Luna Code — AI Coding Agent for VS Code

Luna Code is a Claude Code-style agentic coding assistant that runs entirely on OpenRouter. Point it at any model OpenRouter supports with just an API key and a model id — no other configuration required.

It's built for fast codebase navigation, efficient agentic sessions, and prompt-cache hit optimization so long sessions stay cheap and fast.

Features

• One-line setup. Paste an OpenRouter API key, pick a model, go.
• Three modes
  • Standard — approve each file edit and shell command before it runs.
  • Auto — runs edits and commands autonomously without prompting (commands in lunacode.alwaysDenyCommands are still hard-blocked).
  • Plan — read-only research + planning. The agent investigates the code and proposes a concrete plan, but can't edit files or run mutating commands.
• Session history. Every conversation is saved per-workspace. Click the history button in the header to browse, reload, or delete prior sessions.
• Usage & cost analytics. A live meter shows session-total cost plus the last turn's tokens and cache-hit rate. The usage window (bar-chart button) reports spend and tokens over the last 30 / 60 / 90 days, with a daily cost chart, daily token chart, and a per-model cost/usage breakdown.
• Refined "thinking" UX. While the model reasons, an animated Thinking… indicator sits just above the composer; when it finishes it collapses to a quiet "Thought for Ns" marker — no noisy, expandable reasoning blocks.
• Agentic tool loop. Reads files, lists/globs/greps the workspace, runs builds & tests, checks language-server diagnostics, and edits code — looping until the task is done.
• Cache-hit optimized. A stable system-prompt prefix plus rolling cache_control breakpoints maximize provider prompt caching (Anthropic / Gemini via OpenRouter; automatic for OpenAI). The composer shows a live cache hit % and token/cost meter.
• Context management. Automatically compacts older tool output and turns to stay within a configurable token budget.
• Modern UI. A clean neutral-dark interface with purple accents, streaming responses, collapsible reasoning, tool cards, and inline diff approvals.
• Open anywhere. Use Luna Code in the Activity Bar sidebar or pop it out into an editor tab (button in the panel title bar). To dock it on the right like Claude Code, drag the Luna Code icon into the Secondary Side Bar — VS Code remembers the placement. All surfaces share one live session.
• Private by default. Every request sends OpenRouter provider.data_collection: "deny", so traffic is only routed to providers that do not store or train on your prompts. An optional stricter Zero-Data-Retention (ZDR) mode is available.
• Secure. Your API key is stored in VS Code's encrypted SecretStorage, never in settings or files.

Getting started

1. Build the extension:

   npm install
   npm run compile
   

2. Press F5 in VS Code to launch the Extension Development Host.
3. Click the Luna Code icon in the Activity Bar.
4. Click Set OpenRouter API Key and paste your key (sk-or-v1-…).
5. Click the model chip in the header to pick a model (or browse all OpenRouter models).
6. Type a request and hit Enter.

Keyboard shortcuts

Configuration

All settings live under the lunacode.* namespace (Settings → Extensions → Luna Code):

Tools the agent can use

Mutating tools are hidden entirely in Plan mode and gated by approval in Standard mode.

How cache optimization works

OpenRouter forwards cache_control breakpoints to providers that support prompt caching. Luna Code:

1. Keeps the system prompt + tool definitions byte-stable across a session and marks the end of the system prompt as a cache breakpoint.
2. Places a rolling breakpoint on the latest message each request so the entire accumulated conversation becomes a cached prefix for the next call.
3. Only ever appends to the message list, never reorders, so prefixes stay valid for cache reuse.

For OpenAI models, caching is automatic and these hints are safely ignored.

Project structure

src/
  extension.ts            activation + commands
  config.ts               settings + SecretStorage for the API key
  modes.ts                Standard / Auto / Plan definitions
  openrouter/
    client.ts             streaming Chat Completions client
    types.ts              message + cache_control types
  agent/
    agent.ts              the agentic tool loop
    systemPrompt.ts       system prompt (stable cache prefix)
    contextManager.ts     cache breakpoints + context compaction
    tools/                read/write/edit/list/glob/grep/run/diagnostics
  webview/
    provider.ts           webview host + approval bridge
    protocol.ts           host <-> webview message types
    ui/                   the webview front-end (main.ts, markdown.ts)
media/
  webview.css             the dark-purple theme

License

MIT