diff --git a/bin/alsdiff.ml b/bin/alsdiff.ml
index 103d88a..3d7eed4 100644
--- a/bin/alsdiff.ml
+++ b/bin/alsdiff.ml
@@ -1,6 +1,7 @@
 open Alsdiff_base
 open Alsdiff_live
 open Alsdiff_output
+open Config
 open Eio.Std
 open View_model
 open Cmdliner
@@ -17,22 +18,12 @@ let create_views (change : (Liveset.t, Liveset.Patch.t) Diff.structured_change)
   let item = View_model.create_liveset_item change in
   [View_model.Item item]
 
-let render_views config (views : View_model.view list) : string =
-  let buffer = Buffer.create 4096 in
-  let ppf = Format.formatter_of_buffer buffer in
-  Fmt.set_style_renderer ppf `None;
-
-  List.iter (fun view ->
-      Text_renderer.pp config ppf view;
-      Fmt.pf ppf "@.";
-    ) views;
-
-  Format.pp_print_flush ppf ();
-  Buffer.contents buffer
+type output_mode = Tree | Stats
 
 type config = {
   positional_args: string list;
   git_mode: bool;
+  output_mode: output_mode;
   config_file: string option;
   preset: [ `Compact | `Composer | `Full | `Inline | `Mixing | `Quiet | `Verbose ] option;
   dump_preset: [ `Compact | `Composer | `Full | `Inline | `Mixing | `Quiet | `Verbose ] option;
@@ -121,75 +112,94 @@ let load_and_report_config config_path =
   Fmt.pr "Loading configuration from %s@." config_path;
   load_config_from_json config_path
 
-let diff_cmd ~config ~domain_mgr : int =
-  let file1, file2, reference_path =
-    if config.git_mode then
-      match parse_git_args config.positional_args with
-      | Error msg -> failwith msg
-      | Ok git_args -> (git_args.old_file, git_args.new_file, git_args.path)
-    else
-      match config.positional_args with
-      | [f1; f2] -> (f1, f2, f2)
-      | _ -> failwith "FILE1.als and FILE2.als are required for diff"
-  in
-
-  let base_renderer_config =
-    match config.config_file with
-    | Some config_path ->
-      load_config_from_json config_path
+let build_base_renderer_config ~default_config ~reference_path config =
+  match config.config_file with
+  | Some config_path ->
+    load_config_from_json config_path
+  | None ->
+    match config.preset with
+    | Some preset ->
+      let base = match preset with
+        | `Compact -> Text_renderer.compact
+        | `Composer -> Text_renderer.composer
+        | `Full -> Text_renderer.full
+        | `Inline -> Text_renderer.inline
+        | `Mixing -> Text_renderer.mixing
+        | `Quiet -> Text_renderer.quiet
+        | `Verbose -> Text_renderer.verbose
+      in base
     | None ->
-      match config.preset with
-      | Some preset ->
-        let base = match preset with
-          | `Compact -> Text_renderer.compact
-          | `Composer -> Text_renderer.composer
-          | `Full -> Text_renderer.full
-          | `Inline -> Text_renderer.inline
-          | `Mixing -> Text_renderer.mixing
-          | `Quiet -> Text_renderer.quiet
-          | `Verbose -> Text_renderer.verbose
-        in base
-      | None ->
-        (* Auto-discover .alsdiff.json when neither --config nor --preset specified *)
-        match discover_config_file ~reference_path with
-        | Some auto_config -> load_and_report_config auto_config
-        | None -> Text_renderer.quiet
-  in
+      match discover_config_file ~reference_path with
+      | Some auto_config -> load_and_report_config auto_config
+      | None -> default_config
+
+let stats_incompatible_flags_provided config =
+  config.prefix_added <> None
+  || config.prefix_removed <> None
+  || config.prefix_modified <> None
+  || config.prefix_unchanged <> None
+  || config.note_name_style <> None
+  || config.max_collection_items <> None
 
