Windows: Updated 128-bit characteristic UUID not reflected after firmware change (possible GATT cache issue?)

[silaswaxter]

First off — thank you for the great library.

Description

I'm encountering an issue on Windows where a modified 128-bit characteristic UUID is not reflected in Bleak after updating my peripheral firmware. The service UUID appears correctly, but the characteristic UUID remains stuck at its previous value.

This looks like a Windows GATT caching issue, but I want to confirm whether:

1. This is expected OS behavior.
2. Bleak provides a way to force fresh service discovery.
3. The previously merged Windows caching fixes (e.g., feat/windows-caching-issue) should already handle this case.

Peripheral

Custom embedded device (Nordic nRF52 running Zephyr).

• Originally:
  • Service UUID: 562326d3-a8e8-43c4-b783-daa2145291f1
  • Characteristic UUID: 562326d4-a8e8-43c4-b783-daa2145291f1

I then changed the characteristic UUID.

• Updated:
  • Service UUID: 562326d3-a8e8-43c4-b783-daa2145291f1
  • Characteristic UUID: 5c64d0cf-3ea7-42c7-9e92-844e3b345402

This is verified using nRF Connect (via nRF USB dongle), which correctly shows the updated UUID; see image below.

Environment

• bleak 2.1.1
• Windows 11
• Python 3.14.3

Supporting Info

"""
Scan/Discovery
--------------

Example showing how to scan for BLE devices.

Updated on 2019-03-25 by hbldh <henrik.blidh@nedomkull.com>

"""

import argparse
import asyncio
import logging
from contextlib import asynccontextmanager

from bleak import BleakScanner, BleakClient

logger = logging.getLogger(__name__)


class Args(argparse.Namespace):
    debug: bool

async def active_scan(duration_s: int):
    devices = await BleakScanner.discover(
        return_adv=True,
        timeout=duration_s,
        scanning_mode="active",
    )

    for device_data, advertisement_data in devices.values():
        logger.info("=" * 40)
        logger.info(device_data)
        logger.info(advertisement_data)

class DeviceNotFoundError(Exception):
    """Raised when a BLE device cannot be found."""
    pass

@asynccontextmanager
async def connect_to_device(device_name: str, timeout_s: int = 5):
    device = await BleakScanner.find_device_by_name(
        name=device_name,
        timeout=timeout_s,
        scanning_mode="active",
    )
    if device is None:
        raise DeviceNotFoundError(f"Failed to find device with name '{device_name}'")

    async with BleakClient(device) as client:
        yield client

async def main(args: Args):
    logger.debug("entering main")

    # scan_time_s = 2
    # async def scanner_worker():
    #     while True:
    #         ble_min_advertisement_period_s = 0.020
    #         await active_scan(duration_s=ble_min_advertisement_period_s)
    # try:
    #     await asyncio.wait_for(scanner_worker(), timeout=scan_time_s)
    # except asyncio.TimeoutError:
    #     logger.debug(f"Scan stopped after {scan_time_s} seconds")

    async with connect_to_device("Silas ROM") as client:
        logger.info(client.is_connected)
        for service in client.services:
            logger.info(f"service w/ desc='{service.description}', uuid='{service.uuid}'")

            for char in service.characteristics:
                logger.info(f"  Characteristic: uuid='{char.uuid}', props={char.properties}")
                # Find the Characteristic User Description (CUD) descriptor
                for descriptor in char.descriptors:
                    logger.info(f"    Descriptor: uuid='{descriptor.uuid}'")
                    # if descriptor.uuid == "2901":  # Standard CUD UUID
                    #     cud_value = await client.read_gatt_descriptor(descriptor.handle)
                    #     logger.info(f"      CUD: {cud_value.decode('utf-8')}")
        await asyncio.sleep(10)


if __name__ == "__main__":
    # parse cli args
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "-d",
        "--debug",
        action="store_true",
        help="sets the logging level to debug",
    )   
    args = parser.parse_args(namespace=Args())

    # setup logging
    log_level = logging.DEBUG if args.debug else logging.INFO
    logging.basicConfig(
        level=log_level,
        format="%(asctime)-15s %(name)-8s %(levelname)s: %(message)s",
    )


    asyncio.run(main(args))

> python .\main.py
2026-02-21 22:15:18,074 __main__ INFO: True
2026-02-21 22:15:18,074 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-21 22:15:18,075 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-21 22:15:18,075 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-21 22:15:18,075 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-21 22:15:18,075 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-21 22:15:18,075 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-21 22:15:18,075 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-21 22:15:18,075 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-21 22:15:18,075 __main__ INFO:   Characteristic: uuid='562326d4-a8e8-43c4-b783-daa2145291f1', props=['read']

[dlech]

1. This is expected OS behavior.

If the peripheral does not implement the GATT Database Hash characteristic, then yes, it is expected. Ideally a peripheral that changes the attribute layout would implement this and things should "just work" on all OSes.

