diff --git a/src/app/api/series/[slug]/route.ts b/src/app/api/series/[slug]/route.ts
index fbcfd1d92..06537e0af 100644
--- a/src/app/api/series/[slug]/route.ts
+++ b/src/app/api/series/[slug]/route.ts
@@ -2,7 +2,13 @@ import { NextResponse } from "next/server";
 import { hasSeriesHistory, loadSeriesHistory } from "@/lib/series-history";
 import { unstable_cache } from "next/cache";
 import { getBenchmark } from "@/data/benchmarks";
-import { filterSig, loadSpecsUncached, specToBenchmark } from "@/lib/materialize/load";
+import {
+  dimensionLabels,
+  filterSig,
+  loadSpecsUncached,
+  panelMetricQuery,
+  specToBenchmark,
+} from "@/lib/materialize/load";
 import { readMaterialized } from "@/lib/materialize/store";
 import { loadSnapshotFromBlob } from "@/lib/bench-blob";
 import { buildProviderColors } from "@/lib/series-colors";
@@ -95,13 +101,17 @@ const getSeriesMapCached = unstable_cache(
         const windowSec = range === "7d" ? 7 * 86_400 : 30 * 86_400;
         const numPoints = range === "7d" ? 84 : 60;
         const labelKey = panel.label_key ?? "builder";
+        // The spec here is the raw one off disk, never through
+        // applyDimensionsToSpec, so the reader's chain/region have to be
+        // injected explicitly. Omitting them pooled every chain into one
+        // line while the head-lag view beside it moved per chain.
+        const dims = dimensionLabels({ chain, region, kind, venue, tier });
+        const scoped = panelMetricQuery(panel, dims);
         const result: Record<string, (number | null)[]> = {};
         await Promise.all(
           spec.providers.map(async (p) => {
             const sel = `${labelKey}="${escapePromLabelValue(p.slug)}"`;
-            const q = panel.metric.includes("{")
-              ? panel.metric.replace("{", `{${sel},`)
-              : `${panel.metric}{${sel}}`;
+            const q = scoped.replace("{", `{${sel},`);
             const s = await prom.series(q, windowSec, numPoints);
             if (s && s.length > 0) result[p.slug] = s;
           }),
@@ -143,9 +153,9 @@ const getSeriesMapCached = unstable_cache(
           if (!panel) return;
           const labelKey = panel.label_key ?? "builder";
           const sel = `${labelKey}="${escapePromLabelValue(p.slug)}"`;
-          q = panel.metric.includes("{")
-            ? panel.metric.replace("{", `{${sel},`)
-            : `${panel.metric}{${sel}}`;
+          // Same raw spec, same reason as the 7d/30d path above.
+          const dims = dimensionLabels({ chain, region, kind, venue, tier });
+          q = panelMetricQuery(panel, dims).replace("{", `{${sel},`);
         } else {
           q = p.queries?.series;
         }
@@ -158,7 +168,9 @@ const getSeriesMapCached = unstable_cache(
     return Object.keys(result).length > 0 ? result : null;
   },
   // v8: denser 90d/1y resolution (6h / 18h step) so young benches render at full fidelity.
-  ["series-by-range-v9"],
+  // v10: panel series carry the reader's chain/region. Entries written
+  // before this hold one cross-chain average under a per-chain key.
+  ["series-by-range-v10"],
   { revalidate: 300, tags: ["benchmarks"] },
 );
 
diff --git a/src/components/time-series-chart/index.tsx b/src/components/time-series-chart/index.tsx
index 13b3e209f..4a1321e57 100644
--- a/src/components/time-series-chart/index.tsx
+++ b/src/components/time-series-chart/index.tsx
@@ -18,6 +18,7 @@ import {
   RANGE_LABEL,
   REGION_LABEL,
   pickSeries,
+  panelSeriesCacheKey,
   mean,
   type Range,
   type LineWithColor,
@@ -186,14 +187,28 @@ export function TimeSeriesChart({
   const [lazySeries1y, setLazySeries1y] = useState<Record<string, (number | null)[]> | null>(null);
   // Declared early so effects below can guard on it without TDZ issues.
   const panelActive = !!seriesOverride;
-  // Per-panel lazy series, keyed by panel id. Cached across a panel
-  // switch so flipping back to a previously-viewed panel is instant.
