diff --git a/checkpoint.json b/checkpoint.json
index 8b62eb3c3..c53041ffe 100644
--- a/checkpoint.json
+++ b/checkpoint.json
@@ -1,28 +1,35 @@
 {
-  "timestamp": "2026-03-16T12:06:13.949988Z",
-  "current_node": "setup",
+  "timestamp": "2026-03-16T12:07:13.890515Z",
+  "current_node": "solve",
   "completed_nodes": [
     "start",
-    "setup"
+    "setup",
+    "solve"
   ],
   "node_retries": {
     "setup": 1,
-    "start": 1
+    "start": 1,
+    "solve": 1
   },
   "context_values": {
     "thread.start.current_node": "setup",
-    "current.preamble": "Goal: UsernameValidator allows trailing newline in usernames\nDescription\n\t\nASCIIUsernameValidator and UnicodeUsernameValidator use the regex \nr'^[\\w.@+-]+$'\nThe intent is to only allow alphanumeric characters as well as ., @, +, and -. However, a little known quirk of Python regexes is that $ will also match a trailing newline. Therefore, the user name validators will accept usernames which end with a newline. You can avoid this behavior by instead using \\A and \\Z to terminate regexes. For example, the validator regex could be changed to\nr'\\A[\\w.@+-]+\\Z'\nin order to reject usernames that end with a newline.\nI am not sure how to officially post a patch, but the required change is trivial - using the regex above in the two validators in contrib.auth.validators.\n\n",
+    "current.preamble": "Goal: UsernameValidator allows trailing newline in usernames\nDescription\n\t\nASCIIUsernameValidator and UnicodeUsernameValidator use the regex \nr'^[\\w.@+-]+$'\nThe intent is to only allow alphanumeric characters as well as ., @, +, and -. However, a little known quirk of Python regexes is that $ will also match a trailing newline. Therefore, the user name validators will accept usernames which end with a newline. You can avoid this behavior by instead using \\A and \\Z to terminate regexes. For example, the validator regex could be changed to\nr'\\A[\\w.@+-]+\\Z'\nin order to reject usernames that end with a newline.\nI am not sure how to officially post a patch, but the required change is trivial - using the regex above in the two validators in contrib.auth.validators.\n\n\n## Completed stages\n- **setup**: fail\n  - Script: `git clone https://github.com/django/django.git . && git checkout d26b2424437dabeeca94d7900b37d2df4410da0c && python -m pip install -e .`\n  - Stdout:\n    ```\n    fatal: destination path '.' already exists and is not an empty directory.\n    ```\n  - Stderr: (empty)\n\n## Context\n- failure_class: deterministic\n- failure_signature: setup|deterministic|script failed with exit code: <n> ## stdout fatal: destination path '.' already exists and is not an empty directory.\n",
     "internal.fidelity": "compact",
     "command.output": "fatal: destination path '.' already exists and is not an empty directory.\n",
-    "internal.thread_id": "start",
-    "current_node": "setup",
-    "failure_signature": "setup|deterministic|script failed with exit code: <n> ## stdout fatal: destination path '.' already exists and is not an empty directory.",
+    "thread.setup.current_node": "solve",
+    "response.solve": "The fix works correctly. Both validators now:\n- ✅ Accept valid usernames (e.g., `validuser`)\n- ✅ Reject usernames with trailing newlines (e.g., `validuser\\n`)\n\n**Summary of changes:** In `django/contrib/auth/validators.py`, changed the regex in both `ASCIIUsernameValidator` and `UnicodeUsernameValidator` from `r'^[\\w.@+-]+$'` to `r'\\A[\\w.@+-]+\\Z'`. \n\nThe issue was that Python's `$` in regex matches both end-of-string and just before a trailing newline, while `\\Z` matches only the absolute end of the string. Similarly, `\\A` is used instead of `^` for consistency (matching only the absolute start of the string).",
+    "internal.thread_id": "setup",
+    "current_node": "solve",
+    "failure_signature": "",
+    "last_stage": "solve",
     "command.stderr": "",
+    "last_response": "The fix works correctly. Both validators now:\n- ✅ Accept valid usernames (e.g., `validuser`)\n- ✅ Reject usernames with trailing newlines (e.g., `validuser\\n`)\n\n**Summary of changes:** In `django/c",
+    "internal.retry_count.solve": 1,
     "graph.rankdir": "LR",
     "internal.node_visit_count": 1,
-    "outcome": "fail",
+    "outcome": "success",
     "graph.goal": "UsernameValidator allows trailing newline in usernames\nDescription\n\t\nASCIIUsernameValidator and UnicodeUsernameValidator use the regex \nr'^[\\w.@+-]+$'\nThe intent is to only allow alphanumeric characters as well as ., @, +, and -. However, a little known quirk of Python regexes is that $ will also match a trailing newline. Therefore, the user name validators will accept usernames which end with a newline. You can avoid this behavior by instead using \\A and \\Z to terminate regexes. For example, the validator regex could be changed to\nr'\\A[\\w.@+-]+\\Z'\nin order to reject usernames that end with a newline.\nI am not sure how to officially post a patch, but the required change is trivial - using the regex above in the two validators in contrib.auth.validators.\n",
-    "failure_class": "deterministic",
