diff --git a/crates/brk_client/src/lib.rs b/crates/brk_client/src/lib.rs
index 7c8bfb67d..ab0a03702 100644
--- a/crates/brk_client/src/lib.rs
+++ b/crates/brk_client/src/lib.rs
@@ -8953,7 +8953,7 @@ pub struct BrkClient {
 
 impl BrkClient {
     /// Client version.
-    pub const VERSION: &'static str = "v0.3.0-beta.8";
+    pub const VERSION: &'static str = "v0.3.0-beta.9";
 
     /// Create a new client with the given base URL.
     pub fn new(base_url: impl Into<String>) -> Self {
@@ -9734,7 +9734,7 @@ impl BrkClient {
 
     /// Projected mempool blocks
     ///
-    /// Get projected blocks from the mempool for fee estimation.
+    /// Projected blocks for fee estimation. Block 0 reflects Bitcoin Core's actual next-block selection; blocks 1+ are a fee-tier approximation.
     ///
     /// *[Mempool.space docs](https://mempool.space/docs/api/rest#get-mempool-blocks-fees)*
     ///
@@ -9745,7 +9745,7 @@ impl BrkClient {
 
     /// Recommended fees
     ///
-    /// Get recommended fee rates for different confirmation targets.
+    /// Recommended fee rates by confirmation target.
     ///
     /// *[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees)*
     ///
@@ -9756,7 +9756,7 @@ impl BrkClient {
 
     /// Precise recommended fees
     ///
-    /// Get recommended fee rates with up to 3 decimal places.
+    /// Recommended fee rates with sub-integer precision.
     ///
     /// *[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees-precise)*
     ///
@@ -9778,10 +9778,10 @@ impl BrkClient {
 
     /// Mempool content hash
     ///
-    /// Returns an opaque `u64` that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.
+    /// Returns an opaque hash that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.
     ///
     /// Endpoint: `GET /api/mempool/hash`
-    pub fn get_mempool_hash(&self) -> Result<i64> {
+    pub fn get_mempool_hash(&self) -> Result<NextBlockHash> {
         self.base.get_json(&format!("/api/mempool/hash"))
     }
 
@@ -9829,6 +9829,24 @@ impl BrkClient {
         self.base.get_json(&format!("/api/v1/fullrbf/replacements"))
     }
 
+    /// Projected next block template
+    ///
+    /// Bitcoin Core's `getblocktemplate` selection: full transaction bodies in GBT order with aggregate stats. The returned `hash` is an opaque content token; pass it as `<hash>` on `/api/v1/mempool/block-template/diff/{hash}` to fetch deltas instead of refetching the whole template.
+    ///
+    /// Endpoint: `GET /api/v1/mempool/block-template`
+    pub fn get_block_template(&self) -> Result<BlockTemplate> {
+        self.base.get_json(&format!("/api/v1/mempool/block-template"))
+    }
+
+    /// Block template diff since hash
+    ///
+    /// Delta of the projected next block since `<hash>`. `added` carries full transaction bodies; `removed` is just txids. Returns `404` when `<hash>` has aged out of server history; clients should fall back to `/api/v1/mempool/block-template`.
+    ///
+    /// Endpoint: `GET /api/v1/mempool/block-template/diff/{hash}`
+    pub fn get_block_template_diff(&self, hash: NextBlockHash) -> Result<BlockTemplateDiff> {
+        self.base.get_json(&format!("/api/v1/mempool/block-template/diff/{hash}"))
+    }
+
     /// Live BTC/USD price
     ///
     /// Returns the current BTC/USD price in dollars, derived from on-chain round-dollar output patterns in the last 12 blocks plus mempool.
diff --git a/crates/brk_logger/src/lib.rs b/crates/brk_logger/src/lib.rs
index 428863fcc..722f6151d 100644
--- a/crates/brk_logger/src/lib.rs
+++ b/crates/brk_logger/src/lib.rs
@@ -23,6 +23,7 @@ const MAX_LOG_AGE_DAYS: u64 = 7;
 /// `*.txt` file older than 7 days is pruned on startup.
 pub fn init(dir: Option<&Path>) -> io::Result<()> {
     tracing_log::LogTracer::init().ok();
+    install_panic_hook();
 
     #[cfg(debug_assertions)]
     const DEFAULT_LEVEL: &str = "debug";
@@ -65,6 +66,24 @@ pub fn init(dir: Option<&Path>) -> io::Result<()> {
     Ok(())
 }
 
