Use AbsolutePathBuf for exec cwd plumbing (#17063)

## Summary
- Carry `AbsolutePathBuf` through tool cwd parsing/resolution instead of
resolving workdirs to raw `PathBuf`s.
- Type exec/sandbox request cwd fields as `AbsolutePathBuf` through
`ExecParams`, `ExecRequest`, `SandboxCommand`, and unified exec runtime
requests.
- Keep `PathBuf` conversions at external/event boundaries and update
existing tests/fixtures for the typed cwd.

## Validation
- `cargo check -p codex-core --tests`
- `cargo check -p codex-sandboxing --tests`
- `cargo test -p codex-sandboxing`
- `cargo test -p codex-core --lib tools::handlers::`
- `just fix -p codex-sandboxing`
- `just fix -p codex-core`
- `just fmt`

Full `codex-core` test suite was not run locally; per repo guidance I
kept local validation targeted.

codex-rs/core/src/unified_exec/mod.rs

@@ -24,12 +24,12 @@
 
 use std::collections::HashMap;
 use std::collections::HashSet;
-use std::path::PathBuf;
 use std::sync::Arc;
 use std::sync::Weak;
 
 use codex_network_proxy::NetworkProxy;
 use codex_protocol::models::PermissionProfile;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use rand::Rng;
 use rand::rng;
 use tokio::sync::Mutex;
@@ -91,7 +91,7 @@ pub(crate) struct ExecCommandRequest {
     pub process_id: i32,
     pub yield_time_ms: u64,
     pub max_output_tokens: Option<usize>,
-    pub workdir: Option<PathBuf>,
+    pub workdir: Option<AbsolutePathBuf>,
     pub network: Option<NetworkProxy>,
     pub tty: bool,
     pub sandbox_permissions: SandboxPermissions,

codex-rs/core/src/unified_exec/mod_tests.rs

@@ -51,7 +51,7 @@ fn shell_env() -> HashMap<String, String> {
 fn test_exec_request(
     turn: &TurnContext,
     command: Vec<String>,
-    cwd: PathBuf,
+    cwd: AbsolutePathBuf,
     env: HashMap<String, String>,
 ) -> ExecRequest {
     let windows_sandbox_private_desktop = false;
@@ -87,7 +87,9 @@ async fn exec_command_with_tty(
 ) -> Result<ExecCommandToolOutput, UnifiedExecError> {
     let manager = &session.services.unified_exec_manager;
     let process_id = manager.allocate_process_id().await;
-    let cwd = workdir.unwrap_or_else(|| turn.cwd.clone().to_path_buf());
+    let cwd = workdir
+        .as_ref()
+        .map_or_else(|| turn.cwd.clone(), |workdir| turn.cwd.join(workdir));
     let command = vec!["bash".to_string(), "-lc".to_string(), cmd.to_string()];
     let request = test_exec_request(turn, command.clone(), cwd.clone(), shell_env());
 
@@ -502,7 +504,7 @@ async fn completed_pipe_commands_preserve_exit_code() -> anyhow::Result<()> {
     let request = test_exec_request(
         &turn,
         vec!["bash".to_string(), "-lc".to_string(), "exit 17".to_string()],
-        PathBuf::from("/tmp"),
+        turn.cwd.clone(),
         shell_env(),
     );
 
@@ -544,7 +546,7 @@ async fn unified_exec_uses_remote_exec_server_when_configured() -> anyhow::Resul
     let request = test_exec_request(
         &turn,
         vec!["bash".to_string(), "-i".to_string()],
-        PathBuf::from("/tmp"),
+        remote_test_env.cwd().clone(),
         shell_env(),
     );
 
@@ -598,7 +600,7 @@ async fn remote_exec_server_rejects_inherited_fd_launches() -> anyhow::Result<()
     let request = test_exec_request(
         &turn,
         vec!["bash".to_string(), "-lc".to_string(), "echo ok".to_string()],
-        PathBuf::from("/tmp"),
+        turn.cwd.clone(),
         shell_env(),
     );
 

codex-rs/core/src/unified_exec/process_manager.rs

@@ -2,7 +2,6 @@ use rand::Rng;
 use std::cmp::Reverse;
 use std::collections::HashMap;
 use std::collections::HashSet;
-use std::path::PathBuf;
 use std::sync::Arc;
 use std::sync::atomic::AtomicBool;
 use std::sync::atomic::Ordering;
@@ -49,6 +48,7 @@ use crate::unified_exec::process::OutputHandles;
 use crate::unified_exec::process::SpawnLifecycleHandle;
 use crate::unified_exec::process::UnifiedExecProcess;
 use codex_protocol::protocol::ExecCommandSource;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_output_truncation::approx_token_count;
 
 const UNIFIED_EXEC_ENV: [(&str, &str); 10] = [
@@ -165,7 +165,7 @@ impl UnifiedExecProcessManager {
         let cwd = request
             .workdir
             .clone()
-            .unwrap_or_else(|| context.turn.cwd.to_path_buf());
+            .unwrap_or_else(|| context.turn.cwd.clone());
         let process = self
             .open_session_with_sandbox(&request, cwd.clone(), context)
             .await;
@@ -189,7 +189,7 @@ impl UnifiedExecProcessManager {
         );
         let emitter = ToolEmitter::unified_exec(
             &request.command,
-            cwd.clone(),
+            cwd.to_path_buf(),
             ExecCommandSource::UnifiedExecStartup,
             Some(request.process_id.to_string()),
         );
@@ -255,7 +255,7 @@ impl UnifiedExecProcessManager {
                     Arc::clone(&context.turn),
                     context.call_id.clone(),
                     request.command.clone(),
-                    cwd.clone(),
+                    cwd.to_path_buf(),
                     Some(request.process_id.to_string()),
                     Arc::clone(&transcript),
                     message.clone(),
@@ -298,7 +298,7 @@ impl UnifiedExecProcessManager {
                 Arc::clone(&context.turn),
                 context.call_id.clone(),
                 request.command.clone(),
-                cwd.clone(),
+                cwd.to_path_buf(),
                 Some(process_id.to_string()),
                 Arc::clone(&transcript),
                 text.clone(),
@@ -526,7 +526,7 @@ impl UnifiedExecProcessManager {
         process: Arc<UnifiedExecProcess>,
         context: &UnifiedExecContext,
         command: &[String],
-        cwd: PathBuf,
+        cwd: AbsolutePathBuf,
         started_at: Instant,
         process_id: i32,
         tty: bool,
@@ -572,7 +572,7 @@ impl UnifiedExecProcessManager {
             Arc::clone(&context.turn),
             context.call_id.clone(),
             command.to_vec(),
-            cwd,
+            cwd.to_path_buf(),
             process_id,
             transcript,
             started_at,
@@ -605,7 +605,7 @@ impl UnifiedExecProcessManager {
                 .start(codex_exec_server::ExecParams {
                     process_id: exec_server_process_id(process_id).into(),
                     argv: request.command.clone(),
-                    cwd: request.cwd.clone(),
+                    cwd: request.cwd.to_path_buf(),
                     env: request.env.clone(),
                     tty,
                     arg0: request.arg0.clone(),
@@ -646,7 +646,7 @@ impl UnifiedExecProcessManager {
     pub(super) async fn open_session_with_sandbox(
         &self,
         request: &ExecCommandRequest,
-        cwd: PathBuf,
+        cwd: AbsolutePathBuf,
         context: &UnifiedExecContext,
     ) -> Result<(UnifiedExecProcess, Option<DeferredNetworkApproval>), UnifiedExecError> {
         let env = apply_unified_exec_env(create_env(