diff --git a/lib/ocaml/baseline/expected.json b/lib/ocaml/baseline/expected.json
index e338cc68..01db65d7 100644
--- a/lib/ocaml/baseline/expected.json
+++ b/lib/ocaml/baseline/expected.json
@@ -95,6 +95,7 @@
   "palindrome_sum.ml": 49500,
   "paren_depth.ml": 7,
   "partition.ml": 3025,
+  "partition_count.ml": 176,
   "pancake_sort.ml": 910,
   "pascal.ml": 252,
   "peano.ml": 30,
diff --git a/lib/ocaml/baseline/partition_count.ml b/lib/ocaml/baseline/partition_count.ml
new file mode 100644
index 00000000..f91bfca8
--- /dev/null
+++ b/lib/ocaml/baseline/partition_count.ml
@@ -0,0 +1,13 @@
+let partition_count n =
+  let dp = Array.make (n + 1) 0 in
+  dp.(0) <- 1;
+  for k = 1 to n do
+    for i = k to n do
+      dp.(i) <- dp.(i) + dp.(i - k)
+    done
+  done;
+  dp.(n)
+
+;;
+
+partition_count 15
diff --git a/plans/ocaml-on-sx.md b/plans/ocaml-on-sx.md
index ef2b5f7b..b4f6ac7e 100644
--- a/plans/ocaml-on-sx.md
+++ b/plans/ocaml-on-sx.md
@@ -407,6 +407,12 @@ _Newest first._
   binary search tree (`type 'a tree = Leaf | Node of 'a * 'a tree *
   'a tree`) with insert + in-order traversal. Tests parametric ADT,
   recursive match, List.append, List.fold_left.
+- 2026-05-10 Phase 5.1 — partition_count.ml baseline (number of
+  integer partitions of 15 = 176). Classic DP: dp[0] = 1; for each
+  k from 1..n, for each i from k..n, dp[i] += dp[i - k]. O(n²) time,
+  O(n) space. p(15) = 176 partitions of 15. Tests Array.make, array
+  set/get with `.(i)<-` / `.(i)`, nested for-loops, ref deref.
+  135 baseline programs total.
 - 2026-05-10 Phase 5.1 — pythagorean.ml baseline (count primitive
   Pythagorean triples with hypotenuse ≤ 100 = 16). Uses Euclid's
   formula: for coprime m > k of opposite parity, the triple