diff --git a/backend/hyperglosae/src/updates/editFlag.js b/backend/hyperglosae/src/updates/editFlag.js
new file mode 100644
index 00000000..3ae8e855
--- /dev/null
+++ b/backend/hyperglosae/src/updates/editFlag.js
@@ -0,0 +1,10 @@
+function(doc, req) {
+  if (!doc) return [null, { json: { error: 'not_found' } }];
+  const body = JSON.parse(req.body);
+  if (body.beingEditedBy) {
+    doc.beingEditedBy = body.beingEditedBy;
+  } else {
+    delete doc.beingEditedBy;
+  }
+  return [doc, { json: { status: 'ok' } }];
+}
\ No newline at end of file
diff --git a/backend/hyperglosae/src/views/content/map.js b/backend/hyperglosae/src/views/content/map.js
index fcec13f7..1fdb95a6 100644
--- a/backend/hyperglosae/src/views/content/map.js
+++ b/backend/hyperglosae/src/views/content/map.js
@@ -1,9 +1,9 @@
 function (doc) {
   const { getRelatedDocuments, emitPassages, emitIncludedDocuments } = require('views/lib/links');
 
-  let { _id, text = '', isPartOf = _id, links = [] } = doc;
+  let { _id, text = '', isPartOf = _id, links = [], beingEditedBy } = doc;
   let related = getRelatedDocuments({isPartOf, links});
 
-  emitPassages({text, isPartOf, related});
+  emitPassages({text, isPartOf, related, beingEditedBy});
   emitIncludedDocuments({isPartOf, links});
-}
+}
\ No newline at end of file
diff --git a/backend/hyperglosae/src/views/lib/links.js b/backend/hyperglosae/src/views/lib/links.js
index 3e01b765..dd38560c 100644
--- a/backend/hyperglosae/src/views/lib/links.js
+++ b/backend/hyperglosae/src/views/lib/links.js
@@ -31,11 +31,17 @@ const parseText = (text) => {
   }));
 }
 
-exports.emitPassages = ({text, isPartOf, related}) => {
+exports.emitPassages = ({text, isPartOf, related, beingEditedBy}) => {
   parseText(text).forEach(({rubric, passage, parsed_rubric}) =>
     related.forEach((x) => {
-      emit([x, ...parsed_rubric], { text: passage, isPartOf, rubric, _id: null });
- 	  })
+      emit([x, ...parsed_rubric], {
+        text: passage,
+        isPartOf,
+        rubric,
+        _id: null,
+        ...(beingEditedBy && {beingEditedBy})
+      });
+    })
   );
 }
 
diff --git a/frontend/scenarios/co-edit.feature b/frontend/scenarios/co-edit.feature
index bcdcb8a9..72c40da3 100644
--- a/frontend/scenarios/co-edit.feature
+++ b/frontend/scenarios/co-edit.feature
@@ -22,3 +22,13 @@ Scénario: qui modifie les métadonnées
     """
   Alors les métadonnées de la glose en mode édition contiennent "dc_creator: Bill"
 
+Scénario: qui est en train de modifier le contenu
+  Quand "Bill" est en train d’éditer le passage “1”
+  Alors la glose en mode édition indique que "Bill" modifie le passage “1”
+
+Scénario: termine de modifier le contenu
+  Soit "Bill" est en train d’éditer le passage “1”
+  Et la glose en mode édition indique que "Bill" modifie le passage “1”
+  Quand "Bill" quitte le mode édition
+  Alors la glose n'indique pas de modification en cours sur le passage "1"
+  
diff --git a/frontend/src/components/EditableText.jsx b/frontend/src/components/EditableText.jsx
index 19b3452a..6d3e4fac 100644
--- a/frontend/src/components/EditableText.jsx
+++ b/frontend/src/components/EditableText.jsx
@@ -6,13 +6,15 @@ import DiscreeteDropdown from './DiscreeteDropdown';
 import PictureUploadAction from '../menu-items/PictureUploadAction';
 import {v4 as uuid} from 'uuid';
 import { OverlayTrigger, Tooltip } from 'react-bootstrap';
+import { PencilSquare } from 'react-bootstrap-icons';
 
-function EditableText({id, text, rubric, isPartOf, links, fragment, setFragment, setHighlightedText, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate}) {
+function EditableText({id, text, rubric, isPartOf, links, beingEditedBy, fragment, setFragment, setHighlightedText, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate, user}) {
   const [beingEdited, setBeingEdited] = useState(false);
   const [editedDocument, setEditedDocument] = useState();
   const [editedText, setEditedText] = useState();
   const [hasBeenChanged, setHasBeenChanged] = useState(false);
   const PASSAGE = new RegExp(`\\{${rubric}} ?([^{]*)`);
+  const isEditedByOther = beingEditedBy && beingEditedBy !== user;
 
   let parsePassage = (rawText) => (rubric)
     ? rawText.match(PASSAGE)[1]
@@ -33,6 +35,19 @@ function EditableText({id, text, rubric, isPartOf, links, fragment, setFragment,
       return x;
     }), [backend, id, isPartOf, links, rubric]);
 
