diff --git a/FORK.md b/FORK.md
index 3ea847f..4ce6fa6 100644
--- a/FORK.md
+++ b/FORK.md
@@ -15,6 +15,12 @@ npm run ship -- --dmg      # …and put an installer on the Desktop
 cd src-tauri && cargo test  # 26 tests, all pure logic
 ```
 
+`rust-toolchain.toml` at the project root pins the channel to `stable` and must be
+present. On a fresh machine that has never set a rustup default, `tauri-cli` calls
+`cargo metadata` without specifying a toolchain and panics in its metadata thread —
+not a clear error message, just an abort. The file guarantees the toolchain is always
+resolved correctly regardless of what the machine's rustup default is configured to.
+
 Read `README.md` for what it does and
 `docs/superpowers/specs/2026-09-01-work-app-design.md` for why it is built this way. The
 git history is included and the commit messages carry the reasoning — most of them
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..292fe49
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,2 @@
+[toolchain]
+channel = "stable"