diff --git a/sfm/event_browser.html b/sfm/event_browser.html
index 0dce1b0..c3b7516 100644
--- a/sfm/event_browser.html
+++ b/sfm/event_browser.html
@@ -522,8 +522,13 @@ function renderWaveform(data) {
   charts = {};
 
   const channels = data.channels || {};
-  const timeAxis = data.time_axis || null;  // ms relative to trigger
-  const triggerMs = data.trigger_ms ?? 0;
+  // time_axis is METADATA from sfm.plot.v1 — sample_rate, pretrig_samples,
+  // t0_ms (first-sample time relative to trigger; negative when pretrig
+  // exists), dt_ms.  Trigger is at t=0 by convention.
+  const ta    = data.time_axis || {};
+  const sr    = ta.sample_rate || 1024;
+  const dtMs  = ta.dt_ms || (1000.0 / sr);
+  const t0Ms  = ta.t0_ms != null ? ta.t0_ms : 0;
   const isPrintMode = document.body.classList.contains('print-view');
 
   // Which channels actually have data → determines which one renders the
@@ -578,14 +583,8 @@ function renderWaveform(data) {
     wrap.appendChild(canvasWrap);
     chartsDiv.appendChild(wrap);
 
-    // Build time labels — use server-provided time_axis if present, else derive from sample_rate
-    let times;
-    if (timeAxis && timeAxis.length === values.length) {
-      times = timeAxis;
-    } else {
-      const sr = data.sample_rate || 1024;
-      times = values.map((_, i) => (i / sr * 1000 - triggerMs));
-    }
+    // Per-sample time in ms relative to trigger.  Negative for pre-trigger samples.
+    const times = values.map((_, i) => t0Ms + i * dtMs);
 
     // Downsample for rendering
     const MAX_POINTS = 4000;
diff --git a/sfm/sfm_webapp.html b/sfm/sfm_webapp.html
index 6c68b38..df23b3a 100644
--- a/sfm/sfm_webapp.html
+++ b/sfm/sfm_webapp.html
@@ -2572,8 +2572,14 @@ function _renderScWaveform(data) {
   _destroyScCharts();
 
   const channels = data.channels || {};
-  const timeAxis = data.time_axis || null;
-  const triggerMs = data.trigger_ms ?? 0;
+  // time_axis is METADATA, not an array — it carries sample_rate,
+  // pretrig_samples, t0_ms (first-sample time relative to trigger,
+  // negative when pretrig samples exist), and dt_ms.  Trigger is at
+  // t=0 by convention.
+  const ta       = data.time_axis || {};
+  const sr       = ta.sample_rate || 1024;
+  const dtMs     = ta.dt_ms || (1000.0 / sr);
+  const t0Ms     = ta.t0_ms != null ? ta.t0_ms : 0;
 
   // Which channels have data — determines which one renders the shared bottom axis.
   const withData = _SC_CHANNEL_ORDER.filter(ch =>
@@ -2612,14 +2618,8 @@ function _renderScWaveform(data) {
     wrap.appendChild(canvasWrap);
     chartsDiv.appendChild(wrap);
 
-    // Build time axis.  Prefer server-provided time_axis; else derive from sample_rate.
-    let times;
-    if (timeAxis && timeAxis.length === values.length) {
-      times = timeAxis;
-    } else {
-      const sr = data.sample_rate || 1024;
-      times = values.map((_, i) => (i / sr * 1000 - triggerMs));
-    }
+    // Per-sample time in ms relative to trigger.  Negative for pre-trigger samples.
+    const times = values.map((_, i) => t0Ms + i * dtMs);
 
     // Downsample for rendering when very long.
     const MAX = 3000;