diff --git a/lib/haskell/eval.sx b/lib/haskell/eval.sx
index 34b0832d..60de291e 100644
--- a/lib/haskell/eval.sx
+++ b/lib/haskell/eval.sx
@@ -436,6 +436,7 @@
       ((and (list? a) (= (first a) "[]")) b)
       ((and (list? a) (= (first a) ":"))
         (hk-mk-cons (nth a 1) (hk-list-append (nth a 2) b)))
+      ((string? a) (str a b))
       (:else (raise "++: not a list")))))
 
 ;; Eager finite-range spine — handles [from..to] and [from,next..to].
@@ -540,7 +541,7 @@
 ;; the recursive list-building functions.
 (define
   hk-prelude-src
-  "head (x:_) = x\ntail (_:xs) = xs\nfst (a, _) = a\nsnd (_, b) = b\ntake 0 _ = []\ntake _ [] = []\ntake n (x:xs) = x : take (n - 1) xs\ndrop 0 xs = xs\ndrop _ [] = []\ndrop n (_:xs) = drop (n - 1) xs\nrepeat x = x : repeat x\niterate f x = x : iterate f (f x)\nlength [] = 0\nlength (_:xs) = 1 + length xs\nmap _ [] = []\nmap f (x:xs) = f x : map f xs\nfilter _ [] = []\nfilter p (x:xs) = if p x then x : filter p xs else filter p xs\nzipWith _ [] _ = []\nzipWith _ _ [] = []\nzipWith f (x:xs) (y:ys) = f x y : zipWith f xs ys\nfibs = 0 : 1 : zipWith plus fibs (tail fibs)\nplus a b = a + b\nconcat [] = []\nconcat (xs:xss) = xs ++ concat xss\nconcatMap f [] = []\nconcatMap f (x:xs) = f x ++ concatMap f xs\nabs x = if x < 0 then 0 - x else x\nnegate x = 0 - x\nnull [] = True\nnull _ = False\nflip f x y = f y x\nconst x _ = x\ncurry f x y = f (x, y)\nuncurry f p = f (fst p) (snd p)\nfoldr f z [] = z\nfoldr f z (x:xs) = f x (foldr f z xs)\nfoldl f z [] = z\nfoldl f z (x:xs) = foldl f (f z x) xs\nfoldl1 f (x:xs) = foldl f x xs\nfoldr1 f [x] = x\nfoldr1 f (x:xs) = f x (foldr1 f xs)\nzip [] _ = []\nzip _ [] = []\nzip (x:xs) (y:ys) = (x, y) : zip xs ys\nreverse [] = []\nreverse (x:xs) = reverse xs ++ [x]\nelem _ [] = False\nelem x (y:ys) = if x == y then True else elem x ys\nnotElem x xs = not (elem x xs)\nany _ [] = False\nany f (x:xs) = if f x then True else any f xs\nall _ [] = True\nall f (x:xs) = if f x then all f xs else False\nand [] = True\nand (x:xs) = if x then and xs else False\nor [] = False\nor (x:xs) = if x then True else or xs\nsum [] = 0\nsum (x:xs) = x + sum xs\nproduct [] = 1\nproduct (x:xs) = x * product xs\nmaximum [x] = x\nmaximum (x:xs) = let m = maximum xs in if x >= m then x else m\nminimum [x] = x\nminimum (x:xs) = let m = minimum xs in if x <= m then x else m\ncompare x y = if x < y then LT else if x == y then EQ else GT\nmin x y = if x <= y then x else y\nmax x y = if x >= y then x else y\nsignum x = if x < 0 then negate 1 else if x == 0 then 0 else 1\nfromIntegral x = x\nfromInteger x = x\ntoInteger x = x\nceiling x = x\nfloor x = x\nround x = x\ntruncate x = x\nlookup _ [] = Nothing\nlookup k ((k2,v):rest) = if k == k2 then Just v else lookup k rest\nmaybe d _ Nothing = d\nmaybe _ f (Just x) = f x\neither f _ (Left x) = f x\neither _ g (Right y) = g y\nmapMaybe _ [] = []\nmapMaybe f (x:xs) = case f x of { Nothing -> mapMaybe f xs; Just y -> y : mapMaybe f xs }\nfmap = map\npure = return\nwhen b m = if b then m else return ()\nunless b m = if b then return () else m\nmapM_ _ [] = return ()\nmapM_ f (x:xs) = f x >> mapM_ f xs\nsequence_ [] = return ()\nsequence_ (m:ms) = m >> sequence_ ms\ninteract f = getContents >>= \\s -> putStr (f s)\n")
