fix: imagegen MCP env 必须写死本地网关 base URL

首轮生产验收失败根因：_prepare_tenant 只把 IMAGE_GEN_* 透传
进 MCP env，没写 IMAGE_GEN_BASE_URL，也没带 SUB2API_BASE_URL，
于是 imagegen.py 回落到公网 sub2.diante.me，而它不在
Tinyproxy 白名单里，API 调用 403 Filtered。
修法：worker 在写 MCP env 前用 imagegen.build_mcp_env 算好
base（显式 IMAGE_GEN_BASE_URL > SUB2API_BASE_URL），并把
网关 host 加进 NO_PROXY；组装逻辑抽成可单测 helper，新增
2 项回归测试（本地网关解析、显式 base 优先）。

cloud/imagegen.py

@@ -306,3 +306,36 @@ def ensure_imagegen_mcp_env(codex_home_dir, env):
         return True
     except Exception:
         return False
+
+
+def build_mcp_env(worker_environ, proxy_env=None):
+    """Build the [mcp_servers.imagegen.env] dict from worker env.
+
+    The MCP process only sees config.toml env, never the worker's
+    own env, so IMAGE_GEN_BASE_URL must be resolved HERE (worker
+    IMAGE_GEN_BASE_URL, else SUB2API_BASE_URL, else absent and
+    imagegen.py falls back to the public relay domain -- which is
+    NOT on the Tinyproxy whitelist, so a missing base here caused
+    a 403 Filtered in the first production verification, 2026-10-30).
+    proxy_env supplies HTTP(S)_PROXY for downloading the returned
+    image URL; NO_PROXY gains the gateway host for direct API calls.
+    Never injects the task user's gateway key.
+    """
+    env = dict(proxy_env) if proxy_env else {}
+    for key in ("IMAGE_GEN_BASE_URL", "IMAGE_GEN_API_KEY",
+                "IMAGE_GEN_MODEL"):
+        if worker_environ.get(key):
+            env[key] = worker_environ[key]
+    base = (worker_environ.get("IMAGE_GEN_BASE_URL", "")
+            or worker_environ.get("SUB2API_BASE_URL", ""))
+    if base:
+        env["IMAGE_GEN_BASE_URL"] = base
+    host = base.split("://", 1)[-1].split("/", 1)[0]
+    host = host.split(":", 1)[0]
+    parts = [p for p in env.get("NO_PROXY", "").split(",") if p]
+    for item in ("localhost", "127.0.0.1", host):
+        if item and item not in parts:
+            parts.append(item)
+    env["NO_PROXY"] = ",".join(parts)
+    env["no_proxy"] = ",".join(parts)
+    return env

cloud/tests/test_imagegen.py

@@ -108,6 +108,31 @@ class ImageGenTests(unittest.TestCase):
                                           "arguments": {}}})
         self.assertEqual(resp["error"]["code"], -32602)
 
+    def test_build_mcp_env_resolves_local_gateway_base(self):
+        # Regression: first production verification failed 403
+        # Filtered because MCP env had no base URL and imagegen.py
+        # fell back to the public relay domain, which is not on
+        # the Tinyproxy whitelist. The local gateway origin must
+        # be resolved here and land in NO_PROXY.
+        env = imagegen.build_mcp_env(
+            {"SUB2API_BASE_URL": "http://172.17.0.1:28084",
+             "IMAGE_GEN_API_KEY": "k"},
+            {"HTTP_PROXY": "http://10.20.20.1:8888",
+             "NO_PROXY": "localhost,127.0.0.1"})
+        self.assertEqual(env["IMAGE_GEN_BASE_URL"],
+                         "http://172.17.0.1:28084")
+        self.assertIn("172.17.0.1", env["NO_PROXY"])
+        self.assertEqual(env["IMAGE_GEN_API_KEY"], "k")
+        self.assertNotIn("SUB2API_API_KEY", env)
+
+    def test_build_mcp_env_explicit_base_wins(self):
+        env = imagegen.build_mcp_env(
+            {"IMAGE_GEN_BASE_URL": "https://relay.example",
+             "SUB2API_BASE_URL": "http://172.17.0.1:28084"})
+        self.assertEqual(env["IMAGE_GEN_BASE_URL"],
+                         "https://relay.example")
+        self.assertIn("relay.example", env["NO_PROXY"])
+
     def test_ensure_home_seeds_and_env(self):
         home = os.path.join(self._tmp.name, "home")
         os.makedirs(home)

cloud/worker.py

@@ -2906,22 +2906,16 @@ class Worker:
             # 未配 IMAGE_GEN_API_KEY 时仍写 base/model，工具会
             # 明确报“未配置”；绝不把任务自己的分组 2 key 塞进来。
             try:
-                imagegen_env = dict(proxy_env) if proxy_env else {}
-                for key in ("IMAGE_GEN_BASE_URL", "IMAGE_GEN_API_KEY",
-                            "IMAGE_GEN_MODEL"):
-                    if os.environ.get(key):
-                        imagegen_env[key] = os.environ[key]
-                base = (os.environ.get("IMAGE_GEN_BASE_URL", "")
-                        or os.environ.get("SUB2API_BASE_URL", ""))
-                host = base.split("://", 1)[-1].split("/", 1)[0]
-                host = host.split(":", 1)[0]
-                no_proxy = imagegen_env.get("NO_PROXY", "")
-                parts = [p for p in no_proxy.split(",") if p]
-                for item in ("localhost", "127.0.0.1", host):
-                    if item and item not in parts:
-                        parts.append(item)
-                imagegen_env["NO_PROXY"] = ",".join(parts)
-                imagegen_env["no_proxy"] = ",".join(parts)
+                # env 组装在 imagegen.build_mcp_env 里（可单测）：
+                # base 必须在这里算好写进 MCP env，MCP 进程只读
+                # config.toml 里的 env，看不到 worker 的
+                # SUB2API_BASE_URL；不写的话 imagegen.py 会回落
+                # 到公网 sub2.diante.me，而它不在 Tinyproxy
+                # 白名单里，实测 403 Filtered（2026-10-30 首轮
+                # 生产验收即因此失败）。本地网关 origin 优先，
+                # 因为它走 NO_PROXY 直连，不依赖白名单。
+                from cloud.imagegen import build_mcp_env as _build_mcp_env
+                imagegen_env = _build_mcp_env(os.environ, proxy_env)
                 home = self._tenant_dirs(
                     task.get("project_id"))["codex_home"]
                 _ensure_imagegen_mcp_env(home, imagegen_env)