diff --git a/lib/action.ml b/lib/action.ml
index 9cc90492..c9cecb14 100644
--- a/lib/action.ml
+++ b/lib/action.ml
@@ -58,12 +58,12 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
 
   let partition_pr_review_comment cfg (n : pr_review_comment_notification) =
     match n.action with
-    | Created -> partition_label cfg n.pull_request.labels
+    | Created | Edited -> partition_label cfg n.pull_request.labels
     | _ -> []
 
   let partition_issue_comment cfg (n : issue_comment_notification) =
     match n.action with
-    | Created -> partition_label cfg n.issue.labels
+    | Created | Edited -> partition_label cfg n.issue.labels
     | _ -> []
 
   let partition_pr_review cfg (n : pr_review_notification) =
@@ -79,7 +79,7 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
 
        in both cases, since pull_request_review_comment is already handled by another type of event, information in the pull_request_review payload
        does not provide any insightful information and will thus be ignored. *)
-    | Submitted, _, _ -> partition_label cfg n.pull_request.labels
+    | (Submitted | Edited), _, _ -> partition_label cfg n.pull_request.labels
     | _ -> []
 
   let partition_commit (cfg : Config_t.config) files =
@@ -174,6 +174,46 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
     | Some sender_login -> List.exists cfg.ignored_users ~f:(String.equal sender_login)
     | None -> false
 
+  let generate_stateful_notification (ctx : Context.t) content req channel =
+    match req with
+    | Github.PR_review_comment n ->
+      ( match n.action with
+      | Github_t.Created -> Some (generate_new_message content channel)
+      | Edited ->
+        ( match State.get_comment_msg ctx.state n.repository.url ~issue_num:n.pull_request.number n.comment.id with
+        | None ->
+          log#warn "could not find comment %d in %s for PR #%n" n.comment.id n.repository.url n.pull_request.number;
+          None
+        | Some ts -> Some (generate_update_message content ~ts channel)
+        )
+      | _ -> None
+      )
+    | Issue_comment n ->
+      ( match n.action with
+      | Github_t.Created -> Some (generate_new_message content channel)
+      | Edited ->
+        ( match State.get_comment_msg ctx.state n.repository.url ~issue_num:n.issue.number n.comment.id with
+        | None ->
+          log#warn "could not find comment %d in %s for issue #%n" n.comment.id n.repository.url n.issue.number;
+          None
+        | Some ts -> Some (generate_update_message content ~ts channel)
+        )
+      | _ -> None
+      )
+    | PR_review n ->
+      ( match n.action with
+      | Github_t.Submitted -> Some (generate_new_message content channel)
+      | Edited ->
+        ( match State.get_review_msg ctx.state n.repository.url ~issue_num:n.pull_request.number n.review.id with
+        | None ->
+          log#warn "could not find review %d in %s for PR #%n" n.review.id n.repository.url n.pull_request.number;
+          None
+        | Some ts -> Some (generate_update_message content ~ts channel)
+        )
+      | _ -> None
+      )
+    | _ -> Some (generate_new_message content channel)
+
   let generate_notifications (ctx : Context.t) (req : Github.t) =
     let repo = Github.repo_of_notification req in
     let cfg = Context.find_repo_config_exn ctx repo.url in
@@ -182,30 +222,84 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
     | false ->
     match req with
     | Github.Push n ->
-      partition_push cfg n |> List.map ~f:(fun (channel, n) -> generate_push_notification n channel) |> Lwt.return
-    | Pull_request n -> partition_pr cfg n |> List.map ~f:(generate_pull_request_notification n) |> Lwt.return
-    | PR_review n -> partition_pr_review cfg n |> List.map ~f:(generate_pr_review_notification n) |> Lwt.return
+      partition_push cfg n
+      |> List.map ~f:(fun (channel, n) ->
+           generate_stateful_notification ctx (generate_push_notification_content n) req channel
+         )
+      |> Lwt.return
+    | Pull_request n ->
+      partition_pr cfg n
+      |> List.map ~f:(fun channel ->
+           generate_stateful_notification ctx (generate_pull_request_notification_content n) req channel
+         )
+      |> Lwt.return
+    | PR_review n ->
+      partition_pr_review cfg n
+      |> List.map ~f:(fun channel ->
+           generate_stateful_notification ctx (generate_pr_review_notification_content n) req channel
+         )
+      |> Lwt.return
     | PR_review_comment n ->
-      partition_pr_review_comment cfg n |> List.map ~f:(generate_pr_review_comment_notification n) |> Lwt.return
-    | Issue n -> partition_issue cfg n |> List.map ~f:(generate_issue_notification n) |> Lwt.return
+      partition_pr_review_comment cfg n
+      |> List.map ~f:(fun channel ->
+           generate_stateful_notification ctx (generate_pr_review_comment_notification_content n) req channel
+         )
+      |> Lwt.return
+    | Issue n ->
+      partition_issue cfg n
+      |> List.map ~f:(fun channel ->
+           generate_stateful_notification ctx (generate_issue_notification_content n) req channel
+         )
+      |> Lwt.return
     | Issue_comment n ->
-      partition_issue_comment cfg n |> List.map ~f:(generate_issue_comment_notification n) |> Lwt.return
+      partition_issue_comment cfg n
+      |> List.map ~f:(fun channel ->
+           (* not sure why but when I remove "fun channel" it evaluates the [generate_issue_comment_notification_content n] before the partition so I got errors but when I add this, it's completely fine, probably some compiler optimization? *)
+           generate_stateful_notification ctx (generate_issue_comment_notification_content n) req channel
+         )
+      |> Lwt.return
     | Commit_comment n ->
       let%lwt channels, api_commit = partition_commit_comment ctx n in
-      let notifs = List.map ~f:(generate_commit_comment_notification api_commit n) channels in
+      let notifs =
+        List.map
+          ~f:(generate_stateful_notification ctx (generate_commit_comment_notification_content api_commit n) req)
+          channels
+      in
       Lwt.return notifs
     | Status n ->
       let%lwt channels = partition_status ctx n in
-      let notifs = List.map ~f:(generate_status_notification cfg n) channels in
+      let notifs =
+        List.map
+          ~f:(fun channel -> generate_stateful_notification ctx (generate_status_notification_content cfg n) req channel)
+          channels
+      in
       Lwt.return notifs
     | _ -> Lwt.return []
 
