[codex-apps] Omit internal fields from file payloads (#31330)

## Summary

Codex Apps file parameters are exposed to the model as local paths,
uploaded at execution time, and rewritten into provided-file payloads
before the MCP tool call.

The rewrite currently forwards two internal upload fields, `uri` and
`file_size_bytes`, even though they are not part of the documented app
file-reference shape. Strict app schemas can reject those extra fields
before execution.

## Changes

- Stop copying `uri` and `file_size_bytes` into app-facing MCP
arguments.
- Keep the internal `UploadedOpenAiFile` result unchanged.
- Preserve the existing `download_url`, `file_id`, `mime_type`, and
`file_name` behavior for scalar and array file inputs.
- Verify the MCP invocation and post-tool hook receive exactly the
documented four-field payload against an `additionalProperties: false`
schema.

This intentionally does not add schema inspection or change how
`openai/fileParams` names are discovered.

## Validation

- `just test -p codex-core mcp_openai_file` (6 passed)
- `just test -p codex-core codex_apps_file_params_` (2 passed)
- `just fix -p codex-core`
- `just fmt`
- `git diff --check`

codex-rs/core/src/mcp_openai_file.rs

@@ -173,8 +173,6 @@ async fn build_uploaded_argument_value(
         "file_id": uploaded.file_id,
         "mime_type": uploaded.mime_type,
         "file_name": uploaded.file_name,
-        "uri": uploaded.uri,
-        "file_size_bytes": uploaded.file_size_bytes,
     }))
 }
 
@@ -300,8 +298,6 @@ mod tests {
                 "file_id": "file_123",
                 "mime_type": "text/csv",
                 "file_name": "file_report.csv",
-                "uri": "sediment://file_123",
-                "file_size_bytes": 5,
             })
         );
     }
@@ -404,8 +400,6 @@ mod tests {
                 "file_id": "file_123",
                 "mime_type": "text/csv",
                 "file_name": "file_report.csv",
-                "uri": "sediment://file_123",
-                "file_size_bytes": 5,
             }))
         );
     }
@@ -519,16 +513,12 @@ mod tests {
                     "file_id": "file_1",
                     "mime_type": "text/csv",
                     "file_name": "one.csv",
-                    "uri": "sediment://file_1",
-                    "file_size_bytes": 3,
                 },
                 {
                     "download_url": format!("{}/download/file_2", server.uri()),
                     "file_id": "file_2",
                     "mime_type": "text/csv",
                     "file_name": "two.csv",
-                    "uri": "sediment://file_2",
-                    "file_size_bytes": 3,
                 }
             ]))
         );

codex-rs/core/tests/common/apps_test_server.rs

@@ -553,9 +553,13 @@ impl Respond for CodexAppsJsonRpcResponder {
                                             "type": "object",
                                             "description": "Document file payload.",
                                             "properties": {
-                                                "file_id": { "type": "string" }
+                                                "download_url": { "type": "string" },
+                                                "file_id": { "type": "string" },
+                                                "mime_type": { "type": "string" },
+                                                "file_name": { "type": "string" }
                                             },
-                                            "required": ["file_id"]
+                                            "required": ["download_url", "file_id"],
+                                            "additionalProperties": false
                                         }
                                     },
                                     "required": ["file"],

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

@@ -91,14 +91,12 @@ fn read_post_tool_use_hook_inputs(home: &Path) -> Result<Vec<Value>> {
         .collect()
 }
 
-fn uploaded_file(server: &MockServer, file_size_bytes: u64) -> Value {
+fn uploaded_file(server: &MockServer) -> Value {
     json!({
         "download_url": format!("{}/download/file_123", server.uri()),
         "file_id": "file_123",
         "mime_type": "text/plain",
         "file_name": "report.txt",
-        "uri": "sediment://file_123",
-        "file_size_bytes": file_size_bytes,
     })
 }
 
@@ -230,7 +228,7 @@ async fn codex_apps_file_params_upload_environment_files_before_mcp_tool_call()
 
     assert_eq!(
         apps_tool_call.pointer("/params/arguments/file"),
-        Some(&uploaded_file(&server, STREAMED_FILE_SIZE as u64))
+        Some(&uploaded_file(&server))
     );
     assert_eq!(
         apps_tool_call.pointer("/params/_meta/_codex_apps"),
@@ -267,10 +265,7 @@ async fn codex_apps_file_params_pass_uploaded_file_to_post_tool_use_hook() -> Re
 
     let hook_inputs = read_post_tool_use_hook_inputs(test.codex_home_path())?;
     assert_eq!(hook_inputs.len(), 1);
-    assert_eq!(
-        hook_inputs[0]["tool_input"]["file"],
-        uploaded_file(&server, /*file_size_bytes*/ 11)
-    );
+    assert_eq!(hook_inputs[0]["tool_input"]["file"], uploaded_file(&server));
 
     server.verify().await;
     Ok(())