diff --git a/CODEOWNERS b/CODEOWNERS
index 76c9b881688..e015d47ae86 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -8,7 +8,7 @@ crates/config/              @onbjerg
 crates/consensus/           @rkrasiuk @mattsse @Rjected
 crates/engine               @rkrasiuk @mattsse @Rjected
 crates/e2e-test-utils/      @mattsse @Rjected
-crates/engine-primitives/   @rkrasiuk @mattsse @Rjected
+crates/engine/              @rkrasiuk @mattsse @Rjected @fgimenez
 crates/errors/              @mattsse
 crates/ethereum/            @mattsse @Rjected
 crates/ethereum-forks/      @mattsse @Rjected
diff --git a/crates/consensus/beacon/src/engine/forkchoice.rs b/crates/consensus/beacon/src/engine/forkchoice.rs
index c305cee7d21..491d0ff8aad 100644
--- a/crates/consensus/beacon/src/engine/forkchoice.rs
+++ b/crates/consensus/beacon/src/engine/forkchoice.rs
@@ -140,8 +140,11 @@ impl From<PayloadStatusEnum> for ForkchoiceStatus {
 /// A helper type to check represent hashes of a [`ForkchoiceState`]
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum ForkchoiceStateHash {
+    /// Head hash of the [`ForkchoiceState`].
     Head(B256),
+    /// Safe hash of the [`ForkchoiceState`].
     Safe(B256),
+    /// Finalized hash of the [`ForkchoiceState`].
     Finalized(B256),
 }
 
diff --git a/crates/engine/tree/src/backfill.rs b/crates/engine/tree/src/backfill.rs
index 6fce16c3490..ec0b4ef06cc 100644
--- a/crates/engine/tree/src/backfill.rs
+++ b/crates/engine/tree/src/backfill.rs
@@ -245,7 +245,7 @@ mod tests {
                     checkpoint: StageCheckpoint::new(BlockNumber::from(pipeline_done_after)),
                     done: true,
                 })]))
-                .build(chain_spec.clone());
+                .build(chain_spec);
 
             let pipeline_sync = PipelineSync::new(pipeline, Box::<TokioTaskExecutor>::default());
             let client = TestFullBlockClient::default();
diff --git a/crates/engine/tree/src/chain.rs b/crates/engine/tree/src/chain.rs
index badff5a0925..97c6d615c11 100644
--- a/crates/engine/tree/src/chain.rs
+++ b/crates/engine/tree/src/chain.rs
@@ -102,27 +102,24 @@ where
                 Poll::Pending => {}
             }
 
-            // drain the handler
-            loop {
-                // poll the handler for the next event
-                match this.handler.poll(cx) {
-                    Poll::Ready(handler_event) => {
-                        match handler_event {
-                            HandlerEvent::Pipeline(target) => {
-                                // trigger pipeline and start polling it
-                                this.pipeline.on_action(BackfillAction::Start(target));
-                                continue 'outer
-                            }
-                            HandlerEvent::Event(ev) => {
-                                // bubble up the event
-                                return Poll::Ready(ChainEvent::Handler(ev));
-                            }
+            // poll the handler for the next event
+            match this.handler.poll(cx) {
+                Poll::Ready(handler_event) => {
+                    match handler_event {
+                        HandlerEvent::Pipeline(target) => {
+                            // trigger pipeline and start polling it
+                            this.pipeline.on_action(BackfillAction::Start(target));
+                            continue 'outer
+                        }
+                        HandlerEvent::Event(ev) => {
+                            // bubble up the event
+                            return Poll::Ready(ChainEvent::Handler(ev));
                         }
                     }
-                    Poll::Pending => {
-                        // no more events to process
-                        break 'outer
-                    }
+                }
+                Poll::Pending => {
+                    // no more events to process
+                    break 'outer
                 }
             }
         }
diff --git a/crates/engine/tree/src/download.rs b/crates/engine/tree/src/download.rs
index f264b54535d..12b2bd18928 100644
--- a/crates/engine/tree/src/download.rs
+++ b/crates/engine/tree/src/download.rs
@@ -42,7 +42,7 @@ pub enum DownloadOutcome {
     Blocks(Vec<SealedBlockWithSenders>),
 }
 
