[BUG] API Error 500 (no body) on Opus 4.7 with 1M context, intermittent across different requests

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Persistent intermittent 500 errors throughout a single session. Roughly 50% failure rate per request. Failures hit different requests rather than the same one looping, so this is not a poisoned tool result or stuck session state. Retries eventually succeed (typically attempt 2 or 3 of 10), then the next turn fails again (10/10) and shows the full API 500 error message. /login reauth noticeably improved the success rate but did not eliminate the failures.
The in product /feedback command also returns 500, which is why I'm filing here instead of through feedback.
A separate Claude.ai web session briefly wobbled at the same time, suggesting the issue may extend past just the Opus 4.7 1M pool.

What Should Happen?

Requests to Claude Code complete successfully within normal latency. Retries should not be needed for routine requests on a healthy session with low context usage.

Error Messages/Logs

API Error: 500 status code (no body). This is a server-side issue, usually temporary, try again in a moment. If it persists, check status.claude.com.

Couldn't send feedback (server returned 500). If it keeps failing, you can file at https://github.com/anthropics/claude-code/issues instead.

Steps to Reproduce

Not reliably reproducible on demand. The failure correlates with periods when the Opus 4.7 backend pool is strained (see "Additional Information" for related incident history).
Approximate setup at time of failure:

Start a Claude Code session on a Claude Max account, default model (Opus 4.7 with 1M context)
Work normally, including parallel subagents and MCP tool calls
Around 32% context usage, requests begin returning 500 (no body) intermittently
Retries succeed after 2 to 3 attempts; failures resume on subsequent turns
/feedback also returns 500

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.146

Claude Code Version

2.1.146

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

Using Ghostty

Status page (status.claude.com) showed no incidents at time of failure, but Opus 4.7 has had "Elevated errors" incidents recurringly over the past two weeks (May 20, 19, 18, 14, 12, 8, 7). Likely the same underlying issue not yet crossing the public reporting threshold today.
Happy to provide session ID privately if useful for diagnosis. Omitting here for privacy.