+  "head (x:_) = x\ntail (_:xs) = xs\nfst (a, _) = a\nsnd (_, b) = b\ntake 0 _ = []\ntake _ [] = []\ntake n (x:xs) = x : take (n - 1) xs\ndrop 0 xs = xs\ndrop _ [] = []\ndrop n (_:xs) = drop (n - 1) xs\nrepeat x = x : repeat x\niterate f x = x : iterate f (f x)\nlength [] = 0\nlength (_:xs) = 1 + length xs\nmap _ [] = []\nmap f (x:xs) = f x : map f xs\nfilter _ [] = []\nfilter p (x:xs) = if p x then x : filter p xs else filter p xs\nzipWith _ [] _ = []\nzipWith _ _ [] = []\nzipWith f (x:xs) (y:ys) = f x y : zipWith f xs ys\nfibs = 0 : 1 : zipWith plus fibs (tail fibs)\nplus a b = a + b\nconcat [] = []\nconcat (xs:xss) = xs ++ concat xss\nconcatMap f [] = []\nconcatMap f (x:xs) = f x ++ concatMap f xs\nabs x = if x < 0 then 0 - x else x\nnegate x = 0 - x\nnull [] = True\nnull _ = False\nflip f x y = f y x\nconst x _ = x\nid x = x\ncurry f x y = f (x, y)\nuncurry f p = f (fst p) (snd p)\nfoldr f z [] = z\nfoldr f z (x:xs) = f x (foldr f z xs)\nfoldl f z [] = z\nfoldl f z (x:xs) = foldl f (f z x) xs\nfoldl1 f (x:xs) = foldl f x xs\nfoldr1 f [x] = x\nfoldr1 f (x:xs) = f x (foldr1 f xs)\nzip [] _ = []\nzip _ [] = []\nzip (x:xs) (y:ys) = (x, y) : zip xs ys\nreverse [] = []\nreverse (x:xs) = reverse xs ++ [x]\nelem _ [] = False\nelem x (y:ys) = if x == y then True else elem x ys\nnotElem x xs = not (elem x xs)\nany _ [] = False\nany f (x:xs) = if f x then True else any f xs\nall _ [] = True\nall f (x:xs) = if f x then all f xs else False\nand [] = True\nand (x:xs) = if x then and xs else False\nor [] = False\nor (x:xs) = if x then True else or xs\nsum [] = 0\nsum (x:xs) = x + sum xs\nproduct [] = 1\nproduct (x:xs) = x * product xs\nmaximum [x] = x\nmaximum (x:xs) = let m = maximum xs in if x >= m then x else m\nminimum [x] = x\nminimum (x:xs) = let m = minimum xs in if x <= m then x else m\ncompare x y = if x < y then LT else if x == y then EQ else GT\nmin x y = if x <= y then x else y\nmax x y = if x >= y then x else y\nsignum x = if x < 0 then negate 1 else if x == 0 then 0 else 1\nfromIntegral x = x\nfromInteger x = x\ntoInteger x = x\nceiling x = x\nfloor x = x\nround x = x\ntruncate x = x\nlookup _ [] = Nothing\nlookup k ((k2,v):rest) = if k == k2 then Just v else lookup k rest\nmaybe d _ Nothing = d\nmaybe _ f (Just x) = f x\neither f _ (Left x) = f x\neither _ g (Right y) = g y\nmapMaybe _ [] = []\nmapMaybe f (x:xs) = case f x of { Nothing -> mapMaybe f xs; Just y -> y : mapMaybe f xs }\nfmap = map\npure = return\nwhen b m = if b then m else return ()\nunless b m = if b then return () else m\nmapM_ _ [] = return ()\nmapM_ f (x:xs) = f x >> mapM_ f xs\nsequence_ [] = return ()\nsequence_ (m:ms) = m >> sequence_ ms\ninteractApply f s = putStr (f s)\ninteract f = getContents >>= interactApply f\nnub [] = []\nnub (x:xs) = x : nub (filter notEqX xs)\n  where notEqX y = y /= x\nsort [] = []\nsort (x:xs) = sort (filter ltX xs) ++ [x] ++ sort (filter geX xs)\n  where ltX y = y < x\n        geX y = y >= x\nsortBy _ [] = []\nsortBy cmp (x:xs) = sortBy cmp smaller ++ [x] ++ sortBy cmp bigger\n  where smaller = filter ltCmp xs\n        bigger  = filter geCmp xs\n        ltCmp y = cmp y x /= GT\n        geCmp y = cmp y x == GT\nsortOnCmpFst p1 p2 = compare (fst p1) (fst