Keep recovery handoffs available after publication cancellation

internal/gotool/recovery.go

@@ -8,6 +8,8 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strconv"
+	"strings"
 
 	"golang.org/x/mod/modfile"
 
@@ -17,6 +19,30 @@ import (
 const releaseKitModule = "go.maximumdirect.net/releasekit"
 const releaseKitCommand = releaseKitModule + "/cmd/releasekit"
 
+// TemporaryExecutable recognizes executables in Go's temporary build layout,
+// <work parent>/go-build<nonce>/b<action>/exe/<name>. Those paths disappear when
+// the Go driver finishes and cannot provide a later native-command fallback.
+func TemporaryExecutable(path string) bool {
+	exeDir := filepath.Dir(path)
+	if filepath.Base(exeDir) != "exe" {
+		return false
+	}
+	actionDir := filepath.Dir(exeDir)
+	action, ok := strings.CutPrefix(filepath.Base(actionDir), "b")
+	if !ok || action == "" {
+		return false
+	}
+	if _, err := strconv.ParseUint(action, 10, 64); err != nil {
+		return false
+	}
+	nonce, ok := strings.CutPrefix(filepath.Base(filepath.Dir(actionDir)), "go-build")
+	if !ok || nonce == "" {
+		return false
+	}
+	_, err := strconv.ParseUint(nonce, 10, 64)
+	return err == nil
+}
+
 // RecoveryTool returns module-selected Go arguments for a later invocation.
 // An empty result means this module does not select ReleaseKit. API-only modules
 // receive a private module root that outlives launcher-owned bootstraps.

internal/gotool/recovery_test.go

@@ -0,0 +1,22 @@
+package gotool
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestRecoveryFallbackExecutableLifetime(t *testing.T) {
+	for _, test := range []struct {
+		path      string
+		temporary bool
+	}{
+		{filepath.Join("tmp", "go-build123456", "b001", "exe", "releasekit"), true},
+		{filepath.Join("cache", "go-build", "hash-d", "releasekit"), false},
+		{filepath.Join("tmp", "tools", "releasekit"), false},
+		{filepath.Join("workspace", "go-build-project", "b001", "exe", "releasekit"), false},
+	} {
+		if got := TemporaryExecutable(test.path); got != test.temporary {
+			t.Errorf("temporary executable %q = %t, want %t", test.path, got, test.temporary)
+		}
+	}
+}