Claude/Anthropic 500/502/503/504 server errors are not retried

[rich-jojo]

Bug Report

What happened?

When Anthropic's API returns a transient server error (HTTP 500, 502, 503, or 504), OpenCode does not retry the request — it immediately fails with an error like:

{"type":"api_error","message":"Claude API returned a server error. This is usually temporary — try again in a moment."}

Expected behavior

Transient server errors should be retried with exponential backoff, the same way rate-limit errors (429) and overload errors (529) already are.

Root cause

In packages/opencode/src/provider/error.ts, parseAPICallError() trusts input.error.isRetryable from the Vercel AI SDK for non-OpenAI providers. The @ai-sdk/anthropic package only marks status codes 429 and 529 as isRetryable: true. Generic 500/502/503/504 responses get isRetryable: false, so SessionRetry.retryable() returns undefined and the retry loop stops immediately.

OpenAI already has a special override in isOpenAiErrorRetryable() — the same approach needs to be applied universally.

Environment

• OpenCode version: latest dev
• Provider: Anthropic (Claude)

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Anthropic 5xx errors incorrectly marked non-retryable, stopping agent loop #19394: Anthropic 5xx errors incorrectly marked non-retryable, stopping agent loop — nearly identical root cause, same files, same proposed fix
• fix: 5xx errors from non-standard providers are not retried #19203: fix: 5xx errors from non-standard providers are not retried — same general area (non-retryable 5xx errors)
• Anthropic overloaded_error is not retried, halts session #20384: Anthropic overloaded_error is not retried, halts session — closely related Anthropic retry classification issue

If you believe this is distinct, please clarify how it differs from the above (especially #19394, which describes the same root cause in error.ts).

[rich-jojo]

Closing as a duplicate of #19394. Both describe the same Anthropic 5xx APICallError retry-classification path in packages/opencode/src/provider/error.ts.