diff --git a/apps/app/src/components/plugin/PluginNewThreadComposer.test.tsx b/apps/app/src/components/plugin/PluginNewThreadComposer.test.tsx
--- a/apps/app/src/components/plugin/PluginNewThreadComposer.test.tsx
+++ b/apps/app/src/components/plugin/PluginNewThreadComposer.test.tsx
@@
+  it("marks a provider picked in an unseeded plugin composer as explicit", async () => {
+    const submitted: NewThreadRequest[] = [];
+    render(
+      <MemoryRouter>
+        <PluginNewThreadComposer
+          draftKey="picked-provider"
+          defaultProjectId="proj_1"
+          initialPrompt="hello"
+          onSubmit={(request) => {
+            submitted.push(request);
+          }}
+        />
+      </MemoryRouter>,
+    );
+
+    await waitFor(() => {
+      expect(latestPromptBoxProps().disabled).toBe(false);
+    });
+    await act(async () => {
+      latestPromptBoxProps().execution.provider.onChange("claude-code");
+    });
+    await waitFor(() => {
+      expect(latestPromptBoxProps().execution.provider.selectedId).toBe(
+        "claude-code",
+      );
+      expect(latestPromptBoxProps().disabled).toBe(false);
+    });
+    await submit();
+
+    expect(submitted).toHaveLength(1);
+    expect(submitted[0]?.providerId).toBe("claude-code");
+    expect(submitted[0]?.executionInputSources.providerId).toBe("explicit");
+  });