🐛 MCP Tools Failing: TypeError on output.output.toLowerCase() in v1.1.50 #13091

Bug Description

All MCP (Model Context Protocol) tool calls are failing with a TypeError in OpenCode v1.1.50. This affects all MCP servers including Laravel Boost, Exa, Context7, and other MCP integrations.

Error Message:

TypeError: undefined is not an object (evaluating 'output.output.toLowerCase')

Environment

• OpenCode Version: 1.1.50 (latest stable)
• Platform: macOS (darwin-arm64)
• Installation Method: Homebrew
• Node Version: v24.1.0

Steps to Reproduce

1. Install OpenCode v1.1.50 via Homebrew
2. Configure any MCP server (e.g., Laravel Boost MCP)
3. Attempt to call any MCP tool

Example with Laravel Boost:

laravel-boost_search-docs({
  queries: ["migration", "database migration"]
})

Example with Exa:

exa_web_search_exa({
  query: "OpenCode documentation",
  numResults: 5
})

Expected Behavior

MCP tools should execute successfully and return results.

Actual Behavior

All MCP tool calls fail immediately with:

TypeError: undefined is not an object (evaluating 'output.output.toLowerCase')

Root Cause Analysis

The client-side MCP response parser expects a nested structure:

response.output.output.toLowerCase()

However, MCP servers are returning a flat structure:

response.output  // No nested .output property

This is confirmed by direct tool execution working correctly:

# Direct execution works (bypasses OpenCode client parser)
php artisan boost:execute-tool 'Laravel\Boost\Mcp\Tools\SearchDocs' 'base64params'
# Returns: {"isError":false,"content":[{"type":"text","text":"..."}]}

The backend MCP server responses are correct - the bug is in OpenCode's client-side parsing layer.

Affected Components

• ✅ Laravel Boost MCP - All tools fail
• ✅ Exa MCP - All tools fail
• ✅ Context7 MCP - All tools fail
• ✅ grep.app MCP - All tools fail
• ✅ All other MCP integrations - Likely affected

Workaround

For Laravel Boost users, direct tool execution via bash:

php artisan boost:execute-tool 'ToolClassName' 'base64_encoded_params'

Additional Context

• MCP server logs show successful tool execution
• Error occurs during response parsing in OpenCode client
• Binary is compiled (Mach-O), cannot patch directly
• Logs location: ~/.local/share/opencode/log/

Verification

Confirmed with:

opencode --version  # 1.1.50
opencode debug config  # Shows MCP servers configured correctly

MCP servers initialize successfully but all tool invocations fail at the response parsing stage.

Suggested Fix

Update MCP response parser to handle flat output structure:

// Current (broken)
output.output.toLowerCase()

// Suggested fix
(output?.output || output)?.toLowerCase?.()

Or properly validate MCP response schema before accessing nested properties.