diff --git a/data.go b/data.go
index 5c808d0..e866cf6 100644
--- a/data.go
+++ b/data.go
@@ -51,6 +51,9 @@ type ZasData struct {
 	// onto the layout's <body> element since Body only carries the source
 	// body's inner HTML, not the element itself.
 	bodyAttrs map[string]string
+	// Tracks embed nesting depth for this render, guarding against a self-
+	// or mutually-embedding file recursing without bound.
+	embedDepth int
 }
 
 /*
diff --git a/embed_depth_test.go b/embed_depth_test.go
new file mode 100644
index 0000000..2a9f459
--- /dev/null
+++ b/embed_depth_test.go
@@ -0,0 +1,33 @@
+package zas
+
+import (
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/melvinmt/gt"
+)
+
+// A file that embeds itself (directly, or through a cycle of mutually-
+// embedding files) recurses through parseAndReplace/handleEmbedTags without
+// bound now that raw HTML - including <embed> tags written in a .md source -
+// is no longer dropped by the Markdown converter. This must fail with an
+// error instead of exhausting the goroutine's stack.
+
+func TestRenderMarkdownSelfEmbedReturnsError(t *testing.T) {
+	t.Chdir(t.TempDir())
+	if err := os.WriteFile("self.md", []byte(`<embed src="self.md" type="text/markdown" />`+"\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	gen := &Generator{
+		Config: ConfigSection{"mimetypes": ConfigSection{"text/markdown": "markdown"}},
+		I18n:   &gt.Build{Index: gt.Strings{}, Origin: "en"},
+	}
+	err := gen.renderMarkdown("self.md")
+	if err == nil {
+		t.Fatal("renderMarkdown() on a self-embedding file: want error, got nil")
+	}
+	if !strings.Contains(err.Error(), "embed nesting") {
+		t.Fatalf("error = %v, want it to report excessive embed nesting", err)
+	}
+}
diff --git a/generate.go b/generate.go
index 4fadd20..678cb54 100644
--- a/generate.go
+++ b/generate.go
@@ -184,7 +184,19 @@ func (gen *Generator) Generate(path string, data *ZasData) (err error) {
 	return
 }
 
+// maxEmbedDepth bounds how many levels of <embed> an entry file may nest.
+// Markdown and HTML embed handlers call back into parseAndReplace for
+// whatever they embed, so a file that embeds itself (directly, or through a
+// cycle of mutually-embedding files) would otherwise recurse until the
+// goroutine's stack is exhausted.
+const maxEmbedDepth = 20
+
 func (gen *Generator) parseAndReplace(processed bytes.Buffer, data *ZasData) (doc *goquery.Document, err error) {
+	if data.embedDepth >= maxEmbedDepth {
+		return nil, fmt.Errorf("embed nesting deeper than %d levels; check for a self- or mutually-embedding file", maxEmbedDepth)
+	}
+	data.embedDepth++
+	defer func() { data.embedDepth-- }()
 	// Here we manipulate its result.
 	doc, err = goquery.NewDocumentFromReader(&processed)
 	if err != nil {