# How to Give Cursor Your Full Codebase — Fix Context Window Limits

Last updated: April 2026 | Reading time: 6 min

If you've used Cursor on a real project, you've experienced the frustration: Cursor hallucinates function calls, invents APIs that don't exist, and misses obvious dependencies. The root cause isn't Cursor's AI model — it's the context window limit.

## The Problem: Cursor Only Sees 5-10 Files

Cursor uses a combination of open tabs, recent files, and embedding-based retrieval to fill the context window. On a typical project with 500+ files, Cursor can only see about 5-10 files per request — roughly 5% of your codebase.

The other 95% is completely invisible to the AI. This means:

- Hallucinated imports — Cursor references modules it can't see
- Invented APIs — it guesses function signatures instead of reading them
- Missed dependencies — changes `auth.py` without knowing about `auth_config.py`
- Duplicate code — writes functions that already exist elsewhere
- Incomplete refactors — only updates files it can see, breaking the rest

You've probably worked around this by manually pasting code, writing detailed system prompts, or adding `.cursorrules` files. There's a better way.

## The Fix: Context Engineering with Entroly

Entroly is a context engineering engine that compresses your entire codebase into Cursor's context window at variable resolution:

- Critical files appear in full (the code Cursor needs to edit)
- Supporting files appear as function signatures (types, interfaces, configs)
- Everything else appears as one-line references (so Cursor knows they exist)

The result: Cursor sees all your files, uses 78% fewer tokens, and gives dramatically better answers.

## Setup: 2 Minutes with Cursor

### Step 1: Install Entroly

    pip install entroly[full]

### Step 2: Initialize for Cursor

    entroly init

This auto-detects Cursor and generates `.cursor/mcp.json` — the MCP server configuration that connects Entroly to Cursor.

### Step 3: Verify

    entroly demo

This runs a before/after comparison on YOUR codebase, showing exactly how many tokens you'll save and which files get which resolution level.

## Before vs After

| Before Entroly | After Entroly
--- | --- | ---
Files visible | 5-10 files | All files
Tokens/request | ~186,000 | ~40,000 (78% less)
Hallucinations | Frequent | Rare
Cost/1K requests | ~$560 | ~$124
Setup time | Hours of prompt eng. | 2 minutes
Overhead | N/A | <10ms

## How It Works Under the Hood

Entroly runs as an MCP (Model Context Protocol) server that Cursor connects to natively. When you make a request in Cursor:

1. Entroly indexes your codebase — builds a dependency graph, fingerprints every code fragment
2. Scores fragments by information density — high-value code ranks high, boilerplate ranks low
3. Selects the optimal subset — mathematically proven optimal via knapsack solver (not approximate top-K)
4. Delivers at variable resolution — critical files in full, supporting files as signatures, everything else as references
5. Learns from outcomes — reinforcement learning adjusts weights based on which context produced good AI responses

The entire pipeline adds less than 10ms per request. You won't notice it.

## Quality Presets

Control the speed vs quality tradeoff:

    entroly proxy --quality speed       # minimal optimization, lowest latency
    entroly proxy --quality balanced    # recommended for most projects
    entroly proxy --quality max         # full pipeline, best results

## FAQ

### Does it send my code to any external service?

No. Everything runs locally on your machine. Your code never leaves your computer.

### Does it work with Cursor's free tier?

Yes. Entroly works with any Cursor plan. In fact, it's even more valuable on the free tier since you have fewer requests — each one needs to count.

### Does it replace .cursorrules?

No — they're complementary. `.cursorrules` gives Cursor instructions about your preferences. Entroly gives Cursor visibility into your actual code. Use both.

### What languages does it support?

All of them. Entroly works at the file/fragment level, not the AST level. It supports any text-based source code.

### Stop Cursor from hallucinating. Give it your full codebase.

One install. Zero config changes to Cursor. Works immediately.

    pip install entroly[full] && entroly go

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