[BUG] Reasoning loop on repeated Read of same file offset — Claude Code v2.1.220 stops making progress after compaction

Summary

Claude Code v2.1.220 enters a reasoning deadlock: after context compaction, it repeatedly reads the same file at the same offset without making any code changes or tool calls beyond Read. The session becomes unresponsive to user input — every "continue" prompt triggers another identical Read, creating an infinite loop with zero progress.

Environment

• Claude Code: v2.1.220 (also observed in v2.1.219–v2.1.224 range per #84738)
• Platform: macOS 26.5.1 (darwin)
• Model: glm-5.2 (via ANTHROPIC_BASE_URL proxy)
• Session type: tmux window, long-running work session

Reproduction

1. Start a Claude Code session doing code refactoring (Go project, upload.go CheckRedirect fix)
2. Complete multiple Read + Edit operations on the same file
3. Context approaches compact threshold → /compact fires
4. After compaction, Claude attempts to continue the refactoring task
5. Claude enters a loop: Read upload.go offset=95 → Read upload.go offset=95 → Read upload.go offset=95 ...
6. Each "continue" user prompt triggers another Read of the same offset
7. No Edit, Write, or any tool call beyond Read is ever issued again

Observed Behavior

tmux capture shows the following pattern repeating 5+ times with no variation:

❯ 继续
  Thought for 7s
⏺ Read(upload.go, offset=95)

❯ 继续
  Thought for 8s
⏺ Read(upload.go, offset=95)

❯ 继续
  Thought for 8s
⏺ Read(upload.go, offset=95)

❯ ？你这是怎么了，怎么不往下走
  Thought for 3s
⏺ Read(upload.go, offset=95)

The session process is alive (pid=45593, dead=0) but produces no actionable output. The model appears stuck in a "understand the file" reasoning loop and never transitions to "edit the file".

Expected Behavior

After compaction, Claude should either:

• Complete the pending code change (Edit/Write upload.go)
• Ask the user a clarifying question
• Or at minimum vary its approach after the same Read yields no new insight

Related Issues

• #84738: Advisor turns double-count context usage (same version range, suggests broader context management issues)
• #86198: Slash command during advisor in-flight corrupts session (session state management fragility)

Workaround

Ctrl+C to interrupt the loop, then /clear to reset context. Re-issue the task with a more focused prompt. The bug may be related to post-compaction context reconstruction — reducing context pressure before compaction may help.

Severity

🔴 Fatal — the session becomes completely unusable after compaction. The only recovery is /clear (discarding all context), losing all prior work context. No graceful degradation path.