Classify LLM context length errors

internal/worker/worker.go

@@ -207,6 +207,8 @@ func classifyLLMError(err error) string {
 		return "timeout"
 	case strings.Contains(s, "connection refused") || strings.Contains(s, "connection reset") || strings.Contains(s, "no route to host") || strings.Contains(s, "llm http 5"):
 		return "model_unavailable"
+	case strings.Contains(s, "maximum context length") || strings.Contains(s, "context length") || strings.Contains(s, "input_tokens"):
+		return "context_length"
 	case strings.Contains(s, "llm http 4") || strings.Contains(s, "messages are required"):
 		return "bad_input"
 	case strings.Contains(s, "llm decode") || strings.Contains(s, "empty choices"):

internal/worker/worker_test.go

@@ -0,0 +1,29 @@
+package worker
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestClassifyLLMError(t *testing.T) {
+	tests := []struct {
+		name string
+		err  error
+		want string
+	}{
+		{name: "timeout", err: errors.New("context deadline exceeded"), want: "timeout"},
+		{name: "unavailable", err: errors.New("llm HTTP 500: internal server error"), want: "model_unavailable"},
+		{name: "context length", err: errors.New("This model's maximum context length is 16384 tokens. input_tokens=16001"), want: "context_length"},
+		{name: "bad input", err: errors.New("llm HTTP 400: messages are required"), want: "bad_input"},
+		{name: "bad response", err: errors.New("llm decode: invalid character '<'"), want: "bad_response"},
+		{name: "unknown", err: errors.New("strange failure"), want: "unknown"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := classifyLLMError(tt.err); got != tt.want {
+				t.Fatalf("classifyLLMError() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}