LLM Cost Tracker

LLM spend tracking and budgets for Rails: by user, feature, or any tag, in your own database, no proxy.

No prompts, no traces, no replay. Spend attribution only.

Requires Ruby 3.3+, Rails 8.0+, PostgreSQL or MySQL. Built for a Rails monolith, not multiple services.

Shown with RubyLLM; the flow is identical for the official OpenAI and Anthropic SDKs: swap the gem and the instrument name (see the cookbook).

# Gemfile
gem "llm_cost_tracker"
gem "ruby_llm"

bin/rails llm_cost_tracker:setup

Runs the install generator, writes a local price file, migrates the database, and verifies via llm_cost_tracker:doctor. Then enable the integration in the generated config/initializers/llm_cost_tracker.rb:

LlmCostTracker.configure do |config|
  config.tags.default = -> { { environment: Rails.env } }
  config.instrument :ruby_llm
end

Your RubyLLM calls stay unchanged, and every chat, embedding, transcription, image, and moderation call now lands in the ledger. Tag them to attribute spend:

LlmCostTracker.with_tags(user_id: Current.user&.id, feature: "chat") do
  RubyLLM.chat.ask("Hello")
end

Mount the dashboard in config/routes.rb. The engine ships without authentication, so put it behind yours:

authenticate :admin do
  mount LlmCostTracker::Engine => "/llm-costs"
end

• Calls. Provider, model, total tokens, total cost, latency, status.
• Line items. Per-component breakdown: text/audio/cached tokens, tool charges (web search, grounding, container sessions).
• Tags. Whatever attribution you pass: user, feature, tenant, env.
• Provider IDs. Response, plus project, API key and workspace when you pass them to track or track_stream, for downstream audits.
• Pricing snapshot. So historical numbers don't drift when prices change.

Daily, monthly, and per-call limits, plus per-tag limits such as one monthly budget per tenant_id, or a lifetime cap in dollars or calls per agent run (run_id, which RubyLLM.workflow sets on its calls). A crossed limit calls your on_exceeded hook, raises, or blocks the next call before it is sent. See Budgets.

Streams are recorded from the provider's final usage; see Streaming.

Captured does not always mean priced:

Add missing prices to config.pricing.file or config.pricing.overrides (Pricing), then run bin/rails llm_cost_tracker:backfill_unknown_pricing to price the calls already recorded. bin/rails llm_cost_tracker:prices:refresh runs it after writing a new config.pricing.file if the database is reachable.

For batch jobs, internal gateways, or anything without an SDK or Faraday hook:

LlmCostTracker.track(
  provider: :anthropic,
  model: "claude-sonnet-4-6",
  tokens: { input_tokens: 1500, output_tokens: 320 },
  tags: { feature: "summarizer", user_id: current_user.id }
)

• Configuration
• Pricing
• Budgets
• Data model
• Querying
• Dashboard
• Streaming
• Cookbook
• Extending
• Operations
• Architecture
• EU AI Act record-keeping
• Upgrading
• Changelog

bundle install
bin/check

MIT. See LICENSE.txt.