ggml-webgpu: add Q1_0 support (#22374)

* add fast matmul matvec q1_0 kernel

* ggml-webgpu: drop redundant zero-fills in Q1_0 shmem init

common/fit.cpp

@@ -856,7 +856,7 @@ void common_memory_breakdown_print(const struct llama_context * ctx) {
         ggml_backend_dev_memory(dev, &free, &total);
 
         const size_t self = mb.model + mb.context + mb.compute;
-        const size_t unaccounted = total - self - free;
+        const int64_t unaccounted = static_cast<int64_t>(total) - static_cast<int64_t>(free) - static_cast<int64_t>(self);
 
         table_data.push_back({
             template_gpu,
@@ -867,7 +867,7 @@ void common_memory_breakdown_print(const struct llama_context * ctx) {
             std::to_string(mb.model / MiB),
             std::to_string(mb.context / MiB),
             std::to_string(mb.compute / MiB),
-            std::to_string(unaccounted / MiB)});
+            std::to_string(unaccounted / static_cast<int64_t>(MiB))});
     }
 
     // print memory breakdown for host:

ggml/src/ggml-rpc/ggml-rpc.cpp

@@ -1101,7 +1101,7 @@ bool rpc_server::set_tensor(const std::vector<uint8_t> & input) {
         fs::path cache_file = fs::path(cache_dir) / hash_str;
         std::ofstream ofs(cache_file, std::ios::binary);
         ofs.write((const char *)data, size);
-        GGML_LOG_INFO("[%s] saved to '%s'\n", __func__, cache_file.c_str());
+        GGML_LOG_INFO("[%s] saved to '%s'\n", __func__, cache_file.string().c_str());
     }
     ggml_backend_tensor_set(tensor, data, offset, size);
     return true;

ggml/src/ggml-webgpu/ggml-webgpu-shader-lib.hpp

@@ -1287,6 +1287,7 @@ class ggml_webgpu_shader_lib {
                     std::transform(type_upper.begin(), type_upper.end(), type_upper.begin(), ::toupper);
 
                     switch (key.src_type) {
+                        case GGML_TYPE_Q1_0:
                         case GGML_TYPE_Q4_0:
                         case GGML_TYPE_Q5_0:
                         case GGML_TYPE_Q8_0:
@@ -1323,7 +1324,9 @@ class ggml_webgpu_shader_lib {
 
                     defines.push_back("DST_TYPE=f32");
 
-                    if ((key.src_type >= GGML_TYPE_Q4_0 && key.src_type <= GGML_TYPE_Q8_1) ||
+                    if (key.src_type == GGML_TYPE_Q1_0) {
+                        defines.push_back("BLOCK_SIZE=128u");
+                    } else if ((key.src_type >= GGML_TYPE_Q4_0 && key.src_type <= GGML_TYPE_Q8_1) ||
                         key.src_type == GGML_TYPE_IQ4_NL) {
                         defines.push_back("BLOCK_SIZE=32u");
                     } else if (key.src_type >= GGML_TYPE_Q2_K) {
@@ -1615,6 +1618,24 @@ class ggml_webgpu_shader_lib {
                     defines.push_back("MUL_ACC_" + type_upper);
                     defines.push_back("U32_DEQUANT_HELPERS");
                     defines.push_back("SRC0_INNER_TYPE=u32");
+                    switch (context.src0->type) {
+                        case GGML_TYPE_IQ1_S:
+                        case GGML_TYPE_IQ1_M:
+                        case GGML_TYPE_IQ2_S:
+                        case GGML_TYPE_IQ3_S:
+                        case GGML_TYPE_IQ4_NL:
+                        case GGML_TYPE_IQ4_XS:
+                            defines.push_back(type_upper + "_GRID");
+                            break;
+                        case GGML_TYPE_IQ2_XXS:
+                        case GGML_TYPE_IQ2_XS:
+                        case GGML_TYPE_IQ3_XXS:
+                            defines.push_back(type_upper + "_GRID");
+                            defines.push_back(type_upper + "_TABLES");
+                            break;
+                        default:
+                            break;
+                    }
                     break;
                 }
         }
@@ -1639,7 +1660,9 @@ class ggml_webgpu_shader_lib {
         uint32_t wg_size        = WEBGPU_MUL_MAT_VEC_WG_SIZE;
         uint32_t outputs_per_wg = WEBGPU_MUL_MAT_VEC_FLOAT_OUTPUTS_PER_WG;
 
