[BUG] Opus 4.8 (1M): multi-minute freeze, then off-topic / non-sequitur reply to a conversation that never happened (v2.1.185/2.1.186)

Preflight Checklist

• [x] I have searched existing issues for similar behavior
• [x] This report contains NO sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Model freezes for minutes, then replies with off-topic / non-sequitur content.

Summary

On Opus 4.8 (1M context), the assistant intermittently freezes for several
minutes and then answers with content that has nothing to do with my question.
The reply reads as if the model is part-way through a different conversation
that never actually happened. Once it slips into this state, it keeps replying
to that non-existent thread and ignores what I actually typed, until I force a
restart. This started about two days ago and was not happening before.

Environment

• Claude Code: v2.1.185 (when it occurred) / v2.1.186 (current)
• Model: claude-opus-4-8 (1M context)
• OS: macOS 26.5.1, arm64

Steps / What happens

1. I type a short, normal follow-up question (plain text — no voice input, no

special characters).

1. The turn hangs for several minutes (~8–9 min in the captured case).
2. The assistant then returns a reply that is a non-sequitur: it talks about

a topic that appears nowhere earlier in the session (e.g. "still empty,
not recovered… switching to web search"), as if continuing some other task.

1. Following turns keep tracking that fabricated thread and ignore my real

question. I have to abandon the session and open a new one to recover.

Evidence (from the local session transcript)

• Local session id: 6523e5b0-4472-42c5-9394-567e94228dc9
• The transcript shows an ~8m42s gap between my prompt and the assistant reply.
• The reply's thinking block is empty.
• The off-topic text is generated by the model — it does not match any prior

user or assistant turn in the session.

Expected behavior

The assistant should either answer the question I actually asked, or surface an
explicit error — not stall for minutes and then reply to a conversation that
never took place.

Impact

When it happens the session becomes unusable and has to be discarded. It is
intermittent and can strike on any question, which makes it hard to predict or
work around.