From 76ab6ed685158d9e252a5285d5bafb4213abb6e3 Mon Sep 17 00:00:00 2001
From: Minh Vu <vuhoangminh97@gmail.com>
Date: Sun, 16 Aug 2026 02:28:51 +0200
Subject: [PATCH 1/2] Fix iterate subscribe exception specification

---
 include/exec/sequence/iterate.hpp   |  7 ++++++-
 test/exec/sequence/test_iterate.cpp | 29 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/include/exec/sequence/iterate.hpp b/include/exec/sequence/iterate.hpp
index a85f37c94..fba51cc1a 100644
--- a/include/exec/sequence/iterate.hpp
+++ b/include/exec/sequence/iterate.hpp
@@ -178,7 +178,12 @@ namespace experimental::execution
     struct __subscribe_fn
     {
       template <class _Range>
-      constexpr auto operator()(__ignore, _Range&& __range) noexcept
+      constexpr auto operator()(__ignore, _Range&& __range) noexcept(
+        noexcept(std::ranges::begin(static_cast<_Range&&>(__range)))
+        && noexcept(std::ranges::end(static_cast<_Range&&>(__range)))
+        && __nothrow_move_constructible<std::ranges::iterator_t<_Range>,
+                                        std::ranges::sentinel_t<_Range>,
+                                        _Receiver>)
       {
         return __operation{std::ranges::begin(static_cast<_Range&&>(__range)),
                            std::ranges::end(static_cast<_Range&&>(__range)),
diff --git a/test/exec/sequence/test_iterate.cpp b/test/exec/sequence/test_iterate.cpp
index 408630a9a..cae2088fe 100644
--- a/test/exec/sequence/test_iterate.cpp
+++ b/test/exec/sequence/test_iterate.cpp
@@ -25,6 +25,26 @@
 namespace
 {
 
+  struct begin_error
+  {};
+
+  struct begin_throws_range
+  {
+    using iterator = std::array<int, 1>::iterator;
+
+    iterator begin()
+    {
+      throw begin_error{};
+    }
+
+    iterator end() noexcept
+    {
+      return values.end();
+    }
+
+    std::array<int, 1> values{0};
+  };
+
   template <class Receiver>
   struct sum_item_rcvr
   {
@@ -140,4 +160,13 @@ namespace
     CHECK(sum == (42 + 43 + 44 + 1));
   }
 
+  TEST_CASE("iterate - subscribe propagates begin exceptions", "[sequence_senders][iterate]")
+  {
+    auto iterate = exec::iterate(begin_throws_range{});
+    int  sum     = 0;
+
+    STATIC_REQUIRE_FALSE(noexcept(exec::subscribe(iterate, sum_receiver<>{.sum_ = sum})));
+    CHECK_THROWS_AS(exec::subscribe(iterate, sum_receiver<>{.sum_ = sum}), begin_error);
+  }
+
 }  // namespace

From 25d49276b52f734d90cb97fbab080d5eb1f67a09 Mon Sep 17 00:00:00 2001
From: Minh Vu <vuhoangminh97@gmail.com>
Date: Sun, 16 Aug 2026 20:52:51 +0200
Subject: [PATCH 2/2] Format iterate subscribe exception specification

---
 include/exec/sequence/iterate.hpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/exec/sequence/iterate.hpp b/include/exec/sequence/iterate.hpp
index fba51cc1a..6ab2d2908 100644
--- a/include/exec/sequence/iterate.hpp
+++ b/include/exec/sequence/iterate.hpp
@@ -178,12 +178,12 @@ namespace experimental::execution
     struct __subscribe_fn
     {
       template <class _Range>
-      constexpr auto operator()(__ignore, _Range&& __range) noexcept(
-        noexcept(std::ranges::begin(static_cast<_Range&&>(__range)))
-        && noexcept(std::ranges::end(static_cast<_Range&&>(__range)))
-        && __nothrow_move_constructible<std::ranges::iterator_t<_Range>,
-                                        std::ranges::sentinel_t<_Range>,
-                                        _Receiver>)
+      constexpr auto operator()(__ignore, _Range&& __range)
+        noexcept(noexcept(std::ranges::begin(static_cast<_Range&&>(__range)))
+                 && noexcept(std::ranges::end(static_cast<_Range&&>(__range)))
+                 && __nothrow_move_constructible<std::ranges::iterator_t<_Range>,
+                                                 std::ranges::sentinel_t<_Range>,
+                                                 _Receiver>)
       {
         return __operation{std::ranges::begin(static_cast<_Range&&>(__range)),
                            std::ranges::end(static_cast<_Range&&>(__range)),