-  let renderer_config = { base_renderer_config with
-                          prefix_added = (match config.prefix_added with Some s -> s | None -> base_renderer_config.prefix_added);
-                          prefix_removed = (match config.prefix_removed with Some s -> s | None -> base_renderer_config.prefix_removed);
-                          prefix_modified = (match config.prefix_modified with Some s -> s | None -> base_renderer_config.prefix_modified);
-                          prefix_unchanged = (match config.prefix_unchanged with Some s -> s | None -> base_renderer_config.prefix_unchanged);
-                          note_name_style = (match config.note_name_style with Some s -> s | None -> base_renderer_config.note_name_style);
-                          max_collection_items = (match config.max_collection_items with Some n -> Some n | None -> base_renderer_config.max_collection_items);
-                        } in
-
-  let liveset1, liveset2 = Fiber.pair
-      (fun () -> load_liveset ~domain_mgr file1)
-      (fun () -> load_liveset ~domain_mgr file2)
-  in
+let diff_cmd ~config ~domain_mgr : int =
+  if config.output_mode = Stats && stats_incompatible_flags_provided config then begin
+    Fmt.epr "Error: --mode stats is incompatible with --prefix-*, \
+             --note-name-style, and --max-collection-items@.";
+    1
+  end else begin
+    let file1, file2, reference_path =
+      if config.git_mode then
+        match parse_git_args config.positional_args with
+        | Error msg -> failwith msg
+        | Ok git_args -> (git_args.old_file, git_args.new_file, git_args.path)
+      else
+        match config.positional_args with
+        | [f1; f2] -> (f1, f2, f2)
+        | _ -> failwith "FILE1.als and FILE2.als are required for diff"
+    in
 
-  let liveset_patch = Liveset.diff liveset1 liveset2 in
-  let has_changes = not (Liveset.Patch.is_empty liveset_patch) in
+    let liveset1, liveset2 = Fiber.pair
+        (fun () -> load_liveset ~domain_mgr file1)
+        (fun () -> load_liveset ~domain_mgr file2)
+    in
 
-  let liveset_change =
-    if has_changes then
-      `Modified liveset_patch
-    else
-      `Unchanged
-  in
+    let liveset_patch = Liveset.diff liveset1 liveset2 in
+    let has_changes = not (Liveset.Patch.is_empty liveset_patch) in
 
-  let views = create_views liveset_change in
+    let liveset_change =
+      if has_changes then
+        `Modified liveset_patch
+      else
+        `Unchanged
+    in
 
-  let output = render_views renderer_config views in
-  Fmt.pr "%s@." output;
+    let views = create_views liveset_change in
+
+    let output = match config.output_mode with
+      | Stats ->
+        let base_renderer_config = build_base_renderer_config ~default_config:stats_default ~reference_path config in
+        (* Stats mode doesn't use prefix/note_style/max_items, so no merging needed *)
+        Stats_renderer.render base_renderer_config views
+      | Tree ->
+        let base_renderer_config = build_base_renderer_config ~default_config:Text_renderer.quiet ~reference_path config in
+        let renderer_config = { base_renderer_config with
+                                prefix_added = (match config.prefix_added with Some s -> s | None -> base_renderer_config.prefix_added);
+                                prefix_removed = (match config.prefix_removed with Some s -> s | None -> base_renderer_config.prefix_removed);
+                                prefix_modified = (match config.prefix_modified with Some s -> s | None -> base_renderer_config.prefix_modified);
+                                prefix_unchanged = (match config.prefix_unchanged with Some s -> s | None -> base_renderer_config.prefix_unchanged);
+                                note_name_style = (match config.note_name_style with Some s -> s | None -> base_renderer_config.note_name_style);
+                                max_collection_items = (match config.max_collection_items with Some n -> Some n | None -> base_renderer_config.max_collection_items);
+                              } in
+        Text_renderer.render renderer_config views
+    in
 
