Usage & Billing

Overview

ReqLLM provides normalized usage tracking and best-effort cost calculation for API requests. Every response includes usage data that works consistently across providers, with detailed breakdowns for tokens, tools, and images when the provider exposes enough information.

Pricing Policy

ReqLLM currently targets "some assistance, no guarantees" for pricing.

In practice, that means:

• response.usage is intended to be useful for product analytics, tenant attribution, dashboards, and rough billing estimates
• token, tool, image, and caching costs are calculated from provider usage data plus model pricing metadata when those inputs exist
• the resulting USD totals are not guaranteed to match provider invoices exactly

When exact billing matters, treat ReqLLM usage as a helpful estimate and reconcile against provider-side reporting. For the full contract, known gaps, and production guidance, see the Pricing Policy guide.

The Usage Structure

Every ReqLLM.Response includes a usage map with normalized metrics:

{:ok, response} = ReqLLM.generate_text("anthropic:claude-haiku-4-5", "Hello")

response.usage
#=> %{
#     # Token counts
#     input_tokens: 8,
#     output_tokens: 12,
#     total_tokens: 20,
#
#     # Cost summary (USD)
#     pricing: %{status: :priced, currency: "USD", total: 0.0006},
#     input_cost: 0.00024,
#     output_cost: 0.00036,
#     total_cost: 0.0006,
#
#     # Detailed cost breakdown
#     cost: %{
#       tokens: 0.0006,
#       tools: 0.0,
#       images: 0.0,
#       total: 0.0006
#     }
#   }

Conditional tariffs and unknown pricing

Pass confirmed billing facts through pricing_context for conditional tariffs:

{:ok, response} = ReqLLM.generate_text("openai:gpt-6-sol", prompt,
  pricing_context: %{
    api: "responses",
    service_tier: "default",
    regional_processing: false
  }
)

response.usage.pricing
#=> %{status: :priced, currency: "USD", total: 0.012345}

The same option works with stream_text/3; read the final value with ReqLLM.StreamResponse.usage/1. The context is local billing input. ReqLLM derives the prompt size from returned usage, including cached prompt tokens, then uses LLMDB's component selector. It charges uncached input, cache reads, cache writes, output, and storage through separate meters. A selected context tier applies to the whole request when LLMDB marks it full_request.

For OpenAI, ReqLLM uses the physical endpoint and the returned service tier for both buffered and streamed prices. The returned tier replaces pricing_context.service_tier; a missing, invalid, or "auto" returned tier does not confirm a billed tier. Known OpenAI hosts confirm global or regional processing. Other hosts require an independently confirmed processing fact. Standalone compact and Decisions endpoints do not establish a Responses tariff.

For other providers, supply the actual billed service tier after any provider fallback. "auto" does not confirm one. Time-dependent tariffs require an explicit pricing_period: "peak" or "off_peak" chosen by the caller from provider billing evidence; ReqLLM does not choose a period from a clock or response timestamp. For a current Coding Plan credit tariff, also supply billing_product: "coding_plan" and plan_generation: "token_credits". Cache writes with mixed durations use reported cache_write_tokens_by_ttl: %{"5m" => count, "1h" => count} usage; if the durations cannot be reconciled with the total, pricing stays unknown. ReqLLM requires LLMDB 2026.10.2 or later for the reviewed Anthropic cache tariffs. This includes Haiku 5.5's separate five-minute and one-hour rates, its full-prompt threshold, and the Sonnet 5.5 one-hour rate.

When the tariff or usage is incomplete, usage.pricing is %{status: :unknown} and ReqLLM omits total_cost, input_cost, output_cost, reasoning_cost, and cost. This includes missing token counts, unresolved conditions, unsupported modifiers, incomplete bands, missing cache/storage rates, and unpriced gateway usage. A zero charge is reported only when a complete selected tariff and usage establish zero billable quantity. If a provider returns no usage payload at all, response.usage may remain nil; that also means the price is unknown. The legacy flat cost map remains a model metadata summary; it does not select a conditional period or supply a missing rate.

