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Guide for updating model pricing in Splitrail. Use when adding new AI model costs or updating existing pricing data.

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Pricing Model Updates

Token pricing is defined in src/models.rs. Built-in models are populated by populate_defaults() into the runtime model registry, and user/config models can be merged with init_external_models().

Adding a New Model

  1. Add a ModelInfo entry in populate_defaults() with:
    • pricing: Use PricingStructure::Flat { input_per_1m, output_per_1m } for flat-rate models, or PricingStructure::Tiered for threshold-based pricing.
    • caching: Use the appropriate CachingSupport variant (None, OpenAI, Anthropic, OpenAIWithWrites, or Tiered).
    • service_tiers: Leave empty unless the provider has distinct priority/flex/batch rates.
    • dated_pricing: Leave empty unless pricing changes by usage date.
    • is_estimated: Set to true only when pricing is not confirmed by a provider/tool source.
    • input_token_semantics: Auto-derived for built-in models (defaults to ExcludesCache); only GPT/o-series models typically need IncludesCacheRead. External model configs should set this explicitly if it affects cache-read counting.
  2. If the model has aliases (date suffixes, provider-prefixed names, regional names, etc.), add entries to the alias section mapping each observed name to the canonical model name.
  3. Add or update tests in src/models.rs for canonical pricing, aliases, caching, and estimated/non-estimated status.

Dated Pricing Overrides

Use dated_pricing when a model has temporary promotional pricing, launch pricing, or another time-bounded rate that should apply based on the original usage timestamp.

The default pricing and caching fields should represent the durable/current sticker price. Each DatedPricing override has a valid_until: NaiveDate exclusive end date and applies when usage_date < valid_until. For example, an introductory rate that applies through 2026-08-31 should use valid_until = NaiveDate::from_ymd_opt(2026, 9, 1).expect("valid date").

When adding a dated override:

  • Keep the model's default pricing/caching at the post-promo or durable rate.
  • Add the temporary rate with add_dated_pricing!() after add_model!().
  • Add boundary tests for the final day of the temporary rate and the first day after it ends.
  • Prefer dated calculator functions in analyzers that know the usage timestamp.

Price Calculation

Use models::calculate_total_cost_for_service_tier_at() when an analyzer has a message or event timestamp. This preserves historical costs across dated pricing windows.

Use the undated compatibility helpers, such as models::calculate_total_cost(), only for tests, config-like calculations, or call sites that truly do not know the usage date. Undated helpers use the model's default pricing/caching, not temporary dated overrides.

Common Pricing Sources