diff --git a/README.md b/README.md
index 60575c7..52a586e 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,8 @@ pip install itp-interface
 ```
 
 2. Run the following command to prepare the REPL for Lean 4. The default version is 4.24.0. You can change the version by setting the `LEAN_VERSION` environment variable. If no version is set, then 4.24.0 is used.
->NOTE: The Lean 4 version must match the version of the Lean 4 project you are working with.
+>NOTE: The Lean 4 version must match the version of the Lean 4 project you are working with. `itp-interface` **supports Lean 4 version >= 4.15.0 and <= 4.24.0**. (It has been tested till version 4.24.0, but might as well work for future versions too, if the future versions are completely backwards-compatible).
+
 ```bash
 install-lean-repl
 # To use a different Lean version, set LEAN_VERSION before running:
diff --git a/pyproject.toml b/pyproject.toml
index e018019..924e11b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ requires = [
 build-backend = "hatchling.build"
 [project]
 name = "itp_interface"
-version = "1.1.15"
+version = "1.1.16"
 authors = [
   { name="Amitayush Thakur", email="amitayush@utexas.edu" },
 ]
diff --git a/src/itp_interface/main/install.py b/src/itp_interface/main/install.py
index c6e8222..e375f57 100644
--- a/src/itp_interface/main/install.py
+++ b/src/itp_interface/main/install.py
@@ -1,10 +1,15 @@
 import os
 import random
 import string
+import logging
+import traceback
 from itp_interface.tools.tactic_parser import build_tactic_parser_if_needed
 
 file_path = os.path.abspath(__file__)
 
+logging.basicConfig(level=logging.INFO)
+# Create a console logger
+logger = logging.getLogger(__name__)
 
 def generate_random_string(length, allowed_chars=None):
     if allowed_chars is None:
@@ -25,7 +30,12 @@ def install_itp_interface():
     print("Lean toolchain version for tactic_parser: ", lean_toolchain_content)
     print(f"LEAN_VERSION set: {os.environ.get('LEAN_VERSION', 'Not Set')}")
     print("Building itp_interface")
-    build_tactic_parser_if_needed()
+    try:
+        build_tactic_parser_if_needed(logger)
+    except Exception:
+        # print the stack trace
+        traceback.print_exc()
+        raise
 
 def install_lean_repl():
     print("Updating Lean")
diff --git a/src/itp_interface/tools/dynamic_lean4_proof_exec.py b/src/itp_interface/tools/dynamic_lean4_proof_exec.py
index 1d51f67..53eb19e 100644
--- a/src/itp_interface/tools/dynamic_lean4_proof_exec.py
+++ b/src/itp_interface/tools/dynamic_lean4_proof_exec.py
@@ -159,12 +159,12 @@ def cancel_tactic_till_line(self, tactic_line_num: int, no_backtracking: bool =
                 if line_num >= tactic_line_num:
                     del self.run_state.line_tactic_map[line_num]
             line_proof_context_map_keys = list(self.run_state.line_proof_context_map.keys())
-            for line_num in line_proof_context_map_keys:
-                if line_num >= tactic_line_num:
-                    del self.run_state.line_proof_context_map[line_num]
             if not no_backtracking:
                 self.proof_context = self.run_state.line_proof_context_map[tactic_line_num]
                 self.line_num = tactic_line_num
                 cancelled_some_tactics = self._backtrack_tactic_line(tactic_line_num)
                 self._proof_running = self.proof_context is not None
+            for line_num in line_proof_context_map_keys:
+                if line_num >= tactic_line_num:
+                    del self.run_state.line_proof_context_map[line_num]
         return cancelled_some_tactics
\ No newline at end of file
diff --git a/src/itp_interface/tools/tactic_parser.py b/src/itp_interface/tools/tactic_parser.py
index bf9638d..047c55e 100644
--- a/src/itp_interface/tools/tactic_parser.py
+++ b/src/itp_interface/tools/tactic_parser.py
@@ -249,35 +249,6 @@ class FileDependencyAnalysis(BaseModel):
     def __repr__(self) -> str:
         return f"FileDependencyAnalysis({self.module_name}, {len(self.declarations)} decls)"
 
