From 8dd0d46c3c5d05d93a51ad6aded3dbeff8a9aacd Mon Sep 17 00:00:00 2001
From: Claw <claw@devop.live>
Date: Tue, 28 Jul 2026 12:33:53 -0500
Subject: [PATCH] =?UTF-8?q?build:=20pin=20rustc=201.94.0=20=E2=80=94=20the?=
 =?UTF-8?q?=20workspace=20only=20builds=20in=20a=20narrow=20band?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Established empirically in a clean Debian 13 container (2026-07-28), not inferred
from the dev host:

  1.85.0  (apt install rustc, Debian trixie)  -> FAILS, aws-sdk-* need >= 1.91.1
  1.97.1  (rustup default stable, today)      -> FAILS, ethnum E0512 transmute
  1.94.0                                      -> builds clean, workspace, 2m39s

Both obvious reviewer paths break: the distro compiler is too old and current
rustup stable is too new. Before this pin the build reproduced on our host only
because the toolchain had been restored from the previous machine — reproducible
by accident rather than by construction.

Verified the pin works: set the shell default to the BROKEN stable, and the repo
still resolved 1.94.0 and built.

Minimal native prerequisites, also tested in the clean container:
  protobuf-compiler (lance-encoding/lance-file build scripts need protoc),
  pkg-config, libssl-dev.
NOT required despite being installed on the dev host: cmake, clang, libclang-dev.
---
 rust-toolchain.toml | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 rust-toolchain.toml

diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..d5502a4
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,27 @@
+# Pinned toolchain — this workspace only builds inside a NARROW rustc band.
+#
+# Established empirically 2026-07-28 in a clean Debian 13 container:
+#
+#   rustc 1.85.0  (what `apt install rustc` gives on Debian trixie)
+#       -> FAILS: "rustc 1.85.0 is not supported by the following packages"
+#          aws-config, aws-sdk-*, aws-smithy-* all require >= 1.91.1
+#
+#   rustc 1.97.1  (what `rustup default stable` gives today)
+#       -> FAILS: ethnum, error[E0512] "cannot transmute between types of
+#          different sizes, or dependently-sized types"
+#
+#   rustc 1.94.0  -> builds clean (2m39s, workspace, exit 0)
+#
+# So BOTH obvious reviewer paths break: distro rustc is too old, rustup stable
+# is too new. Without this pin the build reproduced on our host only because the
+# toolchain happened to be restored from the previous machine. Pinning makes it
+# reproducible by construction rather than by accident.
+#
+# Native prerequisites (also verified in the clean container, minimal set):
+#   protobuf-compiler   -- lance-encoding / lance-file build scripts need protoc
+#   pkg-config
+#   libssl-dev
+# NOT required, despite being installed on the dev host: cmake, clang, libclang-dev.
+[toolchain]
+channel = "1.94.0"
+profile = "minimal"