{"name":"tengu_fennel_godwit","slug":"tengu-fennel-godwit","family":"flag","title":"Feature flags","noun":"feature flag","description":"On Opus 5, Claude is told not to spawn subagents, workflows or deep research unless you ask.","description_source":"entry","described_by":{"version":"2.1.219","anchor":"opus-5-gets-an-extra-system-prompt-instruction-restricting-a"},"presence":{"first_seen":"2.1.219","removed_in":null,"in_current_build":true,"newest_mined":"2.1.309","builds":61,"mined_builds":150,"first_cited":null},"aliases":[],"entries":[{"version":"2.1.219","anchor":"opus-5-gets-an-extra-system-prompt-instruction-restricting-a","heading":"Opus 5 gets an extra system-prompt instruction restricting AgentTool, workflows and deep-research","line":"On Opus 5, Claude is told not to spawn subagents, workflows or deep research unless you ask.","released_at":"2026-07-24 16:11:49","reason":"gate cited by this entry, found in this entry's text"}],"entries_total":1,"docs":[],"docs_total":0,"gates":[{"version":"2.1.219","state":"off","account":false,"baseline":false,"code_default":null}],"related":[{"name":"tengu_fennel_kite_model","slug":"tengu-fennel-kite-model","description":"Default `\"\"`. A model-ID substring: when the current model's ID contains it, and the base preconditions hold (the default Anthropic API base URL or `CLAUDE_CODE_MID_CONVERSATION_SYSTEM` set, plus other provider and model checks), requests send the `mid-conversation-system-2026-04-07` beta header and message building switches to its mid-conversation-system handling. A model ID matching `CLAUDE_CODE_MID_CONVERSATION_SYSTEM` is accepted first, and a non-empty cached client-data value of the same name is used in place of the flag."}],"url":"https:\/\/changelogs.core-directive.com\/reference\/flag\/tengu-fennel-godwit","family_url":"https:\/\/changelogs.core-directive.com\/reference\/flag.json"}