-  let send_notifications (ctx : Context.t) notifications =
-    let notify (msg : Slack_t.post_message_req) =
-      match%lwt Slack_api.send_notification ~ctx ~msg with
-      | Ok () -> Lwt.return_unit
-      | Error e -> action_error e
+  let send_notifications (ctx : Context.t) (req : Github.t) notifications =
+    let update_comment_mapping message =
+      match req with
+      | Github.PR_review_comment n ->
+        State.add_comment_msg ctx.state n.repository.url ~issue_num:n.pull_request.number n.comment.id message
+      | Issue_comment n ->
+        State.add_comment_msg ctx.state n.repository.url ~issue_num:n.issue.number n.comment.id message
+      | PR_review n ->
+        State.add_review_msg ctx.state n.repository.url ~issue_num:n.pull_request.number n.review.id message
+      | _ -> Lwt.return_unit
+    in
+    let notify = function
+      | New_message (msg : Slack_t.post_message_req) ->
+        ( match%lwt Slack_api.send_notification ~ctx ~msg with
+        | Ok res -> update_comment_mapping res.ts
+        | Error e -> action_error e
+        )
+      | Update_message msg ->
+        ( match%lwt Slack_api.update_notification ~ctx ~msg with
+        | Ok () -> Lwt.return_unit
+        | Error e -> action_error e
+        )
     in
+
     Lwt_list.iter_s notify notifications
 
   (** [refresh_repo_config ctx n] fetches the latest repo config if it's
@@ -253,6 +347,13 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
       end
     | _ -> Lwt.return_unit
 
+  let cleanup_state (ctx : Context.t) (payload : Github.t) =
+    match payload with
+    | Github.Pull_request { action = Closed; pull_request = { number; _ }; repository = { url; _ }; _ }
+    | Issue { action = Closed; issue = { number; _ }; repository = { url; _ }; _ } ->
+      State.close_issue ctx.state url number
+    | _ -> Lwt.return_unit
+
   let process_github_notification (ctx : Context.t) headers body =
     let validate_signature secrets payload =
       let repo = Github.repo_of_notification payload in
@@ -278,10 +379,14 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
           | Error e -> action_error e
           | Ok () ->
             let%lwt notifications = generate_notifications ctx payload in
-            let%lwt () = Lwt.join [ send_notifications ctx notifications; do_github_tasks ctx repo payload ] in
+            let%lwt () =
+              Lwt.join
+                [ send_notifications ctx payload (List.filter_opt notifications); do_github_tasks ctx repo payload ]
+            in
             ( match ctx.state_filepath with
             | None -> Lwt.return_unit
             | Some path ->
+              let%lwt () = cleanup_state ctx payload in
               ( match%lwt State.save ctx.state path with
               | Ok () -> Lwt.return_unit
               | Error e -> action_error e
diff --git a/lib/api.ml b/lib/api.ml
index c1be62a0..a01cf91b 100644
--- a/lib/api.ml
+++ b/lib/api.ml
@@ -18,7 +18,8 @@ module type Github = sig
 end
 
 module type Slack = sig
-  val send_notification : ctx:Context.t -> msg:post_message_req -> unit slack_response Lwt.t
+  val send_notification : ctx:Context.t -> msg:post_message_req -> post_message_res slack_response Lwt.t
+  val update_notification : ctx:Context.t -> msg:update_message_req -> unit slack_response Lwt.t
 
   val send_chat_unfurl
     :  ctx:Context.t ->
diff --git a/lib/api_local.ml b/lib/api_local.ml
index 524c241d..2319bec6 100644
--- a/lib/api_local.ml
+++ b/lib/api_local.ml
@@ -53,6 +53,7 @@ end
 (** The base implementation for local check payload debugging and mocking tests *)
 module Slack_base : Api.Slack = struct
   let send_notification ~ctx:_ ~msg:_ = Lwt.return @@ Error "undefined for local setup"
+  let update_notification ~ctx:_ ~msg:_ = Lwt.return @@ Error "undefined for local setup"
   let send_chat_unfurl ~ctx:_ ~channel:_ ~ts:_ ~unfurls:_ () = Lwt.return @@ Error "undefined for local setup"
   let send_auth_test ~ctx:_ () = Lwt.return @@ Error "undefined for local setup"
 end
@@ -65,6 +66,14 @@ module Slack : Api.Slack = struct
     let json = msg |> Slack_j.string_of_post_message_req |> Yojson.Basic.from_string |> Yojson.Basic.pretty_to_string in
     Stdio.printf "will notify #%s\n" msg.channel;
     Stdio.printf "%s\n" json;
+    Lwt.return @@ Ok ({ channel = msg.channel; ts = "SOMETS" } : Slack_t.post_message_res)
+
+  let update_notification ~ctx:_ ~msg =
+    let json =
+      msg |> Slack_j.string_of_update_message_req |> Yojson.Basic.from_string |> Yojson.Basic.pretty_to_string
+    in
+    Stdio.printf "will update msg in #%s\n" msg.channel;
+    Stdio.printf "%s\n" json;
     Lwt.return @@ Ok ()
 
   let send_chat_unfurl ~ctx:_ ~channel ~ts ~unfurls () =
@@ -91,6 +100,14 @@ module Slack_simple : Api.Slack = struct
       | None -> ""
       | Some s -> sprintf " with %S" s
       );
+    Lwt.return @@ Ok ({ channel = msg.channel; ts = "SOMETS" } : Slack_t.post_message_res)
+
+  let update_notification ~ctx:_ ~(msg : Slack_t.update_message_req) =
+    log#info "will update msg in #%s: %s\n" msg.channel
+      ( match msg.Slack_t.text with
+      | None -> ""
+      | Some s -> sprintf " with %S" s
+      );
     Lwt.return @@ Ok ()
 