-  (* Exit code: git mode uses trustExitCode semantics *)
-  if config.git_mode then
-    if has_changes then 1 else 0
-  else
-    0
+    Fmt.pr "%s@." output;
+
+    if config.git_mode then
+      if has_changes then 1 else 0
+    else
+      0
+  end
 
 let positional_args =
   let doc = "Positional arguments. Normal mode: FILE1.als FILE2.als. \
@@ -239,6 +249,11 @@ let max_collection_items =
   let doc = "Maximum number of items to show in collections (default from preset: None/10/50 depending on preset)" in
   Arg.(value & opt (some int) None & info ["max-collection-items"] ~docv:"N" ~doc)
 
+let output_mode =
+  let doc = "Output mode. $(b,tree)=hierarchical tree view (default), $(b,stats)=summary statistics of changes by type. \
+             Stats mode now supports --config and --preset for customizing which types appear in statistics. Incompatible with --prefix-*, --note-name-style, and --max-collection-items." in
+  Arg.(value & opt (enum ["tree", Tree; "stats", Stats]) Tree & info ["mode"] ~docv:"MODE" ~doc)
+
 let dump_schema =
   let doc = "Dump JSON schema for configuration to stdout and exit. Does not require FILE1.als or FILE2.als." in
   Arg.(value & flag & info ["dump-schema"] ~doc)
@@ -259,6 +274,8 @@ let cmd =
     `S Manpage.s_examples;
     `P "Compare two files with default quiet preset:";
     `Pre "$(cmd) v1.als v2.als";
+    `P "Show change statistics summary:";
+    `Pre "$(cmd) v1.als v2.als --mode stats";
     `P "Compare with compact output:";
     `Pre "$(cmd) v1.als v2.als --preset compact";
     `P "Compare with full details:";
@@ -312,6 +329,7 @@ let cmd =
     `P "Git mode with config file:";
     `Pre "$(cmd) --config myconfig.json --git path old-file old-hex old-mode new-file new-hex new-mode";
     `S Manpage.s_options;
+    `P "$(b,--mode MODE) selects the output mode. $(b,tree) (default) shows a hierarchical tree view of changes. $(b,stats) shows a flat summary of change counts by type (e.g., Tracks: 1 Added, 3 Modified). Stats mode is incompatible with --preset, --config, and other tree-specific options.";
     `P "$(b,--config FILE) loads configuration from JSON file. Takes precedence over auto-discovery. The --preset option is ignored when --config is specified. Individual CLI options override values from config file.";
     `P "$(b,--preset PRESET) sets the output detail preset. Available presets: $(b,compact), $(b,composer), $(b,full), $(b,mixing), $(b,quiet) (default), $(b,verbose). Takes precedence over auto-discovery but ignored when --config is specified.";
     `P "$(b,--prefix-added PREFIX) overrides prefix for added items from config file.";
@@ -336,8 +354,8 @@ let cmd =
   Cmd.make (Cmd.info "alsdiff" ~version:(match version () with
       | None -> "dev"
       | Some v -> Version.to_string v) ~doc ~man ~exits) @@
-  let+ positional_args and+ git_mode and+ config_file and+ preset and+ dump_preset and+ prefix_added and+ prefix_removed and+ prefix_modified and+ prefix_unchanged and+ note_name_style and+ max_collection_items and+ dump_schema and+ validate_config in
-  let cfg = { positional_args; git_mode; config_file; preset; dump_preset; prefix_added; prefix_removed; prefix_modified; prefix_unchanged; note_name_style; max_collection_items; dump_schema; validate_config } in
+  let+ positional_args and+ git_mode and+ config_file and+ preset and+ dump_preset and+ prefix_added and+ prefix_removed and+ prefix_modified and+ prefix_unchanged and+ note_name_style and+ max_collection_items and+ output_mode and+ dump_schema and+ validate_config in
+  let cfg = { positional_args; git_mode; output_mode; config_file; preset; dump_preset; prefix_added; prefix_removed; prefix_modified; prefix_unchanged; note_name_style; max_collection_items; dump_schema; validate_config } in
   config_ref := Some cfg;
   ()
 
diff --git a/lib/output/config.ml b/lib/output/config.ml
index 093009c..0a1002a 100644
--- a/lib/output/config.ml
+++ b/lib/output/config.ml
@@ -443,6 +443,58 @@ let quiet = {
   indent_width = 2;
 }
 
