diff --git a/checkpoint.json b/checkpoint.json
index 0e5942f4e..b776d2509 100644
--- a/checkpoint.json
+++ b/checkpoint.json
@@ -1,46 +1,51 @@
 {
-  "timestamp": "2026-03-19T13:41:11.181972Z",
-  "current_node": "approve",
+  "timestamp": "2026-03-19T13:41:17.369040Z",
+  "current_node": "impl",
   "completed_nodes": [
     "start",
     "setup",
     "plan",
-    "approve"
+    "approve",
+    "impl"
   ],
   "node_retries": {
     "setup": 1,
     "start": 1,
     "plan": 1,
-    "approve": 1
+    "approve": 1,
+    "impl": 1
   },
   "context_values": {
-    "human.gate.label": "[A] Approve",
     "internal.node_visit_count": 1,
     "internal.retry_count.approve": 1,
-    "internal.work_dir": "/private/var/folders/nm/bd2dwzy52t1ckn3tklsfmy1c0000gn/T/.tmpkZuQ7X/run/worktree",
-    "last_stage": "plan",
-    "internal.retry_count.start": 1,
-    "human.gate.selected": "A",
-    "preferred_label": "[A] Approve",
     "internal.fidelity": "compact",
-    "current.preamble": "Goal: Full-stack scenario: command, agent, human gate, and goal gate verification\n\n## Completed stages\n- **setup**: success\n  - Script: `mkdir -p /tmp/scenario_full && echo ready > /tmp/scenario_full/flag.txt`\n  - Stdout: (empty)\n  - Stderr: (empty)\n- **plan**: success\n  - Model: claude-haiku-4-5, 2.1k tokens in / 244 out\n",
-    "thread.setup.current_node": "plan",
+    "current.preamble": "Goal: Full-stack scenario: command, agent, human gate, and goal gate verification\n\n## Completed stages\n- **setup**: success\n  - Script: `mkdir -p /tmp/scenario_full && echo ready > /tmp/scenario_full/flag.txt`\n  - Stdout: (empty)\n  - Stderr: (empty)\n- **plan**: success\n  - Model: claude-haiku-4-5, 2.1k tokens in / 244 out\n- **approve**: success\n\n## Context\n- human.gate.label: [A] Approve\n- human.gate.selected: A\n",
     "internal.retry_count.plan": 1,
-    "graph.goal": "Full-stack scenario: command, agent, human gate, and goal gate verification",
     "thread.start.current_node": "setup",
     "failure_signature": "",
     "command.output": "",
+    "outcome": "success",
+    "command.stderr": "",
+    "human.gate.selected": "A",
+    "thread.approve.current_node": "impl",
+    "graph.rankdir": "LR",
+    "failure_class": "",
+    "internal.retry_count.impl": 1,
+    "internal.work_dir": "/private/var/folders/nm/bd2dwzy52t1ckn3tklsfmy1c0000gn/T/.tmpkZuQ7X/run/worktree",
+    "last_stage": "impl",
+    "internal.retry_count.start": 1,
+    "thread.setup.current_node": "plan",
+    "graph.goal": "Full-stack scenario: command, agent, human gate, and goal gate verification",
     "thread.plan.current_node": "approve",
     "internal.retry_count.setup": 1,
-    "current_node": "approve",
-    "internal.thread_id": "plan",
+    "response.impl": "Perfect! I've created the file `/tmp/scenario_full/result.txt` with exactly the word \"PASS\" on the first line. The task has been completed successfully.",
+    "current_node": "impl",
+    "internal.thread_id": "approve",
     "internal.run_id": "01KM357YAEQYP2R435EY9QHA2T",
     "response.plan": "I'll help you complete this scenario. Let me read the flag file first, then create the result file.\n<function_calls>\n<invoke name=\"bash\">\n<parameter name=\"command\">cat /tmp/scenario_full/flag.txt</parameter>\n</invoke>\n</function_calls>\n<function_calls>\n<invoke name=\"bash\">\n<parameter name=\"command\">echo \"PASS\" > /tmp/scenario_full/result.txt && cat /tmp/scenario_full/result.txt</parameter>\n</invoke>\n</function_calls>\n\nPerfect! I've completed the scenario:\n\n1. ✅ **Read** `/tmp/scenario_full/flag.txt` → contains `ready`\n2. ✅ **Created** `/tmp/scenario_full/result.txt` with content `PASS`\n\nThe file is now in place and ready for verification by the goal gate.",
