Sweep 19 Sep 2026 · 02:36Z Build v2.1.278 500 read Stable v2.1.267 Latest v2.1.278 Next v2.1.278 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.275 ·

Attachment builder drops a tool-availability gate around pending MCP names

Pending MCP server names are now always included when building tool-availability updates

TierUnder the hoodhow much it should matter to you
Useful1my rating, 1 to 5
Signal1worth watching, 1 to 5
AreaMCPwhat it touches
KindInternal Changesin v2.1.275,
Under the hood

Pending MCP server names are now always included when building tool-availability updates

What

The code that builds the list of tool changes sent to Claude (the "deferred tools delta") used to only include the names of pending MCP clients (external tool servers still connecting) when a certain tool-availability check was false. That check has been removed, so pending MCP client names are now always included. A related keepMcp flag used when stripping tools is also now hard-coded to true.

Why

This means information about MCP servers that are still connecting is passed through more consistently, though the finding doesn't specify the downstream effect of always including it.

How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtThe finding does not say what visible difference this makes to the tools Claude sees during a session.

See this entry in the whole of v2.1.275 →