From 5522ab985a2be9a096554e2be307cb8430d00a05 Mon Sep 17 00:00:00 2001
From: Susana Cardoso Ferreira <susana@coder.com>
Date: Fri, 23 Jan 2026 17:32:44 +0000
Subject: [PATCH 1/2] test: verify upstream errors are relayed to client in
 streaming chatcompletions

---
 intercept/chatcompletions/streaming_test.go | 110 ++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 intercept/chatcompletions/streaming_test.go

diff --git a/intercept/chatcompletions/streaming_test.go b/intercept/chatcompletions/streaming_test.go
new file mode 100644
index 0000000..fdd5bc9
--- /dev/null
+++ b/intercept/chatcompletions/streaming_test.go
@@ -0,0 +1,110 @@
+package chatcompletions
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strconv"
+	"testing"
+
+	"cdr.dev/slog/v3"
+	"cdr.dev/slog/v3/sloggers/sloghuman"
+	"github.com/coder/aibridge/config"
+	"github.com/coder/aibridge/internal/testutil"
+	"github.com/google/uuid"
+	"github.com/openai/openai-go/v3"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/otel"
+)
+
+// Test that when the upstream provider returns an error before streaming starts,
+// the error status code and body are correctly relayed to the client.
+func TestStreamingInterception_RelaysUpstreamErrorToClient(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name           string
+		statusCode     int
+		responseBody   string
+		expectedErrStr string
+		expectedBody   string
+	}{
+		{
+			name:           "bad request error",
+			statusCode:     http.StatusBadRequest,
+			responseBody:   `{"error":{"message":"Invalid request","type":"invalid_request_error","code":"invalid_request"}}`,
+			expectedErrStr: strconv.Itoa(http.StatusBadRequest),
+			expectedBody:   "invalid_request",
+		},
+		{
+			name:           "rate limit error",
+			statusCode:     http.StatusTooManyRequests,
+			responseBody:   `{"error":{"message":"Rate limit exceeded","type":"rate_limit_error","code":"rate_limit_exceeded"}}`,
+			expectedErrStr: strconv.Itoa(http.StatusTooManyRequests),
+			expectedBody:   "rate_limit",
+		},
+		{
+			name:           "internal server error",
+			statusCode:     http.StatusInternalServerError,
+			responseBody:   `{"error":{"message":"Internal server error","type":"server_error","code":"internal_error"}}`,
+			expectedErrStr: strconv.Itoa(http.StatusInternalServerError),
+			expectedBody:   "server_error",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Setup a mock server that returns an error immediately (before any streaming)
+			mockServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "application/json")
+				w.Header().Set("x-should-retry", "false")
+				w.WriteHeader(tc.statusCode)
+				_, _ = w.Write([]byte(tc.responseBody))
+			}))
+			t.Cleanup(mockServer.Close)
+
+			// Create interceptor with mock server URL
+			cfg := config.OpenAI{
+				BaseURL: mockServer.URL,
+				Key:     "test-key",
+			}
+
+			req := &ChatCompletionNewParamsWrapper{
+				ChatCompletionNewParams: openai.ChatCompletionNewParams{
+					Model: "gpt-4",
+					Messages: []openai.ChatCompletionMessageParamUnion{
+						openai.UserMessage("hello"),
+					},
+				},
+				Stream: true,
+			}
+
+			tracer := otel.Tracer("test")
+			interceptor := NewStreamingInterceptor(uuid.New(), req, cfg, tracer)
+
+			logger := slog.Make(sloghuman.Sink(io.Discard))
+			interceptor.Setup(logger, &testutil.MockRecorder{}, nil)
+
+			// Create test request
+			w := httptest.NewRecorder()
+			httpReq := httptest.NewRequest(http.MethodPost, "/chat/completions", nil)
+
+			// Process the request
+			err := interceptor.ProcessRequest(w, httpReq)
+
+			// Verify error was returned
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), tc.expectedErrStr)
+
+			// Verify status code was written to response
+			assert.Equal(t, tc.statusCode, w.Code, "expected status code to be relayed to client")
+
+			// Verify error body contains expected error info
+			body := w.Body.String()
+			assert.Contains(t, body, tc.expectedBody, "expected error type in response body")
+		})
+	}
+}

From 3372d8d70f5d8a9410da82a10ce0d33af6044414 Mon Sep 17 00:00:00 2001
From: Susana Cardoso Ferreira <susana@coder.com>
Date: Mon, 26 Jan 2026 10:47:07 +0000
Subject: [PATCH 2/2] chore: address comments

---
 intercept/chatcompletions/streaming_test.go | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/intercept/chatcompletions/streaming_test.go b/intercept/chatcompletions/streaming_test.go
index fdd5bc9..7d8d4d5 100644
--- a/intercept/chatcompletions/streaming_test.go
+++ b/intercept/chatcompletions/streaming_test.go
@@ -1,14 +1,13 @@
 package chatcompletions
 
 import (
-	"io"
 	"net/http"
 	"net/http/httptest"
 	"strconv"
 	"testing"
 
 	"cdr.dev/slog/v3"
-	"cdr.dev/slog/v3/sloggers/sloghuman"
+	"cdr.dev/slog/v3/sloggers/slogtest"
 	"github.com/coder/aibridge/config"
 	"github.com/coder/aibridge/internal/testutil"
 	"github.com/google/uuid"
@@ -85,7 +84,7 @@ func TestStreamingInterception_RelaysUpstreamErrorToClient(t *testing.T) {
 			tracer := otel.Tracer("test")
 			interceptor := NewStreamingInterceptor(uuid.New(), req, cfg, tracer)
 
-			logger := slog.Make(sloghuman.Sink(io.Discard))
+			logger := slogtest.Make(t, &slogtest.Options{IgnoreErrors: false}).Leveled(slog.LevelDebug)
 			interceptor.Setup(logger, &testutil.MockRecorder{}, nil)
 
 			// Create test request