p2)\nsortOn f xs = map snd (sortBy sortOnCmpFst (zip (map f xs) xs))\nsplitAt 0 xs = ([], xs)\nsplitAt _ [] = ([], [])\nsplitAt n (x:xs) = (x : a, b) where (a, b) = splitAt (n - 1) xs\nspan _ [] = ([], [])\nspan p (x:xs) = if p x then (x : a, b) else ([], x : xs) where (a, b) = span p xs\nbreak p xs = span notP xs\n  where notP y = not (p y)\npartition _ [] = ([], [])\npartition p (x:xs) = if p x then (x : a, b) else (a, x : b) where (a, b) = partition p xs\nunzip [] = ([], [])\nunzip ((a, b) : rest) = (a : as, b : bs) where (as, bs) = unzip rest\ntails [] = [[]]\ntails (x:xs) = (x:xs) : tails xs\ninits [] = [[]]\ninits (x:xs) = [] : map (x:) (inits xs)\nisPrefixOf [] _ = True\nisPrefixOf _ [] = False\nisPrefixOf (x:xs) (y:ys) = if x == y then isPrefixOf xs ys else False\nisSuffixOf xs ys = isPrefixOf (reverse xs) (reverse ys)\nisInfixOf [] _ = True\nisInfixOf _ [] = False\nisInfixOf xs ys = if isPrefixOf xs ys then True else isInfixOf xs (tail ys)\nintercalate _ [] = []\nintercalate _ [x] = x\nintercalate sep (x:xs) = x ++ sep ++ intercalate sep xs\nintersperse _ [] = []\nintersperse _ [x] = [x]\nintersperse sep (x:xs) = x : sep : intersperse sep xs\nunwords [] = \"\"\nunwords [w] = w\nunwords (w:ws) = w ++ \" \" ++ unwords ws\nunlines [] = \"\"\nunlines (l:ls) = l ++ \"\\n\" ++ unlines ls\n")
 
 (define
   hk-load-into!
@@ -791,7 +792,161 @@
                 (dict-set! hk-vfs (hk-force path) (hk-force contents))
                 (list "IO" (list "Tuple"))))
             2))
-        env))))
+        (let
+          ((--sx-to-hk-- (fn (lst) (if (empty? lst) (list "[]") (list ":" (first lst) (--sx-to-hk-- (rest lst))))))
+            (--words--
+              (fn
+                (s n i start acc)
+                (if
+                  (>= i n)
+                  (let
+                    ((w (substr s start (- n start))))
+                    (reverse (if (= (len w) 0) acc (cons w acc))))
+                  (let
+                    ((c (char-code (nth s i))))
+                    (if
+                      (or (= c 32) (= c 9) (= c 10) (= c 13))
+                      (if
+                        (= i start)
+                        (--words-- s n (+ i 1) (+ i 1) acc)
+                        (--words--
+                          s
+                          n
+                          (+ i 1)
+                          (+ i 1)
+                          (cons (substr s start (- i start)) acc)))
+                      (--words-- s n (+ i 1) start acc))))))
+            (--lines--
+              (fn
+                (s n i start acc)
+                (if
+                  (>= i n)
+                  (if
+                    (= start n)
+                    (reverse acc)
+                    (reverse (cons (substr s start (- n start)) acc)))
+                  (let
+                    ((c (char-code (nth s i))))
+                    (if
+                      (= c 10)
+                      (--lines--
+                        s
+                        n
+                        (+ i 1)
+                        (+ i 1)
+                        (cons (substr s start (- i start)) acc))
+                      (--lines-- s n (+ i 1) start acc)))))))
+          (dict-set!
