diff --git a/deploy/docker/Dockerfile b/deploy/docker/Dockerfile
index d14fb88..ed2f2d0 100644
--- a/deploy/docker/Dockerfile
+++ b/deploy/docker/Dockerfile
@@ -33,7 +33,12 @@ WORKDIR /src
 # to silently serve stale stub binaries when cargo's fingerprint didn't
 # notice the source swap. A single build is ~1.5 min longer on cold cache
 # but guarantees the binary reflects the sources we copied.
-COPY Cargo.toml rust-toolchain.toml ./
+# Do not copy rust-toolchain.toml into the image. The local workspace pins
+# developer tooling, but inside Docker we intentionally use the Rust version
+# selected by the base image. Copying rust-toolchain.toml with
+# `channel = "stable"` makes rustup download a second full toolchain during
+# `cargo build`, which is slow and can exhaust small Colima/CI disks.
+COPY Cargo.toml ./
 COPY crates/ crates/
 COPY --from=fetch /src/assets/ipxe /src/assets/ipxe