-    # def to_dict(self) -> Dict:
-    #     """Convert to dictionary matching the JSON format."""
-    #     return {
-    #         "filePath": self.file_path,
-    #         "moduleName": self.module_name,
-    #         "imports": self.imports,
-    #         "declarations": [
-    #             {
-    #                 "declaration": decl.declaration.to_dict(),
-    #                 "dependencies": [dep.model_dump(exclude_none=True) for dep in decl.dependencies],
-    #                 "unresolvedNames": decl.unresolved_names,
-    #                 **({"declId": decl.decl_id} if decl.decl_id else {})
-    #             }
-    #             for decl in self.declarations
-    #         ]
-    #     }
-
-    # @staticmethod
-    # def from_dict(data: Dict) -> 'FileDependencyAnalysis':
-    #     """Parse from the JSON dict returned by dependency-parser executable."""
-    #     declarations = DeclWithDependencies.from_dependency_analysis(data)
-
-    #     return FileDependencyAnalysis(
-    #         file_path=data['filePath'],
-    #         module_name=data['moduleName'],
-    #         imports=data.get('imports', []),
-    #         declarations=declarations
-    #     )
-
 # Create an enum for parsing request type
 class RequestType(Enum):
     PARSE_TACTICS = "parse_tactics"
diff --git a/src/itp_interface/tools/tactic_parser/TacticParser/Base64.lean b/src/itp_interface/tools/tactic_parser/TacticParser/Base64.lean
index 7e8f02b..786c87f 100644
--- a/src/itp_interface/tools/tactic_parser/TacticParser/Base64.lean
+++ b/src/itp_interface/tools/tactic_parser/TacticParser/Base64.lean
@@ -25,49 +25,50 @@ def charToValue (c : Char) : Option UInt8 :=
   else
     none
 
-/-- Decode a base64 string to bytes -/
-def decodeBytes (s : String) : Except String ByteArray :=
-  let chars := s.trim.toList.filter (· ≠ '=')
-  let rec loop (i : Nat) (result : ByteArray) : Except String ByteArray :=
-    if i >= chars.length then
-      .ok result
-    else
-      -- Get 4 characters (or remaining)
-      let c1 := chars[i]!
-      let c2 := if i + 1 < chars.length then chars[i + 1]! else '='
-      let c3 := if i + 2 < chars.length then chars[i + 2]! else '='
-      let c4 := if i + 3 < chars.length then chars[i + 3]! else '='
+partial def loop (i : Nat) (result : ByteArray) (chars : List Char) : Except String ByteArray :=
+  if i >= chars.length then
+    .ok result
+  else
+    -- Get 4 characters (or remaining)
+    let c1 := chars[i]!
+    let c2 := if i + 1 < chars.length then chars[i + 1]! else '='
+    let c3 := if i + 2 < chars.length then chars[i + 2]! else '='
+    let c4 := if i + 3 < chars.length then chars[i + 3]! else '='
 
-      match Option.toExcept (charToValue c1) "Invalid base64 character" with
+    match Option.toExcept (charToValue c1) "Invalid base64 character" with
+    | .error e => .error e
+    | .ok v1 =>
+      match Option.toExcept (charToValue c2) "Invalid base64 character" with
       | .error e => .error e
-      | .ok v1 =>
-        match Option.toExcept (charToValue c2) "Invalid base64 character" with
-        | .error e => .error e
-        | .ok v2 =>
-          -- First byte is always present
-          let b1 := (v1.toNat <<< 2 ||| (v2.toNat >>> 4)).toUInt8
-          let result := result.push b1
+      | .ok v2 =>
+        -- First byte is always present
+        let b1 := (v1.toNat <<< 2 ||| (v2.toNat >>> 4)).toUInt8
+        let result := result.push b1
 
-          -- Second byte if c3 exists
-          if c3 ≠ '=' then
-            match Option.toExcept (charToValue c3) "Invalid base64 character" with
-            | .error e => .error e
-            | .ok v3 =>
-              let b2 := ((v2.toNat &&& 0xF) <<< 4 ||| (v3.toNat >>> 2)).toUInt8
-              let result := result.push b2
+        -- Second byte if c3 exists
+        if c3 ≠ '=' then
+          match Option.toExcept (charToValue c3) "Invalid base64 character" with
+          | .error e => .error e
+          | .ok v3 =>
+            let b2 := ((v2.toNat &&& 0xF) <<< 4 ||| (v3.toNat >>> 2)).toUInt8
+            let result := result.push b2
 