-        if (key.src0_type >= GGML_TYPE_Q2_K) {
+        if (key.src0_type == GGML_TYPE_Q1_0) {
+            outputs_per_wg = WEBGPU_MUL_MAT_VEC_LEGACY_Q_OUTPUTS_PER_WG;
+        } else if (key.src0_type >= GGML_TYPE_Q2_K) {
             outputs_per_wg = WEBGPU_MUL_MAT_VEC_K_Q_OUTPUTS_PER_WG;
         } else if (key.src0_type >= GGML_TYPE_Q4_0) {
             outputs_per_wg = WEBGPU_MUL_MAT_VEC_LEGACY_Q_OUTPUTS_PER_WG;

ggml/src/ggml-webgpu/ggml-webgpu.cpp

@@ -1389,8 +1389,20 @@ static webgpu_encoded_op ggml_webgpu_mul_mat(webgpu_context & ctx,
                 case GGML_TYPE_Q5_K:
                 case GGML_TYPE_Q3_K:
                 case GGML_TYPE_Q2_K:
+                case GGML_TYPE_Q1_0:
                     use_fast = true;
                     break;
+                case GGML_TYPE_IQ1_S:
+                case GGML_TYPE_IQ1_M:
+                case GGML_TYPE_IQ2_XXS:
+                case GGML_TYPE_IQ2_XS:
+                case GGML_TYPE_IQ2_S:
+                case GGML_TYPE_IQ3_XXS:
+                case GGML_TYPE_IQ3_S:
+                case GGML_TYPE_IQ4_NL:
+                case GGML_TYPE_IQ4_XS:
+                    use_fast = is_vec;
+                    break;
                 default:
                     break;
             }
@@ -3725,6 +3737,7 @@ static bool ggml_backend_webgpu_device_supports_buft(ggml_backend_dev_t dev, ggm
 
 static bool ggml_webgpu_supported_qtype(ggml_type type) {
     switch (type) {
+        case GGML_TYPE_Q1_0:
         case GGML_TYPE_Q4_0:
         case GGML_TYPE_Q4_1:
         case GGML_TYPE_Q5_0:
@@ -3819,6 +3832,7 @@ static bool ggml_backend_webgpu_device_supports_op(ggml_backend_dev_t dev, const
                         switch (src0->type) {
                             case GGML_TYPE_F32:
                             case GGML_TYPE_F16:
+                            case GGML_TYPE_Q1_0:
                             case GGML_TYPE_Q4_0:
                             case GGML_TYPE_Q4_1:
                             case GGML_TYPE_Q5_0:
@@ -3857,6 +3871,7 @@ static bool ggml_backend_webgpu_device_supports_op(ggml_backend_dev_t dev, const
                     switch (src0->type) {
                         case GGML_TYPE_F32:
                         case GGML_TYPE_F16:
+                        case GGML_TYPE_Q1_0:
                         case GGML_TYPE_Q4_0:
                         case GGML_TYPE_Q4_1:
                         case GGML_TYPE_Q5_0:

ggml/src/ggml-webgpu/wgsl-shaders/get_rows.wgsl

@@ -27,6 +27,24 @@ fn copy_elements(src_base: u32, dst_base: u32, offset: u32) {
 }
 #endif
 
+#ifdef Q1_0
+fn copy_elements(src_base: u32, dst_base: u32, offset: u32) {
+    let block_byte_base = (src_base + offset) * 18;
+    let d = load_f16_as_f32_at_src(block_byte_base);
+    for (var j: u32 = 0u; j < 4u; j++) {
+        let q_packed = load_u32_at_src(block_byte_base + 2u + j * 4u);
+        let dst_base128 = dst_base + offset * 128u + j * 32u;
+        for (var k: u32 = 0; k < 4u; k++) {
+            let q_byte = get_byte(q_packed, k);
+            for (var bit: u32 = 0; bit < 8u; bit++) {
+                let w = select(-d, d, ((q_byte >> bit) & 1u) != 0u);
+                dst[dst_base128 + k * 8u + bit] = w;
+            }
+        }
+    }
+}
+#endif
+
 #ifdef Q4_0
 fn copy_elements(src_base: u32, dst_base: u32, offset: u32) {
     let block_byte_base = (src_base + offset) * 18; // Block stride: 18 bytes

ggml/src/ggml-webgpu/wgsl-shaders/mul_mat_decls.tmpl

@@ -61,6 +61,39 @@ fn init_shmem_src1(thread_id: u32, batch_offset: u32, offset_n: u32, k_outer: u3
 #endif // INIT_SRC1_SHMEM_FLOAT
 #endif
 
+#ifdef INIT_SRC0_SHMEM_Q1_0
+const BLOCK_SIZE = 128u;
+const BLOCK_SIZE_BYTES = 18u;
+const NQ = 8u; // 8 weights (1 byte of qs) per thread per iteration
+
+fn init_shmem_src0(thread_id: u32, batch_offset: u32, offset_m: u32, k_outer: u32) {
+    for (var i = thread_id * NQ; i < TILE_SRC0_SHMEM; i += TOTAL_WORKGROUP_SIZE * NQ) {
+        let tile_m = i / TILE_K;
+        let tile_k_start = i % TILE_K;
+        let global_m = offset_m + tile_m;
+        let global_k_start = k_outer + tile_k_start;
+
+        if (global_m >= params.m) {
+            break;
+        }
+
+        let block_k = global_k_start / BLOCK_SIZE;
+        let byte_in_block = (global_k_start % BLOCK_SIZE) / 8u;
+        let src0_idx = batch_offset + global_m * params.stride_01 + block_k;
+        let block_byte_base = src0_idx * BLOCK_SIZE_BYTES;
+        let d = load_f16_at_src0(block_byte_base);
+        let q_byte = load_u32_at_src0(block_byte_base + 2u + byte_in_block) & 0xFFu;
+
+        for (var bit = 0u; bit < NQ; bit++) {
+            let global_k = global_k_start + bit;
+            if (global_k < params.k) {
+                shmem[i + bit] = select(-d, d, ((q_byte >> bit) & 1u) != 0u);
+            }
+        }
+    }
+}
+#endif // INIT_SRC0_SHMEM_Q1_0
+
 #ifdef INIT_SRC0_SHMEM_Q4_0
 const BLOCK_SIZE = 32u;
 const BLOCK_SIZE_BYTES = 18u;

