Connect Claude Code to tools via MCP changedmcp
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#### Mid-session drops of a remote server #### Failed first connections #### Failed discovery requests #### How Claude learns that a server failed
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349349### Automatic reconnection
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351If an HTTP or SSE server disconnects mid-session, Claude Code automatically reconnects with exponential backoff: up to five attempts, starting at a one-second delay and doubling each time. The server appears as pending in `/mcp` while reconnection is in progress. After five failed attempts the server is marked as failed and you can retry manually from `/mcp`. Stdio servers are local processes and are not reconnected automatically.
351Claude Code reconnects a remote server that drops mid-session and retries an HTTP or SSE server's first connection after a transient error. Stdio servers are local processes, and Claude Code doesn't reconnect them automatically.
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353The same backoff applies when an HTTP or SSE server fails its initial connection at startup. Claude Code retries the initial connection up to three times on transient errors such as a 5xx response, a connection refused, or a timeout, then marks the server as failed if it still can't connect. Authentication and not-found errors are not retried because they require a configuration change to resolve.
353#### Mid-session drops of a remote server
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355When a configured server fails to connect, Claude Code tells Claude which server failed and its connection error, including in `ToolSearch` results that find no matching tool, so Claude reports the connection failure in its response. Requires [tool search](#scale-with-mcp-tool-search), which is enabled by default. In configurations without tool search, such as a custom `ANTHROPIC_BASE_URL`, `ENABLE_TOOL_SEARCH=false`, or a model that doesn't support tool search, and on Amazon Bedrock, Google Cloud's Agent Platform, and Microsoft Foundry, Claude Code doesn't report failed server connections to Claude.
355Claude Code reconnects a dropped remote server with exponential backoff: up to five attempts, starting at a one-second delay and doubling it each time. What you see depends on how you're running Claude Code:
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357The capability discovery requests that run after a successful connection, such as `tools/list`, `prompts/list`, and `resources/list`, also retry transient network and server errors up to three times with short backoff. Authentication errors, 4xx responses, and request timeouts are not retried.
357* **In an interactive session**: `/mcp` shows the server as pending while Claude Code reconnects. After five failed attempts, Claude Code marks the server as failed, or as needing authentication when the server needs authorizing again. You can retry manually from `/mcp`.
358* **In [`claude -p`](/docs/en/headless) runs and [Agent SDK](/docs/en/agent-sdk/overview) sessions**: Claude Code reconnects on the same schedule, with no `/mcp` panel to show the attempts.
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360#### Failed first connections
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362When an HTTP or SSE server's first connection fails with a transient error, such as a 5xx response, a connection refused, or a timeout, Claude Code retries up to three times. If the connection still fails, Claude Code marks the server as failed. Claude Code retries this way at startup and when a server is added mid-session. That includes a server Claude Code adds to a [cloud session](/docs/en/claude-code-on-the-web) from its configuration and a server you add with the Agent SDK's [`setMcpServers()`](/docs/en/agent-sdk/typescript).
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364Claude Code doesn't retry in these cases:
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366* A WebSocket server's first connection
367* An authentication or not-found error, because it requires a configuration change to resolve
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369#### Failed discovery requests
370
371After a server connects, Claude Code sends it capability discovery requests such as `tools/list`, `prompts/list`, and `resources/list`. Claude Code retries those requests up to three times with short backoff after a transient network or server error. It doesn't retry authentication errors, 4xx responses, or request timeouts.
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373#### How Claude learns that a server failed
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375Whether Claude Code tells Claude about a configured server that failed to connect depends on [tool search](#scale-with-mcp-tool-search), which is on by default:
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377* With tool search, Claude Code tells Claude which server failed and its connection error, so Claude reports the connection failure in its response. Claude Code includes the same information in `ToolSearch` results that find no matching tool.
378* In any [configuration without tool search](#configure-tool-search), Claude Code doesn't report failed server connections to Claude.
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359380### Push messages with channels
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