diff --git a/filter_openai.go b/filter_openai.go
index 15b4dca..2f08e3c 100644
--- a/filter_openai.go
+++ b/filter_openai.go
@@ -101,9 +101,7 @@ func (o OpenAIFilterer) Filter(m APMessage) (filterThisMessage bool, reason stri
 	chatCompletion, err := client.Chat.Completions.New(context.TODO(),
 		openai.ChatCompletionNewParams{
 			Messages: openai.F([]openai.ChatCompletionMessageParamUnion{
-				openai.SystemMessage(OpenAISystemPrompt),
-				openai.SystemMessage(o.UserPrompt),
-				openai.SystemMessage(OpenAIFinalInstructions),
+				openai.SystemMessage(OpenAISystemPrompt + o.UserPrompt + OpenAIFinalInstructions),
 				openai.UserMessage(ms),
 			}),
 			Model: openai.F(openAIModel),
diff --git a/filter_openai_test.go b/filter_openai_test.go
new file mode 100644
index 0000000..0cbdf80
--- /dev/null
+++ b/filter_openai_test.go
@@ -0,0 +1,235 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/mcuadros/go-defaults"
+	"github.com/openai/openai-go"
+	"github.com/openai/openai-go/option"
+)
+
+// TestOpenAIFiltererSendsSingleSystemMessage verifies that OpenAIFilterer.Filter
+// sends exactly one leading system message followed by a single user message.
+//
+// Regression test for https://github.com/tyzbit/acars-processor/issues/45:
+// Strict chat templates (e.g. Qwen3 served by llama.cpp --jinja) reject
+// requests with multiple consecutive system messages and return HTTP 400,
+// which (combined with the default FilterOnFailure=true) causes every
+// message to be silently dropped.
+func TestOpenAIFiltererSendsSingleSystemMessage(t *testing.T) {
+	var (
+		gotPath             string
+		gotMethod           string
+		gotMessages         []map[string]any
+		gotContentType      string
+		gotAuthorizationHdr string
+	)
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotPath = r.URL.Path
+		gotMethod = r.Method
+		gotContentType = r.Header.Get("Content-Type")
+		gotAuthorizationHdr = r.Header.Get("Authorization")
+
+		buf, _ := io.ReadAll(r.Body)
+		var body struct {
+			Messages []map[string]any `json:"messages"`
+			Model    string           `json:"model"`
+		}
+		if err := json.Unmarshal(buf, &body); err != nil {
+			t.Errorf("failed to decode request body: %v", err)
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+		gotMessages = body.Messages
+
+		// Reply with a valid chat.completions response so Filter() can parse it.
+		w.Header().Set("Content-Type", "application/json")
+		_ = json.NewEncoder(w).Encode(map[string]any{
+			"id":      "chatcmpl-test",
+			"object":  "chat.completion",
+			"created": 0,
+			"model":   body.Model,
+			"choices": []map[string]any{
+				{
+					"index": 0,
+					"message": map[string]any{
+						"role":    "assistant",
+						"content": `{"message_matches_criteria":"false","reasoning":"test"}`,
+					},
+					"finish_reason": "stop",
+				},
+			},
+		})
+	}))
+	defer srv.Close()
+
+	f := OpenAIFilterer{
+		FilterOnFailure: false,
+		APIKey:          "test-key",
+		Model:           "gpt-4o",
+		UserPrompt:      "USER-PROMPT-MARKER",
+		SystemPrompt:    "SYS-MARKER",
+		URL:             srv.URL + "/v1/",
+	}
+
+	filterThis, _, err := f.Filter(APMessage{
+		ACARSProcessorPrefix + "MessageText": "hello world",
+	})
+	if err != nil {
+		t.Fatalf("Filter returned error: %v", err)
+	}
+	// Mock returns message_matches_criteria="false" (no match) -> the filter
+	// should drop the message, i.e. filterThisMessage == true.
+	if !filterThis {
+		t.Fatalf("expected filterThis=true (model reported no match), got false")
+	}
+
+	if gotMethod != http.MethodPost {
+		t.Errorf("expected POST request, got %s", gotMethod)
+	}
+	if gotPath != "/v1/chat/completions" {
+		t.Errorf("expected path /v1/chat/completions, got %s", gotPath)
+	}
+	if !strings.HasPrefix(gotContentType, "application/json") {
+		t.Errorf("expected JSON content type, got %q", gotContentType)
+	}
+	if gotAuthorizationHdr != "Bearer test-key" {
+		t.Errorf("expected Bearer auth header, got %q", gotAuthorizationHdr)
+	}
+
+	// Core regression check: exactly one system message and one user message.
+	if len(gotMessages) != 2 {
+		t.Fatalf("expected exactly 2 messages (1 system + 1 user), got %d: %#v", len(gotMessages), gotMessages)
+	}
+	if role, _ := gotMessages[0]["role"].(string); role != "system" {
+		t.Errorf("expected first message role=system, got %q", role)
+	}
+	if role, _ := gotMessages[1]["role"].(string); role != "user" {
+		t.Errorf("expected second message role=user, got %q", role)
+	}
+
+	// The single system message must contain the framing prompt, the user
+	// prompt, and the closing instructions, in that order. The openai-go
+	// library serializes content as either a plain string or an array of
+	// {type,text} parts; we accept either form and concatenate any parts.
