diff --git a/init.lua b/init.lua
index 64d48e9..48673b5 100644
--- a/init.lua
+++ b/init.lua
@@ -76,9 +76,9 @@ local function shallow_copy(t)
     return out
 end
 
--- Locale-Resolver: akzeptiert entity_handle (bw-compat) ODER table
--- {sources={...}, sink=...}. Returns immer Form-2 mit validierten
--- Feldern. Loud-Error bei kaputter Form-2.
+-- Locale resolver: accepts entity_handle (bw-compat) OR table
+-- {sources={...}, sink=...}. Always returns Form-2 with validated
+-- fields. Loud-error on malformed Form-2.
 local function resolve_locale(locale, fn_name)
     -- Form 2: explicit table
     if type(locale) == "table" and locale.sources ~= nil then
@@ -92,7 +92,27 @@ local function resolve_locale(locale, fn_name)
                 "crafting.%s: locale.sink must not be nil",
                 fn_name), 3)
         end
-        return locale
+        -- De-duplicate sources by identity, preserving first-occurrence order.
+        -- A caller building sources programmatically (e.g. {workbench_buffer,
+        -- player_backpack} where both alias the same entity) should not have
+        -- count_by_template double-count nor craft silent-fail.
+        local seen, deduped = {}, {}
+        for _, s in ipairs(locale.sources) do
+            if not seen[s] then
+                seen[s] = true
+                deduped[#deduped + 1] = s
+            end
+        end
+        return { sources = deduped, sink = locale.sink }
+    end
+    -- Form 2 malformed: a table that's not Form-2 (no sources key) is almost
+    -- certainly a caller typo. Loud-error explicitly instead of silently
+    -- falling through to the Form-1 bw-compat path (which would then crash
+    -- deep inside inventory-list with an opaque error).
+    if type(locale) == "table" then
+        error(string.format(
+            "crafting.%s: locale table must contain 'sources' field",
+            fn_name), 3)
     end
     -- Form 1 (bw-compat): bare entity_handle
     if locale == nil then