DevoxxGenie Files

A patch release for one freeze: the Activity Log tool window could lock up the IDE after a busy agent or MCP session, and the cost was paid by every window in the IDE, not just the log.

Fixed

• fix(ui): the Activity Log no longer freezes the IDE under sustained MCP and agent traffic. The panel's JList was deliberately variable-height so multi-line tool output could grow its row, and each row's text was set as Swing HTML. Both decisions compound: a variable-height list has no cached row geometry, so Swing re-measures every retained row on each model change, and JLabel reparses its HTML on both setText and setForeground — which DefaultListCellRenderer calls for each cell, each pass. With 1,000 retained entries, some of them multi-megabyte MCP responses, a single new log line meant a full HTML re-layout of the whole backlog on the EDT; entries also arrived one addElement/remove at a time, each firing its own model event and its own layout pass, and scrollToBottom called ensureIndexIsVisible, which forces exactly the variable-row layout being avoided. Under a busy agent run that added up to tens of seconds of frozen EDT — the whole IDE, since it is one thread. Rows are now fixed-height (24px) and single-line: formatForListRow collapses a payload into a bounded 500-character preview with ↵ markers where line breaks were, and stops scanning as soon as the preview is full, so a multi-megabyte response is never copied merely to paint one row. The renderer sets plain text instead of HTML, a new ActivityLogListModel coalesces retention trimming and filter changes into one bulk event per update (appendAllAndRemoveFirst, replaceAll, removeFirst) instead of one per entry, and scrolling moves the scrollbar directly and only when you are already at the bottom — isFollowingTail leaves the view alone if you have scrolled up to read something, where before every new entry yanked you back to the tail. The pending-log timer is now a single reusable non-repeating Timer started on the EDT rather than a fresh one per batch, and it is stopped on dispose alongside a disposed guard so queued invokeLater work cannot touch a closed panel. Two user-visible changes come with this: rows are single-line previews rather than growing multi-line blocks, and default retention drops from 1,000 to 250 entries — the complete, untruncated payload is still one copy or double-click away, in the editor view. A new AgentMcpLogPanelPerformanceTest covers large payloads, pruning arithmetic under an active filter, and the tail-follow decision (task-260, [#1279])

Contributors

• @stephanj