diff --git a/changelog.d/fixes/12373-vision-bridge-auto-combo-guard.md b/changelog.d/fixes/12373-vision-bridge-auto-combo-guard.md
new file mode 100644
index 0000000000..033324bfc5
--- /dev/null
+++ b/changelog.d/fixes/12373-vision-bridge-auto-combo-guard.md
@@ -0,0 +1 @@
+- **fix(guardrails):** keep `auto`/`auto/*` virtual combos exempt from the Vision Bridge `fixedModel` credential guard so a combo target is passed through instead of silently falling back to global auto-selection ([#12237](https://github.com/diegosouzapw/OmniRoute/issues/12237))
diff --git a/src/lib/guardrails/visionBridgeRouter.ts b/src/lib/guardrails/visionBridgeRouter.ts
index 5660f1e557..c2dbbc9121 100644
--- a/src/lib/guardrails/visionBridgeRouter.ts
+++ b/src/lib/guardrails/visionBridgeRouter.ts
@@ -231,7 +231,9 @@ async function getVisionCapableModels(
         };
       });
 
-      return candidates.filter((candidate): candidate is VisionModelCandidate => candidate !== null);
+      return candidates.filter(
+        (candidate): candidate is VisionModelCandidate => candidate !== null
+      );
     })
   );
 
@@ -271,6 +273,51 @@ function selectBestModel(
   return scored[0];
 }
 
+/**
+ * (#12237) `auto` / `auto/*` ids are VIRTUAL combos: there is no provider
+ * row for "auto", so the credential check always reports `false` for them.
+ * Member-level credentials are enforced downstream when the combo
+ * dispatches (mirrors the reroute guard in visionBridge.ts), so a virtual
+ * combo must not be discarded by the #8430 short-circuit — otherwise the
+ * combo silently falls through to auto-selection and never rotates. It is
+ * still subject to the pool check in `getBestVisionModel`: when the ENTIRE
+ * vision pool is unusable there is nothing the combo could dispatch to, and
+ * returning the combo id would let a raw image reach a text-only backend
+ * (#8430).
+ *
+ * Returns the combo id when `fixedModel` is virtual, `undefined` otherwise.
+ */
+function resolveVirtualCombo(fixedModel: string | undefined): string | undefined {
+  return fixedModel === "auto" || fixedModel?.startsWith("auto/") ? fixedModel : undefined;
+}
+
+/**
+ * Resolve a live selection-cache entry for `cacheKey`.
+ *
+ * Returns the id to hand back: the cached member for a concrete target, or
+ * `virtualCombo` once the cached member proves it still has usable
+ * credentials (the cache never re-validates credentials, and the caller
+ * exempts virtual combos from that check). A missing or expired entry yields
+ * `null`; an entry whose member is no longer available or usable is dropped
+ * so the pool is rescanned.
+ */
+async function resolveCachedSelection(
+  cacheKey: string,
+  virtualCombo: string | undefined,
+  deps: VisionBridgeRouterDeps
+): Promise<string | null> {
+  const cached = selectionCache.get(cacheKey);
+  if (!cached || cached.expiresAt <= Date.now()) return null;
+
+  if (await cachedModelRemainsAvailable(cached.modelId, deps)) {
+    if (!virtualCombo) return cached.modelId;
+    const checkCreds = deps.hasUsableCredentials ?? hasUsableCredentialsForModel;
+    if ((await checkCreds(cached.modelId)) !== false) return virtualCombo;
+  }
+  selectionCache.delete(cacheKey);
+  return null;
+}
+
 /**
  * Get the best vision model for image description.
  * Respects fixed model override if configured, but validates it has usable
@@ -283,12 +330,15 @@ export async function getBestVisionModel(
   deps: VisionBridgeRouterDeps = {}
 ): Promise<string | null> {
   const fullConfig = { ...DEFAULT_ROUTER_CONFIG, ...config };
+  const virtualCombo = resolveVirtualCombo(fullConfig.fixedModel);
 