+  // Marque "en édition par <user>" quand on entre, démarque quand on sort
+  useEffect(() => {
+    if (!user || !id) return;
+    if (beingEdited) {
+      backend.markEditing(id, user).catch(console.error);
+    }
+    return () => {
+      if (beingEdited) {
+        backend.markEditing(id, null).catch(console.error);
+      }
+    };
+  }, [beingEdited, id, user, backend]);
+
   useEffect(() => {
     if (fragment) {
       updateEditedDocument()
@@ -57,6 +72,7 @@ function EditableText({id, text, rubric, isPartOf, links, fragment, setFragment,
   }, [rawEditMode, updateEditedDocument]);
 
   let handleClick = () => {
+    if (isEditedByOther) return;
     setBeingEdited(true);
     updateEditedDocument()
       .then((x) => {
@@ -102,25 +118,41 @@ function EditableText({id, text, rubric, isPartOf, links, fragment, setFragment,
       .catch(console.error);
   };
 
+  // Vue lecture
   if (!beingEdited) return (
-    <div className="editable content position-relative">
+    <div className="editable content position-relative" id={id} >
+      {isEditedByOther && (
+        <OverlayTrigger
+          placement="top"
+          overlay={<Tooltip id={`being-edited-${id}`}>{beingEditedBy} is currently editing passage {rubric || '0'}</Tooltip>}
+        >
+          <PencilSquare className="being-edited-icon" data-testid="being-edited-icon" />
+        </OverlayTrigger>
+      )}
       <OverlayTrigger
         placement="top"
-        overlay={<Tooltip id={`tooltip-${id}`}>Edit content...</Tooltip>}
+        overlay={
+          <Tooltip id={`tooltip-${id}`}>
+            {isEditedByOther ? `Locked by ${beingEditedBy}` : 'Edit content...'}
+          </Tooltip>
+        }
       >
         <div className="formatted-text" onClick={handleClick}>
           <FormattedText {...{setHighlightedText, setSelectedText}}>
-            {text || '&nbsp;'}
+            {text || '\u00A0'}
           </FormattedText>
         </div>
       </OverlayTrigger>
       <DiscreeteDropdown>
-        <PictureUploadAction {... {id, backend, handleImageUrl}}/>
+        <PictureUploadAction {...{id, backend, handleImageUrl}}/>
       </DiscreeteDropdown>
     </div>
   );
+
+  // Vue édition
   return (
-    <form>
+    <form className="position-relative">
+      <PencilSquare className="being-edited-icon self" data-testid="being-edited-self" />
       <textarea className="form-control" type="text" rows="5" autoFocus
         value={editedText} onChange={handleChange} onBlur={handleBlur}
       />
diff --git a/frontend/src/components/OpenedDocuments.jsx b/frontend/src/components/OpenedDocuments.jsx
index c51f6de2..afc10f2e 100644
--- a/frontend/src/components/OpenedDocuments.jsx
+++ b/frontend/src/components/OpenedDocuments.jsx
@@ -34,7 +34,7 @@ function OpenedDocuments({id, margin, metadata, parallelDocuments, rawEditMode,
       </Row>
       {parallelDocuments.passages.map(({rubric, source, scholia}, i) =>
         <Passage key={rubric || i}
-          {...{source, rubric, scholia, margin, sourceId: id, isComposite, rawEditMode, setRawEditMode, backend, setLastUpdate}}
+          {...{source, rubric, scholia, margin, sourceId: id, isComposite, rawEditMode, setRawEditMode, backend, setLastUpdate, user}}
         />)
       }
       <Row>
diff --git a/frontend/src/components/Passage.jsx b/frontend/src/components/Passage.jsx
index 7001609e..7698a1b9 100644
--- a/frontend/src/components/Passage.jsx
+++ b/frontend/src/components/Passage.jsx
@@ -10,7 +10,7 @@ import EditableText from '../components/EditableText';
 import DiscreeteDropdown from './DiscreeteDropdown';
 import CommentFragmentAction from '../menu-items/CommentFragmentAction';
 
-function Passage({source, rubric, scholia, margin, sourceId, isComposite, rawEditMode, setRawEditMode, backend, setLastUpdate}) {
+function Passage({source, rubric, scholia, margin, sourceId, isComposite, rawEditMode, setRawEditMode, backend, setLastUpdate, user}) {
   const [selectedText, setSelectedText] = useState();
   const [highlightedText, setHighlightedText] = useState('');
   const [fragment, setFragment] = useState();
@@ -39,7 +39,7 @@ function Passage({source, rubric, scholia, margin, sourceId, isComposite, rawEdi
           </Container>
         }
       </Col>
-      <PassageMargin active={!!margin} {...{scholia, rubric, setHighlightedText, fragment, setFragment, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate}} />
+      <PassageMargin active={!!margin} {...{scholia, rubric, setHighlightedText, fragment, setFragment, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate, user}} />
     </Row>
   );
 }
@@ -87,12 +87,12 @@ function Rubric({id}) {
   );
 }
 