+  // Per-panel lazy series, keyed by panel id AND by the filters the series
+  // was fetched under. Cached across a panel switch so flipping back to a
+  // previously-viewed panel is instant.
   // 7d/30d: fetched on panel activation. 90d/1y: fetched on-demand when
   // the user clicks those tabs (Prom-backed, not archive-backed).
+  //
+  // The filters have to be in the key. Keyed on the panel alone, the first
+  // chain a reader opened was served back on every other chain tab: the
+  // effects below DO re-run on a chain change (chainProp is in their deps)
+  // and then return early on their own cache hit, so the fetch never
+  // happened. 1H/6H/24H never showed it because those render from the
+  // embedded per-filter series, which is why the bug presented as "only 7D
+  // and 30D are wrong". Lucas reported it on bench 001, where the First to
+  // report shares are a per-chain race, so one chain's numbers appearing on
+  // four tabs named the wrong leader on three of them.
   const [lazyPanel7d, setLazyPanel7d] = useState<Record<string, Record<string, (number | null)[]>>>({});
   const [lazyPanel30d, setLazyPanel30d] = useState<Record<string, Record<string, (number | null)[]>>>({});
   const [lazyPanel90d, setLazyPanel90d] = useState<Record<string, Record<string, (number | null)[]>>>({});
   const [lazyPanel1y, setLazyPanel1y] = useState<Record<string, Record<string, (number | null)[]>>>({});
+  const panelCacheKey = activePanelId
+    ? panelSeriesCacheKey(activePanelId, chainProp, regionProp, tierProp)
+    : null;
 
   // Pre-fetch 7d AND 30d in the background as soon as the chart mounts,
   // not just when the user clicks the tab. The fetches are non-blocking
@@ -318,14 +333,14 @@ export function TimeSeriesChart({
   // case since slimBenchmarkForCache drops them). Cache-keyed per panel so
   // switching between panels re-uses previously loaded data instantly.
   useEffect(() => {
-    if (!activePanelId) return;
+    if (!activePanelId || !panelCacheKey) return;
     // Inline overrides win — skip the fetch when the parent already
     // supplied panel long-range series (e.g. an unshimmed test caller).
     if (seriesOverride7d && seriesOverride30d) return;
-    if (lazyPanel7d[activePanelId] && lazyPanel30d[activePanelId]) return;
+    if (lazyPanel7d[panelCacheKey] && lazyPanel30d[panelCacheKey]) return;
     let cancelled = false;
-    const need7d = !seriesOverride7d && !lazyPanel7d[activePanelId];
-    const need30d = !seriesOverride30d && !lazyPanel30d[activePanelId];
+    const need7d = !seriesOverride7d && !lazyPanel7d[panelCacheKey];
+    const need30d = !seriesOverride30d && !lazyPanel30d[panelCacheKey];
     const done: Record<"7d" | "30d", boolean> = {
       "7d": !need7d,
       "30d": !need30d,
@@ -349,9 +364,9 @@ export function TimeSeriesChart({
           const map: Record<string, (number | null)[]> = {};
           for (const p of data.providers) map[p.slug] = p.values;
           if (range === "7d") {
-            setLazyPanel7d((prev) => ({ ...prev, [activePanelId]: map }));
+            setLazyPanel7d((prev) => ({ ...prev, [panelCacheKey]: map }));
           } else {
-            setLazyPanel30d((prev) => ({ ...prev, [activePanelId]: map }));
+            setLazyPanel30d((prev) => ({ ...prev, [panelCacheKey]: map }));
           }
         })
         .catch(() => {
@@ -361,9 +376,9 @@ export function TimeSeriesChart({
           } else {
             done[range] = true;
             if (range === "7d") {
-              setLazyPanel7d((prev) => ({ ...prev, [activePanelId]: {} }));
+              setLazyPanel7d((prev) => ({ ...prev, [panelCacheKey]: {} }));
             } else {
-              setLazyPanel30d((prev) => ({ ...prev, [activePanelId]: {} }));
+              setLazyPanel30d((prev) => ({ ...prev, [panelCacheKey]: {} }));
             }
           }
         });
@@ -384,9 +399,9 @@ export function TimeSeriesChart({
   // Triggered the first time a panel becomes active — we prefetch both
   // ranges so the user can switch between them without extra round-trips.
