diff --git a/packages/web/server/lib/opencode/settings-helpers.js b/packages/web/server/lib/opencode/settings-helpers.js
index 9393375b..1b7cbbe6 100644
--- a/packages/web/server/lib/opencode/settings-helpers.js
+++ b/packages/web/server/lib/opencode/settings-helpers.js
@@ -565,6 +565,9 @@ export const createSettingsHelpers = (dependencies) => {
         result.userMessageRenderingMode = mode;
       }
     }
+    if (typeof candidate.collapsibleUserMessages === 'boolean') {
+      result.collapsibleUserMessages = candidate.collapsibleUserMessages;
+    }
     if (typeof candidate.stickyUserHeader === 'boolean') {
       result.stickyUserHeader = candidate.stickyUserHeader;
     }
diff --git a/packages/web/server/lib/opencode/settings-helpers.test.js b/packages/web/server/lib/opencode/settings-helpers.test.js
index 3bc30c41..3b80d029 100644
--- a/packages/web/server/lib/opencode/settings-helpers.test.js
+++ b/packages/web/server/lib/opencode/settings-helpers.test.js
@@ -74,6 +74,14 @@ describe('settings helpers', () => {
     expect(helpers.sanitizeSettingsUpdate({ wideChatLayoutEnabled: 'true' })).toEqual({});
   });
 
+  it('accepts only booleans for collapsible user messages', () => {
+    const helpers = createTestHelpers();
+
+    expect(helpers.sanitizeSettingsUpdate({ collapsibleUserMessages: true })).toEqual({ collapsibleUserMessages: true });
+    expect(helpers.sanitizeSettingsUpdate({ collapsibleUserMessages: false })).toEqual({ collapsibleUserMessages: false });
+    expect(helpers.sanitizeSettingsUpdate({ collapsibleUserMessages: 'true' })).toEqual({});
+  });
+
   it('accepts messageStreamTransport as a persisted shared setting', () => {
     const helpers = createTestHelpers();