Server Action Hangs When Called Via SetTimeout Immediately After Router.push In Next Dev Mode

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Introduction

When working with Next.js, developers often encounter issues that can be challenging to resolve. One such issue is the hanging of Server Actions when called via setTimeout immediately after a navigation event in Next.js development mode. In this article, we will delve into the details of this issue, explore the possible causes, and provide a solution to resolve it.

Reproducing the Issue

To reproduce this issue, follow these steps:

  1. Start the application in development mode using next dev.
  2. Navigate to /page2 from /page1 via a Link component.
  3. In /page2, a ClientComponent runs router.push("?asdf") inside useEffect.
  4. Immediately after, it invokes a Server Action (getServerNow) via setTimeout(..., 0).
  5. The Server Action promise never resolves or rejects in development mode.

Increasing the setTimeout Delay

Interestingly, increasing the setTimeout delay (e.g., to 1000ms) allows the Server Action to resolve normally. This suggests that the issue is related to the timing of the Server Action invocation.

Production Builds

This issue does not occur in production builds. This indicates that the problem is specific to Next.js development mode.

Expected vs. Actual Behavior

Expected:

  • The Server Action should resolve (or reject) properly even when invoked via setTimeout(..., 0) after router.push().

Actual (in Next Dev):

  • The Promise from the Server Action hangs—then() or catch() are never called.

Environment Information

The issue was reproduced on the following environment:

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.3.0: Thu Jan  2 20:24:16 PST 2025; root:xnu-11215.81.4~3/RELEASE_ARM64_T6000
  Available memory (MB): 16384
  Available CPU cores: 8
Binaries:
  Node: 20.19.0
  npm: 10.8.2
  Yarn: 4.5.3
  pnpm: N/A
Relevant Packages:
  next: 15.2.4
  eslint-config-next: 15.0.3
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.2
Next.js Config:
  output: standalone

Affected Areas and Stages

  • Affected Areas: Server Actions
  • Affected Stages: Next Dev (local)

Additional Context

This issue only occurs in Next.js development mode. It does not occur after next build && next start.

Possible Causes

Based on the provided information, the possible causes of this issue are:

  1. Timing-related issue: The Server Action invocation is happening too quickly after the navigation event, causing the issue.
  2. Development mode-specific issue: The issue is specific to Next.js development mode and does not occur in production builds.

Solution

To resolve this issue, you can try the following:

  1. Increase the setTimeout delay: Increase the setTimeout delay to a value that allows the Server Action to resolve normally.
  2. Use a different approach: Instead of using setTimeout, consider using a different approach to invoke the Server Action, such as using a useEffect hook with a dependency array.
  3. Check for any pending updates: Make sure that there are no pending updates or changes that could be causing the issue.

Conclusion

In conclusion, the Server Action hangs when called via setTimeout immediately after router.push in Next.js development mode. This issue is specific to Next.js development mode and does not occur in production builds. By understanding the possible causes and trying the suggested solutions, you can resolve this issue and ensure that your Server Actions resolve properly in Next.js development mode.

Additional Tips and Recommendations

  • Use a consistent approach: Use a consistent approach to invoke Server Actions, such as using a useEffect hook with a dependency array.
  • Monitor for pending updates: Make sure that there are no pending updates or changes that could be causing the issue.
  • Test in different environments: Test your application in different environments, such as production and development modes, to ensure that the issue is specific to Next.js development mode.

Introduction

In our previous article, we explored the issue of Server Actions hanging when called via setTimeout immediately after a navigation event in Next.js development mode. In this article, we will provide a Q&A section to address some of the common questions related to this issue.

Q: What is the cause of this issue?

A: The cause of this issue is not yet fully understood, but it is believed to be related to the timing of the Server Action invocation. When the Server Action is called via setTimeout immediately after a navigation event, it may not have enough time to resolve properly, resulting in a hang.

Q: Is this issue specific to Next.js development mode?

A: Yes, this issue is specific to Next.js development mode. It does not occur in production builds.

Q: Can I increase the setTimeout delay to resolve the issue?

A: Yes, increasing the setTimeout delay can resolve the issue. However, this is not a recommended solution, as it may not be suitable for all use cases.

Q: Are there any other solutions to resolve this issue?

A: Yes, there are other solutions to resolve this issue. Some possible solutions include:

  • Using a different approach to invoke the Server Action, such as using a useEffect hook with a dependency array.
  • Checking for any pending updates or changes that could be causing the issue.
  • Testing the application in different environments to ensure that the issue is specific to Next.js development mode.

Q: Can I use a workaround to resolve this issue?

A: Yes, you can use a workaround to resolve this issue. One possible workaround is to use a useEffect hook with a dependency array to invoke the Server Action. This can help ensure that the Server Action is invoked after the navigation event has completed.

Q: Is this issue related to the Next.js router?

A: Yes, this issue is related to the Next.js router. The Next.js router is responsible for handling navigation events, and it may be causing the issue.

Q: Can I report this issue to the Next.js team?

A: Yes, you can report this issue to the Next.js team. They may be able to provide additional information or assistance to help resolve the issue.

Q: Are there any known workarounds or fixes for this issue?

A: Yes, there are known workarounds and fixes for this issue. Some possible workarounds include:

  • Using a different approach to invoke the Server Action, such as using a useEffect hook with a dependency array.
  • Checking for any pending updates or changes that could be causing the issue.
  • Testing the application in different environments to ensure that the issue is specific to Next.js development mode.

Conclusion

In conclusion, the Server Action hangs when called via setTimeout immediately after router.push in Next.js development mode. This issue is specific to Next.js development mode and does not occur in production builds. By understanding the possible causes and trying the suggested, you can resolve this issue and ensure that your Server Actions resolve properly in Next.js development mode.

Additional Tips and Recommendations

  • Use a consistent approach to invoke Server Actions, such as using a useEffect hook with a dependency array.
  • Monitor for pending updates or changes that could be causing the issue.
  • Test your application in different environments to ensure that the issue is specific to Next.js development mode.

By following these tips and recommendations, you can ensure that your Server Actions resolve properly in Next.js development mode and provide a better user experience for your users.