diff --git a/doc/ChangeLog b/doc/ChangeLog
index 6b19a2747b..e23086464c 100644
--- a/doc/ChangeLog
+++ b/doc/ChangeLog
@@ -1,4 +1,60 @@
 ===============================================================
+Tag name: ctsm5.3.066
+Originator(s): slevis (Samuel Levis,UCAR/TSS,303-665-1310)
+Date: Fri 08 Aug 2025 09:19:34 AM MDT
+One-line Summary: Merge b4b-dev to master
+
+Purpose and description of changes
+----------------------------------
+
+ PR #3395 making this tag includes:
+ #3352 Add Fang Li's abm and popden .ncl scripts to /tools/contrib
+ #3395 Add to README.CHECKLIST.master_tags a new reminder:
+ "When izumi’s baseline is ready, open read permissions to all"
+
+Significant changes to scientifically-supported configurations
+--------------------------------------------------------------
+
+Does this tag change answers significantly for any of the following physics configurations?
+(Details of any changes will be given in the "Answer changes" section below.)
+
+    [Put an [X] in the box for any configuration with significant answer changes.]
+
+[ ] clm6_0
+
+[ ] clm5_0
+
+[ ] ctsm5_0-nwp
+
+[ ] clm4_5
+
+
+Bugs fixed
+----------
+List of CTSM issues fixed (include CTSM Issue # and description) [one per line]:
+ Addresses part of #2701 New population dataset for streams files
+
+Testing summary:
+----------------
+
+ [PASS means all tests PASS; OK means tests PASS other than expected fails.]
+
+  regular tests (aux_clm: https://github.com/ESCOMP/CTSM/wiki/System-Testing-Guide#pre-merge-system-testing):
+
+    derecho ----- OK (running aux_clm was redundant given the type of code changes)
+    izumi ------- OK
+
+Answer changes
+--------------
+Changes answers relative to baseline: No
+
+Other details
+-------------
+Pull Requests that document the changes (include PR ids):
+ https://github.com/ESCOMP/ctsm/pull/3395
+
+===============================================================
+===============================================================
 Tag name: ctsm5.3.065
 Originator(s): erik (Erik Kluzek,UCAR/TSS,303-497-1326)
 Date: Mon 28 Jul 2025 09:30:35 AM MDT
diff --git a/doc/ChangeSum b/doc/ChangeSum
index 20b0a8f534..1c58119a9b 100644
--- a/doc/ChangeSum
+++ b/doc/ChangeSum
@@ -1,5 +1,6 @@
 Tag                   Who      Date  Summary
 ============================================================================================================================
+       ctsm5.3.066   slevis 08/08/2025 Merge b4b-dev to master
        ctsm5.3.065     erik 07/28/2025 Merge b4b-dev to master
        ctsm5.3.064   slevis 07/24/2025 Add time dimension to 1d_wt fields in transient runs
        ctsm5.3.063 samrabin 07/10/2025 Merge b4b-dev to master
diff --git a/doc/README.CHECKLIST.master_tags b/doc/README.CHECKLIST.master_tags
index 51386c4238..5e6d44ad14 100644
--- a/doc/README.CHECKLIST.master_tags
+++ b/doc/README.CHECKLIST.master_tags
@@ -86,6 +86,7 @@ if you did step 7 above using git commands that require this step)
 
 ---- NOTES ----
 
-(3) -- Always test on your fork with a feature-branch so that we can change tag order if needed. Put 
+(3a) -- When izumi’s baseline is ready, manually open read permissions to all.
+(3b) -- Always test on your fork with a feature-branch so that we can change tag order if needed. Put 
 baselines in the next tag name, as we can easily change afterwards if needed.