[codex] add context-window lineage headers (#16758)

This change adds client-owned context-window and parent thread id
headers to all requests to responses api.

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

@@ -0,0 +1,146 @@
+#![allow(clippy::expect_used)]
+
+use super::compact::COMPACT_WARNING_MESSAGE;
+use anyhow::Result;
+use codex_core::CodexThread;
+use codex_core::compact::SUMMARIZATION_PROMPT;
+use codex_protocol::protocol::EventMsg;
+use codex_protocol::protocol::Op;
+use codex_protocol::protocol::WarningEvent;
+use codex_protocol::user_input::UserInput;
+use core_test_support::responses::ResponsesRequest;
+use core_test_support::responses::ev_assistant_message;
+use core_test_support::responses::ev_completed;
+use core_test_support::responses::mount_sse_sequence;
+use core_test_support::responses::sse;
+use core_test_support::responses::start_mock_server;
+use core_test_support::skip_if_no_network;
+use core_test_support::test_codex::test_codex;
+use core_test_support::wait_for_event;
+use pretty_assertions::assert_eq;
+use std::sync::Arc;
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn window_id_advances_after_compact_persists_on_resume_and_resets_on_fork() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let request_log = mount_sse_sequence(
+        &server,
+        vec![
+            sse(vec![
+                ev_assistant_message("msg-1", "first reply"),
+                ev_completed("resp-1"),
+            ]),
+            sse(vec![
+                ev_assistant_message("msg-2", "summary"),
+                ev_completed("resp-2"),
+            ]),
+            sse(vec![ev_completed("resp-3")]),
+            sse(vec![ev_completed("resp-4")]),
+            sse(vec![ev_completed("resp-5")]),
+        ],
+    )
+    .await;
+
+    let mut builder = test_codex().with_config(|config| {
+        config.model_provider.name = "Non-OpenAI Model provider".to_string();
+        config.compact_prompt = Some(SUMMARIZATION_PROMPT.to_string());
+    });
+    let initial = builder.build(&server).await?;
+    let initial_thread = Arc::clone(&initial.codex);
+    let rollout_path = initial
+        .session_configured
+        .rollout_path
+        .clone()
+        .expect("rollout path");
+
+    submit_user_turn(&initial_thread, "before compact").await?;
+    submit_compact_turn(&initial_thread).await?;
+    submit_user_turn(&initial_thread, "after compact").await?;
+    shutdown_thread(&initial_thread).await?;
+
+    let resumed = builder
+        .resume(&server, initial.home.clone(), rollout_path.clone())
+        .await?;
+    submit_user_turn(&resumed.codex, "after resume").await?;
+    shutdown_thread(&resumed.codex).await?;
+
+    let forked = resumed
+        .thread_manager
+        .fork_thread(
+            /*snapshot*/ 0usize,
+            resumed.config.clone(),
+            rollout_path,
+            /*persist_extended_history*/ false,
+            /*parent_trace*/ None,
+        )
+        .await?;
+    submit_user_turn(&forked.thread, "after fork").await?;
+    shutdown_thread(&forked.thread).await?;
+
+    let requests = request_log.requests();
+    assert_eq!(requests.len(), 5, "expected five model requests");
+
+    let (initial_thread_id, first_generation) = window_id_parts(&requests[0]);
+    let (compact_thread_id, compact_generation) = window_id_parts(&requests[1]);
+    let (after_compact_thread_id, after_compact_generation) = window_id_parts(&requests[2]);
+    let (after_resume_thread_id, after_resume_generation) = window_id_parts(&requests[3]);
+    let (after_fork_thread_id, after_fork_generation) = window_id_parts(&requests[4]);
+
+    assert_eq!(first_generation, 0);
+    assert_eq!(compact_thread_id, initial_thread_id);
+    assert_eq!(compact_generation, 0);
+    assert_eq!(after_compact_thread_id, initial_thread_id);
+    assert_eq!(after_compact_generation, 1);
+    assert_eq!(after_resume_thread_id, initial_thread_id);
+    assert_eq!(after_resume_generation, 1);
+    assert_ne!(after_fork_thread_id, initial_thread_id);
+    assert_eq!(after_fork_generation, 0);
+
+    Ok(())
+}
+
+async fn submit_user_turn(codex: &Arc<CodexThread>, text: &str) -> Result<()> {
+    codex
+        .submit(Op::UserInput {
+            items: vec![UserInput::Text {
+                text: text.to_string(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+        })
+        .await?;
+    wait_for_event(codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+    Ok(())
+}
+
+async fn submit_compact_turn(codex: &Arc<CodexThread>) -> Result<()> {
+    codex.submit(Op::Compact).await?;
+    let warning_event = wait_for_event(codex, |event| matches!(event, EventMsg::Warning(_))).await;
+    let EventMsg::Warning(WarningEvent { message }) = warning_event else {
+        panic!("expected warning event after compact");
+    };
+    assert_eq!(message, COMPACT_WARNING_MESSAGE);
+    wait_for_event(codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+    Ok(())
+}
+
+async fn shutdown_thread(codex: &Arc<CodexThread>) -> Result<()> {
+    codex.submit(Op::Shutdown).await?;
+    wait_for_event(codex, |event| matches!(event, EventMsg::ShutdownComplete)).await;
+    Ok(())
+}
+
+fn window_id_parts(request: &ResponsesRequest) -> (String, u64) {
+    let window_id = request
+        .header("x-codex-window-id")
+        .expect("missing x-codex-window-id header");
+    let (thread_id, generation) = window_id
+        .rsplit_once(':')
+        .unwrap_or_else(|| panic!("invalid window id header: {window_id}"));
+    let generation = generation
+        .parse::<u64>()
+        .unwrap_or_else(|err| panic!("invalid window generation in {window_id}: {err}"));
+    (thread_id.to_string(), generation)
+}