RAGState and AnalysisState each declared the same five fields, so the generic
base could not name them: StateT was bound to BaseModel, and every access
went through cast(Any, state), a getattr by string, or a loop clearing fields
by name so it could skip the one only AnalysisState has.
EvidenceState declares them once. RAGState adds nothing, AnalysisState adds
executions and overrides begin_invocation to clear them. StateT binds to
EvidenceState, which removes all ten casts and both state-shape getattrs; the
three getattr(ctx.deps, "state") probes stay, since those check a
host-supplied object rather than our own state.
discover_evidence reached into capability.state for two fields. It now asks
through evidence_record() and citation_index(), alongside the
evidence_tool_names() and cite_available accessors it already used. The eval
runner's _RagLikeState protocol and the chat app's getattr reads described
this shape from outside and are gone.
Compatibility is semantic JSON-object equivalence, not bytes: field names and
nesting are unchanged, so a dict stored by 0.75.0 loads and re-dumps equal,
but deriving from a shared base reorders AnalysisState's keys. Nothing
serializes, hashes or string-compares this state — every carry point
re-validates by key.
Both optional capabilities read what earlier questions retrieved and cited from
the capability's state, so a host that carries only the message history hands
every run an empty record. Compaction then replaced the earlier evidence with
receipts and retained nothing, and the loss was invisible: the citations the host
already displayed were still there. It now refuses when it finds evidence from an
earlier question and no record of what that question cited.
`state_carried` reaches the optional capabilities through discovery, so the
refusal distinguishes a host that never carries state from a question that simply
cited nothing.
The documentation taught the pattern that breaks: the compose example is now
stateful and the requirement is stated where each capability is introduced.
The app's browser storage was doing exactly this, keeping only the fields the UI
reads. It now persists the whole namespace map, so the citation policy's
violations survive a reload as well as the evidence record.
`CitationPolicyCapability` makes the single enforcement decision, whatever mix of
evidence capabilities is registered: two of them must not each demand a citation for
one answer. It decides in `after_model_request`, when a response carries no tool calls
and the question can still be redirected. An explicitly ungrounded answer is a
declaration and is left alone; a question that gathered no evidence is left alone too,
read from the ledger rather than from a searches dict that a new question clears. When
the cite tool is already withdrawn the question is recorded in
`CitationPolicyState.violations` instead of pointing the model at a tool that is gone.
Registering it is the only switch. `DiscoveredEvidence` and discovery move to
`capabilities.evidence` so both optional capabilities share them, and `cite_available`
joins `evidence_tool_names` as public for the same reason.
Measured on Qwen3.6-35B over two arms of 37 questions, 29 of them unanswerable from
the corpus: explicit ungrounded declarations rose from 23 to 26, grounded answers to
unanswerable questions fell from 4 to 2, answerable questions stayed at 8 of 8, and
one redirect fired in the whole arm. Reading every answer found no invented grounding.
