diff --git a/packages/db/src/queries/benchmarks.test.ts b/packages/db/src/queries/benchmarks.test.ts
new file mode 100644
index 00000000..3e32a780
--- /dev/null
+++ b/packages/db/src/queries/benchmarks.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest';
+
+import type { DbClient } from '../connection.js';
+import { getAllBenchmarksForHistory, getLatestBenchmarks } from './benchmarks.js';
+
+/**
+ * A {@link DbClient} stand-in that records every SQL template it is handed and
+ * resolves to an empty result set. Lets us assert on the *generated SQL* without
+ * a live database — in particular that the read path never names the optional
+ * `workers` column directly.
+ *
+ * Joining the template's static segments with a ` ? ` placeholder reconstructs
+ * the literal SQL (interpolated values like model keys / dates become `?`),
+ * which is all we need to substring-match the column selection.
+ */
+function makeRecordingSql(): { sql: DbClient; sqlText: () => string } {
+  const queries: string[] = [];
+  const sql = ((strings: TemplateStringsArray, ..._values: unknown[]) => {
+    queries.push(strings.join(' ? '));
+    return Promise.resolve([]);
+  }) as DbClient;
+  return { sql, sqlText: () => queries.join('\n') };
+}
+
+/**
+ * Regression guard for the #405 fallout: the read queries must surface `workers`
+ * via `to_jsonb(row) -> 'workers'`, NOT a bare `br.workers` / `lb.workers`. A bare
+ * column reference fails to plan ("column \"workers\" does not exist") when migration
+ * 006 hasn't been applied, which 500s every cache-miss request to /api/v1/benchmarks.
+ * The to_jsonb form returns null for the absent column and lets the endpoint keep
+ * serving everything else.
+ */
+describe('benchmark read queries — workers column tolerance', () => {
+  it('getLatestBenchmarks (no-date / materialized-view branch) does not reference lb.workers directly', async () => {
+    const { sql, sqlText } = makeRecordingSql();
+    await getLatestBenchmarks(sql, 'dsr1');
+    const text = sqlText();
+    expect(text).toContain("to_jsonb(lb) -> 'workers'");
+    expect(text).not.toMatch(/\blb\.workers\b/u);
+  });
+
+  it('getLatestBenchmarks (date-filtered / base-table branch) does not reference br.workers directly', async () => {
+    const { sql, sqlText } = makeRecordingSql();
+    await getLatestBenchmarks(sql, 'dsr1', '2026-01-01');
+    const text = sqlText();
+    expect(text).toContain("to_jsonb(br) -> 'workers'");
+    expect(text).not.toMatch(/\bbr\.workers\b/u);
+  });
+
+  it('getAllBenchmarksForHistory does not reference br.workers directly', async () => {
+    const { sql, sqlText } = makeRecordingSql();
+    await getAllBenchmarksForHistory(sql, 'dsr1', 1024, 1024);
+    const text = sqlText();
+    expect(text).toContain("to_jsonb(br) -> 'workers'");
+    expect(text).not.toMatch(/\bbr\.workers\b/u);
+  });
+});
diff --git a/packages/db/src/queries/benchmarks.ts b/packages/db/src/queries/benchmarks.ts
index a2167e95..b3a6e96f 100644
--- a/packages/db/src/queries/benchmarks.ts
+++ b/packages/db/src/queries/benchmarks.ts
@@ -90,7 +90,11 @@ export async function getLatestBenchmarks(
         br.conc,
         br.image,
         br.metrics,
-        br.workers,
+        -- Read workers via to_jsonb(row)->'workers' rather than a bare column ref so the
+        -- query still plans (and returns null) if migration 006 has not been applied yet.
+        -- A bare column reference throws "column does not exist" at parse time and 500s the
+        -- whole endpoint. See migration 006_benchmark_results_workers.sql.
+        to_jsonb(br) -> 'workers' AS workers,
         br.date::text,
         CASE WHEN wr.html_url IS NOT NULL THEN wr.html_url || '/attempts/' || wr.run_attempt ELSE NULL END AS run_url
       FROM benchmark_results br
@@ -129,7 +133,8 @@ export async function getLatestBenchmarks(
       lb.conc,
       lb.image,
       lb.metrics,
-      lb.workers,
+      -- to_jsonb(row)->'workers' guard: tolerate a pre-migration-006 view (see date branch above).
+      to_jsonb(lb) -> 'workers' AS workers,
       lb.date::text,
       CASE WHEN wr.html_url IS NOT NULL THEN wr.html_url || '/attempts/' || wr.run_attempt ELSE NULL END AS run_url
     FROM latest_benchmarks lb
@@ -176,7 +181,8 @@ export async function getAllBenchmarksForHistory(
       br.osl,
       br.conc,
       br.metrics - '{std_ttft,std_tpot,std_e2el,std_intvty,std_itl,mean_ttft,mean_tpot,mean_e2el,mean_intvty,mean_itl}'::text[] as metrics,
-      br.workers,
+      -- to_jsonb(row)->'workers' guard: tolerate a pre-migration-006 base table (see getLatestBenchmarks).
+      to_jsonb(br) -> 'workers' AS workers,
       br.date::text,
       CASE WHEN wr.html_url IS NOT NULL THEN wr.html_url || '/attempts/' || wr.run_attempt ELSE NULL END AS run_url
     FROM configs c