fix(agent-manager): keep the loaded browser page across context switches

[marius-kilocode]

Issue

No tracking issue. This is a focused bug fix found while verifying the Agent Manager Integrated Browser.

Context

The Agent Manager Integrated Browser panel (right side panel) lost a loaded page after switching to another worktree, project, or session and back. The iframe reloaded from its URL, so the page and its in-page state reset. That made it hard to keep a locally built page open while moving between contexts.

Implementation

The side panel previously rendered one browser panel for the active session, so every context switch unmounted it and destroyed the iframe. The panel now keeps one browser panel alive per scope (project plus session), shows only the active scope, and retires entries when their session is gone, bounded by a small LRU. The side host also stays mounted while a cached panel is alive, so hiding the panel does not tear the iframe down.

Screenshots / Video

How to Test

Manual/local verification

• In an isolated VS Code instance, opened Agent Manager, opened the Integrated Browser panel for a worktree, and loaded a stateful local page (random load ID plus a sessionStorage counter).
• Switched to another worktree and back: the load ID and counter stayed the same. Before the fix, the counter incremented on return.
• Repeated with a Local to worktree switch, with the panel toggled closed and reopened, and with two worktrees each keeping a separate page.
• Ran bun run lint, bun run typecheck, bun run knip, and bun test tests/unit (6386 pass, 0 fail).

Reviewer test steps

1. Enable browser automation in Kilo settings.
2. Open Agent Manager and open the Integrated Browser panel for a worktree.
3. Load a local page (for example a dev server on localhost).
4. Switch to another worktree or project and back.
5. Confirm the page and its state are still there.

Checklist

• Issue linked above, or exception explained
• Tests/verification described
• Screenshots/video included for visual changes, or marked N/A
• Changeset considered for user-facing changes
• I personally reviewed the diff and can explain the changes, including any AI-assisted work.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (1 file)

• packages/kilo-vscode/webview-ui/agent-manager/BrowserPanel.tsx

Previous Review Summary (commit 3499a48)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit 3499a48)

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	0
SUGGESTION	1

Issue Details (click to expand)

SUGGESTION

File	Line	Issue
packages/kilo-vscode/webview-ui/agent-manager/BrowserPanel.tsx	221	Evicting/unmounting a cached browser panel disposes only local controller state; the extension-side browser context is never closed, so the 8-entry cache does not bound the heavier backend resource.

Files Reviewed (7 files)

• .changeset/agent-manager-browser-preserve.md - no issues
• packages/kilo-vscode/tests/unit/browser-panel-cache.test.ts - no issues
• packages/kilo-vscode/webview-ui/agent-manager/AgentManagerApp.tsx - no issues
• packages/kilo-vscode/webview-ui/agent-manager/BrowserPanel.tsx - 1 issue
• packages/kilo-vscode/webview-ui/agent-manager/browser-panel-cache.ts - no issues
• packages/kilo-vscode/webview-ui/agent-manager/side-panel-state.ts - no issues
• packages/kilo-vscode/webview-ui/browser/browser.css - no issues

Fix these issues in Kilo Cloud

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