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fix(provider): sanitize xAI tool schemas for OpenRouter and native xai provider - #23706

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fix(provider): sanitize xAI tool schemas for OpenRouter and native xai provider#23706
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anomalyco:devfrom
dotCipher:fix/openrouter-xai-tool-schema-sanitization

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@dotCipher dotCipher commented Apr 21, 2026 •
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Issue for this PR

Closes #23704

Type of change

  • Bug fix
  • New feature
  • Refactor / code improvement
  • Documentation

What does this PR do?

Tool calling fails for xAI models (e.g. grok-4.1-fast) when used through OpenRouter or the native xai provider. The error is:

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

xAI structured output docs state:

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

So the fix strips additionalProperties: false from tool/input JSON schemas before sending to xAI. This preserves the intended strictness (since false is the default) while avoiding the validator rejection.

The change is scoped to:

  • providerID === "xai" (native xAI provider)
  • providerID === "openrouter" with model.api.id.startsWith("x-ai/") (xAI models via OpenRouter)

Non-xAI models are unaffected.

How did you verify your code works?

Added unit tests in packages/opencode/test/provider/transform.test.ts:

  • Verifies recursive removal of additionalProperties: false for both OpenRouter xAI and native xai provider
  • Verifies object-valued and true additionalProperties are preserved
  • Verifies non-xAI OpenRouter models are not affected

Screenshots / recordings

N/A — no UI changes.

Checklist

  • I have tested my changes locally
  • I have not included unrelated changes in this PR

@github-actions github-actions Bot added the needs:compliance This means the issue will auto-close after 2 hours. label Apr 21, 2026
@github-actions github-actions Bot mentioned this pull request Apr 21, 2026
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github-actions Bot commented Apr 21, 2026

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

POTENTIAL DUPLICATE FOUND:

PR #23707 - "fix(provider): sanitize xAI tool schemas for OpenRouter"

Note: PR #23706 is the current PR you're analyzing, so #23707 is a potential duplicate that should be reviewed for consolidation or coordination.

@dotCipher
fix(provider): sanitize xAI tool schemas for OpenRouter and native xa…
c8692ce 
…i provider

Strip additionalProperties: false from tool/input JSON schemas
when targeting xAI models via OpenRouter or the native xai provider.
xAI rejects this keyword while their validator already defaults to false.

Fixes anomalyco#23704
@dotCipher
dotCipher force-pushed the fix/openrouter-xai-tool-schema-sanitization branch from 5bd4988 to c8692ce Compare April 21, 2026 15:45
@dotCipher dotCipher changed the title fix(provider): sanitize xAI tool schemas for OpenRouter fix(provider): sanitize xAI tool schemas for OpenRouter and native xai provider Apr 21, 2026
@dotCipher dotCipher changed the title fix(provider): sanitize xAI tool schemas for OpenRouter fix(provider): sanitize xAI tool schemas for OpenRouter and native xai provider Apr 21, 2026
@github-actions github-actions Bot removed the needs:compliance This means the issue will auto-close after 2 hours. label Apr 21, 2026
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github-actions Bot commented Apr 21, 2026

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Thanks for updating your PR! It now meets our contributing guidelines. 👍

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Thanks for updating your PR! It now meets our contributing guidelines. 👍

@dotCipher

dotCipher commented Apr 21, 2026

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Closing this PR after extensive investigation. The issue is not fixable at the OpenCode level.

