Model Not Found and 400 Error Troubleshooting

Your Problem

When using Antigravity models, you may encounter the following errors:

Error Message	Typical Symptoms
Model not found	Indicates model doesn't exist, cannot make requests
Invalid JSON payload received. Unknown name "parameters"	400 error, tool calls fail
MCP server call errors	Specific MCP tools unavailable

These issues are usually related to configuration, MCP server compatibility, or plugin version.

Quick Diagnosis

Before diving deep, confirm the following:

macOS/Linux:

# Check plugin version
grep "opencode-antigravity-auth" ~/.config/opencode/opencode.json

# Check configuration file
cat ~/.config/opencode/antigravity.json | grep -E "(google|npm)"

Windows:

# Check plugin version
Get-Content "$env:USERPROFILE\.config\opencode\opencode.json" | Select-String "opencode-antigravity-auth"

# Check configuration file
Get-Content "$env:USERPROFILE\.config\opencode\antigravity.json" | Select-String "google|npm"

---

Problem 1: Model not found

Error symptom:

Model not found: antigravity-claude-sonnet-4-5

Cause: OpenCode's Google provider configuration is missing the npm field.

Solution:

In your ~/.config/opencode/opencode.json, add the npm field to the google provider:

{
  "provider": {
    "google": {
      "npm": "@ai-sdk/google",
      "models": { ... }
    }
  }
}

Verification steps:

1. Edit ~/.config/opencode/opencode.json
2. Save the file
3. Retry calling the model in OpenCode
4. Check if "Model not found" error still occurs

Tip

If you're unsure about the configuration file location, run:

opencode config path

---

Problem 2: 400 Error - Unknown name 'parameters'

Error symptom:

Invalid JSON payload received. Unknown name "parameters" at 'request.tools[0]'

What's this problem?

Gemini 3 models use strict protobuf validation, while Antigravity API requires tool definitions in a specific format:

// ❌ Incorrect format (will be rejected)
{
  "tools": [
    {
      "name": "my_tool",
      "parameters": { ... }  // ← This field is not accepted
    }
  ]
}

// ✅ Correct format
{
  "tools": [
    {
      "functionDeclarations": [
        {
          "name": "my_tool",
          "description": "...",
          "parameters": { ... }  // ← Inside functionDeclarations
        }
      ]
    }
  ]
}

The plugin automatically converts the format, but some MCP servers return Schemas containing incompatible fields (like const, $ref, $defs), causing cleanup failures.

Solution 1: Update to latest beta version

The latest beta version includes Schema cleanup fixes:

{
  "plugin": ["opencode-antigravity-auth@beta"]
}

macOS/Linux:

npm install -g opencode-antigravity-auth@beta

Windows:

npm install -g opencode-antigravity-auth@beta

Solution 2: Disable MCP servers one by one to diagnose

Some MCP servers return Schema formats that don't meet Antigravity requirements.

Steps:

1. Open ~/.config/opencode/opencode.json
2. Find mcpServers configuration
3. Disable all MCP servers (comment out or delete)
4. Retry calling the model
5. If successful, enable MCP servers one by one, testing after each
6. Once the problematic MCP server is identified, disable it or report the issue to that project's maintainer

Example configuration:

{
  "mcpServers": {
    // "filesystem": { ... },  ← Temporarily disabled
    // "github": { ... },       ← Temporarily disabled
    "brave-search": { ... }     ← Test this one first
  }
}

Solution 3: Add npm override

If the above methods don't work, force the use of @ai-sdk/google in the google provider configuration:

{
  "provider": {
    "google": {
      "npm": "@ai-sdk/google"
    }
  }
}

---

Problem 3: MCP servers causing tool call failures

Error symptoms:

• Specific tools unavailable (e.g., WebFetch, file operations)
• Error hints at Schema-related issues
• Other tools work normally

Cause: JSON Schema returned by MCP server contains fields not supported by Antigravity API.

