diff --git a/tasktypes/vendoring.py b/tasktypes/vendoring.py
index be929c7..d3a3c29 100644
--- a/tasktypes/vendoring.py
+++ b/tasktypes/vendoring.py
@@ -25,6 +25,13 @@ def _patch_exception_message(e):
     return str(e)
 
 
+def _is_patch_conflict(e):
+    # `./mach vendor --patch-mode only` applies the patches and then runs the
+    # post-patch actions. Only a patch that didn't apply is something the AI can
+    # fix; mach logs this message for that case and not for a failed action.
+    return "Could not apply" in _patch_exception_message(e)
+
+
 class VendorTaskRunner(BaseTaskRunner):
     def __init__(self, provider_dictionary, config_dictionary):
         self.jobType = JOBTYPE.VENDORING
@@ -193,6 +200,13 @@ def _process_new_job(self, library, task, new_version, timestamp, most_recent_jo
             except Exception as e:
                 msg = _patch_exception_message(e)
 
+                if not _is_patch_conflict(e):
+                    # Something other than a patch conflict failed (e.g. a
+                    # post-patch action), which the AI can't resolve.
+                    self.dbProvider.update_job_status(created_job, JOBSTATUS.DONE, JOBOUTCOME.COULD_NOT_PATCH)
+                    self.bugzillaProvider.comment_on_bug(created_job.bugzilla_id, CommentTemplates.COULD_NOT_GENERAL_ERROR("apply the mozilla patches (this wasn't a patch conflict, so Updatebot didn't ask its AI assistant to resolve it)", errormessage=msg), needinfo=library.maintainer_bz)
+                    return
+
                 # The mozilla patches didn't apply cleanly. Ask the AI to try to
                 # resolve the conflicts (updating the .patch files / moz.yaml).
                 potential_commit_message = "Bug %s - Update %s local patches to apply cleanly" % (
diff --git a/tests/functionality_all_platforms.py b/tests/functionality_all_platforms.py
index 9f45184..e39948f 100755
--- a/tests/functionality_all_platforms.py
+++ b/tests/functionality_all_platforms.py
@@ -368,7 +368,7 @@ def testFailsDuringPatching(self):
             lambda: 50,  # get_filed_bug_id_func,
             lambda b: {},  # filed_bug_ids_func
             AssertFalse,  # treeherder_response
-            command_callbacks={'patch': lambda: raise_(Exception("No patching!"))}
+            command_callbacks={'patch': lambda: raise_(Exception("Could not apply mozilla.patch, possible reasons:"))}
         )
         try:
             u.run(library_filter=library_filter)
@@ -380,10 +380,35 @@ def testFailsDuringPatching(self):
             self.assertEqual(JOBSTATUS.DONE, j.status, "Expected status JOBSTATUS.DONE, got status %s" % (j.status.name))
             self.assertEqual(JOBOUTCOME.COULD_NOT_PATCH, j.outcome, "Expected outcome JOBOUTCOME.COULD_NOT_PATCH, got outcome %s" % (j.outcome.name))
             self.assertEqual(expected_values.get_filed_bug_id_func(), j.bugzilla_id)
+            self.assertEqual(u.aiProvider.resolve_call_count, 1, "A patch conflict should have been given to the AI")
 
         finally:
             self._cleanup(u, expected_values)
 
+    # Create -> patching fails, but not because a patch didn't apply (e.g. a
+    # post-patch action failed) -> the AI isn't asked -> COULD_NOT_PATCH
+    @logEntryExitHeaderLine
+    def testPatchFailureNotAConflictSkipsAI(self):
+        library_filter = 'png'
+        (u, expected_values, _check_jobs) = self._setup(
+            library_filter,
+            lambda b: ["try_rev|2021-02-09 15:30:04 -0500|2021-02-12 17:40:01 +0000"],
+            lambda: 56,  # get_filed_bug_id_func
+            lambda b: {},  # filed_bug_ids_func
+            AssertFalse,  # treeherder_response
+            command_callbacks={'patch': lambda: raise_(Exception("Importing local patches...\nERROR: Could not find revision field in moz.yaml."))},
+            ai_config={'ai_outcome': 'trivial success', 'ai_details': ['Should not be asked.']},
+        )
+        try:
+            u.run(library_filter=library_filter)
+            self.assertEqual(u.aiProvider.resolve_call_count, 0, "The AI should not be asked about a failure that isn't a patch conflict")
+            lib = [lib for lib in u.libraryProvider.get_libraries(u.config_dictionary['General']['gecko-path']) if library_filter in lib.name][0]
+            j = u.dbProvider.get_job(lib, expected_values.library_new_version_id())
+            self.assertEqual(JOBSTATUS.DONE, j.status)
+            self.assertEqual(JOBOUTCOME.COULD_NOT_PATCH, j.outcome)
+        finally:
+            self._cleanup(u, expected_values)
+
     # Create -> patch fails -> AI resolves the conflict -> re-apply succeeds -> proceeds
     @logEntryExitHeaderLine
     def testPatchConflictResolvedByAI(self):
@@ -392,7 +417,7 @@ def testPatchConflictResolvedByAI(self):
         def patch_callback():
             patch_calls[0] += 1
             if patch_calls[0] == 1:
-                raise_(Exception("patch does not apply cleanly"))
+                raise_(Exception("Could not apply mozilla.patch, possible reasons:"))
             return ""
 
         arc_calls = [0]
@@ -438,7 +463,7 @@ def testPatchConflictResolvedByAIUncertain(self):
         def patch_callback():
             patch_calls[0] += 1
             if patch_calls[0] == 1:
-                raise_(Exception("patch does not apply cleanly"))
+                raise_(Exception("Could not apply mozilla.patch, possible reasons:"))
             return ""
 
         arc_calls = [0]
@@ -480,7 +505,7 @@ def testPatchConflictAIResolvedButReapplyStillFails(self):
             lambda: 54,  # get_filed_bug_id_func
             lambda b: {},  # filed_bug_ids_func
             AssertFalse,  # treeherder_response
-            command_callbacks={'patch': lambda: raise_(Exception("patch still does not apply"))},
+            command_callbacks={'patch': lambda: raise_(Exception("Could not apply mozilla.patch, possible reasons:"))},
             ai_config={'ai_outcome': 'trivial success', 'ai_details': ['I think I fixed it.']},
         )
         try: