Implementation Planning

Plans that a different (or weaker) model could execute without re-deriving your reasoning, with success criteria fixed before any result is seen.

Model handoff

Use the strongest available model for problem framing, macro architecture, irreversible decisions, and plan approval. In Codex this is Sol; in Claude it is Fable when available, otherwise Opus. After the architecture is approved, a bounded phase planner may expand it on the intermediate tier (Codex Terra; Claude Sonnet when no design choice remains). Write the resulting brief so a clear-task worker (Codex Luna or Claude Sonnet) can implement it without reconstructing design intent. See agent-fanout for the full routing and escalation policy.

Pick the register (by stakes, not size)