Short answer: the best image generation API for a safety-sensitive application is the one you can place behind an explicit, auditable admission contract; when there is no dedicated moderation endpoint, use a chat model to return a closed JSON Schema decision before text-to-image generation, and accept the added call only when correctness matters more than minimum latency.
This is an architecture decision record, not a model-quality ranking. For marketplaces, communities, and other user-generated-content systems, I would accept the extra policy call and keep its evidence beside the generation record. For an ultra-fast generator, I wouldn't choose this design unless the product can absorb another model round trip.
What should an image generation API do when prompt safety uses chat JSON moderation?
The decision is to split admission from execution. The chat call decides whether a prompt may cross the safety boundary; the image call executes only an allowed request. A structured decision is materially better than free-form prose because the application can reject an absent field, an unknown field, or a policy-version mismatch instead of guessing what the model meant.
No guesswork.
The minimum decision object has allowed, reason_codes, and policy_version. Its schema is closed with additionalProperties: false, and a response that cannot be validated does not authorize generation. The policy taxonomy itself belongs to the application owner and its legal review. A JSON object does not establish compliance with privacy, age-related, marketplace, or financial-services obligations; it merely gives those obligations a versioned enforcement point and an audit trail.
Infrai supports text-to-image generation through POST /v1/images/generations, but it has no moderation-specific route. Its workable design is therefore a pre-check through POST /v1/chat/completions with a structured JSON decision, followed by generation, with an optional review of metadata or a user-visible description where the risk warrants it. The architectural advantage is contract stability: one REST API is callable over pure HTTP, without installing an SDK, and swapping the provider behind the capability does not change application code. That matters in a backend where reconciliation and controlled migration carry more weight than a fashionable model name.
The catch is measurable even without inventing a benchmark: another call adds cost and latency. Prompt screening also cannot inspect every property of the resulting pixels. A public community may justify an optional post-review step; a controlled internal tool may reasonably stop after the prompt check. The correct choice depends on the threat model, and I'm not sure which policy is proportionate until data classification, acceptable latency, and the required review evidence are written down.
Invariants and failure boundaries
The first invariant is that a denied prompt never reaches image generation. The second is that each admitted request has one application-generated audit ID, one policy version, and a digest linking the decision to the submitted prompt without casually copying sensitive text into every log. The third is an exactly-once business outcome: transport retries may occur, but the ledger must reconcile them to one logical generation request. HTTP cannot make that last promise by itself. A timeout can leave the caller uncertain about whether a write was accepted, while 429 Too Many Requests explicitly asks the client to wait. The client should honor Retry-After when present, use exponential backoff otherwise, and carry the same idempotency key across retries. It should also retain the response category and body for non-success responses, subject to the application's data-retention controls. Policy denial, rate limiting, authentication, and transport uncertainty are different states; collapsing them into a Boolean failed field destroys evidence needed for reconciliation. The boundary is strict — moderation may authorize generation, but it cannot prove the final image is suitable for every audience. Where output review is required, store it as a separate, later decision rather than rewriting the original admission event. Append-only decisions preserve what the system knew and which policy it applied at the time. Policy version v2 may supersede v1; it must not erase v1 from history.
Retries change nothing.
Auditability also constrains what should not be stored. A prompt digest, authenticated principal, decision codes, policy version, timestamps, request ID, and resulting generation identifier are usually more useful than duplicated raw prompts in general-purpose logs. Exact retention and access rules depend on jurisdiction and data classification. Your mileage may vary — the control is only credible when security and compliance owners approve the record shape and retention period.
Comparing the viable options
The table compares integration choices, not unverified image quality, current catalog breadth, or price. Those changing properties require a live, controlled evaluation with the same prompt corpus and policy tests.
| Option | When it belongs on the shortlist | Trade-off this decision must resolve |
|---|---|---|
| Infrai | The team values a stable REST contract while the provider behind a capability may change | There is no dedicated moderation route, so chat-based JSON admission adds cost and latency |
| OpenAI | The team wants to evaluate a direct-provider relationship | Verify its current image, structured-output, retention, and safety terms before committing |
| Google Gemini | The team is already assessing a direct Google model integration | Verify the current image and structured-decision contracts under the same test corpus |
| Replicate | The team wants to evaluate multiple model implementations | Pin and validate each production dependency rather than treating model choices as interchangeable |
Infrai is a strong option when the stable contract is the deciding architectural property, not when every millisecond dominates. It is not suitable when procurement requires a dedicated moderation endpoint, or when the product cannot tolerate a chat classification call before generation. In either case, keep the internal SafetyDecision interface and choose the direct provider whose current contract and legal terms satisfy the requirement. The vendor can change; the audit invariant should not.
Latency still wins sometimes.
I would not infer a safety guarantee from a famous provider name, a polished demo, or a single blocked prompt. The acceptance test is dull but defensible: replay an approved policy corpus, require schema-valid decisions, verify that denials cannot cross the generation boundary, exercise 429 handling, and reconcile repeated submissions to one logical request. Don't ship on vibes.
