diff --git a/client/src/pages/AdminErrors.tsx b/client/src/pages/AdminErrors.tsx
index e0bdb93..e591b9b 100644
--- a/client/src/pages/AdminErrors.tsx
+++ b/client/src/pages/AdminErrors.tsx
@@ -1,6 +1,7 @@
 import { useState, useRef, useCallback, useEffect } from "react";
 import { formatDate, formatDateTime } from "@/lib/date-format";
 import { useQuery, useMutation } from "@tanstack/react-query";
+import { buildBatchDeletePayload } from "./adminErrorsUtils";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 import { Badge } from "@/components/ui/badge";
 import { Button } from "@/components/ui/button";
@@ -265,25 +266,13 @@ export default function AdminErrors() {
   }, [finalizePrevious, batchDeleteMutation]);
 
   const handleBatchDelete = useCallback(() => {
-    if (selectAll) {
-      const filters: { level?: string; source?: string } = {};
-      if (levelFilter !== "all") filters.level = levelFilter;
-      if (sourceFilter !== "all") filters.source = sourceFilter;
-      if (!filters.level && !filters.source) {
-        toast({ title: "Filter required", description: "Apply a level or source filter before deleting all entries", variant: "destructive" });
-        return;
-      }
-      const excluded = Array.from(excludedIds);
-      finalizePrevious();
-      batchDeleteMutation.mutate({
-        filters,
-        ...(excluded.length > 0 ? { excludeIds: excluded } : {}),
-      });
-    } else {
-      finalizePrevious();
-      batchDeleteMutation.mutate({ ids: Array.from(selectedIds) });
-    }
-  }, [finalizePrevious, batchDeleteMutation, selectAll, selectedIds, excludedIds, levelFilter, sourceFilter, toast]);
+    const payload = buildBatchDeletePayload({
+      selectAll, selectedIds, excludedIds, levelFilter, sourceFilter, logs,
+    });
+    if (!payload) return;
+    finalizePrevious();
+    batchDeleteMutation.mutate(payload);
+  }, [finalizePrevious, batchDeleteMutation, selectAll, selectedIds, excludedIds, levelFilter, sourceFilter, logs]);
 
   const selectionCount = selectAll ? logs.length - excludedIds.size : selectedIds.size;
   const hasSelection = selectionCount > 0;
@@ -670,7 +659,7 @@ export default function AdminErrors() {
                 aria-label="Select all entries"
               />
               <span className="text-sm text-muted-foreground">
-                {selectAll ? "All matching entries selected" : "Select all"}
+                {selectAll ? `All ${logs.length} visible entries selected` : "Select all"}
               </span>
             </div>
             <div className="space-y-2">
@@ -772,7 +761,7 @@ export default function AdminErrors() {
         <div className="fixed bottom-6 left-1/2 -translate-x-1/2 z-50" data-testid="floating-action-bar">
           <div className="flex items-center gap-3 bg-background border rounded-lg shadow-lg px-4 py-3">
             <span className="text-sm font-medium" data-testid="text-selection-count">
-              {selectAll ? `All matching entries` : `${selectionCount} selected`}
+              {selectAll ? `${selectionCount} visible entries` : `${selectionCount} selected`}
             </span>
             <Button
               variant="destructive"
diff --git a/client/src/pages/adminErrorsUtils.test.ts b/client/src/pages/adminErrorsUtils.test.ts
new file mode 100644
index 0000000..5f398c5
--- /dev/null
+++ b/client/src/pages/adminErrorsUtils.test.ts
@@ -0,0 +1,116 @@
+import { describe, it, expect } from "vitest";
+import { buildBatchDeletePayload } from "./adminErrorsUtils";
+
+const defaults = {
+  selectAll: false,
+  selectedIds: new Set<number>(),
+  excludedIds: new Set<number>(),
+  levelFilter: "all",
+  sourceFilter: "all",
+  logs: [{ id: 1 }, { id: 2 }, { id: 3 }],
+};
+
+describe("buildBatchDeletePayload", () => {
+  // --- individual selection (selectAll = false) ---
+
+  it("returns ids when individual entries are selected", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectedIds: new Set([1, 3]),
+    });
+    expect(result).toEqual({ ids: [1, 3] });
+  });
+
+  it("returns null when no individual entries are selected", () => {
