616 lines
26 KiB
Markdown
616 lines
26 KiB
Markdown
---
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title: "Extending the Compression Pipeline"
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version: 3.8.44
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lastUpdated: 2026-07-02
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---
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# Extending the Compression Pipeline
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> **TL;DR**: OmniRoute's compression engine is **pluggable** — you can register custom engines, ship language packs for new languages, and compose stacked pipelines. This guide shows how.
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**Related guides:**
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- [COMPRESSION_GUIDE.md](./COMPRESSION_GUIDE.md) — Full pipeline overview
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- [COMPRESSION_ENGINES.md](./COMPRESSION_ENGINES.md) — Engine registry and built-in engines
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- [RTK_COMPRESSION.md](./RTK_COMPRESSION.md) — RTK engine and custom filters
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- [COMPRESSION_RULES_FORMAT.md](./COMPRESSION_RULES_FORMAT.md) — Rule pack format reference
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---
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## Overview
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The compression system has **3 extension points**:
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| Extension point | Use case | Difficulty |
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| -------------------- | ------------------------------------------------------------------------ | ---------- |
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| **Custom engine** | Add a brand-new compression algorithm (e.g., domain-specific summarizer) | Advanced |
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| **Language pack** | Add support for a new natural language (e.g., Hindi, Arabic) | Medium |
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| **Stacked pipeline** | Compose existing engines in a custom order | Beginner |
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```
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┌─────────────────────────────────────────────────────────────┐
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│ Compression Strategy │
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│ │
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│ Input messages ──▶ getEffectiveMode() ──▶ mode │
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│ │ │
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│ ┌───────────────────────┼──────────┐ │
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│ │ │ │ │ │ │
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│ ▼ ▼ ▼ ▼ │ │
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│ "rtk" "lite" "standard" "stacked" │
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│ │ │ │ │ │ │
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│ ▼ ▼ ▼ ▼ │ │
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│ RTK Lite Caveman engines[] │
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│ engine engine engine chained │
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│ │ │ │ │ │ │
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│ └─────────┴─────────┴─────────┘ │ │
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│ │ │
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│ ▼ │
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│ Compressed output │
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└─────────────────────────────────────────────────────────────┘
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The strategy selector is MODE-BASED: each request selects ONE mode
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(rtk / lite / standard / aggressive / ultra / stacked / off).
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Only mode "stacked" chains multiple engines in sequence.
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Default auto-trigger mode is "lite" (not a 3-tier priority chain).
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```
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---
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## Writing a Custom Compression Engine
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The engine interface (`open-sse/services/compression/engines/types.ts`) is the contract every engine must satisfy. It has 5 required methods.
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### The `CompressionEngine` Interface
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```ts
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interface CompressionEngine {
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id: string; // Unique engine ID
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name: string; // Display name
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description: string; // Short description
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icon: string; // Icon (emoji or URL)
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targets: CompressionEngineTarget[]; // ["messages", "tool_results", "code_blocks"]
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stackable: boolean; // Can be used in a stacked pipeline
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stackPriority: number; // Order in stacked pipelines (lower = earlier)
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metadata: CompressionEngineMetadata;
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apply(body, options?): CompressionResult;
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compress(body, config?): CompressionResult;
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getConfigSchema(): EngineConfigField[];
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validateConfig(config): EngineValidationResult;
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}
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```
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### Minimal Example: Whitespace Engine
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The simplest possible engine — strip extra whitespace from messages.
