diff --git a/backend/src/app/rpc/commands/files_branch.clj b/backend/src/app/rpc/commands/files_branch.clj
index 9bbd09e371..d48d3cdc5e 100644
--- a/backend/src/app/rpc/commands/files_branch.clj
+++ b/backend/src/app/rpc/commands/files_branch.clj
@@ -1733,7 +1733,8 @@
           fb.base_snapshot_id,
           bf.revn AS branch_revn,
           sf.revn AS source_revn,
-          sf.name AS source_name
+          sf.name AS source_name,
+          sf.is_shared AS source_is_shared
      FROM file_branch AS fb
      JOIN file AS bf ON (bf.id = fb.branch_file_id)
      JOIN file AS sf ON (sf.id = fb.source_file_id)
diff --git a/frontend/playwright/data/pull-requests/get-file-blank-shared.json b/frontend/playwright/data/pull-requests/get-file-blank-shared.json
new file mode 100644
index 0000000000..9a09260ac5
--- /dev/null
+++ b/frontend/playwright/data/pull-requests/get-file-blank-shared.json
@@ -0,0 +1,58 @@
+{
+  "~:features": {
+    "~#set": [
+      "layout/grid",
+      "styles/v2",
+      "fdata/pointer-map",
+      "fdata/objects-map",
+      "components/v2",
+      "fdata/shape-data-type"
+    ]
+  },
+  "~:permissions": {
+    "~:type": "~:membership",
+    "~:is-owner": true,
+    "~:is-admin": true,
+    "~:can-edit": true,
+    "~:can-read": true,
+    "~:is-logged": true
+  },
+  "~:has-media-trimmed": false,
+  "~:comment-thread-seqn": 0,
+  "~:name": "New File 1",
+  "~:revn": 11,
+  "~:modified-at": "~m1713873823633",
+  "~:id": "~uc7ce0794-0992-8105-8004-38f280443849",
+  "~:is-shared": true,
+  "~:version": 46,
+  "~:project-id": "~uc7ce0794-0992-8105-8004-38e630f7920b",
+  "~:created-at": "~m1713536343369",
+  "~:data": {
+    "~:pages": [
+      "~u66697432-c33d-8055-8006-2c62cc084cad"
+    ],
+    "~:pages-index": {
+      "~u66697432-c33d-8055-8006-2c62cc084cad": {
+        "~#penpot/pointer": [
+          "~ude58c8f6-c5c2-8196-8004-3df9e2e52d88",
+          {
+            "~:created-at": "~m1713873823636"
+          }
+        ]
+      }
+    },
+    "~:id": "~uc7ce0794-0992-8105-8004-38f280443849",
+    "~:options": {
+      "~:components-v2": true
+    },
+    "~:recent-colors": [
+      {
+        "~:color": "#0000ff",
+        "~:opacity": 1,
+        "~:id": null,
+        "~:file-id": null,
+        "~:image": null
+      }
+    ]
+  }
+}
\ No newline at end of file
diff --git a/frontend/playwright/data/pull-requests/get-file-branch-info-library-branch.json b/frontend/playwright/data/pull-requests/get-file-branch-info-library-branch.json
new file mode 100644
index 0000000000..848706e76a
--- /dev/null
+++ b/frontend/playwright/data/pull-requests/get-file-branch-info-library-branch.json
@@ -0,0 +1,16 @@
+{
+  "~:id": "~uc7ce0794-0992-8105-8004-38f280443998",
+  "~:branch-file-id": "~uc7ce0794-0992-8105-8004-38f280443849",
+  "~:source-file-id": "~uc7ce0794-0992-8105-8004-38f280443997",
+  "~:name": "checkout",
+  "~:description": null,
+  "~:status": "open",
+  "~:created-by": "~uc7ce0794-0992-8105-8004-38e630f29a9b",
+  "~:created-at": "~m1713536343369",
+  "~:updated-at": "~m1713873823633",
+  "~:source-name": "New File 1",
+  "~:ahead": 1,
+  "~:behind": 0,
+  "~:conflicts": 0,
+  "~:source-is-shared": true
+}
diff --git a/frontend/playwright/data/pull-requests/get-file-branches-one.json b/frontend/playwright/data/pull-requests/get-file-branches-one.json
new file mode 100644
index 0000000000..9fd1b73fb8
--- /dev/null
+++ b/frontend/playwright/data/pull-requests/get-file-branches-one.json
@@ -0,0 +1,17 @@
+[
+  {
+    "~:id": "~uc7ce0794-0992-8105-8004-38f280443998",
+    "~:branch-file-id": "~uc7ce0794-0992-8105-8004-38f280443850",
+    "~:source-file-id": "~uc7ce0794-0992-8105-8004-38f280443849",
