diff --git a/packages/agent/src/harness/session/jsonl/v3.ts b/packages/agent/src/harness/session/jsonl/v3.ts
index aff457d79..9b5a67519 100644
--- a/packages/agent/src/harness/session/jsonl/v3.ts
+++ b/packages/agent/src/harness/session/jsonl/v3.ts
@@ -155,7 +155,9 @@ export function parseJsonlV3Entry(line: string, seq: number): Result<Entry, Json
 					} satisfies CustomMessage,
 				} satisfies MessageEntry;
 			default:
-				// TODO(J4): Decode and normalize the remaining supported coding-agent v3 entry types.
+				// TODO(J4): Normalize v3 compaction and branch_summary entries, preserving details, usage,
+				// and required fromHook provenance, and materialize firstKeptEntryId as retainedTail.
+				// TODO(J4): Decode and normalize the remaining label and session_info entry types.
 				throw new JsonlDecodeError("schema", `has unsupported entry type ${String(value.type)}`);
 		}
 	});