diff --git a/addons/mail/static/src/views/form/form_compiler.js b/addons/mail/static/src/views/form/form_compiler.js
index d6503c8741d..7e750ab1a1f 100644
--- a/addons/mail/static/src/views/form/form_compiler.js
+++ b/addons/mail/static/src/views/form/form_compiler.js
@@ -82,13 +82,19 @@ export class MailFormCompiler extends ViewCompiler {
         if (chatterContainerHookXml) {
             setAttributes(chatterContainerHookXml, {
                 "t-if": `!hasAttachmentViewer() and uiService.size >= ${SIZES.XXL}`,
-                "t-attf-class": `{{ uiService.size >= ${SIZES.XXL} ? "o-aside" : "" }}`,
+                "t-attf-class": "o-aside",
+            });
+            const chatterContainerXml = chatterContainerHookXml.querySelector('ChatterContainer');
+            setAttributes(chatterContainerXml, {
+                "hasExternalBorder": "false",
+                "hasMessageListScrollAdjust": "true",
+                "isInFormSheetBg": "false",
             });
         }
         const attachmentViewHookXml = res.querySelector(".o_attachment_preview");
         if (attachmentViewHookXml) {
             setAttributes(attachmentViewHookXml, {
-                "t-if": `hasAttachmentViewer() and uiService.size >= ${SIZES.XXL}`,
+                "t-if": `hasAttachmentViewer()`,
             });
         }
         return res;
@@ -152,11 +158,12 @@ patch(FormCompiler.prototype, 'mail', {
             return res; // no chatter, keep the result as it is
         }
         const chatterContainerXml = chatterContainerHookXml.querySelector('ChatterContainer');
+        setAttributes(chatterContainerXml, {
+            "hasExternalBorder": "true",
+            "hasMessageListScrollAdjust": "false",
+            "isInFormSheetBg": "false",
+        });
         if (chatterContainerHookXml.parentNode.classList.contains('o_form_sheet')) {
-            setAttributes(chatterContainerXml, {
-                "hasExternalBorder": 'true',
-                "hasMessageListScrollAdjust": 'false',
-            });
             return res; // if chatter is inside sheet, keep it there
         }
         const formSheetBgXml = res.querySelector('.o_form_sheet_bg');
@@ -164,33 +171,24 @@ patch(FormCompiler.prototype, 'mail', {
         if (!parentXml) {
             return res; // miss-config: a sheet-bg is required for the rest
         }
-        if (params.hasAttachmentViewer) {
+        if (params.hasAttachmentViewerInArch) {
             // in sheet bg (attachment viewer present)
-            const sheetBgChatterContainerHookXml = chatterContainerHookXml;
+            const sheetBgChatterContainerHookXml = chatterContainerHookXml.cloneNode(true);
             sheetBgChatterContainerHookXml.classList.add('o-isInFormSheetBg');
             setAttributes(sheetBgChatterContainerHookXml, {
-                't-if': `uiService.size < ${SIZES.XXL} or hasAttachmentViewer()`,
+                't-if': `this.props.hasAttachmentViewer`,
             });
             append(formSheetBgXml, sheetBgChatterContainerHookXml);
             const sheetBgChatterContainerXml = sheetBgChatterContainerHookXml.querySelector('ChatterContainer');
             setAttributes(sheetBgChatterContainerXml, {
                 "isInFormSheetBg": "true",
-                "hasExternalBorder": "true",
-                "hasMessageListScrollAdjust": "false",
             });
-        } else {
-            // after sheet bg (standard position, either aside or below)
-            setAttributes(chatterContainerXml, {
-                "isInFormSheetBg": "false",
-                "hasExternalBorder": `uiService.size < ${SIZES.XXL}`,
-                "hasMessageListScrollAdjust": `uiService.size >= ${SIZES.XXL}`,
-            });
-            setAttributes(chatterContainerHookXml, {
-                't-if': `uiService.size < ${SIZES.XXL}`,
-                't-attf-class': `{{ uiService.size >= ${SIZES.XXL} ? "o-aside" : "" }}`,
-            });
-            append(parentXml, chatterContainerHookXml);
         }
+        // after sheet bg (standard position, below form)
+        setAttributes(chatterContainerHookXml, {
+            't-if': `!this.props.hasAttachmentViewer and uiService.size < ${SIZES.XXL}`,
+        });
+        append(parentXml, chatterContainerHookXml);
         return res;
     },
 });
diff --git a/addons/mail/static/src/views/form/form_controller.js b/addons/mail/static/src/views/form/form_controller.js
index 0920be0f0af..69525a5d54c 100644
--- a/addons/mail/static/src/views/form/form_controller.js
+++ b/addons/mail/static/src/views/form/form_controller.js
@@ -6,6 +6,7 @@ import { WebClientViewAttachmentViewContainer } from "@mail/components/web_clien
 
