Cost & pricing observability

GNL writes model calls' usage info (input/output/cached tokens) to the journal. getRunCost scans this journal POST-HOC to produce an exact, deterministic per-run cost — not a live/estimated "cost guard", but a literal sum of what actually happened. Use it when you need to answer "how much did this conversation cost me, how much did each model consume" after a run finishes, when generating a billing/usage report, or when feeding an OTel-compatible observability chain (trace exporter).

No separate sub-package is needed; it comes from the @gnldev/durable root export.

import { getRunCost, toTraceSpans } from '@gnldev/durable';

getRunCost takes a JournalReader and a runId; it sums the usage of all model entries in the run and computes cost from the pricing table (default DEFAULT_PRICING):

const cost = await getRunCost(reader, runId);
// { runId, inputTokens, outputTokens, cachedTokens, totalTokens,
//   modelCalls, toolCalls, costUsd, byModel: { 'claude-sonnet-5': { calls, tokens, costUsd }, ... } }

If you want to pass your own pricing table, you can override it with opts.pricing; if the journal has no model id (e.g. a mock model), assign a default with opts.modelId:

const cost = await getRunCost(reader, runId, { modelId: 'claude-sonnet-5' });

To feed an OTel exporter or for a waterfall visualization, convert the journal to a gen_ai.* semantic-compatible span list:

const spans = await toTraceSpans(reader, runId);
// [{ name: 'llm.generate' | 'tool.execute', kind: 'model' | 'tool', runId, seq, attributes }, ...]

If you want to update the pricing table without a deploy, you can read the __pricing__ document from the journal to get the effective table (falls back to DEFAULT_PRICING if there's no record in the journal):

import { effectivePricingTable } from '@gnldev/durable';
const table = await effectivePricingTable(journal); // __pricing__ (varsa) > DEFAULT_PRICING

Studio serves the same computation over REST — you don't need to re-implement it in your own backend:

GET /runs/:id/cost   → getRunCost(reader, id)
GET /runs/:id/trace  → journal'dan waterfall span'leri (maliyet dahil)