diff --git a/scripts/build_msigdb_cache.R b/scripts/build_msigdb_cache.R
new file mode 100644
index 0000000..d87c497
--- /dev/null
+++ b/scripts/build_msigdb_cache.R
@@ -0,0 +1,113 @@
+#!/usr/bin/env Rscript
+
+suppressPackageStartupMessages({
+  library(dplyr)
+  library(msigdbr)
+})
+
+species_to_cache <- c(
+  "Homo sapiens",
+  "Mus musculus"
+)
+
+default_output_dir <- file.path("shiny", "data", "msigdb_genesets")
+output_dir <- Sys.getenv("MSIGDB_CACHE_DIR", unset = default_output_dir)
+
+dir.create(output_dir, recursive = TRUE, showWarnings = FALSE)
+
+slugify <- function(x) {
+  x <- gsub("[^A-Za-z0-9]+", "_", x)
+  x <- gsub("_+", "_", x)
+  x <- gsub("^_|_$", "", x)
+  x
+}
+
+fetch_msigdb <- function(species, collection, subcollection = "") {
+  msigdbr_args <- list(species = species)
+  msigdbr_formals <- names(formals(msigdbr::msigdbr))
+
+  if ("collection" %in% msigdbr_formals) {
+    msigdbr_args$collection <- collection
+  } else if ("category" %in% msigdbr_formals) {
+    msigdbr_args$category <- collection
+  }
+
+  if (nzchar(subcollection)) {
+    if ("subcollection" %in% msigdbr_formals) {
+      msigdbr_args$subcollection <- subcollection
+    } else if ("subcategory" %in% msigdbr_formals) {
+      msigdbr_args$subcategory <- subcollection
+    }
+  }
+
+  do.call(msigdbr::msigdbr, msigdbr_args)
+}
+
+geneset_cache_path <- function(species, collection, subcollection) {
+  species_slug <- slugify(species)
+  subcollection_slug <- if (nzchar(subcollection)) slugify(subcollection) else "all"
+  file.path(
+    output_dir,
+    sprintf("%s__%s__%s.rds", species_slug, collection, subcollection_slug)
+  )
+}
+
+collections <- msigdbr::msigdbr_collections() |>
+  dplyr::select(gs_collection, gs_subcollection) |>
+  dplyr::distinct() |>
+  dplyr::arrange(gs_collection, gs_subcollection)
+
+manifest <- list()
+
+for (species in species_to_cache) {
+  message("Building MSigDB cache for: ", species)
+
+  for (i in seq_len(nrow(collections))) {
+    collection <- collections$gs_collection[[i]]
+    subcollection <- collections$gs_subcollection[[i]]
+    cache_file <- geneset_cache_path(species, collection, subcollection)
+
+    message(
+      "  - ",
+      collection,
+      if (nzchar(subcollection)) paste0(" / ", subcollection) else "",
+      " -> ",
+      cache_file
+    )
+
+    msigdb_tbl <- fetch_msigdb(
+      species = species,
+      collection = collection,
+      subcollection = subcollection
+    ) |>
+      dplyr::select(gs_name, gene_symbol)
+
+    genesets <- split(msigdb_tbl$gene_symbol, msigdb_tbl$gs_name)
+    genesets <- lapply(genesets, unique)
+
+    saveRDS(genesets, cache_file, compress = "xz")
+
+    manifest[[length(manifest) + 1]] <- data.frame(
+      species = species,
+      gs_collection = collection,
+      gs_subcollection = subcollection,
+      file = basename(cache_file),
+      genesets = length(genesets),
+      genes = length(unique(unlist(genesets, use.names = FALSE))),
+      stringsAsFactors = FALSE
+    )
+
+    rm(msigdb_tbl, genesets)
+    gc(verbose = FALSE)
+  }
+}
+
+manifest_df <- do.call(rbind, manifest)
+manifest_file <- file.path(output_dir, "manifest.rds")
+manifest_csv <- file.path(output_dir, "manifest.csv")
+
+saveRDS(manifest_df, manifest_file, compress = "xz")
+utils::write.csv(manifest_df, manifest_csv, row.names = FALSE)
+
+message("MSigDB cache complete.")
+message("Manifest: ", manifest_file)
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+++ b/shiny/data/msigdb_genesets/manifest.csv
@@ -0,0 +1,51 @@
+"species","gs_collection","gs_subcollection","file","genesets","genes"
+"Homo sapiens","C1","","Homo_sapiens__C1__all.rds",302,43321
+"Homo sapiens","C2","CGP","Homo_sapiens__C2__CGP.rds",3538,21705
+"Homo sapiens","C2","CP","Homo_sapiens__C2__CP.rds",19,349