+    "~:name": "checkout",
+    "~:description": null,
+    "~:status": "open",
+    "~:created-by": "~uc7ce0794-0992-8105-8004-38e630f29a9b",
+    "~:created-at": "~m1713536343369",
+    "~:updated-at": "~m1713873823633",
+    "~:source-name": "New File 1",
+    "~:ahead": 1,
+    "~:behind": 0,
+    "~:conflicts": 0
+  }
+]
diff --git a/frontend/playwright/ui/specs/branches-library.spec.js b/frontend/playwright/ui/specs/branches-library.spec.js
new file mode 100644
index 0000000000..ac135712e6
--- /dev/null
+++ b/frontend/playwright/ui/specs/branches-library.spec.js
@@ -0,0 +1,80 @@
+import { test, expect } from "@playwright/test";
+import { WorkspacePage } from "../pages/WorkspacePage";
+
+test.beforeEach(async ({ page }) => {
+  await WorkspacePage.init(page);
+  await WorkspacePage.mockConfigFlags(page, ["enable-branching"]);
+});
+
+const setupBranching = async (workspacePage, rpcs) => {
+  await workspacePage.setupEmptyFile();
+  await workspacePage.mockRPCs({
+    "get-file-branch-info?file-id=*":
+      "pull-requests/get-file-branch-info-none.json",
+    "get-file-branches?file-id=*": "pull-requests/get-file-branches-empty.json",
+    "get-file-pull-requests?file-id=*":
+      "pull-requests/get-file-branches-empty.json",
+    ...rpcs,
+  });
+};
+
+test("on a branch of a library, the header says consumers read main", async ({
+  page,
+}) => {
+  const workspacePage = new WorkspacePage(page);
+  await setupBranching(workspacePage, {
+    "get-file-branch-info?file-id=*":
+      "pull-requests/get-file-branch-info-library-branch.json",
+  });
+  await workspacePage.goToWorkspace();
+
+  const chip = page.getByTitle(
+    "On branch checkout from main. Library consumers can adopt changes from main only.",
+  );
+  await expect(chip).toBeVisible();
+
+  await chip.click();
+  await expect(
+    page.getByText("Default branch (read by library consumers)"),
+  ).toBeVisible();
+});
+
+test("on a library, the create dialog says consumers read main", async ({
+  page,
+}) => {
+  const workspacePage = new WorkspacePage(page);
+  await setupBranching(workspacePage, {
+    "get-file-branches?file-id=*": "pull-requests/get-file-branches-one.json",
+  });
+  await workspacePage.mockGetFile("pull-requests/get-file-blank-shared.json");
+  await workspacePage.goToWorkspace();
+
+  await expect(
+    page.getByText("Default branch (read by library consumers)"),
+  ).toBeVisible();
+
+  await page.getByTitle("Switch branch").click();
+  await page.getByText("New branch").click();
+  await expect(
+    page.getByText(
+      "files that use this library can adopt changes from main only",
+    ),
+  ).toBeVisible();
+});
+
+test("on an ordinary file, the create dialog keeps its note", async ({
+  page,
+}) => {
+  const workspacePage = new WorkspacePage(page);
+  await setupBranching(workspacePage, {
+    "get-file-branches?file-id=*": "pull-requests/get-file-branches-one.json",
+  });
+  await workspacePage.goToWorkspace();
+
+  await expect(page.getByText("Default branch", { exact: true })).toBeVisible();
+
+  await page.getByTitle("Switch branch").click();
+  await page.getByText("New branch").click();
+  await expect(page.getByText("isolated copy")).toBeVisible();
+  await expect(page.getByText("files that use this library")).toBeHidden();
+});
diff --git a/frontend/src/app/main/ui/workspace/branch_switcher.cljs b/frontend/src/app/main/ui/workspace/branch_switcher.cljs
index 15e1c027bb..50a6de071a 100644
--- a/frontend/src/app/main/ui/workspace/branch_switcher.cljs
+++ b/frontend/src/app/main/ui/workspace/branch_switcher.cljs
@@ -81,6 +81,14 @@
        (zero? (or (:behind row) 0))
        (zero? (or (:conflicts row) 0))))
 
