docs(vscode): analyze webview tab vs sidebar performance differences

[kilo-code-bot]

Summary

• Adds a detailed analysis document investigating potential performance issues when the Kilo Code extension webview runs in an editor tab versus the default sidebar position
• Identifies three compounding root causes: unthrottled per-token SSE streaming with no event coalescing, lack of visibility-aware message gating, and duplicate KiloProvider processing when both sidebar and tab are open
• Provides prioritized recommendations from short-term (16ms event coalescing) to long-term (virtual scrolling, removing retainContextWhenHidden for non-critical panels)

Key Findings

1. No event coalescing — Per-token postMessage calls during streaming overwhelm the webview. The codebase already documents this as a planned improvement in sdk-sse-adapter.ts:22-27.
2. No visibility awareness — Neither the extension host nor the webview checks visibility before processing events. The sidebar gets implicit throttling from VS Code when hidden; the tab does not.
3. Duplicate work — Opening Kilo in a tab while the sidebar is active creates two independent KiloProvider instances processing the same SSE events.
4. No virtual scrolling — All messages rendered in DOM; wider tab viewport = more layout work per update.
5. Identical code paths — resolveWebviewView() and resolveWebviewPanel() use the same HTML, bundle, and message handling — no tab-specific logic exists.

This is a research/analysis document only — no behavioral changes.

[kilo-code-bot]

WARNING: Sidebar visibility detection is described inconsistently

The recommendation section later points to WebviewView.onDidChangeVisibility, and this extension already targets VS Code ^1.108.0. Framing sidebar visibility changes as impossible turns this from "not implemented today" into "cannot be done", which changes the conclusion of finding #2.

Suggested change

	- `WebviewView` (sidebar) does not expose `onDidChangeViewState` -- the extension cannot detect sidebar visibility changes at all
	- `WebviewView` (sidebar) is not currently using visibility APIs, so sidebar updates are never gated on visibility

[kilo-code-bot]

SUGGESTION: This bullet describes the wrap behavior backwards

A wider viewport means lines wrap less, so each rendered message is typically shorter rather than taller.

Suggested change

	- Text wraps less, producing taller rendered messages
	- Text wraps less, producing shorter rendered messages

[kilo-code-bot]

Code Review Summary

Status: 2 Issues Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	1
SUGGESTION	1

Fix these issues in Kilo Cloud

Issue Details (click to expand)

WARNING

File	Line	Issue
packages/kilo-vscode/docs/infrastructure/webview-tab-vs-sidebar-performance.md	42	Finding #2 says sidebar visibility cannot be detected, but the same doc later recommends WebviewView.onDidChangeVisibility, so the analysis currently overstates the limitation.

SUGGESTION

File	Line	Issue
packages/kilo-vscode/docs/infrastructure/webview-tab-vs-sidebar-performance.md	76	The bullet says less wrapping makes messages taller, but a wider viewport usually makes each rendered message shorter.

Other Observations (not in diff)

No issues found in unchanged code that required summary-only notes.

Files Reviewed (1 files)

• packages/kilo-vscode/docs/infrastructure/webview-tab-vs-sidebar-performance.md - 2 issues

---

_{Reviewed by gpt-5.4-20260305 · 437,344 tokens}