Pass thread IDs to attachment uploads (#47121)

## Why

Attachment stores need the receiving thread ID to support thread-based placement.

## What changed

Add `thread_id` to `UploadRequest` and pass the session's thread ID through image preparation for messages and tool outputs. Include the ID in debug output while continuing to redact attachment bytes.

## Testing

Extend the image rollout test to assert that a new image uploaded after resume carries the resumed session's thread ID. Update the debug-output test for the new field.

GitOrigin-RevId: f81e3bd761dca704064287177b8ecd7175662f07

codex-rs/attachment-store/src/lib.rs

@@ -36,6 +36,8 @@ pub trait AttachmentStore: Send + Sync {
 /// Attachment data supplied to [`AttachmentStore::upload`].
 #[derive(Clone, Eq, PartialEq)]
 pub struct UploadRequest {
+    /// Thread receiving this attachment; storage backends may use it for placement.
+    pub thread_id: String,
     /// Optional name associated with the attachment.
     pub file_name: Option<String>,
     /// Attachment bytes to persist.
@@ -46,6 +48,7 @@ impl fmt::Debug for UploadRequest {
     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
         formatter
             .debug_struct("UploadRequest")
+            .field("thread_id", &self.thread_id)
             .field("file_name", &self.file_name)
             .field("data", &"<redacted>")
             .finish()

codex-rs/attachment-store/src/lib_tests.rs

@@ -6,6 +6,7 @@ use super::*;
 #[test]
 fn attachment_debug_output_redacts_bytes() {
     let request = UploadRequest {
+        thread_id: "thread-1".to_string(),
         file_name: Some("image.png".to_string()),
         data: b"secret".to_vec(),
     };
@@ -16,7 +17,7 @@ fn attachment_debug_output_redacts_bytes() {
     assert_eq!(
         (format!("{request:?}"), format!("{result:?}")),
         (
-            r#"UploadRequest { file_name: Some("image.png"), data: "<redacted>" }"#.to_string(),
+            r#"UploadRequest { thread_id: "thread-1", file_name: Some("image.png"), data: "<redacted>" }"#.to_string(),
             r#"Inline { bytes: "<redacted>" }"#.to_string(),
         )
     );
@@ -47,6 +48,7 @@ async fn inline_store_preserves_image_bytes() {
     for (file_name, data) in cases {
         let attachment = InlineAttachmentStore
             .upload(UploadRequest {
+                thread_id: "thread-1".to_string(),
                 file_name: Some(file_name.to_string()),
                 data: data.to_vec(),
             })

codex-rs/core/src/image_preparation.rs

@@ -52,6 +52,7 @@ pub(crate) fn unified_image_budget_enabled(
 
 #[derive(Clone, Copy, Debug)]
 struct ImageOrigin<'a> {
+    thread_id: &'a str,
     message_role: Option<&'a str>,
     item_id: Option<&'a str>,
 }
@@ -118,6 +119,7 @@ impl ImagePreparationError {
 }
 
 pub(crate) async fn prepare_response_items(
+    thread_id: &str,
     items: &mut Vec<ResponseItem>,
     mode: ImagePreparationMode,
     resize_notice_mode: ImageResizeNoticeMode,
@@ -135,6 +137,7 @@ pub(crate) async fn prepare_response_items(
                 let resized_images = prepare_message_content(
                     &mut content,
                     ImageOrigin {
+                        thread_id,
                         message_role: Some(role.as_str()),
                         item_id: None,
                     },
@@ -157,6 +160,7 @@ pub(crate) async fn prepare_response_items(
                 call_id, output, ..
             } => {
                 prepare_tool_output(
+                    thread_id,
                     output,
                     call_id.as_deref(),
                     resize_notice_mode,
@@ -170,6 +174,7 @@ pub(crate) async fn prepare_response_items(
                 call_id, output, ..
             } => {
                 prepare_tool_output(
+                    thread_id,
                     output,
                     Some(call_id.as_str()),
                     resize_notice_mode,
@@ -205,6 +210,7 @@ pub(crate) async fn prepare_response_items(
 }
 
