diff --git a/codex-rs/shell-command/src/command_safety/powershell_parser.ps1 b/codex-rs/shell-command/src/command_safety/powershell_parser.ps1
index de696c88b..92291e7c9 100644
--- a/codex-rs/shell-command/src/command_safety/powershell_parser.ps1
+++ b/codex-rs/shell-command/src/command_safety/powershell_parser.ps1
@@ -42,6 +42,21 @@ function Invoke-ParseRequest {
         return @{ id = $RequestId; status = 'parse_errors' }
     }
 
+    # Top-level AST regions and collections outside the end-block statement list
+    # can execute code that the command lowering below does not inspect.
+    $cleanBlock = $ast.PSObject.Properties['CleanBlock']
+    if (
+        $ast.ParamBlock -ne $null -or
+        $ast.DynamicParamBlock -ne $null -or
+        $ast.BeginBlock -ne $null -or
+        $ast.ProcessBlock -ne $null -or
+        ($cleanBlock -ne $null -and $cleanBlock.Value -ne $null) -or
+        $ast.UsingStatements.Count -gt 0 -or
+        $ast.EndBlock.Traps.Count -gt 0
+    ) {
+        return @{ id = $RequestId; status = 'unsupported' }
+    }
+
     # PowerShell's stop-parsing marker hands the remaining source text to native
     # commands with runtime argument handling that does not match the AST shape we
     # flatten below. Keep that form out of the argv-like lowering path entirely.
diff --git a/codex-rs/shell-command/src/command_safety/powershell_parser.rs b/codex-rs/shell-command/src/command_safety/powershell_parser.rs
index ddcbdf572..00b18af6f 100644
--- a/codex-rs/shell-command/src/command_safety/powershell_parser.rs
+++ b/codex-rs/shell-command/src/command_safety/powershell_parser.rs
@@ -310,4 +310,62 @@ mod tests {
             .unwrap();
         assert_eq!(parsed, PowershellParseOutcome::Unsupported);
     }
+
+    #[test]
+    fn parser_process_rejects_param_blocks() {
+        let Some(powershell) = try_find_powershell_executable_blocking() else {
+            return;
+        };
+        let powershell = powershell.as_path().to_str().unwrap();
+        let mut parser = PowershellParserProcess::spawn(powershell).unwrap();
+
+        let parsed = parser
+            .parse("param([string]$path = (Get-Location)) Write-Output test")
+            .unwrap();
+        assert_eq!(parsed, PowershellParseOutcome::Unsupported);
+    }
+
+    #[test]
+    fn parser_process_rejects_named_blocks() {
+        let Some(powershell) = try_find_powershell_executable_blocking() else {
+            return;
+        };
+        let powershell = powershell.as_path().to_str().unwrap();
+        let mut parser = PowershellParserProcess::spawn(powershell).unwrap();
+
+        let parsed = parser
+            .parse("begin { Set-Content codex_poc.txt pwned } end { Get-Content Cargo.toml }")
+            .unwrap();
+        assert_eq!(parsed, PowershellParseOutcome::Unsupported);
+    }
+
+    #[test]
+    fn parser_process_rejects_using_statements() {
+        let Some(powershell) = try_find_powershell_executable_blocking() else {
+            return;
+        };
+        let powershell = powershell.as_path().to_str().unwrap();
+        let mut parser = PowershellParserProcess::spawn(powershell).unwrap();
+
+        let parsed = parser
+            .parse("using module ./codex_poc.psm1\nGet-Content Cargo.toml")
+            .unwrap();
+        assert_eq!(parsed, PowershellParseOutcome::Unsupported);
+    }
+
+    #[test]
+    fn parser_process_rejects_trap_blocks() {
+        let Some(powershell) = try_find_powershell_executable_blocking() else {
+            return;
+        };
+        let powershell = powershell.as_path().to_str().unwrap();
+        let mut parser = PowershellParserProcess::spawn(powershell).unwrap();
+
+        let parsed = parser
+            .parse(
+                "trap { Set-Content codex_poc.txt pwned; continue } Get-Content missing -ErrorAction Stop",
+            )
+            .unwrap();
+        assert_eq!(parsed, PowershellParseOutcome::Unsupported);
+    }
 }
diff --git a/codex-rs/shell-command/src/command_safety/windows_safe_commands.rs b/codex-rs/shell-command/src/command_safety/windows_safe_commands.rs
index a8dcef6de..df2025253 100644
--- a/codex-rs/shell-command/src/command_safety/windows_safe_commands.rs
+++ b/codex-rs/shell-command/src/command_safety/windows_safe_commands.rs
@@ -412,6 +412,46 @@ mod tests {
         ])));
     }
 
+    #[test]
+    fn rejects_powershell_param_blocks() {
+        assert!(!is_safe_command_windows(&vec_str(&[
+            "powershell.exe",
+            "-NoProfile",
+            "-Command",
+            "param([string]$path = (Get-Location)) Write-Output test",
+        ])));
+    }
+
+    #[test]
+    fn rejects_powershell_named_blocks() {
+        assert!(!is_safe_command_windows(&vec_str(&[
+            "powershell.exe",
+            "-NoProfile",
+            "-Command",
+            "begin { Set-Content codex_poc.txt pwned } end { Get-Content Cargo.toml }",
+        ])));
+    }
+
+    #[test]
+    fn rejects_powershell_using_statements() {
+        assert!(!is_safe_command_windows(&vec_str(&[
+            "powershell.exe",
+            "-NoProfile",
+            "-Command",
+            "using module ./codex_poc.psm1\nGet-Content Cargo.toml",
+        ])));
+    }
+
+    #[test]
+    fn rejects_powershell_trap_blocks() {
+        assert!(!is_safe_command_windows(&vec_str(&[
+            "powershell.exe",
+            "-NoProfile",
+            "-Command",
+            "trap { Set-Content codex_poc.txt pwned; continue } Get-Content missing -ErrorAction Stop",
+        ])));
+    }
+
     #[test]
     fn rejects_powershell_commands_with_side_effects() {
         assert!(!is_safe_command_windows(&vec_str(&[