Incompatible Schema Characteristics

The plugin automatically cleans the following incompatible features (source src/plugin/request-helpers.ts:24-37):

Feature	Conversion Method	Example
const	Convert to enum	{ const: "text" } → { enum: ["text"] }
$ref	Convert to description hint	{ $ref: "#/$defs/Foo" } → { type: "object", description: "See: Foo" }
$defs / definitions	Expand into schema	References no longer used
minLength / maxLength / pattern	Move to description	Add to description hint
additionalProperties	Move to description	Add to description hint

However, if Schema structure is too complex (like multi-level nested anyOf/oneOf), cleanup may fail.

Diagnosis Process

# Enable debug logs
export OPENCODE_ANTIGRAVITY_DEBUG=1  # macOS/Linux
$env:OPENCODE_ANTIGRAVITY_DEBUG=1     # Windows PowerShell

# Restart OpenCode

# View Schema conversion errors in logs
tail -f ~/.config/opencode/antigravity-logs/*.log

Keywords to look for in logs:

• cleanJSONSchemaForAntigravity
• Failed to clean schema
• Unsupported keyword
• anyOf/oneOf flattening failed

Reporting Issues

If you've identified a specific MCP server causing the problem, please submit a GitHub issue, including:

1. MCP server name and version
2. Complete error logs (from ~/.config/opencode/antigravity-logs/)
3. Example of tool triggering the problem
4. Plugin version (run opencode --version)

---

Common Pitfalls

Plugin Loading Order

If you're using both opencode-antigravity-auth and @tarquinen/opencode-dcp, place the Antigravity Auth plugin first:

{
  "plugin": [
    "opencode-antigravity-auth@latest",  ← Must come before DCP
    "@tarquinen/opencode-dcp@latest"
  ]
}

DCP creates synthetic assistant messages lacking thought blocks, which may cause signature verification errors.

Configuration Key Name Error

Make sure to use plugin (singular), not plugins (plural):

// ❌ Incorrect
{
  "plugins": ["opencode-antigravity-auth@beta"]
}

// ✅ Correct
{
  "plugin": ["opencode-antigravity-auth@beta"]
}

---

When to Seek Help

If the problem persists after trying all the above methods:

Check log files:

cat ~/.config/opencode/antigravity-logs/latest.log

Reset account (clear all state):

rm ~/.config/opencode/antigravity-accounts.json
opencode auth login

Submit GitHub issue, including:

• Complete error message
• Plugin version (opencode --version)
• ~/.config/opencode/antigravity.json configuration (remove sensitive info like refreshToken)
• Debug logs (~/.config/opencode/antigravity-logs/latest.log)

---

Related Courses

• Quick Installation Guide - Basic configuration
• Plugin Compatibility - Troubleshooting other plugin conflicts
• Debug Logging - Enable verbose logging

---

Appendix: Source Code Reference

Click to view source code locations

Last updated: 2026-01-23

Feature	File Path	Lines
JSON Schema cleanup main function	src/plugin/request-helpers.ts	658-685
Convert const to enum	src/plugin/request-helpers.ts	86-104
Convert $ref to hints	src/plugin/request-helpers.ts	55-80
Flatten anyOf/oneOf	src/plugin/request-helpers.ts	368-453
Gemini tool format conversion	src/plugin/transform/gemini.ts	425-517

Key Constants:

• UNSUPPORTED_KEYWORDS: Schema keywords removed (request-helpers.ts:33-37)
• UNSUPPORTED_CONSTRAINTS: Constraints moved to description (request-helpers.ts:24-28)

Key Functions:

• cleanJSONSchemaForAntigravity(schema): Cleans incompatible JSON Schema
• convertConstToEnum(schema): Converts const to enum
• convertRefsToHints(schema): Converts $ref to description hints
• flattenAnyOfOneOf(schema): Flattens anyOf/oneOf structures