Vex Python SDK

The reliability layer for AI agents in production. Trace executions, enforce guardrails, and monitor agent behavior — with zero changes to your agent's core logic.

Installation

pip install vex-sdk

Quick Start

from vex import Vex, VexConfig

guard = Vex(
    api_key="your-api-key",
    config=VexConfig(api_url="https://api.tryvex.dev"),
)

# 1. Decorator — auto-capture input/output/latency
@guard.watch(agent_id="my-agent")
def run_agent(prompt: str) -> str:
    return call_llm(prompt)

# 2. Context manager — fine-grained step tracing
with guard.trace(agent_id="my-agent", task="summarize") as ctx:
    result = call_llm(prompt)
    ctx.step("llm", "summarize", input=prompt, output=result)
    ctx.record(result)

Sync Verification

Run inline verification with pass/flag/block decisions. When the verification engine determines an output is unreliable, the SDK raises VexBlockError so your application can handle it gracefully.

from vex import Vex, VexConfig, VexBlockError

guard = Vex(
    api_key="your-api-key",
    config=VexConfig(
        mode="sync",
        api_url="https://api.tryvex.dev",
    ),
)

@guard.watch(agent_id="my-agent")
def run_agent(prompt: str) -> str:
    return call_llm(prompt)

try:
    result = run_agent("Summarize this document")
    # result is a VexResult with confidence score
    print(result.output, result.confidence, result.action)
except VexBlockError as e:
    print(f"Blocked: confidence={e.result.confidence}")

Correction Cascade

Automatically correct unreliable outputs instead of blocking. When enabled, the verification engine attempts to fix issues and returns the corrected output.

guard = Vex(
    api_key="your-api-key",
    config=VexConfig(
        mode="sync",
        correction="cascade",          # Enable correction
        transparency="transparent",    # Include correction details in result
    ),
)

result = run_agent("Summarize this document")
if result.corrected:
    print(f"Output was corrected: {result.output}")
    print(f"Original: {result.original_output}")

Session Tracking & Conversation History

Group related executions into sessions with automatic conversation history for multi-turn verification (hallucination, drift, coherence).

session = guard.session(agent_id="chat-bot")

# Turn 1
with session.trace(task="greeting", input_data="Hello") as ctx:
    response = call_llm("Hello")
    ctx.record(response)

# Turn 2 — conversation history from turn 1 is sent automatically
with session.trace(task="follow-up", input_data="Tell me more") as ctx:
    response = call_llm("Tell me more")
    ctx.record(response)

The session maintains a sliding window of conversation history (configurable via conversation_window_size), enabling cross-turn verification checks like self-contradiction detection and goal drift analysis.

Configuration

from vex import VexConfig
from vex.models import ThresholdConfig

VexConfig(
    mode="async",               # "async" (fire-and-forget) or "sync" (inline verification)
    correction="none",          # "none" or "cascade" (auto-correct unreliable outputs)
    transparency="opaque",      # "opaque" or "transparent" (include correction details)
    api_url="https://api.tryvex.dev",
    flush_interval_s=1.0,       # Batch flush interval (async mode)
    flush_batch_size=50,        # Max events per flush batch
    timeout_s=2.0,              # HTTP timeout for API calls
    conversation_window_size=10,  # Max conversation turns retained per session
    confidence_threshold=ThresholdConfig(
        pass_threshold=0.8,     # >= 0.8 → pass
        flag_threshold=0.5,     # >= 0.5 → flag (warning logged)
        block_threshold=0.3,    # < 0.3 → block (raises VexBlockError)
    ),
)

What's New in v0.3.0

• Rebranded to Vex: pip install vex-sdk, from vex import Vex, VexConfig
• Sync Verification: Inline pass/flag/block decisions via mode="sync" with configurable confidence thresholds
• Correction Cascade: Auto-correct unreliable outputs with correction="cascade", dual-timeout transport (2s verify / 12s correction), and transparent/opaque modes
• Conversation-Aware Verification: Multi-turn coherence, cross-turn hallucination detection, and goal drift analysis via automatic session history
• VexResult Model: Structured verification results with confidence, action, corrected, original_output, and corrections fields
• VexBlockError: Exception raised when verification blocks output, with the full VexResult attached
• ConversationTurn Model: First-class conversation turn representation for multi-turn agents

Requirements

• Python 3.9+
• Dependencies: httpx, pydantic (v2)

Documentation

Full documentation: docs.tryvex.dev

License

Apache 2.0 — see LICENSE for details.