diff --git a/docs/schemas/craft.schema.json b/docs/schemas/craft.schema.json
index 63a74a57..40c26670 100644
--- a/docs/schemas/craft.schema.json
+++ b/docs/schemas/craft.schema.json
@@ -12,6 +12,13 @@
       ],
       "default": null
     },
+    "agent_session_by": {
+      "description": "The coding agent that saved `agent_session` (`claude-code`, `codex`…); none: saved before\nthis was kept.",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
     "allowed_actions": {
       "description": "Kinds of agent action the person allowed for this workspace (\"bash:npm\", \"web_fetch\"…).",
       "type": "array",