fix(core): throttle shell text output UI updates

[nbardy]

Summary

• Shell tool text output (data events) triggered a React re-render on every chunk, while binary_progress already throttled to 1s intervals via OUTPUT_UPDATE_INTERVAL_MS
• Commands that produce thousands of lines (e.g. build warnings, manifest generation with ~2000 duplicate warnings) caused the UI to freeze — each line forced a full re-render of the shell output panel
• Apply the same OUTPUT_UPDATE_INTERVAL_MS throttle to text data events. The final output is unaffected — it is rendered from the complete result after the command exits

Test plan

• Verified existing shell.test.ts tests are unaffected (only test using type: 'data' is for background mode which already skips updateOutput)
• Manual test: run a command that produces high-volume output (e.g. for i in $(seq 1 5000); do echo "line $i"; done) and verify the UI remains responsive
• Verify final output after command completion is still complete and correct

🤖 Generated with Claude Code

[gemini-code-assist]

Summary of Changes

Hello, 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 significantly enhances the user interface's responsiveness when handling shell commands that produce a large amount of text output. By introducing a throttling mechanism for text data events, it prevents the UI from freezing due to excessive re-renders, thereby improving the overall user experience without compromising the accuracy or completeness of the displayed information.

Highlights

• UI Responsiveness: Addressed UI freezing issues caused by frequent React re-renders during high-volume shell text output.
• Throttling Mechanism: Implemented throttling for shell text data events using the existing OUTPUT_UPDATE_INTERVAL_MS to limit UI updates.
• Output Integrity: Ensured that the final shell output remains complete and correct, as it is rendered only after the command exits.

Changelog

• packages/core/src/tools/shell.ts
  • Implemented throttling logic for 'data' events to prevent frequent UI updates.
  • Added comments explaining the purpose of the new throttling mechanism.

Activity

• Verified that existing shell.test.ts tests remain unaffected by the changes.
• Suggested manual testing for commands producing high-volume output to confirm UI responsiveness.
• Suggested manual testing to verify the completeness and correctness of the final output after command completion.

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[gemini-code-assist]

Code Review

This pull request aims to improve UI performance by throttling shell output updates, which is a valuable enhancement. However, the current implementation introduces a functional regression for non-PTY shell executions. By overwriting the output with each chunk instead of accumulating it, intermediate output is lost during the throttled live updates. I've provided a critical review comment with a code suggestion to address this issue by correctly handling both string-based (cumulative) and object-based (overwrite) output types.

[gemini-code-assist]

The current implementation overwrites cumulativeOutput with each new event.chunk. While this is correct for PTY executions where event.chunk represents the full terminal state (AnsiOutput), it is incorrect for non-PTY (child_process) executions where event.chunk is a partial string of the output. With the new throttling logic, any intermediate chunks received between UI updates will be lost, leading to an incomplete and choppy live view of the command's output.

To fix this, you should accumulate the output for string-based chunks, while continuing to overwrite for AnsiOutput chunks.

Suggested change

	cumulativeOutput = event.chunk;
	if (typeof event.chunk === 'string') {
	cumulativeOutput = (cumulativeOutput as string) + event.chunk;
	} else {
	cumulativeOutput = event.chunk;
	}

[nbardy]

This was fixed in the latest commit

[gemini-cli]

Hi there! Thank you for your interest in contributing to Gemini CLI.

To ensure we maintain high code quality and focus on our prioritized roadmap, we have updated our contribution policy (see Discussion #17383).

We only guarantee review and consideration of pull requests for issues that are explicitly labeled as 'help wanted'. All other community pull requests are subject to closure after 14 days if they do not align with our current focus areas. For this reason, we strongly recommend that contributors only submit pull requests against issues explicitly labeled as 'help-wanted'.

This pull request is being closed as it has been open for 14 days without a 'help wanted' designation. We encourage you to find and contribute to existing 'help wanted' issues in our backlog! Thank you for your understanding and for being part of our community!

[nbardy]

Tracking issue filed: #25459. Cannot reopen this PR (GitHub blocks it — branch is far behind base). Will open a fresh PR against current main referencing the issue.