diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1a708e499..0dba932cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@
 - Add cache keep modes, including `SENTRY_CACHE_KEEP_ALWAYS` to cache envelopes regardless of upload result. ([#1707](https://github.com/getsentry/sentry-native/pull/1707))
 - Crashpad: add error log for oversized envelopes (HTTP 413 Content Too Large). ([#1706](https://github.com/getsentry/sentry-native/pull/1706), [crashpad#155](https://github.com/getsentry/crashpad/pull/155))
 - Crashpad: support modifying attachments after `sentry_init` on macOS. ([#1705](https://github.com/getsentry/sentry-native/pull/1705), [crashpad#153](https://github.com/getsentry/crashpad/pull/153))
+- Add `cache_dir` envelope header for external crash reporters. ([#1698](https://github.com/getsentry/sentry-native/pull/1698))
 
 **Fixes**:
 
diff --git a/src/backends/native/sentry_crash_daemon.c b/src/backends/native/sentry_crash_daemon.c
index 8d4d75026..7e702f17f 100644
--- a/src/backends/native/sentry_crash_daemon.c
+++ b/src/backends/native/sentry_crash_daemon.c
@@ -3036,6 +3036,11 @@ sentry__process_crash(const sentry_options_t *options, sentry_crash_ipc_t *ipc)
 
     SENTRY_DEBUG("Envelope loaded, capturing");
 
+    if (options->cache_keep && options->external_crash_reporter
+        && !sentry__envelope_materialize(envelope)) {
+        SENTRY_WARN("Failed to materialize envelope for external crash report");
+    }
+
     // Capture directly, or pass to external crash reporter
     if (!sentry__launch_external_crash_reporter(options, envelope)) {
         if (has_attachment_refs && options && options->run) {
diff --git a/src/backends/sentry_backend_crashpad.cpp b/src/backends/sentry_backend_crashpad.cpp
index 1d5d9f35f..5e2b9c318 100644
--- a/src/backends/sentry_backend_crashpad.cpp
+++ b/src/backends/sentry_backend_crashpad.cpp
@@ -253,6 +253,10 @@ flush_external_crash_report(
         sentry__envelope_add_session(envelope, options->session);
     }
 
+    if (options->cache_keep) {
+        sentry__envelope_set_header(envelope, "cache_dir",
+            sentry_value_new_string(options->run->cache_path->path));
+    }
     sentry__run_write_external(options->run, envelope);
     sentry_envelope_free(envelope);
 }
diff --git a/src/sentry_core.c b/src/sentry_core.c
index fdd1aa10d..815aa2b71 100644
--- a/src/sentry_core.c
+++ b/src/sentry_core.c
@@ -1709,6 +1709,14 @@ sentry__launch_external_crash_reporter(
         sentry_free(envelope_filename);
         return false;
     }
+    if (options->cache_keep) {
+        if (!sentry__envelope_is_raw(envelope)) {
+            sentry__envelope_set_header(envelope, "cache_dir",
+                sentry_value_new_string(options->run->cache_path->path));
+        } else {
+            SENTRY_WARN("failed to add cache_dir to external crash report");
+        }
+    }
     sentry__transport_send_envelope(disk_transport, envelope);
     sentry__transport_dump_queue(disk_transport, options->run);
     sentry_transport_free(disk_transport);
diff --git a/src/sentry_envelope.c b/src/sentry_envelope.c
index 69d3603d8..3214ff86a 100644
--- a/src/sentry_envelope.c
+++ b/src/sentry_envelope.c
@@ -83,6 +83,25 @@ envelope_item_cleanup(sentry_envelope_item_t *item)
     sentry_free(item->payload);
 }
 
+static void
+envelope_items_cleanup(sentry_envelope_t *envelope)
+{
+    sentry_value_decref(envelope->contents.items.headers);
+
+    // Free all items in the linked list
+    sentry_envelope_item_t *item = envelope->contents.items.first_item;
+    while (item) {
+        sentry_envelope_item_t *next = item->next;
+        envelope_item_cleanup(item);
+        sentry_free(item);
+        item = next;
+    }
+
+    envelope->contents.items.first_item = NULL;
+    envelope->contents.items.last_item = NULL;
+    envelope->contents.items.item_count = 0;
+}
+
 sentry_value_t
 sentry_envelope_get_header(const sentry_envelope_t *envelope, const char *key)
 {
@@ -200,17 +219,7 @@ sentry_envelope_free(sentry_envelope_t *envelope)
         sentry_free(envelope);
         return;
     }
-    sentry_value_decref(envelope->contents.items.headers);
-
-    // Free all items in the linked list
-    sentry_envelope_item_t *item = envelope->contents.items.first_item;
-    while (item) {
-        sentry_envelope_item_t *next = item->next;
-        envelope_item_cleanup(item);
-        sentry_free(item);
-        item = next;
-    }
-
+    envelope_items_cleanup(envelope);
     sentry_free(envelope);
 }
 
