Fix 'make dev' failure in Windows environment#3236
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Pull request overview
This PR aims to make make dev work reliably on Windows by applying a Windows-compatible asyncio event loop policy and improving cross-platform startup scripting (Python selection + port readiness checks).
Changes:
- Add Windows-specific asyncio event loop policy configuration (both in gateway startup and via
sitecustomize.py). - Improve
serve.shPython interpreter selection to work better in Windows/Git Bash environments. - Extend
wait-for-port.shto detect listening ports viapowershell.exeon Windows.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.
| File | Description |
|---|---|
| scripts/wait-for-port.sh | Adds a PowerShell-based port listening probe for Windows. |
| scripts/serve.sh | Adds _pick_python() and uses it for Better Auth secret generation and uv-extras detection. |
| backend/sitecustomize.py | New module to set Windows asyncio event loop policy at Python startup. |
| backend/app/gateway/app.py | Adds Windows asyncio policy setup and modifies lifespan config/runtime initialization. |
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| # Initialize LangGraph runtime components (StreamBridge, RunManager, checkpointer, store) | ||
| async with langgraph_runtime(app, startup_config): | ||
| async with langgraph_runtime(app): | ||
| logger.info("LangGraph runtime initialised") |
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| # Load config and check necessary environment variables at startup | ||
| try: | ||
| startup_config = get_app_config() | ||
| apply_logging_level(startup_config.log_level) | ||
| app.state.config = get_app_config() | ||
| apply_logging_level(app.state.config.log_level) | ||
| logger.info("Configuration loaded successfully") |
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| if command -v powershell.exe >/dev/null 2>&1; then | ||
| if powershell.exe -NoProfile -ExecutionPolicy Bypass -Command "\$ErrorActionPreference='SilentlyContinue'; if (Get-NetTCPConnection -LocalPort $PORT -State Listen) { exit 0 } else { exit 1 }" >/dev/null 2>&1; then | ||
| return 0 |
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| _pick_python() { | ||
| local candidate | ||
| for candidate in python3 python py; do |
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| import asyncio | ||
| import sys | ||
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| def _configure_windows_event_loop_policy() -> None: | ||
| if sys.platform != "win32": | ||
| return | ||
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| selector_policy = getattr(asyncio, "WindowsSelectorEventLoopPolicy", None) | ||
| if selector_policy is None: | ||
| return | ||
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| if not isinstance(asyncio.get_event_loop_policy(), selector_policy): | ||
| asyncio.set_event_loop_policy(selector_policy()) | ||
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| _configure_windows_event_loop_policy() |
WillemJiang
reviewed
May 26, 2026
| async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]: | ||
| """Application lifespan handler.""" | ||
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| # Load config and check necessary environment variables at startup. |
Collaborator
There was a problem hiding this comment.
Please revert the change to the startup_config, which was just updated 5 days ago.
Collaborator
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@tanghang97 thanks for your contribution. Please review the comments and fix the lint errors. |
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| if command -v powershell.exe >/dev/null 2>&1; then | ||
| if powershell.exe -NoProfile -ExecutionPolicy Bypass -Command "\$ErrorActionPreference='SilentlyContinue'; if (Get-NetTCPConnection -LocalPort $PORT -State Listen) { exit 0 } else { exit 1 }" >/dev/null 2>&1; then | ||
| return 0 | ||
| fi | ||
| fi |
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| _pick_python() { | ||
| local candidate | ||
| for candidate in python3 python py; do | ||
| if command -v "$candidate" >/dev/null 2>&1 && "$candidate" -c 'import sys' >/dev/null 2>&1; then | ||
| printf '%s\n' "$candidate" | ||
| return 0 | ||
| fi | ||
| done | ||
| return 1 | ||
| } |
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| def _configure_windows_event_loop_policy() -> None: | ||
| """Use an event loop policy compatible with async psycopg on Windows.""" | ||
| if sys.platform != "win32": | ||
| return | ||
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| selector_policy = getattr(asyncio, "WindowsSelectorEventLoopPolicy", None) | ||
| if selector_policy is None: | ||
| return | ||
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| if not isinstance(asyncio.get_event_loop_policy(), selector_policy): | ||
| asyncio.set_event_loop_policy(selector_policy()) | ||
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| _configure_windows_event_loop_policy() |
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| """Process-wide Python startup customizations for local development.""" | ||
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| from __future__ import annotations | ||
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| import asyncio | ||
| import sys | ||
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| def _configure_windows_event_loop_policy() -> None: | ||
| if sys.platform != "win32": | ||
| return | ||
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| selector_policy = getattr(asyncio, "WindowsSelectorEventLoopPolicy", None) | ||
| if selector_policy is None: | ||
| return | ||
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| if not isinstance(asyncio.get_event_loop_policy(), selector_policy): | ||
| asyncio.set_event_loop_policy(selector_policy()) | ||
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| _configure_windows_event_loop_policy() |
WillemJiang
previously approved these changes
May 28, 2026
Collaborator
|
@tanghang97, could you take a look at the latest review message of Copilot? |
- Validate wait-for-port input and avoid PowerShell port interpolation - Require Python 3 in serve.sh launcher detection - Keep Windows event loop policy setup in sitecustomize only - Clarify sitecustomize process-wide backend behavior
github-actions
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added
risk:medium
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Summary
This PR resolves the issue where
make devcommand fails to start properly in Windows environments. The fix addresses compatibility problems with asyncio event loop policy and improves cross-platform support for the development server startup process.Changes Made
1. Event Loop Policy Configuration (
backend/app/gateway/app.py)_configure_windows_event_loop_policy()function to handle Windows-specific asyncio requirementsWindowsSelectorEventLoopPolicyfor better async/await compatibility on Windows2. Site Customization (
backend/sitecustomize.py)3. Script Improvements (
scripts/serve.sh,scripts/wait-for-port.sh)powershell.exefor port listening verificationTechnical Details
sys.platform == "win32"to identify Windows environmentsWindowsSelectorEventLoopPolicywhich is more compatible with async libraries on Windowswait-for-port.shto use PowerShell'sGet-NetTCPConnectionon Windows systemsTesting
make devon Windows environmentsImpact
Related Issues
Resolves the Windows-specific startup failure that was blocking local development on Windows machines.
Fixes #3212