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.
from praisonaiagents import Agentagent = Agent(name="fetcher", instructions="Fetch URLs safely from sync or async tools.")agent.start("Summarise https://example.com")
The user calls a sync tool that needs async I/O; the bridge runs the coroutine safely or surfaces a clear error if called from a running loop.
from praisonaiagents.utils.async_bridge import is_async_context, run_coroutine_from_any_contextimport httpxasync def _async_fetch(url: str) -> str: async with httpx.AsyncClient() as client: return (await client.get(url)).textdef 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)
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.
Calling run_coroutine_from_any_context inside an async def raises RuntimeError by design. If you’re in a coroutine, use await instead:
# Goodasync def my_async_tool(): result = await my_coroutine()# Bad - will raise RuntimeErrorasync 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 boundarydef sync_tool(): return run_coroutine_from_any_context(async_logic())# Bad - unnecessary nestingdef 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 operationsresult = run_coroutine_from_any_context(quick_api_call(), timeout=10)# Good for long operationsresult = 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()
praisonai._run_praisonai (added PR #1681) — boots the InteractiveRuntime on the persistent background loop. If you call PraisonAI.run() from inside a running event loop, you now get a clear RuntimeError instead of a silent deadlock.
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.PR #1692 — cancellation on timeout (May 2026). When a run_sync() call hits its timeout (default 300 s, or whatever PRAISONAI_RUN_SYNC_TIMEOUT is set to), the underlying coroutine is now actively cancelled on the background loop. The bridge waits up to 1 s for cancellation to propagate before re-raising TimeoutError. This means slow DB queries (SurrealDB, async MySQL), HTTP calls, and subprocess waits now release their connection / socket / pipe instead of leaking. Cancellation also fires on KeyboardInterrupt, SystemExit, and GeneratorExit.
The wrapper-layer bridge (praisonai._async_bridge) creates its
background loop lazily on the first run_sync() call. Pure imports
do not allocate a loop or thread. Calling the module-level shutdown() before any
run_sync() is a safe no-op — it only affects the shared default bridge, not any AsyncBridge() instances you create yourself.
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.
Symptom
Cause
Resolution
TimeoutError raised but you also see your coroutine’s finally: block run after the exception
Expected: cancellation propagated, cleanup ran.
No action needed; this is the new PR #1692 behaviour.
Test reference:praisonai/tests/unit/test_async_bridge.py::TestBridgeIntegration::test_timeout_cancels_coroutine_and_runs_finally — quote this in the page so users can verify the behaviour locally.
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 compatibilityget_approval_registry().set_backend(WebhookBackend(url="http://localhost:8080/approve"))
The wrapper layer provides a module-level run_sync() for CLI scripts and single-tenant servers, plus a public AsyncBridge class when you need an isolated loop per tenant or service.
Module-level (default)
Per-instance AsyncBridge
from praisonai._async_bridge import run_sync, shutdownasync def async_helper(data: str) -> str: await asyncio.sleep(0.1) return f"Processed: {data}"def sync_entry_point(data: str) -> str: return run_sync(async_helper(data), timeout=60)import atexitatexit.register(shutdown) # shuts down ONLY the shared default bridge
from praisonai._async_bridge import AsyncBridgebridge = AsyncBridge() # per-tenant / per-service instanceasync def fetch(url: str) -> str: ...result = bridge.run_sync(fetch("https://example.com"), timeout=10)bridge.shutdown() # only this bridge — not the shared default
Multi-tenant gateway (loop scoped to tenant lifecycle)
—
✅
Embedding PraisonAI inside another async framework
—
✅
Tests needing clean shutdown without affecting others
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✅
API Reference:
Class / Function
Signature
Description
AsyncBridge
class AsyncBridge
Per-instance async runner; create one per tenant or service.
AsyncBridge.run_sync
(self, coro, *, timeout=300) -> T
Run a coroutine on this bridge’s background loop.
AsyncBridge.shutdown
(self, timeout=5.0, *, permanent=False) -> None
Cancel pending tasks and stop this bridge’s loop. With permanent=True, the bridge cannot be reused; later run_sync/submit raise RuntimeError. scoped_bridge() uses permanent=True for scope-owned bridges. PR #2122: releases the bridge lock before awaiting cancellation.
AsyncBridge.submit
(self, coro) -> concurrent.futures.Future
Submit without waiting; returns a concurrent.futures.Future.
AsyncBridge.get
(self) -> asyncio.AbstractEventLoop
Get (lazily spawn) the bridge’s event loop.
run_sync (module-level)
(coro, *, timeout=300) -> T
Routes through the shared default AsyncBridge. Behaviour unchanged.
shutdown (module-level)
() -> None
Shuts down only the shared default bridge. User-owned instances are untouched.
Environment:
PRAISONAI_RUN_SYNC_TIMEOUT: Default timeout in seconds (300)
Do not call run_sync from inside async def — use await instead. The function raises RuntimeError if called from within a running event loop to prevent deadlocks.The module-level shutdown() only stops the shared default bridge. Per-instance AsyncBridge objects must be shut down via bridge.shutdown() on each instance.
Servers and gateways that handle multiple concurrent sessions need each session to run on its own loop+thread binding. current_bridge() and scoped_bridge() provide ContextVar-backed per-session isolation so sessions never share a bridge accidentally.
Use scoped_bridge() inside any request handler that may run concurrently with other handlers — for example a FastAPI endpoint, a Starlette WebSocket handler, or a custom bot session dispatcher.
from praisonai._async_bridge import AsyncBridge, scoped_bridge, current_bridgeasync def handle_request(session_id: str, message: str) -> str: """Each concurrent request gets its own isolated bridge.""" bridge = AsyncBridge() async with scoped_bridge(bridge): # All code in this block sees `current_bridge()` as `bridge` result = bridge.run_sync(process_message(session_id, message)) return result
from praisonai._async_bridge import scoped_bridge, AsyncBridgebridge = AsyncBridge()async with scoped_bridge(bridge): # current_bridge() returns `bridge` inside this block ...# Outside: current_bridge() returns None (or the enclosing scope's bridge)
The context manager uses a ContextVar so nested scopes work correctly in async tasks and threads — each concurrent task sees only its own bridge.
When scoped_bridge() creates the bridge for you (no argument), it shuts down with permanent=True on exit. If code tries to call run_sync or submit on that bridge afterward, you get:RuntimeError: AsyncBridge has been shut down and cannot be reused; this usually means a context outlived its scoped_bridge() blockThat guard stops an orphaned loop and thread from outliving the scope that owned them. The shared default bridge always shuts down with permanent=False.
from praisonaiagents import Agentfrom praisonai._async_bridge import scoped_bridge, run_syncdef handle_session(session_id: str, prompt: str) -> str: with scoped_bridge() as bridge: data = run_sync(fetch_session_data(session_id)) agent = Agent(name="Assistant", instructions=f"Context: {data}") return agent.start(prompt) # bridge.shutdown(permanent=True) ran automatically — do not reuse `bridge` here
With no argument, scoped_bridge() creates a fresh bridge and tears it down with permanent=True when the with block ends. Internal code that calls module-level run_sync() inside the block uses the scoped bridge via contextvars — no import changes required.
current_bridge() returns the bridge bound to the current async task, or None when no scope is active. Use it to inspect which bridge is in use without passing it explicitly through call stacks.
from praisonai._async_bridge import current_bridgedef my_util(): bridge = current_bridge() if bridge is None: raise RuntimeError("No scoped bridge active — wrap with scoped_bridge()") return bridge.run_sync(some_coroutine())
Context manager. Binds a per-scope bridge via ContextVar. With None, creates and owns a fresh bridge (shut down with permanent=True on exit). With a caller-provided bridge, the caller retains lifecycle ownership.
current_bridge
() -> AsyncBridge
Returns the bridge bound by an enclosing scoped_bridge() block, else the shared default.