Inferrail

Know what your AI work costs.
Without keeping what it said.

Inferrail is a gateway you run yourself that tracks token usage and estimated LLM cost by customer, workflow, or task for its supported OpenAI and Anthropic endpoints.

Try locally · How it works · Privacy · Integrations · MCP · Status · Docs

Open source under Apache-2.0. Developer preview: the features below are implemented and tested, but CLI flags, config shape, and receipt fields may still change before 1.0.

Privacy boundary

For each supported request, the gateway writes one receipt to a local file. This is a real receipt from the offline demo below.

Example receipt: synthetic demo data, abbreviated.

{
  "receipt_id": "ir_4090e812f2ba4d3680e7",
  "route": "default",
  "provider": "demo",
  "model": "demo-small",
  "status": "success",
  "prompt_tokens": 812,
  "completion_tokens": 143,
  "pricing": {
    "input_usd_per_million": "0.20",
    "output_usd_per_million": "0.80",
    "source": "DEMO — a made-up round number, not a real provider price",
    "verified_date": "2026-09-26"
  },
  "estimated_cost_usd": "0.000277",
  "attributes": {"customer": "acme", "workflow": "contract-review", "work_id": "work-contract-1"}
}

Omitted here: request_id, timestamp, total_latency_ms, retry_count. Full field list: receipts/schema.py.

What happens to your key and your content (self-hosted):

• Your gateway process reads the provider key from its own environment and sends requests to the provider you configure.
• It processes prompts and responses in memory to forward them. The provider still receives your request content, under its own policies.
• Receipts record usage, cost evidence, status, timing, and the attribution you supply. The receipt path does not copy message bodies.
• Attribution tags are stored exactly as sent. Use identifiers, and keep secrets and message content out of them.
• Local telemetry events are operational metadata. The optional usage beacon is separate and sends nothing unless you configure a collector endpoint (details).
• The hosted trial is a different boundary: if you add a real key there, the hosted process holds that key and handles your traffic.

Check it yourself: request handlers · execution engines (OpenAI, Anthropic) · provider adapters (OpenAI, Anthropic) · receipt builder · sinks (JSONL, SQLite) · canary tests (OpenAI, streaming and telemetry, Anthropic).

inferrail verify-payload-free prints the live receipt schema and checks that no field is named for message content. It is a schema check, not a security audit: it cannot inspect stored values, logs, or your provider.

Try it offline

Requires Python 3.11+. Installing downloads the package and its dependencies; after that, the demo runs offline.

python -m pip install inferrail
inferrail demo
inferrail report --by customer --receipts ./inferrail-demo-receipts.jsonl

The demo needs no API key, makes no network calls, and creates no provider charges. It sends six scripted requests through the real engine with a fake provider and made-up prices labeled DEMO, then writes ./inferrail-demo-receipts.jsonl in your current directory.

python3 -m venv .venv && source .venv/bin/activate   # Windows: .venv\Scripts\activate
python -m pip install inferrail

_{Real run of inferrail demo 0.4.3 with networking blocked. Synthetic data, not provider billing. Static image · captured output · how it was made}

In the report, acme shows one request with unknown cost: the demo's preview model has no price on file, so its receipt has "pricing": null and "estimated_cost_usd": null. The COST (USD) column adds up known costs only. It is not a complete bill when the unknown count is above zero.

Send a real request

This uses your own provider account, which bills you as usual. Run the gateway in one terminal, with the key set in that terminal, because the gateway is the process that calls the provider:

export OPENAI_API_KEY=...        # and/or ANTHROPIC_API_KEY=...
inferrail serve --quickstart

Then point your client at it from another terminal or your app:

from openai import OpenAI

client = OpenAI(base_url="http://127.0.0.1:8000/v1", api_key="not-needed")
client.chat.completions.create(
    model="gpt-4o-mini",
    messages=[{"role": "user", "content": "Say hello in five words."}],
    extra_headers={"X-Inferrail-Attribute-Customer": "acme"},
)

import anthropic

# No /v1 here: the Anthropic SDK adds /v1/messages itself.
client = anthropic.Anthropic(base_url="http://127.0.0.1:8000", api_key="not-needed")
client.messages.create(
    model="claude-haiku-4-5-20251001",
    max_tokens=256,
    messages=[{"role": "user", "content": "Say hello in five words."}],
)

The client's api_key is a placeholder; the gateway ignores it unless you set INFERRAIL_GATEWAY_TOKEN. Then run inferrail report --by customer in the gateway's directory. The gateway listens only on 127.0.0.1 by default. Set INFERRAIL_GATEWAY_TOKEN before exposing it anywhere else (SECURITY.md).

