diff --git a/lib/js/runtime.sx b/lib/js/runtime.sx
index 08d0ab7b..58ad2369 100644
--- a/lib/js/runtime.sx
+++ b/lib/js/runtime.sx
@@ -1624,6 +1624,61 @@
                     (= idx -1)
                     nil
                     (let ((res (list))) (append! res needle) res))))))))
+      ((= name "at")
+        (fn
+          (i)
+          (let
+            ((idx (js-num-to-int i)))
+            (let
+              ((actual (if (< idx 0) (+ (len s) idx) idx)))
+              (if
+                (or (< actual 0) (>= actual (len s)))
+                :js-undefined (char-at s actual))))))
+      ((= name "codePointAt")
+        (fn
+          (i)
+          (let
+            ((idx (js-num-to-int i)))
+            (if
+              (or (< idx 0) (>= idx (len s)))
+              :js-undefined (char-code (char-at s idx))))))
+      ((= name "lastIndexOf")
+        (fn
+          (&rest args)
+          (if
+            (empty? args)
+            -1
+            (let
+              ((needle (js-to-string (nth args 0))))
+              (js-string-last-index-of s needle (- (len s) (len needle)))))))
+      ((= name "localeCompare")
+        (fn
+          (&rest args)
+          (if
+            (empty? args)
+            0
+            (let
+              ((other (js-to-string (nth args 0))))
+              (cond ((< s other) -1) ((> s other) 1) (else 0))))))
+      ((= name "replaceAll")
+        (fn
+          (&rest args)
+          (if
+            (< (len args) 2)
+            s
+            (let
+              ((needle-arg (nth args 0)) (repl (nth args 1)))
+              (let
+                ((needle (if (js-regex? needle-arg) (get needle-arg "source") (js-to-string needle-arg))))
+                (js-string-replace-all
+                  s
+                  needle
+                  (if (js-function? repl) repl (js-to-string repl))))))))
+      ((= name "normalize") (fn (&rest args) s))
+      ((= name "toLocaleLowerCase") (fn (&rest args) (js-lower-case s)))
+      ((= name "toLocaleUpperCase") (fn (&rest args) (js-upper-case s)))
+      ((= name "isWellFormed") (fn () true))
+      ((= name "toWellFormed") (fn () s))
       (else js-undefined))))
 
 (define
@@ -1654,6 +1709,36 @@
       ((js-string-matches? s needle i 0) i)
       (else (js-string-index-of s needle (+ i 1))))))
 
+(define
+  js-string-last-index-of
+  (fn
+    (s needle start)
+    (cond
+      ((< start 0) -1)
+      ((= needle "") start)
+      ((js-string-matches? s needle start 0) start)
+      (else (js-string-last-index-of s needle (- start 1))))))
+
+(define
+  js-string-replace-all
+  (fn
+    (s needle repl)
+    (if
+      (= needle "")
+      s
+      (let
+        ((idx (js-string-index-of s needle 0)))
+        (if
+          (= idx -1)
+          s
+          (str
+            (js-string-slice s 0 idx)
+            (if (js-function? repl) (repl needle) repl)
+            (js-string-replace-all
+              (js-string-slice s (+ idx (len needle)) (len s))
+              needle
+              repl)))))))
+
 (define
   js-string-matches?
   (fn
@@ -1791,6 +1876,18 @@
             ((= key "replace") (js-string-method obj "replace"))
             ((= key "search") (js-string-method obj "search"))
             ((= key "match") (js-string-method obj "match"))
+            ((= key "at") (js-string-method obj "at"))
+            ((= key "codePointAt") (js-string-method obj "codePointAt"))
+            ((= key "lastIndexOf") (js-string-method obj "lastIndexOf"))
+            ((= key "localeCompare") (js-string-method obj "localeCompare"))
+            ((= key "replaceAll") (js-string-method obj "replaceAll"))
+            ((= key "normalize") (js-string-method obj "normalize"))
+            ((= key "toLocaleLowerCase")
+              (js-string-method obj "toLocaleLowerCase"))
+            ((= key "toLocaleUpperCase")
+              (js-string-method obj "toLocaleUpperCase"))
+            ((= key "isWellFormed") (js-string-method obj "isWellFormed"))
+            ((= key "toWellFormed") (js-string-method obj "toWellFormed"))
             (else js-undefined)))
         ((= (type-of obj) "dict")
           (js-dict-get-walk obj (js-to-string key)))
diff --git a/lib/js/test.sh b/lib/js/test.sh
index ae9fc823..9ca2f09e 100755
--- a/lib/js/test.sh
+++ b/lib/js/test.sh
@@ -1213,6 +1213,28 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 3709)
 (eval "(js-eval \"var a=[1,2,3]; a.keys().join(',')\")")
 
+;; ── Phase 11.strmore: more String.prototype methods ─────────
+(epoch 3800)
+(eval "(js-eval \"'hello'.at(0)\")")
+(epoch 3801)
+(eval "(js-eval \"'hello'.at(-1)\")")
+(epoch 3802)
+(eval "(js-eval \"'hello'.codePointAt(0)\")")
+(epoch 3803)
+(eval "(js-eval \"'hello world hello'.lastIndexOf('hello')\")")
+(epoch 3804)
+(eval "(js-eval \"'abc'.localeCompare('abd')\")")
+(epoch 3805)
+(eval "(js-eval \"'abc'.localeCompare('abc')\")")
+(epoch 3806)
+(eval "(js-eval \"'hello hello'.replaceAll('hello', 'bye')\")")
+(epoch 3807)
+(eval "(js-eval \"'a,b,c'.replaceAll(',', '-')\")")
+(epoch 3808)
+(eval "(js-eval \"'hi'.toLocaleUpperCase()\")")
+(epoch 3809)
+(eval "(js-eval \"'HI'.toLocaleLowerCase()\")")
+
 ;; ── Phase 11.arrlike: Array.prototype.* on {length, 0:..., 1:...} ──
 (epoch 3500)
 (eval "(js-eval \"var a = {length: 3, 0: 41, 1: 42, 2: 43}; Array.prototype.slice.call(a).length\")")
@@ -1887,6 +1909,18 @@ check 3707 "arr.toReversed"                '"2,1,3"'
 check 3708 "arr.toSorted"                  '"1,1,3,4,5"'
 check 3709 "arr.keys"                      '"0,1,2"'
 
+# ── Phase 11.strmore: more String.prototype methods ───────────
+check 3800 "'hello'.at(0)"                 '"h"'
+check 3801 "'hello'.at(-1)"                '"o"'
+check 3802 "'hello'.codePointAt(0)"        '104'
+check 3803 "lastIndexOf found"             '12'
+check 3804 "localeCompare less"            '-1'
+check 3805 "localeCompare equal"           '0'
+check 3806 "replaceAll multiple"           '"bye bye"'
+check 3807 "replaceAll commas"             '"a-b-c"'
+check 3808 "toLocaleUpperCase"             '"HI"'
+check 3809 "toLocaleLowerCase"             '"hi"'
+
 # ── Phase 11.arrlike: array-like receivers on Array.prototype ─
 check 3500 "slice.call arrLike length"     '3'
 check 3501 "slice.call arrLike join"       '"41,42,43"'