Inferrail

Know what your AI work costs.

Inferrail turns supported OpenAI chat-completion traffic into local, attributable economic receipts, so you can see which customer, workflow, or task caused the spend without storing prompts, responses, or tool payloads in Inferrail's own records.

For the supported chat-completions surface, Inferrail records known cost when measured usage and a verified price are available. Otherwise it reports unknown, never a fabricated $0. Attach customer, workflow, or task context when you need attributed economics.

See your first cost

pip install inferrail
inferrail demo                 # optional: canned data, no billing
inferrail try "Reply with one word: ready" --customer acme
inferrail report

inferrail demo is optional proof: no API key, no network call, and no provider billing. It runs canned requests through Inferrail's real engine with made-up prices labeled DEMO and prints one receipt per request plus an aggregate report. The try command is the shortest path to one real cost. It uses your existing OPENAI_API_KEY; if it is not set, Inferrail prints what is required. It prints the response, receipt, measured tokens, known cost or unknown, local receipt path, and the next report command:

Receipt ...
Provider ...
Model ...
Input tokens ...
Output tokens ...
Cost ...
Prompt stored     no
Response stored   no

Saved locally:
  /absolute/path/to/inferrail-receipts.jsonl

Next:
  inferrail report

inferrail report shows the all-up economics first: requests, failed requests, input tokens, output tokens, known cost, and unknown-cost requests. Explore existing dimensions afterward:

inferrail report --by customer
inferrail report --by workflow
inferrail report --by provider

CUSTOMER        REQUESTS  FAILED  INPUT TOKENS  OUTPUT TOKENS  COST (USD)  UNKNOWN COST
globex          2                 1621          416            $0.007825
acme            3                 1952          361            $0.000483   1
TOTAL           6                 3873          827            $0.008408   1

That 1 in UNKNOWN COST is deliberate: one request used a model Inferrail has no verified price for, and its cost shows as unresolved — never silently counted as $0.

Known cost requires measured usage and a verified price. Unknown stays unknown. Inferrail measures and attributes supported inference spend; it does not set budgets, send alerts, cap usage, or stop provider requests.

What a receipt contains

One payload-free JSON receipt per supported request:

{
  "receipt_id": "ir_1e6c916bac8940ca8a85",
  "provider": "openai",
  "model": "gpt-4o-mini",
  "prompt_tokens": 842,
  "completion_tokens": 191,
  "estimated_cost_usd": "0.000241",
  "attributes": { "customer": "acme", "workflow": "contract-review" }
}

(Trimmed — the full record also carries pricing provenance, status, route, timestamp, latency, and retry count. See Privacy boundary below for the complete shape.)

Task economics

One task is rarely one call. Tag every request belonging to one unit of work with the same attribution value, then ask Inferrail what the task cost:

export OPENAI_API_KEY=<your-openai-api-key>
inferrail try "Reply with one word: ready" -a task_id=bug_9281
inferrail try "Summarize: the retry patch is deployed" -a task_id=bug_9281
inferrail transaction bug_9281

Task:        bug_9281
Transaction: tx_72fcfcca9ede9d2facc3
Status:      success

EVENT TYPE  EVENT ID                 STATUS   COST
inference   ir_f6fb6403d5324ea0acf9  success  $0.000003
inference   ir_756cc072a27f42f4a2ea  success  $0.000007

Known total cost: $0.00001

This needs a real provider request — inferrail demo's canned data doesn't include a task id to correlate offline. Over HTTP, an X-Inferrail-Attribute-Task-Id: bug_9281 header does the same thing; inferrail.track_task(task_id=...) (see Attribute spend below) attaches it automatically to every nested call in an agent run, no header-threading required. See docs/adr/0008.

Use it as a gateway

For a long-running application, start the separate gateway process. The gateway process must have access to the provider credential through the configured environment variable; a key held only inside application memory is not automatically transferred to the gateway.

inferrail serve --quickstart

curl http://127.0.0.1:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "X-Inferrail-Attribute-Customer: acme" \
  -d '{
    "model": "default",
    "messages": [{"role": "user", "content": "Say hello in five words."}]
  }'

The response is standard OpenAI choices/usage plus a non-standard inferrail block (route, provider, latency, retries) any OpenAI client already ignores. X-Inferrail-Attribute-* headers are optional attribution — never forwarded upstream. See examples/basic_chat_request.py for a minimal Python client, or point a supported OpenAI-compatible chat client at http://127.0.0.1:8000/v1. An OpenAI SDK client that does not set base_url can use its existing OPENAI_BASE_URL environment mechanism instead.

The default receipt is one JSONL line per supported request in ./inferrail-receipts.jsonl, relative to the gateway's working directory. Treat that file as machine/audit evidence; use inferrail report for the human aggregate and inferrail transaction <task-id> for a task total.

