boost-modules

---
name: boost-modules
description: Create custom modules for Harbor Boost, an optimizing LLM proxy. Use when building Python modules that intercept/transform LLM chat completions—reasoning chains, prompt injection, structured outputs, artifacts, or custom workflows. Triggers on requests to create Boost modules, extend LLM behavior via proxy, or implement chat completion middleware.
---

# Harbor Boost Custom Modules

Boost modules are Python files that intercept chat completions and can transform, augment, or replace LLM responses.

## Module Structure

```python
ID_PREFIX = 'mymodule'  # Models prefixed with this trigger the module

async def apply(chat, llm):
    # chat: conversation history (linked list of ChatNodes)
    # llm: interface to downstream LLM and output streaming
    await llm.stream_final_completion()

Quick Reference

Output Methods

# Stream text to client
await llm.emit_message("Hello")

# Status indicator (formatted per HARBOR_BOOST_STATUS_STYLE)
await llm.emit_status("Processing...")

# Internal completion (not streamed to client)
result = await llm.chat_completion(prompt="Summarize: {text}", text=content, resolve=True)

# Streamed completion (visible to client)
await llm.stream_chat_completion(prompt="Explain {topic}", topic="quantum")

# Final completion (always streamed, even when intermediate output disabled)
await llm.stream_final_completion()
await llm.stream_final_completion(prompt="Reply to: {msg}", msg=chat.tail.content)

# Structured output
from pydantic import BaseModel, Field
class Response(BaseModel):
    answer: str = Field(description="The answer")
result = await llm.chat_completion(prompt="...", schema=Response, resolve=True)

# Artifacts (for clients like Open WebUI)
await llm.emit_artifact("<h1>Interactive content</h1>")

Chat Manipulation

# Read conversation
chat.text()           # Full conversation as string
chat.message          # Last user message content
chat.tail             # Last ChatNode
chat.tail.content     # Content of last message
chat.tail.role        # Role of last message
chat.history()        # List of messages from tail
chat.plain()          # List of ChatNodes from tail