OpenRouter xAI/Grok tool schemas fail when additionalProperties: false is emitted #23704

Summary

Tool calling fails in OpenCode for xAI models via OpenRouter because emitted tool/input JSON schemas include additionalProperties: false, which xAI rejects.

Repro

Model:

• openrouter/x-ai/grok-4.1-fast

Observed error:

• [xAI] Invalid request content: Schema validation failed: [standard_violation] /properties/properties/additionalProperties: property schema 'false' is not supported

Notes

This happens on the native OpenCode OpenRouter path, not from external plugins.

OpenCode currently runs tool schemas through ProviderTransform.schema(...) before handing them to the model. For xAI via OpenRouter, that transform should strip additionalProperties: false recursively.

Why this is safe

xAI structured output docs state:

• additionalProperties defaults to false
• schemas with boolean property schemas like false are rejected

So omitting explicit additionalProperties: false preserves behavior while avoiding the xAI validator error.

Proposed fix

In packages/opencode/src/provider/transform.ts, add an xAI/OpenRouter schema sanitizer:

• apply only when providerID === "openrouter" and model.api.id.startsWith("x-ai/")
• recursively remove additionalProperties: false
• preserve additionalProperties: true and object-valued additionalProperties

Related context

OpenCode already has related provider-specific schema sanitization work:

• Tool schemas cause 400 errors on strict validators (Codex, Vertex AI) #13737 Tool schemas cause 400 errors on strict validators
• fix: sanitize tool schemas for strict JSON Schema validators (#13737) #13823 sanitize tool schemas for strict JSON Schema validators