diff --git a/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.test.ts b/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.test.ts
index 4e81fc46d3..3f029b6eac 100644
--- a/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.test.ts
+++ b/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.test.ts
@@ -61,3 +61,64 @@ describe('installPdfjsDomGlobals base64 codecs', () => {
     expect(new TextDecoder().decode(plaintext)).toBe('integration-secret');
   });
 });
+
+describe('installPdfjsDomGlobals Map.getOrInsertComputed', () => {
+  it('installs the method pdfjs calls on its Maps', () => {
+    // Its absence is what broke the operator-list read per page (#3018).
+    installPdfjsDomGlobals();
+    expect(typeof Map.prototype.getOrInsertComputed).toBe('function');
+  });
+
+  it('computes and inserts when the key is absent', () => {
+    installPdfjsDomGlobals();
+    const map = new Map<string, number>();
+    const calls: string[] = [];
+    const value = map.getOrInsertComputed('a', (key) => {
+      calls.push(key);
+      return 1;
+    });
+    expect(value).toBe(1);
+    expect(map.get('a')).toBe(1);
+    expect(calls).toEqual(['a']);
+  });
+
+  it('returns the existing value without calling the callback', () => {
+    // pdfjs relies on this: the callback builds an intent state, and calling
+    // it twice would discard the one already in flight.
+    installPdfjsDomGlobals();
+    const map = new Map<string, number>([['a', 1]]);
+    let called = false;
+    const value = map.getOrInsertComputed('a', () => {
+      called = true;
+      return 2;
+    });
+    expect(value).toBe(1);
+    expect(called).toBe(false);
+  });
+
+  it('stores a value the callback returns even when it is undefined', () => {
+    // Presence, not truthiness: a second call must not recompute.
+    installPdfjsDomGlobals();
+    const map = new Map<string, undefined>();
+    map.getOrInsertComputed('a', () => undefined);
+    expect(map.has('a')).toBe(true);
+    let recomputed = false;
+    map.getOrInsertComputed('a', () => {
+      recomputed = true;
+      return undefined;
+    });
+    expect(recomputed).toBe(false);
+  });
+
+  it('refuses a callback that is not callable', () => {
+    installPdfjsDomGlobals();
+    const map = new Map<string, number>();
+    expect(() =>
+      // oxlint-disable-next-line typescript/no-unsafe-type-assertion -- the guard exists for callers without types
+      map.getOrInsertComputed(
+        'a',
+        undefined as unknown as (k: string) => number,
+      ),
+    ).toThrow(TypeError);
+  });
+});
diff --git a/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.ts b/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.ts
index cfe9bcf11a..88af27e2fe 100644
--- a/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.ts
+++ b/services/platform/backend/core/lib/knowledge/extraction/pdfjs_dom_polyfill.ts
@@ -1,8 +1,8 @@
 'use node';
 
 /**
- * Pure-JS DOM-global polyfills for running pdfjs-dist in the Convex node
- * action runtime.
+ * Pure-JS DOM-global polyfills, plus the ES2025 shims pdfjs expects, for
+ * running pdfjs-dist on the backend's Node worker.
  *
  * pdfjs 5.x's Node setup polyfills `DOMMatrix` / `ImageData` / `Path2D` by
  * `require("@napi-rs/canvas")` — a NATIVE module. Convex extracts a bundled
@@ -324,6 +324,37 @@ function ensureEs2025Shims(): void {
     });
   }
 
+  // pdfjs 5.x calls this on plain Maps in both the main and worker builds
+  // (`_intentStates`, `methodPromises`, `objs`, …). Node 22 lacks it, and the
+  // failure is quiet: the operator-list read throws once per page, and that is
+  // the path that finds embedded images and decides "scanned page → OCR". Text
+  // extraction still runs, so a digital PDF looks fine while a scanned one
+  // indexes thin or empty with only a warning to say so (#3018).
+  //
+  // Spec shape: return the existing value when the key is present; otherwise
+  // compute, insert, and return. Presence, not truthiness — a callback that
+  // returns `undefined` still counts, so a second call does not recompute.
+  // `set` runs after the callback, as the proposal does: the callback may have
+  // inserted the key itself, and the computed value wins.
+  if (typeof Map.prototype.getOrInsertComputed !== 'function') {
+    // oxlint-disable-next-line no-extend-native -- deliberate spec-shaped polyfill of an ES2025 method Node 22 lacks; guarded so a real runtime implementation wins
+    Object.defineProperty(Map.prototype, 'getOrInsertComputed', {
+      value: function <K, V>(this: Map<K, V>, key: K, callbackfn: (k: K) => V) {
+        if (typeof callbackfn !== 'function') {
+          throw new TypeError(
+            'Map.prototype.getOrInsertComputed: callback is not a function',
+          );
+        }
+        if (this.has(key)) return this.get(key);
+        const value = callbackfn(key);
+        this.set(key, value);
+        return value;
+      },
+      writable: true,
+      configurable: true,
+    });
+  }
+
   // Install when missing, or replace a process-global poison shim that
   // ignores `alphabet` (regression: always-`base64` loop). Native Node ≥24
   // / Bun implementations honor options and win the probe below.