+            env
+            "ord"
+            (hk-mk-builtin "ord" (fn (c) (char-code (hk-force c))) 1))
+          (dict-set!
+            env
+            "isAlpha"
+            (hk-mk-builtin
+              "isAlpha"
+              (fn
+                (c)
+                (let
+                  ((code (char-code (hk-force c))))
+                  (hk-of-bool
+                    (or
+                      (and (>= code 65) (<= code 90))
+                      (and (>= code 97) (<= code 122))))))
+              1))
+          (dict-set!
+            env
+            "isAlphaNum"
+            (hk-mk-builtin
+              "isAlphaNum"
+              (fn
+                (c)
+                (let
+                  ((code (char-code (hk-force c))))
+                  (hk-of-bool
+                    (or
+                      (and (>= code 65) (<= code 90))
+                      (and (>= code 97) (<= code 122))
+                      (and (>= code 48) (<= code 57))))))
+              1))
+          (dict-set!
+            env
+            "isDigit"
+            (hk-mk-builtin
+              "isDigit"
+              (fn
+                (c)
+                (let
+                  ((code (char-code (hk-force c))))
+                  (hk-of-bool (and (>= code 48) (<= code 57)))))
+              1))
+          (dict-set!
+            env
+            "isSpace"
+            (hk-mk-builtin
+              "isSpace"
+              (fn
+                (c)
+                (let
+                  ((code (char-code (hk-force c))))
+                  (hk-of-bool
+                    (or (= code 32) (= code 9) (= code 10) (= code 13)))))
+              1))
+          (dict-set!
+            env
+            "isUpper"
+            (hk-mk-builtin
+              "isUpper"
+              (fn
+                (c)
+                (let
+                  ((code (char-code (hk-force c))))
+                  (hk-of-bool (and (>= code 65) (<= code 90)))))
+              1))
+          (dict-set!
+            env
+            "isLower"
+            (hk-mk-builtin
+              "isLower"
+              (fn
+                (c)
+                (let
+                  ((code (char-code (hk-force c))))
+                  (hk-of-bool (and (>= code 97) (<= code 122)))))
+              1))
+          (dict-set!
+            env
+            "digitToInt"
+            (hk-mk-builtin
+              "digitToInt"
+              (fn (c) (- (char-code (hk-force c)) 48))
+              1))
+          (dict-set!
+            env
+            "words"
+            (hk-mk-builtin
+              "words"
+              (fn
+                (s)
+                (let
+                  ((str (hk-force s)))
+                  (--sx-to-hk-- (--words-- str (len str) 0 0 (list)))))
+              1))
+          (dict-set!
+            env
+            "lines"
+            (hk-mk-builtin
+              "lines"
+              (fn
+                (s)
+                (let
+                  ((str (hk-force s)))
+                  (if
+                    (= (len str) 0)
+                    (list "[]")
+                    (--sx-to-hk-- (--lines-- str (len str) 0 0 (list))))))
+              1))
+          env)))))
 
 ;; Eagerly build the Prelude env once at load time; each call to
 ;; hk-eval-expr-source copies it instead of re-parsing the whole Prelude.
