fix(provider): sanitize tool schemas for strict validators

[sametakofficial]

Fixes #13737
Related: #11413, #8184, #13618

Tool schemas have two issues that cause 400s on strict validators (Codex, Vertex AI, SGLang): optional properties missing from required when additionalProperties: false is set, and non-standard keywords ($schema, ref) from Zod meta.

Added a recursive sanitize() step in ProviderTransform.schema() that strips the bad keywords and ensures all properties are in required when additionalProperties is false. Runs before provider-specific transforms.

Tested against Codex and Vertex AI endpoints — both previously 400, now work. 6 new unit tests, all 104 existing tests pass.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search results, I found two potentially related PRs that appear to be addressing similar schema sanitization issues:

1. PR fix: sanitize tool JSON schemas for Claude API compatibility #13619: "fix: sanitize tool JSON schemas for Claude API compatibility"

   • Likely addressing similar schema validation issues for a different provider (Claude API)

2. PR fix(google): sanitize unsupported JSON Schema keywords for Gemini API #13666: "fix(google): sanitize unsupported JSON Schema keywords for Gemini API"

   • Addressing schema keyword sanitization for the Google/Gemini API

These PRs seem to be part of a broader effort to sanitize tool schemas across different providers. They may be related work or even duplicative approaches to the same problem. I recommend checking if PR #13619 and #13666 are already merged or if they cover the same scope as PR #13738.

[rekram1-node]

Can u provide means to reproduce issue? You said before they 400, what tools were you passing?

[sametakofficial]

No custom tools — this happens with a completely clean config. I set up a fresh opencode.json with just one provider (@ai-sdk/openai-compatible pointing to a strict OpenAI-compatible endpoint), no MCP, no plugins, no custom tools. First message I send → 400.

The endpoint rejects opencode's built-in question tool. Here's what gets sent:

{
  "type": "object",
  "properties": {
    "question": { "type": "string" },
    "header": { "type": "string" },
    "options": { "type": "array", ... },
    "multiple": { "type": "boolean" }
  },
  "required": ["question", "header", "options"],
  "additionalProperties": false,
  "$schema": "https://json-schema.org/draft/2020-12/schema"
}

multiple is in properties but not in required, and additionalProperties is false. Strict validators won't accept that — every property needs to be in required if you're disabling additional properties.

The $schema and ref fields also cause issues on some endpoints.

Re: #13619 and #13666 — those are provider-specific fixes (Claude API and Gemini). This one runs in ProviderTransform.schema() before provider-specific transforms, so it catches the issue for all providers.

[sametakofficial]

Closing in favor of #13823 which takes a better approach — wrapping optional properties with anyOf: [original, {type: "null"}] preserves the optional semantics while satisfying strict validators. Our fix just forced everything into required which changes the contract. Nice work @echoVic 👍