   let send_chat_unfurl ~ctx:_ ~channel ~ts:_ ~(unfurls : Slack_t.message_attachment Common.StringMap.t) () =
@@ -117,6 +134,15 @@ module Slack_json : Api.Slack = struct
     let url = Uri.add_query_param url ("msg", [ json ]) in
     log#info "%s" (Uri.to_string url);
     log#info "%s" json;
+    Lwt.return @@ Ok ({ channel = msg.channel; ts = "SOMETS" } : Slack_t.post_message_res)
+
+  let update_notification ~ctx:_ ~(msg : Slack_t.update_message_req) =
+    log#info "will notify %s" msg.channel;
+    let json = Slack_j.string_of_update_message_req msg in
+    let url = Uri.of_string "https://api.slack.com/docs/messages/builder" in
+    let url = Uri.add_query_param url ("msg", [ json ]) in
+    log#info "%s" (Uri.to_string url);
+    log#info "%s" json;
     Lwt.return @@ Ok ()
 
   let send_chat_unfurl ~ctx:_ ~channel ~ts:_ ~(unfurls : Slack_t.message_attachment Common.StringMap.t) () =
diff --git a/lib/api_remote.ml b/lib/api_remote.ml
index 525d527f..0aba78e2 100644
--- a/lib/api_remote.ml
+++ b/lib/api_remote.ml
@@ -117,36 +117,46 @@ module Slack : Api.Slack = struct
     (* must read whole response to update lexer state *)
     ignore (Slack_j.read_ok_res s l)
 
+  let webhook_channel_request (ctx : Context.t) ~channel ~build_error read body =
+    match Context.hook_of_channel ctx channel with
+    | Some url ->
+      ( match%lwt http_request ~body ~headers:[] `POST url with
+      | Ok res -> Lwt.return_ok @@ read res
+      | Error e -> Lwt.return @@ build_error (query_error_msg url e)
+      )
+    | None -> Lwt.return @@ build_error (sprintf "no hook for channel: %s" channel)
+
   (** [send_notification ctx msg] notifies [msg.channel] with the payload [msg];
       uses web API with access token if available, or with webhook otherwise *)
   let send_notification ~(ctx : Context.t) ~(msg : Slack_t.post_message_req) =
     log#info "sending to %s" msg.channel;
     let build_error e = fmt_error "%s\nfailed to send Slack notification" e in
-    let secrets = Context.get_secrets_exn ctx in
-    let headers, url, webhook_mode =
-      match Context.hook_of_channel ctx msg.channel with
-      | Some url -> [], Some url, true
-      | None ->
-      match secrets.slack_access_token with
-      | Some access_token -> [ bearer_token_header access_token ], Some "https://slack.com/api/chat.postMessage", false
-      | None -> [], None, false
-    in
-    match url with
-    | None -> Lwt.return @@ build_error @@ sprintf "no token or webhook configured to notify channel %s" msg.channel
-    | Some url ->
-      let data = Slack_j.string_of_post_message_req msg in
-      let body = `Raw ("application/json", data) in
-      log#info "data: %s" data;
-      if webhook_mode then begin
-        match%lwt http_request ~body ~headers `POST url with
-        | Ok _res -> Lwt.return @@ Ok ()
-        | Error e -> Lwt.return @@ build_error (query_error_msg url e)
-      end
-      else begin
-        match%lwt slack_api_request ~body ~headers `POST url Slack_j.read_post_message_res with
-        | Ok _res -> Lwt.return @@ Ok ()
-        | Error e -> Lwt.return @@ build_error e
-      end
+    let data = Slack_j.string_of_post_message_req msg in
+    let body = `Raw ("application/json", data) in
+    log#info "data: %s" data;
+    match%lwt webhook_channel_request ctx ~channel:msg.channel ~build_error Slack_j.post_message_res_of_string body with
+    | Ok res -> Lwt.return_ok res
+    | Error e ->
+      log#warn "failed to run webhook call: %s" e;
+      request_token_auth ~name:"post message to channel" ~body ~ctx `POST "chat.postMessage"
+        Slack_j.read_post_message_res
+
+  (** [update_notification ctx msg] update a message at [msg.ts] in [msg.channel]
+      with the payload [msg]; uses web API with access token if available, or with
+      webhook otherwise *)
+  let update_notification ~(ctx : Context.t) ~(msg : Slack_t.update_message_req) =
+    log#info "sending to %s" msg.channel;
+    let build_error e = fmt_error "%s\nfailed to update Slack notification" e in
+    let data = Slack_j.string_of_update_message_req msg in
+    let body = `Raw ("application/json", data) in
+    log#info "data: %s" data;
+    match%lwt
+      webhook_channel_request ctx ~channel:msg.channel ~build_error Slack_j.update_message_res_of_string body
+    with
+    | Ok (_res : Slack_t.update_message_res) -> Lwt.return_ok ()
+    | Error e ->
+      log#warn "failed to run webhook call: %s" e;
+      request_token_auth ~name:"update message in channel" ~body ~ctx `POST "chat.update" read_unit
 
   let send_chat_unfurl ~(ctx : Context.t) ~channel ~ts ~unfurls () =
     let req = Slack_j.{ channel; ts; unfurls } in
diff --git a/lib/github.atd b/lib/github.atd
index 43c55fa4..2a424942 100644
--- a/lib/github.atd
+++ b/lib/github.atd
@@ -185,6 +185,7 @@ type pr_notification = {
 
 type review = {
   ?body: string nullable;
+  id: int;
   html_url: string;
   state: string;
 }
diff --git a/lib/slack.atd b/lib/slack.atd
index 285a12b8..a977eef9 100644
--- a/lib/slack.atd
+++ b/lib/slack.atd
@@ -65,6 +65,17 @@ type post_message_req = {
 
 type post_message_res = {
   channel: string;
+  ts: string;
+}
+
+type update_message_req = {
+  inherit post_message_req;
+  ts: string;
+}
+
+type update_message_res = {
+  channel: string;
+  ts: string;
 }
 
 type link_shared_link = {
diff --git a/lib/slack.ml b/lib/slack.ml
index bb22457e..b67e4c81 100644
--- a/lib/slack.ml
+++ b/lib/slack.ml
@@ -36,7 +36,7 @@ let show_labels = function
 
 let pluralize name num suffix = if num = 1 then sprintf "%s" name else String.concat [ name; suffix ]
 
