fix(provider): infer type 'object' for schemas with properties but missing type in Gemini sanitization

[ChickenBreast-ky]

Summary

Follow-up to #11888. sanitizeGemini strips properties/required from non-object types, but misses the case where type is entirely undefined (undefined).

Fixes #13148

Problem

The current check:

if (result.type && result.type !== "object") {
  delete result.properties
  delete result.required
}

When type is undefined, result.type && ... short-circuits to false, so properties/required are not removed. MCP tools like Notion MCP define schemas where type is omitted but properties/required are present (valid per JSON Schema spec as implicit objects):

{
  "data": {
    "description": "The data required for updating a page",
    "properties": { "page_id": { "type": "string" } },
    "required": ["page_id"]
  }
}

This causes:

Bad Request: GenerateContentRequest.tools[0].function_declarations[90].parameters.properties[data].properties: only allowed for OBJECT type

Solution

Infer type: "object" when properties or required exist but type is missing, before the existing non-object stripping logic:

if (!result.type && (result.properties || result.required)) {
  result.type = "object"
}

Changes

• packages/opencode/src/provider/transform.ts: Added 4 lines to infer missing type
• packages/opencode/test/provider/transform.test.ts: Added 2 test cases for missing type inference

Related Issues

• [bug] Gemini schema sanitization misses properties/required when type is undefined #13148
• Follow-up to fix(provider): strip properties/required from non-object types in Gemini schema #11888 / [bug] Gemini API rejects MCP tool schemas with properties/required on non-object types #11889

[github-actions]

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No duplicate PRs found

[ChickenBreast-ky]

CI note: e2e (windows) failure is unrelated — zod cache ENOENT + session file path issue on Windows CI environment. unit (linux) (which covers this change) passed ✅