diff --git a/evalharness/agent/envs/swe_agentic.py b/evalharness/agent/envs/swe_agentic.py
index f99b212..c1f18cb 100644
--- a/evalharness/agent/envs/swe_agentic.py
+++ b/evalharness/agent/envs/swe_agentic.py
@@ -171,8 +171,10 @@ class SWEAgenticEnvironment(Environment):
                 total_usage = total_usage + out.usage
                 text = out.text or ''
                 if SENTINEL in text:
-                    # payload after the sentinel echo = `cat patch.txt` output
-                    patch = text.split(SENTINEL, 1)[1].strip()
+                    # payload after the sentinel echo = `cat patch.txt` output.
+                    # A unified diff must end with a newline; a stripped
+                    # payload fails git apply with 'corrupt patch at line N'
+                    patch = text.split(SENTINEL, 1)[1].strip() + '\n'
                     break
                 if out.tool_calls:
                     messages.append(ChatMessage(role='assistant', content=text))
@@ -184,7 +186,7 @@ class SWEAgenticEnvironment(Environment):
                             content=f"exit={res['exit']}\n{res['out']}"))
                         if SENTINEL in res['out']:
                             # sentinel appeared in command output: capture patch
-                            patch = res['out'].split(SENTINEL, 1)[1].strip()
+                            patch = res['out'].split(SENTINEL, 1)[1].strip() + '\n'
                 else:
                     # no tool call: nudge per protocol
                     messages.append(ChatMessage(role='assistant', content=text))