diff --git a/.changeset/theme-shape-render-call.md b/.changeset/theme-shape-render-call.md
new file mode 100644
--- /dev/null
+++ b/.changeset/theme-shape-render-call.md
@@ -0,0 +1,5 @@
+---
+"@aliou/pi-processes": patch
+---
+
+Detect tool render themes by shape instead of class identity so Pi and oh-my-pi render process calls correctly when package copies differ.
diff --git a/extensions/processes/tools/index.test.ts b/extensions/processes/tools/index.test.ts
--- a/extensions/processes/tools/index.test.ts
+++ b/extensions/processes/tools/index.test.ts
@@ -13,7 +13,7 @@
  */
 import {
   type ExtensionAPI,
-  Theme,
+  type Theme,
   type ToolDefinition,
 } from "@earendil-works/pi-coding-agent";
 import { describe, expect, it, vi } from "vitest";
@@ -32,13 +32,8 @@
   third?: RenderCallFnContext | Theme,
 ) => ReturnType<RenderCallFn>;
 
-/** pi's theme: a real Theme instance (passes `instanceof Theme`). */
-const piTheme = Object.create(Theme.prototype) as Theme;
-piTheme.fg = (_color: string, text: string) => text;
-piTheme.bold = (text: string) => text;
-
-/** OMP's theme: same surface, but not a pi Theme instance. */
-const ompTheme = {
+/** Theme-like object, as passed by host Pi/OMP package copies. */
+const theme = {
   fg: (_color: string, text: string) => text,
   bold: (text: string) => text,
 } as Theme;
@@ -54,7 +49,7 @@
 describe("renderCall host argument order", () => {
   it("renders with pi order: (args, theme, context)", () => {
     const renderCall = captureRenderCall();
-    const component = renderCall({ action: "list" }, piTheme, {
+    const component = renderCall({ action: "list" }, theme, {
       expanded: false,
     } as RenderCallFnContext);
     expect(component.render(80).join("\n")).toContain("Process:");
@@ -65,7 +60,7 @@
     const component = renderCall(
       { action: "list" },
       { expanded: false, isPartial: true } as RenderCallFnContext,
-      ompTheme,
+      theme,
     );
     expect(component.render(80).join("\n")).toContain("Process:");
   });
diff --git a/extensions/processes/tools/index.ts b/extensions/processes/tools/index.ts
--- a/extensions/processes/tools/index.ts
+++ b/extensions/processes/tools/index.ts
@@ -3,7 +3,7 @@
   defineTool,
   type ExtensionAPI,
   type ExtensionContext,
-  Theme,
+  type Theme,
   type ToolDefinition,
 } from "@earendil-works/pi-coding-agent";
 import { type Component, Container, Text } from "@earendil-works/pi-tui";
@@ -112,13 +112,17 @@
 type RenderCallFnContext = Parameters<RenderCallFn>[2];
 
 /**
- * pi invokes renderCall as (args, theme, context) where theme is pi's Theme
- * class instance. Detecting that exact class distinguishes pi's argument
- * order from OMP's (args, options, theme), where the second argument is a
- * plain options object.
+ * pi invokes renderCall as (args, theme, context), while OMP invokes it as
+ * (args, options, theme). Detect the theme by shape instead of Theme class
+ * identity because host and extension package copies can differ.
  */
-function isPiTheme(value: unknown): value is Theme {
-  return value instanceof Theme;
+function isThemeLike(value: unknown): value is Theme {
+  return (
+    typeof value === "object" &&
+    value !== null &&
+    typeof (value as { fg?: unknown }).fg === "function" &&
+    typeof (value as { bold?: unknown }).bold === "function"
+  );
 }
 
 function renderProcessCall(
@@ -126,7 +130,7 @@
   second: Theme | RenderCallFnContext,
   third?: RenderCallFnContext | Theme,
 ): Component {
-  const usesPiOrder = isPiTheme(second);
+  const usesPiOrder = isThemeLike(second);
   const theme = usesPiOrder ? second : (third as Theme);
   const context = (usesPiOrder ? third : second) as
     | RenderCallFnContext