**cylc-7 client/server communications is not backward compatible with cylc-6.**
Note that cylc-7 bug fixes were back-ported to a series of 6.11.x releases,
for those who have not transitioned to cylc-7 yet.
Highlighted Changes
[1923](https://github.com/cylc/cylc-flow/pull/1923): **A new HTTPS communications
layer, replaces Pyro-3 Object RPC for all client-server communications.**
Suite daemons are now web servers!
[2063](https://github.com/cylc/cylc-flow/pull/2063): **Removed deprecated cylc-5
syntax and features.**
[2044](https://github.com/cylc/cylc-flow/pull/2044): Suite start-up now aborts with
a sensible message on suite configuration errors (previously this happened post
daemonization so the user had to check suite logs to see the error).
[2067](https://github.com/cylc/cylc-flow/pull/2067): Consolidated suite service
files (passphrase, SSL files, contact file, etc.) under `.service/` in the
suite run directory; the suite registration database and port files under
`$HOME/.cylc/` are no longer used; suites can now be grouped in sub-directory
trees under the top level run directory.
[2033](https://github.com/cylc/cylc-flow/pull/2033): Allow restart from suite state
checkpoints other than the latest (checkpoints are also recorded automatically
before and after restarts, and on reload).
[2024](https://github.com/cylc/cylc-flow/pull/2024): `cylc gscan` now supports
collapsible suite groups via a top level suite config `group` item.
Right-click *View Column* "Group".
[2074](https://github.com/cylc/cylc-flow/pull/2074): Task retry states and timers,
and poll timers, now persist across suite restarts. Waiting tasks are not
put in the held state before shutdown. Held tasks are not automatically
released on restart.
[2004](https://github.com/cylc/cylc-flow/pull/2004): Task event handlers are
now continued on restart.
Other Changes
[2042](https://github.com/cylc/cylc-flow/pull/2042): Documented `[scheduling]spawn
to max active cycle points` (new in 6.11.0), which lets successive instances of
the same task run out of order if dependencies allow.
[2092](https://github.com/cylc/cylc-flow/pull/2092): New command `cylc
get-suite-contact` to print suite contact information (host, port, PID, etc.)
[2089](https://github.com/cylc/cylc-flow/pull/2089): Improved documentation on
cycling workflows and use of parameterized tasks as a proxy for cycling.
[2021](https://github.com/cylc/cylc-flow/pull/2021): `cylc gui`: removed the
"connection failed" warning dialog that popped up on suite shutdown. This
should be obvious by the reconnection countdown timer in the info bar.
[2023](https://github.com/cylc/cylc-flow/pull/2023): New custom event email footer
via global or suite config.
[2013](https://github.com/cylc/cylc-flow/pull/2013): Fixed "remove task after
spawning" which since 6.9.0 would not force a waiting task to spawn its
successor.
[2071](https://github.com/cylc/cylc-flow/pull/2071): Fix quote stripping on
`initial cycle point = "now"`.
[2070](https://github.com/cylc/cylc-flow/pull/2070): Fix dummy mode support for
custom task outputs: they were incorrectly propagated to other tasks.
[2065](https://github.com/cylc/cylc-flow/pull/2065): `cylc gscan` now supports
suite name filtering via a `--name` command line option.
[2060](https://github.com/cylc/cylc-flow/pull/2060): 5-second timeout if hanging
connections are encountered during port scanning.
[2055](https://github.com/cylc/cylc-flow/pull/2055): Task elapsed times now persist
over restarts.
[2046](https://github.com/cylc/cylc-flow/pull/2046): Multi-task interface for `cylc
show`. Fixed *View Prerequisites* for tasks in the runahead pool.
[2049](https://github.com/cylc/cylc-flow/pull/2049): Per-host job submission and
execution polling intervals via global/user config files.
[2051](https://github.com/cylc/cylc-flow/pull/2051): Bundle Jinja2 2.8 with Cylc -
one less external software dependency.
[2088](https://github.com/cylc/cylc-flow/pull/2088): Support dependence on absolute
cycle points in cycling graphs.