Antigravity Planning Mode vs Fast Mode: Deep Comparison and When to Use Each

One of Antigravity's most powerful features is the ability to switch between Planning Mode and Fast Mode—two distinct execution approaches that fundamentally change how you work with the platform. Understanding when to use each can transform your development speed and project outcomes.

Planning Mode: The Deliberate Approach

Planning Mode is Antigravity's most comprehensive workflow. It creates an interactive environment similar to Google Docs, where you can review, comment on, and refine an AI-generated plan before actual execution begins.

Artifacts: The Virtual Deliverables

At the heart of Planning Mode are Artifacts—preview objects that represent what the AI intends to create. These include:

• Task Lists: Auto-generated breakdowns with prioritization
• Implementation Plans: Step-by-step execution strategies with decision points
• Architecture Diagrams: Visual representations of system design and data flow
• Screenshots: UI mockups and component previews

Unlike traditional code editors, Artifacts live in a collaborative space. You can comment directly on them, ask for changes, and watch the AI refine its approach—much like commenting on a shared document before final approval.

The Planning Mode Workflow

1. State your intent: Be clear about what you want to build or change
2. AI proposes a plan: Task decomposition, deliverable previews, time estimates
3. Review and provide feedback: Comment on Artifacts, ask questions, suggest changes
4. AI iterates: The plan is refined based on your input
5. Execute with confidence: Once approved, implementation begins

This deliberate pace pays dividends on complex projects where a wrong decision early on cascades into rework.

Fast Mode: Speed and Directness

Fast Mode strips away the planning layer. The AI uses a shortened reasoning chain and gets straight to execution. There's no artifact review—just direct implementation.

When Fast Mode Shines

Fast Mode excels for lightweight tasks where Planning Mode would be overkill:

• Minor edits: Renaming variables, fixing typos, adding a single function
• Test generation: Creating unit tests for existing functionality
• Documentation updates: Adding or revising README sections and inline comments
• Clear bug fixes: Addressing well-defined errors with obvious solutions

Fast Mode isn't careless—it's efficient. It skips unnecessary deliberation for tasks where quick iteration and direct feedback are better than upfront planning.

The Decision Framework: Which Mode to Choose

Here's where theory becomes practical. How do you actually decide?

New File Creation → Planning Mode

When building something from scratch, especially with complex requirements, Plan first.

Example: Creating a REST API endpoint with user authentication,
database transactions, and comprehensive error handling

New files involve countless micro-decisions: data models, error handling strategies, validation logic, and more. Planning Mode lets you see the full design before committing code.

Database and Schema Changes → Planning Mode

Any modification to schemas, migrations, or data structures deserves Planning Mode. Database changes are hard to undo, and the downstream effects are often invisible until runtime.

Planning Mode helps you think through:

• Migration reversibility
• Data consistency during transitions
• Performance implications of new indexes
• Compatibility with existing application logic

Post-Implementation Refinements → Fast Mode

Once your initial feature is built (via Planning Mode), switch to Fast Mode for iteration:

Planning: Build the new chat feature from scratch
  ↓
Fast: Improve the message parsing logic
  ↓
Fast: Adjust the UI styling
  ↓
Fast: Add rate limiting edge cases

This rhythm—Planning for foundations, Fast for refinement—optimizes both quality and velocity.

Real-World Scenario: Multi-Phase Integration

Let's apply this to a realistic project.

Scenario: Adding Real-Time AI Chat to a Legacy Web App

Phase 1: Planning Mode

• How does chat authentication integrate with existing sessions?
• Where do conversation histories persist? (Database, vector DB, ephemeral?)
• What rate limits and quotas apply?
• UI mockups showing integration points

Phase 2: Planning Mode (Part 2)

• API endpoint design and contract specification

Phase 3: Fast Mode (Weeks 2+)

• Endpoint implementation refinements
• Error handling edge cases
• Performance optimizations
• Minor UI adjustments based on user feedback

The pattern: Big decisions in Planning, small adjustments in Fast.

Performance Comparison: Speed vs. Thoroughness

What's the actual time difference?

For trivial changes, Fast Mode's speed advantage is obvious. For substantial decisions, Planning Mode eliminates backtracking that would erase any time savings.

Mastering Planning Mode Feedback

Planning Mode's power depends on how you interact with Artifacts. Generic feedback wastes time; specific requests accelerate iteration.

Weak feedback: "Make this simpler"

Strong feedback: "Can we reorder the task list?
I want schema design → data migration → test setup,
because tests can't run without the schema."

Explain why you want a change. This helps the AI understand your constraints and priorities.

Transitioning Between Modes

As projects mature, the mode balance shifts:

• Early-stage: Mostly Planning (building the foundation)
• Mid-stage: Mixed (new features in Planning, improvements in Fast)
• Maintenance: Mostly Fast (bug fixes, performance tweaks)

This natural progression aligns your workflow with project needs.

Advanced Patterns: Combining Both Modes

Sophisticated users often create hybrid workflows:

1. Plan the architecture in Planning Mode
2. Build modular features with Planning for each major unit
3. Refine within units using Fast Mode
4. Integrate across modules back to Planning if unexpected interactions surface

This layered approach gives you high-level confidence without sacrificing iteration speed.

In-Flight Signals That It's Time to Switch Modes

Even after you've made the broad call at the project level, there are moments inside a single task when you should switch modes. You can't decide these in advance. You notice them while your hands are on the keyboard.

If a fix you started in Fast Mode reaches its third revision, that's a signal to move to Planning. When you keep patching the same spot, the AI is filling local gaps without holding the whole picture. Stopping to redraw the task order in Planning usually lands the work faster in the end.

The same is true when one fix breaks something else. That chain reaction means the design assumptions aren't shared. Chasing it in Fast Mode turns into a loop of breaking and re-fixing. Move to Planning, make the blast radius visible in an Artifact, and then proceed.

The reverse happens too. If you find yourself spending too long confirming a plan in Planning Mode — more than three rounds of Artifact comments without converging — that's evidence the task is small enough. Just running it in Fast is often quicker.

There's a single question that decides it: can you predict the next move? If yes, Fast. If you need to organize your thoughts first, Planning. Asking yourself this repeatedly mid-task sharpens your timing.

Cost looks different through this lens, too. The gap between the two modes is less about raw speed and more about the number of reasoning round-trips. Re-running a stuck Fast task five times can cost more effort than planning it once. The faster mode isn't always the cheaper one.

In my own work as an indie developer running the Dolice Labs blogs, I switch almost unconsciously — Fast for small wording fixes, Planning when changing the structure of an article-generation pipeline. Looking back, the time I lost most was always the "tried to force it in Fast and fixed it three times" moments. The number of times I got stuck was itself the sign I'd picked the wrong mode.

Key Takeaways

Planning Mode and Fast Mode aren't about which is "better"—they're complementary tools:

• Use Planning Mode for: New features, architecture decisions, database changes, complex integrations
• Use Fast Mode for: Bug fixes, test generation, documentation, minor optimizations

Master the distinction, and Antigravity becomes far more than a code generator—it becomes a thinking partner that scales with your project's complexity. Try being intentional about mode selection on your next project, and watch your productivity multiply.