{"name":"tengu_vellum_lantern","slug":"tengu-vellum-lantern","family":"flag","title":"Feature flags","noun":"feature flag","description":"Default `false`. Turns on the alternate prompt mode that `CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT` controls, for eligible models (`claude-opus-4-7`, model IDs ending in `-eap`, or models listed in the `simple_system_prompt` client data or the `tengu_velvet_cascade` flag). `-eap` and listed models get the mode whether or not this flag is on, and a truthy or explicitly falsy `CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT` overrides both.","description_source":"code","described_by":{"bundle":"2.1.153","author":"claude-opus-5-5"},"presence":{"first_seen":"2.1.138","removed_in":"2.1.154","in_current_build":false,"newest_mined":"2.1.308","builds":15,"mined_builds":149,"first_cited":{"version":"2.1.120","released_at":"2026-04-24 23:02:49","spans":1}},"aliases":[],"entries":[{"version":"2.1.120","anchor":"lean-prompt-mode-condensed-tool-descriptions","heading":"Lean Prompt Mode (Condensed Tool Descriptions)","line":null,"released_at":"2026-04-24 23:02:49","reason":"gate cited by this entry, found in this entry's text"},{"version":"2.1.120","anchor":"lean-prompt-system-gradual-rollout","heading":"Lean Prompt System [Gradual Rollout]","line":null,"released_at":"2026-04-24 23:02:49","reason":"gate cited by this entry, found in this entry's text"}],"entries_total":2,"docs":[],"docs_total":0,"gates":[{"version":"2.1.120","state":"off","account":false,"baseline":false,"code_default":null}],"related":[{"name":"tengu_vellum_anchor","slug":"tengu-vellum-anchor","description":"The out-of-credits message can add a \"progress saved\" note, off unless a server enables it."},{"name":"tengu_vellum_ash","slug":"tengu-vellum-ash","description":"Default `[]`. A list of model name fragments: when the current main model's name contains any non-empty entry, `TodoWrite` and the task tools (`TaskCreate`, `TaskGet`, `TaskUpdate`, `TaskList`) are disabled and the todo and task reminder messages are not added. A non-array or empty value changes nothing."},{"name":"tengu_vellum_siding","slug":"tengu-vellum-siding","description":"When the product-feedback policy changes, Claude Code now re-sends every feature switch to the VS Code extension, not just two of them"}],"url":"https:\/\/changelogs.core-directive.com\/reference\/flag\/tengu-vellum-lantern","family_url":"https:\/\/changelogs.core-directive.com\/reference\/flag.json"}