CPU usage at max.

[bjornmadsen]

Describe the bug

Copilot CLI feedback - 2026-06-24

Two related issues from a single long-running session.

Issue 1: agent-induced data loss via hardlink "backup"

While trying to mitigate Issue 2 (below), I (the agent) ran:

ln events.jsonl events.jsonl.bak-20260624
: > events.jsonl

Intending to keep a backup before truncating the 233 MB events log.
Because ln creates a hardlink (shared inode), truncating one name
truncated both. The 233 MB raw transcript was destroyed.

The session survived because the in-prompt summary, plan.md,
checkpoints/, session.db, files/ and stored memories were intact.

What would help

• Document in the agent system prompt or tool guidance that
  ln is not a backup primitive. Use cp (or cp --reflink=auto
  on btrfs/xfs) to take an independent copy.
• Or: ship a built-in /session-archive or /session-compact
  command so users (and agents) don't have to invent file-level
  tricks on a live session.

Issue 2: events.jsonl growth pins CPU on long sessions

Single-session events.jsonl grew to 233 MB over ~1200 turns.
Starting copilot from a directory that triggers session resume
pegs ~5 CPU cores ("indexer berserk") for 20+ minutes.

lsof shows events.jsonl is NOT held open during the session
(only session.db is) - so it appears to be read whole on
resume or on summary regeneration.

What would help

• Cap events.jsonl size, or roll/compact it as part of the
  existing summarization pass.
• Don't re-parse the whole file on every resume; rely on
  session.db + the last summary checkpoint.
• Or expose --no-resume-events / .copilotignore for the
  session log itself.

Issue 3 (related): no .copilotignore and no scan-depth flag

Starting copilot from ~/github (a directory of ~60 sibling
repos, not a single repo) appears to walk every subdir for
CLAUDE.md / AGENTS.md / .github/instructions. -C <repo> is
the only workaround and defeats cross-repo work.

What would help

• .copilotignore honoured at the cwd.
• --scan-depth N or --no-scan-children.
• Or: scan lazily, only when the user references a path.

Session id

7801c0d9-4a25-47bf-aee7-bb26e20ff3c2

Affected version

No response

Steps to reproduce the behavior

1. Open VScode.
2. Start copilot.
3. Watch CPU usage rise to max.

Expected behavior

Not seeing CPU usage over the normal 1-2%.

Additional context

No response