synth-ai 0.7.13

Serverless Posttraining for Agents - Core AI functionality and tracing

Synth

Prompt Optimization

Use the sdk in Python (uv add synth-ai) and Rust (beta) (cargo add synth-ai), or hit our serverless endpoints in any language

Average accuracy on LangProBe prompt optimization benchmarks.

Demo Notebooks (Colab)

• GEPA Banking77 Prompt Optimization
• GEPA Crafter VLM Verifier Optimization
• GraphGen Image Style Matching

Highlights

• 🎯 GEPA Prompt Optimization - Automatically improve prompts with evolutionary search. See 70%→95% accuracy gains on Banking77, +62% on critical game achievements
• 🔍 Zero-Shot Verifiers - Fast, accurate rubric-based evaluation with configurable scoring criteria
• 🧬 GraphGen - Train custom verifier graphs optimized for your specific workflows. Train custom pipelines for other tasks
• 🚀 No Code Changes - Wrap existing code in a FastAPI app and optimize via HTTP. Works with any language or framework
• ⚡️ Local Development - Run experiments locally with tunneled task apps. No cloud setup required
• 🗂️ Multi-Experiment Management - Track and compare prompts/models across runs with built-in experiment queues

Getting Started

SDK (Python)

pip install synth-ai==0.7.5
# or
uv add synth-ai

SDK (Rust - Beta)

cargo add synth-ai

TUI (Homebrew)

brew install synth-laboratories/tap/synth-ai-tui
synth-ai-tui

The TUI provides a visual interface for managing jobs, viewing events, and monitoring optimization runs.

OpenCode Skills (Synth API)

The Synth-AI TUI integrates with OpenCode and ships a synth-api skill.

# List packaged skills shipped with synth-ai
uvx synth-ai skill list

uvx synth-ai skill install synth-api --dir ~/custom/opencode/skill

LocalAPI Deploy (Cloud)

Deploy a LocalAPI with a Dockerfile and get a stable task_app_url:

export SYNTH_API_KEY=sk_live_...
synth localapi deploy \
  --name my-localapi \
  --app my_module:app \
  --dockerfile ./Dockerfile \
  --context . \
  --wait

Use the emitted task_app_url in training configs. Harbor auth uses SYNTH_API_KEY as the task app API key.

Tunnels

Synth optimization jobs need HTTPS access to your local task app. Two tunnel backends are available:

SynthTunnel (Recommended)

Relay-based tunnel — no external binary required, supports 128 concurrent requests:

from synth_ai.core.tunnels import TunneledLocalAPI

tunnel = await TunneledLocalAPI.create(local_port=8001, api_key="sk_live_...")
print(tunnel.url)            # https://st.usesynth.ai/s/rt_...
print(tunnel.worker_token)   # pass to job config

Use with optimization jobs:

job = PromptLearningJob.from_dict(
    config,
    task_app_url=tunnel.url,
    task_app_worker_token=tunnel.worker_token,
)

Cloudflare Quick Tunnel

Anonymous tunnel via trycloudflare.com — no API key needed:

from synth_ai.core.tunnels import TunneledLocalAPI, TunnelBackend

tunnel = await TunneledLocalAPI.create(
    local_port=8001,
    backend=TunnelBackend.CloudflareQuickTunnel,
)

Requires cloudflared installed (brew install cloudflared). Use task_app_api_key instead of worker_token when configuring jobs.

See the tunnels documentation for the full comparison.

Testing

Run the TUI integration tests:

cd tui/app
bun test

Synth is maintained by devs behind the MIPROv2 prompt optimizer.