ggml/src/ggml-webgpu/wgsl-shaders/mul_mat_vec.wgsl

@@ -128,6 +128,38 @@ fn main(
     }
 #endif
 
+#ifdef MUL_ACC_Q1_0
+#define BLOCK_SIZE 128
+#define BLOCK_SIZE_BYTES 18
+#define THREADS_PER_BLOCK 16
+#define ELEMS_PER_THREAD (BLOCK_SIZE/THREADS_PER_BLOCK)
+
+    let num_blocks = params.k / BLOCK_SIZE;
+    let thread_within_block = thread_id % THREADS_PER_BLOCK;
+    for (var block = thread_id / THREADS_PER_BLOCK; block < num_blocks; block += WG_SIZE / THREADS_PER_BLOCK) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + thread_within_block * ELEMS_PER_THREAD;
+        var x_block: array<f32, ELEMS_PER_THREAD>;
+        for (var i = 0u; i < ELEMS_PER_THREAD; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let q_byte = load_u32_at_src0(block_byte_base + 2u + thread_within_block) & 0xFFu;
+                var row_sum = 0.0;
+                for (var bit = 0u; bit < 8u; bit++) {
+                    let w = select(-d, d, ((q_byte >> bit) & 1u) != 0u);
+                    row_sum += w * x_block[bit];
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
 #ifdef MUL_ACC_Q4_0
 #define BLOCK_SIZE 32
 #define BLOCK_SIZE_BYTES 18
@@ -812,6 +844,520 @@ fn main(
     }
 #endif
 