-/// Basic [BlockDownloader].
+/// Basic [`BlockDownloader`].
 pub struct BasicBlockDownloader<Client>
 where
     Client: HeadersClient + BodiesClient + Clone + Unpin + 'static,
@@ -253,7 +253,7 @@ impl From<OrderedSealedBlockWithSenders> for SealedBlockWithSenders {
     }
 }
 
-/// A [BlockDownloader] that does nothing.
+/// A [`BlockDownloader`] that does nothing.
 #[derive(Debug, Clone, Default)]
 #[non_exhaustive]
 pub struct NoopBlockDownloader;
diff --git a/crates/engine/tree/src/engine.rs b/crates/engine/tree/src/engine.rs
index c375afa0ea5..d77162e4cd0 100644
--- a/crates/engine/tree/src/engine.rs
+++ b/crates/engine/tree/src/engine.rs
@@ -1,21 +1,18 @@
 //! An engine API handler for the chain.
 
 use crate::{
-    chain::{ChainHandler, FromOrchestrator, HandlerEvent, OrchestratorState},
+    chain::{ChainHandler, FromOrchestrator, HandlerEvent},
     download::{BlockDownloader, DownloadAction, DownloadOutcome},
-    tree::{EngineApiTreeHandler, TreeEvent},
 };
 use futures::{Stream, StreamExt};
-use reth_beacon_consensus::{BeaconEngineMessage, OnForkChoiceUpdated};
+use reth_beacon_consensus::BeaconEngineMessage;
 use reth_engine_primitives::EngineTypes;
 use reth_primitives::{SealedBlockWithSenders, B256};
-use reth_rpc_types::engine::{PayloadStatus, PayloadStatusEnum};
 use std::{
-    collections::{HashSet, VecDeque},
+    collections::HashSet,
     task::{Context, Poll},
 };
 use tokio::sync::mpsc;
-use tracing::trace;
 
 /// Advances the chain based on incoming requests.
 ///
@@ -46,7 +43,7 @@ pub struct EngineHandler<T, S, D> {
 
 impl<T, S, D> EngineHandler<T, S, D> {
     /// Creates a new [`EngineHandler`] with the given handler and downloader.
-    pub fn new(handler: T, downloader: D, incoming_requests: S) -> Self
+    pub const fn new(handler: T, downloader: D, incoming_requests: S) -> Self
     where
         T: EngineRequestHandler,
     {
@@ -70,31 +67,26 @@ where
     fn poll(&mut self, cx: &mut Context<'_>) -> Poll<HandlerEvent<Self::Event>> {
         loop {
             // drain the handler first
-            loop {
-                match self.handler.poll(cx) {
-                    Poll::Ready(ev) => {
-                        match ev {
-                            RequestHandlerEvent::Idle => break,
-                            RequestHandlerEvent::HandlerEvent(ev) => {
-                                return match ev {
-                                    HandlerEvent::Pipeline(target) => {
-                                        // bubble up pipeline request
-                                        self.downloader.on_action(DownloadAction::Clear);
-                                        Poll::Ready(HandlerEvent::Pipeline(target))
-                                    }
-                                    HandlerEvent::Event(ev) => {
-                                        // bubble up the event
-                                        Poll::Ready(HandlerEvent::Event(ev))
-                                    }
-                                }
+            while let Poll::Ready(ev) = self.handler.poll(cx) {
+                match ev {
+                    RequestHandlerEvent::Idle => break,
+                    RequestHandlerEvent::HandlerEvent(ev) => {
+                        return match ev {
+                            HandlerEvent::Pipeline(target) => {
+                                // bubble up pipeline request
+                                self.downloader.on_action(DownloadAction::Clear);
+                                Poll::Ready(HandlerEvent::Pipeline(target))
                             }
-                            RequestHandlerEvent::Download(req) => {
-                                // delegate download request to the downloader
-                                self.downloader.on_action(DownloadAction::Download(req));
+                            HandlerEvent::Event(ev) => {
+                                // bubble up the event
+                                Poll::Ready(HandlerEvent::Event(ev))
                             }
                         }
                     }
-                    Poll::Pending => break,
+                    RequestHandlerEvent::Download(req) => {
+                        // delegate download request to the downloader
+                        self.downloader.on_action(DownloadAction::Download(req));
+                    }
                 }
             }
 