+    "failure_class": "",
     "internal.retry_count.setup": 1,
     "internal.run_id": "01KKV8M223JTFVZ853MV9PGXVD",
     "internal.retry_count.start": 1
@@ -44,14 +51,37 @@
         "failure_class": "deterministic"
       },
       "duration_ms": 26
+    },
+    "solve": {
+      "status": "success",
+      "context_updates": {
+        "response.solve": "The fix works correctly. Both validators now:\n- ✅ Accept valid usernames (e.g., `validuser`)\n- ✅ Reject usernames with trailing newlines (e.g., `validuser\\n`)\n\n**Summary of changes:** In `django/contrib/auth/validators.py`, changed the regex in both `ASCIIUsernameValidator` and `UnicodeUsernameValidator` from `r'^[\\w.@+-]+$'` to `r'\\A[\\w.@+-]+\\Z'`. \n\nThe issue was that Python's `$` in regex matches both end-of-string and just before a trailing newline, while `\\Z` matches only the absolute end of the string. Similarly, `\\A` is used instead of `^` for consistency (matching only the absolute start of the string).",
+        "last_response": "The fix works correctly. Both validators now:\n- ✅ Accept valid usernames (e.g., `validuser`)\n- ✅ Reject usernames with trailing newlines (e.g., `validuser\\n`)\n\n**Summary of changes:** In `django/c",
+        "last_stage": "solve"
+      },
+      "notes": "Stage completed: solve",
+      "usage": {
+        "model": "claude-opus-4-6",
+        "input_tokens": 5085,
+        "output_tokens": 1751,
+        "cache_read_tokens": 58025,
+        "cache_write_tokens": 10158,
+        "reasoning_tokens": 21,
+        "cost": 0.2076
+      },
+      "files_touched": [
+        "/tmp/django-fix/django/contrib/auth/validators.py"
+      ],
+      "duration_ms": 57355
     }
   },
-  "next_node_id": "solve",
+  "next_node_id": "extract_patch",
   "loop_failure_signatures": {
     "setup|deterministic|script failed with exit code: <n> ## stdout fatal: destination path '.' already exists and is not an empty directory.": 1
   },
   "node_visits": {
     "setup": 1,
+    "solve": 1,
     "start": 1
   }
 }
\ No newline at end of file
diff --git a/nodes/solve/prompt.md b/nodes/solve/prompt.md
new file mode 100644
index 000000000..93048f112
--- /dev/null
+++ b/nodes/solve/prompt.md
@@ -0,0 +1,26 @@
+Goal: UsernameValidator allows trailing newline in usernames
+Description
+	
+ASCIIUsernameValidator and UnicodeUsernameValidator use the regex 
+r'^[\w.@+-]+$'
+The intent is to only allow alphanumeric characters as well as ., @, +, and -. However, a little known quirk of Python regexes is that $ will also match a trailing newline. Therefore, the user name validators will accept usernames which end with a newline. You can avoid this behavior by instead using \A and \Z to terminate regexes. For example, the validator regex could be changed to
+r'\A[\w.@+-]+\Z'
+in order to reject usernames that end with a newline.
+I am not sure how to officially post a patch, but the required change is trivial - using the regex above in the two validators in contrib.auth.validators.
+
+
+## Completed stages
+- **setup**: fail
+  - Script: `git clone https://github.com/django/django.git . && git checkout d26b2424437dabeeca94d7900b37d2df4410da0c && python -m pip install -e .`
+  - Stdout:
+    ```
+    fatal: destination path '.' already exists and is not an empty directory.
+    ```
+  - Stderr: (empty)
+
+## Context
+- failure_class: deterministic
+- failure_signature: setup|deterministic|script failed with exit code: <n> ## stdout fatal: destination path '.' already exists and is not an empty directory.
+
+
+Fix this GitHub issue in the repository. Make the minimal code change needed.
\ No newline at end of file
diff --git a/nodes/solve/provider_used.json b/nodes/solve/provider_used.json
new file mode 100644
index 000000000..c1905ff10
--- /dev/null
+++ b/nodes/solve/provider_used.json
@@ -0,0 +1,5 @@
+{
+  "mode": "agent",
+  "provider": "anthropic",
+  "model": "claude-opus-4-6"
+}
\ No newline at end of file
diff --git a/nodes/solve/response.md b/nodes/solve/response.md
new file mode 100644
index 000000000..1af5aa6a9
--- /dev/null
+++ b/nodes/solve/response.md
@@ -0,0 +1,7 @@
+The fix works correctly. Both validators now:
+- ✅ Accept valid usernames (e.g., `validuser`)
+- ✅ Reject usernames with trailing newlines (e.g., `validuser\n`)
+
+**Summary of changes:** In `django/contrib/auth/validators.py`, changed the regex in both `ASCIIUsernameValidator` and `UnicodeUsernameValidator` from `r'^[\w.@+-]+$'` to `r'\A[\w.@+-]+\Z'`. 
+
+The issue was that Python's `$` in regex matches both end-of-string and just before a trailing newline, while `\Z` matches only the absolute end of the string. Similarly, `\A` is used instead of `^` for consistency (matching only the absolute start of the string).
\ No newline at end of file
diff --git a/nodes/solve/status.json b/nodes/solve/status.json
new file mode 100644
index 000000000..1c6980f2d
--- /dev/null
+++ b/nodes/solve/status.json
@@ -0,0 +1,6 @@
+{
+  "status": "success",
+  "notes": "Stage completed: solve",
+  "failure_reason": null,
+  "timestamp": "2026-03-16T12:07:13.889615+00:00"
+}
\ No newline at end of file