Spec Kit Limitations with 3rd Party Claude Agent in Copilot.

[Eric-A99]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version:
  Version: 1.109.5 (user setup)
  Commit: 0725862
  Date: 2026-02-19T19:43:32.382Z
  Electron: 39.3.0
  ElectronBuildId: 13313481
  Chromium: 142.0.7444.265
  Node.js: 22.21.1
  V8: 14.2.231.22-electron.0

• OS Version:
  Windows_NT x64 10.0.26200

Steps to Reproduce:

Noticing limitations with using Spec Kit with 3rd party agents in VS Code (Claude SDK).

Repeatedly falls into plan mode & gets stuck there unless the following instructions are used:

Copilot Instructions (Repo-Wide)

Workflow

• ALWAYS follow the Spec Kit workflow: /specify → /plan → /tasks → /implement
• Read specs/, plan.md, and tasks.md BEFORE starting any implementation
• The constitution at .specify/memory/constitution.md is the source of truth
• NEVER generate your own instructions file or deviate from the Spec Kit flow

Additionally, the Claude Agent in VS Code does not pick up slash commands tied to Spec Kit, unlike when using the Copilot harness or using Spec Kit with Claude Code directly.

[TylerLeonhardt]

are these slash commands implemented as skills and placed in the .claude folder?

[Eric-A99]

@PabTorre - are you able to share more details on this?

[PabTorre]

are these slash commands implemented as skills and placed in the .claude folder?

Yeah, we have the slash commands in the folder, they work with Claude Code in the same project.

[TylerLeonhardt]

Repeatedly falls into plan mode & gets stuck there unless the following instructions are used

Can you elaborate on "gets stuck there" is the agent not attempting to exit plan mode? It has that tool, so it should be able to.

[PabTorre]

Can you elaborate on "gets stuck there" is the agent not attempting to exit plan mode? It has that tool, so it should be able to.

There's 2 different problems mixed up here.

1. when using delegate to claude SDK , there's no slash commands.
2. when using local, with spec kit's defautl install for Copilot, you start a new feature /speckit.specify and halfway through the agent's though process it switches from Agent to Plan on its own, but then it is unable to switch back from plan to agent to write take the steps required by speckit's specify command, like creating a feature branch and a folder in specs/ with the relevant documentation for this feature... it requires a mouse click to switch it back to agent where it takes a few steps and gets stuck in plan mode again... Feels like the built in plan mode is fighting against speckit's slash command. This can be fixed in the copilot-instructions.md file ... but it means that new commers to speckit run into an issue they need to fix out of the box , instead of it "just working".

sample copilot-instruction

Copilot Instructions (Repo-Wide)

Workflow

• ALWAYS follow the Spec Kit workflow: /specify → /plan → /tasks → /implement
• Read specs/, plan.md, and tasks.md BEFORE starting any implementation
• The constitution at .specify/memory/constitution.md is the source of truth
• NEVER generate your own instructions file or deviate from the Spec Kit flow
  ....

[TylerLeonhardt]

We should separate the two issues into two issues, it's way easier to digest that way.

when using delegate to claude SDK , there's no slash commands.

that's this #287659 - a known issue that I wanna fix next week.

when using local

So the second problem is not related to Claude integration if I'm hearing you right. It's Local. Sounds like there's a bug in how Local switches agents. @sbatten this is a feature you implemented, yes?