# LangChain
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    base_url="http://127.0.0.1:8000/v1",
    api_key="not-needed",  # or your INFERRAIL_GATEWAY_TOKEN if auth is enabled
    model="default",
)

# LlamaIndex
from llama_index.llms.openai_like import OpenAILike

llm = OpenAILike(
    model="default",
    api_base="http://127.0.0.1:8000/v1",
    api_key="not-needed",
    is_chat_model=True,
    context_window=8192,
)

# CrewAI
from crewai import LLM

llm = LLM(
    model="openai/default",  # "openai/" prefix required by CrewAI
    base_url="http://127.0.0.1:8000/v1",
    api_key="not-needed",
)

"model" normally selects a named route from inferrail.yaml (e.g. "default"), which maps to a provider + underlying model. If default_provider is set in your config, a model that matches no route is instead forwarded to that provider unchanged — so "model": "gpt-5.6-sol" works with no route pre-registered for it. Named routes always take priority. This passthrough is on by default for the zero-config quickstart path, off by default otherwise. Full design: docs/adr/0007.

Attribute spend

Three ways to attach business context to a request, all landing in the same attributes: dict[str, str] on its receipt:

• HTTP header (gateway): X-Inferrail-Attribute-<Name>: <value>, e.g. X-Inferrail-Attribute-Task-Id: bug_9281.
• CLI flag (inferrail try): --customer/--workflow shorthand, or generic -a <name>=<value> for anything else, including task_id.
• Ambient, for nested agent calls: inferrail.track_task attaches X-Inferrail-Attribute-Task-Id to every outgoing request for the duration of a with block or decorated function — no threading a task_id parameter through nested function signatures by hand.

import inferrail
from openai import OpenAI

client = OpenAI(
    base_url="http://127.0.0.1:8000/v1",
    api_key="not-needed",
    # also accepted by LangChain's ChatOpenAI, CrewAI's LLM, etc. via
    # their own http_client= argument
    # base_url must match the client's own base_url above — the header is
    # only ever attached to requests going to that destination.
    http_client=inferrail.attributed_http_client(base_url="http://127.0.0.1:8000/v1"),
)

@inferrail.track_task(task_id="bug_9281")
def fix_bug():
    client.chat.completions.create(...)  # tagged automatically
    run_subagent()  # nested calls too — no task_id parameter needed

with inferrail.track_task(task_id="..."): works the same way. Sync and async are both supported (attributed_async_http_client(base_url=...) for AsyncOpenAI/async frameworks); concurrent tasks never cross-contaminate. This is a small client-side convenience over the HTTP header above — no gateway or schema change, task_id only, no public API stability commitment yet. See docs/adr/0009.

Once tagged, inferrail report shows the all-up aggregate, while inferrail report --by <provider|model|route|attribute-name> aggregates receipts by any of these dimensions — customer, workflow, task_id, or anything else you've attached.

Referral early access

Referral access is opening soon. Planned early-access rewards are based on verified routed usage, not signup:

1 verified referral
→ +90 days of cost history for both sides

3 verified referrals
→ Pro for one year + unlimited seats

10 verified referrals
→ Founding Operator
→ permanent Pro
→ logo on the site
→ roadmap vote
→ private channel

25 verified referrals
→ Inferrail free for life
→ 20% recurring on additional teams referred

Program terms will be published when referral access opens.

See the current program presentation at tryinferrail.com.

How it works

InferenceEngine normalizes the request, resolves model to a route in inferrail.yaml (a pure config lookup — no cost/latency-aware selection in v0.1), calls the one provider adapter in this version (OpenAIProvider, generic over base_url — OpenAI itself, Azure OpenAI's compatible surface, vLLM, llama.cpp-server, or anything else speaking the same wire format), and emits a telemetry event and a receipt for every supported request, success or failure. Full lifecycle, package layout, and the streaming/retry boundaries: docs/ARCHITECTURE.md.

Privacy boundary

Inferrail does not persist prompts, responses, or tool payloads in its local receipt or telemetry records — structurally: neither schema has a field capable of holding message content, and test_inference_receipt_has_no_payload_fields enforces it. This is a claim about Inferrail's own local records, not about the request path as a whole — your configured provider still receives the real prompt either way; Inferrail is a pass-through gateway to it, not a privacy boundary against it.

