diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d5df34e..55f4ee3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -79,6 +79,8 @@ jobs:
             echo "$req"
             grep -q 'openkal.stream' <<<"$req" && ! grep -q 'openkal.net' <<<"$req" \
               || { echo "::error::a weak import made the image require its interface"; exit 1; }
+            # 6 MiB of frames on the main thread, the runner's on Windows (0.5.2).
+            bash examples/build-image.sh "$arch" "out/$arch/stack.oke" examples/stack/app.c
             cp "out/$arch/hello.oke" "out/$arch/signed.oke"
             # The library examples/bind binds for a program of each system.
             bash examples/build-image.sh "$arch" "out/$arch/libmathlib.okso" examples/bind/mathlib/image/mathlib.c
@@ -275,6 +277,10 @@ jobs:
           n=$("$OKRUN" "out/$a/needed.oke" | tr -d '\r')
           echo "$n"
           grep -q "twice(21) = 42, next_value() = 41" <<<"$n" || { echo "::error::an image another needs"; exit 1; }
+          # THE MAIN THREAD HAS A THREAD'S STACK (0.5.2): on Windows the runner's
+          # reservation, which was the linker's 1 MiB default.
+          st=$("$OKRUN" "out/$a/stack.oke" | tr -d '\r')
+          test "$st" = 'stack: 6 MiB on the main thread' || { echo "::error::the image's main thread has less than a thread's stack: $st"; exit 1; }
           w=$("$OKRUN" "out/$a/weak.oke" | tr -d '\r')
           echo "$w"
           grep -q "weak: openkal.net bound" <<<"$w" || { echo "::error::a weak import the implementation provides was not bound"; exit 1; }
diff --git a/README.md b/README.md
index 9f93873..14323a1 100644
--- a/README.md
+++ b/README.md
@@ -27,6 +27,13 @@ rules hold sixteen long grants, and states the kernel layer as compatible ranges
 (openkal `^0.24.0`, Linux `^0.25.0`, macOS `^0.22.1`, Windows `^0.20.0`). The
 format, the loader and the import names are unchanged.
 
+Version 0.5.2 gives an image's main thread a thread's stack on Windows. An image
+is entered on okrun's main thread, whose stack there is the executable's
+reservation, the linker's 1 MiB; okrun.exe now reserves 8 MiB + 256 KiB, a
+thread's default under openkal-windows, as Linux and macOS give the main thread
+8 MiB. The `stack` example recurses through 6 MiB on the main thread on every
+system.
+
 ## An image
 
 ```sh
diff --git a/bind/mcpp.toml b/bind/mcpp.toml
index 31f5b90..eb05ff0 100644
--- a/bind/mcpp.toml
+++ b/bind/mcpp.toml
@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-bind"
-version     = "0.5.1"
+version     = "0.5.2"
 # `mcpp::xpkg_request', `mcpp::decision' (protocol 15).
 mcpp        = ">=2026.10.1.3"
 description = "A build plugin: a library published as an ok image (.okso) and a C header is called from a program of any system, through a binding generated from the header and libokrun."
diff --git a/docs/bind.md b/docs/bind.md
index b6d065d..7152d4c 100644
--- a/docs/bind.md
+++ b/docs/bind.md
@@ -110,6 +110,7 @@ llvm toolchain's clang converts the call.