+fn install_panic_hook() {
+    std::panic::set_hook(Box::new(|info| {
+        let location = info
+            .location()
+            .map(|l| format!("{}:{}:{}", l.file(), l.line(), l.column()))
+            .unwrap_or_else(|| "unknown".to_string());
+        let payload = info.payload();
+        let msg = payload
+            .downcast_ref::<&str>()
+            .copied()
+            .map(str::to_owned)
+            .or_else(|| payload.downcast_ref::<String>().cloned())
+            .unwrap_or_else(|| "Box<dyn Any>".to_owned());
+        let backtrace = std::backtrace::Backtrace::capture();
+        tracing::error!(location, backtrace = %backtrace, "panic: {msg}");
+    }));
+}
+
 /// Register a hook that gets called for every log message.
 pub fn register_hook<F>(hook: F) -> Result<(), &'static str>
 where
diff --git a/crates/brk_mempool/src/lib.rs b/crates/brk_mempool/src/lib.rs
index 27c0bc2f5..028ffffd5 100644
--- a/crates/brk_mempool/src/lib.rs
+++ b/crates/brk_mempool/src/lib.rs
@@ -30,9 +30,11 @@ use std::{
 use brk_error::Result;
 use brk_rpc::Client;
 use brk_types::{
-    AddrBytes, AddrMempoolStats, FeeRate, MempoolInfo, MempoolRecentTx, OutpointPrefix, OutputType,
-    Sats, Timestamp, Transaction, TxOut, Txid, TxidPrefix, Vin, Vout,
+    AddrBytes, AddrMempoolStats, BlockTemplate, BlockTemplateDiff, FeeRate, MempoolBlock,
+    MempoolInfo, MempoolRecentTx, NextBlockHash, OutpointPrefix, OutputType, Sats, Timestamp,
+    Transaction, TxOut, Txid, TxidPrefix, Vin, Vout,
 };
+use rustc_hash::FxHashSet;
 use parking_lot::{RwLock, RwLockReadGuard};
 use tracing::error;
 
@@ -102,10 +104,58 @@ impl Mempool {
         self.snapshot().block_stats.clone()
     }
 
-    pub fn next_block_hash(&self) -> u64 {
+    pub fn next_block_hash(&self) -> NextBlockHash {
         self.snapshot().next_block_hash
     }
 
+    /// Full projected next block: Core's `getblocktemplate` selection
+    /// (block 0) with aggregate stats and full tx bodies in GBT order.
+    pub fn block_template(&self) -> BlockTemplate {
+        let snap = self.snapshot();
+        let stats = MempoolBlock::from(&snap.block_stats[0]);
+        let txids: Vec<Txid> = snap.blocks[0]
+            .iter()
+            .map(|idx| snap.txs[idx.as_usize()].txid)
+            .collect();
+        let transactions = self.collect_txs(&txids);
+        BlockTemplate {
+            hash: snap.next_block_hash,
+            stats,
+            transactions,
+        }
+    }
+
+    /// Delta of the projected next block since `since`. `None` when
+    /// `since` has aged out of the rebuilder's history (server should
+    /// 404 → client falls back to `block_template`). `removed` is just
+    /// txids; `added` carries full bodies so clients can patch their
+    /// local view in one round trip.
+    pub fn block_template_diff(&self, since: NextBlockHash) -> Option<BlockTemplateDiff> {
+        let past = self.0.rebuilder.historical_block0(since)?;
+        let snap = self.snapshot();
+        let current: FxHashSet<Txid> = snap.blocks[0]
+            .iter()
+            .map(|idx| snap.txs[idx.as_usize()].txid)
+            .collect();
+        let added_txids: Vec<Txid> = current.difference(&past).copied().collect();
+        let removed: Vec<Txid> = past.difference(&current).copied().collect();
+        let added = self.collect_txs(&added_txids);
+        Some(BlockTemplateDiff {
+            hash: snap.next_block_hash,
+            since,
+            added,
+            removed,
+        })
+    }
+
+    fn collect_txs(&self, txids: &[Txid]) -> Vec<Transaction> {
+        let state = self.read();
+        txids
+            .iter()
+            .filter_map(|txid| state.txs.get(txid).cloned())
+            .collect()
+    }
+
     pub fn addr_state_hash(&self, addr: &AddrBytes) -> u64 {
         self.read().addrs.stats_hash(addr)
     }
diff --git a/crates/brk_mempool/src/steps/rebuilder/mod.rs b/crates/brk_mempool/src/steps/rebuilder/mod.rs
index 1785f45c8..41607e59e 100644
--- a/crates/brk_mempool/src/steps/rebuilder/mod.rs
+++ b/crates/brk_mempool/src/steps/rebuilder/mod.rs
@@ -1,10 +1,13 @@
-use std::sync::{
-    Arc,
-    atomic::{AtomicBool, AtomicU64, Ordering},
+use std::{
+    collections::VecDeque,
+    sync::{
+        Arc,
+        atomic::{AtomicBool, AtomicU64, Ordering},
+    },
 };
 