For non-USD tariffs, usage.pricing carries the denomination and amount. For example, Coding Plan returns currency: "credits" and never populates the USD *_cost fields. Existing clients reading total_cost continue to receive a number for complete USD flat tariffs. Clients should check usage.pricing.status before treating a missing total_cost as free usage.

Token Usage

Standard Tokens

All providers report basic token counts:

Reasoning Tokens

For reasoning models (OpenAI o1/o3/gpt-5, Anthropic extended thinking, Google thinking):

{:ok, response} = ReqLLM.generate_text("openai:o3-mini", prompt)

response.usage.reasoning_tokens
#=> 1250  # Tokens used for internal reasoning

The reasoning_tokens field tracks tokens used for chain-of-thought reasoning. These may be billed differently than standard tokens depending on the provider.

Cached Tokens

For providers that support prompt caching (Amazon Bedrock, Anthropic, OpenAI):

response.usage.cache_read_tokens
#=> 500  # Input tokens served from cache

response.usage.cache_write_tokens
#=> 0    # Tokens used to create new cache entries

Cache reads and writes have separate counters because providers can bill them at different rates. The cached_tokens and cache_creation_tokens fields remain as compatibility aliases. See Anthropic Prompt Caching for details.

Tool Usage

When using tools like web search, usage is tracked in tool_usage:

response.usage.tool_usage
#=> %{
#     web_search: %{count: 2, unit: "call"}
#   }

Web Search

Each provider has slightly different web search tracking:

Anthropic Example:

{:ok, response} = ReqLLM.generate_text(
  "anthropic:claude-sonnet-4-5",
  "What's happening in AI today?",
  provider_options: [web_search: %{max_uses: 5}]
)

response.usage.tool_usage.web_search
#=> %{count: 3, unit: "call"}

xAI Example:

{:ok, response} = ReqLLM.generate_text(
  "xai:grok-4-1-fast-reasoning",
  "Latest tech news",
  xai_tools: [%{type: "web_search"}]
)

response.usage.tool_usage.web_search
#=> %{count: 5, unit: "call"}

Google Grounding Example:

{:ok, response} = ReqLLM.generate_text(
  "google:gemini-3-flash-preview",
  "Current stock market trends",
  provider_options: [google_grounding: %{enable: true}]
)

response.usage.tool_usage.web_search
#=> %{count: 2, unit: "query"}

Image Usage

For image generation, usage is tracked in image_usage:

{:ok, response} = ReqLLM.generate_image("openai:gpt-image-1", prompt)

response.usage.image_usage
#=> %{
#     generated: %{count: 1, size_class: "1024x1024"}
#   }

Size Classes

Image costs vary by resolution:

Multiple Images

{:ok, response} = ReqLLM.generate_image("openai:dall-e-2", prompt, n: 3)

response.usage.image_usage.generated
#=> %{count: 3, size_class: "1024x1024"}

Cost Breakdown

The cost map provides a detailed breakdown by category:

response.usage.cost
#=> %{
#     tokens: 0.001,    # Token-based costs (input + output)
#     tools: 0.02,      # Web search and tool costs
#     images: 0.04,     # Image generation costs
#     total: 0.061,     # Sum of all costs
#     line_items: [...]  # Per-component details
#   }

Line Items

For detailed billing analysis, line_items provides per-component costs:

response.usage.cost.line_items
#=> [
#     %{component: "token.input", cost: 0.0003, quantity: 100},
#     %{component: "token.output", cost: 0.0007, quantity: 50},
#     %{component: "tool.web_search", cost: 0.02, quantity: 2}
#   ]

Provider-Specific Notes

Anthropic

• Web search: $10 per 1,000 searches
• Prompt caching: Reduced rates for cached tokens
• Extended thinking: Reasoning tokens tracked separately

OpenAI

• Responses API: Web search available for o1, o3, gpt-5 models
• Chat Completions API: No built-in web search
• Image generation: Costs vary by model and size

xAI

• Web search: Via xai_tools option
• Deprecated: live_search is no longer supported
• Units: May report as "call" or "source"

Google

• Grounding: Search via google_grounding option
• Units: Reports as "query"
• Image generation: Gemini image models supported

Known Limits

ReqLLM does not currently guarantee support for every provider billing surface. In particular:

