Claude Code v2.1.212 Major Updates

This is Ishikawa from the Cloud Business Division. Claude Code v2.1.212 (released 2026-07-16) has been released. This is a content-rich release that includes new features led by a revamped /fork, along with security fixes related to plan mode and worktrees, as well as numerous bug fixes and improvements.

Update Summary

v2.1.212 includes 48 changes. /fork now copies the conversation to an independent background session, and the former in-session subagent has been separated out as /subtask. Additionally, per-session limits for WebSearch and subagents to prevent runaway loops, and a mechanism to automatically background MCP calls that run long, have been added. Security fixes around permissions are also included, such as plan mode executing file-modifying commands without authorization, so updating is recommended.

Highlighted Updates

• New Features: /fork now copies the conversation to a new background session (the former in-session subagent has been separated as /subtask), and per-session limits for WebSearch and subagents, as well as automatic backgrounding of MCP calls exceeding 2 minutes, have been added.
• Bug Fixes: Fixed an issue where conversations with many images would incorrectly fail with "Request too large," and an issue where editing a file read with offset/limit specified would incorrectly show "File has not been read yet."
• Security: Fixed an issue where plan mode would automatically execute file-modifying Bash commands such as touch or rm without going through a permission prompt, and an issue where worktree creation could follow symlinks in .claude/worktrees to create files outside the repository.

Update Details

New Features

• /fork Converted to Background Session and /subtask Separated: /fork now copies the conversation to a new background session (an independent entry in claude agents) while you continue working. The in-session subagent that /fork previously launched has been separated into /subtask. In other words, two different use cases that one command /fork was handling have been split into two commands.

• Automatic Backgrounding of MCP Calls: MCP tool calls that run for more than 2 minutes are now automatically moved to the background, keeping the session operable. The threshold can be changed or disabled via CLAUDE_CODE_MCP_AUTO_BACKGROUND_MS.
• Per-Session Limit for WebSearch: A per-session limit (default 200, adjustable via CLAUDE_CODE_MAX_WEB_SEARCHES_PER_SESSION) has been added to WebSearch tool calls to prevent runaway search loops.
• Per-Session Limit for Subagent Launches: A per-session limit (default 200, overridable via CLAUDE_CODE_MAX_SUBAGENTS_PER_SESSION) has been added to subagent launches. This prevents runaway delegation loops, and the budget is reset with /clear.
• /resume in Agent View: Entering /resume in Agent View now opens a picker for past sessions (including ones removed from the list), allowing you to resume a selected session as a background session.
• Addition of claude auto-mode reset: claude auto-mode reset has been added to reset auto mode settings to their defaults. A confirmation prompt is displayed upon execution (skippable with --yes).

Security

• Fixed Unauthorized File Modifications in Plan Mode: Fixed a bug where plan mode would automatically execute file-modifying Bash commands such as touch or rm without going through a permission prompt or the SDK's canUseTool callback.
• Fixed Symlink Following During Worktree Creation: Fixed a bug where worktree creation could follow symlinks committed to the repository at .claude/worktrees to create files outside the repository.
• Expanded Scope of Enterprise forceLoginMethod: Enterprise forceLoginMethod now applies to logins via VS Code extension, SDK, setup-token, and install-github-app, not just the terminal.

Improvements

• Improved Reliability of Web Search and Web Fetch: 529 errors and rate-limited requests are now retried with capped backoff.
• Improved Prompt Caching: Mid-conversation system blocks now work behind LLM gateways and custom base URLs (Bedrock, Vertex, 1P).
• Reduced Token Usage in Inter-Agent Messaging: The body of SendMessage is no longer duplicated into replayed history or tool results, reducing token usage.
• Status Display in Agent View: Sessions awaiting a prompt from sandbox, MCP input, or managed-settings now display as "Needs input" instead of "Working," including in claude agents --json.
• Model Switching in Headless/SDK: set_model control requests are now applied mid-turn, so the new model is used without waiting for the next turn.
• Other changes include immediate transcript display on cold attach of background agents, naming of /fork copies, reopening of /btw, recording of inference effort in transcripts, authentication panel title changes, and a correction to release notes regarding tmux synchronized output.

Fixes

• Fixed "Request too large" for Many Images: Fixed a bug where conversations with many images would incorrectly fail with a "Request too large" error, and improved the error message to explain the actual cause.
• Fixed False Positive "File has not been read yet": Fixed a bug where editing a file that was read with offset/limit specified before resuming a session would incorrectly produce a "File has not been read yet" error.
• Fixed Error Injection in Web Search/Fetch: Fixed a bug where, during API overload, web search or web fetch would return "API Error" text as search results or page content.
• Fixed Reopening of Stopped Background Sessions: Fixed a bug where silently reopening a stopped session from Agent View would fail without any message. It now asks whether to resume, or displays the reason it cannot be resumed and offers the option to force a restart.
• Fixed /background Launch Failure on Windows: Fixed a bug where /background or claude --bg would fail with a "uv_spawn" error when Group Policy blocks PowerShell 5.1. The daemon now prefers PowerShell 7.
• Fixed Launch Failure of Host-Managed Sessions: Fixed a bug where host-managed sessions would fail at startup when repository settings configure mTLS certificates, additional CA bundles, or OAuth scopes (these settings are now ignored with a warning).
• Fixed Bugs Around @Mentions and Plugins: Fixed an issue where @mentions would attach nothing after a partial file read, an issue where plugin uninstallation would target the wrong marketplace, and an issue where exit code 143 would incorrectly show "Command timed out."
• Various other minor bugs have also been fixed, including issues with /ultrareview input and branch resolution, stop instructions for continue:false hooks, process tree handling on SIGTERM, OpenTelemetry/OTLP export, diff preview display, and shell mode execution.

Breaking Changes and Deprecations

• Deprecation of mode Parameter in Task Tool: The mode parameter of the Task tool has been deprecated and is currently ignored. Subagents now inherit the parent session's permission mode by default. If you were specifying mode in your SDK or tool definitions, the behavior may change, so it is recommended to verify.

Closing

v2.1.212 is a wide-ranging release that covers practical new features such as the revamped /fork, per-session limits to prevent runaway loops, and automatic backgrounding of MCP calls, as well as security fixes for plan mode and worktrees, and improvements to prompt caching via the cloud. In particular, those using plan mode, the SDK, or Enterprise environments should check the scope of impact. Why not update and give it a try?

References

https://github.com/anthropics/claude-code/blob/main/CHANGELOG.md

https://code.claude.com/docs/en/changelog