Include shared histories in rollout compression (#42039)

## What changed

- Make `local_thread_store_compression` compress cold rollout files across shared and forked histories without a separate compression mode.
- Retire `local_thread_store_shared_compression` while continuing to accept it in strict configuration without changing compression behavior.
- Read rollout files through the compressed-rollout reader when `codex exec resume` determines the latest turn's working directory.

## Testing

- Cover compression and restoration of an archived fork chain.
- Cover cwd-based resume selection when only the compressed rollout remains.
- Cover the removed compatibility key in strict configuration.

GitOrigin-RevId: 8edebf61eccc1f79cabb8e641f8982c76f337bf1

codex-rs/exec/Cargo.toml

@@ -37,6 +37,7 @@ codex-login = { workspace = true }
 codex-model-provider-info = { workspace = true }
 codex-otel = { workspace = true }
 codex-protocol = { workspace = true }
+codex-rollout = { workspace = true }
 codex-utils-absolute-path = { workspace = true }
 codex-utils-cli = { workspace = true }
 codex-utils-oss = { workspace = true }
@@ -77,3 +78,4 @@ tracing-opentelemetry = { workspace = true }
 uuid = { workspace = true }
 walkdir = { workspace = true }
 wiremock = { workspace = true }
+zstd = { workspace = true }

codex-rs/exec/src/lib.rs

@@ -1563,20 +1563,24 @@ async fn latest_thread_cwd(thread: &AppServerThread) -> PathBuf {
 }
 
 async fn parse_latest_turn_context_cwd(path: &Path) -> Option<PathBuf> {
-    let text = tokio::fs::read_to_string(path).await.ok()?;
-    for line in text.lines().rev() {
-        let trimmed = line.trim();
-        if trimmed.is_empty() {
-            continue;
+    let path = path.to_path_buf();
+    tokio::task::spawn_blocking(move || {
+        let reader = codex_rollout::open_rollout_seekable_reader(&path).ok()?;
+        let mut scanner = codex_rollout::ReverseJsonlScanner::new(reader).ok()?;
+        while let Some(outcome) = scanner.scan_next::<RolloutLine>().ok()? {
+            if let codex_rollout::ScanOutcome::Parsed(RolloutLine {
+                item: RolloutItem::TurnContext(item),
+                ..
+            }) = outcome
+            {
+                return Some(item.cwd.into_path_buf());
+            }
         }
-        let Ok(rollout_line) = serde_json::from_str::<RolloutLine>(trimmed) else {
-            continue;
-        };
-        if let RolloutItem::TurnContext(item) = rollout_line.item {
-            return Some(item.cwd.into_path_buf());
-        }
-    }
-    None
+        None
+    })
+    .await
+    .ok()
+    .flatten()
 }
 
 fn cwds_match(current_cwd: &Path, session_cwd: &Path) -> bool {

codex-rs/exec/tests/suite/resume.rs

@@ -564,6 +564,14 @@ async fn exec_resume_last_respects_cwd_filter_and_all_flag() -> anyhow::Result<(
         "resume --last --all should pick newest session"
     );
 
+    // Selection must still use the latest turn's cwd when only the compressed rollout exists.
+    zstd::stream::copy_encode(
+        std::fs::File::open(&path_b)?,
+        std::fs::File::create(path_b.with_extension("jsonl.zst"))?,
+        /*level*/ 3,
+    )?;
+    std::fs::remove_file(&path_b)?;
+
     let marker_a2 = format!("resume-cwd-a-2-{}", Uuid::new_v4());
     let prompt_a2 = format!("echo {marker_a2}");
     test.cmd_with_server(&server)