diff --git a/checkpoint.json b/checkpoint.json
index 2a325d322..d3ab0f130 100644
--- a/checkpoint.json
+++ b/checkpoint.json
@@ -1,28 +1,35 @@
 {
-  "timestamp": "2026-03-16T12:05:27.060157Z",
-  "current_node": "setup",
+  "timestamp": "2026-03-16T12:07:55.009635Z",
+  "current_node": "solve",
   "completed_nodes": [
     "start",
-    "setup"
+    "setup",
+    "solve"
   ],
   "node_retries": {
     "start": 1,
-    "setup": 1
+    "setup": 1,
+    "solve": 1
   },
   "context_values": {
     "command.stderr": "",
-    "internal.thread_id": "start",
-    "current.preamble": "Goal: Correct expected format in invalid DurationField error message\nDescription\n\t\nIf you enter a duration \"14:00\" into a duration field, it translates to \"00:14:00\" which is 14 minutes.\nThe current error message for invalid DurationField says that this should be the format of durations: \"[DD] [HH:[MM:]]ss[.uuuuuu]\". But according to the actual behaviour, it should be: \"[DD] [[HH:]MM:]ss[.uuuuuu]\", because seconds are mandatory, minutes are optional, and hours are optional if minutes are provided.\nThis seems to be a mistake in all Django versions that support the DurationField.\nAlso the duration fields could have a default help_text with the requested format, because the syntax is not self-explanatory.\n\n",
+    "last_stage": "solve",
+    "response.solve": "The regex confirms:\n- Line 33: Hours are captured only when lookahead confirms `\\d+:\\d+` follows (meaning both MM and ss must be present after HH)\n- Line 34: Minutes are optional\n- Line 35: Seconds are mandatory\n\nSo the correct format notation is `[[HH:]MM:]ss` — seconds are always required, minutes are optional, and hours are optional but require minutes. This matches the fix: `[DD] [[HH:]MM:]ss[.uuuuuu]`.\n\n**Summary of changes:**\n\n1. **`django/db/models/fields/__init__.py`** (line 1590): Changed the DurationField error message format from `[DD] [HH:[MM:]]ss[.uuuuuu]` to `[DD] [[HH:]MM:]ss[.uuuuuu]` to correctly describe that seconds are mandatory, minutes are optional, and hours are optional only when minutes are provided.\n\n2. **`tests/model_fields/test_durationfield.py`** (line 78): Updated the test to match the corrected error message format.",
+    "internal.thread_id": "setup",
+    "internal.retry_count.solve": 1,
+    "current.preamble": "Goal: Correct expected format in invalid DurationField error message\nDescription\n\t\nIf you enter a duration \"14:00\" into a duration field, it translates to \"00:14:00\" which is 14 minutes.\nThe current error message for invalid DurationField says that this should be the format of durations: \"[DD] [HH:[MM:]]ss[.uuuuuu]\". But according to the actual behaviour, it should be: \"[DD] [[HH:]MM:]ss[.uuuuuu]\", because seconds are mandatory, minutes are optional, and hours are optional if minutes are provided.\nThis seems to be a mistake in all Django versions that support the DurationField.\nAlso the duration fields could have a default help_text with the requested format, because the syntax is not self-explanatory.\n\n\n## Completed stages\n- **setup**: fail\n  - Script: `git clone https://github.com/django/django.git . && git checkout 17455e924e243e7a55e8a38f45966d8cbb27c273 && 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.retry_count.setup": 1,
     "command.output": "fatal: destination path '.' already exists and is not an empty directory.\n",
-    "failure_signature": "setup|deterministic|script failed with exit code: <n> ## stdout fatal: destination path '.' already exists and is not an empty directory.",
+    "last_response": "The regex confirms:\n- Line 33: Hours are captured only when lookahead confirms `\\d+:\\d+` follows (meaning both MM and ss must be present after HH)\n- Line 34: Minutes are optional\n- Line 35: Seconds ar",
+    "failure_signature": "",
     "graph.goal": "Correct expected format in invalid DurationField error message\nDescription\n\t\nIf you enter a duration \"14:00\" into a duration field, it translates to \"00:14:00\" which is 14 minutes.\nThe current error message for invalid DurationField says that this should be the format of durations: \"[DD] [HH:[MM:]]ss[.uuuuuu]\". But according to the actual behaviour, it should be: \"[DD] [[HH:]MM:]ss[.uuuuuu]\", because seconds are mandatory, minutes are optional, and hours are optional if minutes are provided.\nThis seems to be a mistake in all Django versions that support the DurationField.\nAlso the duration fields could have a default help_text with the requested format, because the syntax is not self-explanatory.\n",
     "graph.rankdir": "LR",
     "internal.fidelity": "compact",
-    "outcome": "fail",
-    "current_node": "setup",
