The plan catalogue describes what we sell today; a customer who signed up last
year bought last year's terms. Every commercially relevant condition — price,
quotas, seats, the hardware behind the plan — is now frozen onto a subscription
at signup, and the model refuses to let any of it be rewritten afterwards. A
price rise applies to new subscriptions and cannot reach back into an existing
contract.
PlanChange holds the two rules, computed against the frozen price rather than
today's catalogue:
- Upgrading is immediate and pro rata: the new plan for the days left in the
paid term, minus what the old plan was worth over those same days. On the
last day of a month that is one day's difference, not a month's.
- Downgrading waits for the end of the term. A yearly customer bought a year
and can move down when it is up; a month is a month. A mid-term downgrade is
a goodwill decision, not a self-service button, and its credit covers only
the unused part of the difference.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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