This is a significant release with lots of major and long requested features. Here's a run down:
Session Resurrection
This version adds a built-in capability to resurrect sessions. Attaching to "exited" sessions will re-create them, placing any running commands behind a Press <ENTER> to run banner so as to prevent awkward situations with things like rm -rf. Sessions can also be resurrected through the session-manager.
Read more
Special thanks to @AlixBernard for implementing the serialization algorithm, as well as to @alekspickle for helping integrate the algorithm with our code base. Without them this feature would not have come to be.
UI Components for Plugins
This version introduces UI Components for plugins. Allowing plugins to render beautiful and consistent UI elements (eg. table, ribbon, nexted-list) no matter which programming language they were developped in. These components are serialized on the plugin-side and interpreted by our ANSI interpreter using a private DCS.
Read more
Load Plugins from the Web
This release introduces the http(s) prefix for plugin URLs. Meaning we would be able to load them from the web just like we load them from the HD.
A new top-level CLI command was also added to make loading plugins easier:
zellij plugin -- https://example.com/plugin.wasm # Will also work with file: and zellij: urls
Thanks @jaeheonji for designing and implementing this feature.
Renaming Sessions
It's now possible to rename the current session. This can either be done through the CLI with the new rename-session action, or through the session-manager with Ctrl r.
Start panes in-place
Sometimes, when opening new panes it can be convenient to have them open "in-place", meaning that they would replace the currently active pane and then drop back to it once they exit. This release adds this ability to zellij run and similar commands using the --in-place flag.
Wasmer 3.x upgrade
While not user facing, this is an important upgrade of our WebAssembly runtime that makes packaging easier as well as facilitating compatibility to some platforms.
Thanks @tlinford for his tremendous efforts in getting this done
New Plugin APIs
RunCommand - execute command in the background and get a response
This API allows plugins to run a command on the host machine. The command will run in the background and the plugin will be notified with an Event when the command has completed, receiving its exit code, STDIN and STDOUT.
WebRequest - execute an http(s) request in the background and get a response
This API allows plugins to make a web request and receive its output. The request will run in the background and the plugin will receive an Event with the response once the request is complete.
Add <ESC> - Drop to shell to command panes
For a while now, Zellij has had the concept of "command panes" - panes that run a specific command as part of the UI. Now, in addition to being able to re-run the command with ENTER and close the pane with Ctrl c, it's also possible to drop to a shell with <ESC>. This can be especially useful when combined with the session resurrection feature (eg. if one does not want to run the resurrected command but does not want to close the pane either).
Support Styled Underlines
Zellij now supports the "styled underlines" ANSI extension.
Thanks @eatgrass and @mike-lloyd03 for the implementation
Open new Plugins to current CWD
Starting this release, plugins are opened to the working folder of the currently focused terminal pane (if available), rather than the folder in which the Zellij session was started.
All changes

fix(utils): validate session name by @deepsghimire in fix(utils): validate session name zellij-org/zellij#2607
feat(panes): in place run by @imsnif in feat(panes): in place run zellij-org/zellij#2795
Fix: fg color for gruvbox light theme by @papey in Fix: fg color for gruvbox light theme zellij-org/zellij#2791
fix: display parsing error for kdl files located under the 'themes' directory by @shinhs0506 in fix: display parsing error for kdl files located under the 'themes' directory zellij-org/zellij#2762
feat(plugins): upgrade wasmer to 3.1.1 by @tlinford in feat(plugins): upgrade wasmer to 3.1.1 zellij-org/zellij#2706
remove leftover Cargo.lock file from session-manager plugin by @silwol in remove leftover Cargo.lock file from session-manager plugin zellij-org/zellij#2819
chore: migrate to directories from directories-next by @silwol in chore: migrate to directories from directories-next zellij-org/zellij#2820
chore: update uuid dependency to 1.4.1 by @silwol in chore: update uuid dependency to 1.4.1 zellij-org/zellij#2821
fix(plugins): address potential security issue by @tlinford in fix(plugins): address potential security issue zellij-org/zellij#2830
fix(plugins): add zellij version to cached artifact path by @tlinford in fix(plugins): add zellij version to cached artifact path zellij-org/zellij#2836
Session resurrection by @imsnif in Session resurrection zellij-org/zellij#2801
feat(client): terminal synchronized output by @gmorer in feat(client): terminal synchronized output zellij-org/zellij#2798
fix(resurrection): log failure instead of crashing in some edge cases by @imsnif in fix(resurrection): log failure instead of crashing in some edge cases zellij-org/zellij#2851
fix(plugins): make auxiliary functions (get_focused_tab and get_focused_pane) public by @Nacho114 in fix(plugins): make auxiliary functions (get_focused_tab and get_focused_pane) public zellij-org/zellij#2765
feat(plugins): plugin run_command api by @imsnif in feat(plugins): plugin run_command api zellij-org/zellij#2862
style: cyberpunk inspired theme options added by @Sr-vZ in style: cyberpunk inspired theme options added zellij-org/zellij#2868
feat(panes): Add an option to press  and drop to shell in command panes by @imsnif in feat(panes): Add an option to press <ESC> and drop to shell in command panes zellij-org/zellij#2872
feat(plugins): web requests api by @imsnif in feat(plugins): web requests api zellij-org/zellij#2879
fix(cli): session names only for attach in fish completion by @dj95 in fix(cli): session names only for attach in fish completion zellij-org/zellij#2857
feat(plugins): UI components by @imsnif in feat(plugins): UI components zellij-org/zellij#2898
feat: support load plugins from the web by @jaeheonji in feat: support load plugins from the web zellij-org/zellij#2863
feat(sessions): resurrect sessions through the session-manager (and plugin API) by @imsnif in feat(sessions): resurrect sessions through the session-manager (and plugin API) zellij-org/zellij#2902
Styled underlines by @eatgrass in Styled underlines zellij-org/zellij#2730
feat(ux): allow renaming sessions by @imsnif in feat(ux): allow renaming sessions zellij-org/zellij#2903
fix(plugins): start plugin pane in cwd of focused pane if possible by @imsnif in fix(plugins): start plugin pane in cwd of focused pane if possible zellij-org/zellij#2905
fix(resurrection): properly serialize certain edge cases by @imsnif in fix(resurrection): properly serialize certain edge cases zellij-org/zellij#2907
docs(api): docs for shim.rs by @imsnif in docs(api): docs for shim.rs zellij-org/zellij#2909

New Contributors

@deepsghimire made their first contribution in fix(utils): validate session name zellij-org/zellij#2607
@papey made their first contribution in Fix: fg color for gruvbox light theme zellij-org/zellij#2791
@shinhs0506 made their first contribution in fix: display parsing error for kdl files located under the 'themes' directory zellij-org/zellij#2762
@silwol made their first contribution in remove leftover Cargo.lock file from session-manager plugin zellij-org/zellij#2819
@gmorer made their first contribution in feat(client): terminal synchronized output zellij-org/zellij#2798
@Sr-vZ made their first contribution in style: cyberpunk inspired theme options added zellij-org/zellij#2868
@dj95 made their first contribution in fix(cli): session names only for attach in fish completion zellij-org/zellij#2857
@eatgrass made their first contribution in Styled underlines zellij-org/zellij#2730

Full Changelog: zellij-org/zellij@v0.38.2...v0.39.0