Replace segmentation model type heuristic with arch field

src/ai/backend.h

@@ -93,10 +93,11 @@ typedef struct dt_ai_context_t dt_ai_context_t;
  * @brief Model Metadata (ReadOnly)
  */
 typedef struct dt_ai_model_info_t {
-  const char *id;          ///< Unique ID (e.g. "nafnet-sidd")
+  const char *id;          ///< Unique ID (e.g. "mask-object-segnext-b2hq")
   const char *name;        ///< Display name
   const char *description; ///< Short description
-  const char *task_type;   ///< e.g. "denoise", "inpainting"
+  const char *task_type;   ///< e.g. "mask", "denoise"
+  const char *arch;        ///< e.g. "sam2", "segnext"
   const char *backend;     ///< Backend type (e.g. "onnx")
   int num_inputs;          ///< Number of model inputs (default 1)
 } dt_ai_model_info_t;

src/ai/backend_common.c

@@ -143,6 +143,11 @@ static void _scan_directory(dt_ai_environment_t *env, const char *root_path)
               _store_string(env, name, &info->name);
               _store_string(env, desc, &info->description);
               _store_string(env, task, &info->task_type);
+
+              const char *arch = json_object_has_member(obj, "arch")
+                ? json_object_get_string_member(obj, "arch")
+                : "";
+              _store_string(env, arch, &info->arch);
               _store_string(env, backend, &info->backend);
               info->num_inputs = json_object_has_member(obj, "num_inputs")
                 ? (int)json_object_get_int_member(obj, "num_inputs")

src/ai/segmentation.c

@@ -300,20 +300,20 @@ dt_seg_context_t *dt_seg_load(dt_ai_environment_t *env, const char *model_id)
            ctx->enc_order[0], ctx->enc_order[1], ctx->enc_order[2], ctx->enc_order[3],
            ctx->n_enc_outputs);
 
-  // detect model type from decoder output count
-  // SAM: 3+ outputs (masks, iou_predictions, low_res_masks)
-  // SegNext: 1 output (mask)
-  const int n_dec_outputs = dt_ai_get_output_count(decoder);
+  // detect model type from arch field in model registry
+  const dt_ai_model_info_t *minfo
+    = dt_ai_get_model_info_by_id(env, model_id);
+  const char *arch = minfo ? minfo->arch : "";
 
-  if(n_dec_outputs >= 3)
+  if(strcmp(arch, "sam2") == 0)
     ctx->model_type = DT_SEG_MODEL_SAM;
-  else if(n_dec_outputs == 1)
+  else if(strcmp(arch, "segnext") == 0)
     ctx->model_type = DT_SEG_MODEL_SEGNEXT;
   else
   {
     dt_print(DT_DEBUG_AI,
-             "[segmentation] decoder has %d outputs, unsupported for %s",
-             n_dec_outputs, model_id);
+             "[segmentation] unknown arch '%s' for %s",
+             arch, model_id);
     dt_seg_free(ctx);
     return NULL;
   }

src/common/ai_models.h

@@ -46,7 +46,7 @@ typedef enum dt_ai_model_status_t
  */
 typedef struct dt_ai_model_t
 {
-  char *id;              // Unique identifier (e.g. "nafnet-sidd-width32")
+  char *id;              // Unique identifier (e.g. "mask-object-segnext-b2hq")
   char *name;            // Display name
   char *description;     // Short description
   char *task;            // Task type: "denoise", "upscale", etc.