+(* stats_default preset: types shown in statistics output by default.
+   Shows the 7 core types that were historically in stats_renderer.
+   All other types set to Ignore to exclude from statistics. *)
+let stats_default = {
+  (* Base: Summary to show counts only *)
+  added = Summary;
+  removed = Summary;
+  modified = Summary;
+  unchanged = Ignore;
+
+  (* Show the 7 historically tracked types *)
+  type_overrides = [
+    { domain_type = DTTrack; override = uniform_override Summary; };
+    { domain_type = DTDevice; override = uniform_override Summary; };
+    { domain_type = DTClip; override = uniform_override Summary; };
+    { domain_type = DTNote; override = uniform_override Summary; };
+    { domain_type = DTAutomation; override = uniform_override Summary; };
+    { domain_type = DTSend; override = uniform_override Summary; };
+    { domain_type = DTParam; override = uniform_override Summary; };
+    { domain_type = DTLocator; override = uniform_override Summary; };
+
+    (* Explicitly ignore all other types for stats mode *)
+    { domain_type = DTLiveset; override = uniform_override Ignore; };
+    { domain_type = DTMixer; override = uniform_override Ignore; };
+    { domain_type = DTRouting; override = uniform_override Ignore; };
+    { domain_type = DTEvent; override = uniform_override Ignore; };
+    { domain_type = DTPreset; override = uniform_override Ignore; };
+    { domain_type = DTMacro; override = uniform_override Ignore; };
+    { domain_type = DTSnapshot; override = uniform_override Ignore; };
+    { domain_type = DTLoop; override = uniform_override Ignore; };
+    { domain_type = DTSignature; override = uniform_override Ignore; };
+    { domain_type = DTSampleRef; override = uniform_override Ignore; };
+    { domain_type = DTVersion; override = uniform_override Ignore; };
+    { domain_type = DTOther; override = uniform_override Ignore; };
+  ];
+
+  (* No limit needed for stats - just counting *)
+  max_collection_items = None;
+
+  (* Standard prefixes *)
+  prefix_added = "+";
+  prefix_removed = "-";
+  prefix_modified = "*";
+  prefix_unchanged = "=";
+
+  (* Sharp note names *)
+  note_name_style = Sharp;
+
+  (* Indent width *)
+  indent_width = 2;
+}
+
 (* Verbose preset: show everything including unchanged items.
    Useful for debugging, auditing, or understanding complete file structure.
    No limits - displays all items and all fields. *)
diff --git a/lib/output/dune b/lib/output/dune
index 5991876..a12f50c 100644
--- a/lib/output/dune
+++ b/lib/output/dune
@@ -2,9 +2,10 @@
  (name alsdiff_output)
  (public_name alsdiff.output)
  (modules
-   view_model
-   config
-   text_renderer)
+    view_model
+    config
+    text_renderer
+    stats_renderer)
  (libraries
    alsdiff_base
    alsdiff_live
diff --git a/lib/output/stats_renderer.ml b/lib/output/stats_renderer.ml
new file mode 100644
index 0000000..73d72f0
--- /dev/null
+++ b/lib/output/stats_renderer.ml
@@ -0,0 +1,84 @@
+open View_model
+open Config
+
+let display_name (dt : domain_type) : string =
+  match dt with
+  | DTTrack -> "Tracks"
+  | DTDevice -> "Devices"
+  | DTClip -> "Clips"
+  | DTNote -> "Notes"
+  | DTAutomation -> "Automations"
+  | DTSend -> "Sends"
