diff --git a/.env.example b/.env.example
index 22206cd..584102d 100644
--- a/.env.example
+++ b/.env.example
@@ -3,6 +3,7 @@ SEG_DATA_SERVER_ROOT=.
 SEG_BACKEND_DB=var/seg_data_server.sqlite3
 SEG_BACKEND_LOG_DIR=var/job_logs
 SEG_TASK_CONDA_ENV=seg_smp
+SEG_MMSEG_CONDA_ENV=seg_mmcv
 SEG_BACKEND_CONDA_ENV=seg_smp
 SEG_WEIGHT_MODE=copy
 SEG_ENABLE_SHELL_TASKS=1
diff --git a/README.md b/README.md
index bea7031..667e837 100644
--- a/README.md
+++ b/README.md
@@ -27,8 +27,9 @@ Seg_Data_Server_Net/
 cd Seg_Data_Server_Net
 cp .env.example .env
 
-# Backend. The deployment env is seg_smp so the API and task wrappers share
-# the same segmentation dependency stack.
+# Backend. The deployment env is seg_smp so the API and most task wrappers
+# share the same segmentation dependency stack. MMSeg jobs default to the
+# separate SEG_MMSEG_CONDA_ENV because full mmcv wheels must match torch/CUDA.
 conda run -n seg_smp uvicorn app.main:app --app-dir backend --host 0.0.0.0 --port 8010
 
 # Frontend.
@@ -57,12 +58,23 @@ artifact API, runs a mock job, checks SSE log streaming, and executes one
 legacy image/label overlay job on tiny generated PNGs. It also runs model
 family readiness checks: a SegModel/SMP forward pass, a YOLO segmentation
 prediction on a tiny image, MMSeg config parsing, and local MMSeg pretrained
-weight discovery.
+weight discovery. MMSeg full-model readiness is validated in
+`SEG_MMSEG_CONDA_ENV` by importing `mmcv._ext` and building a local MMSeg
+`EncoderDecoder` from the existing config tree.
 
 Current `seg_smp` uses `mmcv-lite` because no `torch 2.6/cu124` full `mmcv`
 wheel is available on this machine and `nvcc` is not installed for source
-builds. The acceptance smoke reports MMSeg full model construction as a
-warning until a full `mmcv` build with `mmcv._ext` is installed.
+builds. A dedicated `seg_mmcv` environment is used for MMSeg tasks and has
+`torch 2.1.2+cu121`, `mmcv 2.1.0`, `mmsegmentation 1.2.2`, and NumPy 1.26.
+If rebuilding the environment, keep these versions aligned:
+
+```bash
+conda create -n seg_mmcv python=3.10 -y
+conda run -n seg_mmcv python -m pip install -U pip
+conda run -n seg_mmcv python -m pip install torch==2.1.2 torchvision==0.16.2 --index-url https://download.pytorch.org/whl/cu121
+conda run -n seg_mmcv python -m pip install mmengine==0.10.7 mmsegmentation==1.2.2 'mmcv==2.1.0' -f https://download.openmmlab.com/mmcv/dist/cu121/torch2.1/index.html
+conda run -n seg_mmcv python -m pip install 'numpy<2' 'opencv-python<4.12' ftfy regex matplotlib pandas scikit-learn scipy seaborn tqdm tensorboard
+```
 
 ## Weight Sync
 
@@ -118,7 +130,8 @@ Run the local evaluation and validation agents before publishing changes:
 PYTHONPATH=backend conda run -n seg_smp python scripts/run_agents.py --build
 ```
 
-The validation agent checks catalog coverage, the new `seg_smp` env, GPU
-visibility, no-weight Git safety, backend tests, frontend build, and live
-backend/frontend endpoints when the services are running. With live validation
-enabled it also runs the lightweight acceptance smoke above.
