In one sentence
Third-party agents is a mechanism to line up coding agents other than Copilot alongside Copilot's workflow.
The primary examples are Anthropic Claude and OpenAI Codex. They can be launched from both VS Code and GitHub with the same feel as Copilot.
The important thing is that this is not a mode of Copilot Chat. This is about which provider / harness to hand a task to. Billing, rate limits, and governance are all consolidated on the Copilot subscription side.
Enabling (Enterprise / Org / Personal)
Third-party agents are OFF by default. Before using them, an admin at the appropriate contract level must permit them via policy. Controlled through a 3-tier governance hierarchy.
| Level | Who configures | Where | What happens |
|---|---|---|---|
| 🏢 Enterprise | Enterprise owner | Enterprise → Policies → Copilot | Sets an upper bound for all orgs underneath (Allow / Block / No policy) |
| 🏛️ Organization | Org owner | Organization → Settings → Copilot → Coding agent | Individually enable/disable Claude / Codex for org members |
| 👤 Personal (Pro / Pro+) | The user | Settings → Copilot → Cloud agent → Partner agents | Enable via toggle for your own repos |
⚠️ VS Code local agents (Claude / Codex sessions running within chat) are outside the scope of this policy. Local control is handled through VS Code settings (e.g.,
github.copilot.chat.claudeAgent.enabled).
VS Code × OpenAI Codex
To use Codex from VS Code, install the OpenAI Codex extension and choose “Sign in with Copilot” at launch. Logging in via Copilot means no separate OpenAI account or billing is needed.
Steps
- Install the OpenAI Codex extension from the VS Code Marketplace
- Launch the extension and click “Sign in with Copilot”
- A Codex session appears in the Agent Sessions view
Key points
- 🧩 Extension installation required (OpenAI Codex extension from the Marketplace)
- 🤖 Available models are OpenAI series only:
Auto/GPT-5.2-Codex/GPT-5.3-Codex/GPT-5.4/GPT-5.4 nano - 🌐 All requests go via the Copilot API — GitHub billing applies
VS Code × Claude Code
In the VS Code Chat Session Type picker, just select Claude instead of Local. No extension installation required — it’s directly integrated into Copilot Chat.
Steps
- Open the Chat view and click New Chat (
+) - Select
Claudefrom the Session Type dropdown - Enter a prompt → Claude Agent SDK runs directly on the workspace
Key points
- 🧩 No extension needed — Natively integrated into Copilot Chat (unlike Codex, nothing to install from the Marketplace)
- 🤖 Available models:
Auto/Claude Opus 4.5/Claude Opus 4.6/Claude Opus 4.7/Claude Sonnet 4.5/Claude Sonnet 4.6 - 🌐 All requests go via the Copilot API — GitHub billing applies
- 🛡️ Permission mode is selectable: Edit automatically / Request approval / Plan
- ⚙️ Claude-specific slash commands are available
Cloud Agent × Codex / Claude SDK
When delegating a task to GitHub’s Cloud Agent, you can choose Copilot / OpenAI Codex SDK / Claude Agent SDK as the harness. The Cloud Agent framework (runs on GitHub Actions, returns a PR) stays the same — only the underlying agent implementation is swapped out.
Choosing the right option
| Harness | Strengths | Best for |
|---|---|---|
| Copilot | Standard harness optimized for GitHub | Default choice, Issue → PR automation |
| OpenAI Codex SDK | Optimized for the Codex model family | Long coding-focused tasks |
| Claude Agent SDK | Anthropic’s agentic loop | Implementations requiring extensive reasoning |
Shared benefits
- ☁️ Execution environment is the same as Cloud Agent (GitHub Actions runner)
- 🔐 Security and validation tools (CodeQL / Code Review / Secret Scanning / Dependency checks) apply the same safety net
- 💰 Billing is consolidated on the Copilot side