After Effects 25.2.2 (Win) - CEP Remote Debugging Port Not Opening (netstat Confirms No Listening Pr

[LitNightt]

Hello everyone,

I'm encountering a persistent issue where I'm unable to use remote debugging for my CEP extension in After Effects 25.2.2 on Windows. The core problem is that After Effects does not seem to open or listen on the specified remote debugging port. I'm hoping someone in the community has encountered this or can offer new insights, as extensive troubleshooting has not yet resolved it.

My Environment:

• Operating System: Windows (User: Pro980)
• Adobe After Effects Version: 25.2.2
• CEP Version (inferred from logs): CEP 12 (e.g., CEP12-AEFT.log shows PlugPlug version 12.0.1.2)

Problem Description: When my CEP extension panel (or even a minimal test panel) is loaded in After Effects, I cannot connect to the configured remote debugging port (e.g., http://localhost:8089, http://127.0.0.1:8089, or other ports tested). The browser consistently shows a "site can't be reached" error. Critically, using the netstat -ano | findstr ":[PORT_NUMBER]" command in Windows command line confirms that there is no process listening on the configured debug port when After Effects and the panel are active.

Troubleshooting Steps Performed (Exhaustively):

Correct Extension Path: Confirmed the extension is in the correct user-specific folder: C:\Users\Pro980\AppData\Roaming\Adobe\CEP\extensions.

CSXS/manifest.xml Configuration:

• Validated ExtensionBundleId and Extension Id.
• Ensured MainPath (e.g., ./client/index.html) and ScriptPath (for my main extension) are correct. Confirmed ./ prefix is necessary for the panel to load.
• <CEFCommandLine> includes <Parameter>--remote-debugging-port=[PORT]</Parameter> (tried 8089, 8091, 8092).
• For my main extension, <Parameter>--enable-nodejs</Parameter> and <Parameter>--mixed-context</Parameter> are included (removing them breaks panel UI functionality, so they seem necessary for the panel itself).

CSXS/.debug File:

• Correctly formatted XML specifying the panel's Extension Id and the Host Name="AEFT" with the matching Port number as defined in manifest.xml.

Windows Firewall:

• "Adobe After Effects 2025" application is explicitly allowed for Private and Public networks.
• Specific inbound rules were created to "Allow" TCP connections for all tested ports (8089, 8091, 8092) across all network profiles (Domain, Private, Public).
• netstat confirmed no other applications were using the specified ports, ruling out a direct port conflict.

Registry Settings:

• PlayerDebugMode (String Value REG_SZ) has been verified and set to 1 in all found CSXS version keys under HKEY_CURRENT_USER\Software\Adobe, specifically including CSXS.11 and CSXS.12.
• The computer was fully restarted after these registry changes.

Conflicting Extensions:

• All other CEP extensions were temporarily removed from both user-specific (AppData\Roaming...) and system-level (Program Files (x86)\Common Files...) extension folders to ensure no conflicts. This did not resolve the issue.

Different Ports Tested: Ports 8089, 8091, and 8092 were all tested with corresponding changes in manifest.xml, .debug file, and firewall rules. None worked.

CEP Log Files Reviewed:

• Inspected CEP12-AEFT.log, CEPHtmlEngine12-AEFT-[version]-com.[extensionId].ui.log, and the ...-renderer.log.
• No explicit errors such as "failed to start debug server," "port in use," or other direct indicators of a debug port initialization failure specific to the debug service were found. The main ...ui.log typically only shows an "Injecting cep_node" message as the last entry during these attempts.

Key Diagnostic: Minimal Test Extension Also Fails To isolate the problem from my main extension's complexity, I created an absolutely minimal CEP extension:

• New, unique Bundle ID and Panel ID.
• Simple manifest.xml pointing to a basic index.html.
• CEFCommandLine contained only <Parameter>--remote-debugging-port=8092</Parameter>.
• Corresponding .debug file for port 8092.
• New firewall rule for port 8092.

Result: This "Minimal Test Panel" loads and displays its simple HTML content correctly within After Effects. However, its remote debugging port (8092) is also unreachable, and netstat confirms After Effects is not listening on this port either.