-              -- Third byte if c4 exists
-              if c4 ≠ '=' then
-                match Option.toExcept (charToValue c4) "Invalid base64 character" with
-                | .error e => .error e
-                | .ok v4 =>
-                  let b3 := ((v3.toNat &&& 0x3) <<< 6 ||| v4.toNat).toUInt8
-                  loop (i + 4) (result.push b3)
-              else
-                loop (i + 4) result
-          else
-            loop (i + 4) result
-  loop 0 ByteArray.empty
+            -- Third byte if c4 exists
+            if c4 ≠ '=' then
+              match Option.toExcept (charToValue c4) "Invalid base64 character" with
+              | .error e => .error e
+              | .ok v4 =>
+                let b3 := ((v3.toNat &&& 0x3) <<< 6 ||| v4.toNat).toUInt8
+                loop (i + 4) (result.push b3) chars
+            else
+              loop (i + 4) result chars
+        else
+          loop (i + 4) result chars
+
+/-- Decode a base64 string to bytes -/
+def decodeBytes (s : String) : Except String ByteArray :=
+  let chars := s.trim.toList.filter (· ≠ '=')
+  loop 0 ByteArray.empty chars
 
 /-- Decode a base64 string to UTF-8 string -/
 def decode (s : String) : Except String String := do
diff --git a/src/itp_interface/tools/tactic_parser/TacticParser/DependencyParser.lean b/src/itp_interface/tools/tactic_parser/TacticParser/DependencyParser.lean
index 5cb9479..4e9cd0a 100644
--- a/src/itp_interface/tools/tactic_parser/TacticParser/DependencyParser.lean
+++ b/src/itp_interface/tools/tactic_parser/TacticParser/DependencyParser.lean
@@ -150,6 +150,31 @@ def extractDependenciesFromSyntax (env : Environment) (stx : Syntax) : Array Dec
     | none => (deps, unres.push name.toString)
   ) (#[], #[])
 
+/-- Parse the header recursively to find all import commands -/
+partial def findImports (stx : Syntax) (content: String) : IO (Array ImportInfo) → IO (Array ImportInfo)
+  | accIO => do
+    let acc ← accIO
+    match stx with
+    | Syntax.node _ kind args =>
+      if kind == `Lean.Parser.Module.import then
+        -- Found an import
+        match stx.getRange? with
+        | some range =>
+          let moduleName := extractModuleName stx
+          let text := content.extract range.start range.stop
+          let info : ImportInfo := {
+            moduleName := moduleName
+            startPos := range.start.byteIdx
+            endPos := range.stop.byteIdx
+            text := text
+          }
+          return acc.push info
+        | none => return acc
+      else
+        -- Recursively search children
+        args.foldlM (fun acc child => findImports child content (pure acc)) acc
+    | _ => return acc
+
 /-- Parse imports and namespaces from a Lean 4 file -/
 def parseImports (filepath : System.FilePath) : IO DependencyInfo := do
   let content ← IO.FS.readFile filepath
@@ -164,32 +189,9 @@ def parseImports (filepath : System.FilePath) : IO DependencyInfo := do
   -- Extract the underlying syntax from TSyntax
   let headerSyn : Syntax := headerStx
 
-  -- Parse the header recursively to find all import commands
-  let rec findImports (stx : Syntax) : IO (Array ImportInfo) → IO (Array ImportInfo)
-    | accIO => do
-      let acc ← accIO
-      match stx with
-      | Syntax.node _ kind args =>
-        if kind == `Lean.Parser.Module.import then
-          -- Found an import
-          match stx.getRange? with
-          | some range =>
-            let moduleName := extractModuleName stx
-            let text := content.extract range.start range.stop
-            let info : ImportInfo := {
-              moduleName := moduleName
-              startPos := range.start.byteIdx
-              endPos := range.stop.byteIdx
-              text := text
-            }
-            return acc.push info
-          | none => return acc
-        else
-          -- Recursively search children
-          args.foldlM (fun acc child => findImports child (pure acc)) acc
-      | _ => return acc
-
-  imports ← findImports headerSyn (pure imports)
+
+
+  imports ← findImports headerSyn content (pure imports)
 
