Add fork snapshot modes (#15239)

## Summary
- add `ForkSnapshotMode` to `ThreadManager::fork_thread` so callers can
request either a committed snapshot or an interrupted snapshot
- share the model-visible `<turn_aborted>` history marker between the
live interrupt path and interrupted forks
- update the small set of direct fork callsites to pass
`ForkSnapshotMode::Committed`

Note: this enables /btw to work similarly as Esc to interrupt (hopefully
somewhat in distribution)

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/core/tests/suite/compact_resume_fork.rs

@@ -12,6 +12,7 @@ use super::compact::FIRST_REPLY;
 use super::compact::SUMMARY_TEXT;
 use anyhow::Result;
 use codex_core::CodexThread;
+use codex_core::ForkSnapshot;
 use codex_core::ThreadManager;
 use codex_core::compact::SUMMARIZATION_PROMPT;
 use codex_core::config::Config;
@@ -383,8 +384,13 @@ async fn compact_resume_after_second_compaction_preserves_history() -> Result<()
     let seeded_user_prefix = &first_request_user_texts[..first_turn_user_index];
     let summary_after_second_compact =
         extract_summary_user_text(&requests[requests.len() - 3], SUMMARY_TEXT);
-    let mut expected_after_second_compact_user_texts =
-        vec!["AFTER_FORK".to_string(), summary_after_second_compact];
+    let mut expected_after_second_compact_user_texts = vec![
+        "hello world".to_string(),
+        "AFTER_COMPACT".to_string(),
+        "AFTER_RESUME".to_string(),
+        "AFTER_FORK".to_string(),
+        summary_after_second_compact,
+    ];
     expected_after_second_compact_user_texts.extend_from_slice(seeded_user_prefix);
     expected_after_second_compact_user_texts.push("AFTER_COMPACT_2".to_string());
     let final_user_texts = json_message_input_texts(&requests[requests.len() - 1], "user");
@@ -841,8 +847,14 @@ async fn fork_thread(
     path: std::path::PathBuf,
     nth_user_message: usize,
 ) -> Arc<CodexThread> {
-    Box::pin(manager.fork_thread(nth_user_message, config.clone(), path, false, None))
-        .await
-        .expect("fork conversation")
-        .thread
+    Box::pin(manager.fork_thread(
+        ForkSnapshot::TruncateBeforeNthUserMessage(nth_user_message),
+        config.clone(),
+        path,
+        /*persist_extended_history*/ false,
+        /*parent_trace*/ None,
+    ))
+    .await
+    .expect("fork conversation")
+    .thread
 }

codex-rs/core/tests/suite/fork_thread.rs

@@ -1,3 +1,4 @@
+use codex_core::ForkSnapshot;
 use codex_core::NewThread;
 use codex_core::parse_turn_item;
 use codex_protocol::items::TurnItem;
@@ -110,7 +111,13 @@ async fn fork_thread_twice_drops_to_first_message() {
         thread: codex_fork1,
         ..
     } = thread_manager
-        .fork_thread(1, config_for_fork.clone(), base_path.clone(), false, None)
+        .fork_thread(
+            ForkSnapshot::TruncateBeforeNthUserMessage(1),
+            config_for_fork.clone(),
+            base_path.clone(),
+            /*persist_extended_history*/ false,
+            /*parent_trace*/ None,
+        )
         .await
         .expect("fork 1");
 
@@ -129,7 +136,13 @@ async fn fork_thread_twice_drops_to_first_message() {
         thread: codex_fork2,
         ..
     } = thread_manager
-        .fork_thread(0, config_for_fork.clone(), fork1_path.clone(), false, None)
+        .fork_thread(
+            ForkSnapshot::TruncateBeforeNthUserMessage(0),
+            config_for_fork.clone(),
+            fork1_path.clone(),
+            /*persist_extended_history*/ false,
+            /*parent_trace*/ None,
+        )
         .await
         .expect("fork 2");
 

codex-rs/core/tests/suite/permissions_messages.rs

@@ -1,4 +1,5 @@
 use anyhow::Result;
+use codex_core::ForkSnapshot;
 use codex_core::config::Constrained;
 use codex_execpolicy::Policy;
 use codex_protocol::models::DeveloperInstructions;
@@ -419,7 +420,13 @@ async fn resume_and_fork_append_permissions_messages() -> Result<()> {
     fork_config.permissions.approval_policy = Constrained::allow_any(AskForApproval::UnlessTrusted);
     let forked = initial
         .thread_manager
-        .fork_thread(usize::MAX, fork_config, rollout_path, false, None)
+        .fork_thread(
+            ForkSnapshot::Interrupted,
+            fork_config,
+            rollout_path,
+            /*persist_extended_history*/ false,
+            /*parent_trace*/ None,
+        )
         .await?;
     forked
         .thread

codex-rs/core/tests/suite/shell_snapshot.rs

@@ -531,7 +531,9 @@ async fn shell_command_snapshot_still_intercepts_apply_patch() -> Result<()> {
     let script = "apply_patch <<'EOF'\n*** Begin Patch\n*** Add File: snapshot-apply.txt\n+hello from snapshot\n*** End Patch\nEOF\n";
     let args = json!({
         "command": script,
-        "timeout_ms": 1_000,
+        // The intercepted apply_patch path self-invokes codex, which can take
+        // longer than a second in Bazel macOS test environments.
+        "timeout_ms": 5_000,
     });
     let call_id = "shell-snapshot-apply-patch";
     let responses = vec![