Codex App: @ filename-only search shows conversations, while a directory prefix reveals the matching file

What version of the Codex App are you using (From “About Codex” dialog)?

26.908.70816 (build 9275), read from the installed application's Info.plist. Bundle identifier: com.openai.codex.

What subscription do you have?

prolite (planType reported by the signed-in account's usage API; recorded verbatim).

What platform is your computer?

macOS 27.0 (build 26A428), Apple Silicon / arm64.

uname -mprs: Darwin 27.0.0 arm64 arm.

What issue are you seeing?

In a project-associated task, searching the @ mention picker using only a filename fragment shows conversation candidates but no matching project file. Adding a directory prefix to the same fragment makes a file candidate appear.

The original report concerned finding a PDF. The concrete screenshot comparison below demonstrates the problem with an XLSX file, so this is not established as a PDF-specific defect.

What steps can reproduce the bug?

Observed sequence in the same project task (Chinese-language UI):

1. Type @最终版 (final version) in the composer.
2. The visible picker shows eight conversation entries and no file candidates. None of the displayed conversation titles visibly contains 最终版.
3. Change the input to @教案/最终版 (lesson plans/final version).
4. The picker now shows 人工智能教学原理与算法_12次课程与助教分工_最终版.xlsx, with an Excel icon and directory label 教案.

Both screenshots are attached in this comment. Detailed screenshot interpretation.

This records the observed behavior; it has not been independently reproduced in a clean project.

What is the expected behavior?

Typing a filename fragment such as @最终版 should make matching project files discoverable and selectable without requiring the user to know their directory. The need is fuzzy/partial filename discovery.

A Files / Conversations filter or separate result groups could help ensure that file candidates remain accessible when conversations are also suggested.

Additional information

• The screenshots show a project-associated task, not a projectless chat.
• Adding a directory prefix exposes the XLSX candidate in this example. This is still a partial filename, not a complete file path. It is a workaround for this example, not a resolution of filename-only discovery.
• PDFs are visible in the conversation history, but the screenshots do not establish whether those PDFs match the query or are searchable.
• The cause remains unknown. The screenshots do not establish whether this is ranking, query filtering, or selection of which resource types to search. Overlapping conversation titles are not established as a necessary condition.

Reproduce the @ picker behavior in a project-associated task using the filename-only and directory-prefixed queries described. Trace how the picker searches conversations and project files, and determine whether filtering, ranking, or resource selection omits filename-only matches. Done means matching project files appear and remain selectable when users search with a filename fragment alone.