diff --git a/ui/src/components/MarkdownBody.interaction.test.tsx b/ui/src/components/MarkdownBody.interaction.test.tsx
new file mode 100644
index 00000000000..e912a890e47
--- /dev/null
+++ b/ui/src/components/MarkdownBody.interaction.test.tsx
@@ -0,0 +1,95 @@
+// @vitest-environment jsdom
+
+import { flushSync } from "react-dom";
+import { createRoot } from "react-dom/client";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { ThemeProvider } from "../context/ThemeContext";
+import { MarkdownBody } from "./MarkdownBody";
+
+vi.mock("@/lib/router", () => ({
+  Link: ({
+    children,
+    to,
+    ...props
+  }: { children: React.ReactNode; to: string } & React.ComponentProps<"a">) => (
+    <a href={to} {...props}>{children}</a>
+  ),
+}));
+
+vi.mock("../api/issues", () => ({
+  issuesApi: {
+    get: vi.fn(),
+  },
+}));
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+(globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
+
+let root: ReturnType<typeof createRoot> | null = null;
+let container: HTMLDivElement | null = null;
+
+afterEach(() => {
+  if (root) {
+    flushSync(() => root?.unmount());
+  }
+  root = null;
+  container?.remove();
+  container = null;
+});
+
+function renderMarkdown(children: string) {
+  container = document.createElement("div");
+  document.body.appendChild(container);
+  root = createRoot(container);
+  const queryClient = new QueryClient({
+    defaultOptions: {
+      queries: {
+        retry: false,
+      },
+    },
+  });
+
+  flushSync(() => {
+    root?.render(
+      <QueryClientProvider client={queryClient}>
+        <ThemeProvider>
+          <MarkdownBody>{children}</MarkdownBody>
+        </ThemeProvider>
+      </QueryClientProvider>,
+    );
+  });
+
+  return container;
+}
+
+function click(element: Element | null) {
+  if (!element) throw new Error("Expected element to exist");
+  flushSync(() => {
+    element.dispatchEvent(new MouseEvent("click", { bubbles: true }));
+  });
+}
+
+describe("MarkdownBody code block interactions", () => {
+  it("toggles line wrapping for indented preformatted markdown blocks", () => {
+    const node = renderMarkdown("Plan:\n\n    source fetch/sync -> signal inbox");
+    const pre = node.querySelector("pre");
+    const wrapButton = node.querySelector<HTMLButtonElement>(".paperclip-markdown-codeblock-wrap");
+
+    expect(pre?.style.whiteSpace).toBe("");
+    expect(wrapButton?.getAttribute("aria-label")).toBe("Wrap lines");
+
+    click(wrapButton);
+
+    expect(pre?.style.whiteSpace).toBe("pre-wrap");
+    expect(pre?.style.overflowWrap).toBe("anywhere");
+    expect(wrapButton?.getAttribute("aria-pressed")).toBe("true");
+    expect(wrapButton?.getAttribute("aria-label")).toBe("Unwrap lines");
+
+    click(wrapButton);
+
+    expect(pre?.style.whiteSpace).toBe("");
+    expect(wrapButton?.getAttribute("aria-pressed")).toBe("false");
+    expect(wrapButton?.getAttribute("aria-label")).toBe("Wrap lines");
+  });
+});
diff --git a/ui/src/components/MarkdownBody.tsx b/ui/src/components/MarkdownBody.tsx
index 75675a0f695..41ec495a52c 100644
--- a/ui/src/components/MarkdownBody.tsx
+++ b/ui/src/components/MarkdownBody.tsx
@@ -1,6 +1,6 @@
 import { isValidElement, useCallback, useEffect, useId, useRef, useState, type ReactNode } from "react";
 import { useQuery } from "@tanstack/react-query";
-import { Check, Copy, ExternalLink, Github } from "lucide-react";
+import { Check, Copy, ExternalLink, Github, WrapText } from "lucide-react";
 import Markdown, { defaultUrlTransform, type Components, type Options } from "react-markdown";
 import remarkGfm from "remark-gfm";
 import { cn } from "../lib/utils";
@@ -364,6 +364,7 @@ function CodeBlock({
 }) {
   const [copied, setCopied] = useState(false);
   const [failed, setFailed] = useState(false);
+  const [wrapLines, setWrapLines] = useState(false);
   const preRef = useRef<HTMLPreElement>(null);
   const timerRef = useRef<ReturnType<typeof setTimeout>>(undefined);
 
@@ -401,33 +402,57 @@ function CodeBlock({
     }, 1500);
   }, [children]);
 
