RLM MCP Server

Analyze 10GB+ files with Claude Code — no API keys required.

An MCP server implementing MIT's Recursive Language Models that lets Claude Code analyze files too large for its context window.

┌─────────────────────────────────────────────────────────────┐
│  "Find all errors in this 5GB log file"                     │
│                                                             │
│  Claude → writes Python → RLM executes → returns results    │
│                                                             │
│  Result: 78% fewer tokens, same accuracy                    │
└─────────────────────────────────────────────────────────────┘

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Quick Start

1. Install:

pip install rlm-mcp

2. Configure Claude Code (~/.claude/settings.json):

{
  "mcpServers": {
    "rlm": {
      "command": "rlm-mcp"
    }
  }
}

3. Use it:

Load /var/log/syslog and find all kernel errors

That's it. Claude automatically uses RLM for large file analysis.

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Why RLM?

| Problem | Traditional | RLM Solution | |---------|-------------|--------------| | 10GB log file | ❌ Doesn't fit in context | ✅ Loads externally, queries via Python | | Token usage | 📈 ~12,500 tokens | 📉 ~2,700 tokens (78% less) | | Complex analysis | ❌ Limited to grep patterns | ✅ Full Python (regex, stats, aggregation) |

Real Benchmark

Testing on a 300KB system log with Claude Code Opus 4.5:

┌───────────┬──────────────┬───────────────┬─────────┐
│  Method   │ Input Tokens │ Output Tokens │  Total  │
├───────────┼──────────────┼───────────────┼─────────┤
│ Grep/Read │ ~10,000      │ ~2,500        │ ~12,500 │
│ RLM       │ ~1,500       │ ~1,200        │ ~2,700  │
└───────────┴──────────────┴───────────────┴─────────┘

Both methods found identical results.
RLM used 78% fewer tokens.

---

The Science

Based on Recursive Language Models from MIT CSAIL:

"We propose treating the long context as an 'external environment' to be interacted with via a Python REPL..." — Alex L. Zhang, Tim Kraska, Omar Khattab (MIT), 2025

Paper Results

| Benchmark | Traditional | RLM | |-----------|-------------|-----| | S-NIAH (8M tokens) | 39.3% | 96.0% | | OOLONG QA | 36.2% | 56.7% |

---

How It Works

┌─────────────────┐     ┌─────────────────┐     ┌─────────────────┐
│   Claude Code   │────▶│   RLM Server    │────▶│  Python REPL    │
│   (The Brain)   │◀────│   (MCP)         │◀────│  (Execution)    │
└─────────────────┘     └─────────────────┘     └─────────────────┘

1. You ask: "Find errors in this huge log"
2. Claude loads file via rlm_load_file()
3. Claude writes Python: re.findall(r'ERROR.*', context)
4. RLM executes on full file (outside Claude's context)
5. Only results return to Claude
6. Claude answers with findings

Key insight: Claude is the brain, RLM is the hands. No API keys needed — uses your Claude Code subscription.

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Available Tools

| Tool | Description | |------|-------------| | rlm_load_file | Load a massive file | | rlm_load_multiple_files | Load multiple files as dict | | rlm_execute_code | Run Python on loaded content | | rlm_get_variable | Get a variable's value | | rlm_session_info | Check session state | | rlm_reset_session | Clear session memory |

---

When to Use

┌─────────────────────────────┬────────────────────┐
│          Use Case           │    Recommended     │
├─────────────────────────────┼────────────────────┤
│ Small files (<50KB)         │ Direct read        │
│ Single pattern search       │ Grep               │
│ Large files (>200KB)        │ ✅ RLM             │
│ Complex analysis/statistics │ ✅ RLM             │
│ Multi-pattern correlation   │ ✅ RLM             │
│ Aggregation/counting        │ ✅ RLM             │
│ Cross-file analysis         │ ✅ RLM             │
└─────────────────────────────┴────────────────────┘

---

Example Session

# Load a large log
>>> rlm_load_file("/var/log/app.log")
File loaded: 2,847,392 chars

# Search for errors
>>> rlm_execute_code("""
import re
errors = re.findall(r'ERROR.*', context)
print(f"Found {len(errors)} errors")
""")
Found 156 errors

# Analyze patterns
>>> rlm_execute_code("""
from collections import Counter
types = re.findall(r'ERROR.*?\] (\w+)', context)
print(Counter(types).most_common(5))
""")
[('Connection', 67), ('Database', 43), ('Timeout', 28)]

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Safety

• 30s timeout — Runaway code auto-killed
• Process isolation — Uses multiprocessing
• Output truncation — Prevents memory issues

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Requirements

• Python 3.10+
• Claude Code with MCP support
• No API keys needed

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Links

• GitHub: https://github.com/ahmedm224/rlm-mcp
• Paper: https://arxiv.org/abs/2512.24601
• Issues: https://github.com/ahmedm224/rlm-mcp/issues

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Citation

@article{zhang2025recursive,
  title={Recursive Language Models},
  author={Zhang, Alex L. and Kraska, Tim and Khattab, Omar},
  journal={arXiv preprint arXiv:2512.24601},
  year={2025}
}

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License

MIT © Ahmed Ali