Auto cost migration

The idea

Per cell, if a cheaper model's EMA quality is within epsilon of the current winner and has enough samples, migrate the cell. Report the projected monthly savings. If things go sideways, one click to roll back.

The migration is automatic; the quality gate is the only thing keeping a cell from moving to a worse model. That gate is tunable.

Safety rails

• Quality epsilon — default 0.05 on the 0..1 quality scale. A cheaper alternative must be within this of the current winner.
• Minimum samples — default 30 on the alternative before it's eligible.
• Grace boost — the newly-migrated model gets a temporary EMA boost so it doesn't immediately lose to its predecessor on the next judge event.
• Rollback — one click reverts the migration and clears the grace boost. Savings stop accruing immediately.
• Opt-in per tenant — default off; Pro+ tiers can enable.

What you see

• Reported savings on /dashboard/routing — "Migrated 3 cells last week — saved $X at equal quality"
• Migration history on GET /v1/cost-migrations
• Full per-migration detail: from model, to model, quality delta, estimated monthly savings

Tuning

# Opt in
curl -X POST https://gateway.provara.xyz/v1/cost-migrations/opt-in \
  -H "Authorization: Bearer <token>" \
  -d '{"enabled": true}'

# Trigger a cycle manually
curl -X POST https://gateway.provara.xyz/v1/cost-migrations/run \
  -H "Authorization: Bearer <token>"

Env vars PROVARA_COST_MIGRATION_EPSILON and PROVARA_COST_MIGRATION_MIN_SAMPLES override the defaults.