OmniRoute/docs/COMPRESSION_GUIDE.md

🗜️ Prompt Compression Guide — OmniRoute

Save 15-75% on token costs automatically. For a quick overview, see the README Compression section.

Overview

OmniRoute implements a modular prompt compression pipeline that runs proactively before requests hit upstream providers. This means your token savings happen transparently — no changes needed to your workflow.

Client Request
  → Compression Strategy Selector
    → Combo override? → Use combo setting
    → Auto-trigger threshold? → Use auto mode
    → Default mode? → Use global setting
    → Off? → Skip compression
  → Selected Compression Mode
    → Off: No compression
    → Lite: Safe whitespace/formatting cleanup (~15%)
    → Standard: Caveman-speak filler removal (~30%)
    → Aggressive: History aging + summarization (~50%)
    → Ultra: Heuristic pruning + code-block thinning (~75%)
  → Compressed Request → Provider

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Compression Modes

Off

No compression applied. All messages pass through unchanged.

Lite Mode (~15% savings, <1ms latency)

The safest mode — zero semantic change, only formatting cleanup:

Technique	Description
collapseWhitespace	Merge consecutive blank lines and trailing spaces
dedupSystemPrompt	Remove duplicate system messages
compressToolResults	Compress verbose tool/function outputs
removeRedundantContent	Strip repeated instructions
replaceImageUrls	Shorten base64 image data URIs

Best for: Always-on usage, safety-critical workflows.

Standard Mode (~30% savings)

Inspired by Caveman — removes filler words and verbose phrasing while preserving meaning:

• Removes filler words ("please", "I think", "basically", "actually")
• Condenses verbose phrases ("in order to" → "to", "as a result of" → "because")
• Strips polite hedging ("Would you mind...", "If you could possibly...")
• 30+ regex rules tuned for coding prompts

Best for: Daily coding workflows, cost-conscious teams.

Aggressive Mode (~50% savings)

Smart history management for long sessions:

• Message Aging — older messages get progressively compressed
• Tool Result Summarization — long tool outputs replaced with summaries
• Structural Integrity Guards — ensures tool_use + tool_result pairs stay consistent
• Context Window Awareness — respects per-model token limits

Best for: Extended debugging sessions, large codebases.

Ultra Mode (~75% savings)

Maximum compression for token-critical scenarios:

• Heuristic Pruning — removes messages below relevance threshold
• Code Block Thinning — compresses repetitive code examples
• Binary Search Truncation — finds optimal cut point for context window
• All Aggressive mode features included

Best for: When you're hitting context limits repeatedly.

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Token Savings Visualization

Without compression: 47K tokens sent to LLM
With Lite:           40K tokens sent          (15% saved — safe, always-on)
With Standard:       33K tokens sent          (30% saved — caveman-speak rules)
With Aggressive:     24K tokens sent          (50% saved — aging + summarization)
With Ultra:          12K tokens sent          (75% saved — heuristic pruning)

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Configuration

Dashboard

Navigate to Dashboard → Settings → Compression:

• Default Mode — sets the system-wide compression mode
• Auto-Trigger Threshold — automatically engage compression when token count exceeds threshold
• Per-Combo Override — each combo can have its own compression mode

Per-Combo Override

In Dashboard → Combos → [Your Combo] → Advanced, set compression mode per combo:

Combo: "free-forever"
  Mode: Standard
  Targets:
    1. gc/gemini-3-flash
    2. if/kimi-k2-thinking

This lets you use aggressive compression on free providers while keeping lite mode on paid subscriptions.

API

# Get compression settings
curl http://localhost:20128/api/settings/compression

# Update compression settings
curl -X PUT http://localhost:20128/api/settings/compression \
  -H "Content-Type: application/json" \
  -d '{"defaultMode":"lite","autoTriggerThreshold":32000}'

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What Gets Protected

The compression engine always preserves:

• ✅ Code blocks (fenced and inline)
• ✅ URLs and file paths
• ✅ JSON structures and structured data
• ✅ API keys, tokens, and identifiers
• ✅ Mathematical expressions
• ✅ Tool/function call definitions
• ✅ System prompts (in lite mode)

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Compression Stats

Every compressed request includes stats in the server logs:

{
  "originalTokens": 47200,
  "compressedTokens": 40120,
  "savingsPercent": 15.0,
  "techniquesUsed": ["collapseWhitespace", "dedupSystemPrompt"],
  "mode": "lite",
  "latencyMs": 0.8
}

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Phase Roadmap

Phase	Modes	Status
Phase 1	Off, Lite	✅ Shipped
Phase 2	Standard, Aggressive, Ultra	✅ Shipped
Phase 3	Per-model adaptive, ML-based pruning	🗓️ Planned

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Acknowledgments

Standard mode compression rules are inspired by Caveman by JuliusBrussee (⭐ 51K+) — the viral "why use many token when few token do trick" project.

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See Also

• Environment Config — Compression environment variables
• Architecture Guide — Compression pipeline internals
• User Guide — Getting started with compression