giant/config.py:migrate_config (config.toml) and
giant/model/network.py:_migrate_legacy_model_config (checkpoint model_config)
independently hand-maintained the same v0.2 facts and an identical router
expert-sizing rejection. Extract the shared knowledge into a new leaf module,
giant/_migration.py (V02_MODEL_KEY_TO_STAGES, V02_FIXED_FACTS,
reject_legacy_router_expert_sizing), consumed by both.
Also replace NSecConfig's legacy-only, nullable legacy_owner sentinel (living
in an extra: dict catch-all) with a normal, always-set owner: str = "stage2"
field, so build_models reads one concrete two-valued key instead of branching
on a legacy marker.
Record in CLAUDE.md that v0.2 checkpoint-loading support has no expiry
decided yet, since /ceph still holds pre-v0.3.0 checkpoints.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
lars
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