# Capabilities

haiku.rag provides native [Pydantic AI capabilities](https://ai.pydantic.dev/capabilities/):

| Capability | Use it for |
|---|---|
| [`RAGCapability`](rag.md) | Grounded document search and citations. |
| [`AnalysisCapability`](analysis.md) | Corpus computation and structural analysis with sandboxed Python. |
| `EvidenceCompactionCapability` | Optional. Shrinking a conversation's history to the evidence that was cited. |
| `CitationPolicyCapability` | Optional. Requiring every answer to declare what grounds it. |

The two evidence capabilities are deferred by default. An agent initially sees only their descriptions and the standard `load_capability` tool. Instructions and tools enter the model context only when the model loads a capability.

## Compose an agent

```python
from pydantic_ai import Agent
from haiku.rag.capabilities.rag import create_capability

rag = create_capability(db_path="my.lancedb")
agent = Agent("openai:gpt-5", capabilities=[rag])

result = await agent.run("What does the knowledge base say about X?")
print(result.output)
```

Attach both capabilities when an agent should choose between retrieval and computation:

```python
from haiku.rag.capabilities.analysis import create_capability as analysis
from haiku.rag.capabilities.rag import create_capability as rag

agent = Agent(
    "openai:gpt-5",
    capabilities=[rag(db_path="my.lancedb"), analysis(db_path="my.lancedb")],
)
```

## Multi-turn conversations

Every question adds its search results to the history, so requests grow turn after
turn, and can degrade answers or exceed a provider's limits as they do. Register the
compaction capability to replace earlier questions' evidence with the evidence that
was actually cited:

```python
from haiku.rag.capabilities.compaction import create_capability as compaction
from haiku.rag.capabilities.rag import create_capability as rag

agent = Agent(
    "openai:gpt-5",
    capabilities=[rag(db_path="my.lancedb"), compaction()],
)
```

Cited text and cited page images are kept in full, grouped by the question that
cited them, and stay citable by the same chunk ids. Everything else earlier becomes a
short receipt. Registering the capability is the only switch: leave it out and the
transcript reaches the model untouched. There is nothing to configure.

Compaction rewrites the request, never the stored history, so `all_messages()` still
holds everything the run gathered. Retained evidence still grows with the
conversation — this reduces what a request carries, it does not bound it. A host that
needs more aggressive pruning can compact its own requests further, on the wire only.

Resuming a question (deferred tool results, an interruption, a suspension) requires
the host to carry the capability state from the run being resumed, alongside the
message history. Without it the identity of the question in progress is unknowable
and the run fails rather than silently treating it as a new question.

## Requiring citations

Citing is always available and always recorded, but nothing requires it. Register the
citation policy capability to make every answer declare its grounding:

```python
from haiku.rag.capabilities.policy import create_capability as citation_policy
from haiku.rag.capabilities.rag import create_capability as rag

agent = Agent(
    "openai:gpt-5",
    capabilities=[rag(db_path="my.lancedb"), citation_policy()],
)
```

An empty citation is a valid declaration: a model that finds nothing relevant calls
the cite tool with an empty list, which records the answer as *ungrounded* — distinct
from an answer that declared nothing at all. That distinction is what makes requiring
a declaration possible without forcing the model to invent grounding.

When a question ends undeclared, the model is asked once to record what grounded the
answer it already gave. It is not asked to change the answer. If the cite tool is no
longer available by then, or the question finishes undeclared anyway, it is recorded as
a violation in `CitationPolicyState` under `"citation_policy"`, since pointing a model
at a tool that is gone costs it retries.

What gets enforced is every answer in a conversation that has something to declare:
either this question retrieved evidence, or the conversation has already cited
something, which stays available to later answers. So a follow-up about evidence cited
earlier is enforced even though it searched nothing — that case is the reason the
capability exists. It also means that once anything has been cited, later turns are
enforced too, a greeting included; the model satisfies the policy by citing an empty
list, at the cost of one extra request. A conversation with neither a current-question
evidence outcome nor any earlier citation is not enforced.

Exactly one policy capability makes the decision, however many evidence capabilities
are registered, so two of them cannot each demand a citation for one answer.

## State

Capabilities use a plain `state: dict[str, Any]` attribute on agent dependencies when one is available. RAG state lives under `"rag"`; analysis state lives under `"analysis"`. This keeps state independent of any transport or UI protocol.

Applications serving AG-UI should adapt the agent with Pydantic AI's `AGUIAdapter`. Native model and tool events require no haiku.rag-specific bridge.

## Database path

Both factories resolve their database in this order:

1. The `db_path` argument.
2. `HAIKU_RAG_DB`.
3. `config.storage.data_dir / "haiku.rag.lancedb"`.