Claude Code 2.1.63 adds bundled slash commands, HTTP hooks, and memory leak fixes

What's new in Claude Code 2.1.63

Anthropic has released Claude Code 2.1.63 with significant updates focused on new features, memory management improvements, and bug fixes. The release includes 26 CLI changes and 6 flag changes.

Key features and changes

• New bundled slash commands: Added /simplify and /batch commands
• Project configuration sharing: Project configs and auto memory are now shared across git worktrees in the same repository
• HTTP hooks: Hooks can now POST JSON to a URL and receive JSON responses instead of running shell commands
• Environment variable: Added ENABLE_CLAUDEAI_MCP_SERVERS=false to opt out from making claude.ai MCP servers available
• Improved /model command: Shows the currently active model in the slash command menu
• Manual URL paste fallback: During MCP OAuth authentication, if automatic localhost redirect fails, you can paste the callback URL manually
• VSCode improvements: Fixed remote sessions not appearing in conversation history; added session rename and remove actions to sessions list
• Copy option: Added "Always copy full response" option to the /copy picker - when selected, future /copy commands skip the code block picker and copy the full response directly

Memory leak fixes

Multiple memory leak issues have been addressed:

• Fixed listener leak in bridge polling loop
• Fixed listener leak in MCP OAuth flow cleanup
• Fixed memory leak when navigating hooks configuration menu
• Fixed listener leak in interactive permission handler during auto-approvals
• Fixed MCP tool/resource cache leak on server reconnect
• Fixed WebSocket listener leak on transport reconnect
• Fixed memory leak in git root detection cache that could cause unbounded growth in long-running sessions
• Fixed memory leak in JSON parsing cache that grew unbounded over long sessions
• Fixed memory leak where long-running teammates retained all messages in AppState even after conversation compaction
• Fixed memory leak where MCP server fetch caches were not cleared on disconnect

Other fixes and improvements

• Fixed local slash command output like /cost appearing as user-sent messages instead of system messages in the UI
• Fixed file count cache ignoring glob ignore patterns
• Fixed memory leak in bash command prefix cache
• Fixed IDE host IP detection cache incorrectly sharing results across ports
• Fixed a race condition in the REPL bridge where new messages could arrive interleaved with historical messages during initial connection flush
• Improved memory usage in long sessions with subagents by stripping heavy progress message payloads during context compaction
• Fixed /clear not resetting cached skills, which could cause stale skill content to persist in new conversations

Surface changes

Added:

• Option: --sparse
• Environment variables: CLAUDE_CODE_PLUGIN_SEED_DIR, ENABLE_CLAUDEAI_MCP_SERVERS
• Config keys: account, action, allowedHttpHookUrls, appendSystemPrompt, available_output_styles, blocked_path, callback_id, decision_reason, dry_run, elicitation_id, fast_mode_state, hookCallbackIds, httpHookAllowedEnvVars, jsonSchema, key, max_thinking_tokens, mcp_server_name, models, pending_permission_requests, pid, promptSuggestions, prompt_response, request, requested_schema, response, sdkMcpServers, selected, server_name, servers, sparsePaths, systemPrompt, uR, user_message_id, variables

Removed:

• Config key: fR
• Model: opus-46-upgrade-nudge

System prompt updates

• Task tool replaced by Agent tool (Explore guidance updated)
• New user-invocable skill: simplify