feat(webview): add batchNearby utility for smarter tool ask batching

[easonLiangWorldedtech]

UI tool ask batching fails when models insert API rows between tool calls

Problem

When using models like qwen, the UI shows multiple separate prompts for the same type of tool call:

Zoo wants to read this file (a.ts)
Zoo wants to read this file (b.ts)
Zoo wants to edit this file (c.ts)

Instead of a single batched prompt:

Zoo wants to read these files:
- a.ts
- b.ts

Root Cause

The existing batchConsecutive() utility only merges tool asks that are truly adjacent in the message array. However, models like qwen insert low-information messages between tool calls during streaming:

• say: "api_req_started" — API request metadata row
• say: "api_req_finished" — API request completion row
• say: "text" with empty content — partial streaming rows
• say: "reasoning" — hidden reasoning text

These messages break the consecutive chain, so batchConsecutive stops merging.

Current Code (ChatView.tsx ~line 1272)

const readFileBatched = batchConsecutive(filtered, isReadFileAsk, synthesizeReadFileBatch)
const listFilesBatched = batchConsecutive(readFileBatched, isListFilesAsk, synthesizeListFilesBatch)
const result = batchConsecutive(listFilesBatched, isEditFileAsk, synthesizeEditFileBatch)

Proposed Solution: batchNearby() utility

A new utility that merges same-type tool asks even when separated by ignorable messages. It uses three predicates:

1. isTarget — matches the target tool type (readFile, listFiles, editFile)
2. isIgnorableBetweenTargets — skips over low-info messages without breaking the batch
3. isBoundary — stops merging when hitting a semantic boundary

Ignorable Messages (skipped during batching)

• api_req_started / api_req_finished
• Empty text rows (say: "text" with no content)
• Reasoning rows (say: "reasoning")

Semantic Boundaries (stop merging)

• User feedback (user_feedback, user_feedback_diff)
• Visible assistant text (text with content)
• Completion result (completion_result)
• Checkpoint saved (checkpoint_saved)
• Errors (error)
• Context condensation (condense_context)
• Codebase search results (codebase_search_result)

New Usage in ChatView.tsx

const readFileBatched = batchNearby(filtered, {
  isTarget: isReadFileAsk,
  isIgnorableBetweenTargets, // api_req_started/finished, empty text, reasoning
  isBoundary,                // user_feedback, visible text, completion_result, error, etc.
  synthesize: synthesizeReadFileBatch,
})

Files Changed

• New: webview-ui/src/utils/batchNearby.ts — the batching utility function
• New: webview-ui/src/utils/__tests__/batchNearby.spec.ts — 23 comprehensive tests
• Modified: webview-ui/src/components/chat/ChatView.tsx — replace batchConsecutive with batchNearby

Testing

All 23 unit tests pass, covering:

• Empty input / no matches / single match passthrough
• Consecutive vs non-consecutive matching
• Ignorable messages between targets (api_req_started/finished, empty text, reasoning)
• Semantic boundaries stopping the merge (user_feedback, visible text, completion_result, checkpoint_saved, error)
• Multiple batches separated by boundaries
• Realistic qwen scenarios with API rows between tool calls

Long-term Improvement (separate issue)

Add toolCallGroupId metadata to backend messages so UI can use explicit grouping instead of heuristic-based merging. This would make batching work consistently across all model providers regardless of streaming format differences.

Fixes #1004

Screen Cap

Summary by CodeRabbit

• Improvements
  • Improved chat message grouping during streaming to combine related tool requests more reliably, even when brief or low-information rows appear between them.
  • Ensures key content types (such as user feedback, visible assistant text, errors, and completion results) remain correctly separated.
  • Preserves important semantic boundaries during multi-step operations for clearer, more consistent chat history.

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

Nearby tool-ask batching

Layer / File(s)	Summary
Nearby batching utility webview-ui/src/utils/batchNearby.ts	Adds configurable target, ignorable-row, boundary, and synthesis callbacks, then groups nearby targets while preserving interrupted and boundary rows.
Chat tool-ask integration webview-ui/src/components/chat/ChatView.tsx	Uses nearby batching for read, list, and edit tool asks, allowing low-information streaming rows between matching requests.
Batching behavior validation webview-ui/src/utils/__tests__/batchNearby.spec.ts	Tests passthrough, synthesis, separators, boundaries, immutability, callback grouping, and realistic streamed tool-call sequences.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested reviewers: taltas

Sequence Diagram(s)

sequenceDiagram
  participant ChatView
  participant batchNearby
  participant ToolBatchSynthesizer
  ChatView->>batchNearby: classify streamed tool-ask rows
  batchNearby->>batchNearby: skip ignorable rows and stop at boundaries
  batchNearby->>ToolBatchSynthesizer: synthesize grouped tool asks
  ToolBatchSynthesizer-->>batchNearby: return batched tool-ask row
  batchNearby-->>ChatView: return processed chat rows

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy #1004 by batching around ignorable rows, preserving boundaries, and adding comprehensive tests.
Out of Scope Changes check	✅ Passed	The PR stays focused on tool-ask batching and related tests without introducing unrelated changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Title check	✅ Passed	The title is concise and accurately summarizes the main change: introducing batchNearby for smarter tool-ask batching.
Description check	✅ Passed	The PR description covers the issue, root cause, solution, tests, and screenshot, though it doesn't follow the template headings exactly.

✨ Finishing Touches

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[easonLiangWorldedtech]

@coderabbitai review

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[codecov]

Codecov Report

❌ Patch coverage is 92.68293% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
webview-ui/src/components/chat/ChatView.tsx	72.72%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!

[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@webview-ui/src/utils/batchNearby.ts`:
- Around line 42-67: Update batchNearby in webview-ui/src/utils/batchNearby.ts
(lines 42-67) to track skipped isIgnorableBetweenTargets items in
pendingIgnorable, clear them only when a subsequent target is found, and restore
remaining items to result after finalizing the batch. Make no code change in
webview-ui/src/components/chat/ChatView.tsx (lines 1311-1328). Update the
boundary-message test in webview-ui/src/utils/__tests__/batchNearby.spec.ts
(lines 135-152) to expect four items, including the restored api_req_started
item between match-1 and visible text.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 421939d2-6c08-49b5-989a-af52340d01f0

📥 Commits

Reviewing files that changed from the base of the PR and between 78c1410 and bd3efaa.

📒 Files selected for processing (3)

• webview-ui/src/components/chat/ChatView.tsx
• webview-ui/src/utils/__tests__/batchNearby.spec.ts
• webview-ui/src/utils/batchNearby.ts