Addons: default PR build notification to off for new projects (#12934)

The "created from a pull request build" toast was on by default, but
visual diff is doing most of the work that it does much less
intrusively. Flip it to opt-in for new projects; existing projects keep
their value (schema-only migration).

Companion to #12932.

Generated by Claude Code.

---------

Co-authored-by: Claude <noreply@anthropic.com>

Author: ericholscher

docs/user/pull-requests.rst

@@ -33,8 +33,10 @@ Build overview with changed files
        This feature is only available for projects connected to a :ref:`reference/git-integration:GitHub App`.
 
 Pull request notifications
-    A pull request notifications is shown at the top of preview pages,
+    A pull request notification can be shown at the top of preview pages,
     which let readers know they aren't viewing an active version of the project.
+    New projects have this notification disabled by default;
+    enable it from :guilabel:`Settings` → :guilabel:`Addons` → :guilabel:`Notifications`.
 
 :doc:`Visual diff </visual-diff>`
     Visual diff shows proposed changes by visually highlighting the differences between the current pull request and the latest version of the project's documentation.

readthedocs/projects/migrations/0161_addons_notifications_show_on_external_default_false.py

@@ -0,0 +1,42 @@
+# Generated by Django 5.2.12 on 2026-04-14 00:00
+
+from django.db import migrations
+from django.db import models
+from django_safemigrate import Safe
+
+
+class Migration(migrations.Migration):
+    safe = Safe.before_deploy()
+
+    dependencies = [
+        ("projects", "0160_notifications_show_on_external_help_text"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="addonsconfig",
+            name="notifications_show_on_external",
+            field=models.BooleanField(
+                default=False,
+                help_text=(
+                    "Display a notification on the rendered documentation of pull "
+                    "request previews. Readers will see a toast linking to the "
+                    "build and the pull request."
+                ),
+                verbose_name="Show a notification on builds from pull requests",
+            ),
+        ),
+        migrations.AlterField(
+            model_name="historicaladdonsconfig",
+            name="notifications_show_on_external",
+            field=models.BooleanField(
+                default=False,
+                help_text=(
+                    "Display a notification on the rendered documentation of pull "
+                    "request previews. Readers will see a toast linking to the "
+                    "build and the pull request."
+                ),
+                verbose_name="Show a notification on builds from pull requests",
+            ),
+        ),
+    ]

readthedocs/projects/models.py

@@ -261,7 +261,7 @@ class AddonsConfig(TimeStampedModel):
     notifications_show_on_latest = models.BooleanField(default=True)
     notifications_show_on_non_stable = models.BooleanField(default=True)
     notifications_show_on_external = models.BooleanField(
-        default=True,
+        default=False,
         verbose_name=_("Show a notification on builds from pull requests"),
         help_text=_(
             "Display a notification on the rendered documentation of pull "

readthedocs/proxito/tests/responses/v1.json

@@ -140,7 +140,7 @@
     },
     "notifications": {
       "enabled": true,
-      "show_on_external": true,
+      "show_on_external": false,
       "show_on_latest": true,
       "show_on_non_stable": true
     },

readthedocs/templates/projects/search_settings_form.html

@@ -0,0 +1,3 @@
+{% extends "projects/project_edit_base.html" %}
+
+{# This is just a placeholder to satisfy tests. This template is only implemented in ext-theme #}