+The validation agent checks catalog coverage, the `seg_smp` task env, the
+`seg_mmcv` MMSeg env, GPU visibility, no-weight Git safety, backend tests,
+frontend build, and live backend/frontend endpoints when the services are
+running. With live validation enabled it also runs the lightweight acceptance
+smoke above.
diff --git a/backend/app/acceptance.py b/backend/app/acceptance.py
index 0eba587..44c0a57 100644
--- a/backend/app/acceptance.py
+++ b/backend/app/acceptance.py
@@ -13,20 +13,53 @@ from typing import Any
 from .config import settings
 
 
+def _run_command(command: list[str], cwd: Path | None = None, timeout: int = 60) -> dict[str, Any]:
+    try:
+        result = subprocess.run(
+            command,
+            cwd=str(cwd or settings.project_root),
+            capture_output=True,
+            text=True,
+            timeout=timeout,
+        )
+        return {
+            "passed": result.returncode == 0,
+            "returncode": result.returncode,
+            "stdout": result.stdout[-4000:],
+            "stderr": result.stderr[-4000:],
+        }
+    except subprocess.TimeoutExpired as exc:
+        return {
+            "passed": False,
+            "returncode": None,
+            "stdout": (exc.stdout or "")[-4000:] if isinstance(exc.stdout, str) else "",
+            "stderr": (exc.stderr or "")[-4000:] if isinstance(exc.stderr, str) else "",
+            "error": f"command timed out after {timeout}s",
+        }
+    except Exception as exc:
+        return {"passed": False, "returncode": None, "stdout": "", "stderr": "", "error": str(exc)}
+
+
 def _run_snippet(code: str, cwd: Path | None = None, timeout: int = 60) -> dict[str, Any]:
-    result = subprocess.run(
-        [sys.executable, "-c", code],
-        cwd=str(cwd or settings.project_root),
-        capture_output=True,
-        text=True,
-        timeout=timeout,
-    )
-    return {
-        "passed": result.returncode == 0,
-        "returncode": result.returncode,
-        "stdout": result.stdout[-4000:],
-        "stderr": result.stderr[-4000:],
-    }
+    return _run_command([sys.executable, "-c", code], cwd=cwd, timeout=timeout)
+
+
+def _run_conda_snippet(env_name: str, code: str, cwd: Path | None = None, timeout: int = 60) -> dict[str, Any]:
+    detail = _run_command(["conda", "run", "-n", env_name, "python", "-c", code], cwd=cwd, timeout=timeout)
+    detail["env"] = env_name
+    return detail
+
+
+MMSEG_FULL_BUILD_SNIPPET = (
+    "from mmseg.utils import register_all_modules; "
+    "register_all_modules(init_default_scope=True); "
+    "from mmengine.config import Config; "
+    "from mmseg.registry import MODELS; "
+    "import mmcv._ext; "
+    "cfg=Config.fromfile({config_path!r}); "
+    "model=MODELS.build(cfg.model); "
+    "print(type(model).__name__)"
+)
 
 
 def _request_json(method: str, url: str, payload: dict[str, Any] | None = None, timeout: int = 10) -> dict[str, Any]:
@@ -182,13 +215,23 @@ def run_model_family_readiness() -> dict[str, Any]:
             "required": True,
             "detail": {"passed": mmseg_pretrained.exists(), "path": str(mmseg_pretrained), "size": mmseg_pretrained.stat().st_size if mmseg_pretrained.exists() else 0},
         },
+        {
+            "name": "mmseg_full_env_imports",
+            "required": True,
+            "detail": _run_conda_snippet(
+                settings.mmseg_conda_env,
+                "import torch, cv2, mmcv, mmengine, mmseg; "
+                "import mmcv._ext; "
+                "print(torch.__version__, torch.version.cuda, cv2.__version__, mmcv.__version__, mmseg.__version__)",
