fix(image-gen): classify unsupported Codex image accounts

plugins/image_gen/openai-codex/__init__.py

@@ -40,6 +40,24 @@ from agent.image_gen_provider import (
 logger = logging.getLogger(__name__)
 
 
+class CodexImageGenerationUnsupportedError(RuntimeError):
+    """The active Codex account cannot use the hosted image tool."""
+
+
+_IMAGE_GENERATION_UNAVAILABLE_MESSAGE = (
+    "Image generation is not enabled for the current Codex account. "
+    "Switch the image provider to OpenAI API key, FAL, or xAI."
+)
+
+
+def _is_image_generation_unsupported_error(status_code: int, body: str) -> bool:
+    """Match only Codex's account-capability rejection for the image tool."""
+    if status_code != 400:
+        return False
+    normalized = " ".join((body or "").lower().split())
+    return "tool choice 'image_generation' not found in 'tools' parameter" in normalized
+
+
 # ---------------------------------------------------------------------------
 # Model catalog — mirrors the ``openai`` plugin so the picker UX is identical.
 # ---------------------------------------------------------------------------
@@ -394,6 +412,11 @@ def _collect_image_b64(
             except httpx.HTTPStatusError as exc:
                 exc.response.read()
                 body = exc.response.text[:500]
+                if _is_image_generation_unsupported_error(
+                    exc.response.status_code,
+                    body,
+                ):
+                    raise CodexImageGenerationUnsupportedError(body) from exc
                 raise RuntimeError(
                     f"Codex Responses API returned HTTP {exc.response.status_code}: {body}"
                 ) from exc
@@ -542,6 +565,19 @@ class OpenAICodexImageGenProvider(ImageGenProvider):
                 quality=meta["quality"],
                 input_images=input_images or None,
             )
+        except CodexImageGenerationUnsupportedError:
+            logger.debug(
+                "Codex account does not expose image generation",
+                exc_info=True,
+            )
+            return error_response(
+                error=_IMAGE_GENERATION_UNAVAILABLE_MESSAGE,
+                error_type="capability_unsupported",
+                provider="openai-codex",
+                model=tier_id,
+                prompt=prompt,
+                aspect_ratio=aspect,
+            )
         except Exception as exc:
             logger.debug("Codex image generation failed", exc_info=True)
             return error_response(

tests/plugins/image_gen/test_openai_codex_provider.py

@@ -307,6 +307,47 @@ class TestGenerate:
         assert result["error_type"] == "api_error"
         assert "cloudflare 403" in result["error"]
 
+    def test_unsupported_image_tool_returns_capability_error(self, provider, monkeypatch):
+        monkeypatch.setattr(codex_plugin, "_read_codex_access_token", lambda: "codex-token")
+
+        def _unsupported(*args, **kwargs):
+            raise codex_plugin.CodexImageGenerationUnsupportedError(
+                "Tool choice 'image_generation' not found in 'tools' parameter."
+            )
+
+        monkeypatch.setattr(codex_plugin, "_collect_image_b64", _unsupported)
+
+        result = provider.generate("a cat")
+
+        assert result["success"] is False
+        assert result["error_type"] == "capability_unsupported"
+        assert "current Codex account" in result["error"]
+        assert "OpenAI API key, FAL, or xAI" in result["error"]
+
+
+class TestCapabilityErrorDetection:
+    @pytest.mark.parametrize(
+        "body",
+        [
+            "Tool choice 'image_generation' not found in 'tools' parameter.",
+            '{"error":{"message":"Tool choice \'image_generation\' not found in \'tools\' parameter."}}',
+        ],
+    )
+    def test_detects_exact_codex_image_tool_rejection(self, body):
+        assert codex_plugin._is_image_generation_unsupported_error(400, body) is True
+
+    @pytest.mark.parametrize(
+        ("status_code", "body"),
+        [
+            (401, "Tool choice 'image_generation' not found in 'tools' parameter."),
+            (400, "Tool choice 'web_search' not found in 'tools' parameter."),
+            (400, "The image_generation request was rejected by moderation."),
+            (500, "Tool choice 'image_generation' not found in 'tools' parameter."),
+        ],
+    )
+    def test_does_not_misclassify_other_failures(self, status_code, body):
+        assert codex_plugin._is_image_generation_unsupported_error(status_code, body) is False
+
 
 # ── Plugin entry point ──────────────────────────────────────────────────────