Conclusion & Request for Help: The failure of even a minimal test extension strongly suggests the issue is not specific to my QuickFX extension's code but likely lies with the After Effects 25.2.2 installation, the general CEP 12 environment on my Windows system, or a potential system-level conflict that's preventing After Effects from initializing any CEP debug service.

• Has anyone else experienced similar issues with remote debugging ports not opening in After Effects 25.2.x (or recent versions) on Windows?
• Are there any other known After Effects or CEP environmental variables, configuration files, or system settings (beyond what's listed above) that could influence CEP debug port initialization?
• Could this be a bug in this specific version of After Effects or CEP?

Any insights, suggestions for further diagnostics, or shared experiences would be greatly appreciated. I have an Adobe Support case open (ADB-39868579-N2V0), and a support representative has offered to forward a forum discussion link to the engineering team.

Thank you!

[Kevin-Monahan]

Hello @LitNightt,

Welcome to the forum. I'm Kevin from Adobe Support, a moderator here. Thanks for filing your bug report. Your information is appreciated. I hope an Adobe Expert or a member of the product team will respond shortly. Tagging the bug report with the SDK label should alert the appropriate people. Sorry for the frustration. Take care.

Thanks,
Kevin

[LitNightt]

Hello All,

I'm hoping you can help or forward to the relevant team member/bug fixer.

Thanks to further diagnostics, I believe I've found the specific reason why the remote debugging port isn't opening in After Effects 25.2.2.

Using Process Explorer to inspect the running processes, I examined the command line arguments being passed from AfterFX.exe to the CEPHtmlEngine.exe process responsible for rendering the CEP panel (even the minimal test one).

The command line arguments do not contain the expected --remote-debugging-port=xxxx parameter directly.

Instead, After Effects appears to be passing the parameter wrapped in a JSON array, which is then Base64 encoded. For example, when using port 8092, one of the arguments passed to CEPHtmlEngine.exe is literally:

WyItLXJlbW90ZS1kZWJ1Z2dpbmctcG9ydD04MDkyIl0=

Decoding this Base64 string reveals the intended parameter, but incorrectly formatted: ["--remote-debugging-port=8092"] Since CEPHtmlEngine.exe likely expects the parameter directly (e.g., --remote-debugging-port=8092) and not as a Base64 encoded JSON array string, it fails to recognize the instruction to start the debugging service.

This strongly suggests an issue or bug within After Effects 25.2.2 itself, specifically in how it processes the debugging parameters from the manifest.xml or .debug file and passes them when launching the CEPHtmlEngine process.

Hoping this specific finding helps the engineering team pinpoint the problem.

Many Thanks,

Jonas

[JohnColombo]

Hi @LitNightt,

Thank you for reporting this issue (and thank you @Kevin-Monahan for bringing the report to our attention.)

Is the remote debugging working for you in the previous major version (24.6) or the previous minor version (25.1) of After Effects? Both should still be available via the Creative Cloud app for you to test. This would be the best indicator of whether the behavior is a bug or an issue in the local environment.

Thank you for any additional info, 

- John, After Effects Engineering Team 

[LitNightt]

Ok I have just installed both those versions 1 at a time and tested my debugging and I get the exact same Base64 encoded string (WyItLXJlbW90ZS1kZWJ1Z2dpbmctcG9ydD04MDkyIl0=) for the remote debugging port argument.

Starting to look like it may not be Adobe specific but something to do with my workspace? I've uninstalled and re-installed multiple times (and now multiple versions) and still the same issue.

Thanks,
Jonas

[LitNightt]

I have also just now used the Adobe Cleaner tool and still have the exact same issue when I've re-installed my After Effects.

[LitNightt]

Any help @JohnColombo , I've got a client project I'm working on and could really do with some advice please 

[JohnColombo]

@LitNightt Thank you for the follow-up. Check the email that you've used to sign in the Adobe forums—I've invited you to a deveoper community where you can (hopefully) find a solution to this issue on your machine.

- Cheers,

- John, After Effects Engineering Team