> ## Documentation Index
> Fetch the complete documentation index at: https://docs.platform.nora.my/llms.txt
> Use this file to discover all available pages before exploring further.

# Where signals come from

> The channels that feed the queue — feedback, errors, verification, and more.

Nora watches your Agents from multiple angles. Every angle that spots a problem creates a Signal.

## The channels

### 1. User feedback

Any 👎 or written correction on an Agent's answer. Highest-quality signal — a real user said the answer was wrong.

Subtypes: thumbs, text correction, categorized feedback, reference correction.

### 2. Verification failures

If a Flow has a causal graph attached with verification on, every `blocked` or `warned` verdict creates a Signal (see [Verify agent answers](/build/causal-graph/verification)). Catches cases where the Agent's answer contradicts your domain knowledge — even when no user complained.

### 3. Retrieval misses

When retrieval returns zero results for a query, or when top-K scores are all below the confidence threshold. Suggests either a knowledge gap or a query the Agent doesn't rewrite well.

### 4. Tool errors

Persistent tool failures. A single 500 from a flaky API doesn't fire — but a rising rate of errors on the same tool does. Also fires on argument-shape errors (`400: missing required field`) because those usually mean the Agent's misunderstanding.

### 5. Guardrail hits

Any block from configured guardrails — PII in an outgoing message, policy violation, output-format check failure. These are usually the Agent trying to do the right thing but hitting a rail; sometimes the rail is misconfigured.

### 6. Behavioral drift

Statistical shifts in behavior over time — cost per run rising, latency rising, tool-usage patterns changing, retrieval-hit rates dropping. Fires when the shift is beyond normal noise and sustained for several days.

### 7. Regressions

New failures that look like they were previously fixed. Fires when a signal similar to a resolved one reappears after a version change. See [Regressions](/reliable/signals/regressions).

### 8. Approval rejections

Rejections in the Approvals queue with a reason. If reviewers keep rejecting a particular kind of Action, that's a Signal about the Agent's decision-making.

## Channel importance

Not all channels weigh equally. Default severity weighting:

* **User feedback (👎 with correction)** — highest.
* **Verification blocks** — high.
* **Regression** — high (something you already fixed came back).
* **User feedback (👎, no context)** — medium.
* **Tool errors, guardrail hits** — medium.
* **Retrieval misses** — low-medium.
* **Behavioral drift** — low (harder to attribute).

Adjust weights per Flow in **Reliable → Signals settings**.

## Adding a custom channel

Post your own signals via the API:

```
POST /signals
{
  "flow": "support-agent",
  "trace_id": "trace_abc",
  "source": "external-review",
  "severity": "high",
  "notes": "Reviewer flagged wrong policy citation"
}
```

Useful if you have an external QA workflow, or a compliance team that reviews sampled outputs offline.

## Turning off a channel

Per-Flow, in Signals settings. Turn off any channel you don't want to fire. Common: turn off "behavioral drift" for Flows that are still ramping and expected to shift.

## Signals and traces

Every signal (except the API-posted ones without a trace\_id) links back to a Trace. From the signal, click through to see the exact run that generated it. From a trace, click **Signals for this run** to see any signals fired by this run.