perf(agent-manager): extend slimPart to strip heavy tool metadata for faster session switching

[marius-kilocode]

Summary

• Extend slim-metadata.ts to strip heavy metadata from 5 tool types (was edit-only), reducing IPC serialization cost on session switch by ~2x

Problem

Session switching in the Agent Manager was slow (400ms–1.4s) for sessions with many tool calls. Performance profiling revealed two bottlenecks:

1. VS Code IPC serialization — deserializeWebviewMessage + deserializeRequestJSONArgs dominated the Chrome profiler (24% + 19% self-time), caused by large tool part payloads containing full file contents
2. Solid.js reactive render cascade — setCurrentSessionID() triggers synchronous re-rendering of all message components

This PR fixes bottleneck #1. The existing slimPart() function only stripped edit tool metadata. These tools were sending massive unfiltered payloads:

Tool	Unstripped field	Typical size
apply_patch	metadata.files[].before/after/diff	Entire file contents × N files
apply_patch	input.patchText	Full multi-file patch
multiedit	metadata.results[] (nested edit metadata)	N × full file diffs
write	input.content	Entire file content
bash	metadata.output / state.output	Up to 30KB / 50KB

Profiling Results

Measured by adding [Kilo Perf] timing instrumentation across the full session-switching pipeline (webview + extension), then comparing before/after.

selectSession (cached sessions, diff panel closed)

Session	Parts	Before	After	Speedup
167 msgs, 607 parts	607	782–1195ms	427–520ms	~2.2x
92 msgs, 328 parts	328	431–471ms	157–213ms	~2.5x
164 msgs, 593 parts	593	1061–1191ms	490–533ms	~2.2x

handleMessagesLoaded round-trip

• Before: 95–280ms typical
• After: 62–146ms typical

Chrome Performance profiler

Before the fix, deserializeWebviewMessage (24.1% self-time) and deserializeRequestJSONArgs (19.4%) were the top two activities. After the fix, serialization is no longer the dominant cost.

What's stripped per tool

Tool	Stripped	Kept for rendering
edit	filediff.before/after, diff	filediff.{file,additions,deletions}, diagnostics, input.oldString/newString (fallback diff)
apply_patch	files[].before/after/diff, input.patchText	files[].{filePath,relativePath,type,additions,deletions,movePath}, diagnostics
multiedit	results[].filediff.before/after, results[].diff	results[].{filediff summary, diagnostics}
write	input.content	input.filePath, diagnostics
bash	Truncates metadata.output and state.output to 4KB	First 4KB with truncation marker

Cloud sessions are unaffected — they use a separate data path.

[kilo-code-bot]

Code Review Summary

Status: 3 Issues Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	3
SUGGESTION	0

Issue Details (click to expand)

WARNING

File	Line	Issue
packages/kilo-vscode/src/kilo-provider/slim-metadata.ts	69	apply_patch slimming removes the snapshots that the webview diff viewer needs, so patch parts expand to an empty body after a session reload.
packages/kilo-vscode/src/kilo-provider/slim-metadata.ts	120	Clearing write tool input.content leaves completed write parts with no file preview after switching away and back.
packages/kilo-vscode/src/kilo-provider/slim-metadata.ts	133	Truncating bash state.output to 4 KB makes reloaded shell parts lose most logs, and the webview has no fallback to fetch the full output.

Fix these issues in Kilo Cloud

Other Observations (not in diff)

No additional issues outside the diff.

Files Reviewed (1 files)

• packages/kilo-vscode/src/kilo-provider/slim-metadata.ts - 3 issues

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_{Reviewed by gpt-5.4-20260305 · 1,490,424 tokens}