phoson-engine-minimal

Minimal Python runtime for the Phoson autonomous-agent platform

🔥 Open Source — Built for developers who want full control over their AI agents.

📋 Table of Contents

• What this project is
• Why Phoson?
• Features
• High-level architecture
• Repository map
• Core modules
  • phoson_llm — LLM normalization layer
  • phoson_agent — Agent orchestration
  • phoson_agent.sessions — Conversation persistence
  • phoson_cli — Interactive REPL
• 🚀 Quick Start
• Installation
  • Standalone binaries (no Python required)
• Development setup
• Run checks locally
• Environment variables
• Usage examples
  • Minimal agent usage
  • Define a tool
  • Interactive CLI
• CI and security workflows
• Commit message format
• Roadmap
• Contributing
• License
• Support

🤔 What this project is

phoson-engine-minimal is the core runtime behind the Phoson autonomous-agent platform. It's a lightweight, framework-free Python implementation that gives you complete control over your AI agents without the bloat of heavy frameworks.

Unlike other agent frameworks (LangChain, LangGraph, etc.), Phoson is built from scratch using provider SDKs directly, with a custom ReAct loop designed for:

• 🔄 Streaming behavior — Token-by-token events for real-time UIs
• 🔧 Tool-call orchestration — Full control over tool execution
• 💰 Cost accounting — Track spend per run with built-in pricing
• 👁️ Observability — RunStep events and typed event streams
• 🌳 Session trees — Branchable conversation history (not linear!)
• ⌨️ Interactive REPL — Debug and iterate on agents interactively

🎯 Why Phoson?

✨ Features

🏗️ High-level architecture

flowchart LR
    U[App / CLI / API] --> AE[AgentEngine\nphoson_agent]
    AE --> MW[Middleware Hooks]
    AE --> T[Registered Tools]
    AE --> S[ConversationTree + Storage]
    AE --> C[BaseLLMChat Contract]
    C --> OA[OpenAIChat]
    C --> AN[AnthropicChat]
    OA --> P1[OpenAI / OpenRouter / Ollama]
    AN --> P2[Anthropic]
    OA --> E[Typed LLM Events]
    AN --> E
    E --> AE
    AE --> R[Agent Events + RunResult]

Runtime loop (tool call cycle)

sequenceDiagram
    participant Client
    participant Engine as AgentEngine
    participant LLM as LLM Adapter
    participant Tool as Tool Handler

    Client->>Engine: run(messages, config)
    Engine->>LLM: stream(history, config, tools)
    LLM-->>Engine: TokenEvent / ReasoningTokenEvent
    LLM-->>Engine: ToolCallEvent
    Engine->>Tool: execute(args)
    Tool-->>Engine: result/error
    Engine->>LLM: continue with ToolResultBlock
    LLM-->>Engine: UsageEvent + LLMDoneEvent
    Engine-->>Client: AgentRunResult

🗺️ Repository map

phoson-engine-minimal/
├── phoson_llm/           # LLM normalization layer (adapters + schemas + pricing)
├── phoson_agent/         # ReAct agent loop, tools, middleware, sessions
├── phoson_cli/           # Interactive CLI (TUI + classic REPL) for agent sessions
├── phoson_plugin_*/      # Official plugins (checkpoint, mcp, memory, monitor)
├── examples/             # Runnable engine/plugin/MCP usage examples
├── bench/                # Benchmarks (run_bench.py + tasks)
├── scripts/              # Installers, uninstall and dev/bench scripts
├── assets/               # README visuals (screenshots, demo GIFs, VHS tapes)
├── tests/                # Unit/integration tests for all layers
├── docs/api/             # Per-package API documentation
├── docs/cli/             # Deep-dive CLI documentation (keybindings, caching, …)
├── .github/workflows/    # CI, release, binaries and security automation
├── ROADMAP.md            # Project roadmap
└── pyproject.toml        # Project metadata, dependencies, tooling config

📦 Core modules

phoson_llm — LLM normalization layer

Provider adapters return a single typed event stream (LLMEvent subclasses):

Supported providers:

All of them are available via the build_chat() factory, e.g. build_chat("openrouter"), and expose the same stream() event contract.

