# Claude Code v2.1.48

> Claude Code v2.1.48, released 19 Feb 2026 (2026-02-19). 14 entries read out of the shipped bundle. Unofficial, and not affiliated with Anthropic.

Web version: https://changelogs.core-directive.com/v/2.1.48

This release introduces a major new worktree workflow for isolated development, adds HTTP hooks and a new ConfigChange hook event, and removes the experimental MCP-CLI feature. Users can now work in git worktrees with optional tmux integration, and exclude specific CLAUDE.md files using glob patterns.

## Changes

### Git Worktree Mode

**What**

Create and work in isolated git worktrees directly from Claude Code, with full session management and cleanup prompts.

**Usage**

`# Start Claude Code with a new worktree claude --worktree claude -w # Start with a named worktree claude --worktree=my-feature # Combine with tmux for parallel sessions claude --worktree --tmux` **Details** - Creates a new git worktree in `.claude/worktrees/` with a dedicated branch based on HEAD - Automatically switches the session's working directory to the worktree - On session exit, prompts to keep or remove the worktree and associated tmux session - Symlinks configured directories (like `node_modules`) from main repo to avoid disk bloat - Copies `settings.local.json` and configures git hooks from the main repository - The worktree branch is automatically deleted when removing the worktree **Evidence** New `-w, --worktree [name]` flag and CreateWorktree tool (search for `"Create a new git worktree for this session"`)

### CreateWorktree Tool

**What**

A new built-in tool that allows Claude to create worktrees mid-session when users request isolated work.

**Usage**

`User: "Start a worktree for this feature" User: "Work in isolation on a separate branch"` **Details** - Tool activates when user asks to "work in isolation" or "start a worktree" - Must be in a git repository and not already in a worktree - Creates worktree with optional custom name - Session automatically switches to the new worktree directory **Evidence** Tool description (search for `"Use this tool when the user asks to work in isolation"`)

### HTTP Hooks

**What**

A new hook type that sends HTTP POST requests instead of executing shell commands, enabling webhook-style integrations.

Usage (in settings.json or CLAUDE.md):

`{ "hooks": { "PreToolUse": [{ "type": "http", "url": "https://your-server.com/hook", "headers": { "Authorization": "Bearer $MY_TOKEN" }, "timeout": 30 }] } }` **Details** - Supports environment variable expansion in headers (`$VAR_NAME` or `${VAR_NAME}` syntax) - Configurable timeout per request - JSON response parsing with optional logging - Works with all hook events including the new ConfigChange event **Evidence** New http hook type definition (search for `"HTTP hook type"`)

### ConfigChange Hook Event

**What**

A new hook event that fires when configuration files change during a session, allowing validation and blocking of config changes.

**Details**

- Fires when skills, settings, or CLAUDE.md files are modified
- Can block changes by returning exit code 2
- Input includes source (user_settings, project_settings, etc.) and file_path
- Useful for enforcing configuration policies

**Evidence**

New ConfigChange hook event (search for `"ConfigChange"`)

### CLAUDE.md Exclude Patterns

**What**

Exclude specific CLAUDE.md files from loading using glob patterns or absolute paths.

Usage (in settings.json):

`{ "memory": { "excludePatterns": [ "/home/user/monorepo/CLAUDE.md", "**/node_modules/**/CLAUDE.md", "**/some-dir/.claude/rules/**" ] } }` **Details** - Uses picomatch for glob pattern matching - Patterns match against absolute file paths - Only applies to User, Project, and Local memory types (Managed/policy files cannot be excluded) **Evidence** New excludePatterns setting (search for `"Glob patterns or absolute paths of CLAUDE.md files to exclude from loading"`)

### Tmux Integration for Worktrees

**What**

Automatically create tmux sessions when starting worktrees, with iTerm2 native pane support.

**Usage**

`claude --worktree --tmux claude -w --tmux=classic # Use traditional tmux instead of iTerm2 integration` **Details** - Creates a tmux session for parallel worktree work - Uses iTerm2 native panes when available for better integration - Use `--tmux=classic` for traditional tmux behavior - Session management options on exit: keep both, keep worktree only, or remove all **Evidence** New --tmux flag (search for `"Create a tmux session for the worktree"`)

### Model Capability Descriptions

**What**

Added explicit descriptions for model thinking capabilities in the schema.

**Details**

- New `effortLevels` field describes available effort levels for models
- New `supportsAdaptiveThinking` field indicates whether a model supports adaptive thinking (Claude decides when and how much to think)

**Evidence**

New schema descriptions (search for `"Whether this model supports adaptive thinking"`)

### Git Diff for Issue Creation

**What**

Improved git diff generation when creating issues, with better handling of edge cases.

**Details**

- Handles shallow clones gracefully with HEAD-only mode
- Falls back to HEAD-only mode when no remote or merge-base is found
- Captures untracked files with size limits (500MB per file, 5GB total)
- Excludes binary files from untracked file capture
- Filters out excessively large files automatically

**Evidence**

New shallow clone detection (search for `"Shallow clone detected, using HEAD-only mode for issue"`)

### MCP Server Authentication Caching

**What**

Caches MCP servers that need authentication to reduce redundant connection attempts.

**Details**

- Stores needs-auth status in `mcp-needs-auth-cache.json`
- Skips connection attempts for cached servers
- Logged as "Skipping connection (cached needs-auth)"

**Evidence**

New cache file (search for `"mcp-needs-auth-cache.json"`)

### Background Agent UX Improvements

**What**

Better messaging for background agent management.

**Details**

- New "Press again to kill all background agents" message for confirmation
- Clearer output file instructions

**Evidence**

New UI text (search for `"Press again to kill all background agents"`)

### IDE Opening Feedback

**What**

Better feedback when opening worktrees or projects in IDEs.

**Details**

- Clearer messages for manual IDE opening
- Specific messaging for worktree vs project contexts

**Evidence**

New message handling (search for `"Please open the"`)

## Bug Fixes

- Fixed path traversal detection (search for `"path traversal detected"`)
- Added validation for non-empty strings and patterns (search for `"Expected a non-empty string"`)

### MCP-CLI Removed

**What**

The experimental `mcp-cli` command-line interface for MCP servers has been removed.

**Details**

- The `ENABLE_EXPERIMENTAL_MCP_CLI` environment variable is no longer recognized
- The `mcp-cli` command (info, call, servers, tools, grep, resources, read) is removed
- MCP tools continue to work through the normal tool interface

Impact: If you relied on `mcp-cli` commands in bash scripts or hooks, migrate to using MCP tools through Claude's standard tool interface.

**Evidence**

Removal of mcp-cli infrastructure (removed strings: `"mcp-cli info"`, `"mcp-cli call"`, `"ENABLE_EXPERIMENTAL_MCP_CLI"`)

## Notes

The worktree feature requires being in a git repository and having git installed. Tmux integration requires tmux to be installed (`sudo apt install tmux` on Linux). iTerm2 users will get native pane integration when using `--tmux` without the `=classic` suffix.