diff --git a/go/scripts/package.sh b/go/scripts/package.sh
index 0627bcefa..6585ae735 100755
--- a/go/scripts/package.sh
+++ b/go/scripts/package.sh
@@ -131,7 +131,13 @@ GO_LIBS=(
     "aarch64-apple-darwin:darwin_arm64:libmoq_ffi.a"
     "x86_64-pc-windows-msvc:windows_amd64:moq_ffi.lib"
 )
+# GitHub's pre-receive hook rejects any file >= 100 MiB. The mirror commits
+# these libs into git, so an oversized lib fails the publish push (GH001).
+# Catch it here, where the error names the file and points at the fix, rather
+# than after a multi-target build burns an hour to die at `git push`.
+GITHUB_FILE_LIMIT=$((100 * 1024 * 1024))
 STAGED_ANY=false
+OVERSIZED=()
 for entry in "${GO_LIBS[@]}"; do
     target="${entry%%:*}"
     rest="${entry#*:}"
@@ -142,7 +148,9 @@ for entry in "${GO_LIBS[@]}"; do
         dest="$PKG_STAGE/moq/lib/$goarch"
         mkdir -p "$dest"
         cp "$src" "$dest/"
-        echo "  go lib $goarch <- $target"
+        size=$(wc -c <"$src")
+        echo "  go lib $goarch <- $target ($((size / 1024 / 1024)) MiB)"
+        [[ "$size" -ge "$GITHUB_FILE_LIMIT" ]] && OVERSIZED+=("$goarch/$libname: $((size / 1024 / 1024)) MiB")
         STAGED_ANY=true
     else
         echo "  go lib $goarch: skipped, $src missing"
@@ -154,6 +162,13 @@ if [[ "$STAGED_ANY" != true ]]; then
     exit 1
 fi
 
+if [[ "${#OVERSIZED[@]}" -gt 0 ]]; then
+    echo "Error: staged libs exceed GitHub's 100 MiB push limit:" >&2
+    printf '  %s\n' "${OVERSIZED[@]}" >&2
+    echo "The mirror push would be rejected (GH001). Shrink the staticlib in rs/moq-ffi/build.sh (LTO)." >&2
+    exit 1
+fi
+
 # --- 4. Minimal consumer-facing README rewrite ---
 # The full developer README lives in the monorepo; the staged copy
 # (which ends up on moq-dev/moq-go) gets a thin orientation pointer.
diff --git a/nix/overlay.nix b/nix/overlay.nix
index d6f3514de..0f8a82faa 100644
--- a/nix/overlay.nix
+++ b/nix/overlay.nix
@@ -83,6 +83,14 @@ in
         doCheck = false;
         nativeBuildInputs = with final; [ pkg-config ];
 
+        # libmoq.a carries moq-ffi's whole dep tree, so an unstripped build is
+        # ~75 MB+. Thin LTO with a single codegen unit dead-strips the unused
+        # monomorphizations Rust bakes into a staticlib, halving the artifact
+        # with no source or ABI change, which keeps the release tarball and
+        # brew download small. Mirrors rs/libmoq/build.sh's Windows cargo path.
+        CARGO_PROFILE_RELEASE_LTO = "thin";
+        CARGO_PROFILE_RELEASE_CODEGEN_UNITS = "1";
+
         # libmoq is a staticlib; crane's default install phase only handles
         # binaries. Lay out the artifact tree the way release tarballs and
         # downstream `find_package(moq)` consumers already expect.
diff --git a/rs/libmoq/build.sh b/rs/libmoq/build.sh
index 206e3fabf..a308ea03c 100755
--- a/rs/libmoq/build.sh
+++ b/rs/libmoq/build.sh
@@ -16,6 +16,17 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 RS_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
 WORKSPACE_DIR="$(cd "$RS_DIR/.." && pwd)"
 
+# Shrink the release staticlib. libmoq.a carries the same heavy dep tree as
+# moq-ffi, so an unstripped build is ~75 MB+. libmoq ships as a release
+# tarball (not a git mirror, so no hard 100 MB limit like moq-go), but thin
+# LTO with a single codegen unit dead-strips the unused monomorphizations Rust
+# bakes into a staticlib, halving the artifact with no source or ABI changes.
+# This covers the Windows cargo path below; the nix/crane path (Linux/macOS)
+# sets the same vars in nix/overlay.nix. Scoped here so a plain
+# `cargo build --release` stays fast; a caller can still override.
+export CARGO_PROFILE_RELEASE_LTO="${CARGO_PROFILE_RELEASE_LTO:-thin}"
+export CARGO_PROFILE_RELEASE_CODEGEN_UNITS="${CARGO_PROFILE_RELEASE_CODEGEN_UNITS:-1}"
+
 TARGET=""
 VERSION=""
 OUTPUT_DIR="dist"
diff --git a/rs/moq-ffi/build.sh b/rs/moq-ffi/build.sh
index 37f00ee32..171f204d4 100755
--- a/rs/moq-ffi/build.sh
+++ b/rs/moq-ffi/build.sh
@@ -14,6 +14,19 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 RS_DIR="$(cd "$SCRIPT_DIR/.." && pwd)"
 WORKSPACE_DIR="$(cd "$RS_DIR/.." && pwd)"
 
+# Shrink the release staticlib. The Go mirror commits the native libs straight
+# into git, and GitHub's pre-receive hook hard-rejects any file over 100 MB
+# (GH001). An unstripped moq-ffi staticlib is ~110 MB on Linux, which silently
+# blocked every moq-go mirror push and pinned consumers to a stale release.
+# Thin LTO with a single codegen unit dead-strips the unused monomorphizations
+# Rust bakes into a staticlib, cutting it by ~60% (~110 MB to ~35 MB) with no
+# source or ABI changes. (Swift ships an XCFramework release asset and Kotlin a
+# Maven .so, so neither hits the git limit, but both still get smaller libs.)
+# Scoped here via env vars so a plain `cargo build --release` stays fast; a
+# caller can still override.
+export CARGO_PROFILE_RELEASE_LTO="${CARGO_PROFILE_RELEASE_LTO:-thin}"
+export CARGO_PROFILE_RELEASE_CODEGEN_UNITS="${CARGO_PROFILE_RELEASE_CODEGEN_UNITS:-1}"
+
 # Resolve cargo target directory (respects CARGO_TARGET_DIR, .cargo/config, etc.)
 TARGET_BASE_DIR=$(cargo metadata --format-version 1 --manifest-path "$WORKSPACE_DIR/Cargo.toml" --no-deps 2>/dev/null |
     sed -n 's/.*"target_directory":"\([^"]*\)".*/\1/p' ||