diff --git a/ggml/src/ggml-vulkan/ggml-vulkan.cpp b/ggml/src/ggml-vulkan/ggml-vulkan.cpp
index 7b53d1b5c3..8777c340ab 100644
--- a/ggml/src/ggml-vulkan/ggml-vulkan.cpp
+++ b/ggml/src/ggml-vulkan/ggml-vulkan.cpp
@@ -7037,7 +7037,9 @@ static void ggml_vk_mul_mat_id_q_f16(ggml_backend_vk_context * ctx, vk_context&
     // n_as counts, n_as offsets, one total, then one packed row id per (expert, token).
     // Hoisting requires 16-bit indices for the packing and a table that fits one binding.
     const uint64_t hoisted_row_id_words = 2 * n_as + 1 + nei0 * nei1;
-    const bool hoist_row_ids = n_as <= 256 && nei0 <= 0xffff && nei1 <= 0xffff &&
+    // 1024 matches MAX_EXPERTS in count_experts.comp and LLAMA_MAX_EXPERTS. It costs
+    // 3 * 1024 * 4 = 12 KiB of shared memory, within the 16 KiB Vulkan guarantees.
+    const bool hoist_row_ids = n_as <= 1024 && nei0 <= 0xffff && nei1 <= 0xffff &&
                                 hoisted_row_id_words * sizeof(uint32_t) <=
                                     ctx->device->properties.limits.maxStorageBufferRange;
 
diff --git a/ggml/src/ggml-vulkan/vulkan-shaders/count_experts.comp b/ggml/src/ggml-vulkan/vulkan-shaders/count_experts.comp
index ef659959d9..06a50181c4 100644
--- a/ggml/src/ggml-vulkan/vulkan-shaders/count_experts.comp
+++ b/ggml/src/ggml-vulkan/vulkan-shaders/count_experts.comp
@@ -30,9 +30,14 @@ layout(local_size_x = BLOCK_SIZE, local_size_y = 1, local_size_z = 1) in;
 layout (binding = 0) readonly buffer A {uint data_a[];};
 layout (binding = 1) writeonly buffer D {uint data_d[];};
 
-shared uint vals[BLOCK_SIZE];
-shared uint offsets[BLOCK_SIZE];
-shared uint cursors[BLOCK_SIZE];
+// Upper bound on n_experts for the hoisted row-id path. Must match the limit in
+// ggml_vk_mul_mat_id_q_f16 (hoist_row_ids). The non-hoisted reduction below only
+// needs BLOCK_SIZE entries.
+#define MAX_EXPERTS 1024
+
+shared uint vals[MAX_EXPERTS];
+shared uint offsets[MAX_EXPERTS];
+shared uint cursors[MAX_EXPERTS];
 
 // data_d layout when p.hoist_row_ids is set:
 //   [0,              n_experts)   per-expert row count
@@ -46,8 +51,8 @@ void main() {
     const uint tid = gl_LocalInvocationID.x;
 
     if (p.hoist_row_ids != 0) {
-        if (tid < p.n_experts) {
-            vals[tid] = 0;
+        for (uint e = tid; e < p.n_experts; e += BLOCK_SIZE) {
+            vals[e] = 0;
         }
         barrier();
 
diff --git a/tests/test-backend-ops.cpp b/tests/test-backend-ops.cpp
index dc529a352b..260ffef66d 100644
--- a/tests/test-backend-ops.cpp
+++ b/tests/test-backend-ops.cpp
@@ -10077,6 +10077,14 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
 
     // gpt-oss issue with Vulkan mmq_id
     test_cases.emplace_back(new test_mul_mat_id(GGML_TYPE_MXFP4, GGML_TYPE_F32, 32, 2, false, 2880, 32, 2880));
+    // more than 256 experts (hoisted row-id path): 512 as in Qwen3.8-Flash-Next,
+    // and 1024 at the LLAMA_MAX_EXPERTS limit
+    for (int n : {1, 5, 64, 300}) {
+        test_cases.emplace_back(new test_mul_mat_id(GGML_TYPE_IQ3_S,  GGML_TYPE_F32,  512, 10, false, 128, n, 512));
+        test_cases.emplace_back(new test_mul_mat_id(GGML_TYPE_Q4_0,   GGML_TYPE_F32,  512, 10, false, 256, n, 128));
+        test_cases.emplace_back(new test_mul_mat_id(GGML_TYPE_IQ3_S,  GGML_TYPE_F32, 1024, 10, false, 128, n, 512));
+        test_cases.emplace_back(new test_mul_mat_id(GGML_TYPE_Q4_0,   GGML_TYPE_F32, 1024, 10, false, 256, n, 128));
+    }
     test_cases.emplace_back(new test_mul_mat_id(GGML_TYPE_Q4_0, GGML_TYPE_F32, 32, 2, false, 2880, 32, 2880));
 
     // multiple blocks per row: exercises the block-stride loop and the