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

Summary by CodeRabbit

• Improvements
  • Updated chat streaming behavior to batch related tool requests more reliably when low-information rows appear between them.
  • Added clearer “boundary” handling to prevent mixing across key semantic moments (e.g., user feedback, visible assistant text, completion outputs, checkpoints, and errors).
• Tests
  • Added a comprehensive new test suite covering nearby batching rules, including ignorable rows, boundary stopping, multi-batch segmentation, and immutability.

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📝 Walkthrough

Walkthrough

The chat view now batches same-type tool asks across ignorable streaming rows while preserving semantic boundaries. A generic batchNearby utility replaces batchConsecutive, with tests covering grouping, interruption, ordering, and streamed tool-call sequences.

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, interruption behavior, immutability, callback grouping, and realistic streamed tool-call sequences.

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

Suggested reviewers: navedmerchant, taltas, hannesrudolph, edelauna, jamesrobert20

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
Title check	✅ Passed	The title clearly matches the main change: introducing batchNearby for smarter tool ask batching in webview.
Description check	✅ Passed	The PR description covers the issue, rationale, implementation, and testing, though it doesn't use the repository's exact template headings.
Linked Issues check	✅ Passed	The changes implement the requested batching fix, including ignorable rows, semantic boundaries, and comprehensive qwen-focused tests for #1004.
Out of Scope Changes check	✅ Passed	The removals and test additions are directly tied to replacing batchConsecutive with batchNearby, with no clear unrelated changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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[easonLiangWorldedtech]

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[codecov]

Codecov Report

❌ Patch coverage is 97.50000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
webview-ui/src/utils/chatBatchingPredicates.ts	85.71%	0 Missing and 1 partial ⚠️

📢 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.

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Fix all unresolved CodeRabbit comments on this PR:

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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

[edelauna]

Looks good - can you add some additional JSDOM state tests please

[edelauna]

The latest commit dropped api_req_finished from production isIgnorableBetweenTargets (ChatView.tsx:1289), but the fixture here still lists it — and the tests below (~lines 350, 367, 386) rely on it being ignorable. Since it can't reach batchNearby in production anyway (combineApiRequests merges/drops it and the visibleMessages filter strips it again), should we drop it from the fixture too so the tests model the real predicate?

[edelauna]

These predicates are inline closures, and the spec's copies are hand-synced — which has now drifted twice (the codebase_search_result addition, and the api_req_finished comment on the spec). Two suggestions:

• Export isIgnorableBetweenTargets/isBoundary from a small shared module so the spec imports the real predicates instead of copies.
• Add a ChatView JSDOM test that feeds [readFile ask, api_req_started, readFile ask] and asserts one batched approval row renders instead of two — pins the UI tool ask batching fails when models insert API rows between tool calls #1004 regression where it lives (behavior-only per webview-ui/AGENTS.md, so Vitest rather than visual or e2e).

[easonLiangWorldedtech]

Addressed the review feedback.

Changes made:

• Extracted the batching predicates into a shared utility so production and tests use the same isIgnorableBetweenTargets / isBoundary logic.
• Updated ChatView to import the shared predicates instead of keeping inline closures.
• Updated batchNearby tests to import the real predicates and removed the stale api_req_finished fixture assumptions, since that row is no longer reachable after combineApiRequests / visibleMessages filtering.
• Added a JSDOM regression test in ChatView.spec.tsx that feeds [readFile ask, api_req_started, readFile ask] through the real ChatView state path and asserts the readFile asks are batched.

Validation:

• npx vitest run src/components/chat/__tests__/ChatView.spec.tsx -t "batches readFile asks separated by an API request row"
• npx vitest run src/components/chat/__tests__/ChatView.spec.tsx -t "ChatView - Sound Playing Tests"
• npx vitest run src/utils/__tests__/batchNearby.spec.ts
• pnpm exec eslint --prune-suppressions --max-warnings=0 src/components/chat/ChatView.tsx src/components/chat/__tests__/ChatView.spec.tsx src/utils/__tests__/batchNearby.spec.ts src/utils/chatBatchingPredicates.ts

The commit also passed the repo pre-commit lint hook.

And also rebased.