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````ts
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import type { CompressionEngine } from "omniroute/compression/engines/types";
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import { registerCompressionEngine } from "omniroute/compression/engines/registry";
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function preserveCodeBlocks(text: string): string {
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// Split by code block markers and preserve whitespace inside them
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const parts = text.split(/(```[\s\S]*?```)/);
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return parts
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.map((part) => {
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if (part.startsWith("```")) {
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return part; // Don't modify code blocks
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}
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return part.replace(/\n{3,}/g, "\n\n"); // Only apply to prose
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})
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.join("");
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}
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const whitespaceEngine: CompressionEngine = {
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id: "whitespace",
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name: "Whitespace Stripper",
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description: "Removes extra whitespace and blank lines",
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icon: "📝",
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targets: ["messages", "tool_results"],
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stackable: true,
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stackPriority: 100, // Run AFTER caveman/rtk
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metadata: {
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id: "whitespace",
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name: "Whitespace Stripper",
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description: "Removes extra whitespace and blank lines",
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inputScope: "messages",
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targetLatencyMs: 5,
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supportsPreview: true,
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stable: true,
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},
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apply(body, options) {
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return this.compress(body, options?.config);
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},
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compress(body, config = {}) {
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let originalLength = 0;
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let compressedLength = 0;
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// Traverse message array — handle both string and multipart content
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const compressedBody = (body.messages || []).map((msg) => {
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if (typeof msg.content === "string") {
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originalLength += msg.content.length;
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let compressed = msg.content
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.replace(/[ \t]+/g, " ")
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.replace(/\n{3,}/g, "\n\n")
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.replace(/^\s+|\s+$/gm, "");
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compressedLength += compressed.length;
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return { ...msg, content: compressed };
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}
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// Multipart content: traverse parts, compress text parts only
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if (Array.isArray(msg.content)) {
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const newParts = msg.content.map((part) => {
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if (part.type === "text" && typeof part.text === "string") {
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originalLength += part.text.length;
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let compressed = part.text
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.replace(/[ \t]+/g, " ")
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.replace(/\n{3,}/g, "\n\n")
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.replace(/^\s+|\s+$/gm, "");
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compressedLength += compressed.length;
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return { ...part, text: compressed };
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}
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return part; // preserve image_url, tool_use, etc.
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});
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return { ...msg, content: newParts };
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}
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return msg;
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});
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return {
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body: { ...body, messages: compressedBody },
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stats: {
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originalTokens: Math.ceil(originalLength / 4),
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compressedTokens: Math.ceil(compressedLength / 4),
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savingsPercent: originalLength > 0 ? 100 * (1 - compressedLength / originalLength) : 0,
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techniques: ["whitespace-collapse"],
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engineId: "whitespace",
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},
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};
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},
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getConfigSchema() {
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return [
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{
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key: "preserveCodeBlocks",
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type: "boolean",
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label: "Preserve code blocks",
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defaultValue: true,
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description: "Don't touch whitespace inside ```code``` blocks",
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},
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];
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},
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validateConfig(config) {
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if (config.preserveCodeBlocks !== undefined && typeof config.preserveCodeBlocks !== "boolean") {
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return { valid: false, errors: ["preserveCodeBlocks must be a boolean"] };
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}
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return { valid: true, errors: [] };
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},
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};
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// Register globally
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registerCompressionEngine(whitespaceEngine);
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````
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### Where to Place Custom Engines
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```
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~/.omniroute/compression/engines/my-engine.ts # User-level
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<project>/compression-engines/my-engine.ts # Project-level (loaded on startup)
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```
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Or load programmatically from a plugin:
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```ts
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// In your plugin
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import {
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registerCompressionEngine,
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unregisterCompressionEngine,
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} from "@omniroute/open-sse/services/compression/engines/registry";
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import { myEngine } from "./engines/my-engine";
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export default definePlugin({
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name: "my-compression-plugin",
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// The plugin SDK exposes onRequest / onResponse / onError hooks. Register the
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// engine when the plugin module loads (or on first onRequest); unregister it
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// from your own teardown path.
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onRequest: async (ctx) => {
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registerCompressionEngine(myEngine);
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},
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});
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// On teardown:
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// unregisterCompressionEngine("my-engine");
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```
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### Testing Your Engine
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Register your engine in a plugin or startup function. Once registered, the engine will be available
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in the strategy selector via its `id`. Test integration by composing it in a stacked pipeline:
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---
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## Creating Language Packs
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Caveman-style compression uses **language-specific rule packs** to handle fillers, hedging, and verbose patterns in each natural language. OmniRoute ships with **6 language packs**: `en`, `es`, `fr`, `de`, `ja`, `pt-BR`.
