diff --git a/nbd/.claude/settings.json b/nbd/.claude/settings.json
index 0b7ed38..c97511a 100644
--- a/nbd/.claude/settings.json
+++ b/nbd/.claude/settings.json
@@ -3,7 +3,9 @@
     "allow": [
       "Bash(cargo:*)",
       "Bash(git:*)",
-      "Bash(ls:*)"
+      "Bash(ls:*)",
+      "Edit",
+      "Write"
     ]
   }
 }
diff --git a/nbd/.nbd/tickets/5f1495.md b/nbd/.nbd/tickets/5f1495.md
index f70a163..af2fcab 100644
--- a/nbd/.nbd/tickets/5f1495.md
+++ b/nbd/.nbd/tickets/5f1495.md
@@ -1,7 +1,7 @@
 +++
 title = "nbd update diff output"
 priority = 5
-status = "todo"
+status = "done"
 ticket_type = "feature"
 dependencies = []
 +++
diff --git a/nbd/src/display.rs b/nbd/src/display.rs
index 1f64097..3ab2208 100644
--- a/nbd/src/display.rs
+++ b/nbd/src/display.rs
@@ -266,6 +266,69 @@ pub fn print_migrate_report_json(report: &MigrateReport) {
     println!("{}", format_migrate_report_json(report));
 }
 
+/// Format a git-diff-style `- old / + new` summary of what changed between
+/// two [`Ticket`] snapshots.
+///
+/// Each field that differs produces two lines:
+///
+/// ```text
+/// - status:         todo
+/// + status:         in_progress
+/// ```
+///
+/// Fields compared: `title`, `body`, `priority`, `status`, `ticket_type`, and
+/// `dependencies`.  The `id` field is never shown because it cannot change.
+///
+/// Returns `"(no changes)"` when every compared field is identical.
+pub fn format_diff(old: &Ticket, new: &Ticket) -> String {
+    let mut lines: Vec<String> = Vec::new();
+
+    macro_rules! diff_field {
+        ($label:expr, $old_val:expr, $new_val:expr) => {{
+            let old_s: String = $old_val;
+            let new_s: String = $new_val;
+            if old_s != new_s {
+                lines.push(format!("- {:<LABEL_WIDTH$}{}", $label, old_s));
+                lines.push(format!("+ {:<LABEL_WIDTH$}{}", $label, new_s));
+            }
+        }};
+    }
+
+    diff_field!("title:", old.title.clone(), new.title.clone());
+    diff_field!("body:", old.body.clone(), new.body.clone());
+    diff_field!(
+        "priority:",
+        old.priority.to_string(),
+        new.priority.to_string()
+    );
+    diff_field!(
+        "status:",
+        status_str(&old.status).to_string(),
+        status_str(&new.status).to_string()
+    );
+    diff_field!(
+        "type:",
+        ticket_type_str(&old.ticket_type).to_string(),
+        ticket_type_str(&new.ticket_type).to_string()
+    );
+    diff_field!(
+        "dependencies:",
+        old.dependencies.join(", "),
+        new.dependencies.join(", ")
+    );
+
+    if lines.is_empty() {
+        "(no changes)".to_string()
+    } else {
+        lines.join("\n")
+    }
+}
+
+/// Print a git-diff-style summary of what changed between two tickets to stdout.
+pub fn print_diff(old: &Ticket, new: &Ticket) {
+    println!("{}", format_diff(old, new));
+}
+
 // ── Graph rendering ───────────────────────────────────────────────────────────
 
 /// Format the full dependency forest as an ASCII tree string.
diff --git a/nbd/src/main.rs b/nbd/src/main.rs
index 81d2ac6..0f23286 100644
--- a/nbd/src/main.rs
+++ b/nbd/src/main.rs
@@ -778,6 +778,7 @@ async fn cmd_update(
     let old_format = detect_format(&existing_path);
 
     let mut ticket = read_ticket(&root, &id).await?;
+    let old = ticket.clone();
 
     if let Some(t) = title {
         ticket.title = t;
@@ -817,7 +818,7 @@ async fn cmd_update(
     if json {
         display::print_ticket_json(&ticket);
     } else {
-        display::print_ticket(&ticket);
+        display::print_diff(&old, &ticket);
     }
 