 use brk_rpc::BlockTemplateTx;
-use brk_types::{FeeRate, TxidPrefix};
+use brk_types::{FeeRate, NextBlockHash, Txid, TxidPrefix};
 use parking_lot::RwLock;
 use rustc_hash::FxHashSet;
 
@@ -20,10 +23,13 @@ pub use brk_types::RecommendedFees;
 pub use snapshot::{BlockStats, SnapTx, Snapshot, TxIndex};
 
 const NUM_BLOCKS: usize = 8;
+const HISTORY: usize = 10;
 
 #[derive(Default)]
 pub struct Rebuilder {
     snapshot: RwLock<Arc<Snapshot>>,
+    /// Past block-0 txid sets keyed by `next_block_hash`, oldest first.
+    history: RwLock<VecDeque<(NextBlockHash, FxHashSet<Txid>)>>,
     dirty: AtomicBool,
     rebuild_count: AtomicU64,
     skip_clean: AtomicU64,
@@ -49,11 +55,38 @@ impl Rebuilder {
             self.skip_clean.fetch_add(1, Ordering::Relaxed);
             return;
         }
-        *self.snapshot.write() = Arc::new(Self::build_snapshot(lock, gbt, min_fee));
+        let snap = Self::build_snapshot(lock, gbt, min_fee);
+        let block0_set: FxHashSet<Txid> = snap.blocks[0]
+            .iter()
+            .map(|idx| snap.txs[idx.as_usize()].txid)
+            .collect();
+        let next_hash = snap.next_block_hash;
+        *self.snapshot.write() = Arc::new(snap);
+        self.push_history(next_hash, block0_set);
         self.dirty.store(false, Ordering::Release);
         self.rebuild_count.fetch_add(1, Ordering::Relaxed);
     }
 
+    fn push_history(&self, hash: NextBlockHash, set: FxHashSet<Txid>) {
+        let mut hist = self.history.write();
+        hist.retain(|(h, _)| *h != hash);
+        hist.push_back((hash, set));
+        while hist.len() > HISTORY {
+            hist.pop_front();
+        }
+    }
+
+    /// Past block-0 txid set for `hash`, or `None` if it has aged out
+    /// (or was never seen). Used by `block_template_diff` to decide
+    /// 200 vs 404.
+    pub fn historical_block0(&self, hash: NextBlockHash) -> Option<FxHashSet<Txid>> {
+        self.history
+            .read()
+            .iter()
+            .find(|(h, _)| *h == hash)
+            .map(|(_, set)| set.clone())
+    }
+
     pub fn rebuild_count(&self) -> u64 {
         self.rebuild_count.load(Ordering::Relaxed)
     }
diff --git a/crates/brk_mempool/src/steps/rebuilder/snapshot/mod.rs b/crates/brk_mempool/src/steps/rebuilder/snapshot/mod.rs
index 79e2e5465..57f5647df 100644
--- a/crates/brk_mempool/src/steps/rebuilder/snapshot/mod.rs
+++ b/crates/brk_mempool/src/steps/rebuilder/snapshot/mod.rs
@@ -11,7 +11,7 @@ pub use tx_index::TxIndex;
 
 use std::hash::{DefaultHasher, Hash, Hasher};
 
-use brk_types::{FeeRate, RecommendedFees, TxidPrefix};
+use brk_types::{FeeRate, NextBlockHash, RecommendedFees, TxidPrefix};
 
 use fees::Fees;
 
