diff --git a/NEWS.md b/NEWS.md
index 7417ae9..1a0d44e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,6 @@
 # fireSense_dataPrepFit 1.3.0.9011 (development version)
 
+- New parameter `fitFileSuffix` (default `""`), the same in `fireSense_spreadFit`, `fireSense_ignitionFit` and `fireSense_ELFs` (checked with `paramCheckOtherMods()`): with `spreadFitFilename = "latest"`, the SpreadFit ledger is read from the files with that suffix only (`fireSenseUtils::latestSpreadFits(suffix =)`), so a test run never reads the production fits. `""` is unchanged. Needs fireSenseUtils (>= 0.2.3.9104).
 - R CMD check of the module's package form has no notes: `NEWS.md` had two "(development version)" headings and none with a version, so it could not be parsed (one heading now, with the version), undefined names are declared (`R/globals.R`), and `methods`, `stats` and `utils` are in `reqdPkgs` for `is()`, `setNames()`, `var()`, `getFromNamespace()` and `modifyList()`. No change to results. One check warning remains: `SpaDES.core::convertToPackage()` writes `import()` for every `reqdPkgs` entry, so the whole-package imports clash ("replacing previous import").
 
 - Fixed: `.inputObjects` (1-2 h of data preparation per ELF) was redone whenever the SpreadFit ledger changed, e.g. when any ELF's fit landed, because `spreadFitPreRun` was declared as an input and `fireSense_ELFs` puts the whole ledger in the simList before `.inputObjects` runs. It is now an output only. `.inputObjects` never reads it; `Init()` always assigns it (this study area's rows from `CacheGeo`, or `NULL`), and `dataPrepBuild`, `prepIgnitionFitData`, `prepEscapeFitData` and `prepSpreadFitData` key on it through `.useCacheArgs`, so a new fit of this study area still re-runs them and a cached event cannot restore an old row. Results are unchanged; the `.inputObjects` key changes once.
diff --git a/R/readSpreadFitLedger.R b/R/readSpreadFitLedger.R
index 7389704..4ef4ace 100644
--- a/R/readSpreadFitLedger.R
+++ b/R/readSpreadFitLedger.R
@@ -6,14 +6,16 @@
 #' (`prepInputs()` would otherwise find its checksum changed and try to download it).
 #'
 #' @param spreadFitFilename The module's `spreadFitFilename`: a file in `cloudFolderID`, or `"latest"`.
+#' @param fitFileSuffix With `"latest"`, only ledger files with this suffix are read; see
+#'   `fireSenseUtils::spreadFitFilenameFor()`.
 #' @param cloudFolderID The Google Drive folder holding the ledger files.
 #' @param domain The study area, an `sf` object.
 #' @param destinationPath Where the ledger files are downloaded.
 #' @return What `CacheGeo()` returns: the ledger rows within `domain`, or `NULL`.
-readSpreadFitLedger <- function(spreadFitFilename, cloudFolderID, domain, destinationPath) {
+readSpreadFitLedger <- function(spreadFitFilename, cloudFolderID, domain, destinationPath, fitFileSuffix = "") {
   purge <- 7                                         # download the named file again: it changes on Drive
   if (identical(spreadFitFilename, "latest")) {
-    latest <- fireSenseUtils::latestSpreadFits(cloudFolderID, destinationPath)
+    latest <- fireSenseUtils::latestSpreadFits(cloudFolderID, destinationPath, suffix = fitFileSuffix)
     if (is.null(latest))
       return(NULL)
     tf <- tempfile(fileext = ".rds")
diff --git a/fireSense_dataPrepFit.R b/fireSense_dataPrepFit.R
index 101f4c9..41abb8d 100644
--- a/fireSense_dataPrepFit.R
+++ b/fireSense_dataPrepFit.R
@@ -17,7 +17,7 @@ defineModule(sim, list(
   reqdPkgs = list("data.table", "fastDummies", "Require",
                   "PredictiveEcology/reproducible@development (>= 3.2.1.9042)", # CacheGeo re-reads a changed local file
                   "PredictiveEcology/climateData@development (>= 2.2.3.9006)",
-                  "PredictiveEcology/fireSenseUtils@development (>= 0.2.3.9100)", # dataYearBefore(), dataYearElement(before =); defaultFireYears() from 1986
+                  "PredictiveEcology/fireSenseUtils@development (>= 0.2.3.9104)", # dataYearBefore(), dataYearElement(before =); defaultFireYears() from 1986
                   "FOR-CAST/fireregimetools@main (>= 0.1.0.9008)",
                   "ggplot2", "methods", "parallel", "purrr", "raster", "sf", "sp", "stats", "utils",
                   "PredictiveEcology/LandR@development (>= 1.2.0.9015)",
@@ -115,6 +115,12 @@ defineModule(sim, list(
                                  "the species, fuel and climate objects itself, as for an unfitted study area.",
                                  "Set it for every fireSense module at once with `.globals = list(heldOutFold = 1L)`;",
                                  "`Init()` stops if `fireSense_spreadFit` has a different value. Any other value is an error.")),
+    defineParameter("fitFileSuffix", "character", "", NA, NA,
+                    paste("Text put after the model tag in the ledger file names, e.g. `\"_boundfix_rep81\"`, so a test run",
+                          "writes and reads (`\"latest\"`) only its own files, never the production ones. `\"\"` (the",
+                          "default) is the production ledger. The same parameter of `fireSense_spreadFit`, `fireSense_ignitionFit` and `fireSense_ELFs`;",
+                          "set it for all with `.globals = list(fitFileSuffix = ...)`; modules that disagree stop",
+                          "(`SpaDES.core::paramCheckOtherMods()`). Ignored when a file name is given.")),
     defineParameter("spreadFitGoogleDriveFolder", "character",
                     fireSenseUtils::spreadFitLedgerFolder(),
                     NA, NA, paste("URL of the Google Drive folder holding the ledger of previous SpreadFit results",
@@ -415,7 +421,8 @@ Init <- function(sim) {
          paste(format(heldOutFold), collapse = ", "))
   sim$spreadFitPreRun <- if (isTRUE(is.na(heldOutFold))) {
     readSpreadFitLedger(Par$spreadFitFilename, Par$spreadFitGoogleDriveFolder,
-                        domain = sa, destinationPath = inputPath(sim))
+                        domain = sa, destinationPath = inputPath(sim),
+                        fitFileSuffix = SpaDES.core::paramCheckOtherMods(sim, "fitFileSuffix"))
   }
   mod$haveSpreadFit <- is(sim$spreadFitPreRun, "sf") || is(sim$spreadFitPreRun, "data.frame")
   if (mod$haveSpreadFit) {
diff --git a/tests/testthat/test-metadata.R b/tests/testthat/test-metadata.R
index 90fe911..49578f7 100644
--- a/tests/testthat/test-metadata.R
+++ b/tests/testthat/test-metadata.R
@@ -99,7 +99,7 @@ test_that("parameters are the expected names", {
            "forestedLCC", "fuelClassCol", "fuelCovariates", "heldOutFold", "igAggFactor",
            "minBufferSize", "minCovariateProp", "nonflammableLCC",
            "nonForestCanBeYoungAge", "scanfiVersion", "sppEquivCol", "spreadFitFilename",
-           "spreadFitGoogleDriveFolder", "spreadIntercept", "targetFuelClasses",
+           "spreadFitGoogleDriveFolder", "fitFileSuffix", "spreadIntercept", "targetFuelClasses",
            "useRasterizedFireForSpread", "whichModulesToPrepare"))
   )
 })
diff --git a/tests/testthat/test-readSpreadFitLedger.R b/tests/testthat/test-readSpreadFitLedger.R
index c65ba10..d873a57 100644
--- a/tests/testthat/test-readSpreadFitLedger.R
+++ b/tests/testthat/test-readSpreadFitLedger.R
@@ -14,7 +14,7 @@ ledger <- function(ids, value) {
 
