diff --git a/ui/src/lib/paste-normalization.test.ts b/ui/src/lib/normalize-markdown.test.ts
similarity index 92%
rename from ui/src/lib/paste-normalization.test.ts
rename to ui/src/lib/normalize-markdown.test.ts
index ae1306fa67a..6afeed59102 100644
--- a/ui/src/lib/paste-normalization.test.ts
+++ b/ui/src/lib/normalize-markdown.test.ts
@@ -51,4 +51,9 @@ describe("normalizeMarkdown", () => {
     const expected = "base\n  nested\nback\n    deep";
     expect(normalizeMarkdown(input)).toBe(expected);
   });
+
+  it("leaves mixed tab and space indentation unchanged", () => {
+    const input = "\t# Title\n    body\n\t- item";
+    expect(normalizeMarkdown(input)).toBe(input);
+  });
 });
diff --git a/ui/src/lib/normalize-markdown.ts b/ui/src/lib/normalize-markdown.ts
index a36aadb13fc..6cfc2584309 100644
--- a/ui/src/lib/normalize-markdown.ts
+++ b/ui/src/lib/normalize-markdown.ts
@@ -12,11 +12,18 @@ export function normalizeMarkdown(text: string): string {
 
   // Find minimum indentation across non-empty lines
   let minIndent = Infinity;
+  let indentStyle: "spaces" | "tabs" | null = null;
   for (const line of lines) {
     if (line.trim() === "") continue;
     const match = line.match(/^(\s+)/);
     if (match) {
-      minIndent = Math.min(minIndent, match[1].length);
+      const leadingWhitespace = match[1];
+      const currentStyle = leadingWhitespace.includes("\t") ? "tabs" : "spaces";
+      if (indentStyle && indentStyle !== currentStyle) {
+        return result;
+      }
+      indentStyle = currentStyle;
+      minIndent = Math.min(minIndent, leadingWhitespace.length);
     } else {
       minIndent = 0;
       break;
diff --git a/ui/src/lib/paste-normalization.ts b/ui/src/lib/paste-normalization.ts
index c180b5f719b..c766e201e32 100644
--- a/ui/src/lib/paste-normalization.ts
+++ b/ui/src/lib/paste-normalization.ts
@@ -1,5 +1,6 @@
 import { createRootEditorSubscription$, realmPlugin } from "@mdxeditor/editor";
 import { COMMAND_PRIORITY_CRITICAL, PASTE_COMMAND } from "lexical";
+import { looksLikeMarkdownPaste } from "./markdownPaste";
 import { normalizeMarkdown } from "./normalize-markdown";
 
 /**
@@ -32,6 +33,10 @@ export const pasteNormalizationPlugin = realmPlugin({
             // let the default paste handler deal with rich content as-is.
             if (clipboardData.getData("text/html")) return false;
 
+            // Markdown-looking pastes are handled by MarkdownEditor.tsx via
+            // insertMarkdown(), so the plugin only owns the plain-text fallback.
+            if (looksLikeMarkdownPaste(text)) return false;
+
             const cleaned = normalizeMarkdown(text);
             if (cleaned === text) return false;