experimental.ts uses zodToJsonSchema which is broken with Zod v4 #20807

Description

server/routes/experimental.ts line 87 uses zodToJsonSchema() from [email protected] to convert tool parameter schemas for the HTTP API. This library is incompatible with Zod v4 — it returns garbage output for object schemas.

Example: a Zod v4 object schema with two string properties produces {"type": "string", "$schema": "http://json-schema.org/draft-07/schema#"} instead of the correct object schema. All property definitions, descriptions, and required fields are lost.

The prompt path (session/prompt.ts line 440) correctly uses z.toJSONSchema() which works with Zod v4. The experimental API endpoint should use the same method.

Related: #4357 (original report about lost descriptions, now fixed in the prompt path by Zod v4)

Steps to reproduce

1. Define a custom tool with described parameters
2. Query the experimental tools endpoint (GET /experimental/tools?provider=...&model=...)
3. Observe the returned parameter schemas are incorrect

Environment

• OpenCode: latest dev (8daeacc98)
• OS: macOS 15.4 (arm64)
• Zod: v4, zod-to-json-schema: 3.24.5