+  | DTParam -> "Parameters"
+  | DTLocator -> "Locators"
+  | _ -> domain_type_to_string dt
+
+(* Build the initial stats list from config - include types not set to Ignore *)
+let stats_from_config (cfg : detail_config) : (domain_type * change_breakdown) list =
+  (* All domain types we might track - check if they're not Ignored *)
+  let all_types = [
+    DTLiveset; DTTrack; DTDevice; DTClip; DTNote;
+    DTAutomation; DTMixer; DTRouting; DTLocator;
+    DTParam; DTEvent; DTSend; DTPreset; DTMacro;
+    DTSnapshot; DTLoop; DTSignature; DTSampleRef;
+    DTVersion; DTOther;
+  ] in
+  (* Filter to types that should be tracked (not Ignore for their change type) *)
+  List.filter_map (fun dt ->
+      (* Check if any change type for this domain type is not Ignore *)
+      let trackable =
+        (get_effective_detail cfg Added dt <> Ignore) ||
+        (get_effective_detail cfg Removed dt <> Ignore) ||
+        (get_effective_detail cfg Modified dt <> Ignore) ||
+        (get_effective_detail cfg Unchanged dt <> Ignore)
+      in
+      if trackable then Some (dt, { added = 0; removed = 0; modified = 0 })
+      else None
+    ) all_types
+
+let increment_stats stats dt ct =
+  List.map
+    (fun (d, b) -> if d = dt then (d, increment_breakdown b ct) else (d, b))
+    stats
+
+let rec collect_view (cfg : detail_config) (stats : (domain_type * change_breakdown) list) (view : view) =
+  match view with
+  | Field _ -> stats
+  | Item item ->
+    let stats =
+      (* Use get_effective_detail to check if type should be tracked *)
+      let level = get_effective_detail cfg item.change item.domain_type in
+      if should_render_level level && item.change <> Unchanged then
+        increment_stats stats item.domain_type item.change
+      else stats
+    in
+    List.fold_left (collect_view cfg) stats item.children
+  | Collection col -> List.fold_left (collect_view cfg) stats col.items
+
+let collect (cfg : detail_config) (views : view list) : (domain_type * change_breakdown) list =
+  List.fold_left (collect_view cfg) (stats_from_config cfg) views
+
+let render_line (dt : domain_type) (b : change_breakdown) : string option =
+  if total_breakdown b = 0 then None
+  else
+    let parts =
+      List.filter_map Fun.id
+        [
+          (if b.added > 0 then Some (Printf.sprintf "%d Added" b.added)
+           else None);
+          (if b.removed > 0 then Some (Printf.sprintf "%d Removed" b.removed)
+           else None);
+          (if b.modified > 0 then Some (Printf.sprintf "%d Modified" b.modified)
+           else None);
+        ]
+    in
+    Some (Printf.sprintf "%s: %s" (display_name dt) (String.concat ", " parts))
+
+let render (cfg : detail_config) (views : view list) : string =
+  let stats = collect cfg views in
+  let lines =
+    List.filter_map (fun (dt, b) -> render_line dt b) stats
+  in
+  match lines with
+  | [] -> "No changes."
+  | _ -> String.concat "\n" lines
diff --git a/lib/output/text_renderer.ml b/lib/output/text_renderer.ml
index 32c929e..c22ed63 100644
--- a/lib/output/text_renderer.ml
+++ b/lib/output/text_renderer.ml
@@ -231,6 +231,19 @@ let pp cfg fmt view =
 let render_to_string cfg view =
   Fmt.str "%a" (pp_view cfg) view
 