   useEffect(() => {
-    if (!activePanelId) return;
-    const need90d = !lazyPanel90d[activePanelId];
-    const need1y = !lazyPanel1y[activePanelId];
+    if (!activePanelId || !panelCacheKey) return;
+    const need90d = !lazyPanel90d[panelCacheKey];
+    const need1y = !lazyPanel1y[panelCacheKey];
     if (!need90d && !need1y) return;
     let cancelled = false;
     const buildQs = (r: "90d" | "1y") => {
@@ -406,13 +421,13 @@ export function TimeSeriesChart({
           if (cancelled) return;
           const map: Record<string, (number | null)[]> = {};
           for (const p of data.providers) map[p.slug] = p.values;
-          if (r === "90d") setLazyPanel90d((prev) => ({ ...prev, [activePanelId]: map }));
-          else setLazyPanel1y((prev) => ({ ...prev, [activePanelId]: map }));
+          if (r === "90d") setLazyPanel90d((prev) => ({ ...prev, [panelCacheKey]: map }));
+          else setLazyPanel1y((prev) => ({ ...prev, [panelCacheKey]: map }));
         })
         .catch(() => {
           if (cancelled) return;
-          if (r === "90d") setLazyPanel90d((prev) => ({ ...prev, [activePanelId]: {} }));
-          else setLazyPanel1y((prev) => ({ ...prev, [activePanelId]: {} }));
+          if (r === "90d") setLazyPanel90d((prev) => ({ ...prev, [panelCacheKey]: {} }));
+          else setLazyPanel1y((prev) => ({ ...prev, [panelCacheKey]: {} }));
         });
     };
     if (need90d) fetchOne("90d");
@@ -421,10 +436,10 @@ export function TimeSeriesChart({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [activePanelId, regionProp, chainProp, tierProp, benchmark.slug]);
 
-  const panelLazy7d = activePanelId ? lazyPanel7d[activePanelId] : undefined;
-  const panelLazy30d = activePanelId ? lazyPanel30d[activePanelId] : undefined;
-  const panelLazy90d = activePanelId ? lazyPanel90d[activePanelId] : undefined;
-  const panelLazy1y = activePanelId ? lazyPanel1y[activePanelId] : undefined;
+  const panelLazy7d = panelCacheKey ? lazyPanel7d[panelCacheKey] : undefined;
+  const panelLazy30d = panelCacheKey ? lazyPanel30d[panelCacheKey] : undefined;
+  const panelLazy90d = panelCacheKey ? lazyPanel90d[panelCacheKey] : undefined;
+  const panelLazy1y = panelCacheKey ? lazyPanel1y[panelCacheKey] : undefined;
 
   // null = still loading → show optimistically; {} = confirmed empty → hide
   const seriesHasData = (m: Record<string, (number | null)[]> | null) =>
diff --git a/src/components/time-series-chart/panel-cache-key.test.ts b/src/components/time-series-chart/panel-cache-key.test.ts
new file mode 100644
index 000000000..6ff7b342c
--- /dev/null
+++ b/src/components/time-series-chart/panel-cache-key.test.ts
@@ -0,0 +1,65 @@
+import { describe, expect, test } from "bun:test";
+import { panelSeriesCacheKey } from "@/components/time-series-chart/scales";
+
+/**
+ * The chart caches a panel's lazily fetched 7d/30d/90d/1y series, and the key
+ * decides whether switching a tab refetches.
+ *
+ * Keyed on the panel id alone, it did not. The effects re-ran on a chain
+ * change, hit their own "already cached?" guard, and returned before
+ * fetching, so the first chain a reader opened stayed on screen for every
+ * other chain. On bench 001 that put one chain's First to report shares on
+ * four tabs and named the wrong leader on three of them (Base is Serialized
+ * at 74.7 %, BNB is Mobula at 64.8 %, Robinhood is Serialized at 93.3 %;
+ * only Solana was Codex). 1H/6H/24H were always right because they render
+ * from the embedded per-filter series, which is exactly why the report was
+ * "only 7D and 30D".
