ASUSWRT not working on RT-AC51U Router

[baunan]

The problem

I have a simple old router ASUS RT-AC51U where the integration hasn't worked for some time. When trying to set it up I am getting an unknown error. I do this regardless of selection of https, http, port etc when trying to login.

What version of Home Assistant Core has the issue?

2026.5.4

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant Supervised

Integration causing the issue

ASUSWRT

Link to integration documentation on our website

https://www.home-assistant.io/integrations/asuswrt

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Logger: homeassistant.components.asuswrt.config_flow
Source: components/asuswrt/config_flow.py:190
Integration: asuswrt (documentation, issues)
First occurred: 08:57:11 (1 occurrence)
Last logged: 08:57:11

Unknown error connecting with AsusWrt router at 192.168.10.2 using protocol https
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/asuswrt/config_flow.py", line 190, in _async_check_connection
    await api.async_connect()
  File "/usr/src/homeassistant/homeassistant/components/asuswrt/bridge.py", line 389, in async_connect
    await self._api.async_connect()
  File "/usr/local/lib/python3.14/site-packages/asusrouter/asusrouter.py", line 203, in async_connect
    return await self.async_get_identity() is not None
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.14/site-packages/asusrouter/asusrouter.py", line 293, in async_get_identity
    self._identity = await collect_identity(
                     ^^^^^^^^^^^^^^^^^^^^^^^
    ...<2 lines>...
    )
    ^
  File "/usr/local/lib/python3.14/site-packages/asusrouter/modules/identity.py", line 119, in collect_identity
    identity = _read_nvram(identity_map)
  File "/usr/local/lib/python3.14/site-packages/asusrouter/modules/identity.py", line 175, in _read_nvram
    raise ex
  File "/usr/local/lib/python3.14/site-packages/asusrouter/modules/identity.py", line 166, in _read_nvram
    value = method(data[key]) if method else data[key]
                                             ~~~~^^^^^
KeyError: 'serial_no'

Additional information

The integration has worked before on this router, but unsure when it stopped, but definitely worked on 2025.11. It has not worked on any of the updates this year. My HA is running on a Proxmox VM on a NUC i3, OS is 16.3

[home-assistant]

Hey there @kennedyshead, @ollo69, @Vaskivskyi, mind taking a look at this issue as it has been labeled with an integration (asuswrt) you are listed as a code owner for? Thanks!

Code owner commands

Code owners of asuswrt can trigger bot actions by commenting:

• @home-assistant close Closes the issue.
• @home-assistant rename Awesome new title Renames the issue.
• @home-assistant reopen Reopen the issue.
• @home-assistant unassign asuswrt Removes the current integration label and assignees on the issue, add the integration domain after the command.
• @home-assistant add-label needs-more-information Add a label (needs-more-information, problem in dependency, problem in custom component, problem in config, problem in device, feature-request) to the issue.
• @home-assistant remove-label needs-more-information Remove a label (needs-more-information, problem in dependency, problem in custom component, problem in config, problem in device, feature-request) on the issue.

_{^{(message by CodeOwnersMention)}}

---

@baunan Thanks for reporting this issue!

Before we dive in, please make sure this isn't a duplicate by searching through existing issues. Also check recently closed issues, as your problem might already be fixed but not yet released.

https://github.com/home-assistant/core/issues?q=%20label%3A%22integration%3A%20asuswrt%22%20
_{^{(message by IssueContext)}}

---

asuswrt documentation
asuswrt source
_{^{(message by IssueLinks)}}

[Vaskivskyi]

Hey, @baunan, I will try to help you with this as the maintainer of the backend library producing the error.

You mentioned it worked with HA 2025.11, but the library dependency hasn't changed since 2025.9.4. Do you recall whether you have updated/changed your device firmware? Regardless, what is the current firmware version of your router?

Thanks!

[baunan]

Hi, The firmware version on the router is 3.0.0.4.947_9135 and it hasn't been updated since I got the router from the internet provider. I haven't used this integration to something specific, so for that reason somewhat uncertain when it failed. I removed the integration to reinstall it as part of the trouble shooting, so lost entities in that process which could perhaps told me when it was last working.

[Vaskivskyi]

Not to worry about 🙂

Currently, the backend library is going through a larger rebuild, which should take a couple of weeks more. Do you mind waiting until then, so that your bug can be fixed together with a few other things?

If not, let me know - I will try to implement a hot-patch into the current architecture and update the dependency for HA. Just keep in mind that it still can take some time to do properly, and until in will get into a stable HA version

[baunan]

No problem from my side. As mentioned earlier, I don't use this integration to anything particular