diff --git a/.changeset/tolerate-non-numeric-step.md b/.changeset/tolerate-non-numeric-step.md
new file mode 100644
index 0000000000..80ee3ccb96
--- /dev/null
+++ b/.changeset/tolerate-non-numeric-step.md
@@ -0,0 +1,5 @@
+---
+"@e2b/python-sdk": patch
+---
+
+fix(python-sdk): don't crash the build error path on a non-numeric reason.step
diff --git a/packages/python-sdk/e2b/template/utils.py b/packages/python-sdk/e2b/template/utils.py
index b61101b307..45979cda1d 100644
--- a/packages/python-sdk/e2b/template/utils.py
+++ b/packages/python-sdk/e2b/template/utils.py
@@ -406,7 +406,7 @@ def pad_octal(mode: int) -> str:
     return f"{mode:04o}"
 
 
-def get_build_step_index(step: str, stack_traces_length: int) -> int:
+def get_build_step_index(step: str, stack_traces_length: int) -> Optional[int]:
     """
     Get the array index for a build step based on its name.
 
@@ -414,11 +414,12 @@ def get_build_step_index(step: str, stack_traces_length: int) -> int:
     - BASE_STEP_NAME: Returns 0 (first step)
     - FINALIZE_STEP_NAME: Returns the last index
     - Numeric strings: Converted to number
+    - Anything else: None (no matching local stack trace)
 
     :param step: Build step name or number as string
     :param stack_traces_length: Total number of stack traces (used for FINALIZE_STEP_NAME)
 
-    :return: Index for the build step
+    :return: Index for the build step, or None if the step has no usable index
     """
     if step == BASE_STEP_NAME:
         return 0
@@ -426,7 +427,10 @@ def get_build_step_index(step: str, stack_traces_length: int) -> int:
     if step == FINALIZE_STEP_NAME:
         return stack_traces_length - 1
 
-    return int(step)
+    try:
+        return int(step)
+    except ValueError:
+        return None
 
 
 def read_gcp_service_account_json(
diff --git a/packages/python-sdk/e2b/template_async/build_api.py b/packages/python-sdk/e2b/template_async/build_api.py
index 9a822cd516..3b9445f482 100644
--- a/packages/python-sdk/e2b/template_async/build_api.py
+++ b/packages/python-sdk/e2b/template_async/build_api.py
@@ -299,7 +299,7 @@ async def poll_status() -> TemplateBuildStatusResponse:
                 step_index = get_build_step_index(
                     build_status.reason.step, len(stack_traces)
                 )
-                if step_index < len(stack_traces):
+                if step_index is not None and 0 <= step_index < len(stack_traces):
                     traceback = stack_traces[step_index]
 
             raise BuildException(
diff --git a/packages/python-sdk/e2b/template_sync/build_api.py b/packages/python-sdk/e2b/template_sync/build_api.py
index 2bc918ab2f..4d5d7bd656 100644
--- a/packages/python-sdk/e2b/template_sync/build_api.py
+++ b/packages/python-sdk/e2b/template_sync/build_api.py
@@ -289,7 +289,7 @@ def poll_status() -> TemplateBuildStatusResponse:
                 step_index = get_build_step_index(
                     build_status.reason.step, len(stack_traces)
                 )
-                if step_index < len(stack_traces):
+                if step_index is not None and 0 <= step_index < len(stack_traces):
                     traceback = stack_traces[step_index]
 
             raise BuildException(
diff --git a/packages/python-sdk/tests/test_build_step_index.py b/packages/python-sdk/tests/test_build_step_index.py
new file mode 100644
index 0000000000..926084947a
--- /dev/null
+++ b/packages/python-sdk/tests/test_build_step_index.py
@@ -0,0 +1,21 @@
+from e2b.template.consts import BASE_STEP_NAME, FINALIZE_STEP_NAME
+from e2b.template.utils import get_build_step_index
+
+
+def test_base_maps_to_first():
+    assert get_build_step_index(BASE_STEP_NAME, 5) == 0
+
+
+def test_finalize_maps_to_last():
+    assert get_build_step_index(FINALIZE_STEP_NAME, 5) == 4
+
+
+def test_numeric_string_maps_to_index():
+    assert get_build_step_index("3", 5) == 3
+
+
+def test_non_numeric_step_returns_none():
+    # e2b Cloud itself reports "optimize" / "resize-disk" for those phases.
+    # None means "no matching local stack trace", not an error.
+    assert get_build_step_index("optimize", 5) is None
+    assert get_build_step_index("RUN apt-get update", 5) is None