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### Pack Structure
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A language pack is a directory of **JSON files** under `open-sse/services/compression/rules/<language>/`:
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```
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open-sse/services/compression/rules/
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├── en/
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│ ├── filler.json # Pleasantries, hedging, politeness
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│ ├── context.json # Context-reducing rules
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│ ├── dedup.json # Deduplication rules
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│ ├── structural.json # Punctuation, formatting
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│ └── ultra.json # Aggressive compression rules
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├── es/ (same structure)
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├── fr/ (same structure)
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├── de/ (same structure)
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├── ja/ (same structure)
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└── pt-BR/ (same structure)
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```
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### Rule Anatomy
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Each rule has this shape (from `open-sse/services/compression/ruleLoader.ts`):
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```ts
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interface FileRule {
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name: string; // Human-readable name (kebab-case)
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pattern: string; // JavaScript regex pattern
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replacement?: string; // What to replace the match with
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replacementMap?: Record<string, string>; // OR a key→replacement map
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flags?: string; // Regex flags ("gi" typically)
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context?: "all" | "user" | "system" | "assistant";
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category?: "filler" | "context" | "structural" | "dedup" | "terse" | "ultra";
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minIntensity?: "lite" | "full" | "ultra"; // Skip below this intensity
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description?: string; // Documentation
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}
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```
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### Example: Adding Hindi Filler Rules
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```json
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{
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"language": "hi",
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"category": "filler",
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"rules": [
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{
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"name": "polite_opener",
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"pattern": "\\b(?:नमस्ते|नमस्कार|आदरणीय)\\b[,!\\s]*",
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"replacement": "",
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"context": "all",
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"category": "filler",
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"minIntensity": "lite",
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"description": "Strip polite openers like 'नमस्ते'"
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},
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{
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"name": "filler_actually",
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"pattern": "\\b(?:असल में|वास्तव में|दरअसल)\\b\\s*",
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"replacement": "",
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"context": "all",
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"category": "filler",
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"minIntensity": "lite",
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"description": "Strip 'actually' fillers"
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},
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{
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"name": "verbose_plea",
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"pattern": "\\b(?:कृपया|कृपया आप|अनुरोध है कि आप)\\b\\s*",
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"replacement": "",
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"context": "all",
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"category": "filler",
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"minIntensity": "full",
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"description": "Strip 'please' in Hindi"
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}
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]
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}
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```
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### Validation
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Rule packs are validated against `_schema.json` on load. A pack with bad structure will fail to load and log an error:
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```
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RULE_LOADER: pack "hi/filler.json" failed validation:
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- rules.0.pattern: Invalid regex
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- rules.1.context: must be one of [all, user, system, assistant]
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```
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Validation runs automatically when a pack is loaded (against `_schema.json`); an
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invalid pack is rejected and the error above is logged. There is no separate
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`npm run` script for pack validation — load the pack (e.g. start the server or
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exercise the compression path) and watch the logs.
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### Loading a Custom Language Pack
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```ts
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import { loadRulePack } from "omniroute/compression/ruleLoader";
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await loadRulePack("./my-custom-rules/hi/filler.json");
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```
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Or place in a recognized location:
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```
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~/.omniroute/compression/rules/hi/filler.json # User-level
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<project>/.compression/rules/hi/filler.json # Project-level
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```
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### Best Practices for Language Packs
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1. **Start with `filler`** — these are the highest-impact rules
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2. **Use `minIntensity`** to gate aggressive rules — protects against over-compression
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3. **Include test cases** — add `tests[]` array in the JSON to verify behavior
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4. **Order matters** — earlier rules apply first; place high-impact rules first
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5. **Be conservative with `replacement`** — empty string is usually correct; never introduce new content
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### Translation Strategy
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When localizing rule packs to a new language:
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1. **Translate the rule names** — they appear in debug output
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2. **Adapt the regex patterns** — direct translation often fails (word boundaries differ)
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3. **Test against real conversations** — the pack should be safe on actual input
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4. **Match cultural conventions** — Japanese packs, for instance, have more honorific fillers than English
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---
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## Stacked Pipelines
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A **stacked pipeline** runs multiple engines in sequence, with each engine's output feeding the next. This is how `mode: stacked` works internally.
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### How Stacking Works
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```
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Input (10,000 tokens)
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│
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▼
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┌──────────┐
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│ Engine │ priority 10
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│ A │ ──▶ output: 6,000 tokens (-40%)
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└────┬─────┘
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▼
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┌──────────┐
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│ Engine │ priority 50
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│ B │ ──▶ output: 2,400 tokens (-60%)
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└────┬─────┘
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▼
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┌──────────┐
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│ Engine │ priority 100
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│ C │ ──▶ output: 1,200 tokens (-80%)
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└────┬─────┘
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│
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▼
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Final output (1,200 tokens, ~88% savings combined)
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```
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When `mode: "stacked"` is selected, engines execute sequentially in the order specified in the `pipeline` array.
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The output of engine N becomes the input of engine N+1.
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### Compression Modes
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OmniRoute selects **ONE mode per request** based on configuration, auto-trigger thresholds, and combo overrides.
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The available modes are defined in `open-sse/services/compression/types.ts` (type `CompressionMode`):
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| Mode | Engines | Use case |
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| ------------ | -------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `off` | None | Disable all compression |
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| `rtk` | RTK only | Command-output heavy sessions (80%+ savings) |
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| `lite` | Lite only | Conservative compression (fast, safe) |
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| `standard` | Caveman | Prose compression with language packs |
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| `aggressive` | Caveman + Aggressive | Aggressive prose + aggressive final pass |
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| `ultra` | Ultra | Maximum compression (lossy, last resort). Optionally routed through the **LLMLingua-2** SLM engine when `ultra.modelPath` is set (fail-opens to the rule-based path when the model is unavailable). |
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| `stacked` | Custom pipeline | Compose engines in any order (see below) |
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> Beyond the mode engines above, the registry also ships specialized stackable engines —
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> **CCR**, **headroom**, **ionizer**, and **session-dedup** — documented in
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> [COMPRESSION_ENGINES.md](./COMPRESSION_ENGINES.md#additional-built-in-engines).
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Mode selection is determined by `getEffectiveMode()` in `open-sse/services/compression/strategySelector.ts`:
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1. If compression is disabled: `"off"`
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2. If a combo override exists: use the override
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3. If auto-trigger threshold is exceeded: use `autoTriggerMode` (default: `"lite"`)
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4. Otherwise: use `defaultMode`
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### The Default Stacked Pipeline
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When `mode: "stacked"` is explicitly configured, the default pipeline composes:
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1. **RTK** — strip command output noise (~80% savings on terminal output)
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2. **Caveman** — remove fillers, terse-ify prose (~46% on remaining text)
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3. **Lite** — final whitespace + dedup pass
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This composition achieves **78-95% savings** on tool-heavy sessions.
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### Configuring Stacked Pipelines
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In combo config:
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```json
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{
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"compression": {
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"mode": "stacked",
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"pipeline": [
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{ "engine": "rtk", "config": { "intensity": "aggressive" } },
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{ "engine": "caveman", "config": { "intensity": "full" } },
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{ "engine": "lite", "config": {} }
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]
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}
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}
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```
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You can omit engines, add custom ones, or reorder them.
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### State Passing
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Engines can read metadata from the request context (in `options`):
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```ts
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compress(body, config) {
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// Read metadata from previous engines
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const original = options?.compressionComboId; // "my-coding-combo"
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// ...
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}
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```
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The metadata is **read-only** — engines cannot mutate the request context, only their own body output.
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### Execution Order Gotchas
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| Engine order | Effect |
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| ----------------------------------- | ------------------------------------------------------------------------------ |
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| RTK → Caveman → Lite | **Recommended** (strips noise first, then language, then whitespace) |
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| Lite → RTK → Caveman | Bad — Lite strips whitespace from raw output, making RTK pattern matching fail |
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| Caveman → RTK | Bad — Caveman may rewrite text in ways that RTK doesn't recognize |
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| Any order with `tool_results` first | Better — tool output is the noisiest content |
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### When NOT to Stack
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Stacking isn't always better:
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- **Simple messages** (no tool output) — single Caveman or Lite is enough
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- **Cost-sensitive** — each engine adds ~5-50ms latency
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- **Specific tools** — RTK alone is usually sufficient for shell output
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### Building a Custom Pipeline
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There is no named-pipeline registry. A stacked pipeline is just an **inline array
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of steps** passed to `applyStackedCompression()` (exported from
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`@omniroute/open-sse/services/compression/strategySelector`):
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```ts
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import { applyStackedCompression } from "@omniroute/open-sse/services/compression/strategySelector";
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const result = applyStackedCompression(body, [
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{ engine: "rtk", intensity: "aggressive" },
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{ engine: "caveman", intensity: "full" },
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]);
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```
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When you don't pass a pipeline, it defaults to `rtk(standard) → caveman(full)`.
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To drive it from config, set `mode: "stacked"` and provide the step array under
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`stackedPipeline` (read from `config.stackedPipeline`):
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```json
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{
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"compression": {
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"mode": "stacked",
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"stackedPipeline": [
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{ "engine": "rtk", "intensity": "aggressive" },
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|
{ "engine": "caveman", "intensity": "full" }
|
|
]
|
|
}
|
|
}
|
|
```
|
|
|
|
---
|
|
|
|
## Upstream Sync Policy
|
|
|
|
OmniRoute's compression engines credit several upstream projects in the README
|
|
("inspired by RTK, Caveman, LLMLingua-2, Troglodita"). A common contributor
|
|
question is: **when upstream RTK adds a new tool filter or Caveman adds a rule
|
|
pack, how does that reach OmniRoute?** This section is the authoritative answer.
|
|
|
|
### Vendored copies vs. independent implementations
|
|
|
|
| Engine | Relationship to upstream | Location |
|
|
| ---------------------------- | ------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------- |
|
|
| **RTK** | **Independent reimplementation** (inspired-by, not a copy) | `open-sse/services/compression/engines/rtk/` |
|
|
| **Caveman** | **Independent reimplementation** (inspired-by) | `open-sse/services/compression/engines/cavemanAdapter.ts` |
|
|
| **Headroom** | Mostly internal; only the `gcf/` codec is **genuinely vendored** from `gcf-typescript` (MIT, SPDX-marked, generic profile only) | `open-sse/services/compression/engines/headroom/gcf/` |
|
|
| **LLMLingua-2 / Troglodita** | Inspired-by (drive the `llmlingua` + `session-dedup` engines) | `open-sse/services/compression/engines/llmlingua/`, `session-dedup` |
|
|
|
|
Key point: **RTK and Caveman are clean-room TypeScript implementations of the
|
|
_ideas_ (filter rules, rule packs), not vendored source trees.** There is no
|
|
upstream copy to `git pull` from — which is exactly why the README says
|
|
"inspired by" rather than "bundled".
|
|
|
|
### How upstream improvements are merged
|
|
|
|
There is **no automated upstream-release tracking and no `compression-sync`
|
|
label** — by design. Because the engines are reimplementations, an upstream RTK
|
|
filter or Caveman rule pack is not merged as code; it is **re-expressed as a new
|
|
rule/filter in OmniRoute's own format** (see
|
|
[COMPRESSION_RULES_FORMAT.md](./COMPRESSION_RULES_FORMAT.md)) and lands ad-hoc via
|
|
a normal PR. The extension points above (custom engine, language pack, RTK filter)
|
|
are the sanctioned way to contribute one.
