fix: include snapshot diff in json output

src/cortex-cli/src/debug_cmd/handlers/snapshot.rs

@@ -7,7 +7,7 @@ use cortex_engine::rollout::get_rollout_path;
 use cortex_protocol::ConversationId;
 
 use crate::debug_cmd::commands::SnapshotArgs;
-use crate::debug_cmd::types::{SnapshotDebugOutput, SnapshotInfo};
+use crate::debug_cmd::types::{SnapshotDebugOutput, SnapshotDiffInfo, SnapshotInfo};
 use crate::debug_cmd::utils::{format_size, get_cortex_home};
 
 /// Run the snapshot debug command.
@@ -196,6 +196,10 @@ pub async fn run_snapshot(args: SnapshotArgs) -> Result<()> {
         snapshot_count,
         session_snapshots,
         total_size_bytes,
+        diff: args.diff.then(|| SnapshotDiffInfo {
+            status: "not_implemented".to_string(),
+            message: "Snapshot diff not yet implemented".to_string(),
+        }),
     };
 
     if args.json {

src/cortex-cli/src/debug_cmd/types.rs

@@ -215,6 +215,8 @@ pub struct SnapshotDebugOutput {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub session_snapshots: Option<Vec<SnapshotInfo>>,
     pub total_size_bytes: u64,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub diff: Option<SnapshotDiffInfo>,
 }
 
 /// Snapshot info.
@@ -225,6 +227,13 @@ pub struct SnapshotInfo {
     pub size_bytes: u64,
 }
 
+/// Snapshot diff status.
+#[derive(Debug, Serialize)]
+pub struct SnapshotDiffInfo {
+    pub status: String,
+    pub message: String,
+}
+
 // =============================================================================
 // Paths types
 // =============================================================================

src/cortex-cli/tests/debug_snapshot_json_diff.rs

@@ -0,0 +1,28 @@
+use std::process::Command;
+
+#[test]
+fn debug_snapshot_json_includes_diff_when_requested() {
+    let output = Command::new(env!("CARGO_BIN_EXE_Cortex"))
+        .args(["debug", "snapshot", "--json", "--diff"])
+        .env("NO_COLOR", "1")
+        .output()
+        .expect("run Cortex debug snapshot");
+
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let stderr = String::from_utf8_lossy(&output.stderr);
+
+    assert!(
+        output.status.success(),
+        "debug snapshot failed\nstdout:\n{stdout}\nstderr:\n{stderr}"
+    );
+
+    let json: serde_json::Value =
+        serde_json::from_str(&stdout).expect("debug snapshot output should be JSON");
+    assert_eq!(json["diff"]["status"], "not_implemented");
+    assert!(
+        json["diff"]["message"]
+            .as_str()
+            .is_some_and(|message| message.contains("not yet implemented")),
+        "diff message should explain snapshot diff status\nstdout:\n{stdout}"
+    );
+}