+    const result = buildBatchDeletePayload(defaults);
+    expect(result).toBeNull();
+  });
+
+  // --- selectAll with filters ---
+
+  it("returns filter-based payload when level filter is active", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      levelFilter: "error",
+    });
+    expect(result).toEqual({ filters: { level: "error" } });
+  });
+
+  it("returns filter-based payload when source filter is active", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      sourceFilter: "scheduler",
+    });
+    expect(result).toEqual({ filters: { source: "scheduler" } });
+  });
+
+  it("returns filter-based payload with both filters", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      levelFilter: "warning",
+      sourceFilter: "api",
+    });
+    expect(result).toEqual({ filters: { level: "warning", source: "api" } });
+  });
+
+  it("includes excludeIds when filters are active and entries are excluded", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      levelFilter: "error",
+      excludedIds: new Set([2]),
+    });
+    expect(result).toEqual({ filters: { level: "error" }, excludeIds: [2] });
+  });
+
+  it("omits excludeIds when the set is empty", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      levelFilter: "error",
+      excludedIds: new Set(),
+    });
+    expect(result).toEqual({ filters: { level: "error" } });
+    expect(result).not.toHaveProperty("excludeIds");
+  });
+
+  // --- selectAll without filters (the bug fix) ---
+
+  it("falls back to visible log ids when no filters are active", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+    });
+    expect(result).toEqual({ ids: [1, 2, 3] });
+  });
+
+  it("excludes entries from the ids fallback when excludedIds is set", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      excludedIds: new Set([2]),
+    });
+    expect(result).toEqual({ ids: [1, 3] });
+  });
+
+  it("returns null when selectAll is true but all entries are excluded", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      excludedIds: new Set([1, 2, 3]),
+    });
+    expect(result).toBeNull();
+  });
+
+  it("returns null when selectAll is true with no filters and logs are empty", () => {
+    const result = buildBatchDeletePayload({
+      ...defaults,
+      selectAll: true,
+      logs: [],
+    });
+    expect(result).toBeNull();
+  });
+});
diff --git a/client/src/pages/adminErrorsUtils.ts b/client/src/pages/adminErrorsUtils.ts
new file mode 100644
index 0000000..af4dfa7
--- /dev/null
+++ b/client/src/pages/adminErrorsUtils.ts
@@ -0,0 +1,46 @@
+/**
+ * Pure utility for computing the batch-delete payload for admin error logs.
+ * Extracted so the branching logic can be unit-tested without React.
+ */
+
+export type BatchDeletePayload =
+  | { ids: number[] }
+  | { filters: { level?: string; source?: string }; excludeIds?: number[] };
+
+/**
+ * Decides which payload shape to send to POST /api/admin/error-logs/batch-delete.
+ *
+ * @returns the payload, or `null` when there is nothing to delete.
+ */
+export function buildBatchDeletePayload(opts: {
+  selectAll: boolean;
+  selectedIds: Set<number>;
+  excludedIds: Set<number>;
+  levelFilter: string;
+  sourceFilter: string;
+  logs: { id: number }[];
+}): BatchDeletePayload | null {
+  const { selectAll, selectedIds, excludedIds, levelFilter, sourceFilter, logs } = opts;
+
+  if (!selectAll) {
+    const ids = Array.from(selectedIds);
+    return ids.length > 0 ? { ids } : null;
+  }
+
+  // selectAll path — prefer filter-based delete when a filter is active
+  const filters: { level?: string; source?: string } = {};
+  if (levelFilter !== "all") filters.level = levelFilter;
+  if (sourceFilter !== "all") filters.source = sourceFilter;
+
+  if (filters.level || filters.source) {
+    const excluded = Array.from(excludedIds);
+    return {
+      filters,
+      ...(excluded.length > 0 ? { excludeIds: excluded } : {}),
+    };
+  }
+
+  // No filters — fall back to sending visible IDs directly
+  const ids = logs.filter(l => !excludedIds.has(l.id)).map(l => l.id);
+  return ids.length > 0 ? { ids } : null;
+}