+let render config (views : View_model.view list) : string =
+  let buffer = Buffer.create 4096 in
+  let ppf = Format.formatter_of_buffer buffer in
+  Fmt.set_style_renderer ppf `None;
+
+  List.iter (fun view ->
+      pp config ppf view;
+      Fmt.pf ppf "@.";
+    ) views;
+
+  Format.pp_print_flush ppf ();
+  Buffer.contents buffer
+
 (* ==================== Backward Compatibility Re-exports ==================== *)
 (* Include all Config types and functions for backward compatibility.
    This ensures that code referencing Text_renderer.Ignore, Text_renderer.detail_config_of_yojson,
diff --git a/scripts/setup-git.sh b/scripts/setup-git.sh
index e40617d..ab9c80f 100755
--- a/scripts/setup-git.sh
+++ b/scripts/setup-git.sh
@@ -70,6 +70,115 @@ fi
 git config --global diff.alsdiff.command "$ALSDIFF_CMD"
 echo "✅ Configured git to use: $ALSDIFF_CMD"
 
+# --- prepare-commit-msg hook ---
+echo ""
+echo "🔧 Optional: Install a prepare-commit-msg hook?"
+echo ""
+echo "This hook auto-generates commit message summaries from .als file changes"
+echo "using 'alsdiff --mode stats'. When you commit staged .als files, the"
+echo "commit message will be pre-filled with a change summary like:"
+echo ""
+echo "  MyProject.als:"
+echo "    Tracks: 1 Added, 3 Modified"
+echo "    Devices: 2 Added, 5 Removed"
+echo ""
+read -p "Install prepare-commit-msg hook? (y/N): " install_hook
+
+if [[ "$install_hook" =~ ^[Yy]$ ]]; then
+    HOOK_FILE=".git/hooks/prepare-commit-msg"
+    MARKER_BEGIN="# alsdiff:begin"
+    MARKER_END="# alsdiff:end"
+
+    # Check if our hook block is already installed
+    if [ -f "$HOOK_FILE" ] && grep -q "$MARKER_BEGIN" "$HOOK_FILE"; then
+        echo "✅ prepare-commit-msg hook already contains alsdiff block"
+    else
+        # Define the hook block
+        HOOK_BLOCK='
+'"$MARKER_BEGIN"'
+# Auto-generate commit message from .als file changes using alsdiff --mode stats
+# Installed by: scripts/setup-git.sh
+alsdiff_prepare_commit_msg() {
+    COMMIT_MSG_FILE="$1"
+    COMMIT_SOURCE="${2:-}"
+
+    # Skip for merges, squashes, amends, and -m messages
+    if [ -n "$COMMIT_SOURCE" ]; then
+        return
+    fi
+
+    # Check if alsdiff is available
+    if ! command -v alsdiff &> /dev/null; then
+        return
+    fi
+
+    # Find staged .als files
+    ALS_STATUS=$(git diff --cached --name-status -- "*.als" 2>/dev/null)
+    if [ -z "$ALS_STATUS" ]; then
+        return
+    fi
+
+    # Create temp directory for blob extraction
+    TMPDIR_ALS=$(mktemp -d)
