diff --git a/lib/sql_generator.js b/lib/sql_generator.js
index bae5a24..efc9b96 100644
--- a/lib/sql_generator.js
+++ b/lib/sql_generator.js
@@ -8,7 +8,7 @@
 // Tokens baked in at generation time:  column names, source schema.table
 // Tokens substituted at request time:  {{fc_table}}, {{where_clause}}, {{exclude_clause}},
 //                                      {{version_id}}, {{logid}}, {{pf_user}}, {{note}},
-//                                      {{label}}, {{bucket}},
+//                                      {{label}}, {{bucket}}, {{tag}},
 //                                      {{params}}, {{slice}}, {{date_from}}, {{date_to}},
 //                                      {{value_incr}}, {{units_incr}}, {{set_clause}}, {{scale_factor}}
 
@@ -303,9 +303,9 @@ GROUP BY
         return `
 WITH
 ilog AS (
-    INSERT INTO pf.log (version_id, pf_user, operation, slice, params, note, label, bucket)
+    INSERT INTO pf.log (version_id, pf_user, operation, slice, params, note, label, bucket, tag)
     VALUES ({{version_id}}, '{{pf_user}}', 'baseline', NULL, '{{params}}'::jsonb, '{{note}}',
-            NULLIF('{{label}}', ''), NULLIF('{{bucket}}', ''))
+            NULLIF('{{label}}', ''), NULLIF('{{bucket}}', ''), NULLIF('{{tag}}', ''))
     RETURNING id
 )
 ,ins AS (
@@ -324,9 +324,9 @@ SELECT count(*) AS rows_affected FROM ins`.trim();
         return `
 WITH
 ilog AS (
-    INSERT INTO pf.log (version_id, pf_user, operation, slice, params, note, label, bucket)
+    INSERT INTO pf.log (version_id, pf_user, operation, slice, params, note, label, bucket, tag)
     VALUES ({{version_id}}, '{{pf_user}}', 'reference', NULL, '{{params}}'::jsonb, '{{note}}',
-            NULLIF('{{label}}', ''), NULLIF('{{bucket}}', ''))
+            NULLIF('{{label}}', ''), NULLIF('{{bucket}}', ''), NULLIF('{{tag}}', ''))
     RETURNING id
 )
 ,ins AS (
diff --git a/routes/operations.js b/routes/operations.js
index 3e6bfc7..47f11f0 100644
--- a/routes/operations.js
+++ b/routes/operations.js
@@ -409,7 +409,7 @@ module.exports = function(pool) {
 
     // load baseline rows from source table — additive, no delete
     router.post('/versions/:id/baseline', async (req, res) => {
-        const { where_clause, date_offset, note, filters, raw_where, label, bucket } = req.body;
+        const { where_clause, date_offset, note, filters, raw_where, label, bucket, tag } = req.body;
         const pf_user = sessionUser(req);
         const dateOffset    = date_offset  || '0 days';
         if (!await assertInterval(dateOffset, res)) return;
@@ -429,6 +429,7 @@ module.exports = function(pool) {
                 note:          esc(note    || ''),
                 label:         esc(label   || ''),
                 bucket:        esc(bucket  || ''),
+                tag:           esc(tag     || ''),
                 params:        esc(paramsJson),
                 filter_clause: filterClause,
                 date_offset:   esc(dateOffset)
@@ -448,7 +449,7 @@ module.exports = function(pool) {
     router.put('/versions/:id/baseline/:logid', async (req, res) => {
         const versionId = parseInt(req.params.id);
         const logid     = parseInt(req.params.logid);
-        const { where_clause, date_offset, note, filters, raw_where, label, bucket } = req.body;
+        const { where_clause, date_offset, note, filters, raw_where, label, bucket, tag } = req.body;
         const pf_user = sessionUser(req);
         const dateOffset   = date_offset  || '0 days';
         if (!await assertInterval(dateOffset, res)) return;
@@ -487,13 +488,21 @@ module.exports = function(pool) {
                 date_offset:  dateOffset,
                 ...(raw_where ? { raw_where } : (filters ? { filters } : {}))
             });
+            // This route deletes the log row and inserts a fresh one, so every
+            // annotation on it has to be handed back or it is lost. `??`, not `||`:
+            // an empty string is the form clearing a field on purpose, undefined is
+            // the form not carrying it at all -- the segment form has no tag input,
+            // so tag is always the latter and must survive an edit made for any
+            // other reason.
+            const keep = (sent, prior) => esc(sent ?? prior ?? '');
             const sql = applyTokens(ctx.sql, {
                 fc_table:      ctx.table,
                 version_id:    ctx.version.id,
                 pf_user:       esc(pf_user || ''),
                 note:          esc(note    || ''),
-                label:         esc(label   || ''),
-                bucket:        esc(bucket  || ''),
+                label:         keep(label,  oldLog.label),
+                bucket:        keep(bucket, oldLog.bucket),
+                tag:           keep(tag,    oldLog.tag),
                 params:        esc(paramsJson),
                 filter_clause: filterClause,
                 date_offset:   esc(dateOffset)
@@ -558,7 +567,7 @@ module.exports = function(pool) {
 
     // load reference rows from source table (additive — does not clear prior reference rows)
     router.post('/versions/:id/reference', async (req, res) => {
-        const { where_clause, date_offset, note, filters, raw_where, label, bucket } = req.body;
+        const { where_clause, date_offset, note, filters, raw_where, label, bucket, tag } = req.body;
         const pf_user = sessionUser(req);
         const dateOffset   = date_offset || '0 days';
         const filterClause = (raw_where || where_clause || '').trim() || 'TRUE';
@@ -577,6 +586,7 @@ module.exports = function(pool) {
                 note:          esc(note    || ''),
                 label:         esc(label   || ''),
                 bucket:        esc(bucket  || ''),
+                tag:           esc(tag     || ''),
                 params:        esc(paramsJson),
                 filter_clause: filterClause,
                 date_offset:   esc(dateOffset)