diff --git a/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-child/behavior.json b/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-child/behavior.json
index d44a3a9698..fd06978be1 100644
--- a/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-child/behavior.json
+++ b/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-child/behavior.json
@@ -2,11 +2,11 @@
   "prompt": "respond",
   "logs": [
     { "file": "b/parent.jsonl", "lines": [
-      { "type": "session", "id": "{{SID}}", "createdAt": 700, "cwd": "{{CWD}}" },
+      { "type": "session", "id": "{{SID}}", "createdAt": 700, "cwd": "{{CWD}}", "delegationDepth": 0 },
       { "type": "request/header", "seq": 0, "time": 3, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } }
     ]},
     { "file": "b/child.jsonl", "lines": [
-      { "type": "session", "id": "abababab-cdcd-4efe-8ada-badabadabada", "createdAt": 800, "cwd": "{{CWD}}", "parentSession": "{{SID}}" },
+      { "type": "session", "id": "abababab-cdcd-4efe-8ada-badabadabada", "createdAt": 800, "cwd": "{{CWD}}", "parentSession": "{{SID}}", "delegationDepth": 1 },
       { "type": "request/header", "seq": 0, "time": 2, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } }
     ]}
   ]
diff --git a/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-pin/behavior.json b/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-pin/behavior.json
index a24e30d80a..b0ed5f1a3f 100644
--- a/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-pin/behavior.json
+++ b/packages/support/acp-snapshot/tests/fixtures/record-suite/rec-pin/behavior.json
@@ -3,7 +3,7 @@
   "logs": [{
     "file": "b/main.jsonl",
     "lines": [
-      { "type": "session", "id": "{{SID}}", "createdAt": 600, "cwd": "{{CWD}}" },
+      { "type": "session", "id": "{{SID}}", "createdAt": 600, "cwd": "{{CWD}}", "delegationDepth": 0 },
       { "type": "request/header", "seq": 0, "time": 4, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } }
     ]
   }]
diff --git a/packages/support/acp-snapshot/tests/fixtures/suite/authored-error/behavior.json b/packages/support/acp-snapshot/tests/fixtures/suite/authored-error/behavior.json
index 808d9672b9..991de99fd6 100644
--- a/packages/support/acp-snapshot/tests/fixtures/suite/authored-error/behavior.json
+++ b/packages/support/acp-snapshot/tests/fixtures/suite/authored-error/behavior.json
@@ -3,7 +3,7 @@
   "logs": [{
     "file": "b/main.jsonl",
     "lines": [
-      { "type": "session", "id": "{{SID}}", "createdAt": 500, "cwd": "{{CWD}}" },
+      { "type": "session", "id": "{{SID}}", "createdAt": 500, "cwd": "{{CWD}}", "delegationDepth": 0 },
       { "type": "turn/end", "seq": 1, "time": 9, "data": { "error": "model exploded" } }
     ]
   }]
diff --git a/packages/support/acp-snapshot/tests/fixtures/suite/blocked-log/behavior.json b/packages/support/acp-snapshot/tests/fixtures/suite/blocked-log/behavior.json
index e0a438297d..209159da7d 100644
--- a/packages/support/acp-snapshot/tests/fixtures/suite/blocked-log/behavior.json
+++ b/packages/support/acp-snapshot/tests/fixtures/suite/blocked-log/behavior.json
@@ -3,7 +3,7 @@
   "logs": [{
     "file": "b/main.jsonl",
     "lines": [
-      { "type": "session", "id": "{{SID}}", "createdAt": 400, "cwd": "{{CWD}}" },
+      { "type": "session", "id": "{{SID}}", "createdAt": 400, "cwd": "{{CWD}}", "delegationDepth": 0 },
       { "type": "hook/result", "seq": 1, "time": 8, "data": { "decision": "block", "durationMs": 37 } }
     ]
   }]
diff --git a/packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/behavior.json b/packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/behavior.json