   -- Now parse the rest of the file to find namespace declarations
   let env ← Lean.importModules #[] {} 0
diff --git a/src/itp_interface/tools/tactic_parser/TacticParser/LineParser.lean b/src/itp_interface/tools/tactic_parser/TacticParser/LineParser.lean
index 3ff3b63..9dc95a8 100644
--- a/src/itp_interface/tools/tactic_parser/TacticParser/LineParser.lean
+++ b/src/itp_interface/tools/tactic_parser/TacticParser/LineParser.lean
@@ -14,7 +14,9 @@ partial def identifySomeDeclType (stx : Syntax) : Option (DeclType × Nat) :=
     match stx with
     | Syntax.node _ _ args =>
       -- Look for the actual declaration type in the children
-      let idx := args.findIdx (fun a => (identifySomeDeclType a).isSome);
+      -- NOTE: using findIdx? for backward compatibility to Lean 4.15
+      -- (as.findIdx? p).getD as.size
+      let idx := (args.findIdx? (fun a => (identifySomeDeclType a).isSome)).getD args.size;
       if idx = args.size then
         some (.unknown, idx)
       else
diff --git a/src/itp_interface/tools/tactic_parser/TacticParser/SyntaxWalker.lean b/src/itp_interface/tools/tactic_parser/TacticParser/SyntaxWalker.lean
index fb9f9fc..46689ac 100644
--- a/src/itp_interface/tools/tactic_parser/TacticParser/SyntaxWalker.lean
+++ b/src/itp_interface/tools/tactic_parser/TacticParser/SyntaxWalker.lean
@@ -181,7 +181,7 @@ def nodeEndPos (node : InfoTreeNode) : Option Position :=
   | InfoTreeNode.leanInfo _ _ _ _ _ endPos _ _ => some endPos
   | _ => none
 
-def filterAllNodesWhichDontStartAndEndOnLine (node : InfoTreeNode) (line_num: Nat) : Array InfoTreeNode :=
+partial def filterAllNodesWhichDontStartAndEndOnLine (node : InfoTreeNode) (line_num: Nat) : Array InfoTreeNode :=
 match node with
 | .context child =>
   filterAllNodesWhichDontStartAndEndOnLine child line_num
@@ -213,7 +213,7 @@ let arg_max := all_possible_nodes.foldl (fun (acc_node, acc_len) n =>
 ) (InfoTreeNode.hole, 0)
 arg_max
 
-def getAllLinesInTree (node : InfoTreeNode) : Std.HashSet Nat :=
+partial def getAllLinesInTree (node : InfoTreeNode) : Std.HashSet Nat :=
   match node with
   | .context child =>
     getAllLinesInTree child
diff --git a/src/itp_interface/tools/tactic_parser/TacticParser/Types.lean b/src/itp_interface/tools/tactic_parser/TacticParser/Types.lean
index a4ef181..fee67f1 100644
--- a/src/itp_interface/tools/tactic_parser/TacticParser/Types.lean
+++ b/src/itp_interface/tools/tactic_parser/TacticParser/Types.lean
@@ -269,7 +269,7 @@ partial def InfoNodeStruct.toJson (n: InfoNodeStruct) : Json :=
 instance : ToJson InfoNodeStruct where
   toJson := InfoNodeStruct.toJson
 
-def getInfoNodeStruct (node : InfoTreeNode) : Option InfoNodeStruct :=
+partial def getInfoNodeStruct (node : InfoTreeNode) : Option InfoNodeStruct :=
   match node with
   | .leanInfo declType name docString text startPos endPos namespc children =>
     let childStructs := children.map getInfoNodeStruct
diff --git a/src/test/simple_env_test.py b/src/test/simple_env_test.py
index 1005f54..0622260 100644
--- a/src/test/simple_env_test.py
+++ b/src/test/simple_env_test.py
@@ -137,7 +137,6 @@ def test_simple_lean4(self):
             assert proof_was_finished, "Proof was not finished"
 
     def test_lean4_backtracking(self):
-        from itp_interface.rl.proof_state import ProofState
         from itp_interface.rl.proof_action import ProofAction
         from itp_interface.rl.simple_proof_env import ProofEnv
         from itp_interface.tools.proof_exec_callback import ProofExecutorCallback