Implemented Markdown escaping for render output

internal/render/markdown.go

@@ -17,13 +17,13 @@ func (MarkdownRenderer) Render(transcript Transcript, opts Options) (string, err
 	if title == "" {
 		title = "Transcript"
 	}
-	lines = append(lines, "# "+title, "")
+	lines = append(lines, "# "+escapeMarkdownInline(title), "")
 
 	if opts.IncludeMetadata {
 		lines = append(lines,
-			fmt.Sprintf("- Application: %s", transcript.Metadata.Application),
-			fmt.Sprintf("- Version: %s", transcript.Metadata.Version),
-			fmt.Sprintf("- Output schema: %s", transcript.Schema),
+			fmt.Sprintf("- Application: %s", escapeMarkdownInline(transcript.Metadata.Application)),
+			fmt.Sprintf("- Version: %s", escapeMarkdownInline(transcript.Metadata.Version)),
+			fmt.Sprintf("- Output schema: %s", escapeMarkdownInline(transcript.Schema)),
 			"",
 		)
 	}
@@ -37,11 +37,11 @@ func (MarkdownRenderer) Render(transcript Transcript, opts Options) (string, err
 			parts = append(parts, fmt.Sprintf("[#%d]", segment.ID))
 		}
 
-		text := segment.Text
+		text := escapeMarkdownInline(segment.Text)
 		if shouldItalicize(segment.Categories) {
 			text = "*" + text + "*"
 		}
-		parts = append(parts, fmt.Sprintf("**%s:** %s", segment.Speaker, text))
+		parts = append(parts, fmt.Sprintf("**%s:** %s", escapeMarkdownInline(segment.Speaker), text))
 		lines = append(lines, strings.Join(parts, " "))
 		lines = append(lines, "")
 	}
@@ -53,6 +53,28 @@ func (MarkdownRenderer) Render(transcript Transcript, opts Options) (string, err
 	return output, nil
 }
 
+func escapeMarkdownInline(value string) string {
+	replacer := strings.NewReplacer(
+		`\`, `\\`,
+		"`", "\\`",
+		"*", "\\*",
+		"_", "\\_",
+		"{", "\\{",
+		"}", "\\}",
+		"[", "\\[",
+		"]", "\\]",
+		"(", "\\(",
+		")", "\\)",
+		"#", "\\#",
+		"+", "\\+",
+		"!", "\\!",
+		"|", "\\|",
+		"<", "\\<",
+		">", "\\>",
+	)
+	return replacer.Replace(value)
+}
+
 func shouldItalicize(categories []string) bool {
 	for _, category := range categories {
 		switch category {

internal/render/markdown_test.go

@@ -108,6 +108,48 @@ func TestMarkdownRendererMetadataOnlyWhenRequested(t *testing.T) {
 	}
 }
 
+func TestMarkdownRendererEscapesUserProvidedMarkdown(t *testing.T) {
+	transcript := Transcript{
+		Schema: "seriatim-intermediate",
+		Metadata: Metadata{
+			Application: "seriatim *cli*",
+			Version:     "v[test]",
+		},
+		Segments: []Segment{
+			{
+				ID:      1,
+				Start:   1,
+				End:     2,
+				Speaker: "Dr. *A_[1]",
+				Text:    "Use *literal* [link](target) and `code` \\ slash!",
+			},
+			{
+				ID:         2,
+				Start:      2,
+				End:        3,
+				Speaker:    "Narrator",
+				Text:       "_aside_ with | pipe",
+				Categories: []string{"background"},
+			},
+		},
+	}
+
+	output, err := MarkdownRenderer{}.Render(transcript, Options{
+		Title:             "# Planning [notes]",
+		IncludeTimestamps: false,
+		IncludeMetadata:   true,
+	})
+	if err != nil {
+		t.Fatalf("render markdown: %v", err)
+	}
+
+	assertContains(t, output, "# \\# Planning \\[notes\\]")
+	assertContains(t, output, "- Application: seriatim \\*cli\\*")
+	assertContains(t, output, "- Version: v\\[test\\]")
+	assertContains(t, output, "**Dr. \\*A\\_\\[1\\]:** Use \\*literal\\* \\[link\\]\\(target\\) and \\`code\\` \\\\ slash\\!")
+	assertContains(t, output, "**Narrator:** *\\_aside\\_ with \\| pipe*")
+}
+
 func TestMarkdownRendererCategoryHintItalicsAndUnknownCategories(t *testing.T) {
 	transcript := Transcript{
 		Segments: []Segment{
@@ -176,3 +218,10 @@ func TestMarkdownRendererIsDeterministic(t *testing.T) {
 		t.Fatalf("expected HH:MM:SS timestamp formatting:\n%s", first)
 	}
 }
+
+func assertContains(t *testing.T, value string, want string) {
+	t.Helper()
+	if !strings.Contains(value, want) {
+		t.Fatalf("expected output to contain %q:\n%s", want, value)
+	}
+}