question tool fails with Gemini models (SchemaError: Missing key at ["questions"] due to argument flattening) #35105

Description

Description

When using the built-in question tool with Gemini-powered models (e.g., gemini-3.5-flash), the tool execution fails with a schema validation error.

The issue is that the model's tool-calling arguments are being flattened/serialized into dot-bracket notation keys (like questions[0].header) instead of being maintained or re-assembled as a valid nested JSON array of objects.

This works perfectly on Anthropic Claude models (which correctly output a nested questions array), but consistently fails on Gemini.

Error Output

The question tool was called with invalid arguments: SchemaError(Missing key
  at ["questions"]).
Please rewrite the input so it satisfies the expected schema.

Observed Serialization (Gemini)

The adapter/serialiser attempts to invoke the tool with parameters structured like this:

{
  "questions[0].header": "Favorite Food",
  "questions[0].multiple": false,
  "questions[0].options[0].description": "Delicious, cheesy, and versatile",
  "questions[0].options[0].label": "Pizza",
  "questions[0].question": "What is your go-to comfort food?"
}

This fails schema validation because the expected root questions array key is missing.

Expected Serialization (Claude)

{
  "questions": [
    {
      "header": "Favorite Food",
      "multiple": false,
      "options": [
        {
          "description": "Delicious, cheesy, and versatile",
          "label": "Pizza"
        }
      ],
      "question": "What is your go-to comfort food?"
    }
  ]
}

Suggested Fix

The Gemini provider adapter layer in opencode should detect and parse bracket/dot-notation parameters back into nested arrays/objects (e.g., un-flattening questions[0].header into questions: [{ header: ... }]) before running the schema validator.

Plugins

none

OpenCode version

1.17.13

Steps to reproduce

1. select any model from the gemini class
2. prompt to ask any question using the question tool

Screenshot and/or share link

Operating System

Ubuntu 24.04

Terminal

No response