diff --git a/lib/haskell/tests/prelude-extra.sx b/lib/haskell/tests/prelude-extra.sx
new file mode 100644
index 00000000..82a18676
--- /dev/null
+++ b/lib/haskell/tests/prelude-extra.sx
@@ -0,0 +1,234 @@
+;; prelude-extra.sx — tests for Phase 6 prelude additions:
+;; ord/isAlpha/isDigit/isSpace/isUpper/isLower/isAlphaNum/digitToInt
+;; words/lines/unwords/unlines/sort/nub/splitAt/span/break
+;; partition/intercalate/intersperse/isPrefixOf/isSuffixOf/isInfixOf
+
+;; ── ord ──────────────────────────────────────────────────────
+(hk-test "ord 'A'" (hk-eval-expr-source "ord 'A'") 65)
+(hk-test "ord 'a'" (hk-eval-expr-source "ord 'a'") 97)
+(hk-test "ord '0'" (hk-eval-expr-source "ord '0'") 48)
+
+;; ── isAlpha / isDigit / isSpace / isUpper / isLower ──────────
+(hk-test
+  "isAlpha 'a' True"
+  (hk-eval-expr-source "isAlpha 'a'")
+  (list "True"))
+(hk-test
+  "isAlpha 'Z' True"
+  (hk-eval-expr-source "isAlpha 'Z'")
+  (list "True"))
+(hk-test
+  "isAlpha '3' False"
+  (hk-eval-expr-source "isAlpha '3'")
+  (list "False"))
+(hk-test
+  "isDigit '5' True"
+  (hk-eval-expr-source "isDigit '5'")
+  (list "True"))
+(hk-test
+  "isDigit 'a' False"
+  (hk-eval-expr-source "isDigit 'a'")
+  (list "False"))
+(hk-test
+  "isSpace ' ' True"
+  (hk-eval-expr-source "isSpace ' '")
+  (list "True"))
+(hk-test
+  "isSpace 'x' False"
+  (hk-eval-expr-source "isSpace 'x'")
+  (list "False"))
+(hk-test
+  "isUpper 'A' True"
+  (hk-eval-expr-source "isUpper 'A'")
+  (list "True"))
+(hk-test
+  "isUpper 'a' False"
+  (hk-eval-expr-source "isUpper 'a'")
+  (list "False"))
+(hk-test
+  "isLower 'z' True"
+  (hk-eval-expr-source "isLower 'z'")
+  (list "True"))
+(hk-test
+  "isLower 'Z' False"
+  (hk-eval-expr-source "isLower 'Z'")
+  (list "False"))
+(hk-test
+  "isAlphaNum '3' True"
+  (hk-eval-expr-source "isAlphaNum '3'")
+  (list "True"))
+(hk-test
+  "isAlphaNum 'b' True"
+  (hk-eval-expr-source "isAlphaNum 'b'")
+  (list "True"))
+(hk-test
+  "isAlphaNum '!' False"
+  (hk-eval-expr-source "isAlphaNum '!'")
+  (list "False"))
+
+;; ── digitToInt ───────────────────────────────────────────────
+(hk-test "digitToInt '0'" (hk-eval-expr-source "digitToInt '0'") 0)
+(hk-test "digitToInt '7'" (hk-eval-expr-source "digitToInt '7'") 7)
+(hk-test "digitToInt '9'" (hk-eval-expr-source "digitToInt '9'") 9)
+
+;; ── words ────────────────────────────────────────────────────
+(hk-test
+  "words single"
+  (hk-deep-force (hk-eval-expr-source "words \"hello\""))
+  (list ":" "hello" (list "[]")))
+
+(hk-test
+  "words two"
+  (hk-deep-force (hk-eval-expr-source "words \"hello world\""))
+  (list ":" "hello" (list ":" "world" (list "[]"))))
+
+(hk-test
+  "words leading/trailing spaces"
+  (hk-deep-force (hk-eval-expr-source "words \"  foo  bar  \""))
+  (list ":" "foo" (list ":" "bar" (list "[]"))))
+
+(hk-test
+  "words empty string"
+  (hk-deep-force (hk-eval-expr-source "words \"\""))
+  (list "[]"))
+
+;; ── lines ────────────────────────────────────────────────────
+(hk-test
+  "lines single no newline"
+  (hk-deep-force (hk-eval-expr-source "lines \"hello\""))
+  (list ":" "hello" (list "[]")))
+
+(hk-test
+  "lines two lines"
+  (hk-deep-force (hk-eval-expr-source "lines \"a\\nb\""))
+  (list ":" "a" (list ":" "b" (list "[]"))))
+
+(hk-test
+  "lines trailing newline"
+  (hk-deep-force (hk-eval-expr-source "lines \"a\\n\""))
+  (list ":" "a" (list "[]")))
+
+(hk-test
+  "lines empty string"