@@ -185,8 +177,11 @@ pub enum EngineApiEvent {}
 
 #[derive(Debug)]
 pub enum FromEngine<Req> {
+    /// Event from the top level orchestrator.
     Event(FromOrchestrator),
+    /// Request from the engine
     Request(Req),
+    /// Downloaded blocks from the network.
     DownloadedBlocks(Vec<SealedBlockWithSenders>),
 }
 
@@ -199,8 +194,11 @@ impl<Req> From<FromOrchestrator> for FromEngine<Req> {
 /// Requests produced by a [`EngineRequestHandler`].
 #[derive(Debug)]
 pub enum RequestHandlerEvent<T> {
+    /// The handler is idle.
     Idle,
+    /// An event emitted by the handler.
     HandlerEvent(HandlerEvent<T>),
+    /// Request to download blocks.
     Download(DownloadRequest),
 }
 
diff --git a/crates/engine/tree/src/lib.rs b/crates/engine/tree/src/lib.rs
index 7aa7fcf75b9..062dd583a9e 100644
--- a/crates/engine/tree/src/lib.rs
+++ b/crates/engine/tree/src/lib.rs
@@ -8,6 +8,7 @@
 )]
 #![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
 // #![cfg_attr(not(test), warn(unused_crate_dependencies))]
+#![allow(missing_docs, dead_code, missing_debug_implementations, unused_variables)] // TODO rm
 
 /// Re-export of the blockchain tree API.
 pub use reth_blockchain_tree_api::*;
diff --git a/crates/engine/tree/src/tree/memory_overlay.rs b/crates/engine/tree/src/tree/memory_overlay.rs
index 3f232b55c20..7e0e1d52e5b 100644
--- a/crates/engine/tree/src/tree/memory_overlay.rs
+++ b/crates/engine/tree/src/tree/memory_overlay.rs
@@ -17,7 +17,7 @@ pub struct MemoryOverlayStateProvider<H> {
 
 impl<H> MemoryOverlayStateProvider<H> {
     /// Create new memory overlay state provider.
-    pub fn new(in_memory: Vec<ExecutedBlock>, historical: H) -> Self {
+    pub const fn new(in_memory: Vec<ExecutedBlock>, historical: H) -> Self {
         Self { in_memory, historical }
     }
 }
diff --git a/crates/engine/tree/src/tree/mod.rs b/crates/engine/tree/src/tree/mod.rs
index 371834b53f9..888183ec6a0 100644
--- a/crates/engine/tree/src/tree/mod.rs
+++ b/crates/engine/tree/src/tree/mod.rs
@@ -162,7 +162,7 @@ pub struct TreeOutcome<T> {
 
 impl<T> TreeOutcome<T> {
     /// Create new tree outcome.
-    pub fn new(outcome: T) -> Self {
+    pub const fn new(outcome: T) -> Self {
         Self { outcome, event: None }
     }
 
@@ -518,7 +518,7 @@ where
             PayloadStatus::from_status(PayloadStatusEnum::Syncing)
         } else {
             let mut latest_valid_hash = None;
-            let status = match self.insert_block_without_senders(block.clone()).unwrap() {
+            let status = match self.insert_block_without_senders(block).unwrap() {
                 InsertPayloadOk::Inserted(BlockStatus::Valid(_)) |
                 InsertPayloadOk::AlreadySeen(BlockStatus::Valid(_)) => {
                     latest_valid_hash = Some(block_hash);