diff --git a/.changeset/devtools-panel-theme.md b/.changeset/devtools-panel-theme.md
new file mode 100644
index 0000000..3e503df
--- /dev/null
+++ b/.changeset/devtools-panel-theme.md
@@ -0,0 +1,7 @@
+---
+"@paramour-js/devtools-panel": major
+---
+
+The devtools panel now follows the TanStack Devtools theme. Before this fix it always rendered light, even in a dark shell. The shell passes its theme only to a plugin's `render` function and renders an element `render` as-is, so `paramourDevtoolsPlugin()` now returns `render` as `(el, { theme }) => <ParamourDevtoolsPanel theme={theme} />`.
+
+**Breaking (types):** `ParamourDevtoolsPluginEntry.render` changes from `ReactElement` to `(el: HTMLElement, props: { readonly theme: "dark" | "light" }) => ReactElement`. Passing the entry to `<TanStackDevtools plugins={[paramourDevtoolsPlugin()]} />` is unchanged. Only code that reads `entry.render` as an element needs updating. Call it with the shell's theme or render `<ParamourDevtoolsPanel theme={…} />` directly.
diff --git a/docs/content/docs/guides/devtools.mdx b/docs/content/docs/guides/devtools.mdx
index b82d34c..5663d7e 100644
--- a/docs/content/docs/guides/devtools.mdx
+++ b/docs/content/docs/guides/devtools.mdx
@@ -73,7 +73,8 @@ nothing to register per route.
 `paramourDevtoolsPlugin({ defaultOpen: true })` opens the panel on load if
 you want it in your face during a debugging session. If you're composing a
 custom devtools shell, `ParamourDevtoolsPanel` is also exported directly —
-the plugin helper is just `{ id, name, render: <ParamourDevtoolsPanel /> }`.
+the plugin helper is just
+`{ id, name, render: (_el, { theme }) => <ParamourDevtoolsPanel theme={theme} /> }`.
 
 ## Production cost: none
 
diff --git a/docs/content/docs/reference/devtools.mdx b/docs/content/docs/reference/devtools.mdx
index a4ac2bb..cede90f 100644
--- a/docs/content/docs/reference/devtools.mdx
+++ b/docs/content/docs/reference/devtools.mdx
@@ -46,8 +46,8 @@ export function Devtools() {
 
 `defaultOpen: true` opens the panel on load — useful when you want it in
 your face during a debugging session. That's the only option; the helper
-just builds `{ id, name, render }` with the panel component as `render`,
-plus the flag.
+just builds `{ id, name, render }`, where `render` mounts the panel with the
+shell's theme, plus the flag.
 
 Gotchas:
 
@@ -87,8 +87,9 @@ export function CustomShellPanel({ theme }: { theme: "dark" | "light" }) {
 `theme` selects the panel's token set via a `data-theme` attribute (no
 theme context, no remount) and defaults to `"light"`. When the panel is
 mounted through [`paramourDevtoolsPlugin`](#paramourdevtoolsplugin) you
-never pass it — the TanStack shell clones the rendered element and injects
-`theme` itself; the prop exists for shells that don't.
+never pass it: the TanStack shell calls the plugin's `render` function with
+its current theme, and the panel follows the shell's theme setting live.
+In a custom shell, pass `theme` yourself.
 
 ## ParamourDevtoolsPluginEntry
 
@@ -99,14 +100,19 @@ interface ParamourDevtoolsPluginEntry {
   readonly defaultOpen?: boolean;
   readonly id: string;
   readonly name: string;
-  readonly render: ReactElement;
+  readonly render: (
+    el: HTMLElement,
+    props: { readonly theme: "dark" | "light" },
+  ) => ReactElement;
 }
 ```
 
 Declared *structurally* — the shell's contract is just
 `name`/`render`/`id`/`defaultOpen` — so this package never imports
 `@tanstack/react-devtools` at runtime; assignability to the real plugin
-type is certified by the package's type tests.
+type is certified by the package's type tests. `render` is a function
+because the shell passes its theme only to function renders. It renders
+an element `render` as-is.
 
