Dedicated Coder Agent

A focused sub-agent for code implementation, using a three-phase workflow with model switching.

Architecture

• Phase 1 (Opus): Read task, explore codebase, write implementation plan
• Phase 2 (Codex): Implement the plan, run tests, create PR
• Phase 3 (Opus, conditional): Review if plan drift, excessive retries, or high complexity

Routing Gate

Trivial tasks (typos, single-line fixes) skip Phase 1 entirely. The routing decision is placed at the top of AGENTS.md in the primacy zone so the model hits it before absorbing phase details.

Definition Files

• AGENTS.md — workflow, routing, rules
• SOUL.md — personality, standards
• TOOLS.md — git patterns, cgc, model switching

Key Design Decisions

• Instruction ordering: "Every Session" and routing gate come before phase details — primacy bias means the model processes routing before it's primed to execute the full workflow
• Phase 3 triggers are explicit: plan drift, >2 fix cycles, >5 files changed — removes ambiguity about when review is needed
• Tool lockdown at config level: models ignore prompt-level tool restrictions, so denied tools must be in the agent config