fix: stop binding SIGPIPE to the root context

The root command binds syscall.SIGPIPE to the cancellation context in
cmd/skaffold/app/skaffold.go. Once a process registers SIGPIPE via
signal.Notify/NotifyContext, the Go runtime delivers it for every file
descriptor, so a SIGPIPE raised when a registry (e.g. mcr.microsoft.com)
resets an idle connection mid-build is interpreted as a request to
cancel the whole run. Multi-stage builds whose first stage runs longer
than the registry's ~60s idle timeout are cancelled with the reason
"broken pipe signal received".

Stop treating SIGPIPE as cancellation: remove it from NotifyContext and
signal.Ignore it instead. Ignoring it (rather than just dropping it)
preserves the original reason SIGPIPE was caught in #510 -- broken-pipe
writes during shutdown return EPIPE instead of killing the process, so
cleanup still completes when skaffold's output pipe is closed.

Fixes #10106

Author: DionJones615

cmd/skaffold/app/skaffold.go

@@ -33,7 +33,7 @@ import (
 )
 
 func Run(out, stderr io.Writer) error {
-	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM, syscall.SIGINT, syscall.SIGPIPE)
+	ctx, cancel := rootContext()
 	defer cancel()
 
 	catchStackdumpRequests()
@@ -63,3 +63,18 @@ func Run(out, stderr io.Writer) error {
 	}
 	return err
 }
+
+// rootContext returns the root context for a skaffold invocation, cancelled on interrupt and
+// termination signals.
+//
+// SIGPIPE is intentionally NOT a cancellation trigger; it is ignored instead. Once a process
+// registers SIGPIPE with signal.Notify, Go delivers it for every file descriptor, so binding it
+// to the cancellation context caused long-running builds to be cancelled whenever a registry
+// (e.g. mcr.microsoft.com) reset an idle connection mid-build (#10106). Ignoring it keeps
+// broken-pipe writes returning EPIPE without killing the process, which preserves the original
+// intent of catching SIGPIPE (#510): a closed output pipe (e.g. `skaffold ... | head`) must not
+// abort skaffold before graceful cleanup finishes.
+func rootContext() (context.Context, context.CancelFunc) {
+	signal.Ignore(syscall.SIGPIPE)
+	return signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM, syscall.SIGINT)
+}

cmd/skaffold/app/skaffold_signal_test.go

@@ -0,0 +1,50 @@
+//go:build !windows
+// +build !windows
+
+/*
+Copyright 2025 The Skaffold Authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package app
+
+import (
+	"context"
+	"os/signal"
+	"syscall"
+	"testing"
+	"time"
+)
+
+// TestRootContextIgnoresSIGPIPE is a regression test for #10106: a SIGPIPE (raised when a
+// registry resets an idle connection during a long build) must not cancel the root context.
+// Before the fix SIGPIPE was passed to signal.NotifyContext, so this would cancel the context
+// and abort the build.
+func TestRootContextIgnoresSIGPIPE(t *testing.T) {
+	defer signal.Reset(syscall.SIGPIPE)
+
+	ctx, cancel := rootContext()
+	defer cancel()
+
+	if err := syscall.Kill(syscall.Getpid(), syscall.SIGPIPE); err != nil {
+		t.Fatalf("sending SIGPIPE: %v", err)
+	}
+
+	select {
+	case <-ctx.Done():
+		t.Fatalf("SIGPIPE cancelled the root context: %v (#10106 regression)", context.Cause(ctx))
+	case <-time.After(200 * time.Millisecond):
+		// expected: SIGPIPE is ignored and the context stays alive.
+	}
+}