+#ifdef MUL_ACC_IQ1_S
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 50
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+
+                let d     = f32(load_f16_at_src0(block_byte_base));
+                let qh    = load_u32_at_src0(block_byte_base + 34u + sub_blk * 2u) & 0xFFFFu;
+                let dl    = d * f32(2u * ((qh >> 12u) & 7u) + 1u);
+                let delta = select(IQ1_DELTA, -IQ1_DELTA, (qh & 0x8000u) != 0u);
+                let qs_w  = load_u32_at_src0(block_byte_base + 2u + sub_blk * 4u);
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l       = slot0 + ll;
+                    let qs_byte = get_byte(qs_w, l);
+                    let ig      = (qs_byte | (((qh >> (3u * l)) & 7u) << 8u)) * 8u;
+                    let gw      = iq1_grid[ig / 16u];
+                    let bit_base = (ig % 16u) * 2u;
+                    for (var j = 0u; j < 8u; j++) {
+                        let g  = (gw >> (bit_base + j * 2u)) & 3u;
+                        let gs = select(f32(g), f32(g) - 4.0, (g & 2u) != 0u);
+                        row_sum += dl * (gs + delta) * x_block[ll * 8u + j];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ1_M
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 56
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+
+                let sc_lo = load_u32_at_src0(block_byte_base + 48u);
+                let sc_hi = load_u32_at_src0(block_byte_base + 52u);
+                let sc0 = sc_lo & 0xFFFFu;
+                let sc1 = (sc_lo >> 16u) & 0xFFFFu;
+                let sc2 = sc_hi & 0xFFFFu;
+                let sc3 = (sc_hi >> 16u) & 0xFFFFu;
+                let d_bits = (sc0 >> 12u) | ((sc1 >> 8u) & 0xF0u) | ((sc2 >> 4u) & 0xF00u) | (sc3 & 0xF000u);
+                let d = f32(bitcast<vec2<f16>>(d_bits)[0]);
+
+                let sc_u16 = select(select(sc2, sc3, sub_blk >= 6u),
+                                    select(sc0, sc1, sub_blk >= 2u),
+                                    sub_blk < 4u);
+
+                let qs_w = load_u32_at_src0(block_byte_base + sub_blk * 4u);
+                let qh = load_u32_at_src0(block_byte_base + 32u + sub_blk * 2u) & 0xFFFFu;
+                let qh_lo = qh & 0xFFu;
+                let qh_hi = (qh >> 8u) & 0xFFu;
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l = slot0 + ll;
+                    let bit_off = 6u * (sub_blk % 2u) + 3u * (l / 2u);
+                    let sub_scale = (sc_u16 >> bit_off) & 0x7u;
+                    let dl = d * f32(2u * sub_scale + 1u);
+                    let qh_byte = select(qh_lo, qh_hi, l >= 2u);
+                    let ll2 = l % 2u;
+                    let grid_idx = get_byte(qs_w, l) | (((qh_byte >> (4u * ll2)) & 7u) << 8u);
+                    let delta = select(IQ1_DELTA, -IQ1_DELTA, ((qh_byte >> (3u + 4u * ll2)) & 1u) != 0u);
+                    let ig = grid_idx * 8u;
+                    let gw = iq1_grid[ig / 16u];
+                    let bit_base = (ig % 16u) * 2u;
+                    for (var j = 0u; j < 8u; j++) {
+                        let g  = (gw >> (bit_base + j * 2u)) & 3u;
+                        let gs = select(f32(g), f32(g) - 4.0, (g & 2u) != 0u);
+                        row_sum += dl * (gs + delta) * x_block[ll * 8u + j];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ2_XXS
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 66
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let aux_lo = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u);
+                let aux_hi = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u + 4u);
+                let ls = aux_hi >> 28u;
+                let db = d * (0.5 + f32(ls)) * 0.25;
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l = slot0 + ll;
+                    let grid_idx = (aux_lo >> (8u * l)) & 0xFFu;
+                    let signs_idx = (aux_hi >> (7u * l)) & 0x7Fu;
+                    let signs = (ksigns_iq2xs[signs_idx / 4u] >> ((signs_idx % 4u) * 8u)) & 0xFFu;
+                    let gw_lo = iq2xxs_grid[grid_idx * 2u];
+                    let gw_hi = iq2xxs_grid[grid_idx * 2u + 1u];
+                    for (var j = 0u; j < 8u; j++) {
+                        let gw = select(gw_hi, gw_lo, j < 4u);
+                        let b = f32((gw >> ((j & 3u) * 8u)) & 0xFFu);
+                        let s = select(1.0, -1.0, ((signs >> j) & 1u) != 0u);
+                        row_sum += db * b * s * x_block[ll * 8u + j];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ2_XS
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 74
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let qs_lo = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u);
+                let qs_hi = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u + 4u);
+                let scales_word = load_u32_at_src0(block_byte_base + 66u + (sub_blk / 4u) * 4u);
+                let scales_byte = get_byte(scales_word, sub_blk % 4u);
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l = slot0 + ll;
+                    let qs_word = select(qs_hi, qs_lo, l < 2u);
+                    let half2 = (l % 2u) * 16u;
+                    let qs_val = (qs_word >> half2) & 0xFFFFu;
+                    let grid_idx = qs_val & 0x1FFu;
+                    let signs_idx = (qs_val >> 9u) & 0x7Fu;
+                    let sub_scale = (scales_byte >> (4u * (l / 2u))) & 0xFu;
+                    let db = d * (0.5 + f32(sub_scale)) * 0.25;
+                    let signs = (ksigns_iq2xs[signs_idx / 4u] >> ((signs_idx % 4u) * 8u)) & 0xFFu;
+                    let gw_lo = iq2xs_grid[grid_idx * 2u];
+                    let gw_hi = iq2xs_grid[grid_idx * 2u + 1u];
+                    for (var j = 0u; j < 8u; j++) {
+                        let gw = select(gw_hi, gw_lo, j < 4u);
+                        let b = f32((gw >> ((j & 3u) * 8u)) & 0xFFu);
+                        let s = select(1.0, -1.0, ((signs >> j) & 1u) != 0u);
+                        row_sum += db * b * s * x_block[ll * 8u + j];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ2_S
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 82
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let qs_w = load_u32_at_src0(block_byte_base + 2u + sub_blk * 4u);
+                let sg_w = load_u32_at_src0(block_byte_base + 34u + sub_blk * 4u);
+                let qh_word = load_u32_at_src0(block_byte_base + 66u + (sub_blk / 4u) * 4u);
+                let qh_byte = get_byte(qh_word, sub_blk % 4u);
+                let sc_word = load_u32_at_src0(block_byte_base + 74u + (sub_blk / 4u) * 4u);
+                let scales_byte = get_byte(sc_word, sub_blk % 4u);
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l = slot0 + ll;
+                    let qs_byte = get_byte(qs_w, l);
+                    let sign_byte = get_byte(sg_w, l);
+                    let grid_idx = qs_byte | (((qh_byte >> (2u * l)) & 3u) << 8u);
+                    let sub_scale = (scales_byte >> (4u * (l / 2u))) & 0xFu;
+                    let db = d * (0.5 + f32(sub_scale)) * 0.25;
+                    let gw_lo = iq2s_grid[grid_idx * 2u];
+                    let gw_hi = iq2s_grid[grid_idx * 2u + 1u];
+                    for (var j = 0u; j < 8u; j++) {
+                        let gw = select(gw_hi, gw_lo, j < 4u);
+                        let b = f32((gw >> ((j & 3u) * 8u)) & 0xFFu);
+                        let s = select(1.0, -1.0, ((sign_byte >> j) & 1u) != 0u);
+                        row_sum += db * b * s * x_block[ll * 8u + j];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ3_XXS
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 98
