diff --git a/onnxruntime/contrib_ops/cpu/transformers/subgraph_t5_decoder.cc b/onnxruntime/contrib_ops/cpu/transformers/subgraph_t5_decoder.cc
index 8db69150919d5..997beb198f450 100644
--- a/onnxruntime/contrib_ops/cpu/transformers/subgraph_t5_decoder.cc
+++ b/onnxruntime/contrib_ops/cpu/transformers/subgraph_t5_decoder.cc
@@ -20,8 +20,9 @@ namespace transformers {
 
    Inputs:
       input_ids: int32 (B, 1)
+      encoder_input_ids: int32 (B, encode_sequence_length) (optional)
       encoder_attention_mask: int32 (B, encode_sequence_length)
-      encoder_hidden_states: (B, encode_sequence_length, encoder_hidden_size)
+      encoder_hidden_states: (B, encode_sequence_length, encoder_hidden_size) (optional)
 
       past_key_self_0: (B, num_heads, past_decode_sequence_length, head_size)
       past_value_self_0: (B, num_heads, past_decode_sequence_length, head_size)
@@ -53,9 +54,6 @@ Status T5DecoderSubgraph::Validate(const std::vector<const NodeArg*>& subgraph_i
   bool has_hidden_state = subgraph_inputs[2 + has_encoder_input_ids]->Name() == "encoder_hidden_states";
   SetPastInputIndex(has_hidden_state, has_encoder_input_ids);
 
-  ORT_RETURN_IF(first_past_input_index_ != 2 && first_past_input_index_ != 3 && first_past_input_index_ != 4,
-                "kFirstPastInputIndex currently only supports 2, 3 or 4");
-
   if (!past_present_share_buffer_) {
     ORT_RETURN_IF(has_decoder_masked_attention_, "decoder_masked_attention shall use with past_present_share_buffer");
     ORT_RETURN_IF(num_subgraph_inputs < 4 + first_past_input_index_ ||
@@ -78,11 +76,6 @@ Status T5DecoderSubgraph::Validate(const std::vector<const NodeArg*>& subgraph_i
                 "decoder subgraph input 0 shall be named as input_ids, got: ", subgraph_inputs[0]->Name());
   const int enc_attn_mask_index = 1 + has_encoder_input_ids_;
   const int enc_hidden_state_index = enc_attn_mask_index + 1;
-  if (has_encoder_input_ids_) {
-    ORT_RETURN_IF(subgraph_inputs[1]->Name() != "encoder_input_ids",
-                  "decoder subgraph input 1 shall be named as encoder_input_ids, got: ",
-                  subgraph_inputs[1]->Name());
-  }
   ORT_RETURN_IF(subgraph_inputs[enc_attn_mask_index]->Name() != "encoder_attention_mask",
                 "decoder subgraph input ", std::to_string(enc_attn_mask_index),
                 " shall be named as encoder_attention_mask, got: ",
@@ -268,6 +261,8 @@ Status T5DecoderSubgraph::CreateInitialFeeds(
   // When first_past_input_index_ == 3, the encoder_hidden_states and past states are copied from the second output
   // of encoder.
   // When first_past_input_index_ == 2, the past states are copied from the second output of encoder.
+  // TODO - probably more robust to introduce a encoder_out/decoder_in mapping instead of relying on positions.
+  // What happens if encoder_hidden_states is present in the encoder_fetches but not in the decoder_feeds?
   for (size_t j = static_cast<size_t>(2) - has_hidden_state_; j < encoder_fetches.size(); j++) {
     if (j == 1) {
       ORT_RETURN_IF(has_hidden_state_ == false, "Invalid hidden_states expension: has_hidden_state_ == false");