A second window OVER (PARTITION BY <constant> ORDER BY …) drops the first window's ORDER BY sort

CREATE TABLE t (id BIGINT);

INSERT INTO t VALUES (-3),(-1),(0),(1),(2),(2),(NULL),(7);

-- (1) THE BUG: window A = SUM(41) OVER (ORDER BY id<1 DESC) is corrupted by the presence of window B.

--     Correct (RANGE peers over key id<1: 3 rows key=1 ->123, 4 rows key=0 ->287, 1 NULL ->328):

--         {123,123,123, 287,287,287,287, 328}   <- MySQL returns exactly this.

--     MariaDB actual: wrong AND run-order-dependent, e.g. {41,82,123, 246,246,246, 287, 328}.

SELECT id,

       SUM(41) OVER (ORDER BY id < 1 DESC)                        AS a,

       MAX(id) OVER (PARTITION BY '3' ORDER BY '3' DESC)          AS b

FROM t;

-- Expected column a multiset = {123 x3, 287 x4, 328}; MariaDB gives garbage (frame sizes 1..8).

-- (2) CONTROL -- window A ALONE is correct (and equals MySQL):

SELECT id, SUM(41) OVER (ORDER BY id < 1 DESC) AS a FROM t;

-- a = {123 x3, 287 x4, 328}  ✓

-- (3) CONTROL -- window B PARTITION BY a REAL column (not a constant): window A is correct again:

SELECT id,

       SUM(41) OVER (ORDER BY id < 1 DESC)          AS a,

       MAX(id) OVER (PARTITION BY id ORDER BY '3' DESC) AS b

FROM t;

-- a = {123 x3, 287 x4, 328}  ✓  (the constant partition is the trigger)

-- (4) CONTROL -- window B with NO ORDER BY: window A is correct again:

SELECT id,

       SUM(41) OVER (ORDER BY id < 1 DESC)  AS a,

       MAX(id) OVER (PARTITION BY '3')      AS b

FROM t;

-- a = {123 x3, 287 x4, 328}  ✓  (window B needs both PARTITION-BY-constant AND its own ORDER BY)