Plan & Build Modes

Why Two Modes?

The success of building with AI is directly proportional to the quality of planning and prompting that goes into the project. But prompt engineering is evolving rapidly, and learning how to effectively communicate with AI systems takes time and practice.

That's why Memex introduces Plan Mode—not just as another planning tool, but as an experienced technical product manager that guides you through the critical thinking and decision-making that sets up Build Mode for success.

Plan Mode: Your Strategic Partner

Plan Mode is designed to solve the "garbage in, garbage out" problem that affects all AI development tools. It acts as an experienced technical product manager who will:

• Guide you toward choices that set you up for success

• Help you think through trade-offs of different technical and business decisions

• Adopt best practices like scoping down to an MVP before expanding

• Steer you toward solutions that get you to value quickly

• Push back on your ideas when appropriate to help you think through implications

What Makes Plan Mode Different

While other AI tools have planning features, Memex's Plan Mode is uniquely opinionated toward solutions that deliver value fast. It understands that the goal isn't just to create a plan, but to create a plan that leads to successful implementation.

Plan Mode will help you consider factors that non-technical users often don't think about upfront:

• Sharing and collaboration: Do you plan to share what you build with others?

• Design requirements: How important is visual design for your use case?

• Scalability considerations: Will this need to handle many users or large amounts of data?

• Integration needs: Does this need to connect with existing tools or services?

• Deployment strategy: Where and how will this run?

How Plan Mode Works

Plan Mode follows a structured approach to requirements gathering:

1. Discovery Phase Plan Mode asks probing questions to understand your true needs:

Plan Mode: That's an interesting idea for a project management tool. Let me ask a few questions to help create the best plan:

1. Is this for personal use, team use, or do you plan to share it more broadly?
2. What specific pain points are you trying to solve that existing tools don't address?
3. Do you have any design preferences or branding requirements?
4. How technically complex are you comfortable with for the initial version?

2. Requirement Clarification Based on your answers, Plan Mode digs deeper into areas that need clarification:

Plan Mode: Since you mentioned this is for team use, I want to make sure we think through the collaboration aspects:

- How will team members access this? (web app, desktop app, shared file, etc.)
- Do you need user accounts and permissions, or is simple shared access sufficient?
- What's the most important feature for initial adoption by your team?

3. MVP Scoping Plan Mode helps you identify the smallest version that delivers real value:

Plan Mode: Based on our discussion, I recommend we start with an MVP that focuses on:

1. Core task tracking with simple status updates
2. Team visibility into who's working on what
3. Basic progress reporting

We can add advanced features like time tracking, detailed analytics, and integrations once the core workflow is proven valuable. Does this sound like the right starting point?

4. Technical Strategy Plan Mode creates a development approach optimized for Build Mode success:

Plan Mode: For the technical implementation, I recommend:

1. Start with a simple web application that can be shared easily
2. Use a lightweight database for data persistence  
3. Focus on mobile-friendly design since teams often check status on phones
4. Plan for simple deployment so you can share with the team quickly

I'll create a structured plan that Build Mode can follow step by step.

The Plan Document

Plan Mode generates a structured plan.md file that includes:

• Project Overview: Clear description of what you're building and why

• User Requirements: Who will use this and what they need

• Technical Approach: Recommended technology stack and architecture

• Development Phases: Step-by-step implementation plan

• Success Criteria: How you'll know when each phase is complete

This document becomes the foundation for Build Mode to work from, ensuring consistent direction throughout development.

Once Plan Mode has worked through your requirements and created a structured plan, it will ask if you're ready to start building or if you'd like to continue refining the idea. If you're ready to proceed, you can choose to start building immediately in the same conversation, or begin fresh in a new conversation with your plan as the foundation.

Build Mode: Your Implementation Partner

Build Mode takes the structured plan and turns it into working software. It's designed to work seamlessly with the plans created in Plan Mode, but it's also flexible enough to handle ad-hoc requests and modifications.