+    "outcome": "success",
+    "thread.setup.current_node": "solve",
+    "current_node": "solve",
     "internal.retry_count.start": 1,
-    "failure_class": "deterministic",
+    "failure_class": "",
     "internal.node_visit_count": 1,
     "internal.run_id": "01KKV8JN2HR5HW549Z6KACQY2C",
     "thread.start.current_node": "setup"
@@ -41,16 +48,39 @@
       },
       "duration_ms": 24
     },
+    "solve": {
+      "status": "success",
+      "context_updates": {
+        "last_response": "The regex confirms:\n- Line 33: Hours are captured only when lookahead confirms `\\d+:\\d+` follows (meaning both MM and ss must be present after HH)\n- Line 34: Minutes are optional\n- Line 35: Seconds ar",
+        "last_stage": "solve",
+        "response.solve": "The regex confirms:\n- Line 33: Hours are captured only when lookahead confirms `\\d+:\\d+` follows (meaning both MM and ss must be present after HH)\n- Line 34: Minutes are optional\n- Line 35: Seconds are mandatory\n\nSo the correct format notation is `[[HH:]MM:]ss` — seconds are always required, minutes are optional, and hours are optional but require minutes. This matches the fix: `[DD] [[HH:]MM:]ss[.uuuuuu]`.\n\n**Summary of changes:**\n\n1. **`django/db/models/fields/__init__.py`** (line 1590): Changed the DurationField error message format from `[DD] [HH:[MM:]]ss[.uuuuuu]` to `[DD] [[HH:]MM:]ss[.uuuuuu]` to correctly describe that seconds are mandatory, minutes are optional, and hours are optional only when minutes are provided.\n\n2. **`tests/model_fields/test_durationfield.py`** (line 78): Updated the test to match the corrected error message format."
+      },
+      "notes": "Stage completed: solve",
+      "usage": {
+        "model": "claude-opus-4-6",
+        "input_tokens": 17129,
+        "output_tokens": 3944,
+        "cache_read_tokens": 448208,
+        "cache_write_tokens": 22594,
+        "reasoning_tokens": 104,
+        "cost": 0.552735
+      },
+      "files_touched": [
+        "/tmp/django_repo/django/db/models/fields/__init__.py"
+      ],
+      "duration_ms": 145498
+    },
     "start": {
       "status": "success",
       "duration_ms": 0
     }
   },
-  "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": {
+    "solve": 1,
     "start": 1,
     "setup": 1
   }
diff --git a/nodes/solve/prompt.md b/nodes/solve/prompt.md
new file mode 100644
index 000000000..2a7715acc
--- /dev/null
+++ b/nodes/solve/prompt.md
@@ -0,0 +1,24 @@
+Goal: Correct expected format in invalid DurationField error message
+Description
+	
+If you enter a duration "14:00" into a duration field, it translates to "00:14:00" which is 14 minutes.
+The current error message for invalid DurationField says that this should be the format of durations: "[DD] [HH:[MM:]]ss[.uuuuuu]". But according to the actual behaviour, it should be: "[DD] [[HH:]MM:]ss[.uuuuuu]", because seconds are mandatory, minutes are optional, and hours are optional if minutes are provided.
+This seems to be a mistake in all Django versions that support the DurationField.
+Also the duration fields could have a default help_text with the requested format, because the syntax is not self-explanatory.
+
+
+## Completed stages
+- **setup**: fail
+  - Script: `git clone https://github.com/django/django.git . && git checkout 17455e924e243e7a55e8a38f45966d8cbb27c273 && 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..b7c5e98b7
--- /dev/null
+++ b/nodes/solve/response.md
@@ -0,0 +1,12 @@
+The regex confirms:
+- Line 33: Hours are captured only when lookahead confirms `\d+:\d+` follows (meaning both MM and ss must be present after HH)
+- Line 34: Minutes are optional
+- Line 35: Seconds are mandatory
+
+So the correct format notation is `[[HH:]MM:]ss` — seconds are always required, minutes are optional, and hours are optional but require minutes. This matches the fix: `[DD] [[HH:]MM:]ss[.uuuuuu]`.
+
+**Summary of changes:**
+
+1. **`django/db/models/fields/__init__.py`** (line 1590): Changed the DurationField error message format from `[DD] [HH:[MM:]]ss[.uuuuuu]` to `[DD] [[HH:]MM:]ss[.uuuuuu]` to correctly describe that seconds are mandatory, minutes are optional, and hours are optional only when minutes are provided.
+
+2. **`tests/model_fields/test_durationfield.py`** (line 78): Updated the test to match the corrected error message format.
\ No newline at end of file
diff --git a/nodes/solve/status.json b/nodes/solve/status.json
new file mode 100644
index 000000000..39d440f0b
--- /dev/null
+++ b/nodes/solve/status.json
@@ -0,0 +1,6 @@
+{
+  "status": "success",
+  "notes": "Stage completed: solve",
+  "failure_reason": null,
+  "timestamp": "2026-03-16T12:07:55.008674+00:00"
+}
\ No newline at end of file