Tessary

Tessary behavior drift

behavior_drift is one of Tessary's built-in classifiers. It learns how an agent normally behaves from its own history, the steps it takes and the order it takes them in, and flags traces that depart from that. It doesn't judge whether any answer was correct.

It catches the changes correctness checks miss: an agent that starts skipping a step it always ran, calling tools it never used, or taking paths it has never taken. The baseline is fitted per call site from its own traffic, so a new project is quiet by design until normal is established. New patterns graduate into normal only after recurring across many sessions. Firings are grouped by cause and triaged, and a confirmed finding opens a case.

7 questions

Answered, plainly.

Does a behavior drift baseline go stale if an agent goes quiet?No. Silence doesn't age out a baseline; only new activity that looks different from what it was fitted on does, whenever the agent comes back.answer →What does a behavior drift baseline catch, and what does it miss?It catches a new or reordered step almost every time and misses a real share of the times an agent quietly stops doing something it used to do.answer →Why did my agent stop doing a step it always used to do?Something changed upstream, a prompt, a tool, or a logic branch, and Tessary's behavior drift classifier is built to flag that kind of omission.answer →Why doesn't one strange trace trigger a behavior drift alert?Drift is a property of a population's behavior over time, not a verdict on any single trace, so one unusual session doesn't fire it alone.answer →Why is my agent taking an action it never took before?Either a deliberate change or a bug pushed it off its usual path, and a brand new action is the drift Tessary's classifier catches most reliably.answer →What is Tessary's behavior_drift classifier?It learns an agent's normal steps and their order from that call site's own history, then flags traces that depart from it. It doesn't judge whether an answer was right.answer →What are the different kinds of agent behavior drift?One taxonomy splits it into three kinds: semantic drift from the original intent, behavioral drift into new strategies, and coordination drift between agents.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