Build Mode Capabilities

Code Development

• Writes code in any programming language

• Follows the architecture and patterns outlined in your plan

• Implements features incrementally based on plan phases

Environment Management

• Sets up development environments and dependencies

• Manages virtual environments and package installations

• Handles complex configuration and setup tasks

File Operations

• Creates and manages all project files

• Organizes code according to best practices

• Maintains project documentation as development progresses

Testing and Debugging

• Runs applications to verify functionality

• Debugs issues and implements fixes

• Tests features to ensure they work as specified

Version Control

• Initializes git repositories with appropriate .gitignore files

• Commits progress at logical milestones

• Maintains clear commit history for project tracking

Working with Your Plan

When Build Mode receives a plan from Plan Mode, it understands how to:

• Follow the implementation sequence outlined in the plan

• Make technical decisions that align with the strategic choices in the plan

• Stay focused on the current phase while keeping future phases in mind

• Adapt the plan when technical realities require adjustments

Beyond Planned Development

Build Mode is also excellent for unplanned work:

Add a dark mode toggle to this application and make sure it persists user preference.

This API is returning different data than expected. Debug the issue and fix the data processing.

Convert this Python script into a web application with a simple interface.

Working Across Modes

Starting with Plan Mode (Recommended)

While you can start with either mode, we recommend beginning new projects in Plan Mode for the best results. Plan Mode is helpful in the majority of scenarios because it:

• Helps you define clear requirements even from vague ideas

• Ensures you're building something valuable from the start

• Provides guidance on technical architecture decisions

• Helps you avoid common pitfalls in project planning

Example workflow:

1. Plan Mode: Define requirements and create development plan

2. Switch to Build Mode: Implement Phase 1 of the plan

3. Back to Plan Mode: Evaluate results and plan Phase 2

4. Build Mode: Continue implementation

Starting with Build Mode

Jump directly into Build Mode when you:

• Have clear, specific requirements

• Are working on existing projects

• Need to make targeted changes or fixes

• Want to experiment with a quick prototype

Switching Between Modes

You can switch modes at any time during a conversation using the toggle below the conversation input. Simply click to switch between Plan and Build modes—no need to ask Memex to make the change.

When switching from Plan to Build: After completing your planning phase, toggle to Build Mode to begin implementation.

When switching from Build to Plan: If you need strategic guidance during development, toggle to Plan Mode for architectural decisions or feature planning.

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Best Practices for Each Mode

Plan Mode Best Practices

Be open to questions and pushback:

I want to build a comprehensive CRM system with every feature I can think of.

Let Plan Mode guide you toward a more focused, achievable scope.

Share context about your situation:

I'm a solo consultant who needs to track about 50 clients and their projects. I currently use spreadsheets but they're getting unwieldy.

Be honest about your technical comfort level:

I understand basic technical concepts but I've never deployed a web application before.

Build Mode Best Practices

Reference the plan:

Following our plan, let's implement the basic task creation and status tracking functionality first.

Work incrementally:

Let's get the core functionality working before adding the advanced filtering features.

Test and verify:

Run the application and test this phase thoroughly before moving to the next one.

Save progress:

This phase is working well. Let's commit our progress and update the README with what we've accomplished.

Advanced Mode Usage

Context Continuity

Both modes maintain awareness of your project history:

• Plan Mode considers previous plans and decisions

• Build Mode remembers the technical implementation details

• Context flows naturally between modes

Custom Instructions for Modes

You can set mode-specific preferences in your Custom Instructions:

In Plan Mode: Always consider mobile-first design and simple deployment options.
In Build Mode: Prioritize code readability and include comprehensive error handling.

Project Rules Integration

Both modes respect project-specific rules stored in your .memex/context.md file, ensuring consistent behavior across conversations and modes.

Plan and Build Modes work together to provide the complete development experience—from initial concept to working software. Plan Mode ensures you're building the right thing, while Build Mode ensures you build it right.