diff --git a/docs/IMPLEMENTATION_PLAN.md b/docs/IMPLEMENTATION_PLAN.md
index eedb9f1..0421fd6 100644
--- a/docs/IMPLEMENTATION_PLAN.md
+++ b/docs/IMPLEMENTATION_PLAN.md
@@ -1489,3 +1489,13 @@ resolving to the 08:30 bar on 15m and the 08:00 bar on 1h, never edge-parked,
 and returning to its original x on the way back. Edge-parking still works where
 it should — a comment scrolled 400 bars out parks right and comes back on
 return to live.
+
+**The trendline Side control became inert.** Once snapping always lands on a
+bar extreme, the side is inferred from *which* extreme — a high is resistance, a
+low is support — so the dropdown could no longer affect anything. It now appears
+only when "Snap to highs/lows" is off, which is the one case where there is no
+extreme to infer from; otherwise the row reads "Side auto". Verified both ways:
+snap on shows the note and no dropdown, snap off shows the dropdown.
+
+`created_at` (epoch seconds) is already stored on every drawing and returned by
+`GET /api/drawings`, so filtering by age needs UI only, not a migration.
diff --git a/static/index.html b/static/index.html
index 5e1d834..eda8d94 100644
--- a/static/index.html
+++ b/static/index.html
@@ -65,7 +65,10 @@
               <label>Width<select v-model.number="drawWidth" aria-label="Trendline width"><option v-for="width in [1,2,3,4]" :value="width">{{ width }}px</option></select></label>
             </div>
             <div class="row">
-              <label>Side<select v-model="drawSide" aria-label="Trendline side"><option value="support">Support</option><option value="resistance">Resistance</option></select></label>
+              <!-- Side is inferred from the extreme you snap to, so it only has
+                   anything to say when snapping is off. -->
+              <label v-if="!snap">Side<select v-model="drawSide" aria-label="Trendline side"><option value="support">Support</option><option value="resistance">Resistance</option></select></label>
+              <span v-else class="side-auto" title="A high is resistance, a low is support">Side <b>auto</b></span>
               <label class="check"><input type="checkbox" v-model="snap">Snap to highs/lows</label>
             </div>
           </div>
diff --git a/static/style.css b/static/style.css
index cf6676d..e25902e 100644
--- a/static/style.css
+++ b/static/style.css
@@ -76,3 +76,4 @@ aside { padding:16px; }h2 { margin:0 0 12px; color:var(--muted); font-size:11px;
   border-radius:4px; background:transparent; color:var(--muted); cursor:pointer; }
 .tool-body textarea { width:100%; min-width:0; font:inherit; font-size:11px; padding:4px 6px; resize:vertical;
   border:1px solid var(--line); border-radius:5px; background:transparent; color:var(--fg); }
+.side-auto { align-self:end; padding-bottom:6px; font-size:10px; color:var(--muted); }.side-auto b { color:var(--fg); font-weight:600; }