Ollama 0.11.8's llama.cpp structured-output implementation segfaults on
Pydantic v2's standard Optional pattern:
{"anyOf": [{"type": "string"}, {"type": "null"}]}
Confirmed on the deploy host: /api/chat request with the MVP's
ProvenanceWrappedResponse schema crashed Ollama with SIGSEGV; the client
saw httpx RemoteProtocolError → IX_002_000.
New _sanitise_schema_for_ollama walks the schema recursively and drops
"type: null" branches from every anyOf. Single-branch unions are
inlined so sibling keys (default, title) survive. This only narrows
what the LLM is *told* it may emit; Pydantic still validates the real
response body against the original schema and accepts None for
Optional fields if they were absent or explicitly null.
Existing unit tests updated: the "happy path" test no longer pins the
format to `_Schema.model_json_schema()` verbatim — instead it asserts
the sanitisation effect on a known-Optional field.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
