diff --git a/Dockerfile b/Dockerfile
index 04563645..580afc59 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -95,6 +95,13 @@ RUN --mount=type=cache,target=/root/.cache/zig \
     fi && \
     zig build -Doptimize=ReleaseSafe -Dgit_version="$GIT_VERSION"
 
+# rec_aggregation's compilation.rs reads .py source files at runtime to verify
+# a bytecode fingerprint (via env!("CARGO_MANIFEST_DIR") baked at compile time).
+# Stage the crate source so we can recreate the path in the runtime image.
+RUN REC_AGG_DIR=$(find /root/.cargo/git/checkouts -path "*/rec_aggregation" -type d | head -1) \
+    && cp -r "$REC_AGG_DIR" /tmp/rec_aggregation_src \
+    && echo "$REC_AGG_DIR" > /tmp/rec_aggregation_path
+
 # Intermediate stage to prepare runtime libraries
 FROM ubuntu:24.04 AS runtime-prep
 ARG TARGETARCH
@@ -104,6 +111,13 @@ COPY --from=builder /app/zig-out/ /app/zig-out/
 COPY --from=builder /app/resources/ /app/resources/
 COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 
+# Recreate rec_aggregation .py files at the baked-in CARGO_MANIFEST_DIR path
+COPY --from=builder /tmp/rec_aggregation_src /tmp/rec_aggregation_src
+COPY --from=builder /tmp/rec_aggregation_path /tmp/rec_aggregation_path
+RUN mkdir -p "$(cat /tmp/rec_aggregation_path)" \
+    && cp -r /tmp/rec_aggregation_src/* "$(cat /tmp/rec_aggregation_path)/" \
+    && rm -rf /tmp/rec_aggregation_src /tmp/rec_aggregation_path
+
 # Create a script to copy the right libraries based on architecture
 RUN mkdir -p /runtime-libs && \
     case "$TARGETARCH" in \
@@ -163,6 +177,9 @@ COPY --from=builder /app/zig-out/ /app/zig-out/
 # Copy runtime resources
 COPY --from=builder /app/resources/ /app/resources/
 
+# Copy rec_aggregation .py files at baked-in CARGO_MANIFEST_DIR path
+COPY --from=runtime-prep /root/.cargo/ /root/.cargo/
+
 # Set the zeam binary as the entrypoint with beam parameter by default
 ENTRYPOINT ["/app/zig-out/bin/zeam"]
 
diff --git a/rust/libp2p-glue/src/lib.rs b/rust/libp2p-glue/src/lib.rs
index 76fe7063..117c343f 100644
--- a/rust/libp2p-glue/src/lib.rs
+++ b/rust/libp2p-glue/src/lib.rs
@@ -1439,7 +1439,7 @@ impl Behaviour {
             .validation_mode(gossipsub::ValidationMode::Anonymous)
             .history_length(6)
             .duplicate_cache_time(Duration::from_secs(3 * 4 * 2))
-            .max_transmit_size(2 * 1024 * 1024) // 2 MiB for blocks/ aggregated payloads
+            .max_transmit_size(crate::req_resp::configurations::max_message_size())
             .message_id_fn(message_id_fn) // content-address messages. No two messages of the same content will be propagated.
             .build()
             .unwrap();
diff --git a/rust/libp2p-glue/src/req_resp/configurations.rs b/rust/libp2p-glue/src/req_resp/configurations.rs
index e54e5f14..b91c92c5 100644
--- a/rust/libp2p-glue/src/req_resp/configurations.rs
+++ b/rust/libp2p-glue/src/req_resp/configurations.rs
@@ -2,15 +2,23 @@
 /// as we still need rust-libp2p until we fully migrate to zig-libp2p. It needs the custom RPC protocol implementation.
 use std::time::Duration;
 
-/// Maximum allowed size for a single RPC payload (compressed).
-pub const MAX_MESSAGE_SIZE: usize = 4 * 1024 * 1024; // 4 MiB
+/// Maximum uncompressed payload size (10 MiB), per Ethereum consensus spec.
+pub const MAX_PAYLOAD_SIZE: usize = 10 * 1024 * 1024;
+
+/// Snappy worst-case compressed length for a payload of size `n`.
+pub const fn max_compressed_len(n: usize) -> usize {
+    32 + n + n / 6
+}
+
+/// Spec-derived maximum message size: snappy worst-case of MAX_PAYLOAD_SIZE + 1024 bytes
+/// framing overhead, with a floor of 1 MiB.
+/// Matches ream / grandine / lighthouse: `max(max_compressed_len(MAX_PAYLOAD_SIZE) + 1024, 1 MiB)`.
+pub fn max_message_size() -> usize {
+    std::cmp::max(max_compressed_len(MAX_PAYLOAD_SIZE) + 1024, 1024 * 1024)
+}
 
 /// Timeout applied to reading requests and responses from a substream.
 pub const REQUEST_TIMEOUT: Duration = Duration::from_secs(15);
 
 /// Idle timeout for server-side response streams.
 pub const RESPONSE_CHANNEL_IDLE_TIMEOUT: Duration = Duration::from_secs(5 * 60);
-
-pub fn max_message_size() -> usize {
-    MAX_MESSAGE_SIZE
-}