feat(image_routing): accept vision alias for custom provider models

Extend the existing candidate-name resolver in _supports_vision_override
to accept 'vision' as an alias for 'supports_vision' on per-model config,
for both the providers.<name>.models dict and the legacy list-style
custom_providers form.

Per review feedback on #31912: this extends the current resolver rather
than replacing its candidate-name logic. Named custom providers resolve
to the runtime value provider='custom' while the config keeps the
user-declared name under model.provider; that lookup path is preserved.

Adds regression tests covering model.provider=my-vllm with runtime
provider='custom' for both config shapes.

agent/image_routing.py

@@ -194,6 +194,10 @@ def _supports_vision_override(
          and/or the user-declared name under ``model.provider``; all are
          tried. For ``custom:<name>`` syntax, the stripped ``<name>`` is also
          tried as a provider key.)
+      2b. ``custom_providers`` (legacy list form) ``.models.<model>``
+
+    Under (2) and (2b), the per-model capability key may be written as
+    either ``supports_vision`` or the shorter ``vision`` alias; both work.
 
     Returns None when no override is set, so the caller falls through to
     models.dev. Returns False explicitly only when the user wrote a
@@ -234,7 +238,9 @@ def _supports_vision_override(
         models_cfg: Dict[str, Any] = models_raw if isinstance(models_raw, dict) else {}
         per_model_raw = models_cfg.get(model)
         per_model: Dict[str, Any] = per_model_raw if isinstance(per_model_raw, dict) else {}
-        coerced = _coerce_capability_bool(per_model.get("supports_vision"))
+        coerced = _coerce_capability_bool(
+            per_model.get("supports_vision", per_model.get("vision"))
+        )
         if coerced is not None:
             return coerced
 
@@ -258,7 +264,9 @@ def _supports_vision_override(
                 models_cfg = models_raw if isinstance(models_raw, dict) else {}
                 per_model_raw = models_cfg.get(model)
                 per_model = per_model_raw if isinstance(per_model_raw, dict) else {}
-                coerced = _coerce_capability_bool(per_model.get("supports_vision"))
+                coerced = _coerce_capability_bool(
+                    per_model.get("supports_vision", per_model.get("vision"))
+                )
                 if coerced is not None:
                     return coerced
 

tests/agent/test_image_routing.py

@@ -874,3 +874,99 @@ class TestFormatCompatibility:
         img_path.write_bytes(b'<svg xmlns="http://www.w3.org/2000/svg" width="4" height="4"/>')
         url = _file_to_data_url(img_path)
         assert url is None
+
+
+# ─── vision alias for custom providers ──────────────────────────────────────
+
+
+class TestCustomProviderVisionAlias:
+    """`vision: true` should work as an alias for `supports_vision: true`.
+
+    Covers both config shapes that host named custom providers:
+      * the ``providers.<name>.models`` dict, and
+      * the legacy list-style ``custom_providers`` entries.
+
+    Regression for the review of PR #31912: named custom providers resolve
+    to the runtime value ``provider="custom"`` while the config keeps the
+    user-declared name under ``model.provider``. The existing candidate-name
+    resolver must be *extended* to accept the ``vision`` alias, not replaced.
+    """
+
+    def test_providers_dict_vision_alias_true(self):
+        cfg = {
+            "providers": {
+                "my-vllm": {"models": {"llava-v1.6": {"vision": True}}}
+            }
+        }
+        assert _supports_vision_override(cfg, "my-vllm", "llava-v1.6") is True
+
+    def test_providers_dict_vision_alias_false(self):
+        cfg = {
+            "providers": {
+                "my-vllm": {"models": {"llama-3": {"vision": False}}}
+            }
+        }
+        assert _supports_vision_override(cfg, "my-vllm", "llama-3") is False
+
+    def test_supports_vision_wins_over_vision_alias(self):
+        """When both keys are present, the canonical key takes priority."""
+        cfg = {
+            "providers": {
+                "my-vllm": {
+                    "models": {
+                        "m": {"supports_vision": True, "vision": False}
+                    }
+                }
+            }
+        }
+        assert _supports_vision_override(cfg, "my-vllm", "m") is True
+
+    def test_named_custom_provider_bare_custom_runtime_vision_alias(self):
+        """Teknium's requested regression case.
+
+        A named custom provider (``model.provider: my-vllm``) is rewritten to
+        the runtime value ``provider="custom"`` by
+        ``hermes_cli/runtime_provider.py``. The resolver must still match the
+        ``my-vllm`` entry via the ``model.provider`` candidate and honour the
+        ``vision`` alias.
+        """
+        cfg = {
+            "model": {"provider": "my-vllm"},
+            "providers": {
+                "my-vllm": {"models": {"llava-v1.6": {"vision": True}}}
+            },
+        }
+        # Runtime provider is the bare normalized value "custom".
+        assert _supports_vision_override(cfg, "custom", "llava-v1.6") is True
+        assert decide_image_input_mode("custom", "llava-v1.6", cfg) == "native"
+
+    def test_custom_providers_list_bare_custom_runtime_vision_alias(self):
+        """Same regression, but the provider lives in the legacy list form."""
+        cfg = {
+            "model": {"provider": "my-vllm"},
+            "custom_providers": [
+                {
+                    "name": "my-vllm",
+                    "models": {"llava-v1.6": {"vision": True}},
+                }
+            ],
+        }
+        assert _supports_vision_override(cfg, "custom", "llava-v1.6") is True
+        assert decide_image_input_mode("custom", "llava-v1.6", cfg) == "native"
+
+    def test_custom_providers_list_vision_alias_false(self):
+        cfg = {
+            "model": {"provider": "my-vllm"},
+            "custom_providers": [
+                {"name": "my-vllm", "models": {"llama-3": {"vision": False}}}
+            ],
+        }
+        assert _supports_vision_override(cfg, "custom", "llama-3") is False
+
+    def test_vision_alias_none_when_model_absent(self):
+        cfg = {
+            "custom_providers": [
+                {"name": "my-vllm", "models": {"llava": {"vision": True}}}
+            ]
+        }
+        assert _supports_vision_override(cfg, "custom:my-vllm", "other") is None