diff --git a/lib/apl/conformance.sh b/lib/apl/conformance.sh
index 4788fc6e..22df7a5a 100755
--- a/lib/apl/conformance.sh
+++ b/lib/apl/conformance.sh
@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(structural operators dfn tradfn valence programs system)
+SUITES=(structural operators dfn tradfn valence programs system idioms)
 
 OUT_JSON="lib/apl/scoreboard.json"
 OUT_MD="lib/apl/scoreboard.md"
diff --git a/lib/apl/scoreboard.json b/lib/apl/scoreboard.json
index c776d7a3..342aece9 100644
--- a/lib/apl/scoreboard.json
+++ b/lib/apl/scoreboard.json
@@ -6,9 +6,10 @@
     "tradfn": {"pass": 20, "fail": 0},
     "valence": {"pass": 14, "fail": 0},
     "programs": {"pass": 46, "fail": 0},
-    "system": {"pass": 13, "fail": 0}
+    "system": {"pass": 13, "fail": 0},
+    "idioms": {"pass": 34, "fail": 0}
   },
-  "total_pass": 328,
+  "total_pass": 362,
   "total_fail": 0,
-  "total": 328
+  "total": 362
 }
diff --git a/lib/apl/scoreboard.md b/lib/apl/scoreboard.md
index 4f6592d5..60ec34b7 100644
--- a/lib/apl/scoreboard.md
+++ b/lib/apl/scoreboard.md
@@ -11,7 +11,8 @@ _Generated by `lib/apl/conformance.sh`_
 | valence | 14 | 0 | 14 |
 | programs | 46 | 0 | 46 |
 | system | 13 | 0 | 13 |
-| **Total** | **328** | **0** | **328** |
+| idioms | 34 | 0 | 34 |
+| **Total** | **362** | **0** | **362** |
 
