Add under-development original-resolution view_image support (#13050)

## Summary

Add original-resolution support for `view_image` behind the
under-development `view_image_original_resolution` feature flag.

When the flag is enabled and the target model is `gpt-5.3-codex` or
newer, `view_image` now preserves original PNG/JPEG/WebP bytes and sends
`detail: "original"` to the Responses API instead of using the legacy
resize/compress path.

## What changed

- Added `view_image_original_resolution` as an under-development feature
flag.
- Added `ImageDetail` to the protocol models and support for serializing
`detail: "original"` on tool-returned images.
- Added `PromptImageMode::Original` to `codex-utils-image`.
  - Preserves original PNG/JPEG/WebP bytes.
  - Keeps legacy behavior for the resize path.
- Updated `view_image` to:
- use the shared `local_image_content_items_with_label_number(...)`
helper in both code paths
  - select original-resolution mode only when:
    - the feature flag is enabled, and
    - the model slug parses as `gpt-5.3-codex` or newer
- Kept local user image attachments on the existing resize path; this
change is specific to `view_image`.
- Updated history/image accounting so only `detail: "original"` images
use the docs-based GPT-5 image cost calculation; legacy images still use
the old fixed estimate.
- Added JS REPL guidance, gated on the same feature flag, to prefer JPEG
at 85% quality unless lossless is required, while still allowing other
formats when explicitly requested.
- Updated tests and helper code that construct
`FunctionCallOutputContentItem::InputImage` to carry the new `detail`
field.

## Behavior

### Feature off
- `view_image` keeps the existing resize/re-encode behavior.
- History estimation keeps the existing fixed-cost heuristic.

### Feature on + `gpt-5.3-codex+`
- `view_image` sends original-resolution images with `detail:
"original"`.
- PNG/JPEG/WebP source bytes are preserved when possible.
- History estimation uses the GPT-5 docs-based image-cost calculation
for those `detail: "original"` images.


#### [git stack](https://github.com/magus/git-stack-cli)
- 👉 `1` https://github.com/openai/codex/pull/13050
- ⏳ `2` https://github.com/openai/codex/pull/13331
- ⏳ `3` https://github.com/openai/codex/pull/13049

codex-rs/core/src/tools/context.rs

@@ -222,6 +222,7 @@ mod tests {
                 },
                 FunctionCallOutputContentItem::InputImage {
                     image_url: "data:image/png;base64,AAA".to_string(),
+                    detail: None,
                 },
                 FunctionCallOutputContentItem::InputText {
                     text: "line 2".to_string(),
@@ -239,6 +240,7 @@ mod tests {
                     },
                     FunctionCallOutputContentItem::InputImage {
                         image_url: "data:image/png;base64,AAA".to_string(),
+                        detail: None,
                     },
                     FunctionCallOutputContentItem::InputText {
                         text: "line 2".to_string(),

codex-rs/core/src/tools/handlers/view_image.rs

@@ -1,10 +1,15 @@
 use async_trait::async_trait;
+use codex_protocol::models::ContentItem;
 use codex_protocol::models::FunctionCallOutputBody;
 use codex_protocol::models::FunctionCallOutputContentItem;
+use codex_protocol::models::ImageDetail;
+use codex_protocol::models::local_image_content_items_with_label_number;
 use codex_protocol::openai_models::InputModality;
+use codex_utils_image::PromptImageMode;
 use serde::Deserialize;
 use tokio::fs;
 
+use crate::features::Feature;
 use crate::function_tool::FunctionCallError;
 use crate::protocol::EventMsg;
 use crate::protocol::ViewImageToolCallEvent;
@@ -14,8 +19,6 @@ use crate::tools::context::ToolPayload;
 use crate::tools::handlers::parse_arguments;
 use crate::tools::registry::ToolHandler;
 use crate::tools::registry::ToolKind;
-use codex_protocol::models::ContentItem;
-use codex_protocol::models::local_image_content_items_with_label_number;
 
 pub struct ViewImageHandler;
 
@@ -81,15 +84,26 @@ impl ToolHandler for ViewImageHandler {
         }
         let event_path = abs_path.clone();
 
-        let content = local_image_content_items_with_label_number(&abs_path, None);
-        let content = content
+        let use_original_detail = turn.config.features.enabled(Feature::ImageDetailOriginal)
+            && turn.model_info.supports_image_detail_original;
+        let image_mode = if use_original_detail {
+            PromptImageMode::Original
+        } else {
+            PromptImageMode::ResizeToFit
+        };
+        let image_detail = use_original_detail.then_some(ImageDetail::Original);
+
+        let content = local_image_content_items_with_label_number(&abs_path, None, image_mode)
             .into_iter()
             .map(|item| match item {
                 ContentItem::InputText { text } => {
                     FunctionCallOutputContentItem::InputText { text }
                 }
                 ContentItem::InputImage { image_url } => {
-                    FunctionCallOutputContentItem::InputImage { image_url }
+                    FunctionCallOutputContentItem::InputImage {
+                        image_url,
+                        detail: image_detail,
+                    }
                 }
                 ContentItem::OutputText { text } => {
                     FunctionCallOutputContentItem::InputText { text }

codex-rs/core/src/tools/js_repl/mod.rs

@@ -1900,6 +1900,7 @@ mod tests {
             output: FunctionCallOutputPayload::from_content_items(vec![
                 FunctionCallOutputContentItem::InputImage {
                     image_url: "data:image/png;base64,abcd".to_string(),
+                    detail: None,
                 },
             ]),
         };
@@ -1929,6 +1930,7 @@ mod tests {
             output: FunctionCallOutputPayload::from_content_items(vec![
                 FunctionCallOutputContentItem::InputImage {
                     image_url: "data:image/png;base64,abcd".to_string(),
+                    detail: None,
                 },
             ]),
         };
@@ -2417,15 +2419,17 @@ console.log(out.output?.body?.text ?? "");
                 image_url:
                     "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR4nGP4z8DwHwAFAAH/iZk9HQAAAABJRU5ErkJggg=="
                         .to_string(),
+                detail: None,
             }]
             .as_slice()
         );
-        let [FunctionCallOutputContentItem::InputImage { image_url }] =
+        let [FunctionCallOutputContentItem::InputImage { image_url, detail }] =
             result.content_items.as_slice()
         else {
             panic!("view_image should return exactly one input_image content item");
         };
         assert!(image_url.starts_with("data:image/png;base64,"));
+        assert_eq!(*detail, None);
         assert!(session.get_pending_input().await.is_empty());
 
         Ok(())
@@ -2515,6 +2519,7 @@ console.log(out.type);
                 },
                 FunctionCallOutputContentItem::InputImage {
                     image_url: image_url.to_string(),
+                    detail: None,
                 },
             ]
         );