diff --git a/docs/IMPLEMENTATION_PLAN.md b/docs/IMPLEMENTATION_PLAN.md
index 98b17a5..eedb9f1 100644
--- a/docs/IMPLEMENTATION_PLAN.md
+++ b/docs/IMPLEMENTATION_PLAN.md
@@ -1474,3 +1474,18 @@ deleting by type or by string a single button.
 One CSS trap worth recording: `.trendline-row span { grid-column:2 }` captured
 the comment row's icon span and dragged it into the text column. Scoped to
 `span:not(.drawing-icon)`.
+
+**A comment lost its place when the timeframe changed.** Placed on a 30m bar,
+then switched to 15m, it slid to the far left. `timeToCoordinate` answers only
+for times that are data points on the current series, so a 30m bucket start
+returned `null` on another timeframe — and `null` was being read as "off the
+left edge". Anchors are now resolved to the bar that *contains* them, which is
+timeframe-independent: an 09:30 note sits on the 09:30 bar at 15m and on the
+09:00 bar at 1h. `setBars` also re-renders comments, since a timeframe switch
+replaces the grid underneath every pinned one.
+
+Verified across 30m → 15m → 1h → 30m: the anchor stays 08:30 throughout,
+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.
diff --git a/static/chart.js b/static/chart.js
index 42268b2..4963b23 100644
--- a/static/chart.js
+++ b/static/chart.js
@@ -229,6 +229,8 @@ class ConfluenceChart {
       this.chart.timeScale().setVisibleRange(this.pendingView);
     }
     requestAnimationFrame(() => this.renderAnchorHandles());
+    // The bar grid just changed underneath every pinned comment.
+    this.renderComments();
   }
 
   updateBar(bar) {
@@ -285,12 +287,13 @@ class ConfluenceChart {
         node.root.classList.remove('off-left', 'off-right');
         continue;
       }
-      const x = this.chart.timeScale().timeToCoordinate(comment.anchor_t);
+      const placed = this.anchorCoordinate(comment.anchor_t);
+      const x = placed.x;
       const y = this.candles.priceToCoordinate(comment.anchor_p);
       // Scrolled past: park it on the edge it went off, pointing that way,
       // rather than letting it vanish and be hard to find again.
-      const offLeft = x === null || x < 0;
-      const offRight = x !== null && x > width;
+      const offLeft = placed.before || (x !== null && x < 0);
+      const offRight = placed.after || (x !== null && x > width);
       node.root.classList.toggle('off-left', offLeft && !offRight);
       node.root.classList.toggle('off-right', offRight);
       const clampedX = offLeft ? 4 : offRight ? width - node.root.offsetWidth - 4 : x;
@@ -305,6 +308,36 @@ class ConfluenceChart {
     }
   }
 
+  /**
+   * Where an anchor time sits on the current timeframe.
+   *
+   * timeToCoordinate answers only for times that are data points on the series,
+   * so a comment placed on a 30m bar returned null the moment the chart
+   * switched to 15m or 1h — and null was being read as "off the left edge",
+   * which slid every such comment to the far left. The anchor is resolved to
+   * the bar that *contains* it instead, which is timeframe-independent: a 09:30
+   * note lands on the 09:30 bar at 15m and on the 09:00 bar at 1h.
+   */
+  anchorCoordinate(anchorT) {
+    if (!this.bars.length) return { x: null, before: false, after: false };
+    if (anchorT < this.bars[0].t) return { x: null, before: true, after: false };
+    const lastBar = this.bars[this.bars.length - 1];
+    if (anchorT > lastBar.t) {
+      // Past the newest bar is not off the chart — the right edge carries
+      // whitespace, so ask the scale directly and only park it if it answers.
+      const beyond = this.chart.timeScale().timeToCoordinate(lastBar.t);
+      return { x: beyond, before: false, after: beyond === null };
+    }
+    let lo = 0;
+    let hi = this.bars.length - 1;
+    while (lo < hi) {
+      const mid = (lo + hi + 1) >> 1;
+      if (this.bars[mid].t <= anchorT) lo = mid;
+      else hi = mid - 1;
+    }
+    return { x: this.chart.timeScale().timeToCoordinate(this.bars[lo].t), before: false, after: false };
+  }
+
   buildCommentNode(comment) {
     const root = document.createElement('div');
     root.className = 'chart-comment';