Pricing module (phoson_llm.pricing) provides calculate_cost() for provider-level USD usage.

phoson_agent — Agent orchestration

Stateless-by-run orchestration over message history with tool execution:

• AgentEngine — Main entry point for running agents (async and sync)
• @tool decorator — Transform Python functions into AgentTool definitions with JSON Schema
• AgentMiddleware — Hooks for pre/post processing (LLM calls, tool execution)
• AgentContext — Shared state across middleware and tools

phoson_agent.sessions — Conversation persistence

• ConversationTree — Branchable conversation structure (not linear)
• ConversationNode — Individual node with messages, children, label
• JsonlStorage — JSONL-backed session storage (local file)
• SessionMeta — Session metadata (id, message_count, created_at, updated_at)

phoson_cli — Interactive REPL

Command-line interface for interactive agent sessions:

• PhosonApp — Full-screen TUI (default) with scrollable chat pane, pickers and overlays
• PhosonRepl — Classic line-by-line REPL (--classic), retained for debugging
• ~30 slash commands (sessions, model/provider, compaction, MCP, permissions, metrics…) — see Interactive CLI
• Real-time streaming responses, one-shot mode for scripts/CI
• Session persistence, branching, and rewind

🚀 Quick Start

from phoson_agent import AgentEngine
from phoson_llm import build_chat
from phoson_llm.schemas import Message, ModelConfig

engine = AgentEngine(chat=build_chat("openai"))

result = engine.run_sync(
    messages=[Message(role="user", content="Summarize this project in one line")],
    config=ModelConfig(model="openai/gpt-4o-mini", max_tokens=128),
)

print(result.final_content)
print(result.total_cost_usd, result.total_credits)

Or run the interactive CLI:

uv run phoson-cli

Run the setup wizard to configure provider credentials and defaults:

uv run phoson-cli --setup

📥 Installation

# Clone the repository
git clone https://github.com/phoson-lat/phoson-engine-minimal.git
cd phoson-engine-minimal

# Install dependencies
uv sync --dev --locked

# Install git hooks
uv run pre-commit install --install-hooks
uv run pre-commit install --hook-type commit-msg
uv run pre-commit install --hook-type pre-push

Standalone binaries (no Python required)

Prebuilt phoson-cli binaries are attached to each GitHub release — no Python interpreter or uv/pip needed (issue #93):

Download the asset for your platform, make it executable (Unix), and run:

chmod +x phoson-cli
./phoson-cli --setup     # configure credentials, then just: phoson-cli

--self-update inside a binary points back to the Releases page (the binary is a one-file bundle with no package metadata to upgrade).

🛠️ Development setup

Install dependencies

uv sync --dev --locked

Install git hooks

uv run pre-commit install --install-hooks
uv run pre-commit install --hook-type commit-msg
uv run pre-commit install --hook-type pre-push

✅ Run checks locally

uv sync --dev --all-extras   # --all-extras is needed for pyright (provider SDK stubs)
uv run ruff format --check .
uv run ruff check .
uv run pyright
uv run python -m compileall phoson_llm phoson_agent phoson_cli
uv run pytest -q

🔐 Environment variables

Set the variables for the providers you use (the adapter reads the default when no api_key is passed):

# Cloud providers
OPENAI_API_KEY=
ANTHROPIC_API_KEY=
OPENROUTER_API_KEY=
GEMINI_API_KEY=
MISTRAL_API_KEY=
GROQ_API_KEY=
XAI_API_KEY=
DEEPSEEK_API_KEY=
TOGETHER_API_KEY=
PERPLEXITY_API_KEY=
NVIDIA_API_KEY=
FIREWORKS_API_KEY=
COHERE_API_KEY=
GITHUB_TOKEN=

# Azure OpenAI
AZURE_OPENAI_ENDPOINT=
AZURE_OPENAI_API_KEY=
AZURE_OPENAI_DEPLOYMENT=

# AWS Bedrock (plus standard AWS credentials: AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY)
AWS_DEFAULT_REGION=us-east-1

Local servers (Ollama, LM Studio, vLLM) need no API key — just the right base_url.