How it works

Each request is routed by model to a configured provider (routing), executed with retries, and measured. Cost is computed only when the provider reports usage and a verified price is on file; otherwise it stays null, never a guessed $0 (calculator). Architecture: docs/ARCHITECTURE.md. Diagram source: scripts/render_flow_svg.py.

Integrations

Supported today: POST /v1/chat/completions (OpenAI-compatible, with streaming and tool calls), POST /v1/messages (Anthropic-compatible, with streaming and tool use), and GET /health. Any client or framework that lets you set a base URL and sends those shapes can use the gateway. Attribution, work grouping, framework examples, and MCP setup are in docs/integrations.md.

Voice agents. Inferrail has no native voice support. A voice stack can route its text LLM stage through Inferrail if that stage accepts a custom OpenAI- or Anthropic-compatible base URL and sends a supported request shape. Only that stage's tokens and cost are recorded. Audio, speech-to-text, text-to-speech, the Realtime API, and full call cost are not covered, and no voice framework has been tested by this project (details).

MCP

Inferrail ships an MCP server with two read-only tools, so an agent can ask what its AI work cost. The tools read your local receipts file. They do not run inference, spend provider budget, change configuration, or write any file. Inferrail receipts store usage and cost metadata without persisting prompt or response bodies, so the tools have none to return. (The gateway itself still handles prompts and responses in memory while forwarding them to the provider; see Privacy boundary.)

There are no separate customer, workflow, or job tools. get_spend groups by whatever tags your requests carry, so grouping by customer, workflow, or work_id (a unit of tagged work, such as one job) only covers requests that were sent with that tag (attribution).

The server speaks stdio and is started by your MCP client:

uvx inferrail mcp        # or: pip install inferrail && inferrail mcp

Client config (Claude Desktop, Cursor, and other clients that use mcpServers; VS Code uses the same entry under servers):

{
  "mcpServers": {
    "inferrail": {
      "command": "uvx",
      "args": ["inferrail", "mcp"],
      "env": {
        "INFERRAIL_RECEIPTS_PATH": "/absolute/path/to/inferrail-receipts.jsonl"
      }
    }
  }
}

Claude Code: claude mcp add inferrail -e INFERRAIL_RECEIPTS_PATH=/absolute/path/to/inferrail-receipts.jsonl -- uvx inferrail mcp

Set INFERRAIL_RECEIPTS_PATH to your receipts file. Clients start the server from their own working directory, so the default ./inferrail-receipts.jsonl is rarely the right place. For serve --app-mode, point it at receipts.db in Inferrail's data directory (~/.local/share/inferrail on Linux, ~/Library/Application Support/inferrail on macOS, %APPDATA%\inferrail on Windows).

Then ask, for example: "How much did the work tagged contract_review_42 cost?" If your requests carried work_id=contract_review_42, the agent calls get_spend with by: "work_id" and reads that group. Full tool contract: inferrail-mcp/README.md.

Status

Inferrail does not account for all spending on a provider account, only the supported requests that pass through a running gateway. Full scope and non-goals: docs/PRODUCT.md.

Documentation

• docs/integrations.md: clients, attribution, work tracking, voice, MCP
• docs/self-hosting.md: install, configuration, storage, budgets, dashboard
• docs/PRODUCT.md: exact current scope
• docs/ARCHITECTURE.md and docs/adr/: how and why it is built this way
• docs/privacy/usage-ping.md: the usage beacon
• openapi.json, config.schema.json, llms.txt: machine-readable references

Feedback, security, license

• Questions and bugs: GitHub issues.
• Security or privacy vulnerabilities: please report privately, as described in SECURITY.md.
• Contributing: CONTRIBUTING.md. pytest needs no API key or network.
• License: Apache-2.0.