-function PassageMargin({active, scholia, setHighlightedText, fragment, setFragment, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate}) {
+function PassageMargin({active, scholia, setHighlightedText, fragment, setFragment, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate, user}) {
   if (!active) return;
   return (
     <Col xs={5} className="scholium">
       {scholia.map((scholium, i) =>
-        <EditableText key={i} {...scholium} {...{setHighlightedText, fragment, setFragment, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate}} />
+        <EditableText key={i} {...scholium} {...{setHighlightedText, fragment, setFragment, setSelectedText, rawEditMode, setRawEditMode, backend, setLastUpdate, user}} />
       )}
     </Col>
   );
diff --git a/frontend/src/hyperglosae.js b/frontend/src/hyperglosae.js
index 35d38743..f3c28c63 100644
--- a/frontend/src/hyperglosae.js
+++ b/frontend/src/hyperglosae.js
@@ -63,7 +63,6 @@ function Hyperglosae(logger) {
         fetch(`${service}/${id}/${attachment.name}`, {
           method: 'PUT',
           headers: {
-            // ETag is the header that carries the current rev.
             'If-Match': x.headers.get('ETag'),
             'Content-Type': attachment.type
           },
@@ -119,7 +118,17 @@ function Hyperglosae(logger) {
     this.getView({view: 'all_documents', id: user || 'PUBLIC', options: ['include_docs']})
       .then((rows) => rows.map(x => x.doc));
 
+  this.markEditing = (id, beingEditedBy) =>
+    fetch(`${service}/_design/app/_update/editFlag/${id}`, {
+      method: 'PUT',
+      body: JSON.stringify({ beingEditedBy })
+    }).then(x => x.json());
+
+  this.subscribeToChanges = (since = 'now') =>
+    fetch(`${service}/_changes?feed=longpoll&since=${since}&heartbeat=25000`)
+      .then(x => x.json());
+
   return this;
 }
 
-export default Hyperglosae;
+export default Hyperglosae;
\ No newline at end of file
diff --git a/frontend/src/parallelDocuments.js b/frontend/src/parallelDocuments.js
index 10d47e88..34daceeb 100644
--- a/frontend/src/parallelDocuments.js
+++ b/frontend/src/parallelDocuments.js
@@ -102,7 +102,12 @@ function ParallelDocuments(id, rawContent = [], margin, raw = false) {
       if (xor(!this.isFromScratch, isPartOf === id)) {
         if (!raw || !part.scholia.length || part.scholia[part.scholia.length - 1].id !== x.id) {
           let rubric = x.value.rubric;
-          part.scholia.push({id: x.id, text, isPartOf, ...(rubric !== '0' && {rubric})});
+
+          part.scholia.push({
+            id: x.id, text, isPartOf,
+            ...(rubric !== '0' && {rubric}),
+            ...(x.value.beingEditedBy && {beingEditedBy: x.value.beingEditedBy})
+          });
         }
       }
     }
diff --git a/frontend/src/routes/Lectern.jsx b/frontend/src/routes/Lectern.jsx
index 6a951062..7053848d 100644
--- a/frontend/src/routes/Lectern.jsx
+++ b/frontend/src/routes/Lectern.jsx
@@ -41,6 +41,30 @@ function Lectern({backend, user}) {
     setParallelDocuments(new ParallelDocuments(id, content, margin, rawEditMode));
   }, [id, content, margin, rawEditMode, lastUpdate]);
 
+  // Long polling sur les changements CouchDB
+  useEffect(() => {
+    let cancelled = false;
+    let since = 'now';
+    function poll() {
+      backend.subscribeToChanges(since)
+        .then(({ last_seq, results }) => {
+          if (cancelled) return;
+          since = last_seq;
+          if (results && results.length > 0) {
+            setLastUpdate(last_seq);
+          }
+          poll();
+        })
+        .catch(() => {
+          if (!cancelled) setTimeout(poll, 5000);
+        });
+    }
+    poll();
+    return () => {
+      cancelled = true;
+    };
+  }, [backend]);
+
   if (!metadata?.focusedDocument?._id && !loading) {
     return <DocumentNotFound />;
   }
@@ -85,4 +109,4 @@ function References({metadata, active, createOn, setLastUpdate, backend, user})
   );
 }
 
-export default Lectern;
+export default Lectern;
\ No newline at end of file
diff --git a/frontend/src/styles/EditableText.css b/frontend/src/styles/EditableText.css
index 5632ffd2..01f832b0 100644
--- a/frontend/src/styles/EditableText.css
+++ b/frontend/src/styles/EditableText.css
@@ -12,4 +12,15 @@
   border-color: black;
 }
 
+.being-edited-icon {
+  position: absolute;
+  top: 4px;
+  right: 4px;
+  color: #d2691e;
+  z-index: 5;
+  pointer-events: auto;
+}
 
+.being-edited-icon.self {
+  color: #2e7d32;
+}
\ No newline at end of file