diff --git a/ui/src/components/MarkdownBody.tsx b/ui/src/components/MarkdownBody.tsx
index b1f2212685..a26cafac79 100644
--- a/ui/src/components/MarkdownBody.tsx
+++ b/ui/src/components/MarkdownBody.tsx
@@ -231,7 +231,7 @@ const codeBlockActionsStyle: React.CSSProperties = {
   gap: "0.25rem",
 };
 
-const codeBlockActionStyle: React.CSSProperties = {
+export const codeBlockActionStyle: React.CSSProperties = {
   position: "static",
   opacity: 1,
   display: "inline-flex",
@@ -242,7 +242,7 @@ const codeBlockActionStyle: React.CSSProperties = {
   padding: "0.2rem 0.4rem",
   borderRadius: "calc(var(--radius) - 4px)",
   border: "1px solid color-mix(in oklab, var(--foreground) 14%, transparent)",
-  backgroundColor: "color-mix(in oklab, var(--muted) 92%, var(--background) 8%)",
+  backgroundColor: "var(--background)",
   color: "var(--muted-foreground)",
   fontSize: "var(--text-micro)",
   lineHeight: 1,
diff --git a/ui/src/components/MarkdownCodeBlockStyles.test.ts b/ui/src/components/MarkdownCodeBlockStyles.test.ts
new file mode 100644
index 0000000000..f269e90bf8
--- /dev/null
+++ b/ui/src/components/MarkdownCodeBlockStyles.test.ts
@@ -0,0 +1,70 @@
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { describe, expect, it } from "vitest";
+
+import { codeBlockActionStyle } from "./MarkdownBody";
+
+const stylesheet = readFileSync(fileURLToPath(new URL("../index.css", import.meta.url)), "utf8");
+
+function cssBlock(selector: string): string {
+  const start = stylesheet.indexOf(`${selector} {`);
+  expect(start, `Missing CSS selector: ${selector}`).toBeGreaterThanOrEqual(0);
+
+  const bodyStart = stylesheet.indexOf("{", start);
+  const bodyEnd = stylesheet.indexOf("\n}", bodyStart);
+  expect(bodyStart, `Missing CSS block start: ${selector}`).toBeGreaterThanOrEqual(0);
+  expect(bodyEnd, `Missing CSS block end: ${selector}`).toBeGreaterThan(bodyStart);
+
+  return stylesheet.slice(bodyStart + 1, bodyEnd);
+}
+
+/* The rendered code block used to be pinned to the Catppuccin literals
+   #1e1e2e / #cdd6f4, in the normal AND the prose-invert variables. A code
+   block therefore stayed dark in light mode. These tests fail if any of
+   those surfaces is pinned to a literal again, rather than riding a token
+   that carries a `.dark` override. */
+
+describe("markdown code block styles", () => {
+  it("rides theme tokens for the rendered code block surface", () => {
+    const block = cssBlock(".paperclip-markdown pre");
+
+    expect(block).toContain("background-color: var(--muted)");
+    expect(block).toContain("color: var(--foreground)");
+    expect(block).toContain("border: 1px solid var(--border)");
+    expect(block).toContain("border-radius: var(--radius-lg)");
+  });
+
+  it("rides theme tokens for the editor content code block surface", () => {
+    const block = cssBlock(".paperclip-mdxeditor-content pre");
+
+    expect(block).toContain("background: var(--muted)");
+    expect(block).toContain("color: var(--foreground)");
+    expect(block).toContain("border: 1px solid var(--border)");
+    expect(block).toContain("border-radius: var(--radius-lg)");
+  });
+
+  it("points the normal and inverted prose variables at the same tokens", () => {
+    const block = cssBlock(".paperclip-markdown");
+
+    expect(block).toContain("--tw-prose-pre-bg: var(--muted)");
+    expect(block).toContain("--tw-prose-pre-code: var(--foreground)");
+    expect(block).toContain("--tw-prose-invert-pre-bg: var(--muted)");
+    expect(block).toContain("--tw-prose-invert-pre-code: var(--foreground)");
+  });
+
+  it("keeps every themed code surface free of hardcoded colors", () => {
+    for (const selector of [".paperclip-markdown pre", ".paperclip-mdxeditor-content pre", ".paperclip-markdown"]) {
+      // Any hex literal, or an rgb()/hsl() literal, re-pins the surface to one mode.
+      expect(cssBlock(selector), `${selector} must not hardcode a color`).not.toMatch(
+        /#[0-9a-f]{3,8}\b|\brgba?\(|\bhsla?\(/i,
+      );
+    }
+  });
+
+  it("separates the copy and wrap controls from the code block surface", () => {
+    // The controls sit on top of the block. --muted is now the block's own
+    // fill, so the controls must not use it or they disappear against it.
+    expect(codeBlockActionStyle.backgroundColor).toBe("var(--background)");
+    expect(codeBlockActionStyle.backgroundColor).not.toContain("--muted");
+  });
+});
diff --git a/ui/src/index.css b/ui/src/index.css
index f8792195e3..2bc7bc81de 100644
--- a/ui/src/index.css
+++ b/ui/src/index.css
@@ -1406,10 +1406,10 @@ a.paperclip-mention-chip[data-mention-kind="agent"]::before {
 .paperclip-mdxeditor-content pre {
   margin: 0.4rem 0;
   padding: 0;
-  border: 1px solid color-mix(in oklab, var(--foreground) 12%, transparent);
-  border-radius: calc(var(--radius) - 3px);
-  background: #1e1e2e;
-  color: #cdd6f4;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-lg);
+  background: var(--muted);
+  color: var(--foreground);
   overflow-x: auto;
 }
 
@@ -1482,20 +1482,22 @@ a.paperclip-mention-chip[data-mention-kind="agent"]::before {
 }
 
 /* Rendered markdown code blocks & inline code (prose/MarkdownBody context).
-   Dark theme code blocks with compact sizing.
-   Override prose CSS variables so prose-invert can't revert to defaults. */
+   Theme-aware: the block rides --muted/--foreground/--border so it follows
+   light and dark instead of pinning the old Catppuccin #1e1e2e/#cdd6f4 in
+   both modes. Override prose CSS variables so prose-invert can't revert to
+   defaults. */
 .paperclip-markdown {
-  --tw-prose-pre-bg: #1e1e2e;
-  --tw-prose-pre-code: #cdd6f4;
-  --tw-prose-invert-pre-bg: #1e1e2e;
-  --tw-prose-invert-pre-code: #cdd6f4;
+  --tw-prose-pre-bg: var(--muted);
+  --tw-prose-pre-code: var(--foreground);
+  --tw-prose-invert-pre-bg: var(--muted);
+  --tw-prose-invert-pre-code: var(--foreground);
 }
 
 .paperclip-markdown pre {
-  border: 1px solid color-mix(in oklab, var(--foreground) 12%, transparent) !important;
-  border-radius: calc(var(--radius) - 3px) !important;
-  background-color: #1e1e2e !important;
-  color: #cdd6f4 !important;
+  border: 1px solid var(--border) !important;
+  border-radius: var(--radius-lg) !important;
+  background-color: var(--muted) !important;
+  color: var(--foreground) !important;
   padding: 0.5rem 0.65rem !important;
   margin: 0.4rem 0 !important;
   font-size: 1em !important;