+(defn- main-subtitle
+  "The note beside main. Files that use a shared library read its main,
+  so on a library it says so."
+  [library?]
+  (if library?
+    (tr "workspace.branches.main-subtitle-library")
+    (tr "workspace.branches.main-subtitle")))
+
 ;; --- Popover
 
 (mf/defc switcher-row*
@@ -92,7 +100,7 @@
                     :data-branch (dm/str (:branch-file-id row))
                     :on-click on-open}
     (if (:is-main row)
-      (tr "workspace.branches.main-subtitle")
+      (main-subtitle (:is-library row))
       [:> row-status* {:row row :pr pr}])]])
 
 (mf/defc switcher-popover*
@@ -115,6 +123,7 @@
         (when-not (:is-main current)
           {:name (tr "workspace.branches.main")
            :is-main true
+           :is-library (boolean (:source-is-shared current))
            :branch-file-id (:source-file-id current)})
 
         rows
@@ -234,6 +243,7 @@
         (or ctx
             {:name (tr "workspace.branches.main")
              :is-main true
+             :is-library (boolean (:is-shared file))
              :created-by (:id profile)
              :branch-file-id file-id})
 
@@ -275,8 +285,16 @@
       [:div {:class (stl/css :branch-bar) :ref bar-ref}
        [:> branch-chip* {:label (:name current)
                          :is-open open?
-                         :title (if (:is-main current)
+                         :title (cond
+                                  (:is-main current)
                                   (tr "workspace.branches.switcher.tooltip")
+
+                                  ;; files that use the library read main,
+                                  ;; never this branch
+                                  (:source-is-shared current)
+                                  (tr "workspace.branches.header-badge-tooltip-library" (:name current))
+
+                                  :else
                                   (tr "workspace.branches.header-badge-tooltip" (:name current)))
                          :on-click on-toggle}]
 
@@ -288,7 +306,7 @@
            [:> text* {:as "span"
                       :typography t/body-small
                       :class (stl/css :status-note)}
-            (tr "workspace.branches.main-subtitle")]
+            (main-subtitle (:is-shared file))]
 
            ^boolean merged?
            nil
diff --git a/frontend/src/app/main/ui/workspace/sidebar/branches.cljs b/frontend/src/app/main/ui/workspace/sidebar/branches.cljs
index b3fede1741..4a18539dba 100644
--- a/frontend/src/app/main/ui/workspace/sidebar/branches.cljs
+++ b/frontend/src/app/main/ui/workspace/sidebar/branches.cljs
@@ -224,7 +224,9 @@
   {::mf/register modal/components
    ::mf/register-as :create-branch}
   [{:keys [file-name file-id]}]
-  (let [branch-name* (mf/use-state "")
+  (let [;; a branch only grows from main, so the open file is main
+        library?     (boolean (:is-shared (mf/deref refs/file)))
+        branch-name* (mf/use-state "")
         description*  (mf/use-state "")
         branch-name   (deref branch-name*)
         description   (deref description*)
@@ -279,7 +281,9 @@
          (tr "workspace.branches.create.derive-from-latest")]]]
 
       [:> context-notification* {:level :info :type :context}
-       (tr "workspace.branches.create.info")]]
+       (if library?
+         (tr "workspace.branches.create.info-library")
+         (tr "workspace.branches.create.info"))]]
 
      [:> modal-footer* {}
       [:> button* {:variant "secondary" :on-click on-close}
diff --git a/frontend/translations/en.po b/frontend/translations/en.po
index 3f7af349ea..022b3ae1c9 100644
--- a/frontend/translations/en.po
+++ b/frontend/translations/en.po
@@ -6808,6 +6808,12 @@ msgstr ""
 "Your branch is a complete, isolated copy. Nothing you do affects main until "
 "you merge it."
 
+#: src/app/main/ui/workspace/sidebar/branches.cljs:283
+msgid "workspace.branches.create.info-library"
+msgstr ""
+"Your branch is a complete copy. Nothing you do affects main until you merge "
+"it, and files that use this library can adopt changes from main only."
+
 #: src/app/main/ui/workspace/sidebar/branches.cljs:283
 msgid "workspace.branches.create.name-label"
 msgstr "Branch name"
@@ -6849,6 +6855,10 @@ msgstr "No branches yet"
 msgid "workspace.branches.header-badge-tooltip"
 msgstr "On branch %s from main"
 
+#: src/app/main/ui/workspace/branch_switcher.cljs:295
+msgid "workspace.branches.header-badge-tooltip-library"
+msgstr "On branch %s from main. Library consumers can adopt changes from main only."
+
 #: src/app/main/ui/workspace/sidebar/branches.cljs:485
 msgid "workspace.branches.info.author"
 msgstr "Created by"
@@ -7070,6 +7080,10 @@ msgstr "Main has new changes. You can update this branch"
 msgid "workspace.branches.main-subtitle"
 msgstr "Default branch"
 
+#: src/app/main/ui/workspace/branch_switcher.cljs:88
+msgid "workspace.branches.main-subtitle-library"
+msgstr "Default branch (read by library consumers)"
+
 #: src/app/main/ui/workspace/sidebar/branches.cljs:779
 msgid "workspace.branches.materialize.accept"
 msgstr "Turn it into a file"