diff --git a/modules/xdebug/breakpoints.go b/modules/xdebug/breakpoints.go
index 06c3c9ab..8f8ce9d9 100644
--- a/modules/xdebug/breakpoints.go
+++ b/modules/xdebug/breakpoints.go
@@ -34,7 +34,7 @@ type SavedBreakpoint struct {
 	Type      string    `json:"type"`                // line or exception
 	File      string    `json:"file,omitempty"`      // file:// URI as PHP sees it (line)
 	Line      int       `json:"line,omitempty"`      // line
-	Exception string    `json:"exception,omitempty"` // class name, e.g. \Throwable (exception)
+	Exception string    `json:"exception,omitempty"` // class name as PHP holds it, e.g. Throwable (exception)
 	Condition string    `json:"condition,omitempty"` // PHP expression; sent only with allow_eval
 	Enabled   bool      `json:"enabled"`
 	Source    string    `json:"source"` // ui or mcp
@@ -50,7 +50,9 @@ func (b *SavedBreakpoint) normalize() error {
 		}
 	}
 	b.File = fileURI(strings.TrimSpace(b.File))
-	b.Exception = strings.TrimSpace(b.Exception)
+	// Xdebug matches the class name as PHP holds it, with no leading \;
+	// "\RuntimeException" would be accepted and never fire.
+	b.Exception = strings.TrimPrefix(strings.TrimSpace(b.Exception), `\`)
 	switch b.Type {
 	case BPLine:
 		if b.File == "" || b.Line < 1 {
@@ -62,7 +64,7 @@ func (b *SavedBreakpoint) normalize() error {
 		b.Exception = ""
 	case BPException:
 		if b.Exception == "" {
-			return errors.New("an exception breakpoint needs exception (a class name, e.g. \\Throwable)")
+			return errors.New("an exception breakpoint needs exception (a class name, e.g. Throwable)")
 		}
 		b.File, b.Line = "", 0
 	default:
diff --git a/modules/xdebug/breakpoints_test.go b/modules/xdebug/breakpoints_test.go
index 4382bfbe..a9afc820 100644
--- a/modules/xdebug/breakpoints_test.go
+++ b/modules/xdebug/breakpoints_test.go
@@ -125,7 +125,7 @@ func TestBreakpoints_SentAtStartWithState(t *testing.T) {
 	waitFor(t, "break", s.Paused)
 
 	sets := be.commands("breakpoint_set")
-	if len(sets) != 2 || !strings.Contains(sets[0], "-t line -f file:///app/src/User.php -n 20") || !strings.Contains(sets[1], `-t exception -x "\\Throwable"`) {
+	if len(sets) != 2 || !strings.Contains(sets[0], "-t line -f file:///app/src/User.php -n 20") || !strings.Contains(sets[1], `-t exception -x Throwable`) {
 		t.Fatalf("breakpoint_set: %q", sets)
 	}
 	// Breakpoints go out before the script runs.
@@ -147,7 +147,7 @@ func TestBreakpoints_SentAtStartWithState(t *testing.T) {
 	for _, want := range []string{
 		`"id":` + itoa(int(line.ID)) + `,"type":"line","file":"file:///app/src/User.php","line":20,"enabled":true,"source":"ui"`,
 		`"state":"resolved","resolved_line":21,"hit_count":2`,
-		`"id":` + itoa(int(exc.ID)) + `,"type":"exception","exception":"\\Throwable"`,
+		`"id":` + itoa(int(exc.ID)) + `,"type":"exception","exception":"Throwable"`,
 		`"id":` + itoa(int(off.ID)) + `,"type":"line","file":"file:///app/src/Off.php","line":3,"enabled":false`,
 		`"state":"disabled"`,
 		`"id":` + itoa(int(cond.ID)),
@@ -246,7 +246,7 @@ func TestBreakpoints_API(t *testing.T) {
 	if code, body := a.do(t, "POST", "/api/xdebug/breakpoints", `{"exception":"\\RuntimeException"}`); code != http.StatusCreated || !strings.Contains(body, `"type":"exception"`) {
 		t.Fatalf("exception: %d %s", code, body)
 	}
-	if code, body := a.do(t, "GET", "/api/xdebug/breakpoints", ""); code != http.StatusOK || !strings.Contains(body, `"exception":"\\RuntimeException"`) {
+	if code, body := a.do(t, "GET", "/api/xdebug/breakpoints", ""); code != http.StatusOK || !strings.Contains(body, `"exception":"RuntimeException"`) {
 		t.Fatalf("list: %d %s", code, body)
 	}
 	if code, _ := a.do(t, "PATCH", "/api/xdebug/breakpoints/99", `{"enabled":false}`); code != http.StatusNotFound {
@@ -538,3 +538,25 @@ func TestBreakpoints_ListResolves(t *testing.T) {
 		t.Fatalf("%+v", bps)
 	}
 }
+
+// Xdebug matches an exception breakpoint by the class name as PHP holds it:
+// "\RuntimeException" is accepted by the engine and never fires.
+func TestBreakpoints_ExceptionLeadingBackslash(t *testing.T) {
+	for in, want := range map[string]string{
+		`\RuntimeException`:     `RuntimeException`,
+		` \App\Errors\Payment `: `App\Errors\Payment`,
+		`RuntimeException`:      `RuntimeException`,
+		`*`:                     `*`,
+	} {
+		b := SavedBreakpoint{Exception: in}
+		if err := b.normalize(); err != nil || b.Type != BPException || b.Exception != want {
+			t.Errorf("%q: got %q type %q err %v, want %q", in, b.Exception, b.Type, err, want)
+		}
+		if cmd := breakpointSetCmd(b); !strings.HasSuffix(cmd, " -x "+quoteArg(want)) {
+			t.Errorf("%q: command %q", in, cmd)
+		}
+	}
+	if b := (SavedBreakpoint{Exception: `\`}); b.normalize() == nil {
+		t.Error(`a lone \ must be rejected`)
+	}
+}
diff --git a/modules/xdebug/control_mcp.go b/modules/xdebug/control_mcp.go
index 62b5a019..34c82232 100644
--- a/modules/xdebug/control_mcp.go
+++ b/modules/xdebug/control_mcp.go
@@ -224,7 +224,7 @@ func (s *Session) pausedAtOf() time.Time {
 type bpSetInput struct {
 	File      string `json:"file,omitempty" jsonschema:"File as PHP sees it: an absolute path (/var/www/app/src/User.php) or a file:// URI. Paths on the PHP side, not your local checkout, unless they are the same."`
 	Line      int    `json:"line,omitempty" jsonschema:"Line number (1-based) for a line breakpoint"`
-	Exception string `json:"exception,omitempty" jsonschema:"Exception class for an exception breakpoint instead of file+line, e.g. \\Throwable or \\App\\Exceptions\\PaymentFailed"`
+	Exception string `json:"exception,omitempty" jsonschema:"Exception class for an exception breakpoint instead of file+line, e.g. Throwable or App\\Exceptions\\PaymentFailed (a leading \\ is dropped)"`
 	Condition string `json:"condition,omitempty" jsonschema:"PHP expression; stop only when it is true. Needs xdebug.allow_eval."`
 }