Tessary

Tessary cost drift

cost_drift is one of Tessary's built-in classifiers: a tripwire that watches each call site's spend against its own past. It tracks dollars per turn, with token counts attached as evidence.

It catches the quiet ways an agent gets more expensive: a prompt that grew, retries that multiplied, caching that stopped working. Comparisons run against the call site's own history, both its recent normal and a reference pinned at the last deploy, so sudden jumps and slow creep both register. A drop in cost shows up as clearly as a rise. Findings go to triage, where the ones ruled real issues open cases.

5 questions

Answered, plainly.

Can cost_drift catch a cost that creeps up slowly, not just a sudden spike?Yes. cost_drift keeps a rolling baseline for sudden jumps and one pinned at a known-good point for the creep the rolling baseline would otherwise absorb.answer →Does cost_drift work for a scheduled agent that has no user sessions?Yes. cost_drift tracks dollars per turn at the call site, not per user session, so a scheduled job's runs build a baseline the same way.answer →How do I tell traffic growth apart from a broken agent in my LLM bill?Look at dollars per turn, not total spend: growth adds turns at the same per-turn price and leaves the ratio flat, while a defect moves the ratio.answer →What is Tessary's cost_drift classifier?It watches a call site's dollars per turn against that call site's own history, catching the cost increases that never throw an error, with token counts as evidence.answer →Why does each turn get pricier as an agent's run goes on?Each step's tool output and reasoning gets carried into the next call's prompt, so input tokens climb turn over turn even if the task stays the same.answer →

Two ways to run Tessary.

Tessary is an open-source agent reliability platform. Cloud and self-hosted run the same workflow on the OpenTelemetry traces your agent already emits.

Tessary Cloud

We host it for you. Send your first trace with nothing to deploy and no model key.

what's includedper organization

traces: 10,000 per calendar month
stored trace data: 1 GB
retention: 30 days
model credit: $10, one-time, for triage and root-cause analysis
credit card: not required

start for free

Self-hosted Tessary

Run the open-source code on your own infrastructure with one command. Add your own model key for triage and root-cause analysis.

set up with a coding agentinstall manually

Self-host Tessary for me by following https://github.com/tessaryai/tessary/blob/main/setup.md

docker compose -f oci://docker.io/tessaryai/tessary:compose up -d -y