diff --git a/src/central/adapters/tomtom_incidents.py b/src/central/adapters/tomtom_incidents.py
index 8b9851f..8868fa1 100644
--- a/src/central/adapters/tomtom_incidents.py
+++ b/src/central/adapters/tomtom_incidents.py
@@ -333,6 +333,8 @@ class TomTomIncidentsAdapter(SourceAdapter):
         return {
             "calls_per_month": calls_per_month,
             "cap": cap,
+            "seconds_per_month": _SECONDS_PER_MONTH,
+            "default_cadence_s": cls.default_cadence_s,
             "percent": percent,
             "warn": percent >= 80.0,
             "blocked": percent >= 100.0,
diff --git a/src/central/gui/templates/_partials/model_list.html b/src/central/gui/templates/_partials/model_list.html
index ac882fb..077cd04 100644
--- a/src/central/gui/templates/_partials/model_list.html
+++ b/src/central/gui/templates/_partials/model_list.html
@@ -66,10 +66,13 @@
 </div>
 
 {% if quota %}
-<div class="quota-panel flash {% if quota.blocked %}flash-error{% elif quota.warn %}flash-warn{% endif %}">
-    <strong>API quota:</strong> {{ quota.detail }}
-    {% if quota.blocked %}<br>⛔ Over free-tier cap — reduce calls before saving.
-    {% elif quota.warn %}<br>⚠️ Approaching free-tier cap.{% endif %}
+<div class="quota-panel flash {% if quota.blocked %}flash-error{% elif quota.warn %}flash-warn{% endif %}"
+     data-field="{{ field.name }}"
+     data-quota-cap="{{ quota.cap }}"
+     data-quota-spm="{{ quota.seconds_per_month }}"
+     data-quota-default="{{ quota.default_cadence_s }}">
+    <strong>API quota:</strong> <span class="quota-detail">{{ quota.detail }}</span>
+    <span class="quota-msg">{% if quota.blocked %}<br>⛔ Over free-tier cap — reduce calls before saving.{% elif quota.warn %}<br>⚠️ Approaching free-tier cap.{% endif %}</span>
 </div>
 {% endif %}
 
@@ -103,3 +106,64 @@
     });
 })();
 </script>
+
+<script>
+// v0.9.15: live client-side mirror of TomTomIncidentsAdapter.quota_estimate --
+// recompute the est. monthly call count as the operator edits a cadence input
+// or adds/removes a bbox row, without waiting for Save. Vanilla, self-contained,
+// and a no-op when no quota panel is present (non-TomTom model_lists).
+(function() {
+    function init() {
+        var panel = document.querySelector('.quota-panel[data-field]');
+        if (!panel) return;
+        var container = document.querySelector(
+            '.model-list[data-field="' + panel.dataset.field + '"]');
+        if (!container) return;
+        var body = container.querySelector('.model-list-body');
+        if (!body) return;
+        var CAP = parseFloat(panel.dataset.quotaCap);
+        var SPM = parseFloat(panel.dataset.quotaSpm);
+        var DEF = parseFloat(panel.dataset.quotaDefault);
+        var detailEl = panel.querySelector('.quota-detail');
+        var msgEl = panel.querySelector('.quota-msg');
+
+        // Server uses the adapter-level cadence as a floor:
+        // effective = max(adapter_cadence, bbox_cadence || default).
+        function adapterCadence() {
+            var el = document.getElementById('cadence_s');
+            var v = el ? parseFloat(el.value) : NaN;
+            return isNaN(v) ? 0 : v;
+        }
+        function recompute() {
+            var rows = body.querySelectorAll('.model-list-row');
+            var floor = adapterCadence(), calls = 0;
+            rows.forEach(function(row) {
+                var el = row.querySelector('[data-sub="cadence_s"]');
+                var bc = el ? parseFloat(el.value) : NaN;
+                var eff = Math.max(floor, isNaN(bc) ? DEF : bc);
+                if (eff > 0) calls += SPM / eff;
+            });
+            var cpm = Math.round(calls);
+            var pct = CAP ? (cpm / CAP * 100) : 0;
+            var warn = pct >= 80, blocked = pct >= 100;
+            detailEl.textContent = cpm.toLocaleString() + ' est. calls/month across '
+                + rows.length + ' bbox(es) vs ' + CAP.toLocaleString()
+                + '/month free tier (' + Math.round(pct) + '%)';
+            msgEl.innerHTML = blocked
+                ? '<br>⛔ Over free-tier cap — reduce calls before saving.'
+                : (warn ? '<br>⚠️ Approaching free-tier cap.' : '');
+            panel.classList.toggle('flash-error', blocked);
+            panel.classList.toggle('flash-warn', warn && !blocked);
+        }
+        body.addEventListener('input', recompute);
+        var core = document.getElementById('cadence_s');
+        if (core) core.addEventListener('input', recompute);
+        new MutationObserver(recompute).observe(body, { childList: true });
+    }
+    if (document.readyState === 'loading') {
+        document.addEventListener('DOMContentLoaded', init);
+    } else {
+        init();
+    }
+})();
+</script>
diff --git a/tests/test_gui_adapter_edit.py b/tests/test_gui_adapter_edit.py
index d7cb04f..f196cbf 100644
--- a/tests/test_gui_adapter_edit.py
+++ b/tests/test_gui_adapter_edit.py
@@ -56,6 +56,27 @@ class TestModelListRender:
         assert "model-list" in out and 'name="bboxes-0-name"' in out
         assert "free tier" in out  # quota panel rendered
 
+    def test_quota_panel_exposes_client_recompute_constants(self):
+        # v0.9.15: data-quota-* attrs let the client JS mirror the server
+        # formula with no hardcoded magic numbers.
+        fields = describe_fields(TomTomIncidentsAdapter.settings_schema, _SETTINGS)
+        quota = TomTomIncidentsAdapter.quota_estimate(TomTomIncidentsSettings(**_SETTINGS), 1800)
+        out = _render("adapters_edit.html", _ctx(_SETTINGS, fields, quota))
+        assert 'data-quota-cap="2500"' in out
+        assert 'data-quota-spm="2592000"' in out
+        assert 'data-quota-default="1800"' in out
+
+    def test_quota_panel_wraps_detail_and_msg_for_live_update(self):
+        # v0.9.15: detail/msg split into spans so the IIFE can rewrite the text
+        # and warn/block state live. JS exec needs a browser, so this is
+        # structural only -- live behaviour (cadence edit + Add/Delete row)
+        # was eyeballed manually against /adapters/tomtom_incidents.
+        fields = describe_fields(TomTomIncidentsAdapter.settings_schema, _SETTINGS)
+        quota = TomTomIncidentsAdapter.quota_estimate(TomTomIncidentsSettings(**_SETTINGS), 1800)
+        out = _render("adapters_edit.html", _ctx(_SETTINGS, fields, quota))
+        assert '<span class="quota-detail">' in out
+        assert '<span class="quota-msg">' in out
+
     def test_nws_region_intact_no_model_list(self):
         from central.adapters.nws import NWSSettings
         s = {"contact_email": "a@b.com",