   // If fixed model is configured, validate it has usable credentials first.
   // (#8430) An unreachable fixedModel (e.g. the default "openai/gpt-4o-mini"
   // on an instance with no OpenAI connection/key) must not short-circuit the
   // credential check — fall through to auto-selection instead.
-  if (fullConfig.fixedModel) {
+  // (#12237) A virtual combo is exempt here and goes through the pool
+  // selection below instead; see `resolveVirtualCombo`.
+  if (fullConfig.fixedModel && !virtualCombo) {
     const checkCreds = deps.hasUsableCredentials ?? hasUsableCredentialsForModel;
     const usable = await checkCreds(fullConfig.fixedModel);
     // Only skip credential validation when the check is indeterminate (null).
@@ -304,13 +354,8 @@ export async function getBestVisionModel(
     fullConfig.excludedModels.length > 0
       ? `excl:${[...fullConfig.excludedModels].sort().join(",")}`
       : "default";
-  const cached = selectionCache.get(cacheKey);
-  if (cached && cached.expiresAt > Date.now()) {
-    if (await cachedModelRemainsAvailable(cached.modelId, deps)) {
-      return cached.modelId;
-    }
-    selectionCache.delete(cacheKey);
-  }
+  const cachedPick = await resolveCachedSelection(cacheKey, virtualCombo, deps);
+  if (cachedPick) return cachedPick;
 
   // Get all vision-capable candidates
   const candidates = await getVisionCapableModels(deps);
@@ -329,7 +374,9 @@ export async function getBestVisionModel(
     expiresAt: Date.now() + fullConfig.selectionCacheTtlMs,
   });
 
-  return best.fullName;
+  // A virtual combo is returned as-is once the pool proves at least one
+  // vision-capable member is usable; it rotates its own members downstream.
+  return virtualCombo ?? best.fullName;
 }
 
 /**
diff --git a/tests/unit/guardrails/visionBridgeRouter.test.ts b/tests/unit/guardrails/visionBridgeRouter.test.ts
index c520aa834d..7c7f75052a 100644
--- a/tests/unit/guardrails/visionBridgeRouter.test.ts
+++ b/tests/unit/guardrails/visionBridgeRouter.test.ts
@@ -80,8 +80,65 @@ test("getBestVisionModel — should exclude specified models", async () => {
 test("getBestVisionModel — excludes a candidate with no usable active connection", async () => {
   // Every candidate reports a confirmed-unusable connection (`false`) ->
   // no candidate survives -> returns null instead of an unreachable default.
+  const model = await getBestVisionModel({}, { hasUsableCredentials: async () => false });
+  assert.equal(model, null);
+});
+
+// `auto` / `auto/*` ids are VIRTUAL combos: there is no provider row for
+// "auto", so hasUsableCredentialsForModel reports a confirmed `false` for the
+// combo id itself while the pool members remain usable (indeterminate here).
+const virtualComboOnlyUnusable = async (fullModelId: string) =>
+  fullModelId === "auto" || fullModelId.startsWith("auto/") ? false : null;
+
+test("getBestVisionModel — keeps an auto/* virtual-combo fixedModel when its credential check is false (#12237)", async () => {
+  // The #8430 short-circuit must not discard the combo — member credentials
+  // are enforced downstream when the combo dispatches (same exemption as the
+  // reroute guard in visionBridge.ts).
+  const fixedModel = "auto/vision";
   const model = await getBestVisionModel(
-    {},
+    { fixedModel },
+    { hasUsableCredentials: virtualComboOnlyUnusable }
+  );
+  assert.equal(model, fixedModel);
+});
+
+test('getBestVisionModel — keeps a bare "auto" fixedModel when its credential check is false (#12237)', async () => {
+  const model = await getBestVisionModel(
+    { fixedModel: "auto" },
+    { hasUsableCredentials: virtualComboOnlyUnusable }
+  );
+  assert.equal(model, "auto");
+});
+
+test("getBestVisionModel — keeps an auto/* virtual-combo fixedModel on a cached pool selection (#12237)", async () => {
+  // Warm the selection cache with a pool pick, then ask for the combo: the
+  // cache-hit branch must still hand back the combo, not the cached member.
+  const warm = await getBestVisionModel({}, { hasUsableCredentials: virtualComboOnlyUnusable });
+  assert.ok(warm);
+  const model = await getBestVisionModel(
+    { fixedModel: "auto/vision" },
+    { hasUsableCredentials: virtualComboOnlyUnusable }
+  );
+  assert.equal(model, "auto/vision");
+});
+
+test("getBestVisionModel — discards an auto/* virtual-combo fixedModel when the ENTIRE vision pool is unusable (#8430)", async () => {
+  // The exemption only bypasses the credential check on the virtual id. With
+  // no usable vision-capable member anywhere, the combo has nothing to
+  // dispatch to and must fall through to `null` so the caller describes
+  // instead of forwarding a raw image to a text-only backend.
+  const model = await getBestVisionModel(
+    { fixedModel: "auto/vision" },
+    { hasUsableCredentials: async () => false }
+  );
+  assert.equal(model, null);
+});
+
+test("getBestVisionModel — still falls through when a concrete fixedModel has no usable credentials (#8430)", async () => {
+  // Regression guard for the exemption above: a non-virtual fixedModel with
+  // a confirmed-unusable credential check must still be discarded.
+  const model = await getBestVisionModel(
+    { fixedModel: "openai/gpt-4o-mini" },
     { hasUsableCredentials: async () => false }
   );
   assert.equal(model, null);
@@ -105,20 +162,17 @@ test("getBestVisionModel — does not query live catalogs for providers without
   assert.equal(catalogCalls, 0);
 });
 
