diff --git a/gpttype_adapter.cpp b/gpttype_adapter.cpp
index a859e9d55..e1ad0d75f 100644
--- a/gpttype_adapter.cpp
+++ b/gpttype_adapter.cpp
@@ -570,6 +570,33 @@ static void load_grammar(const std::string & gammarstr)
     }
 }
 
+//given an old GGUF context and a new context that has some middle portion removed,
+//find and remove the middle portion from the old context from the KV. Does not fast forward after this destructive action
+void PurgeMissingTokens(std::vector<int> &current_context_tokens, std::vector<int> &new_context_tokens)
+{
+    //scan from start old and new ctx, until first mismatch found, save as p0
+    //check remaining old and new ctx for longest common subseq, which needs to be at 256 tokens
+    //test: longest common subseq (LCQ) MUST start within 0 tokens from end of memory, otherwise purge fails
+    //if passed, save beginning of LCQ from old ctx as p1
+    //remove all tokens from old ctx between p0 and p1, updating both arrays and kv, then continue as normal
+
+    // int trimstart = 0;
+
+    // const int n_keep = 0;
+    // const int n_left = n_past - n_keep - 1;
+    // const int n_discard = n_left/2;
+
+    // printf("context full, swapping: n_past = %d, n_left = %d, n_ctx = %d, n_keep = %d, n_discard = %d\n",
+    //     n_past, n_left, nctx, n_keep, n_discard);
+
+    // llama_kv_cache_seq_rm   (llama_ctx_v4, 0, n_keep + 1            , n_keep + n_discard + 1);
+    // llama_kv_cache_seq_shift(llama_ctx_v4, 0, n_keep + 1 + n_discard, n_past, -n_discard);
+    // n_past -= n_discard;
+
+    // printf("after swap: n_past = %d\n", n_past);
+
+}
+
 ModelLoadResult gpttype_load_model(const load_model_inputs inputs, FileFormat in_file_format, FileFormatExtraMeta file_format_meta)
 {
     ggml_time_init();
@@ -1371,6 +1398,8 @@ generation_outputs gpttype_generate(const generation_inputs inputs, generation_o
     std::fill(last_n_tokens.begin(), last_n_tokens.end(), 0);
     n_past = 0;
 
+    PurgeMissingTokens(current_context_tokens, embd_inp);
+
     if (file_format == FileFormat::RWKV_1 || file_format==FileFormat::RWKV_2)
     {
         ContextFastForward(current_context_tokens, embd_inp, n_past, last_n_tokens, nctx, smartcontext, false, true);