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let qs_lo = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u);
+                let qs_hi = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u + 4u);
+                let aux = load_u32_at_src0(block_byte_base + 66u + sub_blk * 4u);
+                let ls = aux >> 28u;
+                let db = d * (0.5 + f32(ls)) * 0.5;
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l = slot0 + ll;
+                    let qs_word = select(qs_hi, qs_lo, l < 2u);
+                    let byte_pos = (l % 2u) * 2u;
+                    let grid_idx_0 = (qs_word >> (byte_pos * 8u)) & 0xFFu;
+                    let grid_idx_1 = (qs_word >> ((byte_pos + 1u) * 8u)) & 0xFFu;
+                    let signs_idx = (aux >> (7u * l)) & 0x7Fu;
+                    let signs = (ksigns_iq2xs[signs_idx / 4u] >> ((signs_idx % 4u) * 8u)) & 0xFFu;
+                    let grid1 = iq3xxs_grid[grid_idx_0];
+                    let grid2 = iq3xxs_grid[grid_idx_1];
+                    for (var j = 0u; j < 4u; j++) {
+                        let b1 = f32((grid1 >> (j * 8u)) & 0xFFu);
+                        let b2 = f32((grid2 >> (j * 8u)) & 0xFFu);
+                        let s1 = select(1.0, -1.0, ((signs >> j) & 1u) != 0u);
+                        let s2 = select(1.0, -1.0, ((signs >> (j + 4u)) & 1u) != 0u);
+                        row_sum += db * b1 * s1 * x_block[ll * 8u + j];
+                        row_sum += db * b2 * s2 * x_block[ll * 8u + j + 4u];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ3_S
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 110
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let slot0   = half * 2u;
+    let y_offset = sub_blk * 32u + slot0 * 8u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let qs_lo = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u);
+                let qs_hi = load_u32_at_src0(block_byte_base + 2u + sub_blk * 8u + 4u);
+                let qh_word = load_u32_at_src0(block_byte_base + 66u + (sub_blk / 4u) * 4u);
+                let qh_byte = get_byte(qh_word, sub_blk % 4u);
+                let sg_w = load_u32_at_src0(block_byte_base + 74u + sub_blk * 4u);
+                let sc_word = load_u32_at_src0(block_byte_base + 106u);
+                let scales_byte = get_byte(sc_word, sub_blk / 2u);
+                let sub_scale = (scales_byte >> (4u * (sub_blk % 2u))) & 0xFu;
+                let db = d * (1.0 + 2.0 * f32(sub_scale));
+
+                var row_sum = 0.0;
+                for (var ll = 0u; ll < 2u; ll++) {
+                    let l = slot0 + ll;
+                    let qs_word = select(qs_hi, qs_lo, l < 2u);
+                    let byte_pos = (l % 2u) * 2u;
+                    let qs0 = (qs_word >> (byte_pos * 8u)) & 0xFFu;
+                    let qs1 = (qs_word >> ((byte_pos + 1u) * 8u)) & 0xFFu;
+                    let grid_idx_1 = qs0 | (((qh_byte >> (2u * l)) & 1u) << 8u);
+                    let grid_idx_2 = qs1 | (((qh_byte >> (2u * l + 1u)) & 1u) << 8u);
+                    let sign_byte = get_byte(sg_w, l);
+                    let grid1 = iq3s_grid[grid_idx_1];
+                    let grid2 = iq3s_grid[grid_idx_2];
+                    for (var j = 0u; j < 4u; j++) {
+                        let b1 = f32((grid1 >> (j * 8u)) & 0xFFu);
+                        let b2 = f32((grid2 >> (j * 8u)) & 0xFFu);
+                        let s1 = select(1.0, -1.0, ((sign_byte >> j) & 1u) != 0u);
+                        let s2 = select(1.0, -1.0, ((sign_byte >> (j + 4u)) & 1u) != 0u);
+                        row_sum += db * b1 * s1 * x_block[ll * 8u + j];
+                        row_sum += db * b2 * s2 * x_block[ll * 8u + j + 4u];
+                    }
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ4_NL
+#define BLOCK_SIZE 32
+#define BLOCK_SIZE_BYTES 18
+#define THREADS_PER_BLOCK 4
+#define ELEMS_PER_THREAD (BLOCK_SIZE/THREADS_PER_BLOCK)
+
+    let num_blocks = params.k / BLOCK_SIZE;
+    let thread_within_block = thread_id % THREADS_PER_BLOCK;
+    for (var block = thread_id / THREADS_PER_BLOCK; block < num_blocks; block += WG_SIZE / THREADS_PER_BLOCK) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + thread_within_block * 4u;
+        var x_block: array<f32, ELEMS_PER_THREAD>;
+        for (var i = 0u; i < ELEMS_PER_THREAD / 2u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+            x_block[i + 4u] = f32(src1[x_base + i + 16u]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                var row_sum = 0.0;
+
+                let q_packed = load_u32_at_src0(block_byte_base + 2u + 4u * thread_within_block);
+                for (var byte_idx = 0u; byte_idx < 4u; byte_idx++) {
+                    let q_byte = get_byte(q_packed, byte_idx);
+                    let q_lo = f32(kvalues_iq4nl[q_byte & 0xFu]) * d;
+                    let q_hi = f32(kvalues_iq4nl[(q_byte >> 4u) & 0xFu]) * d;
+                    row_sum += q_lo * x_block[byte_idx];
+                    row_sum += q_hi * x_block[byte_idx + 4u];
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
+#ifdef MUL_ACC_IQ4_XS
+#define BLOCK_SIZE 256
+#define BLOCK_SIZE_BYTES 136
+#define THREADS_PER_BLOCK 16
+
+    let tid = thread_id % THREADS_PER_BLOCK;
+    let block_group = thread_id / THREADS_PER_BLOCK;
+    let num_block_groups: u32 = WG_SIZE / THREADS_PER_BLOCK;
+
+    let sub_blk = tid / 2u;
+    let half    = tid % 2u;
+    let y_offset = sub_blk * 32u + half * 16u;
+
+    let num_blocks = params.k / BLOCK_SIZE;
+
+    for (var block = block_group; block < num_blocks; block += num_block_groups) {
+        let x_base = src1_idx_base + block * BLOCK_SIZE + y_offset;
+        var x_block: array<f32, 16>;
+        for (var i = 0u; i < 16u; i++) {
+            x_block[i] = f32(src1[x_base + i]);
+        }
+
+        for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
+            let output_row = row_base + row;
+            if (output_row < params.m) {
+                let block_byte_base = (src0_batch_offset + output_row * params.stride_01 + block) * BLOCK_SIZE_BYTES;
+                let d = f32(load_f16_at_src0(block_byte_base));
+                let scales_h = load_u16_at_src0(block_byte_base + 2u);
+                let scales_l_word = load_u32_at_src0(block_byte_base + 4u);
+                let sl_byte = get_byte(scales_l_word, sub_blk / 2u);
+                let sl = (sl_byte >> (4u * (sub_blk % 2u))) & 0xFu;
+                let sh_bits = (scales_h >> (2u * sub_blk)) & 3u;
+                let ls = i32(sl | (sh_bits << 4u));
+                let dl = d * f32(ls - 32);
+
+                let qs_byte_off = 8u + sub_blk * 16u;
+                let q_w0 = load_u32_at_src0(block_byte_base + qs_byte_off);
+                let q_w1 = load_u32_at_src0(block_byte_base + qs_byte_off + 4u);
+                let q_w2 = load_u32_at_src0(block_byte_base + qs_byte_off + 8u);
+                let q_w3 = load_u32_at_src0(block_byte_base + qs_byte_off + 12u);
+
+                var row_sum = 0.0;
+                for (var i = 0u; i < 16u; i++) {
+                    let q_word = select(
+                        select(q_w0, q_w1, i >= 4u),
+                        select(q_w2, q_w3, i >= 12u),
+                        i >= 8u);
+                    let q_byte = get_byte(q_word, i % 4u);
+                    let nib = select(q_byte & 0xFu, (q_byte >> 4u) & 0xFu, half == 1u);
+                    row_sum += f32(kvalues_iq4nl[nib]) * dl * x_block[i];
+                }
+                acc[row] += row_sum;
+            }
+        }
+    }
+#endif
+
 #ifdef USE_SUBGROUP_REDUCTION
     for (var row = 0u; row < OUTPUTS_PER_WG; row++) {
         let subgroup_total = subgroupAdd(acc[row]);

