The claude-ai and anthropic-skills names are now reserved for skills synced from claude.ai

What

A skill is a packaged set of instructions that Claude Code can load. Some skills are synced to Claude Code from your claude.ai account. The names claude-ai and anthropic-skills are now reserved for those synced skills, and several related pieces arrive with that reservation:

• Local and plugin skills whose name uses a reserved name are no longer loaded.
• MCP servers whose name uses one are no longer loaded. MCP is a standard for connecting outside tools to Claude Code.
• A skill served by an MCP server is refused when its SKILL.md frontmatter name: uses a reserved name. The server's tools still load.
• A high-priority warning notification, reserved-skill-names, tells you to rename the file, edit its name: line or rename the workflow, and then restart.
• Prompts from MCP servers with a reserved name are no longer offered as slash commands. Each hidden prompt records an error for that server saying: "Rename the server in your MCP configuration to list its prompts."
• The reserved-name check arrives alongside a new gate, tengu_plaid_harbor. Nothing has been read about this gate yet.
• Synced skills now carry a class, syncedSkillClass. It comes from the sync manifest's skillClass or from a landed-ahead map, and falls back to "account". An account-class skill is named claude-ai:<name>. Attribution is now read from the manifest entry's attribution field, and the check for whether a local skill shadows a synced one takes the class into account.
• A session plugin named anthropic-skills, loaded inline from a marketplace from a path that is not an archive, is flagged accountSkillsWrapper, subject to a condition the members did not resolve. Its prompt commands get plugin information attached, as server plugins already did, and the load result reports which check failed.
• Skill and command names now match across the two prefixes: a claude-ai: name finds its anthropic-skills: twin and the reverse. This covers synced skills and anthropic-skills plugin skills.
• A synced skill whose display name changed gets a formerDisplayName, so its old name still finds it.
• The skillOverrides setting, which hides or collapses a skill, now looks up synced skills from syncedSkills under their alias names too, preferring claude-ai: names, and checks localSettings, projectSettings and userSettings in that order. Stale local keys are cleared when the effective state changes, and writes are skipped for synced skills whose state did not change.
• A new gate, tengu_copper_heron, has a built-in default of off. When it is on, it turns on syncedSkillOwnNamespace: synced skills get their own namespace, and launches of forked skills named with a claude-ai: or anthropic-skills: prefix are stamped anthropicNamespaceReserved. When that stamp is present, a synced skill whose class does not match its prefix is rejected (account for claude-ai, anthropic for anthropic-skills), and alias lookups are no longer used as a fallback. Nothing has been read about this gate yet.
• A new gate, tengu_jaunty_alpaca, has a built-in default of on. It marks a skill that loses a sync name collision as the loser instead of carrying it over, and that skill is then skipped. Nothing has been read about this gate yet.

Why

If you have a skill or an MCP server named claude-ai or anthropic-skills, or a name starting with claude-ai: or anthropic-skills:, it stops loading after this update, and the warning is the only sign. Rename it and restart to get it back. For synced skills, slash commands keep working when a skill is renamed or is reached through the other prefix.