• realtime audio/text billing is not modeled yet
• video generation billing is not modeled yet
• account-specific discounts, taxes, and prices beyond an explicitly modeled tariff are outside the public contract

Telemetry

ReqLLM now emits three telemetry families:

• [:req_llm, :request, :start | :stop | :exception] for lifecycle timing, request and response summaries, usage, and standardized reasoning metadata

• [:req_llm, :reasoning, :start | :update | :stop] for provider-neutral thinking and reasoning milestones

• [:req_llm, :token_usage] for backwards-compatible token and cost tracking

For billing and tenant attribution, use [:req_llm, :request, :stop] as the source of truth. It includes duration in measurements plus request_id, usage, finish_reason, and normalized reasoning metadata in the event metadata. The token usage event remains useful if you only want token and cost totals.

When you audit reasoning-heavy workloads, prefer the normalized reasoning snapshot on the request lifecycle events over raw provider payloads. It captures both the originally requested reasoning settings and the effective translated request, so you can see when a provider rewrites or disables a reasoning configuration before you attribute cost or behavior to a tenant.

:telemetry.attach_many(
  "my-req-llm-billing",
  [
    [:req_llm, :request, :stop],
    [:req_llm, :request, :exception],
    [:req_llm, :token_usage]
  ],
  fn event, measurements, metadata, _config ->
    case event do
      [:req_llm, :request, :stop] ->
        duration_ms = System.convert_time_unit(measurements.duration, :native, :millisecond)

        IO.inspect(
          %{
            request_id: metadata.request_id,
            duration_ms: duration_ms,
            finish_reason: metadata.finish_reason,
            usage: metadata.usage,
            reasoning: metadata.reasoning
          },
          label: "Request"
        )

      [:req_llm, :request, :exception] ->
        IO.inspect(metadata, label: "Failed request")

      [:req_llm, :token_usage] ->
        IO.inspect(%{measurements: measurements, metadata: metadata}, label: "Usage")
    end
  end,
  nil
)

[:req_llm, :token_usage] remains available on every request, including streaming:

:telemetry.attach(
  "my-usage-handler",
  [:req_llm, :token_usage],
  fn _event, measurements, metadata, _config ->
    IO.inspect(measurements, label: "Usage")
    IO.inspect(metadata, label: "Metadata")
  end,
  nil
)

Event measurements include:

• tokens — the normalized token map, including input, output, total_tokens, and reasoning when available
• cost — total USD cost or nil
• input_cost, output_cost, reasoning_cost, and total_cost when model pricing is available

See the Telemetry Guide for the full event contract, reasoning lifecycle, milestone semantics, and payload capture options.

Example: Complete Usage Tracking

defmodule UsageTracker do
  def track_request(model, prompt, opts \\ []) do
    {duration_us, result} = :timer.tc(fn ->
      ReqLLM.generate_text(model, prompt, opts)
    end)

    case result do
      {:ok, response} ->
        usage = response.usage

        IO.puts("""
        Request completed in #{duration_us / 1000}ms

        Tokens:
          Input: #{usage.input_tokens}
          Output: #{usage.output_tokens}
          Total: #{usage.total_tokens}
          #{if usage.reasoning_tokens, do: "Reasoning: #{usage.reasoning_tokens}", else: ""}

        Cost:
          Input: $#{format_cost(usage.input_cost)}
          Output: $#{format_cost(usage.output_cost)}
          Total: $#{format_cost(usage.total_cost)}

        #{format_tool_usage(usage.tool_usage)}
        #{format_image_usage(usage.image_usage)}
        """)

        {:ok, response}

      error ->
        error
    end
  end

  defp format_cost(nil), do: "n/a"
  defp format_cost(cost), do: :erlang.float_to_binary(cost, decimals: 6)

  defp format_tool_usage(nil), do: ""
  defp format_tool_usage(tool_usage) do
    Enum.map_join(tool_usage, "\n", fn {tool, %{count: count, unit: unit}} ->
      "Tool Usage: #{tool} = #{count} #{unit}(s)"
    end)
  end

  defp format_image_usage(nil), do: ""
  defp format_image_usage(%{generated: %{count: count, size_class: size}}) do
    "Image Usage: #{count} image(s) at #{size}"
  end
  defp format_image_usage(_), do: ""
end

