Port from anomalyco/opencode#31877: JSON Schema type arrays like
["number","string"] (common in MCP tool schemas) were collapsed to the
first non-null type, silently dropping every other branch. Several
tool-call backends reject the array form outright — llama.cpp's grammar
generator and Gemini via OpenAI-compatible transports (e.g. GitHub
Copilot proxying to Gemini) 400 on it.
_sanitize_node now mirrors @ai-sdk/google: a single non-null type stays
type:X (+nullable if null was present), multiple non-null types become
an anyOf of single-type schemas so no branch is lost, and an all-null
array becomes type:null. Single-null collapse is unchanged.
Verified nested (object props, array items) survive the full sanitize
pipeline — combinator stripping is top-level-only and nullable-union
collapse only fires on single-survivor unions, so multi-type anyOf is
left intact.
teknium1
ce038a0e05