tests/test-chat.cpp

@@ -2249,6 +2249,46 @@ static void test_template_output_peg_parsers(bool detailed_debug) {
             .reasoning_format(COMMON_REASONING_FORMAT_AUTO)
             .expect(message_assist)
             .run();
+
+        {
+            // additional tests for https://github.com/ggml-org/llama.cpp/pull/21760
+            auto tmpls = read_templates("models/templates/google-gemma-4-31B-it.jinja");
+
+            common_chat_msg tool_call_msg = simple_assist_msg(
+                "Let me check.", "", "special_function", "{\"arg1\": 1}","c0");
+
+            common_chat_msg tool_msg;
+            tool_msg.role         = "tool";
+            tool_msg.tool_name    = "special_function";
+            tool_msg.tool_call_id = "c0";
+            tool_msg.content      = "{\"r\":\"ok\"}";
+
+            {
+                common_chat_templates_inputs inputs;
+                inputs.messages              = { message_user, tool_call_msg, tool_msg };
+                inputs.tools                 = { special_function_tool };
+                inputs.add_generation_prompt = true;
+
+                auto params = common_chat_templates_apply(tmpls.get(), inputs);
+
+                if (!string_ends_with(params.prompt, "<turn|>\n<|turn>model\n")) {
+                    throw std::runtime_error("Missing generation prompt for Gemma 4");
+                }
+            }
+
+            {
+                common_chat_templates_inputs inputs;
+                inputs.messages              = { message_user, tool_call_msg, tool_msg };
+                inputs.tools                 = { special_function_tool };
+                inputs.add_generation_prompt = false;
+
+                auto params = common_chat_templates_apply(tmpls.get(), inputs);
+
+                if (string_ends_with(params.prompt, "<|turn>model\n")) {
+                    throw std::runtime_error("Gemma 4: generation prompt was modified despite add_generation_prompt=false");
+                }
+            }
+        }
     }
 