-let generate_pull_request_notification notification channel =
+let generate_pull_request_notification_content notification =
   let { action; number; sender; pull_request; repository } = notification in
   let ({ body; title; html_url; labels; merged; _ } : pull_request) = pull_request in
   let action, body =
@@ -55,28 +55,17 @@ let generate_pull_request_notification notification channel =
     sprintf "<%s|[%s]> Pull request #%d %s %s by *%s*" repository.url repository.full_name number
       (pp_link ~url:html_url title) action sender.login
   in
-  {
-    channel;
-    text = Some summary;
-    attachments =
-      Some
-        [
-          {
-            empty_attachments with
-            mrkdwn_in = Some [ "text" ];
-            color = Some "#ccc";
-            text = mrkdwn_of_markdown_opt body;
-          };
-        ];
-    blocks = None;
-  }
+  let attachments =
+    [ { empty_attachments with mrkdwn_in = Some [ "text" ]; color = Some "#ccc"; text = mrkdwn_of_markdown_opt body } ]
+  in
+  attachments, summary
 
-let generate_pr_review_notification notification channel =
+let generate_pr_review_notification_content notification =
   let { action; sender; pull_request; review; repository } = notification in
   let ({ number; title; html_url; _ } : pull_request) = pull_request in
   let action_str =
     match action with
-    | Submitted ->
+    | Submitted | Edited ->
       ( match review.state with
       | "commented" -> "commented on"
       | "approved" -> "approved"
@@ -93,28 +82,24 @@ let generate_pr_review_notification notification channel =
     sprintf "<%s|[%s]> *%s* <%s|%s> #%d %s" repository.url repository.full_name sender.login review.html_url action_str
       number (pp_link ~url:html_url title)
   in
-  {
-    channel;
-    text = Some summary;
-    attachments =
-      Some
-        [
-          {
-            empty_attachments with
-            mrkdwn_in = Some [ "text" ];
-            color = Some "#ccc";
-            text = mrkdwn_of_markdown_opt review.body;
-          };
-        ];
-    blocks = None;
-  }
+  let attachments =
+    [
+      {
+        empty_attachments with
+        mrkdwn_in = Some [ "text" ];
+        color = Some "#ccc";
+        text = mrkdwn_of_markdown_opt review.body;
+      };
+    ]
+  in
+  attachments, summary
 
-let generate_pr_review_comment_notification notification channel =
+let generate_pr_review_comment_notification_content notification =
   let { action; pull_request; sender; comment; repository } = notification in
   let ({ number; title; html_url; _ } : pull_request) = pull_request in
   let action_str =
     match action with
-    | Created -> "commented"
+    | Created | Edited -> "commented"
     | _ ->
       invalid_arg
         (sprintf "Monorobot doesn't know how to generate notification for the unexpected event %s"
@@ -130,24 +115,20 @@ let generate_pr_review_comment_notification notification channel =
     | None -> None
     | Some a -> Some (sprintf "New comment by %s in <%s|%s>" sender.login comment.html_url a)
   in
-  {
-    channel;
-    text = Some summary;
-    attachments =
-      Some
-        [
-          {
-            empty_attachments with
-            mrkdwn_in = Some [ "text" ];
-            color = Some "#ccc";
-            footer = file;
-            text = Some (mrkdwn_of_markdown comment.body);
-          };
-        ];
-    blocks = None;
-  }
+  let attachments =
+    [
+      {
+        empty_attachments with
+        mrkdwn_in = Some [ "text" ];
+        color = Some "#ccc";
+        footer = file;
+        text = Some (mrkdwn_of_markdown comment.body);
+      };
+    ]
+  in
+  attachments, summary
 
-let generate_issue_notification notification channel =
+let generate_issue_notification_content notification =
   let ({ action; sender; issue; repository } : issue_notification) = notification in
   let { number; body; title; html_url; labels; _ } = issue in
   let action, body =
@@ -166,28 +147,17 @@ let generate_issue_notification notification channel =
     sprintf "<%s|[%s]> Issue #%d %s %s by *%s*" repository.url repository.full_name number (pp_link ~url:html_url title)
       action sender.login
   in
-  {
-    channel;
-    text = Some summary;
-    attachments =
-      Some
-        [
-          {
-            empty_attachments with
-            mrkdwn_in = Some [ "text" ];
-            color = Some "#ccc";
-            text = mrkdwn_of_markdown_opt body;
-          };
-        ];
-    blocks = None;
-  }
+  let attachments =
+    [ { empty_attachments with mrkdwn_in = Some [ "text" ]; color = Some "#ccc"; text = mrkdwn_of_markdown_opt body } ]
+  in
+  attachments, summary
 
