fix(switch): write nx-asset-probe.log on every NX Play

Capture resolve paths and newImage open results for Yellow/Blue art
triage without enabling switch-debug.txt.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/switch-development.md

@@ -432,6 +432,8 @@ Community mod zip install smoke (MODS inbox + Play): NXMOD-12 in [switch-hardwar
 
 **Opt-in diagnostics:** create an empty `switch-debug.txt` in the save directory; events flush to `switch.log` at ≤1 Hz with build identity (no ROM/save bytes).
 
+**NX asset probe (always on Play):** every Switch Play writes `nx-asset-probe.log` in the save directory (`pokemon-love2d/`). It lists whether `assets/generated/…` vs `yellow|blue/assets/generated/…` exist, what `Assets.resolve` returns, and whether `newImage` / `newImageData` open — for Yellow/Blue blank-sprite triage. No ROM bytes.
+
 **Hardware re-test:** T16 **pass** @ `2699c9a` (naming A=confirm / B=cancel). T19 **pass** (quit/reopen, suspend×10, reboot) — operator 2026-08-01.
 
 **Suspend/resume audio:** after resume, chip music is stopped to avoid duplicate streams; confirm on hardware during P0-09/10 (T19).

main.lua

@@ -188,6 +188,11 @@ local function bootGame(version)
   -- (Blue/Yellow caches live under blue/ / yellow/).
   CacheFs.prefix = GameVersion.cachePrefix()
   CacheFs.mountVersion(GameVersion.get())
+  -- NX: always write nx-asset-probe.log so Yellow/Blue art failures are
+  -- diagnosable from the SD without enabling switch-debug.txt.
+  pcall(function()
+    require("src.debug.SwitchDiagnostics").probeAssets(GameVersion.get())
+  end)
   if love.window and love.window.setTitle then
     local Version = require("src.core.Version")
     love.window.setTitle(Version.title(

src/debug/SwitchDiagnostics.lua

@@ -171,4 +171,91 @@ function SwitchDiagnostics.maybeFlush(force, now)
   filesystem.write(LOG_FILE, table.concat(lines, "\n") .. "\n")
 end
 
+-- One-shot NX asset probe written on every Play. No ROM/save bytes — only
+-- paths, sizes, resolve results, and whether newImage/newImageData open.
+-- Pull sdmc:.../pokemon-love2d/nx-asset-probe.log after a Yellow boot.
+local PROBE_LOG = "nx-asset-probe.log"
+
+local function probeInfo(filesystem, path)
+  local info = filesystem.getInfo(path)
+  if not info then return "missing" end
+  local size = info.size
+  if size == nil then
+    local bytes = filesystem.read(path)
+    size = type(bytes) == "string" and #bytes or -1
+  end
+  return ("type=%s size=%s"):format(tostring(info.type), tostring(size))
+end
+
+local function probeOpen(kind, path)
+  if kind == "image" then
+    local ok, err = pcall(love.graphics.newImage, path)
+    return ok and "ok" or ("FAIL " .. tostring(err):gsub("%s+", " "):sub(1, 160))
+  end
+  if not (love.image and love.image.newImageData) then return "skip-no-imageData" end
+  local ok, err = pcall(love.image.newImageData, path)
+  return ok and "ok" or ("FAIL " .. tostring(err):gsub("%s+", " "):sub(1, 160))
+end
+
+function SwitchDiagnostics.probeAssets(version)
+  local Platform = require("src.core.Platform")
+  if not Platform.isNX() then return end
+  local filesystem = fs()
+  if not filesystem then return end
+
+  local GameVersion = require("src.core.GameVersion")
+  local Assets = require("src.render.Assets")
+  local prefix = GameVersion.cachePrefix(version or GameVersion.get())
+  local lines = {
+    SwitchDiagnostics.identityOverlay(),
+    "probe=nx-asset",
+    "version=" .. tostring(version or GameVersion.get()),
+    "cachePrefix=" .. tostring(prefix),
+    "isNX=" .. tostring(Platform.isNX()),
+    "saveDir=" .. tostring(filesystem.getSaveDirectory and filesystem.getSaveDirectory() or "?"),
+  }
+
+  local samples = {
+    "assets/generated/fonts/font.png",
+    "assets/generated/tilesets/reds_house.png",
+    "assets/generated/sprites/red.png",
+    "assets/generated/sprites/monster.png",
+  }
+  for _, path in ipairs(samples) do
+    local versioned = prefix ~= "" and (prefix .. path) or path
+    local resolved = Assets.resolve(path)
+    lines[#lines + 1] = ("--- %s"):format(path)
+    lines[#lines + 1] = "unprefixed=" .. probeInfo(filesystem, path)
+    if prefix ~= "" then
+      lines[#lines + 1] = "versioned=" .. probeInfo(filesystem, versioned)
+    end
+    lines[#lines + 1] = "resolve=" .. tostring(resolved)
+    lines[#lines + 1] = "newImage=" .. probeOpen("image", resolved)
+    lines[#lines + 1] = "newImageData=" .. probeOpen("imageData", resolved)
+    if prefix ~= "" and resolved ~= versioned then
+      lines[#lines + 1] = "newImage_versioned=" .. probeOpen("image", versioned)
+      lines[#lines + 1] = "newImageData_versioned=" .. probeOpen("imageData", versioned)
+    end
+  end
+
+  -- Shallow listing so we can see if the extract tree exists at all.
+  local roots = { "yellow", "blue", "assets", "yellow/assets/generated",
+    "yellow/assets/generated/sprites", "blue/assets/generated/sprites" }
+  for _, dir in ipairs(roots) do
+    local info = filesystem.getInfo(dir)
+    if info and info.type == "directory" and filesystem.getDirectoryItems then
+      local items = filesystem.getDirectoryItems(dir) or {}
+      local n = math.min(8, #items)
+      local head = {}
+      for i = 1, n do head[i] = items[i] end
+      lines[#lines + 1] = ("list %s count=%d head=%s"):format(
+        dir, #items, table.concat(head, ","))
+    else
+      lines[#lines + 1] = ("list %s %s"):format(dir, info and info.type or "missing")
+    end
+  end
+
+  filesystem.write(PROBE_LOG, table.concat(lines, "\n") .. "\n")
+end
+
 return SwitchDiagnostics

