Feature request: reload .github/instructions mid-session (long-running sessions never pick up instruction updates)

Observed behavior

Custom instructions (.github/instructions/*.instructions.md) are loaded once at session start. A long-running session — kept alive across many compactions over days — never sees any later edits to those files. We measured a session that crossed 200+ compaction boundaries over ~2.5 weeks: the instruction content it held stayed at its boot-time version the whole way, while the on-disk files moved dozens of revisions ahead. Compaction/summarization does not re-read the instruction files, so there is currently no way for updated standing instructions to reach an in-flight session at all.

Why it matters

For anyone using instruction files as living, standing guidance (conventions, safety rules, project state), the effective delivery is boot-only. The longer and more productive a session, the staler its standing instructions — the sessions you care most about are the ones guaranteed to be furthest behind. Restarting the session works but discards its accumulated context, which is exactly what long-running sessions exist to keep.

Ask

Any one of these would resolve it:

1. An explicit reload command/verb (e.g. /reload-instructions) that re-reads the instruction files into the live session, or
2. Automatic re-read of instruction files at each compaction boundary (a natural moment, since context is being rebuilt anyway), or
3. A documented statement that instructions are boot-only, so users can design around it deliberately (e.g., scheduled restarts).

Environment

Copilot CLI on Windows, long-lived sessions resumed across days, instruction files under .github/instructions/ in the working directory.

首先使用 .github/instructions/*.instructions.md 下的文件复现一个长期运行的 Copilot CLI 会话，然后比较压缩前后的指令内容。跟踪初始指令加载以及压缩/摘要行为；当更新后的指令能够到达正在运行的会话，或仅在启动时加载的行为已得到明确记录时，即视为完成。