+  (hk-deep-force (hk-eval-expr-source "lines \"\""))
+  (list "[]"))
+
+;; ── unwords / unlines ────────────────────────────────────────
+(hk-test
+  "unwords two"
+  (hk-eval-expr-source "unwords [\"hello\", \"world\"]")
+  "hello world")
+
+(hk-test "unwords empty" (hk-eval-expr-source "unwords []") "")
+
+(hk-test "unlines two" (hk-eval-expr-source "unlines [\"a\", \"b\"]") "a\nb\n")
+
+;; ── sort / nub ───────────────────────────────────────────────
+(hk-test
+  "sort ascending"
+  (hk-deep-force (hk-eval-expr-source "sort [3,1,2]"))
+  (list ":" 1 (list ":" 2 (list ":" 3 (list "[]")))))
+
+(hk-test
+  "sort already sorted"
+  (hk-deep-force (hk-eval-expr-source "sort [1,2,3]"))
+  (list ":" 1 (list ":" 2 (list ":" 3 (list "[]")))))
+
+(hk-test
+  "nub removes duplicates"
+  (hk-deep-force (hk-eval-expr-source "nub [1,2,1,3,2]"))
+  (list ":" 1 (list ":" 2 (list ":" 3 (list "[]")))))
+
+(hk-test
+  "nub no duplicates unchanged"
+  (hk-deep-force (hk-eval-expr-source "nub [1,2,3]"))
+  (list ":" 1 (list ":" 2 (list ":" 3 (list "[]")))))
+
+;; ── splitAt ──────────────────────────────────────────────────
+(hk-test
+  "splitAt 2"
+  (hk-deep-force (hk-eval-expr-source "splitAt 2 [1,2,3,4]"))
+  (list
+    "Tuple"
+    (list ":" 1 (list ":" 2 (list "[]")))
+    (list ":" 3 (list ":" 4 (list "[]")))))
+
+(hk-test
+  "splitAt 0"
+  (hk-deep-force (hk-eval-expr-source "splitAt 0 [1,2,3]"))
+  (list
+    "Tuple"
+    (list "[]")
+    (list ":" 1 (list ":" 2 (list ":" 3 (list "[]"))))))
+
+;; ── span / break ─────────────────────────────────────────────
+(hk-test
+  "span digits"
+  (hk-deep-force (hk-eval-expr-source "span (\\x -> x < 3) [1,2,3,4]"))
+  (list
+    "Tuple"
+    (list ":" 1 (list ":" 2 (list "[]")))
+    (list ":" 3 (list ":" 4 (list "[]")))))
+
+(hk-test
+  "break digits"
+  (hk-deep-force (hk-eval-expr-source "break (\\x -> x >= 3) [1,2,3,4]"))
+  (list
+    "Tuple"
+    (list ":" 1 (list ":" 2 (list "[]")))
+    (list ":" 3 (list ":" 4 (list "[]")))))
+
+;; ── partition ────────────────────────────────────────────────
+(hk-test
+  "partition even/odd"
+  (hk-deep-force
+    (hk-eval-expr-source "partition (\\x -> x `mod` 2 == 0) [1,2,3,4,5]"))
+  (list
+    "Tuple"
+    (list ":" 2 (list ":" 4 (list "[]")))
+    (list ":" 1 (list ":" 3 (list ":" 5 (list "[]"))))))
+
+;; ── intercalate / intersperse ────────────────────────────────
+(hk-test
+  "intercalate"
+  (hk-eval-expr-source "intercalate \", \" [\"a\", \"b\", \"c\"]")
+  "a, b, c")
+
+(hk-test
+  "intersperse"
+  (hk-deep-force (hk-eval-expr-source "intersperse 0 [1,2,3]"))
+  (list
+    ":"
+    1
+    (list
+      ":"
+      0
+      (list ":" 2 (list ":" 0 (list ":" 3 (list "[]")))))))
+
+;; ── isPrefixOf / isSuffixOf / isInfixOf ──────────────────────
+(hk-test
+  "isPrefixOf True"
+  (hk-deep-force (hk-eval-expr-source "isPrefixOf [1,2] [1,2,3]"))
+  (list "True"))
+
+(hk-test
+  "isPrefixOf False"
+  (hk-deep-force (hk-eval-expr-source "isPrefixOf [2,3] [1,2,3]"))
+  (list "False"))
+
+(hk-test
+  "isSuffixOf True"
+  (hk-deep-force (hk-eval-expr-source "isSuffixOf [2,3] [1,2,3]"))
+  (list "True"))
+
+(hk-test
+  "isInfixOf True"
+  (hk-deep-force (hk-eval-expr-source "isInfixOf [2,3] [1,2,3,4]"))
+  (list "True"))
+
+(hk-test
+  "isInfixOf False"
+  (hk-deep-force (hk-eval-expr-source "isInfixOf [5,6] [1,2,3,4]"))
+  (list "False"))
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}