The 256K context window isn't a free-for-all. I learned this the hard way when a single repository analysis cost me like 63 bucks in ten minutes. Here's how to use context intelligently without going broke, using cost optimization strategies.
The Token Math That Nobody Explains
Every character in your context costs money. A typical React component (150 lines) = ~800 tokens. Your entire node_modules
folder? That's like 2 million tokens waiting to bankrupt you, following token pricing models.
Real cost breakdown I tracked:
- Small bugfix (3 files, 2K tokens): like 4 cents per request
- Medium feature (15 files, 25K tokens): about 35 cents per request
- Full codebase dump (180K tokens): almost 3 bucks per request
Multiply by 50 requests during a debugging session and you're looking at real money.
Context Optimization Strategies That Actually Work
File Prioritization Strategy
Instead of dumping everything, rank files by relevance:
- Core files: Main implementation, entry points
- Related files: Imports, dependencies, configs
- Context files: Types, interfaces, shared utilities
- Reference files: Documentation, examples, tests
I use this bash script to analyze which files actually matter, following code analysis patterns:
## Find files that import the target file
grep -r \"from.*filename\" src/ --include=\"*.ts\" --include=\"*.js\"
## Count references to specific functions/classes
grep -r \"MyComponent\" src/ --include=\"*.tsx\" | wc -l
Smart Context Loading
Don't send the whole file if you only need specific functions. Use line numbers to include relevant sections, following selective loading strategies:
## Bad: Send entire 3000-line file
with open('massive_utils.py') as f:
context = f.read()
## Good: Send only relevant function
def extract_function(file_path, function_name, lines_buffer=10):
# Find function start/end, return with buffer
pass
Token Estimation Before Sending
Rough estimation: 1 token ≈ 4 characters for code, 1 token ≈ 3 characters for English text. Use OpenAI's tokenizer for accurate counts and understand tokenization strategies.
def estimate_cost(text, input_rate=0.20):
tokens = len(text) / 4 # Conservative estimate
return (tokens / 1_000_000) * input_rate
print(f\"Est cost: ${estimate_cost(my_context):.4f}\")
Prompt Caching: The Hidden Money Saver
xAI claims 90%+ cache hit rates, but you have to structure requests correctly. Cached tokens cost $0.02 instead of $0.20 per million - that's 90% savings, similar to Anthropic's caching strategy.
Cache-Friendly Pattern
Put stable context first, variable parts last:
## Good: Stable context gets cached
messages = [
{\"role\": \"system\", \"content\": project_context}, # This gets cached
{\"role\": \"user\", \"content\": f\"Debug this: {error_msg}\"} # Only this varies
]
## Bad: Context changes every time
messages = [
{\"role\": \"user\", \"content\": f\"Debug {error_msg} in context: {project_context}\"}
]
Measuring Cache Performance
Check the response usage object:
response = client.chat.create(...)
usage = response.usage
print(f\"Cached tokens: {usage.prompt_tokens_cached}\")
print(f\"New tokens: {usage.prompt_tokens}\")
print(f\"Cache hit rate: {usage.prompt_tokens_cached / usage.prompt_tokens:.2%}\")
If your cache hit rate is below 70%, you're structuring requests wrong.
When Context Windows Become Context Chaos
The 200K Token Death Trap
Large context doesn't mean better responses. I've seen quality degrade past 150K tokens as the model gets overwhelmed, following context length limitations. Break large codebases into focused sessions using information retrieval principles:
- Session 1: Architecture and main components
- Session 2: Specific feature implementation
- Session 3: Error handling and edge cases
Context Pollution Prevention
Remove noise before sending, following clean code principles and gitignore patterns:
- Generated files (
dist/
,build/
,.next/
) - Dependencies (
node_modules/
,vendor/
) - Binary files, images, videos
- Log files and temporary data
- Commented-out code blocks
Memory Leak Detection
Track context growth in long conversations:
class ContextTracker:
def __init__(self):
self.context_sizes = []
def add_message(self, content):
size = len(content) / 4 # Rough token estimate
self.context_sizes.append(size)
if len(self.context_sizes) > 20: # Keep last 20 messages
self.context_sizes.pop(0)
def current_size(self):
return sum(self.context_sizes)
Production Context Management
Multi-Repository Strategy
For codebases spanning multiple repos, create context summaries:
def create_repo_summary(repo_path):
summary = {
\"structure\": get_file_tree(repo_path),
\"key_files\": identify_entry_points(repo_path),
\"dependencies\": parse_package_json(repo_path),
\"readme_excerpt\": extract_readme_key_points(repo_path)
}
return json.dumps(summary, indent=2)
Send summaries for related repos, full context for the target repo.
Context Versioning
Track which context produced which results:
context_hash = hashlib.md5(context.encode()).hexdigest()[:8]
print(f\"Request {context_hash}: {response.choices[0].message.content}\")
This helps debug when results change unexpectedly.
Emergency Context Reduction
When you're mid-session and hitting token limits:
- Quick wins: Remove comments, collapse whitespace, strip imports
- File reduction: Keep only files that were referenced in recent responses
- Function extraction: Replace large functions with just their signatures
- Historical pruning: Remove older conversation history
Emergency Context Script
## Remove comments and blank lines
grep -v '^[[:space:]]*#' file.py | grep -v '^[[:space:]]*$'
## Get just function signatures
grep -E '^def |^class |^async def' file.py
The goal isn't perfect context - it's actionable context that doesn't bankrupt you. Better to get a slightly less perfect answer for $0.05 than the perfect answer for $5.00.
Start small, measure costs, scale intelligently. Your future self (and your credit card) will thank you.