Typical of Replit to launch quite an important feature that will affect our day to day workflow, and not bother announcing it to clients.
But anyway, I asked Agent to explain the new modes, and its outline is shown below. And based on what Agent told me, I have two initial questions - I would love to discuss these with you other builders:
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You’re only charged when Agent implements approved changes. You’re not charged during planning/proposal stages. Really!!?? So we can have massive planning chats with agent which incur costs upstream with Claude, and Replit really won’t charge us???
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Based on the documentation, Plan mode is NOT 100% guaranteed to prevent code changes. Hhmmm!! Well this makes it an utter waster of time and too dangerous to use.
Steve: what is the difference between the new Agent tool Build and Plan modes?
Based on Replit’s documentation, here are the key differences between Agent’s Build and Plan modes:
Plan Mode
- Outline Creation: Agent creates a detailed development plan without executing code
- Review Process: You can review and approve the proposed approach before implementation
- Strategy Discussion: Allows you to guide the AI’s direction and make adjustments to the plan
- No Code Changes: Only planning and outlining, no actual file modifications
Build Mode
- Direct Implementation: Agent immediately executes the plan and writes code
- Active Development: Makes real changes to your codebase and files
- Immediate Results: You see working code and features right away
- Full Execution: Handles the complete development process from start to finish
The Iterative Process
The two modes work together in an iterative workflow:
- Plan → Agent proposes what it will build
- Review → You approve, modify, or reject the plan
- Build → Agent implements the approved plan
- Iterate → Repeat as needed for refinements
This approach gives you more control over the development process, especially for complex projects where you want to ensure the AI understands your requirements before making changes to your codebase.
The newer Agent versions (v2 with Claude Sonnet 4.0) also include enhanced features like web search, image generation, and dynamic intelligence modes for even more powerful development capabilities.
Steve: but what if I am in the wrong mode for what I am asking in my prompts?
Based on the documentation search, there isn’t specific information about switching between Build and Plan modes when you’re in the wrong mode. However, here’s what typically happens in practice: ## Agent’s Adaptive Behavior Agent is generally intelligent about mode interpretation: - If you ask for planning in Build mode, Agent will often still provide a plan before implementing - If you ask for immediate implementation in Plan mode, Agent may suggest switching to Build mode - The AI can usually understand your intent regardless of the current mode setting ## What to Do if You’re in the Wrong Mode Simple approach: 1. Just ask clearly - Say “I need you to plan this first” or “Please build this now” 2. Agent will adapt - It typically recognizes when your request doesn’t match the current mode 3. Mode switching - You can manually switch modes in the Agent interface if needed Example scenarios: - In Build mode but want planning: Say “Before building this, can you outline your approach?” - In Plan mode but want immediate action: Say “Skip the planning, please implement this directly” ## Best Practices Clear communication works best: - Be explicit about what you want: “Plan this feature” vs “Build this feature” - Agent is designed to be flexible and understand context - If you notice you’re getting the wrong type of response, simply clarify what you need The Agent system is built to be forgiving and adaptive, so being in the “wrong” mode typically isn’t a major issue - just communicate clearly what type of response you’re looking for.
Steve: if I am in plan mode, is agent 100% guaranteed to not change any code or files?
Based on the documentation, Plan mode is NOT 100% guaranteed to prevent code changes. Here’s what the documentation reveals:
The Safety Model
Plan mode provides review capability:
- Agent creates a plan that you can review and approve before implementation
- The safety comes from the review process, not absolute prevention
- You have control over modifications through the approval workflow
No Absolute Guarantee
The documentation doesn’t state that Plan mode completely prevents file changes. Instead, it emphasizes:
Safety through review:
- Plans are presented for your approval first
- You control when implementation happens
- The safety mechanism is human oversight, not technical restriction
Rollback as backup:
- If unwanted changes occur, you can use rollback features
- Rollback restores code, AI context, and connected databases
- This suggests changes can happen, but are reversible
Pricing Clues
Important detail:
- You’re only charged when Agent implements approved changes
- You’re not charged during planning/proposal stages
- This suggests Plan mode typically doesn’t implement, but isn’t technically prevented
Recommendation
For absolute safety, consider:
- Using version control commits before Agent sessions
- Taking manual backups of critical files
- Treating Plan mode as “review first” rather than “never change”
The system is designed for safety through human oversight rather than technical restrictions, so while Plan mode is much safer, it’s not a 100% guarantee against any file modifications.
