GitHub Copilot in VS Code

Route GitHub Copilot's code completions and chat requests in VS Code through Isartor, so repetitive prompts are deflected locally via the L1a/L1b cache layers. This reduces cloud API calls, lowers latency for repeated patterns, and gives you per-tool visibility in isartor stats.

How is this different from Copilot CLI? The Copilot CLI integration uses an MCP server for the terminal-based copilot command. This page covers VS Code — the editor extension that provides inline completions and Copilot Chat.

Prerequisites

• Isartor installed and running (isartor up --detach)
• GitHub Copilot VS Code extension installed (requires a Copilot subscription)
• An LLM provider API key configured in Isartor for Layer 3 fallback (isartor set-key -p openai or similar)

Step 1 — Start Isartor

# Install (if not already)
curl -fsSL https://raw.githubusercontent.com/isartor-ai/Isartor/main/install.sh | sh

# Configure your LLM provider key (OpenAI, Anthropic, Azure, etc.)
isartor set-key -p openai

# Start the gateway in the background
isartor up --detach

Verify it's running:

curl http://localhost:8080/health
# {"status":"ok", ...}

Step 2 — Configure VS Code

Recommended:

isartor connect copilot-vscode

This command:

• auto-detects the VS Code settings.json path on macOS, Linux, and Windows
• backs up the original file to settings.json.isartor-backup
• writes the three github.copilot.advanced.debug.* overrides
• refuses to write if Isartor is not reachable

Manual alternative: open your VS Code User Settings (JSON) and add:

{
  "github.copilot.advanced": {
    "debug.overrideProxyUrl": "http://localhost:8080",
    "debug.overrideCAPIUrl": "http://localhost:8080/v1",
    "debug.chatOverrideProxyUrl": "http://localhost:8080/v1/chat/completions"
  }
}

Custom port? If Isartor runs on a different port, replace 8080 with your port everywhere above.

Step 3 — Restart VS Code

Close and reopen VS Code (or run "Developer: Reload Window" from the command palette). Copilot will now route requests through Isartor.

Step 4 — Verify

Open any code file and trigger a Copilot suggestion (start typing a comment or function). Then check Isartor's stats:

isartor stats

You should see requests flowing through Isartor's layers. Repeat the same prompt and you'll see L1a cache hits — Isartor deflected the duplicate without a cloud call.

For per-tool breakdown:

isartor stats --by-tool

Copilot VS Code traffic appears as copilot in the tool column (identified from the User-Agent header). The table now includes requests, cache hits/misses, average latency, retries, errors, and L1a/L1b safety.

How It Works

VS Code Copilot Extension
        │
        ▼ (HTTP request to overrideProxyUrl)
   ┌─────────────┐
   │   Isartor    │
   │  Gateway     │
   │              │
   │  L1a ──► L1b ──► L3 (Cloud)
   │  hit?    hit?    forward
   └─────────────┘
        │
        ▼
   Response back to VS Code

1. Copilot sends completion/chat requests to Isartor instead of GitHub's servers
2. L1a Exact Cache — sub-millisecond hit for identical prompts (< 1 ms)
3. L1b Semantic Cache — catches variations of the same prompt (1–5 ms)
4. L3 Cloud — only genuinely new prompts reach your configured LLM provider
5. Response flows back to Copilot transparently — no change to the editor UX

Disconnecting

isartor connect copilot-vscode --disconnect

If a backup exists, Isartor restores it. Otherwise it removes only the three managed github.copilot.advanced.debug.* keys.

Benefits

Advanced Configuration

Use a specific LLM provider for Layer 3

Isartor routes surviving (non-cached) prompts to your configured L3 provider. You can use any supported provider:

# OpenAI (default)
isartor set-key -p openai

# Anthropic
isartor set-key -p anthropic

# Azure OpenAI
export ISARTOR__LLM_PROVIDER=azure
export ISARTOR__EXTERNAL_LLM_URL=https://<resource>.openai.azure.com
export ISARTOR__AZURE_DEPLOYMENT_ID=<deployment>
isartor set-key -p azure

Adjust cache sensitivity

Tune the semantic cache threshold to control how similar a prompt must be to trigger an L1b hit:

# Default: 0.92 (higher = stricter matching)
export ISARTOR__SIMILARITY_THRESHOLD=0.90

See the Configuration Reference for all available options.

Enable monitoring

export ISARTOR__ENABLE_MONITORING=true
export ISARTOR__OTEL_EXPORTER_ENDPOINT=http://otel-collector:4317

See Metrics & Tracing for Grafana dashboards and OTel setup.

Known Limitations

1. Copilot Chat override — The debug.chatOverrideProxyUrl setting may not be fully respected by all versions of the Copilot Chat extension (tracking issue). Inline code completions (debug.overrideCAPIUrl) work reliably. If chat requests bypass Isartor, try using the global VS Code proxy setting as a workaround:

   {
     "http.proxy": "http://localhost:8080"
   }
   

   Note: This routes all VS Code HTTP traffic through Isartor, not just Copilot. Use a PAC script if you need finer control.

2. Authentication — These debug.* settings bypass Copilot's normal GitHub authentication. Isartor handles the LLM provider auth via its own API key configuration. Your Copilot subscription is still required for the extension to activate.

3. Extension updates — VS Code may update the Copilot extension automatically. If the proxy stops working after an update, verify the settings are still present in settings.json and restart VS Code.

Troubleshooting

Reverting

To stop routing Copilot through Isartor, remove the github.copilot.advanced block from your settings.json and reload VS Code:

// Remove this entire block:
"github.copilot.advanced": {
    "debug.overrideProxyUrl": "http://localhost:8080",
    "debug.overrideCAPIUrl": "http://localhost:8080/v1",
    "debug.chatOverrideProxyUrl": "http://localhost:8080/v1/chat/completions"
}