What causes "failed to create stream request: %w" in micro/go-micro?

Trim and validate opts.Model and opts.BaseURL (no spaces, valid URL) before calling Stream.

failed to create stream request: %w

Error message

failed to create stream request: %w

What it means

Stream failed at http.NewRequestWithContext while building the streaming POST to /v1beta/models/<model>:streamGenerateContent?alt=sse. This almost always means the constructed URL was invalid (bad model name characters, malformed BaseURL) or the context was already canceled. The wrapped error states which.

Source

Thrown at ai/gemini/gemini.go:188

	if req.SystemPrompt != "" {
		apiReq["system_instruction"] = map[string]any{
			"parts": []map[string]any{{"text": req.SystemPrompt}},
		}
	}
	if p.opts.MaxTokens > 0 {
		apiReq["generationConfig"] = map[string]any{"maxOutputTokens": p.opts.MaxTokens}
	}

	reqBody, err := json.Marshal(apiReq)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal stream request: %w", err)
	}

	apiURL := strings.TrimRight(p.opts.BaseURL, "/") +
		"/v1beta/models/" + p.opts.Model + ":streamGenerateContent?alt=sse"
	httpReq, err := http.NewRequestWithContext(ctx, http.MethodPost, apiURL, bytes.NewReader(reqBody))
	if err != nil {
		return nil, fmt.Errorf("failed to create stream request: %w", err)
	}
	httpReq.Header.Set("Content-Type", "application/json")
	httpReq.Header.Set("Accept", "text/event-stream")
	httpReq.Header.Set("x-goog-api-key", p.opts.APIKey)

	httpResp, err := http.DefaultClient.Do(httpReq)
	if err != nil {
		return nil, fmt.Errorf("stream API request failed: %w", err)
	}
	if httpResp.StatusCode != http.StatusOK {
		defer httpResp.Body.Close()
		respBody, _ := io.ReadAll(httpResp.Body)
		return nil, ai.NewHTTPError(httpResp, respBody)
	}
	return &streamReader{body: httpResp.Body, scanner: bufio.NewScanner(httpResp.Body)}, nil
}

type streamReader struct {

View on GitHub (pinned to 24529f1404)

Solutions

Trim and validate opts.Model and opts.BaseURL (no spaces, valid URL) before calling Stream.
Check the wrapped %w error: if it mentions 'context canceled', fix the upstream context lifecycle.
Print the composed URL and validate it parses with net/url.Parse.
Verify BaseURL lacks a trailing path typo or scheme issue (must include http:// or https://).

Example fix

// before
p.opts.Model = os.Getenv("GEMINI_MODEL")
// after
model := strings.TrimSpace(os.Getenv("GEMINI_MODEL"))
if model == "" || strings.ContainsAny(model, " /?") {
    return nil, fmt.Errorf("invalid model name: %q", model)
}
p.opts.Model = model

Defensive patterns

Strategy: validation

Validate before calling

u, err := url.Parse(strings.TrimSpace(baseURL))
if err != nil || u.Scheme == "" || u.Host == "" {
    return fmt.Errorf("invalid BaseURL: %q", baseURL)
}
model := strings.TrimSpace(modelName)
if model == "" || strings.ContainsAny(model, " ?#/") {
    return fmt.Errorf("invalid model name: %q", model)
}

Type guard

func validGeminiOpts(baseURL, model string) bool {
    u, err := url.Parse(baseURL)
    return err == nil && (u.Scheme == "http" || u.Scheme == "https") && u.Host != "" &&
        strings.TrimSpace(model) == model && model != ""
}

Try / catch

stream, err := provider.Stream(ctx, req)
if err != nil {
    if strings.Contains(err.Error(), "failed to create stream request") && ctx.Err() != nil {
        return fmt.Errorf("context canceled before streaming: %w", ctx.Err())
    }
    return err
}

Prevention

Trim env-derived model names and BaseURLs at config load time
Validate provider configuration once at startup, not per request
Avoid reusing contexts that may already be canceled

When it happens

Trigger: Calling Stream with an opts.Model containing characters invalid in a URL path, a malformed opts.BaseURL (e.g. with spaces or control chars), or a ctx that was canceled before the call.

Common situations: Model name pasted with whitespace/newline; BaseURL set to a proxy URL with stray characters; passing an already-expired/canceled context from an upstream timeout.

Related errors

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/90aa47a7fbb0ac9d. Report an issue: GitHub.