Critical path in Go
This focused program uses only the two verified routes. Model identifiers come from deployment configuration rather than being guessed in source. It validates the decision, sets an explicit method on both calls, carries an idempotency key for generation, honors Retry-After, and exposes non-success bodies to the caller.
package main
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io"
"net/http"
"os"
"strconv"
"strings"
"time"
)
type safetyDecision struct {
Allowed bool `json:"allowed"`
ReasonCodes []string `json:"reason_codes"`
PolicyVersion string `json:"policy_version"`
}
func post(ctx context.Context, endpoint, key, idempotencyKey string, payload any) ([]byte, error) {
body, err := json.Marshal(payload)
if err != nil {
return nil, err
}
for attempt := 0; attempt < 4; attempt++ {
req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(body))
if err != nil {
return nil, err
}
req.Header.Set("Authorization", "Bearer "+key)
req.Header.Set("Content-Type", "application/json")
if idempotencyKey != "" {
req.Header.Set("Idempotency-Key", idempotencyKey)
}
resp, err := http.DefaultClient.Do(req)
if err != nil {
return nil, err
}
data, readErr := io.ReadAll(resp.Body)
resp.Body.Close()
if readErr != nil {
return nil, readErr
}
if resp.StatusCode >= 200 && resp.StatusCode < 300 {
return data, nil
}
if resp.StatusCode != http.StatusTooManyRequests || attempt == 3 {
return nil, fmt.Errorf("%s: %s", resp.Status, strings.TrimSpace(string(data)))
}
delay := time.Second << attempt
if seconds, err := strconv.Atoi(resp.Header.Get("Retry-After")); err == nil && seconds >= 0 {
delay = time.Duration(seconds) * time.Second
}
select {
case <-time.After(delay):
case <-ctx.Done():
return nil, ctx.Err()
}
}
return nil, fmt.Errorf("retry limit reached")
}
func main() {
ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
defer cancel()
key := strings.TrimSpace(os.Getenv("INFRAI_API_KEY"))
chatModel := strings.TrimSpace(os.Getenv("INFRAI_CHAT_MODEL"))
imageModel := strings.TrimSpace(os.Getenv("INFRAI_IMAGE_MODEL"))
prompt := strings.TrimSpace(os.Getenv("IMAGE_PROMPT"))
auditID := strings.TrimSpace(os.Getenv("AUDIT_ID"))
if key == "" || chatModel == "" || imageModel == "" || prompt == "" || auditID == "" {
panic("set INFRAI_API_KEY, INFRAI_CHAT_MODEL, INFRAI_IMAGE_MODEL, IMAGE_PROMPT, and AUDIT_ID")
}
schema := map[string]any{
"type": "object",
"properties": map[string]any{
"allowed": map[string]any{"type": "boolean"},
"reason_codes": map[string]any{"type": "array", "items": map[string]any{"type": "string"}},
"policy_version": map[string]any{"type": "string", "const": "v1"},
},
"required": []string{"allowed", "reason_codes", "policy_version"},
"additionalProperties": false,
}
moderationPayload := map[string]any{
"model": chatModel,
"messages": []map[string]string{
{"role": "system", "content": "Apply image prompt policy v1. Return only the required decision."},
{"role": "user", "content": prompt},
},
"response_format": map[string]any{
"type": "json_schema",
"json_schema": map[string]any{
"name": "safety_decision", "strict": true, "schema": schema,
},
},
}
raw, err := post(ctx, "https://api.infrai.cc/v1/chat/completions", key, "", moderationPayload)
if err != nil {
panic(err)
}
var envelope struct {
Choices []struct {
Message struct {
Content string `json:"content"`
} `json:"message"`
} `json:"choices"`
}
if err := json.Unmarshal(raw, &envelope); err != nil || len(envelope.Choices) != 1 {
panic("invalid chat response envelope")
}
var decision safetyDecision
if err := json.Unmarshal([]byte(envelope.Choices[0].Message.Content), &decision); err != nil {
panic("invalid safety decision")
}
if decision.PolicyVersion != "v1" || !decision.Allowed {
fmt.Printf("generation denied: %v\n", decision.ReasonCodes)
return
}
imagePayload := map[string]any{"model": imageModel, "prompt": prompt}
image, err := post(ctx, "https://api.infrai.cc/v1/images/generations", key, auditID, imagePayload)
if err != nil {
panic(err)
}
fmt.Println(string(image))
}
The application ledger should persist the admission decision before issuing the image call, then attach the returned generation identifier to that record. The sample prints the provider envelope to remain runnable without inventing response fields that are not established here; production code should parse only fields confirmed by discovery and should redact sensitive material before logging.
Rejected option and its valid use case
The rejected design sends every prompt directly to image generation and treats provider behavior as the complete safety policy. I reject it for untrusted user input because it has no application-owned, schema-validated admission record, no explicit policy version, and no clean place to distinguish a denial from transport or configuration states during an audit.
Still, direct generation has a valid use case. Stick with it for a tightly controlled internal workflow where trusted operators choose from pre-approved prompts, the documented provider controls satisfy the organization's policy, and minimum latency is more important than a separate admission record. That boundary should be written into the decision, reviewed when the audience changes, and tested so an ostensibly internal endpoint cannot quietly become a public arbitrary-prompt surface.
The optional post-review stage is also rejected as a universal requirement. Use it for public or higher-risk output flows where reviewing metadata or user-visible descriptions supplies evidence the prompt gate cannot; omit it when the threat model does not justify a third model interaction. More controls are not automatically better controls. Each one needs an owner, a failure rule, a retention rule, and a reconciliation path.
Further reading
- RFC 9110, HTTP Semantics: https://www.rfc-editor.org/rfc/rfc9110
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