costlyinfra-meter

Request-level AI economics for Meter.

It answers questions a monthly total cannot: why did this agent run cost $1.42, which step spent it, which agents are running right now, and did last week's prompt change make every run more expensive.

Stdlib-only, no dependencies.

What it never sends

Prompts, responses, messages, tool arguments, tool results, retrieved documents, exception messages and stack traces.

Not truncated, not redacted, not behind a setting — the events this SDK can construct have no field for them, and the server rejects a payload that carries one. What travels is identity, counts, timing and money: which prompt version, how many tokens, how long, how much.

Install

pip install costlyinfra-meter

export METER_INGEST_URL="https://your-meter/api/hook/events"
export METER_INGEST_TOKEN="…"          # Install SDK page -> Generate token
export METER_APPLICATION="support-agent"
export METER_ENVIRONMENT="production"
export METER_RELEASE_VERSION="2026.9.1"   # optional

With no URL or token configured every call is a no-op, so importing this into a test suite or a local script costs nothing and needs no conditionals.

One model call

from costlyinfra_meter import Meter

meter = Meter(application="support-agent", environment="production")
client = meter.wrap(anthropic_client, feature_id="answer-generation")

response = client.messages.create(model="claude-sonnet-4-6", messages=messages)

The wrapped client behaves exactly like the original — same arguments, same return value. Each call becomes its own one-span trace; you never mention traces.

If your client is behind a wrapper or a subclass, name the provider outright: meter.wrap(client, provider="anthropic").

A multi-step agent

with meter.agent(
    "resolve-ticket",
    feature_id="ticket-resolution",
    customer_id="customer-123",
) as run:
    classification = run.llm("classify", lambda: anthropic_client.messages.create(...))
    documents      = run.tool("retrieve-documents", retrieve_documents)
    answer         = run.llm("generate-answer", lambda: anthropic_client.messages.create(...))

Each step returns whatever your function returned. Latency, status, tokens, model and provider are recorded automatically. An exception fails the step and the run and is re-raised unchanged — its message is never transmitted.

Besides llm and tool there are retrieval, embedding, guardrail and evaluation, which record the same way and are separated in reporting.

Prompt identity, when you version prompts:

run.llm("generate-answer", call, prompt_id="answer-ticket", prompt_version="5.0")

Long-running agents

A run sends a heartbeat every 30 seconds so a slow-but-healthy agent is not mistaken for a hung one. Heartbeats stop the moment the run ends — success, failure or cancellation — and the timer is cancelled rather than abandoned.

Meter derives "stale" at read time from that activity. A stale run has not failed: it may still finish, and it does so normally when it does.

Queues and workers

# producer
with meter.agent("resolve-ticket") as run:
    queue.send("continue-agent", trace_context=run.export_context())

# worker
with meter.resume(job.trace_context) as run:
    run.tool("process-document", process_document)

Both processes write to one trace. The exported context carries identifiers only — trace id, parent span id, application, feature, environment, release. No token, no customer content: it is designed on the assumption that anything on a queue eventually gets logged.

Delivery

Recording appends to an in-memory queue and returns. One background worker batches and posts; nothing on your call path blocks, raises or touches the network. If Meter is down or misconfigured, your agent is unaffected.

Bounded: one worker thread per meter whatever your traffic, and a capped queue (10,000 events). If it fills — a stalled endpoint, a burst — the oldest events are dropped and counted on meter.dropped. Metering degrades visibly; your application does not.

A batch keeps one id across retries, so a retry after an ambiguous timeout (server committed, response lost) is recognised as a replay rather than doubling a run's cost.

Call flush() where the worker may not get scheduled — a serverless handler, a script about to exit:

meter.flush()          # True if the queue drained, False on timeout

An atexit hook flushes on normal shutdown.

Upgrading from 1.x

2.0 replaces per-call cost reporting with traces. meter.record(...), record_anthropic(...) and the other record_* methods are gone; use meter.wrap(...) for a single call and meter.agent(...) for a workflow. METER_TOKEN is now METER_INGEST_TOKEN, and METER_APPLICATION is new and required for anything to be grouped sensibly.