add support for flux2 klein 4b

conditioner.hpp

@@ -1614,9 +1614,9 @@ struct LLMEmbedder : public Conditioner {
                 bool enable_vision                             = false)
         : version(version) {
         LLM::LLMArch arch = LLM::LLMArch::QWEN2_5_VL;
-        if (sd_version_is_flux2(version)) {
+        if (version == VERSION_FLUX2) {
             arch = LLM::LLMArch::MISTRAL_SMALL_3_2;
-        } else if (sd_version_is_z_image(version) || version == VERSION_OVIS_IMAGE) {
+        } else if (sd_version_is_z_image(version) || version == VERSION_OVIS_IMAGE || version == VERSION_FLUX2_KLEIN) {
             arch = LLM::LLMArch::QWEN3;
         }
         if (arch == LLM::LLMArch::MISTRAL_SMALL_3_2) {
@@ -1771,7 +1771,7 @@ struct LLMEmbedder : public Conditioner {
             prompt_attn_range.second = static_cast<int>(prompt.size());
 
             prompt += "<|im_end|>\n<|im_start|>assistant\n";
-        } else if (sd_version_is_flux2(version)) {
+        } else if (version == VERSION_FLUX2) {
             prompt_template_encode_start_idx = 0;
             out_layers                       = {10, 20, 30};
 
@@ -1793,17 +1793,17 @@ struct LLMEmbedder : public Conditioner {
             prompt_attn_range.second = static_cast<int>(prompt.size());
 
             prompt += "<|im_end|>\n<|im_start|>assistant\n";
-        } else if (sd_version_is_flux2(version)) {
+        } else if (version == VERSION_FLUX2_KLEIN) {
             prompt_template_encode_start_idx = 0;
-            out_layers                       = {10, 20, 30};
+            out_layers                       = {9, 18, 27};
 
-            prompt = "[SYSTEM_PROMPT]You are an AI that reasons about image descriptions. You give structured responses focusing on object relationships, object\nattribution and actions without speculation.[/SYSTEM_PROMPT][INST]";
+            prompt = "<|im_start|>user\n";
 
             prompt_attn_range.first = static_cast<int>(prompt.size());
             prompt += conditioner_params.text;
             prompt_attn_range.second = static_cast<int>(prompt.size());
 
-            prompt += "[/INST]";
+            prompt += "<|im_end|>\n<|im_start|>assistant\n<think>\n\n</think>\n\n";
         } else if (version == VERSION_OVIS_IMAGE) {
             prompt_template_encode_start_idx = 28;
             max_length                       = prompt_template_encode_start_idx + 256;

flux.hpp

@@ -1291,10 +1291,16 @@ namespace Flux {
                 flux_params.context_in_dim    = 2048;
                 flux_params.vec_in_dim        = 0;
             } else if (sd_version_is_flux2(version)) {
-                flux_params.context_in_dim   = 15360;
+                if (version == VERSION_FLUX2_KLEIN) {
+                    flux_params.context_in_dim   = 7680;
+                    flux_params.hidden_size      = 3072;
+                    flux_params.num_heads        = 24;
+                } else {
+                    flux_params.context_in_dim   = 15360;
+                    flux_params.hidden_size      = 6144;
+                    flux_params.num_heads        = 48;
+                }
                 flux_params.in_channels      = 128;
-                flux_params.hidden_size      = 6144;
-                flux_params.num_heads        = 48;
                 flux_params.patch_size       = 1;
                 flux_params.out_channels     = 128;
                 flux_params.mlp_ratio        = 3.f;

model.cpp

@@ -1034,6 +1034,8 @@ SDVersion ModelLoader::get_sd_version() {
 
     bool is_xl                       = false;
     bool is_flux                     = false;
+    bool is_flux2                    = false;
+    bool has_single_block_47         = false;
     bool is_wan                      = false;
     int64_t patch_embedding_channels = 0;
     bool has_img_emb                 = false;
@@ -1055,7 +1057,10 @@ SDVersion ModelLoader::get_sd_version() {
                 return VERSION_QWEN_IMAGE;
             }
             if (tensor_storage.name.find("model.diffusion_model.double_stream_modulation_img.lin.weight") != std::string::npos) {
-                return VERSION_FLUX2;
+                is_flux2 = true;
+            }
+            if (tensor_storage.name.find("single_blocks.47.linear1.weight") != std::string::npos) {
+                has_single_block_47 = true;
             }
             if (tensor_storage.name.find("model.diffusion_model.double_blocks.0.img_mlp.gate_proj.weight") != std::string::npos) {
                 return VERSION_OVIS_IMAGE;
@@ -1138,7 +1143,7 @@ SDVersion ModelLoader::get_sd_version() {
         return VERSION_SDXL;
     }
 
-    if (is_flux) {
+    if (is_flux && !is_flux2) {
         if (input_block_weight.ne[0] == 384) {
             return VERSION_FLUX_FILL;
         }
@@ -1151,6 +1156,13 @@ SDVersion ModelLoader::get_sd_version() {
         return VERSION_FLUX;
     }
 
+    if (is_flux2) {
+        if (has_single_block_47) {
+            return VERSION_FLUX2;
+        }
+        return VERSION_FLUX2_KLEIN;
+    }
+
     if (token_embedding_weight.ne[0] == 768) {
         if (is_inpaint) {
             return VERSION_SD1_INPAINT;

model.h

@@ -45,6 +45,7 @@ enum SDVersion {
     VERSION_WAN2_2_TI2V,
     VERSION_QWEN_IMAGE,
     VERSION_FLUX2,
+    VERSION_FLUX2_KLEIN,
     VERSION_Z_IMAGE,
     VERSION_OVIS_IMAGE,
     VERSION_COUNT,
@@ -100,7 +101,7 @@ static inline bool sd_version_is_flux(SDVersion version) {
 }
 
 static inline bool sd_version_is_flux2(SDVersion version) {
-    if (version == VERSION_FLUX2) {
+    if (version == VERSION_FLUX2 || version == VERSION_FLUX2_KLEIN) {
         return true;
     }
     return false;

stable-diffusion.cpp

@@ -48,6 +48,7 @@ const char* model_version_to_str[] = {
     "Wan 2.2 TI2V",
     "Qwen Image",
     "Flux.2",
+    "Flux.2 klein"
     "Z-Image",
     "Ovis Image",
 };