 ## Notes
 
diff --git a/lib/apl/test.sh b/lib/apl/test.sh
index fbd0f025..4c48ba02 100755
--- a/lib/apl/test.sh
+++ b/lib/apl/test.sh
@@ -33,6 +33,7 @@ cat > "$TMPFILE" << 'EPOCHS'
 (load "lib/apl/tests/valence.sx")
 (load "lib/apl/tests/programs.sx")
 (load "lib/apl/tests/system.sx")
+(load "lib/apl/tests/idioms.sx")
 (epoch 4)
 (eval "(list apl-test-pass apl-test-fail)")
 EPOCHS
diff --git a/lib/apl/tests/idioms.sx b/lib/apl/tests/idioms.sx
new file mode 100644
index 00000000..e9de393f
--- /dev/null
+++ b/lib/apl/tests/idioms.sx
@@ -0,0 +1,224 @@
+; APL idiom corpus — classic Roger Hui / Phil Last idioms expressed
+; through our runtime primitives.  Each test names the APL one-liner
+; and verifies the equivalent runtime call.
+
+(define mkrv (fn (arr) (get arr :ravel)))
+(define mksh (fn (arr) (get arr :shape)))
+
+; ---------- reductions ----------
+
+(apl-test
+  "+/⍵ — sum"
+  (mkrv (apl-reduce apl-add (make-array (list 5) (list 1 2 3 4 5))))
+  (list 15))
+
+(apl-test
+  "(+/⍵)÷⍴⍵ — mean"
+  (mkrv
+    (apl-div
+      (apl-reduce apl-add (make-array (list 5) (list 1 2 3 4 5)))
+      (apl-scalar 5)))
+  (list 3))
+
+(apl-test
+  "⌈/⍵ — max"
+  (mkrv (apl-reduce apl-max (make-array (list 6) (list 3 1 4 1 5 9))))
+  (list 9))
+
+(apl-test
+  "⌊/⍵ — min"
+  (mkrv (apl-reduce apl-min (make-array (list 6) (list 3 1 4 1 5 9))))
+  (list 1))
+
+(apl-test
+  "(⌈/⍵)-⌊/⍵ — range"
+  (mkrv
+    (apl-sub
+      (apl-reduce apl-max (make-array (list 6) (list 3 1 4 1 5 9)))
+      (apl-reduce apl-min (make-array (list 6) (list 3 1 4 1 5 9)))))
+  (list 8))
+
+(apl-test
+  "×/⍵ — product"
+  (mkrv (apl-reduce apl-mul (make-array (list 4) (list 1 2 3 4))))
+  (list 24))
+
+(apl-test
+  "+\\⍵ — running sum"
+  (mkrv (apl-scan apl-add (make-array (list 5) (list 1 2 3 4 5))))
+  (list 1 3 6 10 15))
+
+; ---------- sort / order ----------
+
+(apl-test
+  "⍵[⍋⍵] — sort ascending"
+  (mkrv (apl-quicksort (make-array (list 5) (list 3 1 4 1 5))))
+  (list 1 1 3 4 5))
+
+(apl-test
+  "⌽⍵ — reverse"
+  (mkrv (apl-reverse (make-array (list 5) (list 1 2 3 4 5))))
+  (list 5 4 3 2 1))
+
+(apl-test
+  "⊃⌽⍵ — last element"
+  (mkrv
+    (apl-disclose (apl-reverse (make-array (list 4) (list 10 20 30 40)))))
+  (list 40))
+
+(apl-test
+  "1↑⍵ — first element"
+  (mkrv
+    (apl-take (apl-scalar 1) (make-array (list 4) (list 10 20 30 40))))
+  (list 10))
+
+(apl-test
+  "1↓⍵ — drop first"
+  (mkrv
+    (apl-drop (apl-scalar 1) (make-array (list 4) (list 10 20 30 40))))
+  (list 20 30 40))
+
+(apl-test
+  "¯1↓⍵ — drop last"
+  (mkrv
+    (apl-drop (apl-scalar -1) (make-array (list 4) (list 10 20 30 40))))
+  (list 10 20 30))
+
+; ---------- counts / membership ----------
+
+(apl-test
+  "≢⍵ — tally"
+  (mkrv (apl-tally (make-array (list 7) (list 9 8 7 6 5 4 3))))
+  (list 7))
+
+(apl-test
+  "+/⍵=v — count occurrences of v"
+  (mkrv
+    (apl-reduce
+      apl-add
+      (apl-eq (make-array (list 7) (list 1 2 3 2 1 3 2)) (apl-scalar 2))))
+  (list 3))
+
+(apl-test
+  "0=N|M — divisibility test"
+  (mkrv (apl-eq (apl-scalar 0) (apl-mod (apl-scalar 3) (apl-scalar 12))))
+  (list 1))
+
+; ---------- shape constructors ----------
+
+(apl-test
+  "N⍴1 — vector of N ones"
+  (mkrv (apl-reshape (apl-scalar 5) (apl-scalar 1)))
+  (list 1 1 1 1 1))
+
+(apl-test
+  "(N N)⍴0 — N×N zero matrix"
+  (mkrv (apl-reshape (make-array (list 2) (list 3 3)) (apl-scalar 0)))
+  (list 0 0 0 0 0 0 0 0 0))
+
+(apl-test
+  "⍳∘.=⍳ — N×N identity matrix"
+  (mkrv
+    (apl-outer apl-eq (apl-iota (apl-scalar 3)) (apl-iota (apl-scalar 3))))
+  (list 1 0 0 0 1 0 0 0 1))
+
+(apl-test
+  "⍳∘.×⍳ — multiplication table"
+  (mkrv
+    (apl-outer apl-mul (apl-iota (apl-scalar 3)) (apl-iota (apl-scalar 3))))
+  (list 1 2 3 2 4 6 3 6 9))
+
+; ---------- numerical idioms ----------
+
+(apl-test
+  "+\\⍳N — triangular numbers"
+  (mkrv (apl-scan apl-add (apl-iota (apl-scalar 5))))
+  (list 1 3 6 10 15))
+
+(apl-test
+  "+/⍳N=N×(N+1)÷2 — sum of 1..N"
+  (mkrv (apl-reduce apl-add (apl-iota (apl-scalar 10))))
+  (list 55))
+
+(apl-test
+  "×/⍳N — factorial via iota"
+  (mkrv (apl-reduce apl-mul (apl-iota (apl-scalar 5))))
+  (list 120))
+
+(apl-test
+  "2|⍵ — parity (1=odd)"
+  (mkrv (apl-mod (apl-scalar 2) (make-array (list 5) (list 1 2 3 4 5))))
+  (list 1 0 1 0 1))
+
+(apl-test
+  "+/2|⍵ — count odd"
+  (mkrv
+    (apl-reduce
+      apl-add
+      (apl-mod (apl-scalar 2) (make-array (list 5) (list 1 2 3 4 5)))))
+  (list 3))
+
+; ---------- boolean idioms ----------
+
+(apl-test
+  "∧/⍵ — all-true"
+  (mkrv (apl-reduce apl-and (make-array (list 4) (list 1 1 1 1))))
+  (list 1))
+
+(apl-test
+  "∧/⍵ — all-true with zero is false"
+  (mkrv (apl-reduce apl-and (make-array (list 4) (list 1 1 0 1))))
+  (list 0))
+
+(apl-test
+  "∨/⍵ — any-true"
+  (mkrv (apl-reduce apl-or (make-array (list 4) (list 0 0 1 0))))
+  (list 1))
+
+(apl-test
+  "∨/⍵ — any-true all zero is false"
+  (mkrv (apl-reduce apl-or (make-array (list 4) (list 0 0 0 0))))
+  (list 0))
+
+; ---------- selection / scaling ----------
+
+(apl-test
+  "⍵×⍵ — square each"
+  (mkrv
+    (apl-mul
+      (make-array (list 4) (list 1 2 3 4))
+      (make-array (list 4) (list 1 2 3 4))))
+  (list 1 4 9 16))
+
+(apl-test
+  "+/⍵×⍵ — sum of squares"
+  (mkrv
+    (apl-reduce
+      apl-add
+      (apl-mul
+        (make-array (list 4) (list 1 2 3 4))
+        (make-array (list 4) (list 1 2 3 4)))))
+  (list 30))
+
+(apl-test
+  "⍵-(+/⍵)÷⍴⍵ — mean-centered"
+  (mkrv
+    (apl-sub
+      (make-array (list 5) (list 2 4 6 8 10))
+      (apl-div
+        (apl-reduce apl-add (make-array (list 5) (list 2 4 6 8 10)))
+        (apl-scalar 5))))
+  (list -4 -2 0 2 4))
+
+; ---------- shape / structure ----------
+
+(apl-test
+  ",⍵ — ravel"
+  (mkrv (apl-ravel (make-array (list 2 3) (list 1 2 3 4 5 6))))
+  (list 1 2 3 4 5 6))
+
+(apl-test
+  "⍴⍴⍵ — rank"
+  (mkrv
+    (apl-shape (apl-shape (make-array (list 2 3) (list 1 2 3 4 5 6)))))
+  (list 2))
diff --git a/plans/apl-on-sx.md b/plans/apl-on-sx.md
index 2dfbba53..30d98d1d 100644
--- a/plans/apl-on-sx.md
+++ b/plans/apl-on-sx.md
@@ -102,7 +102,7 @@ Core mapping:
   - [x] `quicksort.apl` — the classic Roger Hui one-liner
 - [x] System functions: `⎕FMT`, `⎕FR` (float repr), `⎕TS` (timestamp), `⎕IO`, `⎕ML` (migration level — fixed at 1), `⎕←` (print)
 - [x] Drive corpus to 100+ green
-- [ ] Idiom corpus — `lib/apl/tests/idioms.sx` covering classic Roger Hui / Phil Last idioms
+- [x] Idiom corpus — `lib/apl/tests/idioms.sx` covering classic Roger Hui / Phil Last idioms
 
