diff --git a/lib/haskell/map.sx b/lib/haskell/map.sx
index 6d30a316..8f4cb092 100644
--- a/lib/haskell/map.sx
+++ b/lib/haskell/map.sx
@@ -419,3 +419,102 @@
       (fn (k v acc) (cond ((p k v) (hk-map-insert k v acc)) (:else acc)))
       hk-map-empty
       m)))
+
+(define
+  hk-map-adjust
+  (fn
+    (f k m)
+    (cond
+      ((hk-map-empty? m) m)
+      (:else
+        (let
+          ((mk (hk-map-key m)))
+          (cond
+            ((< k mk)
+              (hk-map-node
+                mk
+                (hk-map-val m)
+                (hk-map-adjust f k (hk-map-left m))
+                (hk-map-right m)))
+            ((> k mk)
+              (hk-map-node
+                mk
+                (hk-map-val m)
+                (hk-map-left m)
+                (hk-map-adjust f k (hk-map-right m))))
+            (:else
+              (hk-map-node
+                mk
+                (f (hk-map-val m))
+                (hk-map-left m)
+                (hk-map-right m)))))))))
+
+(define
+  hk-map-insert-with
+  (fn
+    (f k v m)
+    (cond
+      ((hk-map-empty? m) (hk-map-singleton k v))
+      (:else
+        (let
+          ((mk (hk-map-key m)))
+          (cond
+            ((< k mk)
+              (hk-map-balance
+                mk
+                (hk-map-val m)
+                (hk-map-insert-with f k v (hk-map-left m))
+                (hk-map-right m)))
+            ((> k mk)
+              (hk-map-balance
+                mk
+                (hk-map-val m)
+                (hk-map-left m)
+                (hk-map-insert-with f k v (hk-map-right m))))
+            (:else
+              (hk-map-node
+                mk
+                (f v (hk-map-val m))
+                (hk-map-left m)
+                (hk-map-right m)))))))))
+
+(define
+  hk-map-insert-with-key
+  (fn
+    (f k v m)
+    (cond
+      ((hk-map-empty? m) (hk-map-singleton k v))
+      (:else
+        (let
+          ((mk (hk-map-key m)))
+          (cond
+            ((< k mk)
+              (hk-map-balance
+                mk
+                (hk-map-val m)
+                (hk-map-insert-with-key f k v (hk-map-left m))
+                (hk-map-right m)))
+            ((> k mk)
+              (hk-map-balance
+                mk
+                (hk-map-val m)
+                (hk-map-left m)
+                (hk-map-insert-with-key f k v (hk-map-right m))))
+            (:else
+              (hk-map-node
+                mk
+                (f k v (hk-map-val m))
+                (hk-map-left m)
+                (hk-map-right m)))))))))
+
+(define
+  hk-map-alter
+  (fn
+    (f k m)
+    (let
+      ((look (hk-map-lookup k m)))
+      (let
+        ((res (f look)))
+        (cond
+          ((= (first res) "Nothing") (hk-map-delete k m))
+          (:else (hk-map-insert k (nth res 1) m)))))))
diff --git a/plans/haskell-completeness.md b/plans/haskell-completeness.md
index 45385681..cde89129 100644
--- a/plans/haskell-completeness.md
+++ b/plans/haskell-completeness.md
@@ -187,7 +187,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 - [x] Bulk operations: `fromList`, `toList`, `toAscList`, `keys`, `elems`.
 - [x] Combining: `unionWith`, `intersectionWith`, `difference`.
 - [x] Transforming: `foldlWithKey`, `foldrWithKey`, `mapWithKey`, `filterWithKey`.
-- [ ] Updating: `adjust`, `insertWith`, `insertWithKey`, `alter`.
+- [x] Updating: `adjust`, `insertWith`, `insertWithKey`, `alter`.
 - [ ] Module wiring: `import Data.Map` and `import qualified Data.Map as Map`
   resolve to the `map.sx` namespace dict in the eval import handler.
 - [ ] Unit tests in `lib/haskell/tests/map.sx` (≥ 20 tests: empty, singleton,
@@ -304,6 +304,12 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 11 updating (adjust/insertWith/insertWithKey/alter):
+- `adjust` recurses to find the key, replaces value with `f(v)`; no-op when
+  missing. `insertWith` and `insertWithKey` recurse with rebalance and use
+  `f new old` (or `f k new old`) when the key exists. `alter` is the most
+  general, implemented as `lookup → f → either delete or insert`.
+
 **2026-05-07** — Phase 11 transforming (foldlWithKey/foldrWithKey/mapWithKey/filterWithKey):
 - Folds traverse in-order. `foldlWithKey f acc m` walks left → key/val → right
   threading the accumulator, so left-folding `(\acc k v -> acc ++ k ++ v)` over