|
|
|
|
Recent examples of exactly this flow:
|
|
|
|
- RTK filters for Gradle & `dotnet` build output (v3.8.42)
|
|
- RTK filters for kubectl / docker-build / composer / gh (#2824)
|
|
- Caveman Indonesian language pack (#3975), plus German / French / Japanese / Chinese packs
|
|
|
|
### Headroom (input-compression proxy)
|
|
|
|
Headroom is **fully internal** — a pinned vendored `gcf` codec snapshot plus
|
|
OmniRoute's own `smartcrusher` / `toon` / `tabular` layers. There is no live
|
|
upstream to track beyond the vendored copy; updates to `gcf` are refreshed
|
|
manually when the codec changes and re-validated against the compression budget
|
|
gate (`check:compression-budget`).
|
|
|
|
### Proposing an upstream-inspired improvement
|
|
|
|
1. **Don't vendor** — re-express the upstream rule/filter in OmniRoute's format.
|
|
2. Add it via the matching extension point below (language pack, RTK filter, or
|
|
custom engine).
|
|
3. Reference the upstream project in the PR description (attribution), not by
|
|
copying its license-bearing source.
|
|
4. Include tests and confirm the `check:compression-budget` gate still passes.
|
|
|
|
---
|
|
|
|
## Best Practices
|
|
|
|
### Engine Development
|
|
|
|
1. **Always implement `validateConfig`** — engines without validation cause silent failures
|
|
2. **Set realistic `targetLatencyMs`** — used by the strategy selector to choose engines
|
|
3. **Use `getConfigSchema` for the dashboard** — never hide config from users
|
|
4. **Support `stackable: true` if your engine is pure** — engines with side effects shouldn't stack
|
|
5. **Write inline tests** — engines should be verifiable in <1s
|
|
|
|
### Language Pack Development
|
|
|
|
1. **Start with `lite` intensity** — your rules should be safe at the lowest setting
|
|
2. **Use `context` to scope rules** — `user` only rules can't accidentally affect system prompts
|
|
3. **Avoid capturing JSON keys** — `\\bword\\b` can match inside JSON, breaking structured data
|
|
4. **Test with edge cases** — empty input, unicode, RTL text, emojis
|
|
5. **Use existing packs as templates** — `en/filler.json` is the most-developed example
|
|
|
|
### Pipeline Design
|
|
|
|
1. **Profile before optimizing** — measure with `compression_stats` first
|
|
2. **Prefer composition over reimplementation** — extend Caveman rules before writing a new engine
|
|
3. **Document the order rationale** — comment why engine A before engine B
|
|
4. **Test at all 3 intensity levels** — `lite` is fast but lossy, `ultra` is slow but precise
|
|
|
|
---
|
|
|
|
## Reference: Built-in Engines
|
|
|
|
| Engine ID | Stackable | Default stackPriority | Targets |
|
|
| -------------------- | --------- | --------------------- | ----------------------------------- |
|
|
| `lite` | Yes | 5 | messages, tool_results |
|
|
| `rtk` | Yes | 10 | tool_results |
|
|
| `standard` (caveman) | Yes | 20 | messages, tool_results, code_blocks |
|
|
| `aggressive` | Yes | 30 | messages |
|
|
| `ultra` | Yes | 40 | messages, code_blocks |
|
|
|
|
### See Also
|
|
|
|
- [COMPRESSION_GUIDE.md](./COMPRESSION_GUIDE.md) — Pipeline overview
|
|
- [COMPRESSION_ENGINES.md](./COMPRESSION_ENGINES.md) — Engine registry reference
|
|
- [COMPRESSION_RULES_FORMAT.md](./COMPRESSION_RULES_FORMAT.md) — Rule format spec
|
|
- [COMPRESSION_LANGUAGE_PACKS.md](./COMPRESSION_LANGUAGE_PACKS.md) — Language pack details
|
|
- [RTK_COMPRESSION.md](./RTK_COMPRESSION.md) — RTK engine and custom filters
|
|
- Source: `open-sse/services/compression/` (117 files, ~250KB)
|