Bleak provides a way to force fresh service discovery.

On Windows, there is an option for this. See https://bleak.readthedocs.io/en/latest/api/args.html#bleak.args.winrt.WinRTClientArgs.use_cached_services

The previously merged Windows caching fixes (e.g., feat/windows-caching-issue) should already handle this case.

We've changed the defaults a few times over the years. There isn't one option that works in all cases. So we've settled on the "let Windows decide" option as the default for Bleak. It works for well-designed peripherals and we have the other options to work around cases like this one.

[silaswaxter]

I wasn't aware of the GATT Database Hash characteristic; that's pretty cool.

• I implemented the GATT Database Hash and Service Changed on my embedded device (Zephyr + Nordic nRF52x).
• Verified the updated service/characteristic UUIDs with nRF Connect, which shows the new UUIDs immediately.
• In Python/Bleak (WinRT backend), the first connection enumerates stale UUIDs. I tried waiting 10 seconds while connected to see if the cache would refresh/if printing them out again would reflect the change, but the services/characteristics remained stale. Only after disconnecting and reconnecting (or running the script a second time) do the UUIDs reflect the intended values. See log attached at the bottom.

While running, I also noticed repeated warnings in the log:

bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event

From what I understand, this suggests that Windows received a Service Changed indication but Bleak didn’t automatically refresh its service collection. I’ve seen other issues where WinRT successfully handled Service Changed events, so I'm wondering if I'm using bleak wrong or if there is an issue on the peripheral not handling things correctly?

Updated Code:

    async with connect_to_device("Silas ROM") as client:
        logger.info(client.is_connected)
        for service in client.services:
            logger.info(f"service w/ desc='{service.description}', uuid='{service.uuid}'")

            for char in service.characteristics:
                logger.info(f"  Characteristic: uuid='{char.uuid}', props={char.properties}")
                # Find the Characteristic User Description (CUD) descriptor
                for descriptor in char.descriptors:
                    logger.info(f"    Descriptor: uuid='{descriptor.uuid}'")
                    # if descriptor.uuid == "2901":  # Standard CUD UUID
                    #     cud_value = await client.read_gatt_descriptor(descriptor.handle)
                    #     logger.info(f"      CUD: {cud_value.decode('utf-8')}")

        await asyncio.sleep(10)

        for service in client.services:
            logger.info(f"service w/ desc='{service.description}', uuid='{service.uuid}'")

            for char in service.characteristics:
                logger.info(f"  Characteristic: uuid='{char.uuid}', props={char.properties}")
                # Find the Characteristic User Description (CUD) descriptor
                for descriptor in char.descriptors:
                    logger.info(f"    Descriptor: uuid='{descriptor.uuid}'")
                    # if descriptor.uuid == "2901":  # Standard CUD UUID
                    #     cud_value = await client.read_gatt_descriptor(descriptor.handle)
                    #     logger.info(f"      CUD: {cud_value.decode('utf-8')}")

Log showing the characteristic UUID--stale in first run, correct in second.

> python .\main.py
2026-02-22 14:19:04,622 __main__ INFO: True
2026-02-22 14:19:04,622 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:04,622 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 14:19:04,622 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:04,622 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['write', 'read']
2026-02-22 14:19:04,622 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:04,623 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:04,623 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:04,623 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:04,623 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:04,623 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 14:19:04,623 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-000000000000', props=['read']
2026-02-22 14:19:04,751 bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event
2026-02-22 14:19:04,951 bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event
2026-02-22 14:19:05,735 bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event
2026-02-22 14:19:14,632 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:14,632 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 14:19:14,632 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:14,632 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['write', 'read']
2026-02-22 14:19:14,632 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:14,632 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:14,633 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:14,633 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:14,633 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:14,633 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 14:19:14,633 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-000000000000', props=['read']
> python .\main.py
2026-02-22 14:19:25,567 __main__ INFO: True
2026-02-22 14:19:25,567 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:25,567 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 14:19:25,567 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:25,567 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['write', 'read']
2026-02-22 14:19:25,567 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:25,567 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:25,568 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:25,568 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:25,568 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:25,568 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 14:19:25,568 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-ffffffffffff', props=['read']
2026-02-22 14:19:35,582 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:35,583 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 14:19:35,583 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:35,583 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['write', 'read']
2026-02-22 14:19:35,583 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:35,583 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 14:19:35,584 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:35,584 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:35,584 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 14:19:35,584 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 14:19:35,584 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-ffffffffffff', props=['read']
(rom_ui) PS C:\Users\silas\workspace\rom_ui\services\ble_controller> 

[dlech]

• In Python/Bleak (WinRT backend), the first connection enumerates stale UUIDs.

