What causes "connection to Cohere API failed with status %d" in weaviate/weaviate?

Log bodyBytes on non-200 statuses to capture what was actually returned

connection to Cohere API failed with status %d

Error message

connection to Cohere API failed with status %d

What it means

A formatted error raised when the Cohere rerank endpoint returned a non-200 status and the body either had no parseable message (the variant without %s). It means the client could not obtain any descriptive message from Cohere for the failure.

Source

Thrown at modules/reranker-cohere/clients/ranker.go:146

		return nil, errors.Wrap(err, "send POST request")
	}
	defer res.Body.Close()

	bodyBytes, err := io.ReadAll(res.Body)
	if err != nil {
		return nil, errors.Wrap(err, "read response body")
	}

	if res.StatusCode != 200 {
		var apiError cohereApiError
		err = json.Unmarshal(bodyBytes, &apiError)
		if err != nil {
			return nil, errors.Wrap(err, "unmarshal error from response body")
		}
		if apiError.Message != "" {
			return nil, errors.Errorf("connection to Cohere API failed with status %d: %s", res.StatusCode, apiError.Message)
		}
		return nil, errors.Errorf("connection to Cohere API failed with status %d", res.StatusCode)
	}

	var rankResponse RankResponse
	if err := json.Unmarshal(bodyBytes, &rankResponse); err != nil {
		return nil, fmt.Errorf("failed to parse reranker response (status %d): %w", res.StatusCode, err)
	}
	return c.toDocumentScores(documents, rankResponse.Results), nil
}

func (c *client) chunkDocuments(documents []string, chunkSize int) [][]string {
	var requests [][]string
	for i := 0; i < len(documents); i += chunkSize {
		end := i + chunkSize

		if end > len(documents) {
			end = len(documents)
		}

View on GitHub (pinned to 75aa4b6d11)

Solutions

Log bodyBytes on non-200 statuses to capture what was actually returned
Check status code in the message: 401/403 -> fix API key; 429 -> backoff; 5xx -> retry or check Cohere status page
Bypass intermediaries by testing directly against https://api.cohere.com
Update the module/client so cohereApiError matches Cohere's current error schema

Example fix

// before: opaque error
return nil, errors.Errorf("connection to Cohere API failed with status %d", res.StatusCode)
// after
return nil, fmt.Errorf("connection to Cohere API failed with status %d: %s", res.StatusCode, string(bodyBytes))

Defensive patterns

Strategy: try-catch

Type guard

func isOpaqueCohereStatusError(err error) bool {
    m := err.Error()
    return strings.HasPrefix(m, "connection to Cohere API failed with status") && !strings.HasSuffix(m, "") && !strings.Contains(m, ": ")
}

Try / catch

res, err := client.Rank(ctx, query, docs, cfg)
if err != nil && strings.HasPrefix(err.Error(), "connection to Cohere API failed with status") {
    // no provider message available; log, alert, and optionally retry 5xx
}

Prevention

Capture raw bodies on non-200 to compensate for missing provider messages
Distinguish 4xx (config problem) from 5xx (retryable) by parsing the status from the error
Keep the module updated to match current provider error schemas

When it happens

Trigger: Cohere or an intermediary returns a non-200 with a JSON body lacking the expected message field (empty body, error object with different shape), or a bare gateway 5xx with empty payload.

Common situations: Proxies returning empty 502/504 bodies; Cohere returning error shapes the client's cohereApiError struct does not map; network devices intercepting TLS.

Related errors

AI-assisted analysis of weaviate/weaviate@75aa4b6d11 (2026-09-04). Data as JSON: /api/errors/0e3173d3fba59a6b. Report an issue: GitHub.