-let generate_issue_comment_notification notification channel =
+let generate_issue_comment_notification_content notification =
   let { action; issue; sender; comment; repository } = notification in
   let { number; title; _ } = issue in
   let action_str =
     match action with
-    | Created -> "commented"
+    | Created | Edited -> "commented"
     | _ ->
       invalid_arg
         (sprintf
@@ -199,21 +169,17 @@ let generate_issue_comment_notification notification channel =
     sprintf "<%s|[%s]> *%s* <%s|%s> on #%d %s" repository.url repository.full_name sender.login comment.html_url
       action_str number (pp_link ~url:issue.html_url title)
   in
-  {
-    channel;
-    text = Some summary;
-    attachments =
-      Some
-        [
-          {
-            empty_attachments with
-            mrkdwn_in = Some [ "text" ];
-            color = Some "#ccc";
-            text = Some (mrkdwn_of_markdown comment.body);
-          };
-        ];
-    blocks = None;
-  }
+  let attachments =
+    [
+      {
+        empty_attachments with
+        mrkdwn_in = Some [ "text" ];
+        color = Some "#ccc";
+        text = Some (mrkdwn_of_markdown comment.body);
+      };
+    ]
+  in
+  attachments, summary
 
 let git_short_sha_hash hash = String.sub ~pos:0 ~len:8 hash
 
@@ -245,7 +211,7 @@ let pp_list_with_previews ~pp_item list =
   end
   else List.map ~f:pp_item list
 
-let generate_push_notification notification channel =
+let generate_push_notification_content notification =
   let { sender; created; deleted; forced; compare; commits; repository; _ } = notification in
   let commits_branch = Github.commits_branch_of_ref notification.ref in
   let tree_url = String.concat ~sep:"/" [ repository.url; "tree"; Uri.pct_encode commits_branch ] in
@@ -271,23 +237,19 @@ let generate_push_notification notification channel =
         sender.login
   in
   let commits = pp_list_with_previews ~pp_item:pp_commit commits in
-  {
-    channel;
-    text = Some title;
-    attachments =
-      Some
-        [
-          {
-            empty_attachments with
-            mrkdwn_in = Some [ "fields" ];
-            color = Some "#ccc";
-            fields = Some [ { value = String.concat ~sep:"\n" commits; title = None; short = false } ];
-          };
-        ];
-    blocks = None;
-  }
+  let attachments =
+    [
+      {
+        empty_attachments with
+        mrkdwn_in = Some [ "fields" ];
+        color = Some "#ccc";
+        fields = Some [ { value = String.concat ~sep:"\n" commits; title = None; short = false } ];
+      };
+    ]
+  in
+  attachments, title
 
-let generate_status_notification (cfg : Config_t.config) (notification : status_notification) channel =
+let generate_status_notification_content (cfg : Config_t.config) (notification : status_notification) =
   let { commit; state; description; target_url; context; repository; _ } = notification in
   let ({ commit : inner_commit; sha; author; html_url; _ } : status_commit) = commit in
   let ({ message; _ } : inner_commit) = commit in
@@ -338,18 +300,20 @@ let generate_status_notification (cfg : Config_t.config) (notification : status_
         context state_info
   in
   let msg = String.concat ~sep:"\n" @@ List.concat [ commit_info; branches_info ] in
-  let attachment =
-    {
-      empty_attachments with
-      mrkdwn_in = Some [ "fields"; "text" ];
-      color = Some color_info;
-      text = description_info;
-      fields = Some [ { title = None; value = msg; short = false } ];
-    }
+  let attachments =
+    [
+      {
+        empty_attachments with
+        mrkdwn_in = Some [ "fields"; "text" ];
+        color = Some color_info;
+        text = description_info;
+        fields = Some [ { title = None; value = msg; short = false } ];
+      };
+    ]
   in
-  { channel; text = Some summary; attachments = Some [ attachment ]; blocks = None }
+  attachments, summary
 
-let generate_commit_comment_notification api_commit notification channel =
+let generate_commit_comment_notification_content api_commit notification =
   let { commit; _ } = api_commit in
   let { sender; comment; repository; _ } = notification in
   let commit_id =
@@ -367,16 +331,28 @@ let generate_commit_comment_notification api_commit notification channel =
     | None -> None
     | Some p -> Some (sprintf "New comment by %s in <%s|%s>" sender.login comment.html_url p)
   in
-  let attachment =
-    {
-      empty_attachments with
-      mrkdwn_in = Some [ "pretext"; "text" ];
-      color = Some "#ccc";
-      footer = path;
-      text = Some (mrkdwn_of_markdown comment.body);
-    }
+  let attachments =
+    [
+      {
+        empty_attachments with
+        mrkdwn_in = Some [ "pretext"; "text" ];
+        color = Some "#ccc";
+        footer = path;
+        text = Some (mrkdwn_of_markdown comment.body);
+      };
+    ]
   in
-  { channel; text = Some summary; attachments = Some [ attachment ]; blocks = None }
+  attachments, summary
+
+type send_notification_mode =
+  | New_message of Slack_t.post_message_req
+  | Update_message of Slack_t.update_message_req
+
+let generate_new_message (attachments, summary) channel =
+  New_message { channel; text = Some summary; attachments = Some attachments; blocks = None }
+
+let generate_update_message (attachments, summary) ~ts channel =
+  Update_message { channel; ts; text = Some summary; attachments = Some attachments; blocks = None }
 
 let validate_signature ?(version = "v0") ?signing_key ~headers body =
   match signing_key with
diff --git a/lib/state.atd b/lib/state.atd
index 86b18f06..5f73e78a 100644
--- a/lib/state.atd
+++ b/lib/state.atd
@@ -10,13 +10,21 @@ type branch_statuses = status_state map_as_object
    branch *)
 type pipeline_statuses = branch_statuses map_as_object
 
+type ts_map = string map_as_object
+type issue_state = {
+  comments <ocaml mutable>: ts_map;
+  reviews <ocaml mutable>: ts_map;
+}
+
 (* The runtime state of a given GitHub repository *)
 type repo_state = {
-  pipeline_statuses <ocaml mutable>: pipeline_statuses
+  pipeline_statuses <ocaml mutable>: pipeline_statuses;
+  (* issue number is the same as PR number for github APIs *)
+  issue_tbl <ocaml mutable>: issue_state table_as_object;
 }
 