     Ok(())
diff --git a/nbd/src/tests.rs b/nbd/src/tests.rs
index 0893a6d..f2d091e 100644
--- a/nbd/src/tests.rs
+++ b/nbd/src/tests.rs
@@ -1318,8 +1318,8 @@ mod display_graph {
 /// Tests for [`crate::display`].
 mod display {
     use crate::display::{
-        format_list, format_list_json, format_migrate_report, format_migrate_report_json,
-        format_ticket, format_ticket_json,
+        format_diff, format_list, format_list_json, format_migrate_report,
+        format_migrate_report_json, format_ticket, format_ticket_json,
     };
     use crate::store::MigrateReport;
     use crate::ticket::{Status, Ticket, TicketType};
@@ -1572,4 +1572,84 @@ mod display {
         assert_eq!(parsed["errors"][0]["filename"], "err.json");
         assert_eq!(parsed["errors"][0]["message"], "bad");
     }
+
+    // ── format_diff ───────────────────────────────────────────────────────────
+
+    /// `format_diff` returns `"(no changes)"` when old and new are identical.
+    #[test]
+    fn format_diff_no_changes() {
+        let t = sample_ticket();
+        let output = format_diff(&t, &t);
+        assert_eq!(output, "(no changes)");
+    }
+
+    /// `format_diff` shows `- old` and `+ new` lines only for changed fields.
+    #[test]
+    fn format_diff_shows_changed_fields_only() {
+        let old = sample_ticket(); // status: in_progress
+        let mut new = sample_ticket();
+        new.status = Status::Done;
+        let output = format_diff(&old, &new);
+        assert!(
+            output.contains("- status:"),
+            "should show old status line: {output}"
+        );
+        assert!(
+            output.contains("+ status:"),
+            "should show new status line: {output}"
+        );
+        assert!(
+            output.contains("in_progress"),
+            "should show old status value: {output}"
+        );
+        assert!(
+            output.contains("done"),
+            "should show new status value: {output}"
+        );
+        // Unchanged fields must not appear.
+        assert!(
+            !output.contains("title:"),
+            "unchanged title should not appear: {output}"
+        );
+        assert!(
+            !output.contains("priority:"),
+            "unchanged priority should not appear: {output}"
+        );
+    }
+
+    /// `format_diff` shows multiple changed fields when several differ.
+    #[test]
+    fn format_diff_multiple_changed_fields() {
+        let old = sample_ticket();
+        let mut new = sample_ticket();
+        new.status = Status::Done;
+        new.priority = 3;
+        let output = format_diff(&old, &new);
+        assert!(output.contains("status:"), "status diff should appear");
+        assert!(output.contains("priority:"), "priority diff should appear");
+        // title unchanged — must not appear.
+        assert!(
+            !output.contains("title:"),
+            "unchanged title should not appear: {output}"
+        );
+    }
+
+    /// `format_diff` renders dependency changes as comma-separated lists.
+    #[test]
+    fn format_diff_dependencies_comma_separated() {
+        let mut old = sample_ticket(); // deps: b7d41e, c9e823
+        let mut new = sample_ticket();
+        old.dependencies = vec!["aaaaaa".to_string()];
+        new.dependencies = vec!["bbbbbb".to_string(), "cccccc".to_string()];
+        let output = format_diff(&old, &new);
+        assert!(
+            output.contains("dependencies:"),
+            "dependencies diff should appear: {output}"
+        );
+        assert!(output.contains("aaaaaa"), "old dep should appear: {output}");
+        assert!(
+            output.contains("bbbbbb, cccccc"),
+            "new deps should be comma-separated: {output}"
+        );
+    }
 }
diff --git a/nbd/tests/integration.rs b/nbd/tests/integration.rs
index 075b158..b84d2c6 100644
--- a/nbd/tests/integration.rs
+++ b/nbd/tests/integration.rs
@@ -1696,7 +1696,10 @@ fn graph_chain() {
 
     // B's line should use `└──`.
     let line_b = stdout.lines().find(|l| l.contains(&id_b)).unwrap();
-    assert!(line_b.contains("└──"), "child should use └── connector: {line_b}");
+    assert!(
+        line_b.contains("└──"),
+        "child should use └── connector: {line_b}"
+    );
 }
 
 /// `nbd graph <id>` for ticket A shows A and its dependents but not unrelated
@@ -1714,7 +1717,10 @@ fn graph_single_ticket_subtree() {
 
     assert!(stdout.contains(&id_a), "root should be in subtree");
     assert!(stdout.contains(&id_b), "dependent should be in subtree");
-    assert!(!stdout.contains(&id_c), "unrelated ticket should be absent: {stdout}");
+    assert!(
+        !stdout.contains(&id_c),
+        "unrelated ticket should be absent: {stdout}"
+    );
 }
 
