What causes "String(e?.message ?? e)" in Hmbown/CodeWhale?

Check the upstream server logs and the 500 body's error text for the root cause

String(e?.message ?? e)

Error message

String(e?.message ?? e)

What it means

This is the proxy's top-level error funnel: if translating or relaying the upstream SSE stream throws, the server responds 500 with { error: <first 2000 chars of the exception message> }. The bare expression String(e?.message ?? e) is the message-extraction code, so the observed text mirrors whatever upstream/translation error occurred.

Solutions

Check the upstream server logs and the 500 body's error text for the root cause
Verify upstream API credentials and model name
Confirm the upstream still emits Responses-style SSE that the translator understands
Retry the request; if persistent, inspect translateResponsesSseToChat against the current upstream format

Defensive patterns

Strategy: try-catch

Validate before calling

// pre-flight upstream check
const pre = await fetch(`${UPSTREAM_BASE}/v1/chat/completions`, { method: "POST", headers, body: JSON.stringify({ model, messages: [], max_tokens: 1 }) });
if (!pre.ok) throw new Error(`upstream unhealthy: ${pre.status}`);

Try / catch

try {
  await streamFromUpstream();
} catch (e) {
  console.error("proxy 500 origin:", String(e?.message ?? e).slice(0, 2000));
  // inspect upstream status/format before retrying
}

Prevention

Validate upstream credentials and model names before streaming
Watch for upstream API format changes that break SSE translation
Set upstream timeouts and retries
Log the 500 body's error field — it contains the truncated root cause

When it happens

Trigger: Upstream returns non-SSE or malformed data, translateResponsesSseToChat throws on unexpected chunk shapes, the upstream request itself fails mid-stream, or an exception is thrown while writing the response.

Common situations: Upstream auth failure, upstream API change breaking the SSE translation, network drop between proxy and OpenAI, or a timeout aborting the fetch mid-stream.

Related errors

AI-assisted analysis of Hmbown/CodeWhale@433685b202 (2026-09-15). Data as JSON: /api/errors/af094912d6160771. Report an issue: GitHub.

Appendix: source

Thrown at scripts/opencode-chat2responses-proxy.mjs:199

        const { done, value } = await reader.read();
        if (done) break;
        buf += decoder.decode(value, { stream: true });
        let idx;
        while ((idx = buf.indexOf("\n\n")) !== -1) {
          const chunk = buf.slice(0, idx + 2);
          buf = buf.slice(idx + 2);
          const translated = translateResponsesSseToChat(chunk, model);
          if (translated) res.write(translated);
        }
      }
      if (buf.trim()) {
        const translated = translateResponsesSseToChat(buf, model);
        if (translated) res.write(translated);
      }
      res.write(`data: [DONE]\n\n`);
      res.end();
    } catch (e) {
      res.writeHead(500, { "content-type": "application/json" });
      res.end(JSON.stringify({ error: String(e?.message ?? e).slice(0, 2000) }));
    }
  });
});

server.listen(LISTEN_PORT, "127.0.0.1", () => {
  console.log(`[opencode-proxy] listening on http://127.0.0.1:${LISTEN_PORT}/v1/chat/completions -> ${UPSTREAM_BASE}${UPSTREAM_PATH}`);
  console.log(`[opencode-proxy] health: http://127.0.0.1:${LISTEN_PORT}/health`);
});

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