gemini-cli/plans/TASK-06.md

TASK-06: External Agent Definitions and "Polyfill" Support

Objective

Introduce a new external agent kind to support integrating and "polyfilling" competitor agents like Claude Code and Codex into Gemini CLI teams.

Implementation Details

1. Type Definitions (packages/core/src/agents/types.ts)

• Add ExternalAgentDefinition to the AgentDefinition union.
• Include fields for provider (e.g., 'claude-code', 'codex') and providerOptions.

  export interface ExternalAgentDefinition extends BaseAgentDefinition {
    kind: 'external';
    provider: string;
    // Allow for provider-specific configuration
    providerConfig?: Record<string, unknown>;
  }
  

2. External Agent Invocation (packages/core/src/agents/external-invocation.ts)

• Implement ExternalAgentInvocation class.
• The Polyfill Logic:
  • Use the system's configured default model to "polyfill" the external agent.
  • Apply a "personality overlay" to the system prompt based on the provider.
  • Example (Claude Code): Prepend instructions to adopt the specific style, tool usage patterns, and "persona" of a high-performance, concise coding assistant.
  • Example (Codex): Prepend instructions to act as a specialized code generation model.
  • Ensure the overlay is model-agnostic and relies on the providerConfig for behavior tuning.

3. Tool Wrapping (packages/core/src/agents/subagent-tool-wrapper.ts)

• Update createInvocation to recognize kind === 'external' and return an ExternalAgentInvocation.

Verification

• Unit tests for ExternalAgentInvocation ensuring provider-specific prompts are applied.
• Manual verification by creating an agent with kind: external and provider: claude-code.