 import { browser } from "@web/core/browser/browser";
 import { useService } from "@web/core/utils/hooks";
+import { SIZES } from "@web/core/ui/ui_service";
 import { patch } from "@web/core/utils/patch";
 import { useDebounced } from "@web/core/utils/timing";
 import { FormController } from "@web/views/form/form_controller";
@@ -59,7 +60,12 @@ patch(FormController.prototype, "mail", {
      * @returns {boolean}
      */
     hasAttachmentViewer() {
-        if (!this.getMessaging() || !this.model.root.resId) {
+        if (
+            this.uiService.size < SIZES.XXL ||
+            !this.hasAttachmentViewerInArch ||
+            !this.getMessaging() ||
+            !this.model.root.resId
+        ) {
             return false;
         }
         const thread = this.getMessaging().models['Thread'].insert({
diff --git a/addons/mail/static/src/views/form/form_controller.xml b/addons/mail/static/src/views/form/form_controller.xml
index b15f4d7e4fd..2e30944ce92 100644
--- a/addons/mail/static/src/views/form/form_controller.xml
+++ b/addons/mail/static/src/views/form/form_controller.xml
@@ -8,7 +8,8 @@
             </t>
         </xpath>
         <xpath expr="//Layout/t[@t-component='props.Renderer']" position="attributes">
-            <attribute name="hasAttachmentViewer">hasAttachmentViewerInArch</attribute>
+            <attribute name="hasAttachmentViewerInArch">hasAttachmentViewerInArch</attribute>
+            <attribute name="hasAttachmentViewer">hasAttachmentViewer()</attribute>
         </xpath>
     </t>
 
diff --git a/addons/mail/static/src/views/form/form_renderer.js b/addons/mail/static/src/views/form/form_renderer.js
index 82d84e74721..ef8c51f76fa 100644
--- a/addons/mail/static/src/views/form/form_renderer.js
+++ b/addons/mail/static/src/views/form/form_renderer.js
@@ -1,55 +1,19 @@
 /** @odoo-module */
 
-import { useModels } from '@mail/component_hooks/use_models';
 import { ChatterContainer } from "@mail/components/chatter_container/chatter_container";
-import { WebClientViewAttachmentViewContainer } from '@mail/components/web_client_view_attachment_view_container/web_client_view_attachment_view_container';
 
 import { patch } from "@web/core/utils/patch";
 import { FormRenderer } from "@web/views/form/form_renderer";
 
 patch(FormRenderer.prototype, 'mail', {
-    setup() {
-        this._super();
-        if (this.env.services.messaging) {
-            useModels();
-        }
-    },
-
     get compileParams() {
         return {
             ...this._super(),
-            hasAttachmentViewer: this.props.hasAttachmentViewer,
+            hasAttachmentViewerInArch: this.props.hasAttachmentViewerInArch,
         };
     },
-
-    //--------------------------------------------------------------------------
-    // Mail Methods
-    //--------------------------------------------------------------------------
-
-    /**
-     * @returns {Messaging|undefined}
-     */
-    getMessaging() {
-        return this.env.services.messaging && this.env.services.messaging.modelManager.messaging;
-    },
-    /**
-     * @returns {boolean}
-     */
-    hasAttachmentViewer() {
-        if (!this.getMessaging() || !this.props.record.resId) {
-            return false;
-        }
-        const thread = this.getMessaging().models['Thread'].insert({
-            id: this.props.record.resId,
-            model: this.props.record.resModel,
-        });
-        return (
-            thread.attachmentsInWebClientView.length > 0
-        );
-    },
 });
 
 Object.assign(FormRenderer.components, {
     ChatterContainer,
-    WebClientViewAttachmentViewContainer,
 });
diff --git a/addons/mail/static/src/widgets/form_renderer/form_renderer.scss b/addons/mail/static/src/widgets/form_renderer/form_renderer.scss
index aef5bcd2c61..e6ce0ae41a2 100644
--- a/addons/mail/static/src/widgets/form_renderer/form_renderer.scss
+++ b/addons/mail/static/src/widgets/form_renderer/form_renderer.scss
@@ -17,7 +17,8 @@
     &.o-isInFormSheetBg {
         max-width: none;
         background-color: $white;
-        @include o-form-sheet-negative-margin;
+        margin-left: -$o-horizontal-padding;
+        margin-right: -$o-horizontal-padding;
         width: auto;
         border-top: 1px solid $border-color;
     }