-test(
-  "getBestVisionModel — selects a credentialed candidate over an uncredentialed higher-priority one",
-  async () => {
-    // openai (priority 50, would normally win) has no usable connection;
-    // every other vision-capable provider does.
-    const model = await getBestVisionModel(
-      {},
-      {
-        hasUsableCredentials: async (fullModelId) => fullModelId.split("/")[0] !== "openai",
-      }
-    );
-    assert.equal(model.startsWith("openai/"), false);
-  }
-);
+test("getBestVisionModel — selects a credentialed candidate over an uncredentialed higher-priority one", async () => {
+  // openai (priority 50, would normally win) has no usable connection;
+  // every other vision-capable provider does.
+  const model = await getBestVisionModel(
+    {},
+    {
+      hasUsableCredentials: async (fullModelId) => fullModelId.split("/")[0] !== "openai",
+    }
+  );
+  assert.equal(model.startsWith("openai/"), false);
+});
 
 test("getBestVisionModel — excludes static models missing from an authoritative live catalog", async () => {
   const model = await getBestVisionModel(
@@ -188,17 +242,14 @@ test("getFallbackModels — should respect max fallback attempts", async () => {
   assert.ok(fallbacks.length <= 2);
 });
 
-test(
-  "getFallbackModels — does not include candidates with a confirmed-unusable connection",
-  async () => {
-    const fallbacks = await getFallbackModels(
-      "openai/gpt-4o-mini",
-      {},
-      { hasUsableCredentials: async (fullModelId) => fullModelId.split("/")[0] !== "anthropic" }
-    );
-    assert.ok(!fallbacks.some((m) => m.startsWith("anthropic/")));
-  }
-);
+test("getFallbackModels — does not include candidates with a confirmed-unusable connection", async () => {
+  const fallbacks = await getFallbackModels(
+    "openai/gpt-4o-mini",
+    {},
+    { hasUsableCredentials: async (fullModelId) => fullModelId.split("/")[0] !== "anthropic" }
+  );
+  assert.ok(!fallbacks.some((m) => m.startsWith("anthropic/")));
+});
 
 test("getFallbackModels — excludes fallbacks missing from an authoritative live catalog", async () => {
   const fallbacks = await getFallbackModels(