+"Homo sapiens","C2","CP:BIOCARTA","Homo_sapiens__C2__CP_BIOCARTA.rds",292,1509
+"Homo sapiens","C2","CP:KEGG_LEGACY","Homo_sapiens__C2__CP_KEGG_LEGACY.rds",186,5245
+"Homo sapiens","C2","CP:KEGG_MEDICUS","Homo_sapiens__C2__CP_KEGG_MEDICUS.rds",658,2788
+"Homo sapiens","C2","CP:PID","Homo_sapiens__C2__CP_PID.rds",196,2534
+"Homo sapiens","C2","CP:REACTOME","Homo_sapiens__C2__CP_REACTOME.rds",1787,11369
+"Homo sapiens","C2","CP:WIKIPATHWAYS","Homo_sapiens__C2__CP_WIKIPATHWAYS.rds",885,9127
+"Homo sapiens","C3","MIR:MIRDB","Homo_sapiens__C3__MIR_MIRDB.rds",2377,16652
+"Homo sapiens","C3","MIR:MIR_LEGACY","Homo_sapiens__C3__MIR_MIR_LEGACY.rds",221,7450
+"Homo sapiens","C3","TFT:GTRD","Homo_sapiens__C3__TFT_GTRD.rds",505,26928
+"Homo sapiens","C3","TFT:TFT_LEGACY","Homo_sapiens__C3__TFT_TFT_LEGACY.rds",610,12779
+"Homo sapiens","C4","3CA","Homo_sapiens__C4__3CA.rds",148,2992
+"Homo sapiens","C4","CGN","Homo_sapiens__C4__CGN.rds",427,4883
+"Homo sapiens","C4","CM","Homo_sapiens__C4__CM.rds",431,8359
+"Homo sapiens","C5","GO:BP","Homo_sapiens__C5__GO_BP.rds",7583,18000
+"Homo sapiens","C5","GO:CC","Homo_sapiens__C5__GO_CC.rds",1042,14869
+"Homo sapiens","C5","GO:MF","Homo_sapiens__C5__GO_MF.rds",1855,15699
+"Homo sapiens","C5","HPO","Homo_sapiens__C5__HPO.rds",5748,5112
+"Homo sapiens","C6","","Homo_sapiens__C6__all.rds",189,10927
+"Homo sapiens","C7","IMMUNESIGDB","Homo_sapiens__C7__IMMUNESIGDB.rds",4872,20440
+"Homo sapiens","C7","VAX","Homo_sapiens__C7__VAX.rds",347,13431
+"Homo sapiens","C8","","Homo_sapiens__C8__all.rds",866,20533
+"Homo sapiens","H","","Homo_sapiens__H__all.rds",50,4384
+"Mus musculus","C1","","Mus_musculus__C1__all.rds",297,17961
+"Mus musculus","C2","CGP","Mus_musculus__C2__CGP.rds",3537,17514
+"Mus musculus","C2","CP","Mus_musculus__C2__CP.rds",19,350
+"Mus musculus","C2","CP:BIOCARTA","Mus_musculus__C2__CP_BIOCARTA.rds",292,1513
+"Mus musculus","C2","CP:KEGG_LEGACY","Mus_musculus__C2__CP_KEGG_LEGACY.rds",186,5032
+"Mus musculus","C2","CP:KEGG_MEDICUS","Mus_musculus__C2__CP_KEGG_MEDICUS.rds",658,2718
+"Mus musculus","C2","CP:PID","Mus_musculus__C2__CP_PID.rds",196,2546
+"Mus musculus","C2","CP:REACTOME","Mus_musculus__C2__CP_REACTOME.rds",1787,10688
+"Mus musculus","C2","CP:WIKIPATHWAYS","Mus_musculus__C2__CP_WIKIPATHWAYS.rds",885,8516
+"Mus musculus","C3","MIR:MIRDB","Mus_musculus__C3__MIR_MIRDB.rds",2377,15499
+"Mus musculus","C3","MIR:MIR_LEGACY","Mus_musculus__C3__MIR_MIR_LEGACY.rds",221,7303
+"Mus musculus","C3","TFT:GTRD","Mus_musculus__C3__TFT_GTRD.rds",502,16143
+"Mus musculus","C3","TFT:TFT_LEGACY","Mus_musculus__C3__TFT_TFT_LEGACY.rds",610,12357
+"Mus musculus","C4","3CA","Mus_musculus__C4__3CA.rds",148,2875
+"Mus musculus","C4","CGN","Mus_musculus__C4__CGN.rds",427,4751
+"Mus musculus","C4","CM","Mus_musculus__C4__CM.rds",431,8079
+"Mus musculus","C5","GO:BP","Mus_musculus__C5__GO_BP.rds",7580,15844
+"Mus musculus","C5","GO:CC","Mus_musculus__C5__GO_CC.rds",1042,13330
+"Mus musculus","C5","GO:MF","Mus_musculus__C5__GO_MF.rds",1852,14226
+"Mus musculus","C5","HPO","Mus_musculus__C5__HPO.rds",5748,5027
+"Mus musculus","C6","","Mus_musculus__C6__all.rds",189,10255
+"Mus musculus","C7","IMMUNESIGDB","Mus_musculus__C7__IMMUNESIGDB.rds",4872,17329
+"Mus musculus","C7","VAX","Mus_musculus__C7__VAX.rds",346,11828
+"Mus musculus","C8","","Mus_musculus__C8__all.rds",866,15683
+"Mus musculus","H","","Mus_musculus__H__all.rds",50,4393
diff --git a/shiny/data/msigdb_genesets/manifest.rds b/shiny/data/msigdb_genesets/manifest.rds
new file mode 100644
index 0000000..37ea109
Binary files /dev/null and b/shiny/data/msigdb_genesets/manifest.rds differ
diff --git a/shiny/modules/hypeR_module.R b/shiny/modules/hypeR_module.R
index cf9faac..4dfc818 100644
--- a/shiny/modules/hypeR_module.R
+++ b/shiny/modules/hypeR_module.R
@@ -26,6 +26,90 @@ msigdb_collection_metadata <- data.frame(
 )
 