I think this is to be expected. If the device already had cached GATT services that didn't contain the database hash, then Windows wouldn't know to check it for an update. Now that Windows knows it has this service, I think if you add/remove characteristics, it should find them right away now.

From what I understand, this suggests that Windows received a Service Changed indication but Bleak didn’t automatically refresh its service collection. I’ve seen other issues where WinRT successfully handled Service Changed events, so I'm wondering if I'm using bleak wrong or if there is an issue on the peripheral not handling things correctly?

Windows issues this event on every service that it discovers whether or not there is actually a Service Changed indication. So it is hard to say if this was actually triggered by this or just part of the regular enumeration of services. It's still a "warning" so that people might report it like this so we can try to understand it better 😄.

During connection and the initial enumeration of the GATT services, I think all of the OSes are handling the Services Changed indication automatically. Although I'm not sure this is entire reliable, which is why I suggested the database hash service instead - it seems to work well everywhere.

Really, only cases where the database changes at runtime after connecting is where it would make sense for Bleak to handle the services changed event. This has only come up once that I recall in #1639, but that discussion didn't really go anywhere.

If you are able to reproduce this warning reliably and want to dig into it more I would be interested to hear what you find. Otherwise I will consider the workarounds to still be good enough. 😄

[dlech]

In your test program, calling for service in client.services: after the asyncio.sleep() doesn't tell Windows to re-enumerate the services. You would need to call client._backend._get_services() for that.

[dlech]

I implemented the GATT Database Hash and Service Changed on my embedded device (Zephyr + Nordic nRF52x).

BTW, implementing both is actually redundant (unless the database changes after connecting like mentioned above).

Edit: I guess if you are doing an update from not having the database hash characteristic to having it, then the Service Changed helps. But after that, you don't really need the Service Changed characteristic anymore.

[silaswaxter]

Edit: deleted bc I didn't see your first comment sorry. I'll reply when I've read everything you said.

[silaswaxter]

First off, I verified that the GATT hash db characteristic is working as expected:

1. 
2. change the UUID of the same characteristic I've been testing with.
3. 

I think this is to be expected. If the device already had cached GATT services that didn't contain the database hash, then Windows wouldn't know to check it for an update. Now that Windows knows it has this service, I think if you add/remove characteristics, it should find them right away now.

Yeah this makes sense. However, I'm seeing the same behavior repeatedly; I removed the device with windows, and have performed this test a number of times since wherein the characteristic UUID is updating/changed.

If you are able to reproduce this warning reliably and want to dig into it more I would be interested to hear what you find.

I would like that. I did some digging on the service changed characteristic, and this excerpt from SI Labs might actually explain it since my devices are not bonded or paired.

When I enable pairing via the pair flag in the the bleak client, I no longer see the bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event. However, I also don't see any updates to the services/characteristics like I saw before with the 1st run is stale cache, 2nd run works.

In your test program, calling for service in client.services: after the asyncio.sleep() doesn't tell Windows to re-enumerate the services. You would need to call client._backend._get_services() for that.

This doesn't seem to work; see the code and logs below. Also this appears to be a private method which makes my programmer spidey-sense hairs stand up.

    async with connect_to_device("Silas ROM") as client:
        logger.info(client.is_connected)
        for service in client.services:
            logger.info(f"service w/ desc='{service.description}', uuid='{service.uuid}'")

            for char in service.characteristics:
                logger.info(f"  Characteristic: uuid='{char.uuid}', props={char.properties}")
                # Find the Characteristic User Description (CUD) descriptor
                for descriptor in char.descriptors:
                    logger.info(f"    Descriptor: uuid='{descriptor.uuid}'")
                    # if descriptor.uuid == "2901":  # Standard CUD UUID
                    #     cud_value = await client.read_gatt_descriptor(descriptor.handle)
                    #     logger.info(f"      CUD: {cud_value.decode('utf-8')}")
        
        await asyncio.sleep(5)

        await client._backend._get_services()

        for service in client.services:
            logger.info(f"service w/ desc='{service.description}', uuid='{service.uuid}'")

            for char in service.characteristics:
                logger.info(f"  Characteristic: uuid='{char.uuid}', props={char.properties}")
                # Find the Characteristic User Description (CUD) descriptor
                for descriptor in char.descriptors:
                    logger.info(f"    Descriptor: uuid='{descriptor.uuid}'")
                    # if descriptor.uuid == "2901":  # Standard CUD UUID
                    #     cud_value = await client.read_gatt_descriptor(descriptor.handle)
                    #     logger.info(f"      CUD: {cud_value.decode('utf-8')}")

    await asyncio.sleep(1)