Inferrail currently measures supported OpenAI chat-completions traffic. It is not a background monitor: it records while requests pass through the running process and serves nothing when that process is stopped. It does not enforce budgets or control provider spend.

inferrail try says this in its own output too, not just in the schema:

  Prompt stored     no
  Response stored   no

The full receipt shape, all fields:

{
  "receipt_id": "ir_1e6c916bac8940ca8a85",
  "route": "default",
  "provider": "openai",
  "model": "gpt-4o-mini",
  "status": "success",
  "prompt_tokens": 842,
  "completion_tokens": 191,
  "pricing": {
    "input_usd_per_million": "0.15",
    "output_usd_per_million": "0.60",
    "source": "https://developers.openai.com/api/docs/pricing",
    "verified_date": "2026-08-16"
  },
  "estimated_cost_usd": "0.000241",
  "attributes": { "customer": "acme", "workflow": "contract-review" },
  "total_latency_ms": 15.96,
  "retry_count": 0
}

If Inferrail can't verify a price for the (provider, model) pair, pricing and estimated_cost_usd are null — never a guessed or fabricated cost. You can check the no-payload claim yourself against a running gateway, not just take it on faith: docs/PRODUCT.md's verification walkthrough. Design rationale: docs/adr/0005.

MCP

pip install "inferrail[mcp]"

An MCP server (inferrail-mcp), published on the MCP registry as io.github.domondi1/inferrail, exposes Inferrail's local receipt ledger to any MCP-aware agent (Claude Code, Claude Desktop, Cursor, ...) as two read-only tools — neither executes inference nor spends provider budget:

{
  "mcpServers": {
    "inferrail": { "command": "inferrail-mcp" }
  }
}

Claude Code: claude mcp add inferrail -- inferrail-mcp. Full contract: inferrail-mcp/README.md.

Supported today

• POST /v1/chat/completions: streaming (stream: true, real SSE passthrough) and tool/function calling, single string message content, no n != 1
• GET /health
• One provider adapter, generic over any OpenAI-compatible HTTP endpoint
• Named-route + optional passthrough model routing (above)
• Per-route retry with backoff on transient provider errors
• Local structured telemetry and payload-free cost receipts for supported requests, plus inferrail report, grouped reports, and inferrail transaction <task-id>
• CLI: inferrail demo, try, serve (--quickstart), config check, report, transaction

Not yet

Honest edges, not silent gaps — full list in docs/PRODUCT.md:

• Cost- or latency-aware routing, or automatic failover to a different provider/model on error — routing is a static config lookup
• Budgets, spend limits, or blocking a request based on cost
• Any provider whose wire protocol isn't OpenAI-compatible (native Anthropic, Gemini, Bedrock, ...)
• The full OpenAI API surface — only /v1/chat/completions and /health exist; no embeddings, assistants, batch, images, or audio
• Multi-user auth or role-based access control — INFERRAIL_GATEWAY_TOKEN is one shared secret, not a user system
• Any hosted or cloud-operated component
• Non-LLM economic events (browser, search, compute/sandbox, MCP tool cost) in a TaskTransaction — its only event type today is inference
• Outcome or business-value linkage (success signal, revenue, margin) on a TaskTransaction — it aggregates cost only

Deployment boundary

Single node. The receipt ledger is a local append-only JSONL file, so every process that should appear in one report must write to one file on one filesystem.

• Concurrent writers to the same file are safe: each receipt is written as a single atomic O_APPEND write, so threads and multiple processes on the same host can share one ledger without interleaving or losing records.
• Not supported: several hosts writing to one ledger, aggregating ledgers across machines, or anything resembling a shared/hosted control plane. Running Inferrail on N hosts gives you N separate ledgers, and nothing in the product merges them.
• inferrail report and inferrail transaction read the whole file into memory. That is fine for the millions-of-bytes range a developer preview produces; it is not a query engine, and there is no retention, rotation, or compaction. Rotate the file yourself if it grows.

Anything beyond one host is out of scope for v0.x — see docs/PRODUCT.md.

Configuration

For a real deployment instead of quickstart defaults:

cp inferrail.example.yaml inferrail.yaml
cp .env.example .env      # then add a real OPENAI_API_KEY
inferrail config check    # validate without starting a server
inferrail serve

inferrail.yaml only ever holds the name of an environment variable for a secret, never the secret itself. Full shape (providers, routes, telemetry, receipts, pricing overrides): inferrail.example.yaml.

By default the gateway binds to 127.0.0.1:8000 with no auth. Set INFERRAIL_GATEWAY_TOKEN to require callers to send Authorization: Bearer <token> — see SECURITY.md.

Documentation

• docs/PRODUCT.md — exact current scope
• docs/ARCHITECTURE.md — package layout, request lifecycle
• docs/adr/ — why specific structural decisions were made
• openapi.json / config.schema.json / llms.txt — machine-readable references for tooling and agents
• SECURITY.md

Development

git clone https://github.com/domondi1/inferrail.git && cd inferrail
pip install -e ".[dev,mcp]"
ruff check . && mypy && pytest

pytest needs no API key or network access — see CONTRIBUTING.md.

License

Apache License 2.0 — see LICENSE.