Overview
Coding agents tend to plan horizontally. A typical horizontal plan might be:
- Phase 1: implement all database changes.
- Phase 2: implement all API changes.
- Phase 3: implement all front-end changes.
The problem is delayed feedback. The database work cannot be validated as part of a working user flow until the API and interface are also present. The agent may complete several phases before discovering that the layers do not integrate correctly.
A vertical slice crosses the layers required to produce one observable result. A first gamification slice might include:
- The minimum schema change.
- A focused service that awards points.
- The route or event integration required to trigger it.
- A minimal dashboard representation.
- Tests that exercise the meaningful behavior.
This is a tracer-bullet approach. A tracer bullet makes the path visible while work is still in progress. In software, the equivalent is a thin end-to-end path that immediately shows whether the layers connect and whether the design is viable.
The issues are placed on a Kanban-style board with explicit blocking relationships. One issue may be blocked by nothing. Two later issues may both depend on it but not on each other. A final issue may depend on both. This structure is a directed acyclic graph. The graph naturally creates execution phases without forcing every task into a single numbered list.
A sequential multi-phase plan is effectively one loop that one agent must follow. A dependency graph exposes independent work. Once an upstream issue is complete, multiple unblocked issues can be assigned to separate agents.