     {

tools/rpc/rpc-server.cpp

@@ -317,7 +317,7 @@ int main(int argc, char * argv[]) {
     const char * cache_dir = nullptr;
     std::string cache_dir_str;
     if (params.use_cache) {
-        cache_dir_str = fs_get_cache_directory() + "rpc/";
+        cache_dir_str = fs_get_cache_directory() + "rpc" + DIRECTORY_SEPARATOR;
         if (!fs_create_directory_with_parents(cache_dir_str)) {
             fprintf(stderr, "Failed to create cache directory: %s\n", cache_dir_str.c_str());
             return 1;

tools/server/server-chat.cpp

@@ -575,14 +575,14 @@ json server_chat_msg_diff_to_json_oaicompat(const common_chat_msg_diff & diff) {
 json convert_transcriptions_to_chatcmpl(
         const json & inp_body,
         const common_chat_templates * tmpls,
-        const std::map<std::string, raw_buffer> & in_files,
+        const std::map<std::string, uploaded_file> & in_files,
         std::vector<raw_buffer> & out_files) {
     // TODO @ngxson : this function may need to be improved in the future
     // handle input files
     out_files.clear();
     auto it = in_files.find("file");
     if (it != in_files.end()) {
-        out_files.push_back(it->second);
+        out_files.push_back(it->second.data);
     } else {
         throw std::invalid_argument("No input file found for transcription");
     }

tools/server/server-chat.h

@@ -4,6 +4,7 @@
 
 #include "chat.h"
 #include "server-common.h"
+#include "server-http.h"
 
 #include <nlohmann/json_fwd.hpp>
 
@@ -19,7 +20,7 @@ json server_chat_convert_anthropic_to_oai(const json & body);
 json convert_transcriptions_to_chatcmpl(
     const json & body,
     const common_chat_templates * tmpls,
-    const std::map<std::string, raw_buffer> & in_files,
+    const std::map<std::string, uploaded_file> & in_files,
     std::vector<raw_buffer> & out_files);
 
 json server_chat_msg_diff_to_json_oaicompat(const common_chat_msg_diff & diff);

tools/server/server-cors-proxy.h

@@ -49,6 +49,7 @@ static server_http_res_ptr proxy_request(const server_http_req & req, std::strin
             parsed_url.path,
             headers,
             req.body,
+            req.files,
             req.should_stop,
             600, // timeout_read (default to 10 minutes)
             600  // timeout_write (default to 10 minutes)

tools/server/server-http.cpp

@@ -438,7 +438,7 @@ void server_http_context::get(const std::string & path, const server_http_contex
 void server_http_context::post(const std::string & path, const server_http_context::handler_t & handler) const {
     pimpl->srv->Post(path_prefix + path, [handler](const httplib::Request & req, httplib::Response & res) {
         std::string body = req.body;
-        std::map<std::string, raw_buffer> files;
+        std::map<std::string, uploaded_file> files;
 
         if (req.is_multipart_form_data()) {
             // translate text fields to a JSON object and use it as the body
@@ -459,7 +459,11 @@ void server_http_context::post(const std::string & path, const server_http_conte
 
             // populate files from multipart form
             for (const auto & [key, file] : req.form.files) {
-                files[key] = raw_buffer(file.content.begin(), file.content.end());
+                files[key] = uploaded_file{
+                    raw_buffer(file.content.begin(), file.content.end()),
+                    file.filename,
+                    file.content_type,
+                };
             }
         }
 

tools/server/server-http.h

@@ -36,13 +36,19 @@ struct server_http_res {
 using server_http_res_ptr = std::unique_ptr<server_http_res>;
 using raw_buffer = std::vector<uint8_t>;
 
+struct uploaded_file {
+    raw_buffer data;
+    std::string filename;
+    std::string content_type;
+};
+
 struct server_http_req {
     std::map<std::string, std::string> params; // path_params + query_params
     std::map<std::string, std::string> headers; // used by MCP proxy
     std::string path;
     std::string query_string; // query parameters string (e.g. "action=save")
     std::string body;
-    std::map<std::string, raw_buffer> files; // used for file uploads (form data)
+    std::map<std::string, uploaded_file> files; // used for file uploads (form data)
     const std::function<bool()> & should_stop;
 
     std::string get_param(const std::string & key, const std::string & def = "") const {

tools/server/server-models.cpp

@@ -18,6 +18,8 @@
 #include <chrono>
 #include <queue>
 #include <filesystem>
+#include <random>
+#include <sstream>
 #include <cstring>
 
 #ifdef _WIN32
@@ -823,6 +825,7 @@ server_http_res_ptr server_models::proxy_request(const server_http_req & req, co
             proxy_path,
             req.headers,
             req.body,
+            req.files,
             req.should_stop,
             base_params.timeout_read,
             base_params.timeout_write
@@ -1126,6 +1129,77 @@ static bool should_strip_proxy_header(const std::string & header_name) {
     return false;
 }
 
