Why does enabling an agent that has no trigger fail with a 409?

Tares refuses to enable an agent that has no trigger with a 409, because only a handoff from another agent starts it and there is nothing to switch on. Choose a trigger under Edit and the agent can be enabled. You can pick, change or clear the trigger at any time.

How it works

The trigger field on a Tares agent has a first choice, No trigger: only a handoff starts it. An agent set this way never wakes on its own. It runs only when another agent hands off to it.

That is why the 409 exists. A Tares agent is on in a project when a trigger of that project wakes it. An agent with no trigger has nothing to wake it, so there is nothing for Enable to turn on, and Tares refuses the request.

You see the same state in the console:

• The agent’s page says “Only a handoff from triage starts it”.
• An on handoff badge marks it.
• There is no Enable button.

Two related behaviors:

• New agents start off. An agent with a trigger runs on the next firing once you enable it.
• If you delete a trigger, the agents it woke stay in place, without a trigger of their own. They then behave as handoff-only agents until you pick a new trigger.

Set it up

1. Decide what you want. If the agent should wake on a condition, give it a trigger. If another agent should pass work to it, keep it handoff-only and do not enable it.
2. In the console, open the project’s Advanced setup and open the agent under Agents.
3. Click Edit.
4. In the trigger field, pick a trigger instead of No trigger: only a handoff starts it. To go the other way, change the trigger or clear it again. You can do this at any time.
5. Save, then click Enable. The button is there now because a trigger can wake the agent.
6. Make sure the instance has a model provider. Without one an agent can be created but not enabled.

If you manage agents as a catalog, the same rule shows up in YAML. The trigger key names the trigger that wakes the agent, and you leave it out for an agent only a handoff starts:

agents:
  - name: incident-first-look
    project: Default             # optional; the project that made it
    trigger: incident            # the trigger that wakes it
    enabled: true                # on in its project
    prompt: |
      You are an SRE taking the first look when an alert fires on this service. You are handed the
      correlated timeline: the firing alert plus the signals behind it and the request logs.
      Produce a tight incident note: what is failing and since when, the most likely cause tied to
      specific evidence lines, and a suggested next action. Do not speculate beyond the evidence.

Keep the trigger line for an agent that should wake on its own. Remove it for an agent that a handoff starts.

What you get

• A clear rule: an agent is either woken by a trigger or started by a handoff, and Tares does not let you enable one that has no way to start.
• Handoff-only agents that stay quiet until another agent passes them a finding, so a second-stage agent never fires by itself.
• Freedom to change your mind. Picking, changing or clearing the trigger under Edit works at any time.
• Safe cleanup. Deleting a trigger does not delete the agents it woke.

Once an agent has a trigger and is enabled, each firing runs it. The conclusion shows on the project’s Overview under What the agents found, and the run is listed under the agent’s Runs. The Build an AI SRE guide walks the whole loop on a demo system.

When something else fits

• If the agent should run when a condition is met, give it a trigger and enable it. The 409 is only for agents that have none.
• If the agent is a second stage in a chain, leave it on No trigger: only a handoff starts it and do not look for an Enable button. Set up the handoff from the agent that comes before it.
• If enabling is refused or does nothing and the agent does have a trigger, check that a model provider is configured on the instance.

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