[MetRonnie]

Closes #690

Implements the graphql-transport-ws subprotocol as defined in https://github.com/enisdenjo/graphql-ws/blob/master/PROTOCOL.md

Sibling: cylc/cylc-ui#2548

Check List

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• No dependency changes
• Tests are included (or explain why tests are not needed).
• Changelog entry included if this is a change that can affect users
• Cylc-Doc pull request opened if required at cylc/cylc-doc/pull/XXXX.
• If this is a bug fix, PR should be raised against the relevant ?.?.x branch.

[MetRonnie]

Requested a review from Copilot to try this out for the first time...

[Copilot]

Pull request overview

Switches the UI Server’s WebSocket GraphQL subscriptions to the graphql-transport-ws subprotocol and updates the server-side message handling to follow the newer protocol semantics.

Changes:

• Updated subscription WebSocket protocol constant and message handling (graphql-transport-ws, new message types, ping/pong, subscribe/next/complete).
• Simplified subscription handler state management by making sub_statuses handler-local and updated resolvers context wiring accordingly.
• Updated tests and added a changelog entry for the protocol change.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
cylc/uiserver/tests/test_handlers.py	Updates the subprotocol selection test to the new protocol.
cylc/uiserver/handlers.py	Switches the selected WebSocket subprotocol constant and adjusts subscription handler initialization/state.
cylc/uiserver/graphql/tornado_ws.py	Implements graphql-transport-ws message types and updates subscription server message processing logic.
cylc/uiserver/authorise.py	Tightens typing for AuthorizationMiddleware.auth.
cylc/uiserver/app.py	Removes app-level sub_statuses plumbing now that subscription status is handler-local.
changes.d/821.feat.md	Documents the protocol change in the changelog.

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[MetRonnie]

We are simultaneously upgrading the client (cylc/cylc-ui#2548) so this is not a problem (apart from the awkwardness of running development UI/UIS for a while when different branches have different subprotocols)

[dwsutherland]

Looks good to me 👍

Obviously you'll need the sibling in at the same time:

[E 2026-09-16 14:06:07.712 ServerApp] Uncaught exception GET /cylc/subscriptions (127.0.0.1)
    HTTPServerRequest(protocol='http', host='localhost:8888', method='GET', uri='/cylc/subscriptions', version='HTTP/1.1', remote_ip='127.0.0.1')
    Traceback (most recent call last):
.
.
.

Will post review there, seems like just something with GraphiQL to fix.

[oliver-sanders]

Reviewers: Worth performing a functional test of websocket_ping_interval/timeout.

Changes here shouldn't impact it (implemented at the tornado layer), but worth checking.

[MetRonnie]

If you mean

cylc-uiserver/cylc/uiserver/jupyter_config.py

Lines 56 to 59 in b07ec62

	# configure websocket pings (prevents clients / proxies closing seemingly idle
	# connections and helps us to detect dead connections)
	c.ServerApp.websocket_ping_interval = 5
	c.ServerApp.websocket_ping_timeout = 5

Then I believe that is ping/pong at the websocket layer: https://www.rfc-editor.org/info/rfc6455/#section-5.5.2

Whereas the ping/pong here is the at the subprotocol layer, so is completely separate

[oliver-sanders]

Yes, I don't think this would interact, but might be worth testing.