No context window visibility or compaction notification in chat sessions

[sonydogg]

Summary

There is no UI indicator in the GitHub App showing context window usage, and context compaction happens silently with no notification to the user.

Expected behaviour

• A visible indicator showing tokens used / remaining in the current session (similar to how the model name is shown in the dropdown)
• A notification or visual cue when context compaction fires (summarizing older turns)
• Ideally: some indication of what was compacted or dropped so the user can decide whether to start a fresh session

Actual behaviour

• No token usage indicator anywhere in the UI
• Context compaction fires silently during long sessions
• Older instructions (including repo-level AGENTS.md content loaded at session start) can be silently compressed mid-session with no warning
• Users have no way to know their agent is operating on a summarized version of earlier instructions without manually inspecting ~/.copilot/session-state//events.jsonl

Impact

• Agents that correctly followed repo instructions early in a session may stop following them after compaction, with no observable cause
• Power users running long working sessions (second brain workflows, multi-file refactors) have no signal when to start a fresh session to restore full context fidelity
• Particularly acute for repos with dense AGENTS.md / copilot-instructions.md files where instruction loss mid-session causes behavioural drift

Observed in

GitHub Copilot native desktop app (Windows), long chat session (~25 turns). The raw event data exists at ~/.copilot/session-state//events.jsonl but is not surfaced in the UI.