Subscribing to a binary channel name triggers `UnicodeDecodeError` on reconnect

[diesieben07]

You can subscribe to a binary channel name like so:

await pubsub.subscribe(b'\xc3\x28')
while True:
    message = await pubsub.get_message(ignore_subscribe_messages=True, timeout=1.0)
    if message is not None:
        pass # do stuff

Note that the channel name I picked is invalid UTF-8.

When the underlying connection pool is configured to retry on errors, it will reconnect on error and then eventually end up in PubSub.on_connect.
This method attempts to decode all channel names using the connection's decoder, so it can pass them as kwargs to subscribe. This is guaranteed to work for all channels with a listener (because those must have been created via kwargs in the first place). However if there is no listener attached to a channel, it may have been passed as a normal argument to subscribe in which case it may not be valid according to the encoding (and even if it is, encoding/decoding may break it).

The synchronous code has the same bug:

redis-py/redis/client.py

Lines 896 to 919 in 334cb3b

	def on_connect(self, connection) -> None:
	"Re-subscribe to any channels and patterns previously subscribed to"
	# NOTE: for python3, we can't pass bytestrings as keyword arguments
	# so we need to decode channel/pattern names back to unicode strings
	# before passing them to [p]subscribe.
	self.pending_unsubscribe_channels.clear()
	self.pending_unsubscribe_patterns.clear()
	self.pending_unsubscribe_shard_channels.clear()
	if self.channels:
	channels = {
	self.encoder.decode(k, force=True): v for k, v in self.channels.items()
	}
	self.subscribe(**channels)
	if self.patterns:
	patterns = {
	self.encoder.decode(k, force=True): v for k, v in self.patterns.items()
	}
	self.psubscribe(**patterns)
	if self.shard_channels:
	shard_channels = {
	self.encoder.decode(k, force=True): v
	for k, v in self.shard_channels.items()
	}
	self.ssubscribe(**shard_channels)

This then leads to UnicodeDecodeError being thrown:

1768463839457	2026-01-15T07:57:19.457Z	UnicodeDecodeError: 'utf-8' codec can't decode byte 0x80 in position 8: invalid start byte
1768463839457	2026-01-15T07:57:19.457Z	            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1768463839457	2026-01-15T07:57:19.457Z	    value = value.decode(self.encoding, self.encoding_errors)
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/_parsers/encoders.py", line 43, in decode
1768463839457	2026-01-15T07:57:19.457Z	             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1768463839457	2026-01-15T07:57:19.457Z	    channels[self.encoder.decode(k, force=True)] = v
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/client.py", line 904, in on_connect
1768463839457	2026-01-15T07:57:19.457Z	    await task
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/connection.py", line 343, in connect_check_health
1768463839457	2026-01-15T07:57:19.457Z	    await self.connect_check_health(check_health=True)
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/connection.py", line 296, in connect
1768463839457	2026-01-15T07:57:19.457Z	    await conn.connect()
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/client.py", line 954, in _reconnect
1768463839457	2026-01-15T07:57:19.457Z	    await fail(error)
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/retry.py", line 53, in call_with_retry
1768463839457	2026-01-15T07:57:19.457Z	           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1768463839457	2026-01-15T07:57:19.457Z	    return await conn.retry.call_with_retry(
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/client.py", line 964, in _execute
1768463839457	2026-01-15T07:57:19.457Z	               ^^^^^^^^^^^^^^^^^^^^
1768463839457	2026-01-15T07:57:19.457Z	    response = await self._execute(
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/client.py", line 984, in parse_response
1768463839457	2026-01-15T07:57:19.457Z	               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1768463839457	2026-01-15T07:57:19.457Z	    response = await self.parse_response(block=(timeout is None), timeout=timeout)
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/.cache/pypoetry/virtualenvs/my-app-venv/lib/python3.12/site-packages/redis/asyncio/client.py", line 1111, in get_message
1768463839457	2026-01-15T07:57:19.457Z	              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1768463839457	2026-01-15T07:57:19.457Z	    message = await pubsub.get_message(ignore_subscribe_messages=True, timeout=1.0)
1768463839457	2026-01-15T07:57:19.457Z	  File "/home/app/code/backend/my_event_bus/listener.py", line 53, in __aiter__

My workaround for now is to base64-encode my channels.

[petyaslavova]

Hi @diesieben07, thank you for bringing this to our attention! We'll have a look at it.