Error: 'usage credits required for 1M context' when session grows long on non-1M model

Summary

When a Claude Code session accumulates enough context, the CLI automatically attempts to switch to a 1M-context model. If the user's plan does not include that feature, the session fails with:

usage credits required for 1M context

No fallback occurs — the session is blocked until the user manually runs /compact.

Expected behaviour

Claude Code should either:

1. Stay on the configured model (e.g. claude-sonnet-4-6, 200K context) and trigger automatic compaction when approaching its limit, or
2. Show a clear, actionable error with a suggested fix (e.g. "run /compact to reduce context size")

Actual behaviour

Session fails with a billing/credits error that references "1M context" even though the user is not on a 1M-context model and did not request one.

Environment

• Model: claude-sonnet-4-6
• Platform: Windows 11 (Claude Code CLI + Windsurf integration)
• Trigger: long session with large startup context (session logs, memory files, hook output loaded at startup)

Workaround

Run /compact before context grows too large.

Notes

The startup hook injects significant context each session (handoff notes, memory index, session history). Combined with tool outputs from a long session this pushes toward the 200K limit quickly, at which point the automatic 1M-context upsell fires — but fails silently for users who don't have that entitlement.