+ *
+ * So the property under test is simply: two different filter sets must never
+ * share a key.
+ */
+describe("panelSeriesCacheKey", () => {
+  test("a chain change produces a different key", () => {
+    expect(panelSeriesCacheKey("first_share", "base")).not.toBe(
+      panelSeriesCacheKey("first_share", "bnb"),
+    );
+  });
+
+  test("a region change produces a different key", () => {
+    expect(panelSeriesCacheKey("first_share", "base", "eu-west")).not.toBe(
+      panelSeriesCacheKey("first_share", "base", "sgp"),
+    );
+  });
+
+  test("a tier change produces a different key", () => {
+    expect(panelSeriesCacheKey("p50", "ethereum", "eu-west", "keyed")).not.toBe(
+      panelSeriesCacheKey("p50", "ethereum", "eu-west", "public"),
+    );
+  });
+
+  test("a panel change still produces a different key", () => {
+    expect(panelSeriesCacheKey("first_share", "base")).not.toBe(
+      panelSeriesCacheKey("head_lag", "base"),
+    );
+  });
+
+  test("the same filters produce the same key, so the cache still works", () => {
+    expect(panelSeriesCacheKey("first_share", "base", "eu-west", "public")).toBe(
+      panelSeriesCacheKey("first_share", "base", "eu-west", "public"),
+    );
+  });
+
+  test("an absent filter is distinct from a present one", () => {
+    // The unfiltered view and a chain tab must not share an entry either.
+    expect(panelSeriesCacheKey("first_share")).not.toBe(
+      panelSeriesCacheKey("first_share", "base"),
+    );
+  });
+
+  test("filters cannot collide across positions", () => {
+    // A naive concatenation would make (chain=a, region=b) equal to
+    // (chain=ab) and serve one tab's series on another.
+    expect(panelSeriesCacheKey("p", "a", "b")).not.toBe(panelSeriesCacheKey("p", "ab"));
+    expect(panelSeriesCacheKey("p", "", "x")).not.toBe(panelSeriesCacheKey("p", "x", ""));
+  });
+});
diff --git a/src/components/time-series-chart/scales.ts b/src/components/time-series-chart/scales.ts
index f4bd88911..1b8fd9efb 100644
--- a/src/components/time-series-chart/scales.ts
+++ b/src/components/time-series-chart/scales.ts
@@ -274,3 +274,27 @@ export function fmtTick(v: number, unit: string) {
   if (v >= 1000) return `${(v / 1000).toFixed(1)}s`;
   return `${Math.round(v)}ms`;
 }
+
+/** Cache key for a metric panel's lazily fetched long-range series.
+ *
+ * The filters belong in the key, not just the panel id. Keyed on the panel
+ * alone, the chart's own cache-hit guard returned before fetching whenever a
+ * reader switched chain, so the first chain opened was served back on every
+ * other tab. The effects DO re-run on a chain change; it is the early return
+ * that swallowed it. 1H/6H/24H never showed the fault because those render
+ * from the embedded per-filter series, which is why it presented as "only 7D
+ * and 30D are wrong". Found on bench 001 on 2026-10-29, where the First to
+ * report shares are a per-chain race, so one chain's numbers on four tabs
+ * named the wrong leader on three of them.
+ *
+ * The same class of bug was fixed once for the main series (see the `chain`
+ * prop docs in index.tsx) and left standing for panels.
+ */
+export function panelSeriesCacheKey(
+  panelId: string,
+  chain?: string,
+  region?: string,
+  tier?: string,
+): string {
+  return `${panelId}|${chain ?? ""}|${region ?? ""}|${tier ?? ""}`;
+}
diff --git a/src/lib/materialize/load.ts b/src/lib/materialize/load.ts
index ff2707dbc..89375e3ce 100644
--- a/src/lib/materialize/load.ts
+++ b/src/lib/materialize/load.ts
@@ -1011,25 +1011,10 @@ function applyDimensionsToSpec(spec: Spec, labels: Record<string, string>): Spec
     // braced form so dimension labels (chain=..., region=...) reach them
     // like every provider query. Without this a panel on a chain-dimensioned
     // bench silently mixes every chain's series.
