[Bug] TypeError: Cannot read properties of undefined (reading 'filter')

[tamasmiklossy]

Environment

• OS: Windows
• Eclipse Version: 2026-06 (4.40.0)
• Plugin Version: 0.21.0.202608060743

Describe the bug
The following error occurs in the Agent mode when there is no project in the workspace:

!ENTRY org.eclipse.lsp4e 4 0 2026-08-26 07:45:09.023
!MESSAGE [LS:GitHub Copilot Language Server][Error]	[chat] Error processing turn 72df12fd-e941-4394-adb4-2b5917d14ed7 TypeError: Cannot read properties of undefined (reading 'filter') (at tsx element AgentPrompt > UserMessage > SubagentListPrompt)
    at y0.collect (C:\snapshot\copilot-language-server-internal\dist\main.js:2411:12762)
    at t.listCustomAgents (C:\snapshot\copilot-language-server-internal\dist\main.js:2411:23507)
    at async $de.getAgents (C:\snapshot\copilot-language-server-internal\dist\main.js:3333:954)
    at async $de.getAgentsForModelDispatch (C:\snapshot\copilot-language-server-internal\dist\main.js:3333:1202)
    at async Itt.renderCopilot (C:\snapshot\copilot-language-server-internal\dist\main.js:3333:3037)
    at async annotateError (C:\snapshot\copilot-language-server-internal\dist\main.js:69:4311)
    at async C:\snapshot\copilot-language-server-internal\dist\main.js:67:29695
    at async Promise.all (index 0)
    at async jZe._processPromptPieces (C:\snapshot\copilot-language-server-internal\dist\main.js:67:29606)
    at async jZe._processPromptRenderPiece (C:\snapshot\copilot-language-server-internal\dist\main.js:67:30200)

!ENTRY org.eclipse.lsp4e 4 0 2026-08-26 07:45:09.024
!MESSAGE [LS:GitHub Copilot Language Server][Error]	[agenticTurnProcessor] Error in processing turn 72df12fd-e941-4394-adb4-2b5917d14ed7 TypeError: Cannot read properties of undefined (reading 'filter') (at tsx element AgentPrompt > UserMessage > SubagentListPrompt)
    at y0.collect (C:\snapshot\copilot-language-server-internal\dist\main.js:2411:12762)
    at t.listCustomAgents (C:\snapshot\copilot-language-server-internal\dist\main.js:2411:23507)
    at async $de.getAgents (C:\snapshot\copilot-language-server-internal\dist\main.js:3333:954)
    at async $de.getAgentsForModelDispatch (C:\snapshot\copilot-language-server-internal\dist\main.js:3333:1202)
    at async Itt.renderCopilot (C:\snapshot\copilot-language-server-internal\dist\main.js:3333:3037)
    at async annotateError (C:\snapshot\copilot-language-server-internal\dist\main.js:69:4311)
    at async C:\snapshot\copilot-language-server-internal\dist\main.js:67:29695
    at async Promise.all (index 0)
    at async jZe._processPromptPieces (C:\snapshot\copilot-language-server-internal\dist\main.js:67:29606)
    at async jZe._processPromptRenderPiece (C:\snapshot\copilot-language-server-internal\dist\main.js:67:30200)

To Reproduce
Steps to reproduce the behavior:

1. Open a new empty workspace with no project imported into it
2. Ensure on the Chat window Agent mode is selected
3. Ask a question to Copilot e.g: "What day is today?"
4. See error

Expected behavior
No error should appear

Screenshots

Additional context
The problem does not occur if Ask mode is selected