@@ -30,7 +30,7 @@ pub struct Snapshot {
     pub fees: RecommendedFees,
     /// Content hash of the projected next block. Same value as the
     /// mempool ETag.
-    pub next_block_hash: u64,
+    pub next_block_hash: NextBlockHash,
     /// Per-snapshot `TxidPrefix -> TxIndex` index, so live queries can
     /// resolve a prefix to the snapshot's compact index without
     /// re-walking `txs`. Built once by `builder::build_txs` and reused
@@ -70,13 +70,13 @@ impl Snapshot {
         }
     }
 
-    fn hash_next_block(blocks: &[Vec<TxIndex>]) -> u64 {
+    fn hash_next_block(blocks: &[Vec<TxIndex>]) -> NextBlockHash {
         let Some(block) = blocks.first() else {
-            return 0;
+            return NextBlockHash::ZERO;
         };
         let mut hasher = DefaultHasher::new();
         block.hash(&mut hasher);
-        hasher.finish()
+        NextBlockHash::new(hasher.finish())
     }
 
     pub fn tx(&self, idx: TxIndex) -> Option<&SnapTx> {
diff --git a/crates/brk_mempool/src/steps/rebuilder/snapshot/stats.rs b/crates/brk_mempool/src/steps/rebuilder/snapshot/stats.rs
index bbde8c9ba..954a30b1f 100644
--- a/crates/brk_mempool/src/steps/rebuilder/snapshot/stats.rs
+++ b/crates/brk_mempool/src/steps/rebuilder/snapshot/stats.rs
@@ -1,4 +1,4 @@
-use brk_types::{FeeRate, Sats, VSize, get_weighted_percentile};
+use brk_types::{FeeRate, MempoolBlock, Sats, VSize, get_weighted_percentile};
 
 use super::{SnapTx, TxIndex};
 
@@ -83,3 +83,9 @@ impl BlockStats {
         self.fee_range[3]
     }
 }
+
+impl From<&BlockStats> for MempoolBlock {
+    fn from(s: &BlockStats) -> Self {
+        Self::new(s.tx_count, s.total_size, s.total_vsize, s.total_fee, s.fee_range)
+    }
+}
diff --git a/crates/brk_query/src/impl/mempool.rs b/crates/brk_query/src/impl/mempool.rs
index 885dd4ed1..b9e68fe42 100644
--- a/crates/brk_query/src/impl/mempool.rs
+++ b/crates/brk_query/src/impl/mempool.rs
@@ -2,9 +2,9 @@ use crate::Query;
 use brk_error::{Error, Result};
 use brk_mempool::{Mempool, PrevoutResolver, RbfForTx, RbfNode};
 use brk_types::{
-    CheckedSub, FeeRate, MempoolBlock, MempoolInfo, MempoolRecentTx, OutputType, RbfResponse,
-    RbfTx, RecommendedFees, ReplacementNode, Sats, Timestamp, TxOut, TxOutIndex, Txid, TxidPrefix,
-    TypeIndex,
+    BlockTemplate, BlockTemplateDiff, CheckedSub, FeeRate, MempoolBlock, MempoolInfo,
+    MempoolRecentTx, NextBlockHash, OutputType, RbfResponse, RbfTx, RecommendedFees,
+    ReplacementNode, Sats, Timestamp, TxOut, TxOutIndex, Txid, TxidPrefix, TypeIndex,
 };
 
 const RECENT_REPLACEMENTS_LIMIT: usize = 25;
@@ -28,23 +28,7 @@ impl Query {
 
     pub fn mempool_blocks(&self) -> Result<Vec<MempoolBlock>> {
         let mempool = self.require_mempool()?;
-
-        let block_stats = mempool.block_stats();
-
-        let blocks = block_stats
-            .into_iter()
-            .map(|stats| {
-                MempoolBlock::new(
-                    stats.tx_count,
-                    stats.total_size,
-                    stats.total_vsize,
-                    stats.total_fee,
-                    stats.fee_range,
-                )
-            })
-            .collect();
-
-        Ok(blocks)
+        Ok(mempool.block_stats().iter().map(MempoolBlock::from).collect())
     }
 
     /// Indexer-backed resolver for confirmed-parent prevouts. Pass
@@ -172,7 +156,22 @@ impl Query {
 
