diff --git a/studio/backend/core/export/worker.py b/studio/backend/core/export/worker.py
index 5d54f75d8f..a581813221 100644
--- a/studio/backend/core/export/worker.py
+++ b/studio/backend/core/export/worker.py
@@ -47,18 +47,22 @@ def _activate_transformers_version(model_name: str, project_root: str) -> None:
             logger.warning(".venv_t5 not found at %s — installing at runtime", venv_t5)
             import subprocess as sp
             os.makedirs(venv_t5, exist_ok=True)
-            sp.run(
+            r1 = sp.run(
                 [sys.executable, "-m", "pip", "install", "--target", venv_t5,
                  "--no-deps", "transformers==5.1.0"],
                 stdout=sp.PIPE, stderr=sp.STDOUT,
             )
-            sp.run(
+            r2 = sp.run(
                 [sys.executable, "-m", "pip", "install", "--target", venv_t5,
                  "--no-deps", "huggingface_hub==1.3.0"],
                 stdout=sp.PIPE, stderr=sp.STDOUT,
             )
-            if os.path.isdir(venv_t5):
-                sys.path.insert(0, venv_t5)
+            if r1.returncode != 0 or r2.returncode != 0:
+                raise RuntimeError(
+                    f"Failed to install transformers 5.x into {venv_t5}. "
+                    f"pip returncode: transformers={r1.returncode}, huggingface_hub={r2.returncode}"
+                )
+            sys.path.insert(0, venv_t5)
     else:
         logger.info("Using default transformers (4.57.x) for %s", model_name)
 
diff --git a/studio/backend/core/inference/worker.py b/studio/backend/core/inference/worker.py
index cac5dacd6e..99ead90f9c 100644
--- a/studio/backend/core/inference/worker.py
+++ b/studio/backend/core/inference/worker.py
@@ -49,18 +49,22 @@ def _activate_transformers_version(model_name: str, project_root: str) -> None:
             logger.warning(".venv_t5 not found at %s — installing at runtime", venv_t5)
             import subprocess as sp
             os.makedirs(venv_t5, exist_ok=True)
-            sp.run(
+            r1 = sp.run(
                 [sys.executable, "-m", "pip", "install", "--target", venv_t5,
                  "--no-deps", "transformers==5.1.0"],
                 stdout=sp.PIPE, stderr=sp.STDOUT,
             )
-            sp.run(
+            r2 = sp.run(
                 [sys.executable, "-m", "pip", "install", "--target", venv_t5,
                  "--no-deps", "huggingface_hub==1.3.0"],
                 stdout=sp.PIPE, stderr=sp.STDOUT,
             )
-            if os.path.isdir(venv_t5):
-                sys.path.insert(0, venv_t5)
+            if r1.returncode != 0 or r2.returncode != 0:
+                raise RuntimeError(
+                    f"Failed to install transformers 5.x into {venv_t5}. "
+                    f"pip returncode: transformers={r1.returncode}, huggingface_hub={r2.returncode}"
+                )
+            sys.path.insert(0, venv_t5)
     else:
         logger.info("Using default transformers (4.57.x) for %s", model_name)
 
diff --git a/studio/backend/core/training/worker.py b/studio/backend/core/training/worker.py
index c937b3f110..1ed6b00131 100644
--- a/studio/backend/core/training/worker.py
+++ b/studio/backend/core/training/worker.py
@@ -44,18 +44,22 @@ def _activate_transformers_version(model_name: str, project_root: str) -> None:
             logger.warning(".venv_t5 not found at %s — installing at runtime", venv_t5)
             import subprocess as sp
             os.makedirs(venv_t5, exist_ok=True)
-            sp.run(
+            r1 = sp.run(
                 [sys.executable, "-m", "pip", "install", "--target", venv_t5,
                  "--no-deps", "transformers==5.1.0"],
                 stdout=sp.PIPE, stderr=sp.STDOUT,
             )
-            sp.run(
+            r2 = sp.run(
                 [sys.executable, "-m", "pip", "install", "--target", venv_t5,
                  "--no-deps", "huggingface_hub==1.3.0"],
                 stdout=sp.PIPE, stderr=sp.STDOUT,
             )
-            if os.path.isdir(venv_t5):
-                sys.path.insert(0, venv_t5)
+            if r1.returncode != 0 or r2.returncode != 0:
+                raise RuntimeError(
+                    f"Failed to install transformers 5.x into {venv_t5}. "
+                    f"pip returncode: transformers={r1.returncode}, huggingface_hub={r2.returncode}"
+                )
+            sys.path.insert(0, venv_t5)
     else:
         logger.info("Using default transformers (4.57.x) for %s", model_name)