 | 0.3.2 | No change of its own; released with the archive, whose runner is built over openkal 0.22's implementations: a started program is given the system's null device at a position (`KAL_SPAWN_NULL_*`). |
 | 0.5.0 | The binding format is unchanged; the runner selects OpenKal 0.24 and binds its four process-unit operations. |
 | 0.5.1 | No change of its own; released with the archive, whose runner is built over openkal-macos 0.22.1 (confinement rules sized to their grants). |
+| 0.5.2 | No change of its own; released with the archive, whose runner on Windows reserves a thread's stack for the image's main thread. |
 | 0.4.0 | No change of its own; released with the archive, whose loader places an image at the base `okld place` chose for it (openkal 0.23, `kal_exec_alloc_at`) and then applies only the relocations that name a symbol. |
 | 0.4.1 | No change of its own; released with the archive, whose runner on macOS is built over openkal-macos 0.21.2 (a sleep is no longer a spin of the processor; the granularity is the same at every start). |
 | 0.4.2 | No change of its own; released with the archive, whose runner on macOS is built over openkal-macos 0.21.3 (asked before the implementation's initialiser ran, it answers from the loader's record). |
diff --git a/examples/stack/app.c b/examples/stack/app.c
new file mode 100644
index 0000000..a353059
--- /dev/null
+++ b/examples/stack/app.c
@@ -0,0 +1,30 @@
+/* The image's main thread has the stack a thread has (openkal-image 0.5.2): an
+ * image is entered on the runner's main thread, and on Windows that thread's
+ * stack is the runner's reservation. This one recurses through 6 MiB of
+ * frames, each touched page by page (-fstack-clash-protection), where a thread
+ * of openkal-windows has at least 8 MiB and Linux and macOS give the main
+ * thread 8 MiB. The entry is `int ok_main(void)' (SPEC 12.2). */
+typedef unsigned long kal_uintptr;
+typedef long kal_intptr;
+struct kal_stream { kal_uintptr h; };
+
+struct kal_stream kal_stdout(void);
+kal_intptr kal_stream_write(struct kal_stream, const void*, kal_uintptr);
+
+static void put(const char* s) {
+    unsigned long n = 0; while (s[n]) ++n;
+    kal_stream_write(kal_stdout(), s, n);
+}
+
+__attribute__((noinline)) static unsigned descend(unsigned depth) {
+    volatile unsigned char frame[64 * 1024];
+    for (unsigned i = 0; i < sizeof frame; i += 4096) frame[i] = (unsigned char)depth;
+    unsigned below = depth ? descend(depth - 1) : 0;
+    return below + frame[depth % sizeof frame];
+}
+
+__attribute__((visibility("default"))) int ok_main(void) {
+    descend(96);   /* 96 frames of 64 KiB: 6 MiB */
+    put("stack: 6 MiB on the main thread\n");
+    return 0;
+}
diff --git a/ld/mcpp.toml b/ld/mcpp.toml
index 8ceb501..e2e9faa 100644
--- a/ld/mcpp.toml
+++ b/ld/mcpp.toml
@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-ld"
-version     = "0.5.1"
+version     = "0.5.2"
 description = "libokld: the ok format (openkal image format) --- its definition, a reader of bytes, a checker, a signer, and a loader. Freestanding: no C library, no exceptions."
 license     = "Apache-2.0"
 authors     = ["mcpplibs"]
diff --git a/run/mcpp.toml b/run/mcpp.toml
index 0f341e4..2183bd7 100644
--- a/run/mcpp.toml
+++ b/run/mcpp.toml
@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-run"
-version     = "0.5.1"
+version     = "0.5.2"
 description = "libokrun: the runner's core --- an ok image's names bound to this process's one openkal implementation, in the image's calling convention, and its entry entered."
 license     = "Apache-2.0"
 authors     = ["mcpplibs"]
diff --git a/tools/mcpp.toml b/tools/mcpp.toml
index 8980d36..80c09ac 100644
--- a/tools/mcpp.toml
+++ b/tools/mcpp.toml
@@ -1,7 +1,7 @@
 [package]
 namespace   = "mcpplibs"
 name        = "openkal-tools"
-version     = "0.5.1"
+version     = "0.5.2"
 description = "okrun, which runs an ok image on this system, and okld, the format's tool on a build machine (check, note, sign, inspect)."
 license     = "Apache-2.0"
 authors     = ["mcpplibs"]
@@ -31,3 +31,18 @@ main = "src/okprof.cpp"
 
 [build]
 sources = []
+
+# THE IMAGE'S MAIN THREAD IS THE RUNNER'S (0.5.2): an image is entered on okrun's
+# main thread, whose stack on Windows is the executable's reservation, 1 MiB by
+# the linker's default. openkal-windows gives every other thread at least 8 MiB
+# (kal_task_start), and Linux and macOS give the main thread 8 MiB; an image's
+# deep recursion on its main thread -- clangd.okb indexing the MSVC headers with
+# `--sync` -- ended in STATUS_STACK_OVERFLOW. The reservation is a thread's
+# default and openkal-windows' guard slack, 8 MiB + 256 KiB, spelled for each
+# linker: lld-link on the MSVC ABI (a Windows host), the MinGW driver on the GNU
+# ABI (the hosted arrangement, and a cross build).
+[target.'cfg(all(windows, env = "msvc"))'.build]
+ldflags = ["-Wl,/STACK:8650752"]
+
+[target.'cfg(all(windows, env = "gnu"))'.build]
+ldflags = ["-Wl,--stack,8650752"]