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cv4vs Agents

Architecture & build

How the extension is put together, and how to build it from source. For what it does, see the home page.

Tech & performance

Section titled “Tech & performance”
  • Host: C# / .NET Framework 4.8 Visual Studio package (VSIX) for Visual Studio 2022 and 2026 (VS 17.0+).
  • Chat UI: a WebView2 app built with Lit web components and Fluent UI Web Components, so the UI matches Visual Studio’s look and adapts to the active theme (light/dark). Fluent components are kept pure (no custom colour overrides), so theming stays consistent.
  • TypeScript end to end, bundled by esbuild into a single IIFE dist/bundle.js; the host↔web message contracts are generated from the C# source (one source of truth, no hand-kept duplicates).
  • CLI pane: a real terminal via ConPTY (Microsoft.Terminal.Wpf), so the interactive CLI renders exactly as in a native shell.
  • Lazy everything, by design. The guiding principle is nothing is built, read or started until it’s actually needed: the extension is meant to be fast, fast, fast. Everything loads on demand and tears down when idle; work you don’t do costs nothing.
  • Tuned for performance and low memory:
    • Chat history is lazy: pages of 50 read from the .jsonl on demand, heavy blocks (images, sub-agent transcripts, full diffs) fetched only when opened; nothing loaded up front.
    • Session metadata is read with head+tail 64 KB windows, never loading whole files.
    • The MCP server and event listeners start/stop lazily on the first/last open pane.
    • The WebView is Shadow-DOM + static styles, minimising reflow and style recalculation; CSS/TS are kept lean (linted, no dead rules) for fast paint and small bundles.

How the CLI is started

Section titled “How the CLI is started”
  • Settings are loaded from the user, project and local files (--setting-sources user,project,local), so your permissions.allow and deny apply as in a terminal.
  • The IDE tools (mcp__vs__*) are pre-approved: they never raise a permission prompt, in any mode.
  • A profile’s variables are applied first and the extension’s own last, so a profile cannot override CLAUDE_CODE_ENTRYPOINT (nor, in a CLI pane, FORCE_CODE_TERMINAL and CLAUDE_CODE_SSE_PORT). CLAUDE_CODE_ENABLE_SDK_FILE_CHECKPOINTING is set only while Keep file checkpoints is on.
  • Visual Studio started from inside a Claude Code session does not pass that session’s identity on: CLAUDECODE, CLAUDE_CODE_SESSION_ID, CLAUDE_CODE_CHILD_SESSION and the related variables are removed from every claude.exe it starts.
  • A resumed session starts in the permission mode it was last in, read from its transcript; a new one in Initial permission mode.
  • The CLI runs in a job object: it is killed with Visual Studio, never left behind.

Build

Section titled “Build”

Everything builds from a single solution; the WebView build is hooked into MSBuild.

Terminal window
# Build the VSIX (also runs the WebView build via the BuildWebViewSrc MSBuild target)
msbuild cv4vs-agents.slnx /t:Build /p:Configuration=Debug
# F5 in Visual Studio launches a second (experimental) VS instance with the extension loaded.

WebView UI (src/Corsinvest.VisualStudio.Agents/Chat/WebViewSrc/):

Terminal window
npm run build       # gen-bridge + esbuild → dist/bundle.js
npm run dev         # esbuild --watch while iterating on the chat UI
npm run typecheck
npm run lint

Requirements: the CLI is installed separately (npm i -g @anthropic-ai/claude-code) and driven with the claude-vscode entrypoint.