diff --git a/packages/core/src/__tests__/provider-catalog-contract.test.ts b/packages/core/src/__tests__/provider-catalog-contract.test.ts
index ef03f43fa2..2db51dde6a 100644
--- a/packages/core/src/__tests__/provider-catalog-contract.test.ts
+++ b/packages/core/src/__tests__/provider-catalog-contract.test.ts
@@ -213,3 +213,32 @@ describe('provider catalog contract — fallback lifecycle', () => {
     assert.deepEqual(regressed, []);
   });
 });
+
+describe('opencode-free retired-model quarantine', () => {
+  const opencodeFree = PROVIDER_REGISTRY['opencode-free'];
+
+  // Ox Alpha Free (x-preview-f-free) was retired upstream on OpenCode Zen while
+  // models.dev still snapshots it free+active, so the derivation would keep
+  // offering it as a default-enabled, picker-visible row. Remove this assertion
+  // together with the OPENCODE_FREE_BROKEN_MODEL_IDS entry once the snapshot
+  // marks it deprecated (or upstream serves it again).
+  it('quarantines x-preview-f-free out of the offered free models', () => {
+    assert.ok(opencodeFree.brokenModelIds?.includes('x-preview-f-free'));
+    assert.ok(!(opencodeFree.fallbackModels ?? []).includes('x-preview-f-free'));
+    assert.ok(!(opencodeFree.defaultEnabledModelIds ?? []).includes('x-preview-f-free'));
+  });
+
+  // Mechanism guard, independent of which ids the deny-list holds: a quarantined
+  // id must never leak back into the offered candidates through either path.
+  it('never offers a quarantined broken id as a free candidate', () => {
+    const broken = new Set(opencodeFree.brokenModelIds ?? []);
+    const offered = [
+      ...(opencodeFree.fallbackModels ?? []),
+      ...(opencodeFree.defaultEnabledModelIds ?? []),
+    ];
+    assert.deepEqual(
+      offered.filter((id) => broken.has(id)),
+      [],
+    );
+  });
+});
diff --git a/packages/core/src/provider-registry.ts b/packages/core/src/provider-registry.ts
index 36c3c44d0a..b14019357b 100644
--- a/packages/core/src/provider-registry.ts
+++ b/packages/core/src/provider-registry.ts
@@ -673,7 +673,16 @@ const opencodeGoModelIds = toolCallingModelIds(
 // probes, max_tokens 8–200) — a failure shape that even "the send settles it"
 // cannot surface, which is why these ids are also vetoed in
 // `authorizeConnectionModel` rather than merely dropped from this derivation.
-const OPENCODE_FREE_BROKEN_MODEL_IDS = new Set(['muse-spark-1.2-contributor-free']);
+// 2026-08-30 x-preview-f-free (Ox Alpha Free): retired upstream — dropped from
+// the anonymous /models listing and every completion returns HTTP 401
+// {"type":"ModelError","message":"Model x-preview-f-free is not supported"}.
+// models.dev still snapshots it as free+active, so the derivation kept offering
+// it as a default-enabled, picker-visible row until this quarantine. Remove
+// once the snapshot marks it deprecated (or upstream serves it again).
+const OPENCODE_FREE_BROKEN_MODEL_IDS = new Set([
+  'muse-spark-1.2-contributor-free',
+  'x-preview-f-free',
+]);
 const opencodeFreeModelIds = toolCallingModelIds(
   'OpenCode Free',
   Object.fromEntries(