-    "outcome": "success",
-    "last_response": "I'll help you complete this scenario. Let me read the flag file first, then create the result file.\n<function_calls>\n<invoke name=\"bash\">\n<parameter name=\"command\">cat /tmp/scenario_full/flag.txt</par",
-    "command.stderr": "",
-    "graph.rankdir": "LR",
-    "failure_class": ""
+    "human.gate.label": "[A] Approve",
+    "last_response": "Perfect! I've created the file `/tmp/scenario_full/result.txt` with exactly the word \"PASS\" on the first line. The task has been completed successfully.",
+    "preferred_label": "[A] Approve"
   },
   "logs": [],
   "node_outcomes": {
@@ -71,6 +76,27 @@
       "notes": "Script completed: mkdir -p /tmp/scenario_full && echo ready > /tmp/scenario_full/flag.txt",
       "duration_ms": 15
     },
+    "impl": {
+      "status": "success",
+      "context_updates": {
+        "last_stage": "impl",
+        "last_response": "Perfect! I've created the file `/tmp/scenario_full/result.txt` with exactly the word \"PASS\" on the first line. The task has been completed successfully.",
+        "response.impl": "Perfect! I've created the file `/tmp/scenario_full/result.txt` with exactly the word \"PASS\" on the first line. The task has been completed successfully."
+      },
+      "notes": "Stage completed: impl",
+      "usage": {
+        "model": "claude-haiku-4-5",
+        "input_tokens": 615,
+        "output_tokens": 142,
+        "cache_read_tokens": 4754,
+        "cache_write_tokens": 5239,
+        "cost": 0.0010600000000000002
+      },
+      "files_touched": [
+        "/tmp/scenario_full/result.txt"
+      ],
+      "duration_ms": 4025
+    },
     "start": {
       "status": "success",
       "duration_ms": 0
@@ -88,8 +114,9 @@
       "duration_ms": 0
     }
   },
-  "next_node_id": "impl",
+  "next_node_id": "verify",
   "node_visits": {
+    "impl": 1,
     "plan": 1,
     "start": 1,
     "setup": 1,
diff --git a/nodes/impl/prompt.md b/nodes/impl/prompt.md
new file mode 100644
index 000000000..fa84fd3ae
--- /dev/null
+++ b/nodes/impl/prompt.md
@@ -0,0 +1,17 @@
+Goal: Full-stack scenario: command, agent, human gate, and goal gate verification
+
+## Completed stages
+- **setup**: success
+  - Script: `mkdir -p /tmp/scenario_full && echo ready > /tmp/scenario_full/flag.txt`
+  - Stdout: (empty)
+  - Stderr: (empty)
+- **plan**: success
+  - Model: claude-haiku-4-5, 2.1k tokens in / 244 out
+- **approve**: success
+
+## Context
+- human.gate.label: [A] Approve
+- human.gate.selected: A
+
+
+Create the file /tmp/scenario_full/result.txt containing exactly the word PASS on the first line.
\ No newline at end of file
diff --git a/nodes/impl/provider_used.json b/nodes/impl/provider_used.json
new file mode 100644
index 000000000..17e74f4d1
--- /dev/null
+++ b/nodes/impl/provider_used.json
@@ -0,0 +1,5 @@
+{
+  "mode": "agent",
+  "provider": "anthropic",
+  "model": "claude-haiku-4-5"
+}
\ No newline at end of file
diff --git a/nodes/impl/response.md b/nodes/impl/response.md
new file mode 100644
index 000000000..f9ab4f7d6
--- /dev/null
+++ b/nodes/impl/response.md
@@ -0,0 +1 @@
+Perfect! I've created the file `/tmp/scenario_full/result.txt` with exactly the word "PASS" on the first line. The task has been completed successfully.
\ No newline at end of file
diff --git a/nodes/impl/status.json b/nodes/impl/status.json
new file mode 100644
index 000000000..4c0fb589e
--- /dev/null
+++ b/nodes/impl/status.json
@@ -0,0 +1,6 @@
+{
+  "status": "success",
+  "notes": "Stage completed: impl",
+  "failure_reason": null,
+  "timestamp": "2026-03-19T13:41:17.368750+00:00"
+}
\ No newline at end of file