Async Bridge

Safely call async code from sync, and sync code from async, without deadlocking the event loop.

The async bridge lets your tools and callbacks move between sync and async without crashing the event loop.

Quick Start

1. From a sync tool

   Use run_coroutine_from_any_context to call async code from a sync tool:

   from praisonaiagents import Agent
   from praisonaiagents.utils.async_bridge import run_coroutine_from_any_context
   import httpx
   
   async def _fetch(url: str) -> str:
       async with httpx.AsyncClient() as client:
           return (await client.get(url)).text[:500]
   
   def fetch_sync(url: str) -> str:
       """Sync tool that safely reuses an async HTTP client."""
       return run_coroutine_from_any_context(_fetch(url))
   
   agent = Agent(
       name="Researcher",
       instructions="Fetch and summarise web pages",
       tools=[fetch_sync],
   )
   agent.start("Summarise https://example.com")
   
2. From an async tool

   Use run_sync_in_executor to call blocking code from an async tool without blocking the event loop:

   from praisonaiagents import Agent
   from praisonaiagents.utils.async_bridge import run_sync_in_executor
   import time
   
   def blocking_task(duration: int) -> str:
       time.sleep(duration)
       return f"Completed after {duration} seconds"
   
   async def async_tool(duration: int) -> str:
       """Async tool that offloads blocking work."""
       return await run_sync_in_executor(blocking_task, duration)
   
   agent = Agent(
       name="Worker",
       instructions="Handle blocking tasks efficiently",
       tools=[async_tool],
   )
   
3. Detecting the context

   Use is_async_context to create dual-mode helpers:

   from praisonaiagents.utils.async_bridge import is_async_context, run_coroutine_from_any_context
   import httpx
   
   async def _async_fetch(url: str) -> str:
       async with httpx.AsyncClient() as client:
           return (await client.get(url)).text
   
   def smart_fetch(url: str) -> str:
       """Context-aware fetch that works in both sync and async."""
       if is_async_context():
           raise RuntimeError("Use await smart_fetch_async(url) in async context")
       return run_coroutine_from_any_context(_async_fetch(url))
   
   async def smart_fetch_async(url: str) -> str:
       """Async version for use in async contexts."""
       return await _async_fetch(url)
   

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How It Works

The bridge probes for a running event loop using asyncio.get_running_loop(). If no loop exists, it safely creates one with asyncio.run(). If a loop is already running, it raises RuntimeError to prevent deadlocks.

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Configuration Options

Option	Type	Default	Description
timeout	float	300	Maximum seconds to wait for coroutine completion

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Common Patterns

Reusing async SDKs from sync tools

from praisonaiagents import Agent
from praisonaiagents.utils.async_bridge import run_coroutine_from_any_context
import aiofiles

async def _read_file_async(path: str) -> str:
    async with aiofiles.open(path) as f:
        return await f.read()

def read_file(path: str) -> str:
    """Sync wrapper for async file operations."""
    return run_coroutine_from_any_context(_read_file_async(path))

agent = Agent(
    name="FileReader",
    instructions="Process files efficiently",
    tools=[read_file],
)

Offloading blocking calls from async tools

import subprocess
from praisonaiagents.utils.async_bridge import run_sync_in_executor

async def run_command(cmd: str) -> str:
    """Run shell command without blocking the event loop."""
    def _run():
        return subprocess.check_output(cmd, shell=True, text=True)
    
    return await run_sync_in_executor(_run)

Context-aware dual-mode helper

from praisonaiagents.utils.async_bridge import is_async_context, run_coroutine_from_any_context

def universal_helper(data):
    """Works in both sync and async contexts."""
    if is_async_context():
        raise RuntimeError("Use await universal_helper_async(data) in async context")
    
    async def _process():
        # async processing logic
        await asyncio.sleep(0.1)
        return f"Processed: {data}"
    
    return run_coroutine_from_any_context(_process())

---

Best Practices

Prefer await when you're already async

Calling run_coroutine_from_any_context inside an async def raises RuntimeError by design. If you’re in a coroutine, use await instead:

# Good
async def my_async_tool():
    result = await my_coroutine()
    
# Bad - will raise RuntimeError
async def my_async_tool():
    result = run_coroutine_from_any_context(my_coroutine())

Don't wrap everything

Only wrap at the true sync/async boundary. Avoid creating unnecessary bridge calls in the middle of your call stack:

# Good - bridge at the boundary
def sync_tool():
    return run_coroutine_from_any_context(async_logic())

# Bad - unnecessary nesting
def sync_tool():
    def inner():
        return run_coroutine_from_any_context(async_logic())
    return inner()

Set a sensible timeout

The default 300 seconds is large for most use cases. Tighten for latency-critical tools:

# Good for quick operations
result = run_coroutine_from_any_context(quick_api_call(), timeout=10)

# Good for long operations
result = run_coroutine_from_any_context(model_training(), timeout=3600)

Check is_async_context() for dual-mode helpers

When building utilities that work in both sync and async contexts, check the context first:

def smart_helper():
    if is_async_context():
        raise RuntimeError("Use await smart_helper_async() in async context")
    return run_coroutine_from_any_context(async_implementation())

async def smart_helper_async():
    return await async_implementation()

---

Used by

The following synchronous APIs route through run_sync() and therefore honour PRAISONAI_RUN_SYNC_TIMEOUT consistently:

• praisonai.bots.WebhookApproval.request_approval_sync()
• praisonai.bots.HTTPApproval.request_approval_sync()
• praisonai.integrations.get_available_integrations()
• All ~77 wrapper-side run_sync call sites (gateway, a2u, mcp_server, scheduler) — see PR #1583 for the full list.

These sync wrappers now raise RuntimeError("run_sync() cannot be called from a running event loop; await the coroutine directly instead.") when called from inside an active asyncio loop. Previously they would silently spawn a worker thread. If you call any of these from async code, switch to await request_approval(...) (or the equivalent async method) directly. This is a deliberate fail-fast change — the silent thread spawn was masking architectural bugs in multi-agent setups.

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Troubleshooting

RuntimeError: run_coroutine_from_any_context() cannot be called from async context

You’re trying to use the bridge inside a coroutine. Use await instead:

# Bad
async def my_coroutine():
    return run_coroutine_from_any_context(other_coroutine())

# Good
async def my_coroutine():
    return await other_coroutine()

asyncio.run() cannot be called from a running event loop

This error used to leak from SDK internals before the async bridge was implemented. If you see this on current versions, upgrade to the latest release.

PermissionError in approval system

The approval system now fails fast in async contexts. Configure a non-console backend:

from praisonaiagents.approval import get_approval_registry, WebhookBackend

# Configure for async compatibility
get_approval_registry().set_backend(WebhookBackend(url="http://localhost:8080/approve"))

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Related

Async Agents Guide

Thread Safety & Concurrency