 ## SX primitive baseline
 
@@ -118,6 +118,7 @@ data; format for string templating.
 
 _Newest first._
 
+- 2026-05-07: Phase 6 idiom corpus — lib/apl/tests/idioms.sx; 34 classic idioms (sum, mean, max/min/range, scan, sort, reverse, first/last, take/drop, tally, mod, identity matrix, mult-table, factorial, parity count, all/any, mean-centered, ravel, rank); **all unchecked items in plan now ticked**; 362/362
 - 2026-05-07: Phase 6 system fns + 100+ corpus — apl-quad-{io,ml,fr,ts,fmt,print}; ⎕FMT formats scalar/vector/matrix; ⎕TS returns 7-vector (epoch default); 328 tests >> 100 target; **drive-to-100 ticked**; +13 tests
 - 2026-05-07: Phase 6 quicksort — recursive less/eq/greater partition via apl-compress, deterministic-pivot variant; tests cover empty/single/sorted/reverse/duplicates/negatives; **all 5 classic programs done**; +9 tests; 315/315
 - 2026-05-07: Phase 6 n-queens — permutation enumerate + diagonal-conflict filter; counts q(1..8) = 1,0,0,2,10,4,40,92 (OEIS A000170); apl-permutations + apl-queens; bumped test timeout 60→180s for q(8); +10 tests; 306/306