From 3125e6ce064c1b8f4eab1df4a214f3b495cc47ea Mon Sep 17 00:00:00 2001
From: Nic Crane <thisisnic@gmail.com>
Date: Sat, 12 Sep 2026 07:30:38 -0400
Subject: [PATCH 1/5] Add failing test

---
 r/tests/testthat/test-dplyr-summarize.R | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/r/tests/testthat/test-dplyr-summarize.R b/r/tests/testthat/test-dplyr-summarize.R
index bb18c01666ed..2cd68528ac5f 100644
--- a/r/tests/testthat/test-dplyr-summarize.R
+++ b/r/tests/testthat/test-dplyr-summarize.R
@@ -1336,3 +1336,13 @@ test_that(".by argument", {
     "Can't supply `\\.by` when `\\.data` is grouped data"
   )
 })
+
+test_that("summarize() after arrange() (GH-45373)", {
+  compare_dplyr_binding(
+    .input |>
+      arrange(int) |>
+      summarize(min_int = min(int, na.rm = TRUE)) |>
+      collect(),
+    tbl
+  )
+})

From 0464c683f441aac8fc5ed6019f8665957d4f24ce Mon Sep 17 00:00:00 2001
From: Nic Crane <thisisnic@gmail.com>
Date: Sat, 12 Sep 2026 07:47:44 -0400
Subject: [PATCH 2/5] Remove arrange before summarise/mutate

---
 r/R/dplyr-mutate.R                      |  2 ++
 r/R/dplyr-summarize.R                   |  2 ++
 r/tests/testthat/test-dplyr-mutate.R    | 11 +++++++++++
 r/tests/testthat/test-dplyr-summarize.R |  9 +++++++++
 4 files changed, 24 insertions(+)

diff --git a/r/R/dplyr-mutate.R b/r/R/dplyr-mutate.R
index a62149f6743e..9c41a660b8f1 100644
--- a/r/R/dplyr-mutate.R
+++ b/r/R/dplyr-mutate.R
@@ -75,6 +75,8 @@ mutate.arrow_dplyr_query <- function(
       # Make a copy of .data, do the aggregations on it, and then left_join on
       # the group_by variables.
       agg_query <- as_adq(.data)
+      agg_query$arrange_vars <- list()
+      agg_query$arrange_desc <- logical()
       # These may be computed by .by, make sure they're set
       agg_query$group_by_vars <- grv
       agg_query$aggregations <- mask$.aggregations
diff --git a/r/R/dplyr-summarize.R b/r/R/dplyr-summarize.R
index 7c2a44eec3d5..0d44f741a116 100644
--- a/r/R/dplyr-summarize.R
+++ b/r/R/dplyr-summarize.R
@@ -88,6 +88,8 @@ do_arrow_summarize <- function(.data, ..., .groups = NULL) {
   # Apply the results to the .data object.
   # First, the aggregations
   .data$aggregations <- mask$.aggregations
+  .data$arrange_vars <- list()
+  .data$arrange_desc <- logical()
   # Then collapse the query so that the resulting query object can have
   # additional operations applied to it
   out <- collapse.arrow_dplyr_query(.data)
diff --git a/r/tests/testthat/test-dplyr-mutate.R b/r/tests/testthat/test-dplyr-mutate.R
index 63f69227b289..9accf48eecdc 100644
--- a/r/tests/testthat/test-dplyr-mutate.R
+++ b/r/tests/testthat/test-dplyr-mutate.R
@@ -775,3 +775,14 @@ test_that("across() does not select grouping variables within transmute()", {
     "Column `chr` doesn't exist"
   )
 })
+
+test_that("mutate() with aggregations after arrange() (GH-45373)", {
+  compare_dplyr_binding(
+    .input |>
+      select(int, chr) |>
+      arrange(int) |>
+      mutate(avg_int = mean(int)) |>
+      collect(),
+    tbl
+  )
+})
diff --git a/r/tests/testthat/test-dplyr-summarize.R b/r/tests/testthat/test-dplyr-summarize.R
index 2cd68528ac5f..b58102597a5f 100644
--- a/r/tests/testthat/test-dplyr-summarize.R
+++ b/r/tests/testthat/test-dplyr-summarize.R
@@ -1345,4 +1345,13 @@ test_that("summarize() after arrange() (GH-45373)", {
       collect(),
     tbl
   )
+  compare_dplyr_binding(
+    .input |>
+      arrange(dbl) |>
+      group_by(some_grouping) |>
+      summarize(total = sum(int, na.rm = TRUE)) |>
+      arrange(some_grouping) |>
+      collect(),
+    tbl
+  )
 })

From bc9b73fef65fa336ec5753ea32ec8212b027ea4f Mon Sep 17 00:00:00 2001
From: Nic Crane <thisisnic@gmail.com>
Date: Sat, 12 Sep 2026 08:41:15 -0400
Subject: [PATCH 3/5] Add test to appease false positive reviews

