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For information about project and personal configuration locations, see the Project vs Personal Config page.
The firebender.json file must be located in the project root directory for project-wide configuration, or in ~/.firebender/firebender.json for personal configuration.

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Fields

All high-level fields in the configuration are optional.

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ignore

Type: string[]? Array of glob patterns for files that Firebender should not analyze without explicit permission. Example: 
{
  "ignore": [
    "**/secrets.properties",
    "**/.env*",
    "private/**"
  ]
}
For details and examples, see Ignore Files.

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mcpServers

Type: Object<string, ServerConfig>? Configure Model Context Protocol (MCP) servers to provide custom tools for Firebender Agent.

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mcpServers.{serverName}

  • mcpServers.{serverName}.command: string? - The command to execute for the MCP server (required if url is not provided)
  • mcpServers.{serverName}.url: string? - The URL for HTTP-based MCP servers (required if command is not provided)
  • mcpServers.{serverName}.args: string[]? - Array of arguments to pass to the command
  • mcpServers.{serverName}.env: Object<string, string>? - Environment variables to set for the MCP server
  • mcpServers.{serverName}.headers: Object<string, string>? - HTTP headers for URL-based servers
Example: 
{
  "mcpServers": {
    "brave-search": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-brave-search"],
      "env": {"BRAVE_API_KEY": "YOUR_API_KEY"}
    },
    "weather": {
      "command": "npx",
      "args": ["-y", "@h1deya/mcp-server-weather"]
    },
    "api-server": {
      "url": "http://localhost:3000/mcp",
      "headers": {"Authorization": "Bearer YOUR_TOKEN"}
    }
  }
}
Firebender follows the same syntax as Model Context Protocol. For details and examples, see MCP.

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mcpEnvFile

Type: string? Optional path to a file containing environment variables for MCP servers. Can be either a full path or a relative path from the project root. Example: 
{
  "mcpEnvFile": ".env.mcp"
}

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rules

Type: (string | RuleConfig)[]? Define guidelines for Firebender to follow when generating code. Can contain both global rules (strings) and path-specific rules (objects).
  • rules[i]: string - A rule that applies to all files
  • rules[i].filePathMatches: string | string[]? - Optional glob pattern(s) to match file paths for specific rules. Can be a single pattern or an array of patterns.
  • rules[i].rules: string[] - Array of rules to apply only to matching files
  • rules[i].rulesPaths: string | string[] - Path(s) to files containing additional rules. Can be either a single path or an array of paths. Paths can be absolute or relative to the project root.
Example: 
{
  "rules": [
    "Follow Material Design 3 guidelines",
    "Use Kotlin coroutines for async operations",
    {
      "filePathMatches": "**/*Test.kt",
      "rules": ["Use Kotest BDD style", "Prefer property-based testing"],
      "rulesPaths": "test-rules.txt"
    },
    {
      "filePathMatches": ["**/*.kt", "**/*.kts"],
      "rulesPaths": ["/absolute/path/to/rules.txt", "relative/path/to/more-rules.txt"]
    }
  ]
}
For details and examples, see Rules for AI.

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commands

Type: CommandConfig[]? Define custom commands that can be executed through Firebender’s interface. Commands are markdown files containing prompts or instructions for the AI.

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CommandConfig

  • name: string - The name of the command as it appears in the UI
  • path: string - Path to the command file. Supports ~ expansion for home directory, absolute paths, and relative paths (relative to project root for project config, ~/.firebender for personal config)
Example: 
{
  "commands": [
    {
      "name": "Generate Firebender Rules",
      "path": "./prompts/generate-rules.md"
    },
    {
      "name": "Write Commit Message",
      "path": "~/firebender-commands/commit-message.md"
    },
    {
      "name": "Code Review",
      "path": "/home/user/.firebender/commands/code-review.md"
    }
  ]
}
For details and examples, see Commands.

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agents

Type: string[]? Array of paths to agent configuration files. Custom agent modes appear in the mode picker alongside built-in Auto, Read, and Write modes. Each agent mode can have specialized behavior, tools, and models. Paths support ~ expansion for home directory, absolute paths, and relative paths (relative to project root for project config, ~/.firebender for personal config). Example: 
{
  "agents": [
    ".firebender/agents/code-reviewer.md",
    "~/firebender-agents/test-writer.md",
    "/absolute/path/to/agent.md"
  ]
}
For details and examples, see Extending Agent Modes.

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subagents

Type: string[]? Array of paths to subagent configuration files. Subagents are specialized AI assistants that can be invoked to handle specific types of tasks using their own context window and custom system prompts. Paths support ~ expansion for home directory, absolute paths, and relative paths (relative to project root for project config, ~/.firebender for personal config). Example: 
{
  "subagents": [
    ".firebender/subagents/code-reviewer.md",
    "~/firebender-subagents/test-generator.md",
    "/absolute/path/to/subagent.md"
  ]
}
For details and examples, see Subagents.