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Praxist

Cost Estimation

Praxist can spend tokens, task-selected compute time, wall-clock time, tool quota, and external API quota. Cost estimates are advisory, not a replacement for BudgetPolicy.

Inputs To Estimate

Estimate cost from:

  • cohort size;
  • number of generations;
  • model profile per stage;
  • expected peer session count;
  • expected Principal Investigator (PI) and Chair planning calls;
  • prompt size and cache stability;
  • tool calls;
  • evaluation runtime;
  • platform/backend capacity and queue behavior, including accelerator capacity only when the task actually uses one.

Prompt Cache Readiness

PromptLayout V1 keeps frozen and dynamic prompt blocks separate. Stable frozen prefixes improve the chance that caches managed by the agent runtime or API provider are useful.

Agent runtime cache behavior is currently treated as runtime-managed. Praxist records layout hashes and cache provenance rather than injecting raw cache directives where the runtime does not expose them.

Interpreting Usage

Exact token or cache usage depends on what the agent runtime/API provider returns. Missing metering should be recorded as unknown rather than zero.

Use run artifacts, budget ledgers, and API provider invoices together when analyzing cost after a dogfood run.

For runtimes that report cache usage, input_tokens is the inclusive logical input total and cached_input_tokens is the cache-read subset. Calculate:

uncached_input_tokens = input_tokens - cached_input_tokens - cache_creation_input_tokens
cache_hit_ratio = cached_input_tokens / input_tokens
sessions_per_peer_generation = peer session count / peer-generation count

Treat an unreported cache-creation value as zero. If the reported components do not fit inside inclusive input, keep the raw values and mark them inconsistent instead of forcing the equation to balance.

Claude SDK telemetry additionally preserves cache-creation input separately. Its API provider's native input_tokens value is uncached input, so the adapter normalizes inclusive input as uncached + cache read + cache creation. Historical or third-party records whose cached input exceeds their declared total are kept unchanged and marked telemetry_inconsistent; Praxist does not clamp them or publish a misleading cache-hit ratio.

Treat these as separate signals. Prompt caching can reduce billed compute while logical input remains high; reducing unnecessary fresh sessions reduces both repeated tool work and logical input. The read-only diagnostic inventory derives these values from canonical generation_results.json rows and the run summary; it does not create another usage ledger.

Session-reuse and tool-output mechanisms are defined in Cost Optimization; this page only defines how to estimate and interpret cost.