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Sweep 01 Oct 2026 · 17:27Z Build v2.1.287 508 read Stable v2.1.285 Latest v2.1.287 Next v2.1.287 Feeds RSS JSON llms.txt llms-full.txt Unofficial
HomeDocsClaude Code CLI 1 Oct 2026
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Connect Claude Code to tools via MCP changedmcp

Nearest release: v2.1.286, published 9 hours before upstream edited the page. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

Upstream edited this page at 1 Oct 2026 03:10 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 1 Oct 2026 03:37 UTC.

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First seen 14 Aug 2026 this site's first read of the page
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286286* **Hidden whitespace**: Claude Code warns when an MCP config value carries hidden leading or trailing whitespace, which often comes from pasting a token with a trailing newline. Claude Code checks `command`, `url`, each `args` entry, and the values and key names under `env` and `headers`. Claude Code shows the warning in `claude mcp list` output and in `/mcp`, naming the affected fields without echoing their values, for example `Leading or trailing whitespace in: headers.Authorization`. Claude Code doesn't trim the whitespace and uses the values exactly as written, so edit the configuration to remove it.
287287* **Same name in more than one scope**: if you define the same server name in more than one [scope](#mcp-installation-scopes) with different endpoints, Claude Code warns about the conflict in `claude mcp list` output and in `/mcp`. Claude Code stores OAuth sign-ins per endpoint, so when you authenticate the definition that loads in one project, you still need to sign in separately in a project where a different definition loads. Keep the endpoint you want and remove the others with `claude mcp remove <name> --scope <scope>`. In the warning, Claude Code quotes each scope's endpoint as written in your configuration, with [`${VAR}` references](#environment-variable-expansion-in-mcp-json) unexpanded, so it never shows a resolved value such as an API key.
288* **Reserved names**: Claude Code reserves the names of its built-in servers, including `workspace`, `claude-in-chrome`, `computer-use`, `Claude Preview`, and `Claude Browser`. If your configuration defines a server with a reserved name, Claude Code skips it at load time and shows a warning asking you to rename it. `claude mcp add` rejects a reserved name with an error. `Claude Preview` and `Claude Browser` both name the built-in server that the [Claude Code desktop app's preview pane](/docs/en/desktop#preview-your-app) uses. Before v2.1.205, `Claude Browser` wasn't reserved, so a user-configured server could register under that name.
288* **Reserved names**: Claude Code reserves the names of its built-in servers, including `workspace`, `claude-in-chrome`, `computer-use`, `Claude Preview`, and `Claude Browser`. If your configuration defines a server with a reserved name, Claude Code skips it at load time and shows a warning asking you to rename it. `claude mcp add` rejects a reserved name with an error. `Claude Preview` and `Claude Browser` both name the built-in server that the [Claude Code desktop app's preview pane](/docs/en/desktop#preview-your-app) uses.
289289* **Missing environment variable**: if a [`${VAR}` reference](#environment-variable-expansion-in-mcp-json) in a server's configuration names a variable that isn't set and has no `:-default`, Claude Code warns in `claude mcp list` output and in `/mcp`, naming the variable, and still loads the server with the `${VAR}` text unexpanded. Set the variable or add a `${VAR:-default}` fallback. In a remote server's `url` and `headers`, some credential variables [read as empty](#credential-variables-that-read-as-empty) instead, with no warning.
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291291#### Tool availability
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490490* **Multiple transport types**: support for stdio, SSE, HTTP, and WebSocket transports, though transport support may vary by server
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492492Plugin servers appear in `/mcp` with indicators showing they come from plugins.
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494For a plugin's stdio server, `claude mcp get` prints `Command: stdio`, an empty `Args:` line, and each environment variable as `NAME=[REDACTED]`. The values are hidden because they can carry credentials.
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494496**Plugin MCP tool names**:
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