1 files changed, 24 insertions, 0 deletions

diff --git a/docs/TESTING.md b/docs/TESTING.md
index 0c931d8..c68b6c4 100644
--- a/docs/TESTING.md
+++ b/docs/TESTING.md
@@ -9,6 +9,30 @@ cargo test
 The suite is deterministic and headless: no network, no PTY, no sleeps, no
 shared global database. Each test owns its state.
 
+## Cross-compiling the client
+
+The client is rustls-only. The server is the only thing that links OpenSSL via
+`native-tls`, so it is behind the default `server` feature. Building the client
+for another target does not need that toolchain at all:
+
+```sh
+rustup target add i686-unknown-linux-gnu
+cargo build --release --bin client --no-default-features \
+  --target i686-unknown-linux-gnu
+```
+
+`--no-default-features` drops `native-tls`, which is what fails with
+`Could not find OpenSSL` when no 32-bit OpenSSL is installed. `rusqlite` is
+bundled and `ring` (rustls) only needs `gcc -m32`, which a normal multilib
+setup provides. The binary can be checked with
+`file target/i686-unknown-linux-gnu/release/client`; it must say `ELF 32-bit`
+and `Intel i386`.
+
+Building the server for i686 is a different problem: it needs 32-bit OpenSSL
+headers and libraries (`libssl-dev:i386` plus
+`PKG_CONFIG_ALLOW_CROSS=1 PKG_CONFIG_LIBDIR=/usr/lib/i386-linux-gnu/pkgconfig`),
+or a vendored OpenSSL.
+
 | File | Covers |
 | --- | --- |
 | `tests/client_core.rs` | Client command/game flows via a headless screen applying logical effects. |