Billing & credits

Karta billing is prepaid. Model usage draws down a credit balance you top up in advance, so there are no metered invoices and no bill shock: an org can never owe Karta more than it has already paid. When the balance runs out, requests pause with 402 Payment Required until you top up.

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Plans

• Free includes a one-time $10 credit grant at signup - enough to deploy and run your first agents with no card and no key.
• Pro is the same managed experience with a lower platform fee: the same credit balance buys 25% more model usage than it does on Free.
• Pro BYOK runs on your own Anthropic or Bedrock account. You pay your provider directly for tokens; Karta charges only the flat fee, subject to a $1,000/month fair-use ceiling on estimated model cost (you’ll get a warning email at 80%, and a 402 at 100% - it resets each calendar month). Estimates gate usage; they are never billed.

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Credits

Credits are face dollars. Buy them in packs - $20,$50, or $100 - from the billing page. Pack prices include payment processing; receipts show one number. Usage draws the balance down at your plan’s rate: the per-token model cost below, times the platform-fee multiplier published in the plan table.

• Expiry - unused credits lapse 12 months after they were added. The billing page warns you 30 days out.
• Auto-refill (optional) - buy a chosen pack automatically when the balance drops below a threshold you set. A monthly cap is required when enabling it: it bounds the worst case for a runaway agent at your cap plus one pack. Failures never block buying manually.
• Out of credits - requests return 402 with reason credits_exhausted. Agents resume the moment the balance is positive again.

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Rate card

Model usage is priced per token. Rates track the model vendors’ published API pricing: Other models - anything not listed above (for example a brand-new model variant) is metered at the mid-tier (Sonnet) rate until a specific rate is published. On managed plans, the credit drawdown is the token cost times your plan’s multiplier (the platform fee in the table above). On BYOK, these rates are used only to estimate usage against the fair-use ceiling - your actual token bill comes from your own provider.

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The prepaid guarantee

• No code path can bill you past your collected balance. Usage can briefly overshoot by the in-flight turn (agents finish their current response); the overshoot is absorbed by Karta, never invoiced.
• Refunds and chargebacks are deducted from the credit balance; if it goes negative, usage pauses until a top-up - never a bill.
• The subscription fee (Pro and Pro BYOK) is the only recurring charge, and it’s flat.