 (* The serializable runtime state of the bot *)
 type state = {
   repos : repo_state table_as_object;
   ?bot_user_id <ocaml mutable>: string nullable;
-}
\ No newline at end of file
+}
diff --git a/lib/state.ml b/lib/state.ml
index 6a53f361..c3e9db7d 100644
--- a/lib/state.ml
+++ b/lib/state.ml
@@ -7,7 +7,8 @@ type t = {
   lock : Lwt_mutex.t;  (** protect access to mutable string map `pipeline_statuses` *)
 }
 
-let empty_repo_state () : State_t.repo_state = { pipeline_statuses = StringMap.empty }
+let empty_repo_state () : State_t.repo_state = { pipeline_statuses = StringMap.empty; issue_tbl = Stringtbl.empty () }
+let empty_issue_state () : State_t.issue_state = { comments = StringMap.empty; reviews = StringMap.empty }
 
 let empty () : t =
   let state = State_t.{ repos = Stringtbl.empty (); bot_user_id = None } in
@@ -15,6 +16,9 @@ let empty () : t =
 
 let find_or_add_repo' state repo_url = Stringtbl.find_or_add state.State_t.repos repo_url ~default:empty_repo_state
 
+let find_or_add_issue' (repo_state : State_t.repo_state) issue_num =
+  Stringtbl.find_or_add repo_state.issue_tbl (Int.to_string issue_num) ~default:empty_issue_state
+
 let set_repo_state { state; lock } repo_url repo_state =
   Lwt_mutex.with_lock lock @@ fun () ->
   Stringtbl.set state.repos ~key:repo_url ~data:repo_state;
@@ -34,6 +38,36 @@ let set_repo_pipeline_status { state; lock } repo_url ~pipeline ~(branches : Git
   repo_state.pipeline_statuses <- Map.update repo_state.pipeline_statuses pipeline ~f:set_branch_status;
   Lwt.return_unit
 
+let add_comment_msg { state; lock } repo_url ~issue_num comment_id post_message_res =
+  Lwt_mutex.with_lock lock @@ fun () ->
+  let repo_state = find_or_add_repo' state repo_url in
+  let issue_tbl = find_or_add_issue' repo_state issue_num in
+  issue_tbl.comments <- Map.set issue_tbl.comments ~key:(Int.to_string comment_id) ~data:post_message_res;
+  Lwt.return_unit
+
+let get_comment_msg { state; _ } repo_url ~issue_num comment_id =
+  let repo_state = find_or_add_repo' state repo_url in
+  let issue_tbl = find_or_add_issue' repo_state issue_num in
+  Map.find issue_tbl.comments (Int.to_string comment_id)
+
+let add_review_msg { state; lock } repo_url ~issue_num review_id post_message_res =
+  Lwt_mutex.with_lock lock @@ fun () ->
+  let repo_state = find_or_add_repo' state repo_url in
+  let issue_tbl = find_or_add_issue' repo_state issue_num in
+  issue_tbl.reviews <- Map.set issue_tbl.reviews ~key:(Int.to_string review_id) ~data:post_message_res;
+  Lwt.return_unit
+
+let get_review_msg { state; _ } repo_url ~issue_num review_id =
+  let repo_state = find_or_add_repo' state repo_url in
+  let issue_tbl = find_or_add_issue' repo_state issue_num in
+  Map.find issue_tbl.reviews (Int.to_string review_id)
+
+let close_issue { state; lock } repo_url issue_num =
+  Lwt_mutex.with_lock lock @@ fun () ->
+  let repo_state = find_or_add_repo' state repo_url in
+  Stringtbl.remove repo_state.issue_tbl (Int.to_string issue_num);
+  Lwt.return_unit
+
 let set_bot_user_id { state; _ } user_id = state.State_t.bot_user_id <- Some user_id
 let get_bot_user_id { state; _ } = state.State_t.bot_user_id
 let log = Log.from "state"
diff --git a/mock_states/issue_comment.edited.json b/mock_states/issue_comment.edited.json
new file mode 100644
index 00000000..b127ac8b
--- /dev/null
+++ b/mock_states/issue_comment.edited.json
@@ -0,0 +1,21 @@
+
+{
+    "pipeline_statuses": {
+        "default": {
+            "master": "failure"
+        },
+        "buildkite/pipeline2": {
+            "master": "success"
+        }
+    },
+    "issue_tbl" : {
+        "4" : {
+            "comments": {
+                "0": "1.00"
+            },
+            "reviews": {
+                "0": "2.00"
+            }
+        }
+    }
+}
diff --git a/mock_states/pull_request_review.edited.json b/mock_states/pull_request_review.edited.json
new file mode 100644
index 00000000..7834820b
--- /dev/null
+++ b/mock_states/pull_request_review.edited.json
@@ -0,0 +1,21 @@
+
+{
+    "pipeline_statuses": {
+        "default": {
+            "master": "failure"
+        },
+        "buildkite/pipeline2": {
+            "master": "success"
+        }
+    },
+    "issue_tbl" : {
+        "4": {
+            "comments": {
+                "0": "1.00"
+            },
+            "reviews": {
+                "0": "2.00"
+            }
+        }
+    }
+}
diff --git a/mock_states/pull_request_review_comment.edited.json b/mock_states/pull_request_review_comment.edited.json
new file mode 100644
index 00000000..7834820b
--- /dev/null
+++ b/mock_states/pull_request_review_comment.edited.json
@@ -0,0 +1,21 @@
+
+{
+    "pipeline_statuses": {
+        "default": {
+            "master": "failure"
+        },
+        "buildkite/pipeline2": {
+            "master": "success"
+        }
+    },
+    "issue_tbl" : {
+        "4": {
+            "comments": {
+                "0": "1.00"
+            },
+            "reviews": {
+                "0": "2.00"
+            }
+        }
+    }
+}
diff --git a/mock_states/status.state_hide_success_test.json b/mock_states/status.state_hide_success_test.json
index 0a4b7dec..7834820b 100644
--- a/mock_states/status.state_hide_success_test.json
+++ b/mock_states/status.state_hide_success_test.json
@@ -1,11 +1,21 @@
 
