diff --git a/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/artifacts/.gitkeep b/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/artifacts/.gitkeep
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diff --git a/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/item.md b/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/item.md
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+---
+id: '20260608-103842-remove-legacy-ticket-schema-fields'
+slug: 'remove-legacy-ticket-schema-fields'
+title: 'Remove legacy Ticket schema fields and intake compatibility'
+status: 'open'
+kind: 'task'
+priority: 'P1'
+labels: ['ticket', 'schema', 'migration', 'cleanup']
+workflow_state: 'planning'
+created_at: '2026-06-08T10:38:42Z'
+updated_at: '2026-06-08T10:38:42Z'
+assignee: null
+legacy_ticket: null
+---
+
+## Background
+
+The local Ticket records have been migrated away from legacy `workflow_state: intake` and legacy `preflight` vocabulary. Current open Tickets use explicit `workflow_state: planning`, and open Ticket `item.md` records no longer rely on `needs_preflight`.
+
+Two legacy frontmatter fields/compatibility paths remain in the code/schema:
+
+- `legacy_ticket`: currently a required frontmatter field, but it has no behavioral effect beyond being parsed, stored, and displayed. It is usually `null` and does not validate or resolve any reference.
+- `needs_preflight`: legacy compatibility metadata from the removed preflight concept. It should no longer be authored or exposed as current Ticket state.
+
+The parser also still accepts `workflow_state: intake` as a compatibility alias for `planning`. After local migration, this compatibility should be removed rather than preserved as a permanent runtime surface.
+
+## Goal
+
+Remove obsolete Ticket schema compatibility: delete `legacy_ticket` and `needs_preflight` from the current Ticket schema/tool/API, and reject `workflow_state: intake` instead of normalizing it to `planning`.
+
+## Requirements
+
+- Remove `legacy_ticket` from current Ticket frontmatter requirements.
+  - New Tickets should not write `legacy_ticket`.
+  - `ticket doctor` should not require `legacy_ticket`.
+  - `TicketCreate` / tool input should no longer expose `legacy_ticket` unless a deliberate migration-only path is kept separately.
+  - `TicketShow` / list output should not expose it as a current field.
+  - Existing local records should be migrated to remove the field before or as part of this change.
+- Remove `needs_preflight` from current Ticket schema and tool/API output.
+  - New Tickets should not write it.
+  - Parser should not treat it as a current known field.
+  - `TicketShow` / `TicketList` should not show `needs_preflight` as current metadata.
+  - Any remaining historical mentions in `thread.md` stay audit history only.
+- Remove `workflow_state: intake` compatibility.
+  - `TicketWorkflowState::parse` or equivalent parser should reject `intake`.
+  - Missing `workflow_state` compatibility should be reconsidered; if retained temporarily, it should default to `planning` only as a bounded migration fallback, not reintroduce `intake` vocabulary.
+  - Tests should cover that `intake` is invalid.
+- Update tests, fixtures, prompts, docs, and Ticket examples that still include:
+  - `legacy_ticket` as required frontmatter;
+  - `needs_preflight` as a Ticket field;
+  - `workflow_state: intake` as accepted/current state.
+- Update local Ticket records under `.yoi/tickets` so current `item.md` files pass the stricter schema.
+- Keep historical `thread.md` text intact unless a test fixture requires explicit migration; old thread mentions are audit history, not schema input.
+
+## Non-goals
+
+- Adding typed Ticket relation metadata; that is covered by `typed-ticket-relation-metadata`.
+- Reintroducing a generic external issue link field. If needed later, it should be designed as a typed relation/external reference feature, not as the current inert `legacy_ticket` stub.
+- Rewriting all closed historical thread prose.
+
+## Acceptance criteria
+
+- New Ticket frontmatter omits `legacy_ticket` and `needs_preflight`.
+- `ticket doctor` passes without requiring `legacy_ticket`.
+- `TicketCreate`, `TicketShow`, and `TicketList` no longer expose `legacy_ticket` or `needs_preflight` as current fields.
+- `workflow_state: intake` is rejected by parser/doctor/tests.
+- Existing current Ticket records are migrated to the stricter schema.
+- Tests covering legacy `needs_preflight` / `legacy_ticket` required frontmatter are removed or rewritten.
+- Focused tests, `target/debug/yoi ticket doctor`, `cargo fmt --check`, and `git diff --check` pass.
diff --git a/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/thread.md b/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/thread.md
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+++ b/.yoi/tickets/open/20260608-103842-remove-legacy-ticket-schema-fields/thread.md
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+<!-- event: create author: LocalTicketBackend at: 2026-06-08T10:38:42Z -->
+
+## 作成
+
+LocalTicketBackend によって作成されました。
+
+---