+static std::string generate_multipart_boundary() {
+    thread_local std::mt19937 gen(std::random_device{}());
+    static const char chars[] = "0123456789abcdefghijklmnopqrstuvwxyz";
+    std::uniform_int_distribution<> dis(0, sizeof(chars) - 2);
+    std::string boundary = "----llama-cpp-proxy-";
+    for (int i = 0; i < 16; i++) {
+        boundary += chars[dis(gen)];
+    }
+    return boundary;
+}
+
+static std::string build_multipart_body(
+        const json & form_fields,
+        const std::map<std::string, uploaded_file> & files,
+        const std::string & boundary) {
+    static auto sanitize_field = [](const std::string & text) {
+        std::string result;
+        result.reserve(text.size());
+        for (char c : text) {
+            if (c != '\n' && c != '\r' && c != '"') {
+                result += c;
+            }
+        }
+        return result;
+    };
+
+    std::ostringstream body;
+
+    for (const auto & [key, value] : form_fields.items()) {
+        if (value.is_array()) {
+            for (const auto & item : value) {
+                body << "--" << boundary << "\r\n";
+                body << "Content-Disposition: form-data; name=\"" << sanitize_field(key) << "\"\r\n";
+                body << "\r\n";
+                if (!item.is_string()) {
+                    throw std::invalid_argument("expected string");
+                }
+                body << item.get<std::string>() << "\r\n";
+            }
+        } else {
+            body << "--" << boundary << "\r\n";
+            body << "Content-Disposition: form-data; name=\"" << sanitize_field(key) << "\"\r\n";
+            body << "\r\n";
+            if (!value.is_string()) {
+                throw std::invalid_argument("expected string");
+            }
+            body << value.get<std::string>() << "\r\n";
+        }
+    }
+
+    for (const auto & [key, file] : files) {
+        body << "--" << boundary << "\r\n";
+        body << "Content-Disposition: form-data; name=\"" << sanitize_field(key) << "\"";
+        if (!file.filename.empty()) {
+            body << "; filename=\"" << sanitize_field(file.filename) << "\"";
+        }
+        body << "\r\n";
+        if (!file.content_type.empty()) {
+            body << "Content-Type: " << sanitize_field(file.content_type) << "\r\n";
+        } else {
+            body << "Content-Type: application/octet-stream\r\n";
+        }
+        body << "\r\n";
+        body.write(reinterpret_cast<const char*>(file.data.data()), file.data.size());
+        body << "\r\n";
+    }
+
+    body << "--" << boundary << "--\r\n";
+    return body.str();
+}
+
 server_http_proxy::server_http_proxy(
         const std::string & method,
         const std::string & scheme,
@@ -1134,6 +1208,7 @@ server_http_proxy::server_http_proxy(
         const std::string & path,
         const std::map<std::string, std::string> & headers,
         const std::string & body,
+        const std::map<std::string, uploaded_file> & files,
         const std::function<bool()> should_stop,
         int32_t timeout_read,
         int32_t timeout_write
@@ -1195,28 +1270,65 @@ server_http_proxy::server_http_proxy(
         return pipe->write({{}, 0, std::string(data, data_length), ""});
     };
 
+    // when files are present, the body was converted from multipart form data to JSON
+    // we need to reconstruct the multipart body for the downstream server
+    std::string effective_body = body;
+    std::string override_content_type;
+    bool has_files = !files.empty();
+
+    if (has_files) {
+        json form_fields = json::parse(body, nullptr, false);
+        if (!form_fields.is_discarded()) {
+            auto boundary = generate_multipart_boundary();
+            effective_body = build_multipart_body(form_fields, files, boundary);
+            override_content_type = "multipart/form-data; boundary=" + boundary;
+        } else {
+            throw std::runtime_error("failed to parse multipart form fields JSON");
+        }
+    }
+
     // prepare the request to destination server
     httplib::Request req;
     {
         req.method = method;
         req.path = path;
         for (const auto & [key, value] : headers) {
-            if (key == "Accept-Encoding") {
+            const auto lowered = to_lower_copy(key);
+            if (lowered == "accept-encoding") {
                 // disable Accept-Encoding to avoid compressed responses
                 continue;
             }
-            if (key == "Transfer-Encoding") {
+            if (lowered == "transfer-encoding") {
                 // the body is already decoded
                 continue;
             }
-            if (key == "Host" || key == "host") {
+            if (lowered == "content-length") {
+                // let httplib calculate Content-Length from the actual body
+                continue;
+            }
+            if (lowered == "content-type") {
+                if (has_files) {
+                    // we set our own Content-Type with the new boundary
+                    continue;
+                }
+                // when no files but the original request was multipart,
+                // the body is now JSON, so correct the Content-Type
+                if (value.find("multipart/form-data") != std::string::npos) {
+                    override_content_type = "application/json; charset=utf-8";
+                    continue;
+                }
+            }
+            if (lowered == "host") {
                 bool is_default_port = (scheme == "https" && port == 443) || (scheme == "http" && port == 80);
                 req.set_header(key, is_default_port ? host : host + ":" + std::to_string(port));
             } else {
                 req.set_header(key, value);
             }
         }
-        req.body = body;
+        req.body = effective_body;
+        if (!override_content_type.empty()) {
+            req.set_header("Content-Type", override_content_type);
+        }
         req.response_handler = response_handler;
         req.content_receiver = content_receiver;
     }

tools/server/server-models.h

@@ -202,6 +202,7 @@ public:
                       const std::string & path,
                       const std::map<std::string, std::string> & headers,
                       const std::string & body,
+                      const std::map<std::string, uploaded_file> & files,
                       const std::function<bool()> should_stop,
                       int32_t timeout_read,
                       int32_t timeout_write