Source: github.com/anthropics/claude-code/releases/tag/v2.1.302
The release adds CLAUDE_CODE_AUTO_MODE_MODEL, which sets the model for the client-side auto mode classifier. It does not change the model used for server-side auto mode. A new Idle compaction row in /config lets users turn idle compaction off or back on.
Fork subagents, invoked with subagent_type: "fork", are now on by default in claude -p, the Agent SDK, the desktop app and VS Code. Setting CLAUDE_CODE_FORK_SUBAGENT=0 turns them off. The desktop app and VS Code now run a main conversation's subagents in the background, matching the terminal.
Fixes include MCP servers that negotiate protocol version 2026-07-28 but omit resultType, ttlMs or cacheScope, which could show no tools or fail every tool call. The Read tool no longer loads image files of any size fully into memory, and image sources over 128 MB are refused. Other fixes cover Vertex and Bedrock mid-session switches and cloud session cost tracking.
Why it matters if you build agents
Teams using a separate model for the auto mode classifier can now set it with an environment variable instead of relying on the default. Agents that rely on subagents in the Agent SDK or claude -p will see fork subagents enabled by default, so CLAUDE_CODE_FORK_SUBAGENT=0 is the switch to keep the previous behavior.
Developers with MCP servers on protocol version 2026-07-28 should check that their tools still appear after upgrading, since this release fixes cases where they did not.
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