From c6fb4262826f83a635fb024cd8ddc0a0f5fe449b Mon Sep 17 00:00:00 2001
From: Greg Pomerantz <gmp@wow.st>
Date: Sat, 10 Oct 2026 06:49:11 -0400
Subject: [PATCH] Add a 15s startup watchdog that dumps all goroutine stacks
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The splash hang is intermittent and the process is unattachable from the
shell (not debuggable, no root, no signal permission), so the next
occurrence must be self-reporting: if no frame renders within 15 s of
entering the frame loop, log debug.Stack() — the blocked goroutine's
stack is the diagnosis.
---
 cmd/pad/main.go | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/cmd/pad/main.go b/cmd/pad/main.go
index dc4b43d..18d59b5 100644
--- a/cmd/pad/main.go
+++ b/cmd/pad/main.go
@@ -7,6 +7,7 @@ import (
 	"log"
 	"os"
 	"path/filepath"
+	"runtime/debug"
 	"strings"
 	"sync"
 	"time"
@@ -156,9 +157,24 @@ func run(w *app.Window) error {
 	var mu sync.Mutex
 	var frame editor.Frame
 
+	firstFrameCh := make(chan struct{}) // closed when the first frame renders (watchdog)
+
 	go frameReceiver(w, &mu, &frame, logic.FrameChan())
 	go logic.Run()
 	log.Printf("startup: logic running, entering frame loop")
+	// Startup watchdog: if no frame has been rendered 15 s after entering
+	// the frame loop, dump every goroutine's stack. A splash-screen hang is
+	// intermittent and usually gone by the time anyone can attach a
+	// debugger; the dump makes the next occurrence self-reporting — which
+	// goroutine is blocked where (FUSE read, channel, GL loop) is the whole
+	// diagnosis.
+	go func() {
+		select {
+		case <-firstFrameCh:
+		case <-time.After(15 * time.Second):
+			log.Printf("STARTUP WATCHDOG: no frame 15s after entering the frame loop — goroutine dump:\n%s", debug.Stack())
+		}
+	}()
 	// firstFrame logs the moment the UI actually drew something (splash
 	// done): the anchor for bisecting startup hangs — the log line missing
 	// after "entering frame loop" points at the blocked phase.
@@ -200,6 +216,7 @@ func run(w *app.Window) error {
 		case app.FrameEvent:
 			if !firstFrame {
 				firstFrame = true
+				close(firstFrameCh)
 				log.Printf("startup: first frame rendered")
 			}
 			if perfOn {