+    trap "rm -rf \"$TMPDIR_ALS\"" RETURN
+
+    STATS_OUTPUT=""
+
+    while IFS=$'"'"'\t'"'"' read -r status filepath; do
+        filename=$(basename "$filepath")
+        case "$status" in
+            M)
+                # Modified: diff HEAD vs staged
+                OLD_FILE="$TMPDIR_ALS/old_${filename}"
+                NEW_FILE="$TMPDIR_ALS/new_${filename}"
+                git show "HEAD:${filepath}" > "$OLD_FILE" 2>/dev/null || continue
+                git show ":${filepath}" > "$NEW_FILE" 2>/dev/null || continue
+                DIFF_STATS=$(alsdiff --mode stats "$OLD_FILE" "$NEW_FILE" 2>/dev/null) || true
+                if [ -n "$DIFF_STATS" ] && [ "$DIFF_STATS" != "No changes." ]; then
+                    # Indent each line of stats output
+                    INDENTED=$(echo "$DIFF_STATS" | sed "s/^/  /")
+                    STATS_OUTPUT="${STATS_OUTPUT}${filepath}:\n${INDENTED}\n"
+                fi
+                ;;
+            A)
+                STATS_OUTPUT="${STATS_OUTPUT}${filepath}: New file\n"
+                ;;
+            D)
+                STATS_OUTPUT="${STATS_OUTPUT}${filepath}: Deleted\n"
+                ;;
+        esac
+    done <<< "$ALS_STATUS"
+
+    if [ -n "$STATS_OUTPUT" ]; then
+        # Prepend stats to commit message (before any # comment lines)
+        TMPFILE="$TMPDIR_ALS/commit_msg"
+        printf "%b\n" "$STATS_OUTPUT" > "$TMPFILE"
+        cat "$COMMIT_MSG_FILE" >> "$TMPFILE"
+        mv "$TMPFILE" "$COMMIT_MSG_FILE"
+    fi
+}
+alsdiff_prepare_commit_msg "$@"
+'"$MARKER_END"
+
+        if [ -f "$HOOK_FILE" ]; then
+            # Append to existing hook
+            echo "$HOOK_BLOCK" >> "$HOOK_FILE"
+            echo "✅ Appended alsdiff block to existing prepare-commit-msg hook"
+        else
+            # Create new hook
+            echo '#!/bin/bash' > "$HOOK_FILE"
+            echo "$HOOK_BLOCK" >> "$HOOK_FILE"
+            chmod +x "$HOOK_FILE"
+            echo "✅ Created prepare-commit-msg hook"
+        fi
+    fi
+else
+    echo "⏭️  Skipping prepare-commit-msg hook"
+fi
+
 echo ""
 echo "🎉 Done! Git configured with:"
-echo "   $ALSDIFF_CMD"
+echo "   Diff driver: $ALSDIFF_CMD"
+if [[ "$install_hook" =~ ^[Yy]$ ]]; then
+    echo "   Commit hook: .git/hooks/prepare-commit-msg (alsdiff --mode stats)"
+fi
diff --git a/test/dune b/test/dune
index cfb0aa1..1f3115c 100644
--- a/test/dune
+++ b/test/dune
@@ -159,6 +159,11 @@
  (modules test_view_model utils)
  (libraries alsdiff_base alsdiff_live alsdiff_output alcotest))
 