Runtime / CLI

PHOSON_RUN_BUDGET_SECONDS=600   # one-shot wall-clock cap (s); 0 = unlimited

PHOSON_RUN_BUDGET_SECONDS caps the whole run in non-interactive mode (one-shot / piped stdin) — interactive runs have no such cap (Esc is the escape). When hit, the run exits cleanly with code 124. It is a run-level budget, separate from the per-tool bash timeout (which I-127 deliberately left uncapped for interactive use).

💻 Usage examples

Minimal agent usage

from phoson_agent import AgentEngine
from phoson_llm import build_chat
from phoson_llm.schemas import Message, ModelConfig

engine = AgentEngine(chat=build_chat("openai"))

result = engine.run_sync(
    messages=[Message(role="user", content="Summarize this project in one line")],
    config=ModelConfig(model="openai/gpt-4o-mini", max_tokens=128),
)

print(result.final_content)
print(result.total_cost_usd, result.total_credits)

Define a tool

import ast
import operator

from phoson_agent import tool


@tool
def calculate(expression: str) -> str:
    """Safely evaluate a basic arithmetic expression like "2 + 2 * 10"."""

    def _eval(node: ast.AST):
        match node:
            case ast.Expression(body=value):
                return _eval(value)
            case ast.Constant():
                return node.value
            case ast.BinOp(left=left, op=op, right=right):
                ops = {
                    ast.Add: operator.add,
                    ast.Sub: operator.sub,
                    ast.Mult: operator.mul,
                    ast.Div: operator.truediv,
                }
                if type(op) not in ops:
                    raise ValueError(f"Unsupported operator: {type(op).__name__}")
                return ops[type(op)](_eval(left), _eval(right))
            case ast.UnaryOp(op=op, operand=value) if isinstance(op, ast.USub):
                return -_eval(value)
        raise ValueError(f"Unsupported expression: {expression!r}")

    return str(_eval(ast.parse(expression, mode="eval")))

⚠️ Never use eval()/exec() on model-generated input — treat LLM output as untrusted and validate or sandbox every tool argument.

Interactive CLI

uv run phoson-cli          # full-screen TUI (default)
uv run phoson-cli --setup  # first-run wizard: credentials + defaults

One-shot mode (no REPL, no session — for scripts and CI): the final answer goes to stdout, exit code 0 on success / 1 on agent error / 124 when the run hits its wall-clock budget. Non-interactive runs carry the same Offload → Summarizer → Permission chain as the REPL, and an ask-level tool fails closed (refused, not run).

phoson-cli "fix the failing tests"     # positional task
phoson-cli -p "summarize this repo"    # --print flag
echo "explain the CI failure" | phoson-cli   # piped stdin
# Wall-clock budget for the whole run (one-shot only): default 600s,
# 0 = unlimited. A hung command can't be escaped with Esc here.
PHOSON_RUN_BUDGET_SECONDS=300 phoson-cli -p "long task"

Command-line flags (one-off overrides; they never touch ~/.phoson/config.toml):

The full-screen TUI is the default interactive front end; --classic launches the classic REPL (Rich scrollback) — useful for debugging and on terminals without full-screen support. When TERM is unset or dumb, the classic REPL is selected automatically.

Slash commands (type /help inside the REPL for the live list):

Plugins can register additional slash commands (see docs/plugins.md).

