diff --git a/packages/producer/src/services/deterministicFonts-failClosed.test.ts b/packages/producer/src/services/deterministicFonts-failClosed.test.ts
index 5a1e3c1388..03d56a829c 100644
--- a/packages/producer/src/services/deterministicFonts-failClosed.test.ts
+++ b/packages/producer/src/services/deterministicFonts-failClosed.test.ts
@@ -253,6 +253,17 @@ describe("injectDeterministicFontFaces — failClosedFontFetch: true", () => {
     expect(result).toBe(html);
   });
 
+  it("does NOT throw when font-family uses a CSS var() reference with a fallback", async () => {
+    const html = `<!doctype html><html><head><style>
+      .title { font-family: var(--brand-font, inherit); }
+    </style></head><body><h1 class="title">hello</h1></body></html>`;
+    const result = await injectDeterministicFontFaces(html, {
+      failClosedFontFetch: true,
+      fetchImpl: makeFailingFetch(),
+    });
+    expect(result).toBe(html);
+  });
+
   it("resolves simple CSS var() font aliases when injecting deterministic fonts", async () => {
     const html = `<!doctype html><html><head><style>
       :root { --ui-font: "Inter"; --vowel-font: "Montserrat"; }
diff --git a/packages/producer/src/services/deterministicFonts.ts b/packages/producer/src/services/deterministicFonts.ts
index 85e3e27d8a..46496111aa 100644
--- a/packages/producer/src/services/deterministicFonts.ts
+++ b/packages/producer/src/services/deterministicFonts.ts
@@ -54,10 +54,44 @@ export const GENERIC_FAMILIES: ReadonlySet<string> = new Set([
  * Whitespace and surrounding `"…"` / `'…'` quotes are stripped; case is
  * preserved. Pass each name through `normalizeFamilyName` for case-
  * insensitive comparisons.
+ *
+ * Only top-level commas split: a `var(--x, fallback)` expression stays one
+ * token, as does a comma inside a quoted family name.
  */
 export function parseFontFamilyValue(value: string): string[] {
-  return value
-    .split(",")
+  const pieces: string[] = [];
+  let start = 0;
+  let depth = 0;
+  let quote: "'" | '"' | null = null;
+  for (let index = 0; index < value.length; index += 1) {
+    const char = value[index];
+    if (char === "\\") {
+      index += 1;
+      continue;
+    }
+    if (quote) {
+      if (char === quote) quote = null;
+      continue;
+    }
+    if (char === "'" || char === '"') {
+      quote = char;
+      continue;
+    }
+    if (char === "(") {
+      depth += 1;
+      continue;
+    }
+    if (char === ")") {
+      depth = Math.max(0, depth - 1);
+      continue;
+    }
+    if (char !== "," || depth !== 0) continue;
+    pieces.push(value.slice(start, index));
+    start = index + 1;
+  }
+  pieces.push(value.slice(start));
+
+  return pieces
     .map((piece) => piece.trim().replace(/^['"]/, "").replace(/['"]$/, "").trim())
     .filter((piece) => piece.length > 0);
 }
diff --git a/packages/producer/src/services/render/planValidation.test.ts b/packages/producer/src/services/render/planValidation.test.ts
index 7d10520b74..bdd10f761c 100644
--- a/packages/producer/src/services/render/planValidation.test.ts
+++ b/packages/producer/src/services/render/planValidation.test.ts
@@ -169,6 +169,26 @@ describe("parseFontFamilyValue", () => {
     expect(parseFontFamilyValue(`'My Custom Font', serif`)).toEqual(["My Custom Font", "serif"]);
   });
 
+  it("keeps a comma inside a quoted family name", () => {
+    expect(parseFontFamilyValue(`"Display, Condensed", serif`)).toEqual([
+      "Display, Condensed",
+      "serif",
+    ]);
+  });
+
+  it("keeps a var() fallback in a single token", () => {
+    expect(parseFontFamilyValue(`var(--brand-font, inherit), sans-serif`)).toEqual([
+      "var(--brand-font, inherit)",
+      "sans-serif",
+    ]);
+  });
+
+  it("keeps a nested var() fallback in a single token", () => {
+    expect(
+      parseFontFamilyValue(`var(--brand-font, var(--fallback-font, "Inter")), sans-serif`),
+    ).toEqual([`var(--brand-font, var(--fallback-font, "Inter"))`, "sans-serif"]);
+  });
+
   it("ignores empty entries (trailing commas)", () => {
     expect(parseFontFamilyValue(`Inter,,sans-serif`)).toEqual(["Inter", "sans-serif"]);
   });
diff --git a/packages/producer/tests/distributed/css-var-fonts/src/index.html b/packages/producer/tests/distributed/css-var-fonts/src/index.html
index 8f8221bc5b..9534fb1ea8 100644
--- a/packages/producer/tests/distributed/css-var-fonts/src/index.html
+++ b/packages/producer/tests/distributed/css-var-fonts/src/index.html
@@ -35,7 +35,7 @@
         top: 30%;
         left: 50%;
         transform: translateX(-50%);
-        font-family: var(--display-font), sans-serif;
+        font-family: var(--display-font, "Montserrat"), sans-serif;
         font-size: 48px;
         font-weight: 900;
         color: #e94560;
