With Runtime connected, Claude in the browser can create a Linux sandbox, run code in it, and return files. No API key is pasted anywhere. The connector signs in through your browser and receives a key of its own. The key is listed by name on your keys page and can be revoked in one click. Every new account gets 100 free hours of a 1 GB machine in its first 30 days with no card, as of 25 October 2026 (trial).
Add the connector
On a Pro or Max plan:
- In Claude, go to Customize > Connectors.
- Choose + Add, then Add custom connector.
- Enter a name, such as Runtime, and the remote MCP server URL:
https://api.withruntime.com/mcp. Choose Continue, then Continue again on the detected authentication settings. - Keep the recommended OAuth client, Use Claude's published identity. Runtime's sign-in accepts client metadata documents and dynamic client registration, so it needs no client ID or secret.
- Choose Add.
Claude then opens a Runtime page in your browser:
- Sign in to Runtime, or create an account.
- The page shows which app is asking and where the key goes. Check that it names Claude, then approve Connect.
- Back in Claude, every Runtime tool appears.
On a Team or Enterprise plan
Only an owner of the Claude organization adds a custom connector (on Enterprise, also a role with Manage access to Libraries):
- Organization settings > Connectors, then Add.
- Hover over Custom and choose Web.
- Enter a name and
https://api.withruntime.com/mcp, choose Continue twice, then Add.
Each member then opens Customize > Connectors, finds Runtime in the list, and chooses Connect. Every member approves on Runtime with their own sign-in. Each gets a separate key that can be revoked alone. Invite members to your Runtime account first, so the connection lands in the shared account. See how to invite your team.
Use it in a chat
Turn the connector on from the + button at the lower left of the chat box, under Connectors. Then ask in plain words:
Create a Runtime sandbox, install pandas, load this CSV and plot revenue by month. Stop the sandbox when you are done.
Claude calls the tools itself. The ones it uses most:
| Tool | What Claude does with it |
|---|---|
runtime_sandboxes_create |
Starts a sandbox and waits until it is running |
runtime_sandboxes_exec |
Runs a command and reads the exit code and output |
runtime_sandboxes_files_write |
Puts your code or data into the sandbox |
runtime_sandboxes_files_read |
Reads results back |
runtime_sandboxes_interpreter_run |
A notebook-style cell; charts come back as images |
runtime_sandboxes_previews |
An HTTPS address for an app it started on a port |
runtime_sandboxes_manage |
Stops, pauses or wakes the sandbox |
runtime_account |
Your free usage left and your credit |
runtime_docs_read |
Any page of Runtime's docs, when it needs to check a detail |
The server answers Claude's first contact with instructions: the quick start,
how to retry safely, and how to report a problem. That is why Claude knows to
check exitCode and to stop a sandbox at the end.
How the connection works
| Fact | Detail |
|---|---|
| Endpoint | https://api.withruntime.com/mcp, MCP Streamable HTTP |
| Sign-in | OAuth 2.1 with PKCE and dynamic client registration |
| Where Claude calls from | Anthropic's cloud, not your computer |
| Credential | A key for a new agent named after the app |
| What it can do | Manage resources and spend prepaid credit across the account |
| Revoke | API keys, where it is listed by name |
| Free Claude plan | One custom connector |
Because Claude reaches the server from Anthropic's cloud, nothing is installed on your machine. The connector works wherever you use the same Claude account.
Mistakes and how Runtime handles them
- Approving a request you did not start. The approval page names the app. Approve only when it is the Claude you just used.
- Worrying about spend. Set a daily spending limit on the connector's row
at API keys. Past the limit, a create or wake fails with
spending_limit_reached, and nothing is charged. - Leaving sandboxes running. Ask Claude to stop them, or let them pause. A sandbox pauses itself after 300 seconds with nothing happening in it, and then stops paying the running rate.
- Tools with old names in a saved prompt. On 24 September 2026, every tool
took its product's name, such as
runtime_sandboxes_exec. A call to an old name fails and names the new one.
Related
- How to add Runtime to Cursor
- Claude Code in a sandbox for Claude Code in a terminal
- Code interpreter for chatbots
- Runtime Cloud MCP
Sources
Checked 25 October 2026.
- Getting started with custom connectors using remote MCP, Claude Help Center
Facts on this page were checked on 25 October 2026.