Behavior highlights — one-line summaries; deep dives in docs/cli/:

• Rewind — double-Esc while idle jumps the conversation back to an earlier message; Ctrl+Z undoes the jump → docs/cli/rewind.md
• Key bindings — remappable via [keys] in ~/.phoson/config.toml (validated at startup); Ctrl+T toggles the live reasoning view → docs/cli/keybindings.md
• Text selection & links — Shift+Drag selects chat text natively; markdown links render as clickable OSC 8 hyperlinks → docs/cli/mouse-and-links.md
• @file mentions — type @ and the composer fuzzy-filters repo paths; on send, files are inlined (text) or become native media blocks (images/audio/video/pdf), same as /attach.
• Prompt caching — cacheable prefix by default (Anthropic cache_control + OpenRouter sticky routing); cached tokens surface in /status and /tokens, typically cutting long-session prompt cost 50–90% → docs/cli/prompt-caching.md
• Permissions — per-tool allow/ask/deny + allow-patterns in ~/.phoson/permissions.json; the policy applies to sub-agents and one-shot runs too, and non-interactive runs fail closed → docs/cli/permissions.md
• Project memory — AGENTS.md (or CLAUDE.md) from the repo root to your CWD is injected into the system prompt; /agents-md lists what loaded → docs/cli/agents-md.md
• Skills — SKILL.md packages indexed at one line; the agent loads the full body on demand without busting the prompt cache → docs/cli/skills.md
• Models config — ~/.phoson/models.json for model overrides and non-sensitive provider settings; light/dark theme auto-detection → docs/cli/models-config.md
• Auto-compaction — structured handoff summaries keep long sessions inside the context window; /compact previews before applying → docs/cli/compaction.md
• UI — scrollable chat pane, multiline composer, overlay pickers, animated activity line (Thinking… → Composing tool… → Running tool…) → docs/cli/ui.md

Self-update: at launch the CLI checks PyPI in the background (at most once every 24 h). When a newer release exists it shows a dim one-line hint — ⬆ v0.x.y available — /update — in the TUI header (full-screen) or the prompt line (classic). It never blocks first paint, input, or a run; one-shot mode is untouched. /update or --self-update install it.

🔒 CI and security workflows

• .github/workflows/ci.yml: Format check, lint, smoke compile, and tests on PRs and pushes to main.
• .github/workflows/publish.yml: Build sdist/wheel and publish to PyPI on release.
• .github/workflows/release-binaries.yml: Build standalone phoson-cli binaries (Linux/macOS/Windows) attached to each GitHub release.
• .github/workflows/security.yml: Dependency audit and secret scan on PRs, pushes to main, and weekly schedule.

📝 Commit message format

Conventional Commits are enforced through a commit-msg hook.

Examples:

feat: add streaming chat abstraction
fix: handle unknown model pricing fallback
chore: update pre-commit hook versions

Common types: feat, fix, docs, refactor, test, chore, ci

🗓️ Roadmap

For the project roadmap see ROADMAP.md, and per-package API documentation under docs/api/.

🤝 Contributing

Contributions are welcome! Here's how you can help:

1. Fork the repository
2. Create a feature branch: git checkout -b feature/amazing-feature
3. Commit your changes: git commit -m 'feat: add amazing feature'
4. Push to the branch: git push origin feature/amazing-feature
5. Open a Pull Request

🌐 Language policy: everything in this repository must be in English — documentation, docstrings, code comments, commit messages, issue titles and bodies, and PR descriptions. This keeps the project accessible to contributors worldwide. If you're more comfortable writing in another language, draft your changes in a branch and maintainers will help polish the English before merge.

Please read CONTRIBUTING.md for details on our code of conduct and development process.

Ideas for contributions

• 🆕 Add new LLM providers (20+ already supported — see the table above)
• 🔧 Improve tool execution (batching, retries, caching)
• 📊 Extend observability: the phoson_plugin_otel plugin already traces runs as OTel span trees with a local trace-file sink — real OTLP export (slice 2) and Langfuse remain open
• 🖥️ Build a web-based REPL or playground
• 📚 Improve documentation and examples

📄 License

This project is licensed under the MIT License — see the LICENSE file for details.

MIT License

Copyright (c) 2024 Phoson

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

💬 Support

• Issues: GitHub Issues for bug reports
• Discussions: GitHub Discussions for questions
• Documentation: See docs/api/ for per-package API notes
• Website: https://phoson.lat
• SDK Docs: https://phoson.lat/docs

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