     /// Content hash of the projected next block. Same value as the
     /// mempool ETag. Polling lets monitors detect a stalled sync.
-    pub fn mempool_hash(&self) -> Result<u64> {
+    pub fn mempool_hash(&self) -> Result<NextBlockHash> {
         Ok(self.require_mempool()?.next_block_hash())
     }
+
+    /// Full projected next block (Core's `getblocktemplate` selection)
+    /// with stats and full tx bodies in GBT order.
+    pub fn block_template(&self) -> Result<BlockTemplate> {
+        Ok(self.require_mempool()?.block_template())
+    }
+
+    /// Delta of the projected next block since `since`. `NotFound`
+    /// when `since` has aged out (client should fall back to
+    /// `block_template`).
+    pub fn block_template_diff(&self, since: NextBlockHash) -> Result<BlockTemplateDiff> {
+        self.require_mempool()?
+            .block_template_diff(since)
+            .ok_or_else(|| Error::NotFound(format!("unknown since hash: {since}")))
+    }
 }
diff --git a/crates/brk_rpc/src/methods.rs b/crates/brk_rpc/src/methods.rs
index 4c13bad75..daa6fd422 100644
--- a/crates/brk_rpc/src/methods.rs
+++ b/crates/brk_rpc/src/methods.rs
@@ -373,22 +373,25 @@ impl Client {
 
     /// Verbose mempool listing + Core's projected next block + live
     /// `mempoolminfee`, fetched in a single bitcoind round-trip.
-    /// Validates that every GBT txid is present in the verbose listing
-    /// and returns `Ok(None)` on mismatch so the caller can skip the
-    /// cycle (within-batch races inside bitcoind are rare; persistent
-    /// drift is bug-shaped). Other failures bubble up as `Err`.
+    /// `getblocktemplate` runs first so that any tx arriving between
+    /// the two intra-batch calls lands in the verbose listing only,
+    /// preserving GBT ⊆ verbose for the common race. Validates that
+    /// every GBT txid is present in the verbose listing and returns
+    /// `Ok(None)` on mismatch so the caller can skip the cycle:
+    /// republishing block 0 with missing txids would diverge from
+    /// Core's exact selection. Other failures bubble up as `Err`.
     pub fn fetch_mempool_state(&self) -> Result<Option<MempoolState>> {
         let requests: [(&str, Vec<Value>); 3] = [
-            ("getrawmempool", vec![Value::Bool(true)]),
             (
                 "getblocktemplate",
                 vec![serde_json::json!({ "rules": ["segwit"] })],
             ),
+            ("getrawmempool", vec![Value::Bool(true)]),
             ("getmempoolinfo", vec![]),
         ];
         let mut out = self.0.call_mixed_batch(&requests)?.into_iter();
-        let verbose_raw = out.next().ok_or(Error::Internal("missing verbose"))??;
         let gbt_raw = out.next().ok_or(Error::Internal("missing gbt"))??;
+        let verbose_raw = out.next().ok_or(Error::Internal("missing verbose"))??;
         let info_raw = out.next().ok_or(Error::Internal("missing mempoolinfo"))??;
 
         let verbose: FxHashMap<String, VerboseEntryRaw> = serde_json::from_str(verbose_raw.get())?;
diff --git a/crates/brk_server/src/api/fees.rs b/crates/brk_server/src/api/fees.rs
index 44b363296..d2ea56b78 100644
--- a/crates/brk_server/src/api/fees.rs
+++ b/crates/brk_server/src/api/fees.rs
@@ -27,7 +27,7 @@ impl FeesRoutes for ApiRouter<AppState> {
                     op.id("get_mempool_blocks")
                         .fees_tag()
                         .summary("Projected mempool blocks")
-                        .description("Get projected blocks from the mempool for fee estimation.\n\n*[Mempool.space docs](https://mempool.space/docs/api/rest#get-mempool-blocks-fees)*")
+                        .description("Projected blocks for fee estimation. Block 0 reflects Bitcoin Core's actual next-block selection; blocks 1+ are a fee-tier approximation.\n\n*[Mempool.space docs](https://mempool.space/docs/api/rest#get-mempool-blocks-fees)*")
                         .json_response::<Vec<MempoolBlock>>()
                         .not_modified()
                         .server_error()
@@ -48,7 +48,7 @@ impl FeesRoutes for ApiRouter<AppState> {
                     op.id("get_recommended_fees")
                         .fees_tag()
                         .summary("Recommended fees")
-                        .description("Get recommended fee rates for different confirmation targets.\n\n*[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees)*")
+                        .description("Recommended fee rates by confirmation target.\n\n*[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees)*")
                         .json_response::<RecommendedFees>()
                         .not_modified()
                         .server_error()
@@ -69,7 +69,7 @@ impl FeesRoutes for ApiRouter<AppState> {
                     op.id("get_precise_fees")
                         .fees_tag()
                         .summary("Precise recommended fees")
-                        .description("Get recommended fee rates with up to 3 decimal places.\n\n*[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees-precise)*")
+                        .description("Recommended fee rates with sub-integer precision.\n\n*[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees-precise)*")
                         .json_response::<RecommendedFees>()
                         .not_modified()
                         .server_error()
diff --git a/crates/brk_server/src/api/mempool.rs b/crates/brk_server/src/api/mempool.rs
index b53b7d77e..2f809a546 100644
--- a/crates/brk_server/src/api/mempool.rs
+++ b/crates/brk_server/src/api/mempool.rs
@@ -1,11 +1,18 @@
 use aide::axum::{ApiRouter, routing::get_with};
 use axum::{
-    extract::State,
+    extract::{Path, State},
     http::{HeaderMap, Uri},
 };
-use brk_types::{Dollars, MempoolInfo, MempoolRecentTx, ReplacementNode, Txid};
+use brk_types::{
+    BlockTemplate, BlockTemplateDiff, Dollars, MempoolInfo, MempoolRecentTx, NextBlockHash,
+    ReplacementNode, Txid,
+};
 