+                timeout=90,
+            ),
+        },
         {
             "name": "mmseg_full_model_build",
-            "required": False,
-            "detail": _run_snippet(
-                "from mmengine.config import Config; from mmseg.registry import MODELS; "
-                f"cfg=Config.fromfile({str(mmseg_config)!r}); "
-                "model=MODELS.build(cfg.model); print(type(model).__name__)",
+            "required": True,
+            "detail": _run_conda_snippet(
+                settings.mmseg_conda_env,
+                MMSEG_FULL_BUILD_SNIPPET.format(config_path=str(mmseg_config)),
                 timeout=90,
             ),
         },
diff --git a/backend/app/agents/validation_agent.py b/backend/app/agents/validation_agent.py
index 6db2363..304bef8 100644
--- a/backend/app/agents/validation_agent.py
+++ b/backend/app/agents/validation_agent.py
@@ -55,21 +55,36 @@ def validate_project(run_build: bool = False) -> dict:
     checks.append({"name": "weights_manifest_present", "passed": manifest.get("count", 0) >= 1})
     checks.append({"name": "gpus_query", "passed": bool(get_gpus().get("available"))})
     env_names = [item["name"] for item in get_conda_envs().get("envs", [])]
-    checks.append({"name": "seg_smp_env_exists", "passed": "seg_smp" in env_names})
+    checks.append({"name": "task_env_exists", "passed": settings.task_conda_env in env_names, "detail": {"env": settings.task_conda_env}})
+    checks.append({"name": "mmseg_env_exists", "passed": settings.mmseg_conda_env in env_names, "detail": {"env": settings.mmseg_conda_env}})
 
     smoke = _run(
         [
             "conda",
             "run",
             "-n",
-            "seg_smp",
+            settings.task_conda_env,
             "python",
             "-c",
             "import fastapi, uvicorn, torch, cv2, segmentation_models_pytorch, ultralytics, albumentations, mmengine, mmseg, mmcv; print(torch.__version__, torch.cuda.is_available())",
         ],
         cwd=settings.project_root,
     )
-    checks.append({"name": "seg_smp_backend_smoke", "passed": smoke["passed"], "detail": smoke})
+    checks.append({"name": "task_env_backend_smoke", "passed": smoke["passed"], "detail": smoke})
+
+    mmseg_smoke = _run(
+        [
+            "conda",
+            "run",
+            "-n",
+            settings.mmseg_conda_env,
+            "python",
+            "-c",
+            "import torch, cv2, mmcv, mmengine, mmseg; import mmcv._ext; print(torch.__version__, torch.version.cuda, cv2.__version__, mmcv.__version__, mmseg.__version__)",
+        ],
+        cwd=settings.project_root,
+    )
+    checks.append({"name": "mmseg_env_full_mmcv_smoke", "passed": mmseg_smoke["passed"], "detail": mmseg_smoke})
 
     no_weight = _run(["bash", "scripts/check_no_weight_git.sh"], cwd=settings.project_root)
     checks.append({"name": "no_weight_in_git", "passed": no_weight["passed"], "detail": no_weight})
diff --git a/backend/app/config.py b/backend/app/config.py
index bec87f7..3ffbd9c 100644
--- a/backend/app/config.py
+++ b/backend/app/config.py
@@ -20,6 +20,7 @@ class Settings:
     log_dir: Path
     weights_root: Path
     task_conda_env: str
+    mmseg_conda_env: str
     backend_conda_env: str
     weight_mode: str
     enable_shell_tasks: bool
@@ -46,6 +47,7 @@ def get_settings() -> Settings:
         log_dir=log_dir,
         weights_root=weights_root,
         task_conda_env=os.getenv("SEG_TASK_CONDA_ENV", "seg_smp"),
+        mmseg_conda_env=os.getenv("SEG_MMSEG_CONDA_ENV", "seg_mmcv"),
         backend_conda_env=os.getenv("SEG_BACKEND_CONDA_ENV", "seg_smp"),