See Also

• Data Structures - Response structure details
• Anthropic Guide - Web search and prompt caching
• OpenAI Guide - Responses API and image generation
• xAI Guide - Grok web search
• Google Guide - Grounding and search
• Image Generation Guide - Image costs

Billing validation suite

ExUnit owns billing assertions. The req_llm.billing Mix task selects cases, records provider evidence, and exports independent calculation worksheets. Normal tests and check are offline. Live recording requires explicit limits. After a successful live run, record runs an offline ExUnit audit of its saved capture. This second check makes no provider calls.

mix test --only billing
mix req_llm.billing list
mix req_llm.billing check
mix req_llm.billing check --case mixed_cache_ttl --layer pricing
mix req_llm.billing record --model openai:gpt-6-luna --case basic_usage --budget-usd 0.50 --max-requests 2
mix req_llm.billing audit --run tmp/billing/RUN
mix req_llm.billing promote --run tmp/billing/RUN --case basic_usage

The suite has capture, normalization, pricing, pipeline, and adversarial layers. Stable case IDs include basic_usage, cache_5m, cache_1h, mixed_cache_ttl, client_function, hosted_web_search, returned_service_tier, long_context, compact_unknown, and websocket_usage. list shows provider and phase support. For recording and audit, use --mode buffered, streamed, or both; compact is buffered only and the native session case is streamed only. The first rate book supports selected OpenAI and Anthropic models and the OpenRouter GPT-4.1 Mini gateway case.

A live run writes a new directory under tmp/billing/. It retains failed attempts and disables credential fallback and automatic retries. The USD limit controls admission using conservative estimates; it is not a supplier invoice limit. Each actual model call has its own attempt ID. Confirmed usage can reconcile its reservation. Failed calls retain their reservation.

The raw representation is provider-shaped JSON before ReqLLM response and usage normalization. JSON serialization can change whitespace or key order. Stream source bytes remain available as base64 chunks. Credentials are redacted. Legacy captures without a date remain legacy; export time does not prove a new provider call. Native session observations are labeled native_session_replay because the public session API returns provider events rather than a priced ReqLLM.Response.

Reference calculations read provider counters and reviewed decimal rates from test/support/billing/rates/book.json. They do not use the production billing engine or the LLMDB rate selector as their expected-result calculator. Worksheets retain unrounded amounts and fractions as well as six-decimal totals. For example, an output charge of 39 * 0.50 / 1_000_000 is exactly 0.0000195 USD. ReqLLM uses float arithmetic, so the check reports and permits at most one microdollar of rounding difference per active line when quantities and effective rates agree. A larger difference, wrong quantity, wrong rate, or false known price fails. Equivalent per-call and per-thousand rates are compared by units.

Review rate sources and routing before recording. OpenAI context-band tests use the supplier's returned input count. Separate live calls can have different outputs and cache states. Exact mode agreement uses the same source data in replay. Mixed Anthropic cache entries put the one-hour prefix first and repeat each cold prefix for a warm check. A zero cache hit does not pass a warm case. One-hour and mixed cache recording requires a duration-specific one-hour catalog rule. A generic five-minute write rate is not sufficient. ReqLLM requires LLMDB 2026.10.2 or later, which includes the Haiku 5.5 duration rules and its full-prompt context band, plus the reviewed Anthropic model tariffs. The saved Haiku 5.5 calls originally failed against LLMDB 2026.10.1. Their recorded price and failed result remain unchanged. Small response extracts replay those calls against the independent reference in CI; they are not promoted live baselines.

Recording never overwrites committed fixtures. Inspect the raw and calculation records, run audit, and then explicitly promote selected cases. Promotion rejects incomplete or synthetic source captures and existing targets. Selected transcripts and their independent rate/calculation sidecars become default CI baselines. Each sidecar stores one calculation, one model's frozen rates, the source hash, and the code/catalog identity. CI checks the source hash and the frozen calculation before comparing current ReqLLM pricing. The full capture directory remains outside Git. Large context-band request bodies can remain as local evidence instead of enlarging the fixture repository.