@@ -1510,8 +1519,16 @@ sentry__envelope_materialize(sentry_envelope_t *envelope)
     envelope->contents.items.last_item = NULL;
     envelope->contents.items.item_count = 0;
     bool ok = deserialize_into(envelope, payload, payload_len);
+    if (!ok) {
+        envelope_items_cleanup(envelope);
+        envelope->is_raw = true;
+        envelope->contents.raw.payload = payload;
+        envelope->contents.raw.payload_len = payload_len;
+        return false;
+    }
+
     sentry_free(payload);
-    return ok;
+    return true;
 }
 
 static bool
diff --git a/tests/test_integration_crashpad.py b/tests/test_integration_crashpad.py
index 04e847124..6d6a56f57 100644
--- a/tests/test_integration_crashpad.py
+++ b/tests/test_integration_crashpad.py
@@ -760,6 +760,7 @@ def test_crashpad_external_crash_reporter(cmake, httpserver, run_args):
     tmp_path = cmake(
         ["sentry_example", "sentry_crash_reporter"], {"SENTRY_BACKEND": "crashpad"}
     )
+    cache_dir = tmp_path.joinpath(".sentry-native/cache")
 
     env = dict(os.environ, SENTRY_DSN=make_dsn(httpserver))
     httpserver.expect_oneshot_request("/api/123456/envelope/").respond_with_data("OK")
@@ -769,7 +770,7 @@ def test_crashpad_external_crash_reporter(cmake, httpserver, run_args):
         run(
             tmp_path,
             "sentry_example",
-            ["log", "crash-reporter"] + run_args,
+            ["log", "crash-reporter", "cache-keep"] + run_args,
             expect_failure=True,
             env=env,
         )
@@ -783,6 +784,7 @@ def test_crashpad_external_crash_reporter(cmake, httpserver, run_args):
     crash = crash_request.get_data()
 
     envelope = Envelope.deserialize(crash)
+    assert envelope.headers["cache_dir"] == str(cache_dir)
     assert_meta(envelope, integration="crashpad")
     assert_breadcrumb(envelope)
 
diff --git a/tests/test_integration_http.py b/tests/test_integration_http.py
index 7fc1d13dc..0b3352665 100644
--- a/tests/test_integration_http.py
+++ b/tests/test_integration_http.py
@@ -314,6 +314,7 @@ def test_user_report_http(cmake, httpserver):
 )
 def test_external_crash_reporter_http(cmake, httpserver, build_args):
     tmp_path = cmake(["sentry_example", "sentry_crash_reporter"], build_args)
+    cache_dir = tmp_path.joinpath(".sentry-native/cache")
 
     httpserver.expect_oneshot_request(
         "/api/123456/envelope/",
@@ -329,7 +330,7 @@ def test_external_crash_reporter_http(cmake, httpserver, build_args):
         run(
             tmp_path,
             "sentry_example",
-            ["log", "crash-reporter", "crash"],
+            ["log", "crash-reporter", "cache-keep", "crash"],
             expect_failure=True,
             env=env,
         )
@@ -354,6 +355,7 @@ def test_external_crash_reporter_http(cmake, httpserver, build_args):
     crash = crash_request.get_data()
 
     envelope = Envelope.deserialize(crash)
+    assert envelope.headers["cache_dir"] == str(cache_dir)
     assert_meta(envelope, integration=build_args.get("SENTRY_BACKEND", ""))
 
     envelope = Envelope.deserialize(feedback)
diff --git a/tests/test_integration_native.py b/tests/test_integration_native.py
index fd4bb37a4..5dcdafbd4 100644
--- a/tests/test_integration_native.py
+++ b/tests/test_integration_native.py
@@ -418,6 +418,7 @@ def test_native_external_crash_reporter(cmake, httpserver):
     tmp_path = cmake(
         ["sentry_example", "sentry_crash_reporter"], {"SENTRY_BACKEND": "native"}
     )
+    cache_dir = tmp_path.joinpath(".sentry-native/cache")
 
     env = dict(os.environ, SENTRY_DSN=make_dsn(httpserver))
     httpserver.expect_oneshot_request("/api/123456/envelope/").respond_with_data("OK")
@@ -428,7 +429,7 @@ def test_native_external_crash_reporter(cmake, httpserver):
         run_crash(
             tmp_path,
             "sentry_example",
-            ["log", "crash-reporter", "crash"],
+            ["log", "crash-reporter", "cache-keep", "crash"],
             env=env,
         )
     assert waiting.result
@@ -443,6 +444,7 @@ def test_native_external_crash_reporter(cmake, httpserver):
 
     # Verify it's a minidump crash report and user feedback
     envelope = Envelope.deserialize(crash)
+    assert envelope.headers["cache_dir"] == str(cache_dir)
     assert_meta(envelope)
     assert_breadcrumb(envelope)
 
diff --git a/tests/unit/test_envelopes.c b/tests/unit/test_envelopes.c
index 9cd4017ee..843dfb9d9 100644
--- a/tests/unit/test_envelopes.c
+++ b/tests/unit/test_envelopes.c
@@ -753,6 +753,13 @@ SENTRY_TEST(envelope_materialize)
     sentry_envelope_t *bad = sentry__envelope_from_path(path);
     TEST_ASSERT(!!bad);
     TEST_CHECK(!sentry__envelope_materialize(bad));
+    TEST_CHECK(sentry__envelope_is_raw(bad));
+    size_t serialized_len = 0;
+    char *serialized = sentry_envelope_serialize(bad, &serialized_len);
+    TEST_ASSERT(!!serialized);
+    TEST_CHECK_INT_EQUAL(serialized_len, 7);
+    TEST_CHECK_STRING_EQUAL(serialized, "garbage");
+    sentry_free(serialized);
     sentry_envelope_free(bad);
 
     sentry__path_remove(path);