-    metric_panels: spec.metric_panels?.map((panel) => {
-      // A panel may declare the dimensions its metric does not carry.
-      // Appending one of those matches nothing and empties the panel in
-      // silence, which is how bench 282 shipped a "Billing units per
-      // request" chart that was blank on 71 of 75 views.
-      const ignored = new Set(panel.ignore_dimensions ?? []);
-      const panelLabels = ignored.size
-        ? Object.fromEntries(
-            Object.entries(labels).filter(([k]) => !ignored.has(k)),
-          )
-        : labels;
-      return {
-        ...panel,
-        metric: injectLabels(
-          panel.metric.includes("{") ? panel.metric : `${panel.metric}{}`,
-          panelLabels,
-        ),
-      };
-    }),
+    metric_panels: spec.metric_panels?.map((panel) => ({
+      ...panel,
+      metric: panelMetricQuery(panel, labels),
+    })),
     providers: spec.providers.map((p) => ({
       ...p,
       queries: p.queries
@@ -1059,6 +1044,52 @@ function applyDimensionsToSpec(spec: Spec, labels: Record<string, string>): Spec
   };
 }
 
+/** The dimension labels a reader's filters select, ready for injectLabels.
+ *
+ * `tier` is excluded because it picks the cohort rather than narrowing a
+ * series, and an `all` value is not a filter. Exported so a caller holding
+ * loose filter strings can build the same label set the loader uses.
+ */
+export function dimensionLabels(f: BenchmarkFilters): Record<string, string> {
+  return activeFilterLabels(labelFilters(f));
+}
+
+/** The PromQL a metric panel runs under the reader's active filters.
+ *
+ * A panel declares a bare metric name or `metric{sel}`; normalise to the
+ * braced form so the dimension labels reach it like every provider query.
+ * Without this, a panel on a chain-dimensioned bench silently pools every
+ * chain into one line.
+ *
+ * Exported because TWO paths need this exact string and had drifted. The
+ * loader builds panel values through applyDimensionsToSpec, but the 7d and
+ * 30d panel SERIES are stripped from both the cache form and the snapshot on
+ * purpose (slimBenchmarkForCache, toSnapshot) and refetched by
+ * /api/series/[slug]?panel=..., which rebuilds them from the raw spec. That
+ * route injected only the provider selector, so from the day panels got a
+ * chart, every chain tab of bench 001's "First to report" view published the
+ * same cross-chain average, while the head-lag view beside it moved per chain
+ * because it goes through specToBenchmark. Lucas spotted it on 2026-10-29.
+ *
+ * A panel may also declare dimensions its metric does not carry: appending one
+ * matches nothing and empties the panel in silence, which is how bench 282
+ * shipped a "Billing units per request" chart blank on 71 of 75 views. Hence
+ * ignore_dimensions, honoured here so both callers honour it.
+ */
+export function panelMetricQuery(
+  panel: { metric: string; ignore_dimensions?: string[] },
+  labels: Record<string, string>,
+): string {
+  const ignored = new Set(panel.ignore_dimensions ?? []);
+  const panelLabels = ignored.size
+    ? Object.fromEntries(Object.entries(labels).filter(([k]) => !ignored.has(k)))
+    : labels;
+  return injectLabels(
+    panel.metric.includes("{") ? panel.metric : `${panel.metric}{}`,
+    panelLabels,
+  );
+}
+
 export function injectLabels(query: string, labels: Record<string, string>): string {
   return query.replace(/\{([^}]*)\}/g, (_, inside: string) => {
     const additions: string[] = [];
diff --git a/src/lib/materialize/panel-metric-query.test.ts b/src/lib/materialize/panel-metric-query.test.ts
new file mode 100644
index 000000000..f294adf1d
--- /dev/null
+++ b/src/lib/materialize/panel-metric-query.test.ts
@@ -0,0 +1,94 @@
+import { describe, expect, test } from "bun:test";
+import { dimensionLabels, panelMetricQuery } from "@/lib/materialize/load";
+
+/**
+ * A metric panel's query has to carry the reader's chain and region, and for a
+ * long time one of the two paths that build it did not.
