diff --git a/routes/sources.js b/routes/sources.js
index 3b79ab6..cc27fa7 100644
--- a/routes/sources.js
+++ b/routes/sources.js
@@ -222,6 +222,24 @@ module.exports = function(pool) {
         }
     });
 
+    // set or clear the default Perspective layout for a source.
+    // Body: a Perspective view config (group_by, split_by, columns, plugin_config, …).
+    // Pass null or {} to clear.
+    router.put('/sources/:id/default-layout', async (req, res) => {
+        try {
+            const layout = req.body && Object.keys(req.body).length > 0 ? req.body : null;
+            const result = await pool.query(
+                `UPDATE pf.source SET default_layout = $1 WHERE id = $2 RETURNING *`,
+                [layout, req.params.id]
+            );
+            if (result.rows.length === 0) return res.status(404).json({ error: 'Source not found' });
+            res.json(result.rows[0]);
+        } catch (err) {
+            console.error(err);
+            res.status(500).json({ error: err.message });
+        }
+    });
+
     // deregister a source — does not drop existing forecast tables
     router.delete('/sources/:id', async (req, res) => {
         try {
diff --git a/setup_sql/01_schema.sql b/setup_sql/01_schema.sql
index 66f3bf5..ea9ed8c 100644
--- a/setup_sql/01_schema.sql
+++ b/setup_sql/01_schema.sql
@@ -4,16 +4,20 @@
 CREATE SCHEMA IF NOT EXISTS pf;
 
 CREATE TABLE IF NOT EXISTS pf.source (
-    id          serial PRIMARY KEY,
-    schema      text NOT NULL,
-    tname       text NOT NULL,
-    label       text,
-    status      text NOT NULL DEFAULT 'active',  -- active | archived
-    created_at  timestamptz NOT NULL DEFAULT now(),
-    created_by  text,
+    id             serial PRIMARY KEY,
+    schema         text NOT NULL,
+    tname          text NOT NULL,
+    label          text,
+    status         text NOT NULL DEFAULT 'active',  -- active | archived
+    default_layout jsonb,                            -- Perspective view config used as the per-source default
+    created_at     timestamptz NOT NULL DEFAULT now(),
+    created_by     text,
     UNIQUE (schema, tname)
 );
 
+-- backfill column for existing installs
+ALTER TABLE pf.source ADD COLUMN IF NOT EXISTS default_layout jsonb;
+
 CREATE TABLE IF NOT EXISTS pf.col_meta (
     id          serial PRIMARY KEY,
     source_id   integer NOT NULL REFERENCES pf.source(id) ON DELETE CASCADE,
diff --git a/ui/src/views/Forecast.jsx b/ui/src/views/Forecast.jsx
index 7557f59..3fffda6 100644
--- a/ui/src/views/Forecast.jsx
+++ b/ui/src/views/Forecast.jsx
@@ -29,7 +29,7 @@ function cleanLayout(cfg, validCols) {
   return c
 }
 
-export default function Forecast({ sourceId, versionId }) {
+export default function Forecast({ sources = [], sourceId, versionId, refreshSources }) {
   const { dark } = useTheme()
   const [loading,      setLoading]      = useState(false)
   const [largeDataset, setLargeDataset] = useState(false)
@@ -238,13 +238,21 @@ export default function Forecast({ sourceId, versionId }) {
         await viewer.restore(cfg)
         if (cfg.expand_depth != null) await applyDepth(cfg.expand_depth)
       } else {
-        const valueCol = meta.find(c => c.role === 'value')?.cname
-        const cfg = {
-          table: tableName,
-          settings: false,
-          group_by: ['pf_iter'],
-          columns: valueCol ? [valueCol] : [],
-          plugin_config: { edit_mode: 'SELECT_REGION' }
+        const sourceDefault = sources.find(s => String(s.id) === String(sid))?.default_layout
+        let cfg
+        if (sourceDefault && Object.keys(sourceDefault).length > 0) {
+          cfg = cleanLayout(sourceDefault, validCols)
+          cfg.table = tableName
+          cfg.plugin_config = { edit_mode: 'SELECT_REGION', ...(cfg.plugin_config || {}) }
+        } else {
+          const valueCol = meta.find(c => c.role === 'value')?.cname
+          cfg = {
+            table: tableName,
+            settings: false,
+            group_by: ['pf_iter'],
+            columns: valueCol ? [valueCol] : [],
+            plugin_config: { edit_mode: 'SELECT_REGION' }
+          }
         }
         await viewer.restore(cfg)
       }
@@ -320,6 +328,22 @@ export default function Forecast({ sourceId, versionId }) {
     flash('Saved')
   }
 
+  async function saveAsSourceDefault() {
+    const cfg = await captureConfig()
+    if (!cfg) return
+    const { table, expand_depth, ...rest } = cfg
+    try {
+      const res = await fetch(`/api/sources/${sourceId}/default-layout`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(rest)
+      })
+      if (!res.ok) { const data = await res.json(); flash(data.error || 'Failed', 'error'); return }
+      if (refreshSources) await refreshSources()
+      flash('Saved as source default')
+    } catch (err) { flash(err.message, 'error') }
+  }
+
   async function handleSaveOver() {
     const layout = layouts.find(l => l.id === activeLayoutId)
     if (!layout) return
@@ -492,6 +516,11 @@ export default function Forecast({ sourceId, versionId }) {
               <button onClick={() => setShowSaveAs(true)} className="border border-dashed border-gray-200 text-gray-400 hover:text-gray-600 rounded px-2 py-0.5">
                 Save as…
               </button>
+              <button onClick={saveAsSourceDefault} disabled={!sourceId}
+                className="border border-dashed border-gray-200 text-gray-400 hover:text-gray-600 rounded px-2 py-0.5 disabled:opacity-40"
+                title="Use this layout as the default for new versions of this source">
+                Set source default
+              </button>
               {activeLayoutId !== null && (
                 <button onClick={resetLayout} className="text-gray-300 hover:text-red-400">Reset</button>
               )}