 test_that("'latest' reads the combined ledger and keeps only this study area's rows", {
   d <- withr::local_tempdir()
-  testthat::local_mocked_bindings(latestSpreadFits = function(cloudFolderID, destinationPath, polygonIDs = NULL)
+  testthat::local_mocked_bindings(latestSpreadFits = function(cloudFolderID, destinationPath, polygonIDs = NULL, suffix = "")
     ledger(c("4.1", "4.3"), c(1, 2)), .package = "fireSenseUtils")
   domain <- sf::st_as_sf(square(4e4))                       # the second polygon, 4.3
   out <- suppressMessages(readSpreadFitLedger("latest", "folder", domain, d))
@@ -26,7 +26,7 @@ test_that("a changed ledger is read again, not returned from an earlier read", {
   d <- withr::local_tempdir()
   domain <- sf::st_as_sf(square(4e4))
   value <- 2
-  testthat::local_mocked_bindings(latestSpreadFits = function(cloudFolderID, destinationPath, polygonIDs = NULL)
+  testthat::local_mocked_bindings(latestSpreadFits = function(cloudFolderID, destinationPath, polygonIDs = NULL, suffix = "")
     ledger(c("4.1", "4.3"), c(1, value)), .package = "fireSenseUtils")
   first <- suppressMessages(readSpreadFitLedger("latest", "folder", domain, d))
   value <- 5                                                 # a newer fit of 4.3 arrives
@@ -48,3 +48,17 @@ test_that("a named file is read from the Drive folder, as before", {
   expect_identical(rec$args$cloudFolderID, "folderURL")
   expect_identical(rec$args$action, "nothing")
 })
+
+test_that("'latest' reads only the files with this run's fitFileSuffix", {
+  d <- withr::local_tempdir()
+  asked <- NULL
+  testthat::local_mocked_bindings(latestSpreadFits = function(cloudFolderID, destinationPath, polygonIDs = NULL, suffix = "") {
+    asked <<- suffix
+    ledger("4.3", 2)
+  }, .package = "fireSenseUtils")
+  domain <- sf::st_as_sf(square(2e4 * 1))
+  suppressMessages(readSpreadFitLedger("latest", "folder", domain, d, fitFileSuffix = "_boundfix_rep81"))
+  expect_identical(asked, "_boundfix_rep81")
+  suppressMessages(readSpreadFitLedger("latest", "folder", domain, d))
+  expect_identical(asked, "")
+})