 {
-  "pipeline_statuses": {
-    "default": {
-      "master": "failure"
+    "pipeline_statuses": {
+        "default": {
+            "master": "failure"
+        },
+        "buildkite/pipeline2": {
+            "master": "success"
+        }
     },
-    "buildkite/pipeline2": {
-      "master": "success"
+    "issue_tbl" : {
+        "4": {
+            "comments": {
+                "0": "1.00"
+            },
+            "reviews": {
+                "0": "2.00"
+            }
+        }
     }
-  }
-}
\ No newline at end of file
+}
diff --git a/mock_states/status.state_hide_success_test_disallowed_pipeline.json b/mock_states/status.state_hide_success_test_disallowed_pipeline.json
index 25b4592a..f85336ab 100644
--- a/mock_states/status.state_hide_success_test_disallowed_pipeline.json
+++ b/mock_states/status.state_hide_success_test_disallowed_pipeline.json
@@ -1,7 +1,17 @@
 {
-  "pipeline_statuses": {
-    "buildkite/pipeline2": {
-      "master": "failure"
+    "pipeline_statuses": {
+        "buildkite/pipeline2": {
+            "master": "failure"
+        }
+    },
+    "issue_tbl" : {
+        "4": {
+            "comments": {
+                "0": "1.00"
+            },
+            "reviews": {
+                "0": "2.00"
+            }
+        }
     }
-  }
-}
\ No newline at end of file
+}
diff --git a/src/monorobot.ml b/src/monorobot.ml
index b4aa1394..7fa9e6e6 100644
--- a/src/monorobot.ml
+++ b/src/monorobot.ml
@@ -57,7 +57,7 @@ let check_slack_action file secrets =
       | Error e ->
         log#error "%s" e;
         Lwt.return_unit
-      | Ok () -> Lwt.return_unit
+      | Ok (_res : Slack_t.post_message_res) -> Lwt.return_unit
       )
 
 (* flags *)
diff --git a/test/slack_payloads.expected b/test/slack_payloads.expected
index 1e3c84fe..d8ec7477 100644
--- a/test/slack_payloads.expected
+++ b/test/slack_payloads.expected
@@ -171,6 +171,34 @@ will notify #frontend-bot
   ]
 }
 ===== file ../mock_payloads/issue_comment.edited.json =====
+will update msg in #a1-bot
+{
+  "channel": "a1-bot",
+  "text": "<https://github.com/xinyuluo/monorepo|[xinyuluo/monorepo]> *xinyuluo* <https://github.com/xinyuluo/monorepo/pull/4#issuecomment-633344369|commented> on #4 <https://github.com/xinyuluo/monorepo/pull/4|README update>",
+  "attachments": [
+    {
+      "fallback": null,
+      "mrkdwn_in": [ "text" ],
+      "color": "#ccc",
+      "text": "issue comment edited test"
+    }
+  ],
+  "ts": "1.00"
+}
+will update msg in #backend
+{
+  "channel": "backend",
+  "text": "<https://github.com/xinyuluo/monorepo|[xinyuluo/monorepo]> *xinyuluo* <https://github.com/xinyuluo/monorepo/pull/4#issuecomment-633344369|commented> on #4 <https://github.com/xinyuluo/monorepo/pull/4|README update>",
+  "attachments": [
+    {
+      "fallback": null,
+      "mrkdwn_in": [ "text" ],
+      "color": "#ccc",
+      "text": "issue comment edited test"
+    }
+  ],
+  "ts": "1.00"
+}
 ===== file ../mock_payloads/issues.closed.json =====
 will notify #backend
 {
@@ -307,6 +335,34 @@ will notify #frontend-bot
 }
 ===== file ../mock_payloads/pull_request_review.dismissed.json =====
 ===== file ../mock_payloads/pull_request_review.edited.json =====
+will update msg in #a1-bot
+{
+  "channel": "a1-bot",
+  "text": "<https://github.com/xinyuluo/monorepo|[xinyuluo/monorepo]> *xinyuluo* <https://github.com/xinyuluo/monorepo/pull/4#pullrequestreview-0|commented on> #4 <https://github.com/xinyuluo/monorepo/pull/4|README update>",
+  "attachments": [
+    {
+      "fallback": null,
+      "mrkdwn_in": [ "text" ],
+      "color": "#ccc",
+      "text": "pr review comment test"
+    }
+  ],
+  "ts": "2.00"
+}
+will update msg in #backend
+{
+  "channel": "backend",
+  "text": "<https://github.com/xinyuluo/monorepo|[xinyuluo/monorepo]> *xinyuluo* <https://github.com/xinyuluo/monorepo/pull/4#pullrequestreview-0|commented on> #4 <https://github.com/xinyuluo/monorepo/pull/4|README update>",
+  "attachments": [
+    {
+      "fallback": null,
+      "mrkdwn_in": [ "text" ],
+      "color": "#ccc",
+      "text": "pr review comment test"
+    }
+  ],
+  "ts": "2.00"
+}
 ===== file ../mock_payloads/pull_request_review.request_changes.json =====
 will notify #default
 {
@@ -354,6 +410,36 @@ will notify #backend
 }
 ===== file ../mock_payloads/pull_request_review_comment.deleted.json =====
 ===== file ../mock_payloads/pull_request_review_comment.edited.json =====
+will update msg in #a1-bot
+{
+  "channel": "a1-bot",
+  "text": "<https://github.com/xinyuluo/monorepo|[xinyuluo/monorepo]> *xinyuluo* commented on #4 <https://github.com/xinyuluo/monorepo/pull/4|README update>",
+  "attachments": [
+    {
+      "fallback": null,
+      "mrkdwn_in": [ "text" ],
+      "color": "#ccc",
+      "text": "Edited test comment",
+      "footer": "New comment by xinyuluo in <https://github.com/xinyuluo/monorepo/pull/4#discussion_r0|README.md>"
+    }
+  ],
+  "ts": "1.00"
+}
+will update msg in #backend
+{
+  "channel": "backend",
+  "text": "<https://github.com/xinyuluo/monorepo|[xinyuluo/monorepo]> *xinyuluo* commented on #4 <https://github.com/xinyuluo/monorepo/pull/4|README update>",
+  "attachments": [
+    {
+      "fallback": null,
+      "mrkdwn_in": [ "text" ],
+      "color": "#ccc",
+      "text": "Edited test comment",
+      "footer": "New comment by xinyuluo in <https://github.com/xinyuluo/monorepo/pull/4#discussion_r0|README.md>"
+    }
+  ],
+  "ts": "1.00"
+}
 ===== file ../mock_payloads/push.branch_filter_default.json =====
 will notify #all-push-events
 {
diff --git a/test/test.ml b/test/test.ml
index e7f0df93..d169ad8f 100644
--- a/test/test.ml
+++ b/test/test.ml
@@ -27,52 +27,60 @@ let get_mock_slack_events () =
 