tests/engine/switch_diagnostics_test.lua

@@ -70,4 +70,39 @@ check(errLog:find("missing module", 1, true) ~= nil,
 check(errLog:find("Import again", 1, true) ~= nil,
   "lua-error.log preserves lines after newline")
 
+-- NX asset probe: always writes nx-asset-probe.log on Play (Switch only).
+local Platform = require("src.core.Platform")
+local GameVersion = require("src.core.GameVersion")
+local savedSystem = love.system
+love.system = { getOS = function() return "NX" end }
+Platform._resetForTests()
+GameVersion.set("yellow")
+love.filesystem.write("yellow/assets/generated/fonts/font.png", "font-bytes")
+love.filesystem.write("yellow/assets/generated/tilesets/reds_house.png", "house-bytes")
+love.filesystem.write("yellow/assets/generated/sprites/red.png", "red-bytes")
+SwitchDiagnostics.probeAssets("yellow")
+local probe = love.filesystem.read("nx-asset-probe.log") or ""
+check(probe:find("probe=nx-asset", 1, true) ~= nil, "probe log writes header")
+check(probe:find("cachePrefix=yellow/", 1, true) ~= nil, "probe records yellow prefix")
+check(probe:find("resolve=yellow/assets/generated/fonts/font.png", 1, true) ~= nil
+  or probe:find("versioned=type=file", 1, true) ~= nil,
+  "probe records versioned font path visibility")
+check(not probe:find(string.char(0xEA, 0x9B), 1, true),
+  "probe log contains no ROM-like binary")
+
+love.system = { getOS = function() return "OS X" end }
+Platform._resetForTests()
+love.filesystem.remove("nx-asset-probe.log")
+SwitchDiagnostics.probeAssets("yellow")
+check(love.filesystem.read("nx-asset-probe.log") == nil,
+  "probe is a no-op off NX")
+
+love.system = savedSystem
+Platform._resetForTests()
+GameVersion.set("red")
+love.filesystem.remove("nx-asset-probe.log")
+love.filesystem.remove("yellow/assets/generated/fonts/font.png")
+love.filesystem.remove("yellow/assets/generated/tilesets/reds_house.png")
+love.filesystem.remove("yellow/assets/generated/sprites/red.png")
+
 T.finish()