# BehaviorNotFoundError

`rt.get_behavior(name)` couldn't resolve the name to a registered behavior. The framework refuses to fall back to a fuzzy match or a no-op because wrong-behavior dispatch would silently corrupt the audit trail.

Multi-inherits `LookupError` for back-compat — code that does `except LookupError` around behavior lookups continues to work.

The name resolution rule (canonical strict, lookup lenient) is defined on [`ambiguous-behavior-error`](https://docs.activegraph.ai/reference/errors/ambiguous-behavior-error/index.md) and applies here.

## Quick fix

Check the spelling and the pack:

```python
# List all registered behavior names:
status = rt.status(recent=0)
for b in status.registered_behaviors:
    print(b.name)
```

Or from the CLI:

```bash
activegraph inspect <store> --behaviors
```

Common causes when the name is right:

- **The behavior comes from a pack that isn't loaded.** Load the pack:

  ```python
  rt.load_pack(my_pack, settings=...)
  ```

- **The behavior is in user code that hasn't imported yet.** The `@behavior` decorator registers the behavior at module-import time. If the module containing the decorator runs after `Runtime(...)` is constructed, the registry will be empty. Import the module first.

- **You used a short name when a canonical name was needed.** If the behavior comes from a pack, use the fully-qualified form:

  ```python
  rt.get_behavior("diligence.researcher")   # not just "researcher"
  ```

  See [`ambiguous-behavior-error`](https://docs.activegraph.ai/reference/errors/ambiguous-behavior-error/index.md) for the resolution rule.

## How to diagnose

The error names the offending name and the registered behaviors:

```text
BehaviorNotFoundError: no behavior named 'extract_claims' is loaded

What failed:
  rt.get_behavior('extract_claims') could not resolve the name to a
  registered behavior.
    registered: 'diligence.researcher', 'diligence.memo_synthesizer'
```

From code:

```python
try:
    b = rt.get_behavior("extract_claims")
except BehaviorNotFoundError as e:
    print(e.name)         # 'extract_claims'
    print(e.registered)   # the registered names
    print(e.context["pack_state"])  # True if any pack is loaded
```

If `registered` is empty, no behaviors are registered at all — likely an import ordering problem (the `@behavior` decorators haven't run).

If `pack_state` is `True` but the name doesn't appear in `registered`, the name might exist as a short name that resolves to a different canonical — try the canonical form.

## When does this fire

At `rt.get_behavior(name)` and equivalent lookups. The runtime's trigger dispatch path doesn't go through this — events fire behaviors that subscribed to their type, regardless of name lookup. This error is for explicit by-name access (the operator CLI's `inspect --behavior <name>`, programmatic introspection, test fixtures referencing behaviors directly).

## Why the framework refuses to continue

Behaviors are addressable by their declared name. The lookup is strict — the runtime refuses to fall back to a fuzzy match or a no-op because a wrong-behavior dispatch would silently corrupt the audit trail. Behaviors live either in the global registry (decorated with `@behavior` or `@llm_behavior` at module load) or in a loaded pack; if neither has the name, the lookup misses.

See [`failure-model`](https://docs.activegraph.ai/concepts/failure-model/index.md) for the broader principle.

## What's related

- [`ambiguous-behavior-error`](https://docs.activegraph.ai/reference/errors/ambiguous-behavior-error/index.md) — fires when a short name resolves to two different behaviors. Defines the canonical-strict / lookup-lenient rule that applies here.
- [`tool-not-found-error`](https://docs.activegraph.ai/reference/errors/tool-not-found-error/index.md) — the symmetric case for tool lookups.
- [`missing-provider-error`](https://docs.activegraph.ai/reference/errors/missing-provider-error/index.md) / [`missing-tool-error`](https://docs.activegraph.ai/reference/errors/missing-tool-error/index.md) — the construction-time variants for when an `@llm_behavior` declares dependencies that aren't registered.