-  const label = failed ? "Copy failed" : copied ? "Copied!" : "Copy";
+  const copyLabel = failed ? "Copy failed" : copied ? "Copied!" : "Copy";
+  const wrapLabel = wrapLines ? "Unwrap lines" : "Wrap lines";
 
   return (
-    <div className="paperclip-markdown-codeblock">
+    <div className="paperclip-markdown-codeblock" data-wrap-lines={wrapLines || undefined}>
       <pre
         {...preProps}
         ref={preRef}
-        style={mergeScrollableBlockStyle(preProps.style as React.CSSProperties | undefined)}
+        style={{
+          ...mergeScrollableBlockStyle(preProps.style as React.CSSProperties | undefined),
+          ...(wrapLines
+            ? {
+                whiteSpace: "pre-wrap",
+                overflowWrap: "anywhere",
+                wordBreak: "break-word",
+              }
+            : null),
+        }}
       >
         {children}
       </pre>
-      <button
-        type="button"
-        onClick={handleCopy}
-        aria-label="Copy code"
-        title={label}
-        className="paperclip-markdown-codeblock-copy"
-        data-copied={copied || undefined}
-        data-failed={failed || undefined}
-      >
-        {copied && !failed ? (
-          <Check aria-hidden="true" className="h-3.5 w-3.5" />
-        ) : (
-          <Copy aria-hidden="true" className="h-3.5 w-3.5" />
-        )}
-        <span className="paperclip-markdown-codeblock-copy-label">{label}</span>
-      </button>
+      <div className="paperclip-markdown-codeblock-actions">
+        <button
+          type="button"
+          onClick={() => setWrapLines((value) => !value)}
+          aria-label={wrapLabel}
+          title={wrapLabel}
+          className="paperclip-markdown-codeblock-action paperclip-markdown-codeblock-wrap"
+          aria-pressed={wrapLines}
+          data-active={wrapLines || undefined}
+        >
+          <WrapText aria-hidden="true" className="h-3.5 w-3.5" />
+          <span className="paperclip-markdown-codeblock-action-label">{wrapLabel}</span>
+        </button>
+        <button
+          type="button"
+          onClick={handleCopy}
+          aria-label="Copy code"
+          title={copyLabel}
+          className="paperclip-markdown-codeblock-action paperclip-markdown-codeblock-copy"
+          data-copied={copied || undefined}
+          data-failed={failed || undefined}
+        >
+          {copied && !failed ? (
+            <Check aria-hidden="true" className="h-3.5 w-3.5" />
+          ) : (
+            <Copy aria-hidden="true" className="h-3.5 w-3.5" />
+          )}
+          <span className="paperclip-markdown-codeblock-action-label">{copyLabel}</span>
+        </button>
+      </div>
     </div>
   );
 }
diff --git a/ui/src/index.css b/ui/src/index.css
index a29d4b67bc8..82128ed9a02 100644
--- a/ui/src/index.css
+++ b/ui/src/index.css
@@ -717,15 +717,23 @@ a.paperclip-mention-chip[data-mention-kind="agent"]::before {
   background: none;
 }
 
-/* Copy-to-clipboard button on fenced code blocks */
+/* Actions for fenced and indented preformatted markdown blocks */
 .paperclip-markdown-codeblock {
   position: relative;
 }
 
-.paperclip-markdown-codeblock-copy {
+.paperclip-markdown-codeblock-actions {
   position: absolute;
   top: 0.4rem;
   right: 0.4rem;
+  display: inline-flex;
+  align-items: center;
+  gap: 0.25rem;
+  opacity: 0;
+  transition: opacity 0.12s ease;
+}
+
+.paperclip-markdown-codeblock-action {
   display: inline-flex;
   align-items: center;
   gap: 0.25rem;
@@ -737,30 +745,31 @@ a.paperclip-mention-chip[data-mention-kind="agent"]::before {
   font-size: 0.7rem;
   line-height: 1;
   cursor: pointer;
-  opacity: 0;
-  transition: opacity 0.12s ease, background-color 0.12s ease, color 0.12s ease;
+  transition: background-color 0.12s ease, color 0.12s ease;
 }
 
-.paperclip-markdown-codeblock:hover .paperclip-markdown-codeblock-copy,
-.paperclip-markdown-codeblock-copy:focus-visible,
-.paperclip-markdown-codeblock-copy[data-copied] {
+.paperclip-markdown-codeblock:hover .paperclip-markdown-codeblock-actions,
+.paperclip-markdown-codeblock-actions:focus-within,
+.paperclip-markdown-codeblock-action[data-copied],
+.paperclip-markdown-codeblock-action[data-active] {
   opacity: 1;
 }
 
-.paperclip-markdown-codeblock-copy:hover {
+.paperclip-markdown-codeblock-action:hover {
   background-color: var(--accent);
   color: var(--accent-foreground);
 }
 
-.paperclip-markdown-codeblock-copy[data-copied] {
+.paperclip-markdown-codeblock-action[data-active],
+.paperclip-markdown-codeblock-action[data-copied] {
   color: var(--primary);
 }
 
-.paperclip-markdown-codeblock-copy[data-failed] {
+.paperclip-markdown-codeblock-action[data-failed] {
   color: var(--destructive);
 }
 
-.paperclip-markdown-codeblock-copy-label {
+.paperclip-markdown-codeblock-action-label {
   font-weight: 500;
 }