+	sysContent := extractMessageContent(t, gotMessages[0])
+	idxMarker := strings.Index(sysContent, "USER-PROMPT-MARKER")
+	idxSys := strings.Index(sysContent, "SYS-MARKER")
+	idxFinal := strings.Index(sysContent, "message_matches_criteria")
+	if idxMarker < 0 {
+		t.Errorf("user prompt not found in system message; got: %q", sysContent)
+	}
+	if idxSys < 0 {
+		t.Errorf("default system prompt not found in system message; got: %q", sysContent)
+	}
+	if idxFinal < 0 {
+		t.Errorf("final instructions not found in system message; got: %q", sysContent)
+	}
+	if !(idxSys < idxMarker && idxMarker < idxFinal) {
+		t.Errorf("expected order: framing < user-prompt < final; got sys=%d marker=%d final=%d in %q",
+			idxSys, idxMarker, idxFinal, sysContent)
+	}
+
+	// Ensure the user message contains the original message text, unchanged.
+	userContent := extractMessageContent(t, gotMessages[1])
+	if userContent != "hello world" {
+		t.Errorf("expected user message content %q, got %q", "hello world", userContent)
+	}
+}
+
+// TestOpenAIFiltererFilterOnFailureDefaultsTrue documents the existing default
+// behavior called out in the issue: when the backend returns an error,
+// Filter() returns FilterOnFailure, which defaults to true, causing the
+// message to be dropped. The fix in this branch only changes the request
+// shape, not the failure-handling policy.
+func TestOpenAIFiltererFilterOnFailureDefaultsTrue(t *testing.T) {
+	// Struct-tag defaults are applied at config-load time via the
+	// mcuadros/go-defaults library. Verify the loaded default matches the
+	// tag, so a user who simply instantiates OpenAIFilterer{} at runtime
+	// (without loading config) gets the documented default-on-failure
+	// behavior.
+	f := OpenAIFilterer{}
+	defaults.SetDefaults(&f)
+	if !f.FilterOnFailure {
+		t.Fatalf("expected FilterOnFailure default to be true (per struct tag); got false")
+	}
+}
+
+// TestOpenAIFiltererDropsMessageOnBackendError captures the silent-drop
+// failure mode described in the issue: a backend error combined with
+// FilterOnFailure=true causes the message to be filtered out. The
+// implementation does surface the error to the caller (so the step
+// framework can log it), but the message is dropped from the pipeline
+// because FilterOnFailure=true. This test pins that behavior so we
+// notice if it ever changes unintentionally.
+func TestOpenAIFiltererDropsMessageOnBackendError(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Simulate the exact failure mode in the issue: a strict-template
+		// rejection (400 "System message must be at the beginning").
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprint(w, `{"error":{"code":400,"message":"System message must be at the beginning.","type":"invalid_request_error"}}`)
+	}))
+	defer srv.Close()
+
+	f := OpenAIFilterer{
+		FilterOnFailure: true,
+		APIKey:          "k",
+		Model:           "gpt-4o",
+		UserPrompt:      "x",
+		URL:             srv.URL + "/v1/",
+	}
+	filterThis, _, err := f.Filter(APMessage{ACARSProcessorPrefix + "MessageText": "hi"})
+	if err == nil {
+		t.Fatalf("expected Filter to surface the backend error to the caller, got nil")
+	}
+	if !filterThis {
+		t.Fatalf("expected message to be filtered out on backend error with FilterOnFailure=true, but it passed through")
+	}
+}
+
+// Sanity check: ensure the openai-go types we depend on still expose the
+// constructors we use. This catches accidental import or version drift.
+func TestOpenAIFiltererOpenAIHelpersAvailable(t *testing.T) {
+	_ = openai.SystemMessage("x")
+	_ = openai.UserMessage("y")
+	_ = openai.NewClient(option.WithAPIKey("k"))
+	_ = context.TODO()
+}
+
+// extractMessageContent returns the textual content of a message as decoded
+// from the JSON body. openai-go may serialize content either as a plain
+// string or as an array of typed parts (e.g. {"type":"text","text":"..."}).
+func extractMessageContent(t *testing.T, msg map[string]any) string {
+	t.Helper()
+	raw, ok := msg["content"]
+	if !ok {
+		return ""
+	}
+	switch v := raw.(type) {
+	case string:
+		return v
+	case []any:
+		var sb strings.Builder
+		for _, part := range v {
+			m, ok := part.(map[string]any)
+			if !ok {
+				continue
+			}
+			if text, ok := m["text"].(string); ok {
+				sb.WriteString(text)
+			}
+		}
+		return sb.String()
+	default:
+		return ""
+	}
+}