milo-agent-trace-cost-attributor

OTel-compatible per-task cost splitter for multi-agent systems. Free OSS processor + Lightning-paywalled batch API. No KYC, no signup, no $300/mo SaaS floor.

What it does

You're running a multi-agent system. Maybe LangGraph, maybe CrewAI, maybe hand-rolled. Your traces look like a forest of gen_ai.* spans. Your finance team wants to know:

• How much did each agent cost this month?
• How much did each user / tenant / workflow cost?
• Which agent is the budget hog?

Existing tools (Langfuse, LangSmith, Braintrust, Helicone, Arize Phoenix, Datadog LLM Obs) answer this — but they want $300–$1000/month minimum and they split by model, not by task. If you want per-tenant or per-agent rollups you're rebuilding it in BigQuery.

This service is the missing primitive. Drop in an OTel trace JSON, get back a per-attribution-key cost breakdown:

{
  "trace_id": "trace-multi-agent-001",
  "total_usd": 0.01910,
  "total_tokens": {"input": 2500, "output": 1000},
  "span_count": 4,
  "attributions": [
    {"key": "writer_agent",   "cost_usd": 0.0114, "input_tokens": 800,  "output_tokens": 600},
    {"key": "research_agent", "cost_usd": 0.00725, "input_tokens": 1500, "output_tokens": 350},
    {"key": "critic_agent",   "cost_usd": 0.00045, "input_tokens": 200,  "output_tokens": 50}
  ]
}

That's it. JSON in, JSON out, no dashboard, no account.

Endpoint catalog

Endpoint	Tier	Pricing	What it does
GET /	free	—	Service info + endpoint catalog + free sample
POST /attribute	free	10 req / 60s / IP	Single-trace attribution. Body: OTel trace JSON. Returns full report + summary.
POST /attribute/batch	paid	100 sats per 10k spans	Multi-trace batch. First call returns 402 + BOLT-11; re-call with ?payment_hash=<h> after settlement.
GET /pro	paid	$9 (one-time)	Legacy worked-example endpoint (kept for compat).

Quick start

pip install -e .
python -m milo_agent_trace_cost_attributor.server --port 8101

# Free single-trace attribution:
curl -X POST http://127.0.0.1:8101/attribute \
  -H "content-type: application/json" \
  -d @tests/fixtures/multi_agent_flat.json

# Paid batch:
curl -X POST http://127.0.0.1:8101/attribute/batch \
  -H "content-type: application/json" \
  -d '{"traces": [<otel_trace_1>, <otel_trace_2>, ...]}'
# → 402 + BOLT-11 + batch metadata. Pay invoice in any LN wallet, then:
curl -X POST "http://127.0.0.1:8101/attribute/batch?payment_hash=<h>" \
  -H "content-type: application/json" \
  -d '{"traces": [...]}'

Trace shapes accepted

Both common OpenTelemetry serializations work:

A. Flat agent-framework shape (LangGraph, CrewAI, custom):

{
  "traceId": "...",
  "spans": [
    {"spanId": "...", "name": "llm.chat",
     "startTimeUnixNano": ..., "endTimeUnixNano": ...,
     "attributes": {
       "agent.name": "research_agent",
       "gen_ai.request.model": "gpt-4o",
       "gen_ai.usage.input_tokens": 1000,
       "gen_ai.usage.output_tokens": 250
     }}
  ]
}

B. OTLP-wire shape (opentelemetry-instrumentation-openai-v2 etc.):

{
  "resourceSpans": [{
    "resource": {"attributes": [{"key": "service.name", "value": {"stringValue": "..."}}]},
    "scopeSpans": [{"spans": [{ ... }]}]
  }]
}

Attribution-key precedence

The processor picks the bucket key for each span using the first match of:

1. attributes["agent.name"] (OpenInference / agentic convention)
2. attributes["gen_ai.agent.name"] (OTel GenAI semconv, WIP)
3. attributes["service.name"] (OTel resource attribute)
4. span.name (fallback)

Override with your own field by passing custom logic in code (see domain.CostAttributor).

Cost-basis modes

Each per-span cost record carries a cost_basis:

• token_usage — span had gen_ai.usage.* tokens AND model is in the embedded price table. Highest confidence.
• token_no_price — tokens present but model unknown. Cost = 0; tokens surface so the consumer can price them themselves.
• duration_share — caller passed trace_total_usd and span lacks tokens; cost prorated by duration share of total trace duration.
• unknown — no signal at all. Cost = 0.

Pricing

Free OSS + free /attribute endpoint (rate-limited to 10/min/IP).

Hosted batch: 100 sats per 10,000 spans processed (~$0.04/10k spans at $40k/BTC). Pay-per-call via Lightning Network — no subscription, no KYC, no committee. Compare:

Tool	Floor	Per-call
Langfuse Cloud	$0 → $89/mo for >100k events	included in plan
LangSmith	$39/mo Plus, $499/mo Pro	trace-bundled
Braintrust	$249/mo Pro	event-bundled
Helicone Pro	$80/mo	included
this service	$0	100 sats / 10k spans (~$0.04)

Badge embed

Drop this in your repo README to attribute back:

[![cost-attributed by milo-agent-trace-cost-attributor](https://img.shields.io/badge/cost%20attribution-OTel-blue)](https://github.com/miloantaeus/milo-agent-trace-cost-attributor)

30-day kill criterion

Per Milo's market-truth doctrine, every SKU has a deprecation criterion. This one's: if no third party submits the first POST /attribute call within 30 days of public launch, kill the hosted service and keep only the OSS package. Distribution paths to publish: PyPI, OpenTelemetry contrib registry PR, awesome-llm-observability list.

Tests

pip install -e ".[test]"
pytest -q
# 38 passed

Architecture

Wired to milo-paywall-kit from day zero. Lightning provider, ledger, and HTTP-402 mediation live in the kit — this SKU only owns:

• domain.py — CostAttributor.attribute(), summarize(), price table
• server.py — FastAPI routes (/, /attribute, /attribute/batch, /pro), in-process IP rate-limiter

Lightning Network section

This service uses milo-paywall-kit for L402-style payment. To pay /attribute/batch: hit the endpoint, get a BOLT-11 invoice in the 402 body, pay it in any LN wallet (Alby, Phoenix, Wallet of Satoshi, Zeus), then re-call with ?payment_hash=<hash>. The settlement watcher (milo-agent-trace-cost-attributor-lightning-watcher) flips the ledger to paid within ~60s of settlement.

Stacker.News launch template

**milo-agent-trace-cost-attributor** — per-task cost splitter for multi-agent LLM systems, paid in sats

If you run LangGraph / CrewAI / any multi-agent system, you've hit this:
your OTel traces have hundreds of gen_ai.* spans and your finance team
wants per-agent cost rollups. Existing tools (Langfuse, LangSmith,
Braintrust) start at $300+/mo and split by model, not by task.

Built a tiny FastAPI processor. POST /attribute with an OTel trace JSON,
get back per-agent / per-user / per-tenant cost breakdown. Free for
single traces (rate-limited). Batch at 100 sats per 10k spans, paid via
Lightning. No KYC, no signup.

Free: <your-deploy-url>/attribute
Paid batch: <your-deploy-url>/attribute/batch
Code: https://github.com/miloantaeus/milo-agent-trace-cost-attributor

Zap me at <your-LN-address> if it saves your finance team an afternoon.

License

MIT.