index 4b63893a62..ad4c368e49 100644
--- a/packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/behavior.json
+++ b/packages/support/acp-snapshot/tests/fixtures/suite/pin-turn/behavior.json
@@ -3,7 +3,7 @@
   "logs": [{
     "file": "b/main.jsonl",
     "lines": [
-      { "type": "session", "id": "{{SID}}", "createdAt": 100, "cwd": "{{CWD}}" },
+      { "type": "session", "id": "{{SID}}", "createdAt": 100, "cwd": "{{CWD}}", "delegationDepth": 0 },
       { "type": "request/header", "seq": 0, "time": 100, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } },
       { "type": "request/header", "seq": 1, "time": 100, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT\n\nNEW PROMPT LINE", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "change" } },
       { "type": "turn/start", "seq": 2, "time": 100, "data": { "turn": 1 } }
diff --git a/packages/support/acp-snapshot/tests/fixtures/suite/plain-turn/behavior.json b/packages/support/acp-snapshot/tests/fixtures/suite/plain-turn/behavior.json
index d5cbbf9d28..8903d0360e 100644
--- a/packages/support/acp-snapshot/tests/fixtures/suite/plain-turn/behavior.json
+++ b/packages/support/acp-snapshot/tests/fixtures/suite/plain-turn/behavior.json
@@ -3,12 +3,12 @@
   "echoWorkspace": true,
   "logs": [
     { "file": "b/parent.jsonl", "lines": [
-      { "type": "session", "id": "{{SID}}", "createdAt": 200, "cwd": "{{CWD}}" },
+      { "type": "session", "id": "{{SID}}", "createdAt": 200, "cwd": "{{CWD}}", "delegationDepth": 0 },
       { "type": "request/header", "seq": 0, "time": 5, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } },
       { "type": "assistant/chunk", "seq": 1, "time": 5, "data": { "turn": 1, "step": 1, "chunk": { "type": "text-delta", "index": 0, "text": "hi" } } }
     ]},
     { "file": "b/child.jsonl", "lines": [
-      { "type": "session", "id": "eeeeeeee-1111-4222-8333-444444444444", "createdAt": 300, "cwd": "{{CWD}}", "parentSession": "{{SID}}" },
+      { "type": "session", "id": "eeeeeeee-1111-4222-8333-444444444444", "createdAt": 300, "cwd": "{{CWD}}", "parentSession": "{{SID}}", "delegationDepth": 1 },
       { "type": "request/header", "seq": 0, "time": 6, "data": { "header": { "config": { "model": "fake" }, "system": "SYS PROMPT", "tools": [{ "name": "t1", "description": "D1", "parameters": { "type": "object" } }] }, "reason": "initial" } }
     ]}
   ]
diff --git a/packages/support/acp-snapshot/tests/suite.spec.ts b/packages/support/acp-snapshot/tests/suite.spec.ts
index ac6f944a4a..6fbb06bb9d 100644
--- a/packages/support/acp-snapshot/tests/suite.spec.ts
+++ b/packages/support/acp-snapshot/tests/suite.spec.ts
@@ -90,12 +90,12 @@ function staleRefreshFixtures(dir: string): void {
   writeFileSync(plainBehaviorFile, `${JSON.stringify(plainBehavior, null, 2)}\n`)
 
   writeFileSync(join(dir, 'blocked-log', 'session.jsonl'), [
-    '{"type":"session","id":"99999999-8888-4777-8666-555555555555","createdAt":13,"cwd":"/rec/blocked-cwd"}',
+    '{"type":"session","id":"99999999-8888-4777-8666-555555555555","createdAt":13,"cwd":"/rec/blocked-cwd","delegationDepth":0}',
     '{"type":"hook/result","seq":1,"time":13,"data":{"decision":"stale","durationMs":99}}',
     '',
   ].join('\n'))
   writeFileSync(join(dir, 'authored-error', 'session.jsonl'), [
-    '{"type":"session","id":"77777777-8888-4777-8666-555555555555","createdAt":13,"cwd":"/rec/error-cwd"}',
+    '{"type":"session","id":"77777777-8888-4777-8666-555555555555","createdAt":13,"cwd":"/rec/error-cwd","delegationDepth":0}',
     '{"type":"turn/end","seq":1,"time":9,"data":{"error":"stale"}}',
     '',
   ].join('\n'))