Implementation Approach

Implementation Strategy Selection Framework (Meta-cognitive Approach)

Meta-cognitive Strategy Selection Process [MANDATORY]

Phase 1: Comprehensive Current State Analysis

Core Question: "What does the existing implementation look like?"

Analysis Framework

Architecture Analysis: Responsibility separation, data flow, dependencies, technical debt
Implementation Quality Assessment: Code quality, test coverage, performance, security
Historical Context Understanding: Current form rationale, past decision validity, constraint changes, requirement evolution

Meta-cognitive Question List [MANDATORY CHECKPOINTS]

• What is the true responsibility of this implementation?
• Which parts are business essence and which derive from technical constraints?
• What dependencies or implicit preconditions are unclear from the code?
• What benefits and constraints does the current design bring?

ENFORCEMENT: CANNOT proceed to Phase 2 without answering all questions

Phase 2: Strategy Exploration and Creation

Core Question: "When determining before to after, what implementation patterns or strategies should be referenced?"

Strategy Discovery Process

Research and Exploration: Tech stack examples, similar projects, OSS references, literature/blogs
Creative Thinking: Strategy combinations, constraint-based design, phase division, extension point design

Reference Strategy Patterns (Creative Combinations Encouraged)

Legacy Handling Strategies:

• Strangler Pattern: Gradual migration through phased replacement
• Facade Pattern: Complexity hiding through unified interface
• Adapter Pattern: Bridge with existing systems

New Development Strategies:

• Feature-driven Development: Vertical implementation prioritizing user value
• Foundation-driven Development: Foundation-first construction prioritizing stability
• Risk-driven Development: Prioritize addressing maximum risk elements

Integration/Migration Strategies:

• Proxy Pattern: Transparent feature extension
• Decorator Pattern: Phased enhancement of existing features
• Bridge Pattern: Flexibility through abstraction

IMPORTANT: The optimal solution is discovered through creative thinking according to each project's context. EVALUATE multiple strategy combinations before selecting.

Phase 3: Risk Assessment and Control [MANDATORY]

Core Question: "What risks arise when applying this to existing implementation, and what's the best way to control them?"

Risk Analysis Matrix

Technical Risks: System impact, data consistency, performance degradation, integration complexity
Operational Risks: Service availability, deployment downtime, process changes, rollback procedures
Project Risks: Schedule delays, learning costs, quality achievement, team coordination

Risk Control Strategies

Preventive Measures: Phased migration, parallel operation verification, integration/regression tests, monitoring setup
Incident Response: Rollback procedures, log/metrics preparation, communication system, service continuation procedures

Phase 4: Constraint Compatibility Verification

Core Question: "What are this project's constraints?"

Constraint Checklist

Technical Constraints: Library compatibility, resource capacity, mandatory requirements, numerical targets
Temporal Constraints: Deadlines/priorities, dependencies, milestones, learning periods
Resource Constraints: Team/skills, work hours/systems, budget, external contracts
Business Constraints: Market launch timing, customer impact, regulatory compliance

Phase 5: Implementation Approach Decision

Select optimal solution from basic implementation approaches (creative combinations encouraged):

Vertical Slice (Feature-driven)

Characteristics: Vertical implementation across all layers by feature unit Application Conditions: Low inter-feature dependencies, output in user-usable form, changes needed across all architecture layers Verification Method: End-user value delivery at each feature completion

Horizontal Slice (Foundation-driven)

Characteristics: Phased construction by architecture layer Application Conditions: Foundation system stability important, multiple features depend on common foundation, layer-by-layer verification effective Verification Method: Integrated operation verification when all foundation layers complete

Hybrid (Creative Combination)

Characteristics: Flexible combination according to project characteristics Application Conditions: Unclear requirements, need to change approach per phase, transition from prototyping to full implementation Verification Method: Verify at appropriate L1/L2/L3 levels according to each phase's goals

Phase 6: Decision Rationale Documentation

Design Doc Documentation: Clearly specify implementation strategy selection reasons and rationale.

Verification Level Definitions

Priority for completion verification of each task:

• L1: Functional Operation Verification - Operates as end-user feature (e.g., search executable)
• L2: Test Operation Verification - New tests added and passing
• L3: Build Success Verification - Code builds/runs without errors

Priority: L1 > L2 > L3 in order of verifiability importance

Integration Point Definitions

Define integration points according to selected strategy:

• Strangler-based: When switching between old and new systems for each feature
• Feature-driven: When users can actually use the feature
• Foundation-driven: When all architecture layers are ready and E2E tests pass
• Hybrid: When individual goals defined for each phase are achieved

Anti-patterns [MANDATORY to detect]

• Pattern Fixation: EVALUATE unique combinations instead of selecting only listed strategies
• Insufficient Analysis: MUST complete Phase 1 analysis framework before strategy selection
• Risk Neglect: MUST complete Phase 3 risk analysis matrix before implementation
• Constraint Ignorance: MUST check Phase 4 constraint checklist before deciding strategy
• Rationale Omission: MUST use Phase 6 documentation template when selecting strategy

ENFORCEMENT: Detecting ANY anti-pattern requires IMMEDIATE correction before proceeding

Guidelines for Meta-cognitive Execution

1. Leverage Known Patterns: Use as starting point, then EVALUATE creative combinations
2. Active Research: Research implementation examples from similar tech stacks
3. Apply 5 Whys: Pursue root causes to grasp essence
4. Multi-perspective Evaluation: EVALUATE comprehensively from each Phase 1-4 perspective
5. Creative Thinking: EVALUATE sequential application of multiple strategies and designs leveraging project-specific constraints
6. Clarify Decision Rationale: Strategy selection rationale MUST be explicit in design documents

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: shinpr
• Source: shinpr/codex-workflows
• License: MIT

Install and usage instructions live in the source repository linked above.