OpenCode 2: Gemini requests fail with 400 Unknown name "exclusiveMinimum" when a submitted tool schema has an exclusive bound #36

What happens

On OpenCode 2 with v3.0.2, a request to an Antigravity Gemini model fails when any of its submitted tool declarations still has exclusiveMinimum. OpenCode 2's built-in webfetch tool is one such case. Its timeout parameter is Schema.isGreaterThan(0) (packages/core/src/tool/plugin/webfetch.ts), which becomes "exclusiveMinimum": 0. Ordinary sessions include that tool, so their Gemini requests fail.

The endpoint rejects the request:

Invalid JSON payload received. Unknown name "exclusiveMinimum" at
'request.tools[0].function_declarations[33].parameters.properties[2].value': Cannot find field.
Status: 400
Requested Model: antigravity-gemini-3.8-flash

Cause

applyGeminiTransforms (packages/core/src/transform/gemini.ts) moves numeric JSON-Schema keywords into the description only for GPT-OSS models:

const result = normalizeGeminiTools(payload, {
  moveNumericConstraintsToDescription: model
    .toLowerCase()
    .startsWith('gpt-oss-'),
})

For Gemini models, the numeric keywords stay in the schema. toGeminiSchema strips some unsupported keywords, but none of the numeric ones. The cleaner that does remove exclusiveMinimum, cleanJSONSchemaForAntigravity in packages/opencode/src/plugin/request-helpers.ts, runs only for Claude models.

Reproduction

1. Run OpenCode 2.0.28 with @cortexkit/opencode-antigravity-auth 3.0.2 as its plugin, with one Antigravity account.
2. Send a prompt to google/antigravity-gemini-3.8-flash in a session whose tools include the built-in webfetch.
3. The request fails with the 400 above.

A live retest succeeded with moveNumericConstraintsToDescription: true for all models handled by applyGeminiTransforms, including a turn that made a bash tool call. The constraint then becomes a hint appended to the description: "Optional timeout in seconds (maximum: 120) (exclusiveMinimum: 0, maximum: 120)".

Suggested fix

Move numeric constraints into descriptions for Gemini models as well as GPT-OSS. If that is too broad, at least strip exclusiveMinimum, which the endpoint rejects outright. exclusiveMaximum also passes through untouched for Gemini, and the Claude cleaner treats it as unsupported. I have not seen the endpoint reject it, but it should be handled the same way.

A unit test can call applyGeminiTransforms with model: 'gemini-3.8-flash' and a tool whose property has exclusiveMinimum, then assert that the keyword is gone from the declaration.