[lawrencecchen]

Summary

ghostty_surface_render_counters gains seven fields at the end of the struct. They count each surface's thread wakes by source:

• renderer thread: the wakeup async, the draw-now async, and the cursor blink, animation and scrollback-compression timer fires
• termio thread: the wakeup async, and its timer fires (resize coalesce, synchronized-output reset, selection scroll)

Each count is one relaxed atomic add in a callback that already runs. No behavior changes.

Why

cmux keeps hidden terminals live (its warm set). On cmux24, 24 busy hidden terminals at a warm cap of 25 woke the app 181.8 times a second, against 76.9 at a cap of 8. None of those wakeups were on the main thread.

cmux's own counters show that its output path already runs once per hidden output batch. So the remaining cost, about 2.4-3.4 wakeups a second while idle plus 3-4 per batch for each live hidden terminal, is on the surface's own threads. These counts name the source, per surface, so a cmux test can bound it exactly (cmux SWITCH FRAMES, "hidden output" row).

Base

This is based on release/cmux-9ce9b7d0-e2 (34e73ba8b), the cmux pin, so that one GhosttyNextKit pin bump takes only this change. The struct grows at its end; the existing fields keep their offsets.

Test plan

• Fork CI builds the xcframework for this PR.
• The cmux red test (branch fix/hidden-terminal-wakeups) reads these counts for live hidden surfaces.

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Summary by cubic

Adds per-surface thread wake counters to ghostty_surface_render_counters so a cmux test can bound the cost of keeping hidden terminals alive. Each counter is a relaxed atomic add in an existing callback; no behavior changes.

• Renderer thread counters: wakeup async, draw-now async, and cursor blink, animation, and scrollback-compression timer fires.
• Termio thread counters: wakeup async and timer fires (resize coalesce, synchronized-output reset, selection scroll).

^{Written for commit 782f66b. Summary will update on new commits.}

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[lawrencecchen]

Review (subagent, correctness first): SHIP at 9509f26

• ABI: the 16 existing fields keep their order and offsets. The 7 new uint64 fields are appended in the same order in ghostty.h and the Zig extern struct, and the getter fills all 23 fields.
• Each counter counts once per real wake. On the renderer thread, the timer callbacks count after the Canceled return. On the termio thread, the timers are never cancelled today; libxev's timer_reset re-queues without a cancel callback.
• Threads: the atomics are relaxed. io_thread and renderer are stable fields of the heap-allocated CoreSurface, so they are read under the same lifetime rule as the existing counters.
• No behavior change: the change adds fetchAdd calls only.
• Note: the struct is returned by value. The header and the library must ship together; GhosttyKit always ships them together.

[lawrencecchen]

Review (subagent, correctness first): SHIP at 782f66b

• The fix (9509f26..782f66b) only moves pub const Counters above alloc. The thread's fields now form one block with no declaration between them, which removes the CI error.
• The merge onto the moved base 7d43bb6 (input: one compiled link regex per pattern for the whole process #69, renderer + embedded: the embedder presents a new host size with its bounds (set_host_present, host_frame) #70, renderer: an off-main present never commits while it holds the Core Animation lock (embedder-mode deadlock from #70) #71) is clean (git merge-tree).
• input: one compiled link regex per pattern for the whole process #69 to renderer: an off-main present never commits while it holds the Core Animation lock (embedder-mode deadlock from #70) #71 add no fields to ghostty_surface_render_counters_s. In the merged tree, ghostty.h and the Zig extern struct both have the 16 old fields and then the 7 new ones, in the same order.
• The base did not change the renderer thread, generic.zig or the termio thread. Every increment stays after its cancel and error returns.
• Still true: the struct grows by 56 bytes, and it is returned by value. The header and the library ship together in the xcframework.