deepseek-ai/deepseek-harness · error

mcp-client(${config.serverName}): initial connection or tool

Error message

mcp-client(${config.serverName}): initial connection or tool synchronization failed

What it means

Error "mcp-client(${config.serverName}): initial connection or tool synchronization failed" thrown in deepseek-ai/deepseek-harness.

Source

Thrown at packages/mcp/mcp-client/src/index.ts:179

  }, 'mcp-client.serverName')

  // The supervisor owns the client/transport generations, the reconnect
  // loop, and the live tool registrations; disposal stops reconnection,
  // quiesces in-flight work, and unregisters the current generation.
  const connection = startConnection(ctx, config, reconnect)

  ctx.effect(() => {
    return () => connection.dispose()
  }, 'mcp-client.connection')

  // Block plugin activation on the initial connection + tool discovery so
  // Cordis consumers observe the tools immediately after the fiber activates.
  // When failOnStartupError is true, a failed initial attempt rejects the
  // fiber (Cordis rolls it back); otherwise the error is logged and the
  // supervisor enters its reconnect loop.
  const outcome = await connection.ready
  if (outcome.error !== undefined && config.failOnStartupError) {
    throw new Error(`mcp-client(${config.serverName}): initial connection or tool synchronization failed`, { cause: outcome.error })
  }
}

View on GitHub (pinned to b150a551b8)

Solutions

1. Check the server command/URL, credentials, and the wrapped cause; fix and reload.

When it happens

Trigger: Thrown at packages/mcp/mcp-client/src/index.ts:179 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of deepseek-ai/deepseek-harness@b150a551b8 (2026-08-24). Data as JSON: /api/errors/43a22c4ace74bfd3. Report an issue: GitHub.