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Change the MSC3814 dehydrated device /events endpoint paging to match spec conventions #19897

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Change the MSC3814 dehydrated device /events endpoint paging to match spec conventions #19897

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e5b3ea9
Use 'from' in dehydrated device events API, instead of 'next_batch'
andybalaam Jun 30, 2026
faca7e1
Omit next_batch from dehydrated device events response if there are n…
andybalaam Jun 30, 2026
c4e30a6
Update comment
andybalaam Jul 1, 2026
c701266
Don't force the client to request again to find out there are no more…
andybalaam Jul 1, 2026
cfee5ba
Fix typo with a != > chain
andybalaam Jul 2, 2026
d2d861e
Fix lint - extraneous start of range
andybalaam Jul 2, 2026
01a4c1a
Expand dehydrated device test to cover multiple batches and support t…
andybalaam Jul 2, 2026
f937280
Make the POST API always return next_batch, as before
andybalaam Jul 2, 2026
e18d64b
Reformat code
andybalaam Jul 2, 2026
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1 change: 1 addition & 0 deletions changelog.d/19897.misc
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Change the [MSC3814](https://github.com/matrix-org/matrix-spec-proposals/pull/3814) dehydrated device `/events` endpoint paging to match spec conventions.
13 changes: 9 additions & 4 deletions synapse/handlers/devicemessage.py
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Expand Up @@ -361,8 +361,9 @@ async def get_events_for_dehydrated_device(
since_token: stream id to start from when fetching messages
limit: the number of messages to fetch
Returns:
A dict containing the to-device messages, as well as a token that the client
can provide in the next call to fetch the next batch of messages
A dict containing the to-device `messages`, as well as a `next_batch` token that the
client can provide in the next call to fetch the next batch of messages. If `next_batch`
is missing, there are no more messages to fetch.
"""

user_id = requester.user.to_string()
Expand Down Expand Up @@ -426,11 +427,15 @@ async def get_events_for_dehydrated_device(
user_id,
)

return {
ret: JsonDict = {
"events": messages,
"next_batch": f"d{stream_id}",
}

if len(messages) > 0:
ret["next_batch"] = f"d{stream_id}"

@richvdh richvdh Jul 1, 2026

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This means that the client will have to make an extra round-trip when it gets to the end of the pending messages, just to double-check that there are no more messages. Could we make get_messages_for_device return an additional boolean return value, indicating whether or not the result was "limited"?

@andybalaam andybalaam Jul 1, 2026

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How about c701266 ?

@richvdh richvdh Jul 1, 2026

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I don't think that's valid in the type system!

Seems reasonable in principle though.

@andybalaam andybalaam Jul 2, 2026

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Ouch, thank you. I've pushed fixes for this and a couple of other problems.


return ret


def split_device_messages_into_edus(
sender_user_id: str,
Expand Down
4 changes: 2 additions & 2 deletions synapse/rest/client/devices.py
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Expand Up @@ -255,13 +255,13 @@ async def on_GET(
) -> tuple[int, JsonDict]:
requester = await self.auth.get_user_by_req(request)

next_batch = parse_string(request, "next_batch")
since_token = parse_string(request, "from")
limit = parse_integer(request, "limit", 100)

msgs = await self.message_handler.get_events_for_dehydrated_device(
requester=requester,
device_id=device_id,
since_token=next_batch,
since_token=since_token,
limit=limit,
)

Expand Down
3 changes: 2 additions & 1 deletion tests/rest/client/test_devices.py
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Expand Up @@ -248,12 +248,13 @@ def test_dehydrate_msc3814(self) -> None:
# messages so we should receive an empty array
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channel = self.make_request(
"GET",
f"_matrix/client/unstable/org.matrix.msc3814.v1/dehydrated_device/{device_id}/events?next_batch={next_batch_token}",
f"_matrix/client/unstable/org.matrix.msc3814.v1/dehydrated_device/{device_id}/events?from={next_batch_token}",
access_token=token,
shorthand=False,
)
self.assertEqual(channel.code, 200)
self.assertEqual(channel.json_body["events"], [])
self.assertNotIn("next_batch", channel.json_body)

# make sure we can delete the dehydrated device
channel = self.make_request(
Expand Down
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