+ *
+ * Panel VALUES go through applyDimensionsToSpec, so they were always scoped.
+ * Panel SERIES for 7d and 30d are stripped from the cache form and from the
+ * snapshot on purpose and refetched by /api/series/[slug]?panel=..., which
+ * rebuilds them from the raw spec on disk. That route injected only the
+ * provider selector, so bench 001's "First to report" chart published one
+ * cross-chain average under every chain tab: Codex 68.8% and Serialized 29.5%
+ * identical on Base, BNB, Solana and Robinhood, while the head-lag view
+ * beside it moved per chain because it goes through specToBenchmark.
+ *
+ * Nothing caught it because both paths hand-rolled the same string and only
+ * one of them was ever read in a test. They share one function now, and this
+ * asserts the property that was silently false.
+ */
+describe("panelMetricQuery", () => {
+  test("a bare metric name gets the active dimensions", () => {
+    expect(panelMetricQuery({ metric: "head_lag_first_share_pct" }, { chain: "base" }))
+      .toBe('head_lag_first_share_pct{chain="base"}');
+  });
+
+  test("an empty selector is filled rather than left empty", () => {
+    // This is the exact shape bench 001 declares, and the shape that made the
+    // bug invisible: `{}` looks filtered and matches everything.
+    expect(
+      panelMetricQuery(
+        { metric: "avg by (aggregator) (head_lag_first_share_pct{})" },
+        { chain: "solana", region: "eu-west" },
+      ),
+    ).toBe(
+      'avg by (aggregator) (head_lag_first_share_pct{chain="solana",region="eu-west"})',
+    );
+  });
+
+  test("an existing selector keeps its matchers and gains the dimensions", () => {
+    expect(
+      panelMetricQuery({ metric: 'rpc_call_total{result="ok"}' }, { chain: "base" }),
+    ).toBe('rpc_call_total{result="ok",chain="base"}');
+  });
+
+  test("a label the panel already pins is not duplicated", () => {
+    expect(
+      panelMetricQuery({ metric: 'head_lag_seconds{chain="bnb"}' }, { chain: "base" }),
+    ).toBe('head_lag_seconds{chain="bnb"}');
+  });
+
+  test("ignore_dimensions drops the labels the metric does not carry", () => {
+    // Appending a dimension a metric has no label for matches nothing and
+    // empties the panel in silence (bench 282, blank on 71 of 75 views).
+    expect(
+      panelMetricQuery(
+        { metric: "rpc_billing_units", ignore_dimensions: ["region"] },
+        { chain: "base", region: "eu-west" },
+      ),
+    ).toBe('rpc_billing_units{chain="base"}');
+  });
+
+  test("no active filter leaves the metric queryable", () => {
+    expect(panelMetricQuery({ metric: "head_lag_first_share_pct" }, {})).toBe(
+      "head_lag_first_share_pct{}",
+    );
+  });
+
+  test("the provider selector the route prepends survives the scoping", () => {
+    // The route does scoped.replace("{", `{${sel},`), which only works
+    // because panelMetricQuery always returns a braced form.
+    const scoped = panelMetricQuery(
+      { metric: "avg by (aggregator) (head_lag_first_share_pct{})" },
+      { chain: "robinhood" },
+    );
+    expect(scoped.replace("{", '{aggregator="codex",')).toBe(
+      'avg by (aggregator) (head_lag_first_share_pct{aggregator="codex",chain="robinhood"})',
+    );
+  });
+});
+
+describe("dimensionLabels", () => {
+  test("tier is excluded because it selects the cohort, not a slice", () => {
+    expect(dimensionLabels({ chain: "base", tier: "keyed" })).toEqual({ chain: "base" });
+  });
+
+  test('"all" is not a filter', () => {
+    expect(dimensionLabels({ chain: "all", region: "sgp" })).toEqual({ region: "sgp" });
+  });
+
+  test("an empty filter set yields no labels", () => {
+    expect(dimensionLabels({})).toEqual({});
+  });
+});