Investigation Summary

We spent significant time debugging why xAI/Grok rejects tool schemas with additionalProperties: false when used via OpenRouter. Here's what we found:

Root Cause

The Vercel AI SDK intentionally adds additionalProperties: false to all object schemas during tool serialization (via addAdditionalPropertiesToJsonSchema in @ai-sdk/provider-utils). This is a deliberate design choice for strict JSON validation.

xAI's validator explicitly rejects additionalProperties: false in tool schemas, creating an incompatibility:

  • AI SDK: Adds it for strict validation (intentional)
  • xAI: Rejects it (their validator rule)

Why OpenCode Can't Fix This

  1. The AI SDK re-adds additionalProperties: false AFTER any sanitization we do in OpenCode
  2. The binary bundles all dependencies at build time, so runtime interceptors don't work
  3. The conflict exists at the AI SDK level, not OpenCode's code

Where This Needs To Be Fixed

  1. @openrouter/ai-sdk-provider — Most likely candidate; they translate between OpenAI format and xAI
  2. Vercel AI SDK — Could add provider-specific schema serialization options
  3. xAI — Could change their validator to accept additionalProperties: false

Workarounds

  • Use Grok without tools (tool_call: false in config)
  • Use a different provider (Claude, GPT-4, etc.)
  • File an issue with OpenRouter to add xAI-specific schema handling

1 similar comment
@dotCipher

dotCipher commented Apr 21, 2026

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Closing this PR after extensive investigation. The issue is not fixable at the OpenCode level.

Investigation Summary

We spent significant time debugging why xAI/Grok rejects tool schemas with additionalProperties: false when used via OpenRouter. Here's what we found:

Root Cause

The Vercel AI SDK intentionally adds additionalProperties: false to all object schemas during tool serialization (via addAdditionalPropertiesToJsonSchema in @ai-sdk/provider-utils). This is a deliberate design choice for strict JSON validation.

xAI's validator explicitly rejects additionalProperties: false in tool schemas, creating an incompatibility:

  • AI SDK: Adds it for strict validation (intentional)
  • xAI: Rejects it (their validator rule)

Why OpenCode Can't Fix This

  1. The AI SDK re-adds additionalProperties: false AFTER any sanitization we do in OpenCode
  2. The binary bundles all dependencies at build time, so runtime interceptors don't work
  3. The conflict exists at the AI SDK level, not OpenCode's code

Where This Needs To Be Fixed

  1. @openrouter/ai-sdk-provider — Most likely candidate; they translate between OpenAI format and xAI
  2. Vercel AI SDK — Could add provider-specific schema serialization options
  3. xAI — Could change their validator to accept additionalProperties: false

Workarounds

  • Use Grok without tools (tool_call: false in config)
  • Use a different provider (Claude, GPT-4, etc.)
  • File an issue with OpenRouter to add xAI-specific schema handling

@dotCipher dotCipher closed this Apr 21, 2026
@dotCipher

dotCipher commented Apr 21, 2026

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Investigation Summary

After extensive debugging, this issue is not fixable at the OpenCode level. Here's what we found:

Root Cause

The Vercel AI SDK intentionally adds additionalProperties: false to all object schemas during tool serialization via addAdditionalPropertiesToJsonSchema in @ai-sdk/provider-utils. This is a deliberate design choice for strict JSON validation.

xAI's validator explicitly rejects additionalProperties: false in tool schemas, creating an incompatibility:

  • AI SDK: Adds it for strict validation (intentional)
  • xAI: Rejects it (their validator rule)

Why OpenCode Can't Fix This

  1. The AI SDK re-adds additionalProperties: false AFTER any sanitization we do in OpenCode
  2. The binary bundles all dependencies at build time, so runtime interceptors don't work
  3. The conflict exists at the AI SDK level, not OpenCode's code

Where This Needs To Be Fixed

  1. @openrouter/ai-sdk-provider — Most likely candidate; they translate between OpenAI format and xAI
  2. Vercel AI SDK — Could add provider-specific schema serialization options
  3. xAI — Could change their validator to accept additionalProperties: false

Workarounds

  • Use Grok without tools (tool_call: false in config)
  • Use a different provider (Claude, GPT-4, etc.)
  • File an issue with OpenRouter to add xAI-specific schema handling in their provider package

@dotCipher dotCipher mentioned this pull request Apr 21, 2026
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OpenRouter xAI/Grok tool schemas fail when additionalProperties: false is emitted

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