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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

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Claude Code v2.1.6 13 Jan 2026

MCP Logging Infrastructure

Added structured logging for MCP (Model Context Protocol) server errors and debug messages.

Details

New logMCPError() and logMCPDebug() functions for server-specific logging
MCP logs stored separately per server in mcp-logs-{serverName} directories
Error log sink initialization with buffering for early errors before sink is ready

Evidence

Lq9() at line 536969 (error log sink initialization, contains logMCPError, logMCPDebug)

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.6 →