Task tools (TaskCreate/TaskUpdate/TaskList/TaskGet) silently absent with Fable 5 model

Environment

• Claude Code v2.1.217, macOS (darwin 25.5.0), interactive TTY session (not VSCode, not headless)
• Model: fable (Fable 5), set via /model fable and settings "model": "fable"

Bug

The task-tracking tools (TaskCreate, TaskUpdate, TaskGet, TaskList — the built-in todo list) are silently absent from the session toolset when the model is fable. No error, no notice — the tools are simply not loaded and tool search finds no todo/task tool.

Repro

1. Interactive session with model haiku (or default): task tools present, TaskCreate works.
2. Switch /model fable (or start a session with fable as saved default).
3. Task tools disappear from the available toolset immediately; sessions started under fable never have them.

Observed live: TaskCreate succeeded, then /model fable was run, and the Task tools dropped from the toolset within the same session.

Expected

Docs (tools reference, agent-sdk/todo-tracking) list no model restriction on Task tools — only EndConversation is documented as model-gated. Expected: task tools available under Fable 5, or an explicit documented restriction + user-visible notice.

Notes

• Not the VSCode isTTY case (#23874) — this is a plain terminal TTY session.
• Not headless (#20463) — interactive session.
• Pattern resembles #67306 (Fable 5 advisor silently disabled) — fable silently losing tools with no surfaced message.