fableplan

Plan with Fable 5, execute with Sonnet — an opusplan-style dual-model setup for Claude Code.

Claude Code ships with a built-in opusplan model setting: "Opus in plan mode, Sonnet otherwise". There is no Fable equivalent in the model picker — the model list is hardcoded in the CLI. This plugin recreates it with a small trick: opusplan resolves its plan-mode model through the ANTHROPIC_DEFAULT_OPUS_MODEL environment variable, so pointing that variable at Fable 5 gives you Fable 5 in plan mode, Sonnet for execution.

Install

/plugin marketplace add bapttiste73/fableplan
/plugin install fableplan@fableplan

Usage

Command	Effect
/fableplan	Enable: plan with claude-fable-5, execute with Sonnet
/fableplan 1m	Same, with the 1M-context Fable variant (claude-fable-5[1m])
/fableplan off	Revert to your previous model configuration

Restart your Claude Code session after toggling — the model setting is read at startup.

How it works

The skill merges two keys into your global ~/.claude/settings.json (everything else is preserved):

{
  "model": "opusplan",
  "env": {
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-fable-5"
  }
}

That's it. You can also apply this by hand without installing anything.

Caveats

• The UI will display "Opus Plan Mode" — the label is cosmetic; plan mode actually runs Fable 5.
• ANTHROPIC_DEFAULT_OPUS_MODEL is an undocumented override and could change in a future CLI release.
• Fable 5 is not available on every plan/account. If requests fail, run /fableplan off.
• While enabled, anything else that resolves the "opus" alias (e.g. fast mode) also points to Fable.

License

MIT