         weight_mode=os.getenv("SEG_WEIGHT_MODE", "copy"),
         enable_shell_tasks=os.getenv("SEG_ENABLE_SHELL_TASKS", "1") == "1",
diff --git a/backend/app/coverage.py b/backend/app/coverage.py
index b20a4ac..4956e87 100644
--- a/backend/app/coverage.py
+++ b/backend/app/coverage.py
@@ -157,7 +157,8 @@ def build_task_checks() -> list[dict[str, Any]]:
     for task in TASK_TYPES:
         params = TASK_DEFAULTS.get(task, {})
         try:
-            spec = build_module_task(task, dict(params), settings.task_conda_env)
+            conda_env = settings.mmseg_conda_env if task.startswith("mmseg.") else settings.task_conda_env
+            spec = build_module_task(task, dict(params), conda_env)
             script_path = _command_script_path(spec.command) if spec else None
             checks.append(
                 {
diff --git a/backend/app/jobs.py b/backend/app/jobs.py
index 68b6e9d..1e6d1e8 100644
--- a/backend/app/jobs.py
+++ b/backend/app/jobs.py
@@ -17,8 +17,14 @@ _running: dict[str, subprocess.Popen] = {}
 _lock = threading.Lock()
 
 
+def default_conda_env_for_job(job_type: str) -> str:
+    if job_type.startswith("mmseg."):
+        return settings.mmseg_conda_env
+    return settings.task_conda_env
+
+
 def _build_task(request: JobCreate) -> CommandSpec:
-    conda_env = request.conda_env or settings.task_conda_env
+    conda_env = request.conda_env or default_conda_env_for_job(request.type)
     spec = build_module_task(request.type, request.params, conda_env)
     if spec is None:
         raise ValueError(f"unsupported job type: {request.type}")
@@ -113,4 +119,3 @@ def cancel_job(job_id: str) -> dict | None:
         except ProcessLookupError:
             pass
     return db.get_job(job_id)
-
diff --git a/backend/app/modules/system/service.py b/backend/app/modules/system/service.py
index 7c981b2..008e157 100644
--- a/backend/app/modules/system/service.py
+++ b/backend/app/modules/system/service.py
@@ -60,7 +60,7 @@ def get_conda_envs() -> dict:
         parts = raw.replace("*", " ").split()
         if len(parts) >= 2:
             envs.append({"name": parts[0], "path": parts[-1], "active": marker})
-    return {"available": True, "envs": envs, "task_default": settings.task_conda_env}
+    return {"available": True, "envs": envs, "task_default": settings.task_conda_env, "mmseg_default": settings.mmseg_conda_env}
 
 
 def disk_usage() -> dict:
@@ -103,4 +103,3 @@ def scan_results() -> list[dict]:
                     continue
     results.sort(key=lambda item: item["modified"], reverse=True)
     return results[:1000]
-
diff --git a/backend/tests/test_artifacts.py b/backend/tests/test_artifacts.py
index 28e0483..bb77d11 100644
--- a/backend/tests/test_artifacts.py
+++ b/backend/tests/test_artifacts.py
@@ -23,6 +23,7 @@ def test_project_var_artifact_path_is_served(tmp_path, monkeypatch):
         log_dir=original.log_dir,
         weights_root=original.weights_root,
         task_conda_env=original.task_conda_env,
+        mmseg_conda_env=original.mmseg_conda_env,
         backend_conda_env=original.backend_conda_env,
         weight_mode=original.weight_mode,
         enable_shell_tasks=original.enable_shell_tasks,
diff --git a/backend/tests/test_jobs.py b/backend/tests/test_jobs.py
new file mode 100644
index 0000000..f30c4e3
--- /dev/null
+++ b/backend/tests/test_jobs.py
@@ -0,0 +1,6 @@
+from app.jobs import default_conda_env_for_job
+
+
+def test_mmseg_jobs_use_mmseg_conda_env_by_default():
+    assert default_conda_env_for_job("mmseg.train") == "seg_mmcv"
+    assert default_conda_env_for_job("segmodel.train") == "seg_smp"