 
+fetch_msigdb_table <- function(species, collection, subcollection = "") {
+  msigdbr_args <- list(species = species)
+  msigdbr_formals <- names(formals(msigdbr::msigdbr))
+
+  if ("collection" %in% msigdbr_formals) {
+    msigdbr_args$collection <- collection
+  } else if ("category" %in% msigdbr_formals) {
+    msigdbr_args$category <- collection
+  }
+
+  if (!is.null(subcollection) && nzchar(subcollection)) {
+    if ("subcollection" %in% msigdbr_formals) {
+      msigdbr_args$subcollection <- subcollection
+    } else if ("subcategory" %in% msigdbr_formals) {
+      msigdbr_args$subcategory <- subcollection
+    }
+  }
+
+  msigdb_tbl <- do.call(msigdbr::msigdbr, msigdbr_args)
+
+  required_columns <- c("gs_name", "gs_collection", "gs_subcollection", "gene_symbol")
+  missing_columns <- setdiff(required_columns, names(msigdb_tbl))
+
+  if (length(missing_columns) > 0) {
+    stop(
+      sprintf(
+        "MSigDB result is missing required columns: %s",
+        paste(missing_columns, collapse = ", ")
+      ),
+      call. = FALSE
+    )
+  }
+
+  msigdb_tbl |>
+    dplyr::select(
+      gs_name,
+      gs_collection,
+      gs_subcollection,
+      gene_symbol
+    )
+}
+
+
+msigdb_cache_dir <- function() {
+  Sys.getenv(
+    "MSIGDB_CACHE_DIR",
+    unset = file.path("shiny", "data", "msigdb_genesets")
+  )
+}
+
+
+msigdb_slugify <- function(x) {
+  x <- gsub("[^A-Za-z0-9]+", "_", x)
+  x <- gsub("_+", "_", x)
+  gsub("^_|_$", "", x)
+}
+
+
+msigdb_cache_file <- function(species, collection, subcollection = "") {
+  species_slug <- msigdb_slugify(species)
+  subcollection_slug <- if (!is.null(subcollection) && nzchar(subcollection)) {
+    msigdb_slugify(subcollection)
+  } else {
+    "all"
+  }
+
+  file.path(
+    msigdb_cache_dir(),
+    sprintf("%s__%s__%s.rds", species_slug, collection, subcollection_slug)
+  )
+}
+
+
+load_cached_msigdb_genesets <- function(species, collection, subcollection = "") {
+  cache_file <- msigdb_cache_file(species, collection, subcollection)
+
+  if (!file.exists(cache_file)) {
+    return(NULL)
+  }
+
+  readRDS(cache_file)
+}
+
+
 # hypeR genests ui rewrite
 #' Shiny UI for MSigDB subcategory selection
 #'
@@ -136,18 +220,61 @@ genesets_hypeR_Server <- function(id, species, clean = FALSE) {
       req(input$collection)
       req(!is.null(input$subcategory))
 
