From 6f8d4c1bfc75c3cbc467f981b64d2ac1d222128e Mon Sep 17 00:00:00 2001
From: "sentry-junior[bot]"
 <264270552+sentry-junior[bot]@users.noreply.github.com>
Date: Tue, 3 Nov 2026 00:05:05 +0000
Subject: [PATCH] fix(sourcemaps): ignore non-string sourcemap headers

---
 src/sentry/api/endpoints/source_map_debug.py        | 5 +++--
 tests/sentry/api/endpoints/test_source_map_debug.py | 8 ++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/sentry/api/endpoints/source_map_debug.py b/src/sentry/api/endpoints/source_map_debug.py
index 5c0d4366d101..7a649eeebb5e 100644
--- a/src/sentry/api/endpoints/source_map_debug.py
+++ b/src/sentry/api/endpoints/source_map_debug.py
@@ -1,6 +1,6 @@
 import logging
 from collections.abc import Iterable, Mapping, Sequence
-from typing import Any, Literal, NamedTuple, TypedDict, cast
+from typing import Any, Literal, NamedTuple, TypedDict
 
 import sentry_sdk
 from django.db.models import Exists, OuterRef
@@ -47,7 +47,8 @@
 
 
 def _sourcemap_header(headers: Mapping[str, object]) -> str | None:
-    return cast("str | None", headers.get("sourcemap", headers.get("x-sourcemap")))
+    value = headers.get("sourcemap", headers.get("x-sourcemap"))
+    return value if isinstance(value, str) else None
 
 
 from sentry.utils.urls import non_standard_url_join
diff --git a/tests/sentry/api/endpoints/test_source_map_debug.py b/tests/sentry/api/endpoints/test_source_map_debug.py
index d368179749d5..b3b0eceb5f84 100644
--- a/tests/sentry/api/endpoints/test_source_map_debug.py
+++ b/tests/sentry/api/endpoints/test_source_map_debug.py
@@ -15,6 +15,7 @@
     MIN_JS_SDK_VERSION_FOR_DEBUG_IDS,
     ReleaseBundleUrls,
     SourceMapReleaseProcessResult,
+    _sourcemap_header,
     get_release_bundle_urls,
     report_unsuccessful_url_matches,
 )
@@ -34,6 +35,13 @@
 from sentry.testutils.helpers.options import override_options
 from sentry.testutils.skips import requires_snuba
 
+
+def test_sourcemap_header_ignores_non_strings() -> None:
+    assert _sourcemap_header({"sourcemap": "foo"}) == "foo"
+    assert _sourcemap_header({"x-sourcemap": "bar"}) == "bar"
+    assert _sourcemap_header({"sourcemap": 1}) is None
+
+
 pytestmark = [requires_snuba]