diff --git a/agent/auxiliary_client.py b/agent/auxiliary_client.py
index 2b93a3f918..2854873b81 100644
--- a/agent/auxiliary_client.py
+++ b/agent/auxiliary_client.py
@@ -2021,24 +2021,35 @@ def resolve_vision_provider_client(
         #      _PROVIDER_VISION_MODELS provides per-provider vision model
         #      overrides when the provider has a dedicated multimodal model
         #      that differs from the chat model (e.g. xiaomi → mimo-v2-omni,
-        #      zai → glm-5v-turbo).
+        #      zai → glm-5v-turbo). Nous is the exception: it has a dedicated
+        #      strict vision backend with tier-aware defaults, so it must not
+        #      fall through to the user's text chat model here.
         #   2. OpenRouter  (vision-capable aggregator fallback)
         #   3. Nous Portal (vision-capable aggregator fallback)
         #   4. Stop
         main_provider = _read_main_provider()
         main_model = _read_main_model()
         if main_provider and main_provider not in ("auto", ""):
-            vision_model = _PROVIDER_VISION_MODELS.get(main_provider, main_model)
-            rpc_client, rpc_model = resolve_provider_client(
-                main_provider, vision_model,
-                api_mode=resolved_api_mode)
-            if rpc_client is not None:
-                logger.info(
-                    "Vision auto-detect: using main provider %s (%s)",
-                    main_provider, rpc_model or vision_model,
-                )
-                return _finalize(
-                    main_provider, rpc_client, rpc_model or vision_model)
+            if main_provider == "nous":
+                sync_client, default_model = _resolve_strict_vision_backend(main_provider)
+                if sync_client is not None:
+                    logger.info(
+                        "Vision auto-detect: using main provider %s (%s)",
+                        main_provider, default_model or resolved_model or main_model,
+                    )
+                    return _finalize(main_provider, sync_client, default_model)
+            else:
+                vision_model = _PROVIDER_VISION_MODELS.get(main_provider, main_model)
+                rpc_client, rpc_model = resolve_provider_client(
+                    main_provider, vision_model,
+                    api_mode=resolved_api_mode)
+                if rpc_client is not None:
+                    logger.info(
+                        "Vision auto-detect: using main provider %s (%s)",
+                        main_provider, rpc_model or vision_model,
+                    )
+                    return _finalize(
+                        main_provider, rpc_client, rpc_model or vision_model)
 
         # Fall back through aggregators (uses their dedicated vision model,
         # not the user's main model) when main provider has no client.
diff --git a/tests/agent/test_auxiliary_main_first.py b/tests/agent/test_auxiliary_main_first.py
index 353c6c2ddc..d756d6ffb1 100644
--- a/tests/agent/test_auxiliary_main_first.py
+++ b/tests/agent/test_auxiliary_main_first.py
@@ -167,7 +167,7 @@ class TestResolveAutoMainFirst:
 
 
 class TestResolveVisionMainFirst:
-    """Vision auto-detection prefers main provider + main model first."""
+    """Vision auto-detection prefers the main provider first."""
 
     def test_openrouter_main_vision_uses_main_model(self, monkeypatch):
         """OpenRouter main with vision-capable model → aux vision uses main model."""
@@ -200,28 +200,49 @@ class TestResolveVisionMainFirst:
         assert mock_resolve.call_args.args[0] == "openrouter"
         assert mock_resolve.call_args.args[1] == "anthropic/claude-sonnet-4.6"
 
-    def test_nous_main_vision_uses_main_model(self):
-        """Nous Portal main → aux vision uses main model, not free-tier MiMo-V2-Omni."""
+    def test_nous_main_vision_uses_paid_nous_vision_backend(self):
+        """Paid Nous main → aux vision uses the dedicated Nous vision backend."""
         with patch(
             "agent.auxiliary_client._read_main_provider", return_value="nous",
         ), patch(
             "agent.auxiliary_client._read_main_model",
             return_value="openai/gpt-5",
         ), patch(
-            "agent.auxiliary_client.resolve_provider_client"
-        ) as mock_resolve, patch(
             "agent.auxiliary_client._resolve_task_provider_model",
             return_value=("auto", None, None, None, None),
+        ), patch(
+            "agent.auxiliary_client._resolve_strict_vision_backend",
+            return_value=(MagicMock(), "google/gemini-3-flash-preview"),
         ):
-            mock_client = MagicMock()
-            mock_resolve.return_value = (mock_client, "openai/gpt-5")
-
             from agent.auxiliary_client import resolve_vision_provider_client
 
             provider, client, model = resolve_vision_provider_client()
 
         assert provider == "nous"
-        assert model == "openai/gpt-5"
+        assert client is not None
+        assert model == "google/gemini-3-flash-preview"
+
+    def test_nous_main_vision_uses_free_tier_nous_vision_backend(self):
+        """Free-tier Nous main → aux vision uses MiMo omni, not the text main model."""
+        with patch(
+            "agent.auxiliary_client._read_main_provider", return_value="nous",
+        ), patch(
+            "agent.auxiliary_client._read_main_model",
+            return_value="xiaomi/mimo-v2-pro",
+        ), patch(
+            "agent.auxiliary_client._resolve_task_provider_model",
+            return_value=("auto", None, None, None, None),
+        ), patch(
+            "agent.auxiliary_client._resolve_strict_vision_backend",
+            return_value=(MagicMock(), "xiaomi/mimo-v2-omni"),
+        ):
+            from agent.auxiliary_client import resolve_vision_provider_client
+
+            provider, client, model = resolve_vision_provider_client()
+
+        assert provider == "nous"
+        assert client is not None
+        assert model == "xiaomi/mimo-v2-omni"
 
     def test_exotic_provider_with_vision_override_preserved(self):
         """xiaomi → mimo-v2-omni override still wins over main_model."""