Here is the output before running this twice in succession I changed the char UUID from 5c64d0cf-3ea7-42c7-9e92-333333333333 to 5c64d0cf-3ea7-42c7-9e92-000000000000

> python .\main.py
2026-02-22 17:53:50,618 __main__ INFO: True
2026-02-22 17:53:50,618 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 17:53:50,618 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 17:53:50,618 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 17:53:50,618 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['read', 'write']
2026-02-22 17:53:50,618 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:50,618 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 17:53:50,619 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:50,619 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:50,619 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:50,619 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 17:53:50,619 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-333333333333', props=['read']
2026-02-22 17:53:50,751 bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event
2026-02-22 17:53:50,950 bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event
2026-02-22 17:53:51,843 bleak.backends.winrt.client WARNING: D8:41:37:CF:3A:B8: unhandled services changed event
2026-02-22 17:53:55,635 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 17:53:55,635 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 17:53:55,636 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 17:53:55,636 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['read', 'write']
2026-02-22 17:53:55,636 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:55,636 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 17:53:55,636 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:55,636 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:55,637 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:53:55,637 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 17:53:55,637 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-333333333333', props=['read']
> python .\main.py
2026-02-22 17:54:57,684 __main__ INFO: True
2026-02-22 17:54:57,685 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 17:54:57,685 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['write', 'read']
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:54:57,685 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:54:57,685 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 17:54:57,685 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-000000000000', props=['read']
2026-02-22 17:55:02,697 __main__ INFO: service w/ desc='Generic Attribute Profile', uuid='00001801-0000-1000-8000-00805f9b34fb'
2026-02-22 17:55:02,697 __main__ INFO:   Characteristic: uuid='00002a05-0000-1000-8000-00805f9b34fb', props=['indicate']
2026-02-22 17:55:02,697 __main__ INFO:     Descriptor: uuid='00002902-0000-1000-8000-00805f9b34fb'
2026-02-22 17:55:02,697 __main__ INFO:   Characteristic: uuid='00002b29-0000-1000-8000-00805f9b34fb', props=['write', 'read']
2026-02-22 17:55:02,698 __main__ INFO:   Characteristic: uuid='00002b2a-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:55:02,698 __main__ INFO: service w/ desc='Generic Access Profile', uuid='00001800-0000-1000-8000-00805f9b34fb'
2026-02-22 17:55:02,698 __main__ INFO:   Characteristic: uuid='00002a00-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:55:02,698 __main__ INFO:   Characteristic: uuid='00002a01-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:55:02,698 __main__ INFO:   Characteristic: uuid='00002a04-0000-1000-8000-00805f9b34fb', props=['read']
2026-02-22 17:55:02,698 __main__ INFO: service w/ desc='Unknown', uuid='562326d3-a8e8-43c4-b783-daa2145291f1'
2026-02-22 17:55:02,698 __main__ INFO:   Characteristic: uuid='5c64d0cf-3ea7-42c7-9e92-000000000000', props=['read']

[dlech]

However, I'm seeing the same behavior repeatedly; I removed the device with windows, and have performed this test a number of times since wherein the characteristic UUID is updating/changed.

We would need to look at the Bluetooth packet capture to see what is really going on.

This doesn't seem to work; see the code and logs below.

I think that tells us that the unhanded events were not actually triggered by a Services Changed indication. A Bluetooth packet capture would give us more insight.

Also this appears to be a private method which makes my programmer spidey-sense hairs stand up.

It is just for the purposes of investigation. 😄 If we found that this actually did something useful, we would implement in a proper way. (But it doesn't seem to be helpful anyway.)

[silaswaxter]

We would need to look at the Bluetooth packet capture to see what is really going on.

Wireshark? Is there a guide you could point me to?

Quick google search looks like it wants me to use an external sniffer like an nordic dongle but that wont reproduce the behavior right? Or are we only interested in capturing the packets from the peripheral not the interactions between host and peripheral?

It is just for the purposes of investigation. 😄 If we found that this actually did something useful, we would implement in a proper way. (But it doesn't seem to be helpful anyway.)

Ahh gotcha.

[dlech]

Is there a guide you could point me to?

https://bleak.readthedocs.io/en/latest/troubleshooting.html#capture-bluetooth-traffic