Codex for Visual Studio

The IDE-native Codex agent for .NET developers on Windows — no terminal switching.

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Inspiration

The Codex CLI is excellent, but on Windows it lives in a terminal window next to Visual Studio — not inside it. Every code review meant alt-tabbing, re-pasting paths, and losing the IDE's own context. VS Code and other editors already had first-class agent integrations, and Visual Studio — still the daily driver for a huge amount of .NET, C++, and enterprise work — had nothing that spoke the Codex app-server protocol.

What it does

Codex for Visual Studio runs the local Codex CLI app server from inside the IDE and surfaces it as a chat tool window (View > Other Windows > Codex).

  • Streaming chat with reasoning blocks, agent messages, and a virtualized transcript that stays responsive on long turns.
  • Slash commands — /model, /reasoning, /fast, /review, /permissions, /status and more — with in-composer suggestions.
  • Workspace context: #-mention file suggestions, file attachments via the SDK picker, and empty-workspace scaffolding that creates a root-level .slnx(or .sln) without imposing a project template on you.
  • Usage and limits shown in a panel, with freshness scoped to the connection generation so a stale read can never overwrite newer data.

How we built it

Clone from public repo.

gh repo clone kkamegawa/vsextensionforcodex

and build solution.

dotnet restore CodexForVisualStudio.slnx
dotnet build CodexForVisualStudio.slnx -c Release --no-restore

Challenges we ran into

  • The OOP extension model. It's so harder to implement to AI.
  • It's so hard to implement rendering in Visual Studio Extension panel.
  • "Where's codex CLI?" We can install codex cli with several way. Which cli right now?

Accomplishments that we're proud of

  • Smooth integration Codex CLI and Visual Studio. Many of feature support in Visual Studio

What we learned

  • Easy to integrate Codex App Server and other programs.
  • In honest, we would like to use Codex SDK. However, .NET SDK for Codex don't exist. It would challenge to .NET SDK for Codex.

What's next for Codex for Visual Studio

  • support custom skill file.
  • improve rendering. some area didn't support dark thema.
  • Drag-and-drop attachments, if and when Visual Studio Extensibility exposes a supported Remote UI file-drop contract.
  • migrate Codex App Server to Codex SDK
  • other features...

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