+(test
+ (name test_stats_renderer)
+ (modules test_stats_renderer)
+ (libraries alsdiff_output alcotest))
+
 ;; Auto indent files with `dune build @fmt`
 (subdir
  run
diff --git a/test/test_stats_renderer.ml b/test/test_stats_renderer.ml
new file mode 100644
index 0000000..9394765
--- /dev/null
+++ b/test/test_stats_renderer.ml
@@ -0,0 +1,165 @@
+open Alsdiff_output.View_model
+open Alsdiff_output.Stats_renderer
+open Alsdiff_output.Config
+
+let mk_field name change =
+  Field { name; change; domain_type = DTOther; oldval = None; newval = None }
+
+let mk_item name change domain_type children =
+  Item { name; change; domain_type; children }
+
+let mk_collection name change domain_type items =
+  Collection { name; change; domain_type; items }
+
+let test_empty_no_changes () =
+  let views = [mk_item "LiveSet" Unchanged DTLiveset []] in
+  let output = render stats_default views in
+  Alcotest.(check string) "no changes" "No changes." output
+
+let test_single_added_track () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_collection "Tracks" Modified DTTrack
+            [ mk_item "Track 1" Added DTTrack [mk_field "Name" Added] ]
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  Alcotest.(check string) "single added track" "Tracks: 1 Added" output
+
+let test_mixed_changes () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_collection "Tracks" Modified DTTrack
+            [ mk_item "Track 1" Added DTTrack
+                [ mk_collection "Devices" Modified DTDevice
+                    [ mk_item "Compressor" Added DTDevice [];
+                      mk_item "EQ8" Removed DTDevice [];
+                      mk_item "Reverb" Modified DTDevice [] ]
+                ;
+                  mk_collection "Clips" Modified DTClip
+                    [ mk_item "Clip A" Modified DTClip
+                        [ mk_collection "Notes" Modified DTNote
+                            [ mk_item "C4" Added DTNote [];
+                              mk_item "E4" Modified DTNote [];
+                              mk_item "G4" Modified DTNote [] ]
+                        ]
+                    ]
+                ]
+            ;
+              mk_item "Track 2" Modified DTTrack
+                [ mk_collection "Clips" Modified DTClip
+                    [ mk_item "Clip 1" Removed DTClip [] ]
+                ]
+            ;
+              mk_item "Track 3" Removed DTTrack []
+            ]
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  let lines = String.split_on_char '\n' output in
+  Alcotest.(check int) "line count" 4 (List.length lines);
+  Alcotest.(check string) "tracks line" "Tracks: 1 Added, 1 Removed, 1 Modified"
+    (List.nth lines 0);
+  Alcotest.(check string) "devices line" "Devices: 1 Added, 1 Removed, 1 Modified"
+    (List.nth lines 1);
+  Alcotest.(check string) "clips line" "Clips: 1 Removed, 1 Modified"
+    (List.nth lines 2);
+  Alcotest.(check string) "notes line" "Notes: 1 Added, 2 Modified"
+    (List.nth lines 3)
+
+let test_non_reportable_types_excluded () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_item "Mixer" Modified DTMixer [mk_field "Volume" Modified];
+          mk_item "Loop" Added DTLoop [];
+          mk_item "Version" Modified DTVersion [];
+          mk_item "SampleRef" Added DTSampleRef [];
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  Alcotest.(check string) "non-reportable excluded" "No changes." output
+
+let test_unchanged_items_omitted () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_collection "Tracks" Modified DTTrack
+            [ mk_item "Track 1" Unchanged DTTrack [];
+              mk_item "Track 2" Added DTTrack []
+            ]
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  Alcotest.(check string) "unchanged omitted" "Tracks: 1 Added" output
+
+let test_ordering () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_item "Locator 1" Added DTLocator [];
+          mk_collection "Tracks" Modified DTTrack
+            [ mk_item "Track 1" Modified DTTrack
+                [ mk_collection "Notes" Modified DTNote
+                    [ mk_item "C4" Added DTNote [] ]
+                ]
+            ]
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  let lines = String.split_on_char '\n' output in
+  Alcotest.(check int) "line count" 3 (List.length lines);
+  Alcotest.(check string) "tracks first" "Tracks: 1 Modified" (List.nth lines 0);
+  Alcotest.(check string) "notes second" "Notes: 1 Added" (List.nth lines 1);
+  Alcotest.(check string) "locators third" "Locators: 1 Added" (List.nth lines 2)
+
+let test_deeply_nested () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_collection "Tracks" Modified DTTrack
+            [ mk_item "Track 1" Modified DTTrack
+                [ mk_collection "Devices" Modified DTDevice
+                    [ mk_item "Group" Modified DTDevice
+                        [ mk_collection "Devices" Modified DTDevice
+                            [ mk_item "Inner" Added DTDevice [] ]
+                        ]
+                    ]
+                ]
+            ]
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  let lines = String.split_on_char '\n' output in
+  Alcotest.(check int) "line count" 2 (List.length lines);
+  Alcotest.(check string) "tracks" "Tracks: 1 Modified" (List.nth lines 0);
+  Alcotest.(check string) "devices counted" "Devices: 1 Added, 1 Modified" (List.nth lines 1)
+
+let test_zero_count_change_types_omitted () =
+  let views =
+    [ mk_item "LiveSet" Modified DTLiveset
+        [ mk_collection "Tracks" Modified DTTrack
+            [ mk_item "Track 1" Added DTTrack [];
+              mk_item "Track 2" Added DTTrack []
+            ]
+        ]
+    ]
+  in
+  let output = render stats_default views in
+  Alcotest.(check string) "only added shown" "Tracks: 2 Added" output
+
+let tests =
+  [
+    "empty no changes", `Quick, test_empty_no_changes;
+    "single added track", `Quick, test_single_added_track;
+    "mixed changes", `Quick, test_mixed_changes;
+    "non-reportable types excluded", `Quick, test_non_reportable_types_excluded;
+    "unchanged items omitted", `Quick, test_unchanged_items_omitted;
+    "ordering follows fixed order", `Quick, test_ordering;
+    "deeply nested counting", `Quick, test_deeply_nested;
+    "zero count change types omitted", `Quick, test_zero_count_change_types_omitted;
+  ]
+
+let () = Alcotest.run "Stats_renderer" [ "stats", tests ]