 ```ts twoslash
 import { paramourDevtoolsPlugin } from "@paramour-js/devtools-panel";
diff --git a/packages/devtools/src/components/panel.tsx b/packages/devtools/src/components/panel.tsx
index 9cd95ea..815523f 100644
--- a/packages/devtools/src/components/panel.tsx
+++ b/packages/devtools/src/components/panel.tsx
@@ -10,9 +10,9 @@ import { Sidebar } from "./sidebar.js";
 
 export interface ParamourDevtoolsPanelProps {
   /**
-   * Injected by the TanStack shell (the one contract it guarantees every
-   * panel, regardless of framework); selects the stylesheet's token set via
-   * a `data-theme` attribute — no theme context, no remount.
+   * The shell's theme, passed through by `paramourDevtoolsPlugin()`'s
+   * render function; selects the stylesheet's token set via a `data-theme`
+   * attribute — no theme context, no remount.
    */
   readonly theme?: "dark" | "light";
 }
diff --git a/packages/devtools/src/plugin.tsx b/packages/devtools/src/plugin.tsx
index 5672cb8..fbf2a0a 100644
--- a/packages/devtools/src/plugin.tsx
+++ b/packages/devtools/src/plugin.tsx
@@ -9,13 +9,21 @@ import { ParamourDevtoolsPanel } from "./components/panel.js";
  * entry type is declared STRUCTURALLY (the shell's contract is just
  * name/render/id/defaultOpen) so this module never imports the shell at
  * runtime; assignability to the real plugin type is certified by the
- * package's type tests. The shell clones `render` and injects `theme`.
+ * package's type tests.
+ *
+ * `render` is a function because that is the only way the panel receives
+ * the shell's theme: the shell calls a function render as
+ * `render(el, { theme, devtoolsOpen })` whenever its theme changes, and
+ * renders an element as-is with no props injected.
  */
 export interface ParamourDevtoolsPluginEntry {
   readonly defaultOpen?: boolean;
   readonly id: string;
   readonly name: string;
-  readonly render: ReactElement;
+  readonly render: (
+    el: HTMLElement,
+    props: { readonly theme: "dark" | "light" },
+  ) => ReactElement;
 }
 
 export interface ParamourDevtoolsPluginOptions {
@@ -31,6 +39,6 @@ export function paramourDevtoolsPlugin(
       : { defaultOpen: options.defaultOpen }),
     id: "paramour-devtools",
     name: "Paramour",
-    render: <ParamourDevtoolsPanel />,
+    render: (_el, { theme }) => <ParamourDevtoolsPanel theme={theme} />,
   };
 }
diff --git a/packages/devtools/test/public-api.tst.tsx b/packages/devtools/test/public-api.tst.tsx
index 19b53f2..006a3b4 100644
--- a/packages/devtools/test/public-api.tst.tsx
+++ b/packages/devtools/test/public-api.tst.tsx
@@ -48,7 +48,14 @@ test("plugin helper returns the entry shape", () => {
   expect(
     paramourDevtoolsPlugin({ defaultOpen: true }),
   ).type.toBe<ParamourDevtoolsPluginEntry>();
-  expect(paramourDevtoolsPlugin().render).type.toBeAssignableTo<ReactElement>();
+  // A function, not an element: the shell passes the theme only to a
+  // function render.
+  expect(paramourDevtoolsPlugin().render).type.toBe<
+    (
+      el: HTMLElement,
+      props: { readonly theme: "dark" | "light" },
+    ) => ReactElement
+  >();
 });
 
 test("the entry is assignable to the REAL shell's plugins array", () => {
diff --git a/packages/devtools/test/theme.test.tsx b/packages/devtools/test/theme.test.tsx
index f3a1b2a..8b6875b 100644
--- a/packages/devtools/test/theme.test.tsx
+++ b/packages/devtools/test/theme.test.tsx
@@ -4,6 +4,7 @@ import { defineAppRoute } from "paramour";
 import { afterEach, describe, expect, it } from "vitest";
 
 import { ParamourDevtoolsPanel } from "../src/components/panel.js";
+import { paramourDevtoolsPlugin } from "../src/plugin.js";
 import { freshSeam, paramsObservation, setUrl } from "./helpers.js";
 
 const route = defineAppRoute("/home", {});
@@ -28,6 +29,23 @@ describe("theme switching", () => {
     expect(root?.getAttribute("data-theme")).toBe("dark");
   });
 
+  it("the plugin entry renders the theme the shell passes to render()", () => {
+    // TanStack's shell calls a function render as render(el, { theme, … })
+    // on every theme change; an element render never receives the theme.
+    freshSeam();
+    const entry = paramourDevtoolsPlugin();
+    const host = document.createElement("div");
+    const { container, rerender } = render(
+      entry.render(host, { theme: "dark" }),
+    );
+    const root = container.querySelector(".pmr-root");
+    expect(root?.getAttribute("data-theme")).toBe("dark");
+
+    rerender(entry.render(host, { theme: "light" }));
+    expect(container.querySelector(".pmr-root")).toBe(root);
+    expect(root?.getAttribute("data-theme")).toBe("light");
+  });
+
   it("defaults to light when the shell passes no theme", () => {
     freshSeam();
     const { container } = render(<ParamourDevtoolsPanel />);