Thread per-case source scope through the capability runner

The runner passed document_filter onto capability state but not sources,
so an eval case could not be scoped to named databases. Scoping is what
the multi-database acceptance dataset has to assert, both that a scoped
question honours its databases and that an empty scope refuses rather
than answering without evidence.

sources=[] covers no database while None covers every one the client
covers, so the empty list is threaded on an is-not-None check and a test
pins the two apart.

evaluations/evaluations/capability_runner.py

@@ -130,6 +130,7 @@ def _prepare_agent(
     document_filter: str | None,
     request_limit: int | None,
     compaction: bool = False,
+    sources: list[str] | None = None,
 ) -> tuple[RAGCapabilityBase[Any], _EvalDeps, Agent[_EvalDeps, str]]:
     capability = capability_factory(
         db_path=db_path,
@@ -141,6 +142,8 @@ def _prepare_agent(
     state = capability.state_type()
     if document_filter is not None:
         state.document_filter = document_filter
+    if sources is not None:
+        state.sources = sources
 
     capabilities: list[AbstractCapability] = [capability]
     if compaction:
@@ -169,6 +172,7 @@ async def run_capability_question(
     document_filter: str | None = None,
     request_limit: int | None = None,
     message_history: list[ModelMessage] | None = None,
+    sources: list[str] | None = None,
 ) -> CapabilityRunResult:
     """Run a single question through a capability and return answer + retrieval data.
 
@@ -177,8 +181,11 @@ async def run_capability_question(
     are extracted from the state for downstream eval scoring.
 
     The capability must produce a state with RAG-capability-shaped fields (citation
-    index, searches, optional document filter) — i.e. ``RAGState`` or
-    ``AnalysisState`` from ``haiku.rag.capabilities``.
+    index, searches, optional document filter and source scope) — i.e. ``RAGState``
+    or ``AnalysisState`` from ``haiku.rag.capabilities``.
+
+    ``sources`` scopes the question to named databases; ``[]`` covers none and
+    ``None`` covers everything the client covers.
     """
     capability, deps, agent = _prepare_agent(
         capability_factory,
@@ -187,6 +194,7 @@ async def run_capability_question(
         capability_model,
         document_filter,
         request_limit,
+        sources=sources,
     )
     agent_result = await agent.run(question, deps=deps, message_history=message_history)
     traffic = _count_tool_traffic(
@@ -205,6 +213,7 @@ async def run_capability_conversation(
     capability_model: str | Model,
     document_filter: str | None = None,
     compaction: bool = False,
+    sources: list[str] | None = None,
 ) -> list[CapabilityRunResult]:
     """Run a conversation's user turns sequentially through one capability.
 
@@ -223,6 +232,7 @@ async def run_capability_conversation(
         document_filter=document_filter,
         request_limit=None,
         compaction=compaction,
+        sources=sources,
     )
     history: list[ModelMessage] | None = None
     results: list[CapabilityRunResult] = []

evaluations/tests/test_capability_runner.py

@@ -345,6 +345,80 @@ async def test_conversation_applies_document_filter(tmp_path):
     assert deps_seen[0].state["rag"]["document_filter"] == "uri = 'manual.pdf'"
 
 
+async def test_question_applies_sources(tmp_path):
+    """Per-case `sources` must reach the capability state, so a scoped question
+    only ever searches the databases it named."""
+    deps_seen = []
+
+    async def _run(question, deps=None, message_history=None):
+        deps_seen.append(deps)
+        return SimpleNamespace(output="a", new_messages=lambda: [])
+
+    with patch("evaluations.capability_runner.Agent.run", side_effect=_run):
+        await run_capability_question(
+            create_rag,
+            tmp_path / "rag.lancedb",
+            AppConfig(),
+            "q",
+            TestModel(call_tools=[]),
+            sources=["northern"],
+        )
+
+    assert deps_seen[0].state["rag"]["sources"] == ["northern"]
+
+
+async def test_question_distinguishes_empty_sources_from_none(tmp_path):
+    """`sources=[]` covers nothing and `sources=None` covers everything, so the
+    empty list must survive to the state rather than being treated as unset."""
+    deps_seen = []
+
+    async def _run(question, deps=None, message_history=None):
+        deps_seen.append(deps)
+        return SimpleNamespace(output="a", new_messages=lambda: [])
+
+    with patch("evaluations.capability_runner.Agent.run", side_effect=_run):
+        for sources in ([], None):
+            await run_capability_question(
+                create_rag,
+                tmp_path / "rag.lancedb",
+                AppConfig(),
+                "q",
+                TestModel(call_tools=[]),
+                sources=sources,
+            )
+
+    assert deps_seen[0].state["rag"]["sources"] == []
+    assert deps_seen[1].state["rag"]["sources"] is None
+
+
+async def test_conversation_applies_sources(tmp_path):
+    """Scope must hold for every turn of a conversation, not just the first."""
+    from evaluations.capability_runner import run_capability_conversation
+
+    deps_seen = []
+
+    async def _run(question, deps=None, message_history=None):
+        deps_seen.append(deps)
+        return SimpleNamespace(
+            output="a", all_messages=lambda: [], new_messages=lambda: []
+        )
+
+    with patch("evaluations.capability_runner.Agent.run", side_effect=_run):
+        await run_capability_conversation(
+            create_rag,
+            tmp_path / "rag.lancedb",
+            AppConfig(),
+            ["q1", "q2"],
+            TestModel(call_tools=[]),
+            sources=["southern"],
+        )
+
+    assert [d.state["rag"]["sources"] for d in deps_seen] == [
+        ["southern"],
+        ["southern"],
+    ]
+
+
 async def test_conversation_carries_one_state_dict_across_turns(tmp_path):
     """Capabilities read and write state through the deps dict; carrying the
     same dict across turns is what lets compaction see earlier questions'