 /// `nbd graph --json` produces valid JSON with `nodes` and `edges` arrays.
@@ -1730,12 +1736,22 @@ fn graph_json_output() {
     let parsed: serde_json::Value =
         serde_json::from_str(&stdout).expect("--json should produce valid JSON");
 
-    let nodes = parsed["nodes"].as_array().expect("nodes should be an array");
-    let edges = parsed["edges"].as_array().expect("edges should be an array");
+    let nodes = parsed["nodes"]
+        .as_array()
+        .expect("nodes should be an array");
+    let edges = parsed["edges"]
+        .as_array()
+        .expect("edges should be an array");
 
     let node_ids: Vec<&str> = nodes.iter().map(|n| n["id"].as_str().unwrap()).collect();
-    assert!(node_ids.contains(&id_a.as_str()), "nodes should include id_a");
-    assert!(node_ids.contains(&id_b.as_str()), "nodes should include id_b");
+    assert!(
+        node_ids.contains(&id_a.as_str()),
+        "nodes should include id_a"
+    );
+    assert!(
+        node_ids.contains(&id_b.as_str()),
+        "nodes should include id_b"
+    );
     assert_eq!(edges.len(), 1, "should have exactly one edge (A blocks B)");
     assert_eq!(edges[0]["from"].as_str().unwrap(), id_a);
     assert_eq!(edges[0]["to"].as_str().unwrap(), id_b);
@@ -1776,7 +1792,10 @@ fn graph_filter() {
     let stdout = String::from_utf8(output.stdout).unwrap();
 
     assert!(stdout.contains(&id_bug), "bug ticket should be visible");
-    assert!(!stdout.contains(&id_task), "task ticket should be excluded: {stdout}");
+    assert!(
+        !stdout.contains(&id_task),
+        "task ticket should be excluded: {stdout}"
+    );
 }
 
 /// `nbd graph <3-char-prefix>` resolves to the correct ticket using prefix
@@ -1794,5 +1813,80 @@ fn graph_partial_id() {
         String::from_utf8_lossy(&output.stderr)
     );
     let stdout = String::from_utf8(output.stdout).unwrap();
-    assert!(stdout.contains(&id_a), "resolved ticket should appear in output");
+    assert!(
+        stdout.contains(&id_a),
+        "resolved ticket should appear in output"
+    );
+}
+
+// ── update diff output tests ──────────────────────────────────────────────────
+
+/// `nbd update <id> --status in_progress` (no `--json`) prints `- status:` and
+/// `+ status:` lines showing what changed.
+#[test]
+fn update_no_json_prints_diff() {
+    let env = TestEnv::new();
+    let id = env.create(&["--title", "Diff test"]);
+
+    let output = env.run(&["update", &id, "--status", "in_progress"]);
+    assert!(
+        output.status.success(),
+        "update failed: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    assert!(
+        stdout.contains("- status:"),
+        "should show old status line: {stdout}"
+    );
+    assert!(
+        stdout.contains("+ status:"),
+        "should show new status line: {stdout}"
+    );
+    assert!(stdout.contains("todo"), "should show old value: {stdout}");
+    assert!(
+        stdout.contains("in_progress"),
+        "should show new value: {stdout}"
+    );
+}
+
+/// `nbd update <id> --json` still prints full JSON (no diff).
+#[test]
+fn update_with_json_flag_prints_full_ticket() {
+    let env = TestEnv::new();
+    let id = env.create(&["--title", "JSON update test"]);
+
+    let output = env.run(&["update", &id, "--status", "in_progress", "--json"]);
+    assert!(
+        output.status.success(),
+        "update --json failed: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    // Must be valid JSON containing the updated ticket.
+    let parsed: serde_json::Value =
+        serde_json::from_str(&stdout).expect("--json output should be valid JSON");
+    assert_eq!(parsed["status"], "in_progress");
+    assert_eq!(parsed["title"], "JSON update test");
+    // Should NOT contain diff markers.
+    assert!(
+        !stdout.contains("- status:"),
+        "JSON output should not contain diff markers: {stdout}"
+    );
+}
+
+/// `nbd update` with no changes prints `(no changes)`.
+#[test]
+fn update_no_changes_prints_no_changes() {
+    let env = TestEnv::new();
+    let id = env.create(&["--title", "Unchanged"]);
+
+    // Update with no field changes (supply same status).
+    let output = env.run(&["update", &id, "--status", "todo"]);
+    assert!(output.status.success());
+    let stdout = String::from_utf8(output.stdout).unwrap();
+    assert!(
+        stdout.contains("(no changes)"),
+        "should print '(no changes)' when nothing changed: {stdout}"
+    );
 }