axio-repl

Interactive REPL coding assistant powered by the axio agent framework. Works with any LLM backend via pluggable transports — bring your own API key.

Philosophy

axio-repl is an opinionated terminal agent that actually verifies its work. The system prompt encodes hard-won lessons from watching models cut corners:

• Stream everything, hide nothing. Every piece of information shown to the user — tool arguments, stdout/stderr, images, exit codes — must also be faithfully presented to the model. The model should see exactly what the user sees, so it can reason about the same reality. No summarizing, no truncating, no dropping context between what's displayed and what's sent back.
• Not tested — not done. The agent must run tests, re-read edited files, and observe actual results instead of assuming success from exit codes.
• Iterative UI review. When building or modifying UI, the agent captures real screenshots at multiple viewport sizes (desktop, tablet, mobile) via Playwright/Puppeteer, reads every screenshot through the model's vision, and critically lists visual defects. It repeats the screenshot → fix → re-screenshot loop until zero defects — no premature "looks good".
• Ground everything in project context. Read before editing. List the directory before guessing. Never refuse a safe request.
• Minimal edits. Don't reformat surrounding code, don't narrate tool calls. The user sees the full tool output in the terminal.

Features

• Pluggable transports — auto-detected from API keys via axio.transport entry points. Ships with support for OpenAI, Anthropic, Google (Gemini API & Vertex AI), Nebius, OpenRouter, and Codex.
• Runtime model switching — /model <query> to switch models mid-session without restarting. Capabilities (vision, reasoning, image generation) are re-evaluated and the system prompt adapts automatically.
• Streaming tool arguments — tool call fields appear incrementally as the model generates them, so you see what's happening before execution starts.
• Streaming tool output — shell command stdout/stderr streams line-by-line in real time instead of buffering until completion.
• Vision — read_file on images (PNG, JPG, GIF, WebP) and videos returns multimodal content blocks. The model sees the actual pixels, not a description.
• Image & video generation — when the Google transport is installed, generate_image and generate_video tools are available for Gemini Nano Banana / Veo models.
• AGENTS.md — workspace-level instructions loaded into the system prompt from an AGENTS.md file in the working directory.
• Multiline paste — pasting multi-line text into the prompt is handled gracefully with continuation markers (...).
• Graceful interruption — Ctrl-C cancels the running agent loop, preserving partial tool output in conversation context so the model knows what happened.
• Readline history — persisted across sessions in ~/.axio_repl_history.
• Single-prompt mode — pass a prompt as argument for scripting and non-interactive use.

Install

uv tool install axio-repl

To add optional transports:

uv tool install axio-repl --with axio-transport-anthropic
uv tool install axio-repl --with axio-transport-google

Or within the monorepo workspace:

uv run axio-repl

Usage

# Interactive REPL (auto-detects transport from API keys)
axio-repl

# Single prompt (non-interactive)
axio-repl "list the files in this project"

# Explicit transport and model
axio-repl --transport anthropic --model claude-sonnet-4-20250514

# Google Gemini
axio-repl --transport google --model gemini-3.1-pro-preview

# Custom temperature and iteration limit
axio-repl --temperature 0.5 --max-iterations 100

REPL Commands

Tools

Transports

Transports are discovered via the axio.transport entry point group. The REPL picks the first transport whose required environment variable is set:

Use --transport <name> to force a specific transport regardless of env vars.

Capability-Aware System Prompt

The system prompt adapts based on the selected model's declared capabilities:

• Vision — unlocks instructions to read_file images and do screenshot-based UI review.
• Reasoning — notes that extended thinking is available.
• Image generation — enables inline image generation guidance.
• Video — enables read_file for video content.
• Tool use — gates all tool-related rules (edit workflow, testing, verification).

This means switching from a text-only model to a vision model mid-session (via /model) automatically updates what the agent is instructed to do.

Architecture

┌─────────────┐     ┌───────────┐     ┌──────────────────┐
│  axio-repl  │────▶│   axio    │────▶│    transport      │
│  (terminal  │     │  (agent   │     │  (anthropic /     │
│   UI, I/O)  │     │   loop)   │     │   google / openai │
└─────────────┘     └───────────┘     │   / nebius / ...)  │
                          │           └──────────────────┘
                    ┌─────┴─────┐
                    │ tools     │
                    │ (local fs │
                    │  + shell) │
                    └───────────┘

• axio-repl owns the terminal UI: readline, event rendering, REPL commands.
• axio runs the agent loop: dispatch tools, manage conversation context, handle cancellation.
• transports handle LLM communication — message conversion, streaming, model registries.
• axio-tools-local provides the file and shell tools.