithLimit` to measure and return parsing timing, declared byte length, and raw UTF-8 byte length on all success and failure code paths.
Service performance event infrastructure `packages/genui/server/service/a2ui-agent.ts`	Adds optional `onPerformanceEvent` callback to `ChatOptions`, implements `sumContentChars()` helper for character counting, and emits structured events during agent cache lookup, model message preparation, stream invocation, and conversation assembly.
Action stream route request lifecycle logging `packages/genui/server/app/a2ui/action/stream/route.ts`	Adds stream logger at request start and logs rate-limit decisions, JSON body parsing metrics, validation checkpoints with timing (action name, surfaceId, conversation), wires upstream performance events to logger, and adds connection/first-chunk timing logs during streaming.
Standard stream route request lifecycle logging `packages/genui/server/app/a2ui/stream/route.ts`	Adds stream logger at request start and logs rate-limit decisions, JSON body parsing metrics, message/conversation validation with timing, wires upstream performance events to logger, and adds connection/first-chunk timing logs during streaming.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

lynx-family/lynx-stack#2709: Both PRs modify the server A2UI SSE route handlers to add instrumentation and structured logging, including wiring performance/protocol events through the streaming options.

Suggested reviewers

HuJean
gaoachao
PupilTong

Poem

🐰 Metrics flow like carrots through the stream,
Each event logged, a performance dream,
From body bytes to cache timing true,
The agent sings its song for you. 🎵

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat(a2ui): add server stream performance logs' directly and concisely describes the main change: adding performance logging to A2UI server streaming endpoints.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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codecov · 2026-05-27T05:59:10Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!

codspeed-hq · 2026-05-27T06:15:55Z

Merging this PR will not alter performance

✅ 81 untouched benchmarks
⏩ 26 skipped benchmarks¹

_{Comparing Sherry-hue:feat/a2ui-server-perf-metrics (e955c3f) with main (f38e285)²}

26 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩
No successful run was found on main (ec73c30) during the generation of this report, so f38e285 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

relativeci · 2026-05-27T06:16:27Z

React Example

#8719 Bundle Size — 238KiB (0%).

054575f(current) vs 6a293cb main#8718(baseline)

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Bundle analysis report Branch Sherry-hue:feat/a2ui-server-perf... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-05-27T06:16:41Z

React Example with Element Template

#987 Bundle Size — 204.36KiB (0%).

054575f(current) vs 6a293cb main#986(baseline)

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Bundle size by type no changes

	Current #987	Baseline #986
IMG	`145.76KiB`	`145.76KiB`
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Bundle analysis report Branch Sherry-hue:feat/a2ui-server-perf... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-05-27T06:17:12Z

React External

#1834 Bundle Size — 699.5KiB (0%).

054575f(current) vs 6a293cb main#1833(baseline)

Bundle metrics no changes

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Bundle size by type no changes

	Current #1834	Baseline #1833
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Bundle analysis report Branch Sherry-hue:feat/a2ui-server-perf... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-05-27T06:17:29Z

Web Explorer

#10295 Bundle Size — 903.53KiB (0%).

054575f(current) vs 6a293cb main#10294(baseline)

Bundle metrics

1 change

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Bundle size by type no changes

	Current #10295	Baseline #10294
JS	`499.15KiB`	`499.15KiB`
Other	`402.16KiB`	`402.16KiB`
CSS	`2.22KiB`	`2.22KiB`

Bundle analysis report Branch Sherry-hue:feat/a2ui-server-perf... Project dashboard

^{Generated by RelativeCI Documentation Report issue}

relativeci · 2026-05-27T06:17:34Z

React MTF Example

#1853 Bundle Size — 208.94KiB (0%).

054575f(current) vs 6a293cb main#1852(baseline)

Bundle metrics no changes

	Current #1853	Baseline #1852
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Bundle size by type no changes

	Current #1853	Baseline #1852
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Bundle analysis report Branch Sherry-hue:feat/a2ui-server-perf... Project dashboard

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feat(a2ui): add server stream performance logs

054575f

Sherry-hue marked this pull request as ready for review May 27, 2026 07:42

Merge branch 'main' into feat/a2ui-server-perf-metrics

e955c3f

HuJean approved these changes May 28, 2026

View reviewed changes

Sherry-hue merged commit fc55da2 into lynx-family:main May 28, 2026
73 of 76 checks passed

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Summary

Details

Validation

Summary by CodeRabbit

Release Notes

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Walkthrough

Changes

Estimated code review effort

Possibly related PRs

Suggested reviewers

Poem

❌ Failed checks (1 warning)

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Codecov Report

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Merging this PR will not alter performance

Footnotes

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relativeci Bot commented May 27, 2026

React Example

#8719 Bundle Size — 238KiB (0%).

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relativeci Bot commented May 27, 2026

React Example with Element Template

#987 Bundle Size — 204.36KiB (0%).

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relativeci Bot commented May 27, 2026

React External

#1834 Bundle Size — 699.5KiB (0%).

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relativeci Bot commented May 27, 2026

Web Explorer

#10295 Bundle Size — 903.53KiB (0%).

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relativeci Bot commented May 27, 2026

React MTF Example

#1853 Bundle Size — 208.94KiB (0%).

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Sherry-hue commented May 27, 2026 •

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