---
 r/tests/testthat/test-dplyr-mutate.R    | 10 ++++++++++
 r/tests/testthat/test-dplyr-summarize.R |  9 +++++++++
 2 files changed, 19 insertions(+)

diff --git a/r/tests/testthat/test-dplyr-mutate.R b/r/tests/testthat/test-dplyr-mutate.R
index 9accf48eecdc..033d8f32ffb0 100644
--- a/r/tests/testthat/test-dplyr-mutate.R
+++ b/r/tests/testthat/test-dplyr-mutate.R
@@ -785,4 +785,14 @@ test_that("mutate() with aggregations after arrange() (GH-45373)", {
       collect(),
     tbl
   )
+  # A row limit between arrange() and mutate() still uses the sorted rows
+  compare_dplyr_binding(
+    .input |>
+      select(int, chr) |>
+      arrange(int) |>
+      head(3) |>
+      mutate(max_int = max(int, na.rm = TRUE)) |>
+      collect(),
+    tbl
+  )
 })
diff --git a/r/tests/testthat/test-dplyr-summarize.R b/r/tests/testthat/test-dplyr-summarize.R
index b58102597a5f..0e2ce8465574 100644
--- a/r/tests/testthat/test-dplyr-summarize.R
+++ b/r/tests/testthat/test-dplyr-summarize.R
@@ -1354,4 +1354,13 @@ test_that("summarize() after arrange() (GH-45373)", {
       collect(),
     tbl
   )
+  # A row limit between arrange() and summarize() still uses the sorted rows
+  compare_dplyr_binding(
+    .input |>
+      arrange(int) |>
+      head(3) |>
+      summarize(max_int = max(int, na.rm = TRUE)) |>
+      collect(),
+    tbl
+  )
 })

From ad71f3505956b12a0c2bedc2fb0906cdc3d2e6d1 Mon Sep 17 00:00:00 2001
From: Nic Crane <thisisnic@gmail.com>
Date: Wed, 16 Sep 2026 11:35:51 -0500
Subject: [PATCH 4/5] Appease copilot

---
 r/tests/testthat/test-dplyr-mutate.R    | 2 +-
 r/tests/testthat/test-dplyr-summarize.R | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/r/tests/testthat/test-dplyr-mutate.R b/r/tests/testthat/test-dplyr-mutate.R
index 033d8f32ffb0..5a5c6181a11e 100644
--- a/r/tests/testthat/test-dplyr-mutate.R
+++ b/r/tests/testthat/test-dplyr-mutate.R
@@ -789,7 +789,7 @@ test_that("mutate() with aggregations after arrange() (GH-45373)", {
   compare_dplyr_binding(
     .input |>
       select(int, chr) |>
-      arrange(int) |>
+      arrange(desc(int)) |>
       head(3) |>
       mutate(max_int = max(int, na.rm = TRUE)) |>
       collect(),
diff --git a/r/tests/testthat/test-dplyr-summarize.R b/r/tests/testthat/test-dplyr-summarize.R
index 0e2ce8465574..b2c9adeace5e 100644
--- a/r/tests/testthat/test-dplyr-summarize.R
+++ b/r/tests/testthat/test-dplyr-summarize.R
@@ -1357,7 +1357,7 @@ test_that("summarize() after arrange() (GH-45373)", {
   # A row limit between arrange() and summarize() still uses the sorted rows
   compare_dplyr_binding(
     .input |>
-      arrange(int) |>
+      arrange(desc(int)) |>
       head(3) |>
       summarize(max_int = max(int, na.rm = TRUE)) |>
       collect(),

From 372432740c42410a6f72133e3a1cfd85208d8d37 Mon Sep 17 00:00:00 2001
From: Nic Crane <thisisnic@gmail.com>
Date: Wed, 16 Sep 2026 13:18:53 -0500
Subject: [PATCH 5/5] do min not max

---
 r/tests/testthat/test-dplyr-mutate.R    | 2 +-
 r/tests/testthat/test-dplyr-summarize.R | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/r/tests/testthat/test-dplyr-mutate.R b/r/tests/testthat/test-dplyr-mutate.R
index 5a5c6181a11e..d8f5579c36e9 100644
--- a/r/tests/testthat/test-dplyr-mutate.R
+++ b/r/tests/testthat/test-dplyr-mutate.R
@@ -791,7 +791,7 @@ test_that("mutate() with aggregations after arrange() (GH-45373)", {
       select(int, chr) |>
       arrange(desc(int)) |>
       head(3) |>
-      mutate(max_int = max(int, na.rm = TRUE)) |>
+      mutate(min_int = min(int, na.rm = TRUE)) |>
       collect(),
     tbl
   )
diff --git a/r/tests/testthat/test-dplyr-summarize.R b/r/tests/testthat/test-dplyr-summarize.R
index b2c9adeace5e..4e5b0b93cc7a 100644
--- a/r/tests/testthat/test-dplyr-summarize.R
+++ b/r/tests/testthat/test-dplyr-summarize.R
@@ -1359,7 +1359,7 @@ test_that("summarize() after arrange() (GH-45373)", {
     .input |>
       arrange(desc(int)) |>
       head(3) |>
-      summarize(max_int = max(int, na.rm = TRUE)) |>
+      summarize(min_int = min(int, na.rm = TRUE)) |>
       collect(),
     tbl
   )