Claude Code's OpenTelemetry export now carries `tool_source` and `message.uuid` — you can finally attribute a tool call to its origin

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Version 2.1.214 added `message.uuid`, `client_request_id`, and `tool_source` attributes to OpenTelemetry log events, giving message-level correlation and tool provenance, plus `CLAUDE_CODE_OTEL_CONTENT_MAX_LENGTH` to configure the 60 KB truncation limit on content attributes. `tool_source` is the interesting one: it lets you distinguish a built-in tool call from an MCP server's, which is the join key you need to answer 'which connector is burning my tokens' or 'which server did the agent call right before it went off the rails.' The same release also added reasoning effort to the `subagentStatusLine` payload, so custom agent rows can render model and effort per subagent.