 async fn prepare_tool_output(
+    thread_id: &str,
     output: &mut FunctionCallOutputPayload,
     item_id: Option<&str>,
     resize_notice_mode: ImageResizeNoticeMode,
@@ -216,6 +222,7 @@ async fn prepare_tool_output(
     let resized_images = prepare_tool_output_content(
         content,
         ImageOrigin {
+            thread_id,
             message_role: None,
             item_id,
         },
@@ -349,6 +356,7 @@ async fn prepare_image(
     metadata.push(prepared.metadata(origin));
     let resize = prepared.resize;
     let request = UploadRequest {
+        thread_id: origin.thread_id.to_owned(),
         file_name: None,
         data: prepared.encoded.bytes.to_vec(),
     };

codex-rs/core/src/image_preparation_tests.rs

@@ -100,6 +100,7 @@ async fn preparation_preserves_small_image_bytes_and_replaces_remote_urls() {
     });
 
     prepare_response_items(
+        "image-preparation-thread",
         &mut items,
         ImagePreparationMode::DetailBased,
         ImageResizeNoticeMode::Disabled,
@@ -185,6 +186,7 @@ async fn detail_policies_apply_the_expected_budgets() {
         }];
 
         let metadata = prepare_response_items(
+            "image-preparation-thread",
             &mut items,
             ImagePreparationMode::DetailBased,
             ImageResizeNoticeMode::Disabled,
@@ -238,6 +240,7 @@ async fn preparation_reports_tool_output_item_id() {
         internal_chat_message_metadata_passthrough: None,
     }];
     let metadata = prepare_response_items(
+        "image-preparation-thread",
         &mut items,
         ImagePreparationMode::DetailBased,
         ImageResizeNoticeMode::Disabled,
@@ -274,6 +277,7 @@ async fn upload_failure_keeps_resized_image_inline() {
     }];
 
     prepare_response_items(
+        "image-preparation-thread",
         &mut items,
         ImagePreparationMode::DetailBased,
         ImageResizeNoticeMode::Disabled,
@@ -374,6 +378,7 @@ async fn resize_notices_count_file_backed_images_and_skip_failed_images() {
     ];
 
     prepare_response_items(
+        "image-preparation-thread",
         &mut items,
         ImagePreparationMode::DetailBased,
         ImageResizeNoticeMode::Enabled,
@@ -561,6 +566,7 @@ async fn preparation_replaces_only_failed_tool_images_and_preserves_metadata() {
     }];
 
     prepare_response_items(
+        "image-preparation-thread",
         &mut items,
         ImagePreparationMode::DetailBased,
         ImageResizeNoticeMode::Disabled,

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

@@ -1726,6 +1726,7 @@ impl Session {
         // inline bytes, while existing file references bypass preparation and remain unchanged.
         // Bound replay future size now that image preparation can await storage.
         let _ = Box::pin(prepare_image_response_items(
+            &self.thread_id.to_string(),
             &mut prepared_history,
             ImagePreparationMode::DetailBased,
             ImageResizeNoticeMode::Disabled,
@@ -3412,6 +3413,7 @@ impl Session {
         };
         // Keep nested image-upload futures out of every caller's future frame.
         let image_preparations = Box::pin(prepare_image_response_items(
+            &self.thread_id.to_string(),
             &mut items,
             image_preparation_mode,
             image_resize_notice_mode,

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

@@ -679,6 +679,10 @@ async fn resumed_history_only_emits_resize_notices_for_new_images() -> anyhow::R
         let [upload] = uploads.as_slice() else {
             panic!("only the new image should be uploaded");
         };
+        assert_eq!(
+            upload.thread_id,
+            resumed.session_configured.thread_id.to_string(),
+        );
         assert_eq!(
             image::load_from_memory(&upload.data)?.dimensions(),
             (2048, 768)