diff --git a/.obsidian/workspace b/.obsidian/workspace
index cb8b5286f..a27c4a5c8 100644
--- a/.obsidian/workspace
+++ b/.obsidian/workspace
@@ -10,7 +10,7 @@
           {
             "id": "1c3e63745fbefd6f",
             "type": "leaf",
-            "dimension": 50.73891625615764,
+            "dimension": 25.36945812807882,
             "state": {
               "type": "markdown",
               "state": {
@@ -19,6 +19,18 @@
               }
             }
           },
+          {
+            "id": "434bd4c7c42b00d5",
+            "type": "leaf",
+            "dimension": 25.36945812807882,
+            "state": {
+              "type": "markdown",
+              "state": {
+                "file": "ack.md",
+                "mode": "source"
+              }
+            }
+          },
           {
             "id": "d407fbfa22a48bda",
             "type": "split",
@@ -153,7 +165,7 @@
             "state": {
               "type": "backlink",
               "state": {
-                "file": "do.md",
+                "file": "ack.md",
                 "collapseAll": false,
                 "extraContext": false,
                 "sortOrder": "alphabetical",
@@ -170,7 +182,7 @@
             "state": {
               "type": "outline",
               "state": {
-                "file": "do.md"
+                "file": "ack.md"
               }
             }
           },
@@ -226,8 +238,9 @@
     "width": 300,
     "collapsed": true
   },
-  "active": "1c3e63745fbefd6f",
+  "active": "434bd4c7c42b00d5",
   "lastOpenFiles": [
+    "ack.md",
     "do.md",
     "pomodoro.md",
     "a. p..md",
@@ -236,7 +249,6 @@
     "rusp.md",
     "orgzly.md",
     "logseq.md",
-    "hyperknowledge.md",
-    "Untitled 4.md"
+    "hyperknowledge.md"
   ]
 }
\ No newline at end of file
diff --git a/ack.md b/ack.md
new file mode 100644
index 000000000..8030c50ca
--- /dev/null
+++ b/ack.md
@@ -0,0 +1,2 @@
+- an [[agora action]]
+	- [[ack]] is a complement to [[push]]. node b can [[ack]] an incoming push from node a by [[ack]]
\ No newline at end of file
diff --git a/do.md b/do.md
index d5091348c..d66832a13 100644
--- a/do.md
+++ b/do.md
@@ -63,7 +63,7 @@
 			- a more flexible [[actions]] system
 - Please tell me what you think I should do next below or via any of the channels listed in [[flancian]]. All feedback is welcome!
 - [[push]] [[done]]
-	- implement [[push gc]]
+	- implement [[ack]]
 	- [[agora yaml]]
 	- [[agora plan]]
 	- [[rdf]]