-use crate::{AppState, extended::TransformResponseExtended, params::Empty};
+use crate::{
+    AppState,
+    extended::TransformResponseExtended,
+    params::{Empty, NextBlockHashParam},
+};
 
 pub trait MempoolRoutes {
     fn add_mempool_routes(self) -> Self;
@@ -44,8 +51,8 @@ impl MempoolRoutes for ApiRouter<AppState> {
                     op.id("get_mempool_hash")
                         .mempool_tag()
                         .summary("Mempool content hash")
-                        .description("Returns an opaque `u64` that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.")
-                        .json_response::<u64>()
+                        .description("Returns an opaque hash that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.")
+                        .json_response::<NextBlockHash>()
                         .not_modified()
                         .server_error()
                 },
@@ -131,6 +138,53 @@ impl MempoolRoutes for ApiRouter<AppState> {
                 },
             ),
         )
+        .api_route(
+            "/api/v1/mempool/block-template",
+            get_with(
+                async |uri: Uri, headers: HeaderMap, _: Empty, State(state): State<AppState>| {
+                    state
+                        .respond_json(&headers, state.mempool_strategy(), &uri, |q| {
+                            q.block_template()
+                        })
+                        .await
+                },
+                |op| {
+                    op.id("get_block_template")
+                        .mempool_tag()
+                        .summary("Projected next block template")
+                        .description("Bitcoin Core's `getblocktemplate` selection: full transaction bodies in GBT order with aggregate stats. The returned `hash` is an opaque content token; pass it as `<hash>` on `/api/v1/mempool/block-template/diff/{hash}` to fetch deltas instead of refetching the whole template.")
+                        .json_response::<BlockTemplate>()
+                        .not_modified()
+                        .server_error()
+                },
+            ),
+        )
+        .api_route(
+            "/api/v1/mempool/block-template/diff/{hash}",
+            get_with(
+                async |uri: Uri,
+                       headers: HeaderMap,
+                       Path(path): Path<NextBlockHashParam>,
+                       _: Empty,
+                       State(state): State<AppState>| {
+                    state
+                        .respond_json(&headers, state.mempool_strategy(), &uri, move |q| {
+                            q.block_template_diff(path.hash)
+                        })
+                        .await
+                },
+                |op| {
+                    op.id("get_block_template_diff")
+                        .mempool_tag()
+                        .summary("Block template diff since hash")
+                        .description("Delta of the projected next block since `<hash>`. `added` carries full transaction bodies; `removed` is just txids. Returns `404` when `<hash>` has aged out of server history; clients should fall back to `/api/v1/mempool/block-template`.")
+                        .json_response::<BlockTemplateDiff>()
+                        .not_modified()
+                        .not_found()
+                        .server_error()
+                },
+            ),
+        )
         .api_route(
             "/api/mempool/price",
             get_with(
diff --git a/crates/brk_server/src/lib.rs b/crates/brk_server/src/lib.rs
index cf18becc3..09777101d 100644
--- a/crates/brk_server/src/lib.rs
+++ b/crates/brk_server/src/lib.rs
@@ -102,9 +102,11 @@ impl Server {
         let response_time_layer = axum::middleware::from_fn(
             async |request: Request<Body>, next: Next| -> Response<Body> {
                 let uri = request.uri().clone();
+                let method = request.method().clone();
                 let start = Instant::now();
                 let mut response = next.run(request).await;
                 response.extensions_mut().insert(uri);
+                response.extensions_mut().insert(method);
                 response.headers_mut().insert(
                     "X-Response-Time",
                     format!("{}us", start.elapsed().as_micros())
@@ -182,14 +184,19 @@ impl Server {
             .on_response(
                 |response: &Response<Body>, latency: Duration, _: &tracing::Span| {
                     let status = response.status().as_u16();
-                    let unknown = Uri::from_static("/unknown");
-                    let uri = response.extensions().get::<Uri>().unwrap_or(&unknown);
+                    let unknown_uri = Uri::from_static("/unknown");
+                    let unknown_method = axum::http::Method::default();
+                    let uri = response.extensions().get::<Uri>().unwrap_or(&unknown_uri);
+                    let method = response
+                        .extensions()
+                        .get::<axum::http::Method>()
+                        .unwrap_or(&unknown_method);
                     match response.status() {
-                        StatusCode::OK => info!(status, %uri, ?latency),
+                        StatusCode::OK => info!(%method, status, %uri, ?latency),
                         StatusCode::NOT_MODIFIED
                         | StatusCode::TEMPORARY_REDIRECT
-                        | StatusCode::PERMANENT_REDIRECT => info!(status, %uri, ?latency),
-                        _ => error!(status, %uri, ?latency),
+                        | StatusCode::PERMANENT_REDIRECT => info!(%method, status, %uri, ?latency),
+                        _ => error!(%method, status, %uri, ?latency),
                     }
                 },
             )
@@ -209,8 +216,6 @@ impl Server {
         let router = router
             .with_state(state)
             .merge(website_router)
-            .layer(response_time_layer)
-            .layer(trace_layer)
             .layer(TimeoutLayer::with_status_code(
                 StatusCode::GATEWAY_TIMEOUT,
                 REQUEST_TIMEOUT,
@@ -242,7 +247,9 @@ impl Server {
                     .or_else(|| panic.downcast_ref::<&str>().copied())
                     .unwrap_or("Unknown panic");
                 Error::internal(msg).into_response()
-            }));
+            }))
+            .layer(response_time_layer)
+            .layer(trace_layer);
 
