Expose HTTP transient retry control and preserve shared capacity

internal/adapter/http/handler.go

@@ -76,6 +76,10 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadRequest, "invalid_request", "prompt_id is required")
 		return
 	}
+	if req.TransientRetries != nil && *req.TransientRetries < 0 {
+		writeError(w, http.StatusBadRequest, "invalid_request", "transient_retries must be greater than or equal to 0")
+		return
+	}
 	var mappedInputs map[string]promptkit.ArtifactRef
 	if len(req.Inputs) > 0 {
 		mappedInputs = make(map[string]promptkit.ArtifactRef, len(req.Inputs))
@@ -94,13 +98,14 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	res, err := h.runner.Run(r.Context(), promptkit.RunRequest{
-		PromptID:      req.PromptID,
-		PromptVersion: req.PromptVersion,
-		ProfileID:     req.ProfileID,
-		SessionID:     req.SessionID,
-		Inputs:        mappedInputs,
-		Vars:          req.Vars,
-		Execution:     model,
+		PromptID:         req.PromptID,
+		PromptVersion:    req.PromptVersion,
+		ProfileID:        req.ProfileID,
+		SessionID:        req.SessionID,
+		Inputs:           mappedInputs,
+		Vars:             req.Vars,
+		Execution:        model,
+		TransientRetries: req.TransientRetries,
 	})
 	if err != nil {
 		status, code, message := mapRunError(err)
@@ -224,7 +229,7 @@ func mapRunError(err error) (int, string, string) {
 		return http.StatusBadRequest, "prompt_render_failed", "failed to render prompt"
 	case errors.Is(err, promptkit.ErrCapacityExceeded):
 		return http.StatusServiceUnavailable, "capacity_exceeded", "model backend capacity is exhausted"
-	case errors.Is(err, promptkit.ErrLLMGenerate):
+	case errors.Is(err, promptkit.ErrLLMGenerate), errors.Is(err, promptkit.ErrTransport), errors.Is(err, promptkit.ErrMalformedResponse), errors.Is(err, promptkit.ErrRetriesExhausted):
 		return http.StatusBadGateway, "llm_failed", "model generation request failed"
 	case errors.Is(err, promptkit.ErrValidation):
 		return http.StatusInternalServerError, "validation_runtime_failed", "validation runtime failed"