-      filtered_tbl <- msigdbr::msigdbr(species = species()) |>
-        dplyr::select(
-          gs_name,
-          gs_collection,
-          gs_subcollection,
-          gene_symbol
-        ) |>
-        dplyr::filter(gs_collection == input$collection)
-
-      if (!identical(input$subcategory, "")) {
-        filtered_tbl <- filtered_tbl |>
-          dplyr::filter(gs_subcollection == input$subcategory)
+      selected_genesets(list())
+
+      cached_genesets <- tryCatch(
+        load_cached_msigdb_genesets(
+          species = species(),
+          collection = input$collection,
+          subcollection = input$subcategory
+        ),
+        error = function(err) {
+          showNotification(
+            sprintf("Failed to load cached genesets: %s", conditionMessage(err)),
+            type = "error",
+            duration = 10
+          )
+          NULL
+        }
+      )
+
+      if (!is.null(cached_genesets)) {
+        if (clean) {
+          names(cached_genesets) <- clean_genesets(names(cached_genesets))
+        }
+
+        selected_genesets(cached_genesets)
+        showNotification("Loaded genesets from local cache.", type = "message")
+        return()
+      }
+
+      filtered_tbl <- tryCatch(
+        {
+          shiny::withProgress(
+            message = "Fetching MSigDB genesets...",
+            value = 0.25,
+            {
+              fetch_msigdb_table(
+                species = species(),
+                collection = input$collection,
+                subcollection = input$subcategory
+              )
+            }
+          )
+        },
+        error = function(err) {
+          showNotification(
+            sprintf("Failed to fetch genesets: %s", conditionMessage(err)),
+            type = "error",
+            duration = 10
+          )
+          NULL
+        }
+      )
+
+      if (is.null(filtered_tbl)) {
+        selected_genesets(list())
+        return()
       }
 
       if (nrow(filtered_tbl) == 0) {
@@ -156,15 +283,16 @@ genesets_hypeR_Server <- function(id, species, clean = FALSE) {
         return()
       }
 
-      gs <- filtered_tbl |>
-        (\(df) split(df, df$gs_name))() |>
-        (\(lst) lapply(lst, function(x) unique(x$gene_symbol)))()
+      gs <- split(filtered_tbl$gene_symbol, filtered_tbl$gs_name)
+      gs <- lapply(gs, unique)
       
       if (clean) {
         names(gs) <- clean_genesets(names(gs))
       }
       
       selected_genesets(gs)
+      rm(filtered_tbl)
+      gc(verbose = FALSE)
     })
     
     # Status message