Documentation

docs.usesynth.ai

Community

Join our Discord

GEPA Prompt Optimization (SDK)

Run GEPA prompt optimization programmatically:

import asyncio
import os
from synth_ai.sdk.api.train.prompt_learning import PromptLearningJob
from synth_ai.sdk.localapi import LocalAPIConfig, create_local_api

# Create a local task app: app = create_local_api(LocalAPIConfig(app_id="my_app", handler=my_handler))

# Create and submit a GEPA job
pl_job = PromptLearningJob.from_dict({
    "job_type": "prompt_learning",
    "config": {
        "prompt_learning": {
            "gepa": {
                "rollout": {"budget": 100},
                "population_size": 10,
                "generations": 5,
            }
        }
    },
    "task_app_id": "my_task_app",
})

pl_job.submit()
result = pl_job.stream_until_complete(timeout=3600.0)
print(f"Best score: {result.best_score}")

See the Banking77 demo notebook for a complete example with local task apps.

Online MIPRO (SDK, Ontology Enabled)

Run online MIPRO so rollouts call a proxy URL and rewards stream back to the optimizer. Enable ontology by setting MIPRO_ONT_ENABLED=1 and HELIX_URL on the backend, then follow the Banking77 online MIPRO notes.

import os
from synth_ai.sdk.optimization.policy import MiproOnlineSession

# Use the demo config shape from demos/mipro_banking77
mipro_config = {...}

session = MiproOnlineSession.create(
    config_body=mipro_config,
    api_key=os.environ["SYNTH_API_KEY"],
)
urls = session.get_prompt_urls()
proxy_url = urls["online_url"]

# Use proxy_url in your rollout loop, then report rewards
session.update_reward(
    reward_info={"score": 0.9},
    rollout_id="rollout_001",
    candidate_id="candidate_abc",
)

Graph Evolve: Optimize RLM-Based Verifier Graphs

Train a verifier graph with an RLM backbone for long-context evaluation. See the Image Style Matching demo for a complete Graph Evolve example:

from synth_ai.sdk.api.train.graph_evolve import GraphEvolveJob

# Train an RLM-based verifier graph
verifier_job = GraphEvolveJob.from_dataset(
    dataset="verifier_dataset.json",
    graph_type="rlm",
    policy_models=["gpt-4.1"],
    proposer_effort="medium",  # Use "medium" (gpt-4.1) or "high" (gpt-5.2)
    rollout_budget=200,
)
verifier_job.submit()
result = verifier_job.stream_until_complete(timeout=3600.0)

# Run inference with trained verifier
verification = verifier_job.run_verifier(
    trace=my_trace,
    context={"rubric": my_rubric},
)
print(f"Reward: {verification.reward}, Reasoning: {verification.reasoning}")

Zero-Shot Verifiers (SDK)

Run a built-in verifier graph with rubric criteria passed at runtime. See the Crafter VLM demo for verifier optimization:

import asyncio
import os
from synth_ai.sdk.graphs import VerifierClient

async def run_verifier():
    client = VerifierClient(
        base_url=os.environ["SYNTH_BACKEND_BASE"],
        api_key=os.environ["SYNTH_API_KEY"],
    )
    result = await client.evaluate(
        job_id="zero_shot_verifier_single",
        trace={"session_id": "s", "session_time_steps": []},
        rubric={
            "event": [{"id": "accuracy", "weight": 1.0, "description": "Correctness"}],
            "outcome": [{"id": "task_completion", "weight": 1.0, "description": "Completed task"}],
        },
        options={"event": True, "outcome": True, "model": "gpt-5-nano"},
        policy_name="my_policy",
        task_app_id="my_task",
    )
    return result

asyncio.run(run_verifier())

You can also call arbitrary graphs directly with the Rust SDK:

use serde_json::json;
use synth_ai::{GraphCompletionRequest, Synth};

#[tokio::main]
async fn main() -> Result<(), synth_ai::Error> {
    let synth = Synth::from_env()?;

    let request = GraphCompletionRequest {
        job_id: "zero_shot_verifier_rubric_single".to_string(),
        input: json!({
            "trace": {"session_id": "s", "session_time_steps": []},
            "rubric": {"event": [], "outcome": []},
        }),
        model: None,
        prompt_snapshot_id: None,
        stream: None,
    };

    let resp = synth.complete(request).await?;
    println!("Output: {:?}", resp.output);
    Ok(())
}