diff --git a/codex-rs/core/src/apply_patch.rs b/codex-rs/core/src/apply_patch.rs
index 7efae19f15..f1653bf9e9 100644
--- a/codex-rs/core/src/apply_patch.rs
+++ b/codex-rs/core/src/apply_patch.rs
@@ -114,7 +114,7 @@ pub(crate) fn convert_apply_patch_to_protocol(
 mod tests {
     use super::*;
     use pretty_assertions::assert_eq;
-    
+
     use tempfile::tempdir;
 
     #[test]
diff --git a/codex-rs/core/src/codex.rs b/codex-rs/core/src/codex.rs
index cde64105f4..2877098444 100644
--- a/codex-rs/core/src/codex.rs
+++ b/codex-rs/core/src/codex.rs
@@ -2616,7 +2616,7 @@ async fn handle_container_exec_with_params(
         stdout_stream,
     };
 
-    sess.executor.update_environment( // todo this should not be needed ? Not sure what it means
+    sess.executor.update_environment(
         turn_context.sandbox_policy.clone(),
         turn_context.cwd.clone(),
     );
diff --git a/codex-rs/core/src/executor/backends.rs b/codex-rs/core/src/executor/backends.rs
index 09c786a9d4..aa744b8174 100644
--- a/codex-rs/core/src/executor/backends.rs
+++ b/codex-rs/core/src/executor/backends.rs
@@ -1,13 +1,11 @@
 use std::collections::HashMap;
 use std::env;
-use std::sync::Arc;
 
 use async_trait::async_trait;
 
-use crate::apply_patch::ApplyPatchExec;
 use crate::CODEX_APPLY_PATCH_ARG1;
+use crate::apply_patch::ApplyPatchExec;
 use crate::exec::ExecParams;
-use crate::exec::ExecToolCallOutput;
 use crate::function_tool::FunctionCallError;
 
 pub(crate) enum ExecutionMode {
@@ -27,29 +25,14 @@ pub(crate) trait ExecutionBackend: Send + Sync {
     ) -> Result<ExecParams, FunctionCallError>;
 }
 
-pub(crate) struct BackendStore {
-    shell: Arc<dyn ExecutionBackend>,
-    apply_patch: Arc<dyn ExecutionBackend>,
-}
+static SHELL_BACKEND: ShellBackend = ShellBackend;
+static APPLY_PATCH_BACKEND: ApplyPatchBackend = ApplyPatchBackend;
 
-impl BackendStore {
-    pub(crate) fn new() -> Self {
-        Self {
-            shell: Arc::new(ShellBackend),
-            apply_patch: Arc::new(ApplyPatchBackend),
-        }
+pub(crate) fn backend_for_mode(mode: &ExecutionMode) -> &'static dyn ExecutionBackend {
+    match mode {
+        ExecutionMode::Shell => &SHELL_BACKEND,
+        ExecutionMode::ApplyPatch(_) => &APPLY_PATCH_BACKEND,
     }
-
-    pub(crate) fn for_mode(&self, mode: &ExecutionMode) -> Arc<dyn ExecutionBackend> {
-        match mode {
-            ExecutionMode::Shell => self.shell.clone(),
-            ExecutionMode::ApplyPatch(_) => self.apply_patch.clone(),
-        }
-    }
-}
-
-pub(crate) fn default_backends() -> BackendStore {
-    BackendStore::new()
 }
 
 struct ShellBackend;
@@ -101,7 +84,7 @@ impl ExecutionBackend for ApplyPatchBackend {
                     with_escalated_permissions: params.with_escalated_permissions,
                     justification: params.justification,
                 })
-            },
+            }
             ExecutionMode::Shell => Err(FunctionCallError::RespondToModel(
                 "apply_patch backend invoked without patch context".to_string(),
             )),
diff --git a/codex-rs/core/src/executor/runner.rs b/codex-rs/core/src/executor/runner.rs
index a65da13802..9161e78659 100644
--- a/codex-rs/core/src/executor/runner.rs
+++ b/codex-rs/core/src/executor/runner.rs
@@ -5,10 +5,8 @@ use std::time::Duration;
 
 use thiserror::Error;
 
-use super::backends::BackendStore;
-use super::backends::ExecutionBackend;
 use super::backends::ExecutionMode;
-use super::backends::default_backends;
+use super::backends::backend_for_mode;
 use super::cache::ApprovalCache;
 use crate::codex::Session;
 use crate::error::CodexErr;
@@ -64,7 +62,6 @@ impl ExecError {
 /// Coordinates sandbox selection, backend-specific preparation, and command
 /// execution for tool calls requested by the model.
 pub(crate) struct Executor {
-    backends: BackendStore,
     approval_cache: ApprovalCache,
     config: Arc<RwLock<ExecutorConfig>>,
 }
@@ -72,7 +69,6 @@ pub(crate) struct Executor {
 impl Executor {
     pub(crate) fn new(config: ExecutorConfig) -> Self {
         Self {
-            backends: default_backends(),
             approval_cache: ApprovalCache::default(),
             config: Arc::new(RwLock::new(config)),
         }
@@ -80,11 +76,7 @@ impl Executor {
 
     /// Updates the sandbox policy and working directory used for future
     /// executions without recreating the executor.
-    pub(crate) fn update_environment(
-        &self,
-        sandbox_policy: SandboxPolicy,
-        sandbox_cwd: PathBuf,
-    ) {
+    pub(crate) fn update_environment(&self, sandbox_policy: SandboxPolicy, sandbox_cwd: PathBuf) {
         if let Ok(mut cfg) = self.config.write() {
             cfg.sandbox_policy = sandbox_policy;
             cfg.sandbox_cwd = sandbox_cwd;
@@ -103,7 +95,7 @@ impl Executor {
         call_id: &str,
     ) -> Result<ExecToolCallOutput, ExecError> {
         // Step 1: Normalise parameters via the selected backend.
-        let backend = self.backends.for_mode(&request.mode);
+        let backend = backend_for_mode(&request.mode);
         request.params = backend
             .prepare(request.params, &request.mode)
             .map_err(ExecError::from)?;
@@ -148,10 +140,8 @@ impl Executor {
             }
             Err(CodexErr::Sandbox(error @ SandboxErr::Denied { .. })) => {
                 return if sandbox_decision.escalate_on_failure {
-                    self.retry_without_sandbox(
-                        &*backend, &request, &config, session, sub_id, call_id, error,
-                    )
-                    .await
+                    self.retry_without_sandbox(&request, &config, session, sub_id, call_id, error)
+                        .await
                 } else {
                     Err(ExecError::rejection(format!(
                         "failed in sandbox {:?} with execution error: {error:?}",
@@ -170,7 +160,6 @@ impl Executor {
     #[allow(clippy::too_many_arguments)]
     async fn retry_without_sandbox(
         &self,
-        backend: &dyn ExecutionBackend,
         request: &ExecutionRequest,
         config: &ExecutorConfig,
         session: &Session,