 let process_gh_payload ~(secrets : Config_t.secrets) ~config (kind, path, state_path) =
   let headers = [ "x-github-event", kind ] in
-  let make_test_context event =
-    let repo = Github.repo_of_notification @@ Github.parse_exn headers event in
-    (* overwrite repo url in secrets with that of notification for this test case *)
-    let secrets = { secrets with repos = [ { url = repo.url; gh_token = None; gh_hook_token = None } ] } in
-    let ctx = Context.make () in
-    ctx.secrets <- Some secrets;
-    let%lwt _ = State.find_or_add_repo ctx.state repo.url in
-    match state_path with
-    | None ->
-      Context.set_repo_config ctx repo.url config;
-      Lwt.return ctx
-    | Some state_path ->
-    match Common.get_local_file state_path with
-    | Error e ->
-      log#error "failed to read %s: %s" state_path e;
-      Lwt.return ctx
-    | Ok file ->
-      let repo_state = State_j.repo_state_of_string file in
-      let%lwt () = State.set_repo_state ctx.state repo.url repo_state in
-      Context.set_repo_config ctx repo.url config;
-      Lwt.return ctx
-  in
-  Stdio.printf "===== file %s =====\n" path;
-  let headers = [ "x-github-event", kind ] in
-  match Common.get_local_file path with
-  | Error e -> Lwt.return @@ log#error "failed to read %s: %s" path e
-  | Ok event ->
-    let%lwt ctx = make_test_context event in
-    let%lwt _ctx = Action_local.process_github_notification ctx headers event in
-    Lwt.return_unit
+  try%lwt
+    let make_test_context event =
+      let repo = Github.repo_of_notification @@ Github.parse_exn headers event in
+      (* overwrite repo url in secrets with that of notification for this test case *)
+      let secrets = { secrets with repos = [ { url = repo.url; gh_token = None; gh_hook_token = None } ] } in
+      let ctx = Context.make () in
+      ctx.secrets <- Some secrets;
+      let%lwt _ = State.find_or_add_repo ctx.state repo.url in
+      match state_path with
+      | None ->
+        Context.set_repo_config ctx repo.url config;
+        Lwt.return ctx
+      | Some state_path ->
+      match Common.get_local_file state_path with
+      | Error e ->
+        log#error "failed to read %s: %s" state_path e;
+        Lwt.return ctx
+      | Ok file ->
+        let repo_state = State_j.repo_state_of_string file in
+        let%lwt () = State.set_repo_state ctx.state repo.url repo_state in
+        Context.set_repo_config ctx repo.url config;
+        Lwt.return ctx
+    in
+    Stdio.printf "===== file %s =====\n" path;
+    let headers = [ "x-github-event", kind ] in
+    match Common.get_local_file path with
+    | Error e -> Lwt.return @@ log#error "failed to read %s: %s" path e
+    | Ok event ->
+      let%lwt ctx = make_test_context event in
+      let%lwt _ctx = Action_local.process_github_notification ctx headers event in
+      Lwt.return_unit
+  with exn ->
+    log#error ~exn "failed to run github payload test from %s" path;
+    Caml.exit 1
 
 let process_slack_event ~(secrets : Config_t.secrets) path =
-  let ctx = Context.make () in
-  ctx.secrets <- Some secrets;
-  State.set_bot_user_id ctx.state "bot_user";
-  Stdio.printf "===== file %s =====\n" path;
-  match Common.get_local_file path with
-  | Error e -> Lwt.return @@ log#error "failed to read %s: %s" path e
-  | Ok body ->
-  match Slack_j.event_notification_of_string body with
-  | Url_verification _ -> Lwt.return ()
-  | Event_callback notification ->
-  match notification.event with
-  | Link_shared event ->
-    let%lwt _ctx = Action_local.process_link_shared_event ctx event in
-    Lwt.return_unit
+  try%lwt
+    let ctx = Context.make () in
+    ctx.secrets <- Some secrets;
+    State.set_bot_user_id ctx.state "bot_user";
+    Stdio.printf "===== file %s =====\n" path;
+    match Common.get_local_file path with
+    | Error e -> Lwt.return @@ log#error "failed to read %s: %s" path e
+    | Ok body ->
+    match Slack_j.event_notification_of_string body with
+    | Url_verification _ -> Lwt.return ()
+    | Event_callback notification ->
+    match notification.event with
+    | Link_shared event ->
+      let%lwt _ctx = Action_local.process_link_shared_event ctx event in
+      Lwt.return_unit
+  with exn ->
+    log#error ~exn "failed to run slack unfurl test from %s" path;
+    Caml.exit 1
 
 let () =
   let payloads = get_mock_payloads () in