Use Claude Opus 4.8, Claude Sonnet 4.6, and Claude Haiku 4.5 in VS Code Copilot Chat — powered by OpenRouter with Anthropic prompt caching.

Features

✨ Three Anthropic models in Copilot Chat:

Claude Opus 4.8 — Most capable, best for complex reasoning and analysis
Claude Sonnet 4.6 — Fast and balanced, excellent for coding and general tasks
Claude Haiku 4.5 — Ultra-fast and efficient, perfect for quick tasks and high-volume work

🚀 Anthropic prompt caching built-in:

~90% savings on repeat context in multi-turn sessions via Anthropic's native prompt caching
Provider pinning — locks requests to Anthropic-direct so caches accumulate and reuse across turns
Frontier models only — optimized for the latest Anthropic Claude family (Opus 4.8, Sonnet 4.6, Haiku 4.5)
Fully tunable — adjust caching and routing via VS Code settings without rebuilding

Quick Setup (60 seconds)

1. Get an API key

Visit https://openrouter.ai/keys (free sign-up)

2. Set it in VS Code

Option A (Easiest): Environment variable

# Windows PowerShell (add to profile)
$env:OPENROUTER_API_KEY = "sk-or-..."

Option B: VS Code command Ctrl+Shift+P → "OpenRouter: Set API Key" → paste your sk-or-... key → reload window

The extension checks the environment variable first, then falls back to the stored key.

3. Start coding

Pick an OpenRouter model in Copilot Chat and ask away!

Configuration

All settings are optional — sensible defaults work out of the box:

Setting	Default	Description
`vscode-openrouter.enablePromptCaching`	`true`	Use Anthropic `cache_control` on stable prefix (saves 90% on cache hits)
`vscode-openrouter.providerOrder`	`["anthropic"]`	Pin `anthropic/*` models to Anthropic-direct so caches reuse
`vscode-openrouter.allowFallbacks`	`true`	Fall back to other providers if primary is down (costs full price that turn)

Press Ctrl+, and search openrouter to adjust.

How It Works

This extension registers a custom VS Code Language Model Chat Provider
When you pick an OpenRouter model, your message is sent to openrouter.ai/api/v1/chat/completions
Your API key is stored securely in the OS credential store (Windows Credential Manager, macOS Keychain, etc.)
Anthropic prompt caching is enabled — the system instructions + tools block is cached on the first turn, then reused at ~90% discount on subsequent turns

Commands

Command	Description
`OpenRouter: Set API Key`	Store your API key securely
`OpenRouter: Clear API Key`	Remove the stored key

Troubleshooting

"No API key configured"

Run Ctrl+Shift+P → OpenRouter: Set API Key and paste your key from https://openrouter.ai/keys

"401 Unauthorized"

Your API key is invalid or expired
Check https://openrouter.ai/keys to confirm it's active
Re-run OpenRouter: Set API Key with the correct key

Models not appearing

Reload: Ctrl+Shift+P → Developer: Reload Window

Slow responses

Check OpenRouter status
Try a different model to isolate the issue

System Requirements

VS Code 1.90.0 or later
OpenRouter API key (free at https://openrouter.ai)

License

MIT

npm run compile
npm run package
code --install-extension vscode-openrouter-1.0.0.vsix

Reload VS Code after reinstalling.

Architecture

Entry point: src/extension.ts
API key storage: context.secrets (VS Code Secret Storage → OS Credential Manager)
Provider registration: vscode.lm.registerLanguageModelChatProvider('openrouter', provider) on activation
Streaming: Node https module, parses SSE data: lines, emits LanguageModelTextPart and LanguageModelToolCallPart via progress.report()
Message conversion: toOpenAIMessages() converts VS Code's LanguageModelChatRequestMessage format (including ToolCallPart / ToolResultPart) to OpenAI-compatible message array
Minimum VS Code version: 1.90.0