What is a Context Window?
A context window is how much text the AI can look at and remember at one time. Think of it like the AI’s short-term memory.
What are tokens? Tokens are small pieces of text. About 4 letters = 1 token. So “hamburger” is 2 tokens: “ham” and “burger”. When we say “128K tokens,” that means the AI can remember about 96,000 words at once.
Important: Bigger context windows let the AI see more of your project, but they cost more money and take longer.
Size Guide
| Size | Tokens | About How Many Words | Good For |
|---|
| Small | 8K-32K | 6,000-24,000 | One file, quick fixes |
| Medium | 128K | ~96,000 | Most projects |
| Large | 200K | ~150,000 | Big projects |
| Extra Large | 400K+ | ~300,000+ | Whole apps |
| Huge | 1M+ | ~750,000+ | Multiple projects |
Different AI Models
| AI Model | Context Window | Actually Works Well* | Notes |
|---|
| Claude Sonnet 4.5 | 1M tokens | ~500K tokens | Best for big projects |
| GPT-5 | 400K tokens | ~300K tokens | Has three different modes |
| Gemini 2.5 Pro | 1M+ tokens | ~600K tokens | Great for reading documents |
| DeepSeek V3 | 128K tokens | ~100K tokens | Good for most things |
| Qwen3 Coder | 256K tokens | ~200K tokens | Nice balance |
What Uses Up the Context Window
- Your messages - Everything you and the AI say in the chat
- Your files - Files the AI reads from your project
- Command results - Output from commands that run
- System instructions - CodinIT’s background instructions (uses very little)
How to Save Context Space
1. Start fresh for new features
/new - Start a new chat with empty context
- You get the full context window
- No old, irrelevant messages
- AI focuses better
2. Only include files you need
Instead of including everything:
@filename.ts - Only mention files when necessary- Use search instead of reading big files
- Reference specific parts, not whole files
3. Turn on auto-compact
CodinIT can automatically shorten long conversations:
- Go to Settings → Features → Auto-compact
- Keeps important stuff
- Uses fewer tokens
Warning Signs
How to Tell You’re Running Out of Space
| Warning Sign | What It Means | What to Do |
|---|
| ”Context window exceeded” | You hit the limit | Start a new chat or turn on auto-compact |
| Slow responses | AI is struggling | Include fewer files |
| AI repeats itself | Context is too fragmented | Start fresh |
| AI forgets recent changes | Too much context | Use checkpoints |
Tips by Project Size
Small projects (less than 50 files)
- Any AI model works fine
- Include files freely
- Don’t worry about optimization
Medium projects (50-500 files)
- Use AI with 128K+ context
- Only include files you’re working on
- Start new chats between features
Large projects (500+ files)
- Use AI with 200K+ context
- Focus on one part at a time
- Search instead of reading many files
- Break work into smaller pieces
Advanced Tips
Use Plan/Act Mode Smartly
Use different AI models for different tasks:
- Plan Mode: Use cheaper AI for talking and planning
- Act Mode: Use better AI when writing code
Example:
Plan Mode: DeepSeek V3 (128K) - Cheap for planning
Act Mode: Claude Sonnet (1M) - Better for coding
How CodinIT Saves Space
CodinIT can automatically remove less important text:
- Remove old messages: Delete old parts of the conversation
- Keep relevant code: Only keep code related to what you’re doing now
- Keep summaries: Keep the main ideas but remove details
Counting Tokens
Quick math
- 1 token ≈ 3/4 of a word (1,000 tokens = about 750 words)
- 1 token ≈ 4 letters
- 100 lines of code ≈ 500-1000 tokens
File sizes
| File Type | Tokens per KB |
|---|
| Code | ~250-400 |
| JSON | ~300-500 |
| Markdown | ~200-300 |
| Plain text | ~200-250 |
Common Questions
Q: Why does the AI get worse with long conversations?
A: The AI loses focus when there’s too much to remember. It works best with 50-70% of its maximum.
Q: Should I always use the biggest context window?
A: No. Bigger contexts cost more and can make the AI worse. Use what you need for your task.
Q: How do I know how much context I’m using?
A: CodinIT shows you a meter. Watch it to see when you’re getting close to the limit.
Q: What happens if I go over the limit?
A: CodinIT will:
- Automatically shorten the conversation (if you turned that on)
- Show an error and tell you to start a new chat
- Remove old messages (with a warning)
What to Use When
| What You’re Doing | Context Size | Which AI |
|---|
| Quick fixes | 32K-128K | DeepSeek V3 |
| Building features | 128K-200K | Qwen3 Coder |
| Big changes | 400K+ | Claude Sonnet 4.5 |
| Reviewing code | 200K-400K | GPT-5 |
| Writing docs | 128K | Any cheap model |
