diff --git a/infer/lib/python/infer b/infer/lib/python/infer
index 1bb87f0ee..f4569af8c 100755
--- a/infer/lib/python/infer
+++ b/infer/lib/python/infer
@@ -114,6 +114,7 @@ def main():
 
     remove_infer_out = (imported_module
                         and not args.incremental
+                        and not args.reactive
                         and capture_module_name != 'analyze'
                         and not args.buck)
     if remove_infer_out:
diff --git a/infer/lib/python/inferlib/analyze.py b/infer/lib/python/inferlib/analyze.py
index cb11444f0..63e6dc5d8 100644
--- a/infer/lib/python/inferlib/analyze.py
+++ b/infer/lib/python/inferlib/analyze.py
@@ -75,6 +75,9 @@ base_group.add_argument('-ic', '--changed-only',
                         action=ConfirmIncrementalAction,
                         help='''Same as -i, but does not analyze
                         dependencies of changed procedures.''')
+base_group.add_argument('--reactive', action='store_true',
+                        help='''Analyze in reactive propagation mode
+                        starting from changed files.''')
 base_group.add_argument('--debug-exceptions', action='store_true',
                         help='''Generate lightweight debugging information:
                         just print the internal exceptions during analysis''')
@@ -418,6 +421,9 @@ class Infer:
             else:
                 infer_options.append('-incremental')
 
+        if self.args.reactive:
+            infer_options.append('-reactive')
+
         if self.args.specs_dirs:
             infer_options += self.args.specs_dirs
 
diff --git a/infer/src/backend/clusterMakefile.ml b/infer/src/backend/clusterMakefile.ml
index 3fd52aeb1..2c3e09dc1 100644
--- a/infer/src/backend/clusterMakefile.ml
+++ b/infer/src/backend/clusterMakefile.ml
@@ -30,12 +30,29 @@ let pp_prolog fmt clusters =
         begin
           match Cluster.get_ondemand_info ce with
           | Some source_dir ->
-              let in_ondemand_config = match Ondemand.read_dirs_to_analyze () with
+              let fname = DB.source_dir_to_string source_dir in
+              let in_ondemand_config =
+                match Ondemand.read_dirs_to_analyze () with
                 | None ->
-                    true
+                    None
                 | Some set ->
-                    StringSet.mem (DB.source_dir_to_string source_dir) set in
-              in_ondemand_config
+                    Some (StringSet.mem fname set) in
+              let check_modified () =
+                let modified =
+                  DB.file_was_updated_after_start (DB.filename_from_string fname) in
+                if modified &&
+                   !Config.developer_mode
+                then L.stdout "Modified: %s@." fname;
+                modified in
+              begin
+                match in_ondemand_config with
+                | Some b -> (* ondemand config file is specified *)
+                    b
+                | None when !Config.reactive_mode  ->
+                    check_modified ()
+                | None ->
+                    true
+              end
           | None ->
               true
         end
diff --git a/infer/src/backend/config.ml b/infer/src/backend/config.ml
index 6ceed0dd4..987389734 100644
--- a/infer/src/backend/config.ml
+++ b/infer/src/backend/config.ml
@@ -179,9 +179,14 @@ let eradicate = ref false
 (** should the checkers be run? *)
 let checkers_enabled () = not !eradicate
 
-(** flag to activate ondemand mode. *)
+(** flag for ondemand mode:
+    procedure calls trigger a new analysis if the summary is not present already *)
 let ondemand_enabled = ref false
 
+(** flag for reactive mode:
+    the analysis starts from the files captured since the "infer" command started *)
+let reactive_mode = ref false
+
 (** Flag for footprint discovery mode *)
 let footprint = ref true
 
diff --git a/infer/src/backend/inferanalyze.ml b/infer/src/backend/inferanalyze.ml
index bcedeb4e6..0f68c3342 100644
--- a/infer/src/backend/inferanalyze.ml
+++ b/infer/src/backend/inferanalyze.ml
@@ -177,6 +177,11 @@ let arg_desc =
         None,
         "print the builtin functions and exit"
         ;
+        "-reactive",
+        Arg.Unit (fun () -> Config.ondemand_enabled := true; Config.reactive_mode := true),
+        None,
+        "analyze in reactive propagation mode starting from changed files"
+        ;
         "-source_path",
         Arg.String source_path,
         Some "path",