diff --git a/Project.toml b/Project.toml
index e926c8d1f..c809c13c2 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "SciMLBase"
 uuid = "0bca4576-84f4-4d90-8ffe-ffa030f20462"
 authors = ["Chris Rackauckas <accounts@chrisrackauckas.com> and contributors"]
-version = "2.63.1"
+version = "2.64.0"
 
 [deps]
 ADTypes = "47edcb42-4c32-4615-8424-f2b9edc5f35b"
diff --git a/docs/src/interfaces/Solutions.md b/docs/src/interfaces/Solutions.md
index 5c25e31f7..61723742b 100644
--- a/docs/src/interfaces/Solutions.md
+++ b/docs/src/interfaces/Solutions.md
@@ -81,6 +81,7 @@ SciMLBase.ReturnCode.Success
 SciMLBase.ReturnCode.Terminated
 SciMLBase.ReturnCode.DtNaN
 SciMLBase.ReturnCode.MaxIters
+SciMLBase.ReturnCode.MaxNumSub
 SciMLBase.ReturnCode.DtLessThanMin
 SciMLBase.ReturnCode.Unstable
 SciMLBase.ReturnCode.InitialFailure
diff --git a/src/retcodes.jl b/src/retcodes.jl
index 0910331b5..8bf2409d0 100644
--- a/src/retcodes.jl
+++ b/src/retcodes.jl
@@ -149,6 +149,26 @@ EnumX.@enumx ReturnCode begin
     """
     MaxIters
 
+    """
+        ReturnCode.MaxNumSub
+
+    A failure exit state of the solver. If this return code is given, then the
+    solving process was unsuccessful and exited early because during the solver's
+    adaptivity, mesh length exceeded the `max_num_subintervals` either set by default or specified
+    by users in the solver.
+
+    ## Common Reasons for Seeing this Return Code
+
+      - This commonly occurs in BVP solving if the original mesh are too coarse or
+        the tolerance are too stringent. It is recommended that in such cases, one tries to increase the default `max_num_subintervals`
+        in solvers, or decrease the tolerance.
+
+    ## Properties
+
+      - `successful_retcode` = `false`
+    """
+    MaxNumSub
+
     """
         ReturnCode.DtLessThanMin
 
@@ -417,6 +437,8 @@ function Base.convert(::Type{ReturnCode.T}, retcode::Symbol)
         ReturnCode.Terminated
     elseif retcode == :MaxIters || retcode == :MAXITERS_EXCEED
         ReturnCode.MaxIters
+    elseif retcode == :MaxNumSub
+        ReturnCode.MaxNumSub
     elseif retcode == :MaxTime || retcode == :TIME_LIMIT
         ReturnCode.MaxTime
     elseif retcode == :DtLessThanMin