         let (listener, port) = match port {
             Some(port) => {
diff --git a/crates/brk_server/src/params/mod.rs b/crates/brk_server/src/params/mod.rs
index 2a00f1e1d..804109e75 100644
--- a/crates/brk_server/src/params/mod.rs
+++ b/crates/brk_server/src/params/mod.rs
@@ -6,6 +6,7 @@ mod blockhash_start_index;
 mod blockhash_tx_index;
 mod empty;
 mod height_param;
+mod next_block_hash_param;
 mod pool_slug_param;
 mod series_param;
 mod time_period_param;
@@ -25,6 +26,7 @@ pub use blockhash_start_index::*;
 pub use blockhash_tx_index::*;
 pub use empty::*;
 pub use height_param::*;
+pub use next_block_hash_param::*;
 pub use pool_slug_param::*;
 pub use series_param::*;
 pub use time_period_param::*;
diff --git a/crates/brk_server/src/params/next_block_hash_param.rs b/crates/brk_server/src/params/next_block_hash_param.rs
new file mode 100644
index 000000000..8f58fbaa2
--- /dev/null
+++ b/crates/brk_server/src/params/next_block_hash_param.rs
@@ -0,0 +1,10 @@
+use schemars::JsonSchema;
+use serde::Deserialize;
+
+use brk_types::NextBlockHash;
+
+/// `since` hash for `/api/v1/mining/block-template/diff/{hash}`.
+#[derive(Deserialize, JsonSchema)]
+pub struct NextBlockHashParam {
+    pub hash: NextBlockHash,
+}
diff --git a/crates/brk_server/src/state.rs b/crates/brk_server/src/state.rs
index b000ab15e..d2949c10c 100644
--- a/crates/brk_server/src/state.rs
+++ b/crates/brk_server/src/state.rs
@@ -124,7 +124,7 @@ impl AppState {
             if let Some(mempool) = q.mempool()
                 && mempool.contains_txid(txid)
             {
-                return CacheStrategy::MempoolHash(mempool.next_block_hash());
+                return CacheStrategy::MempoolHash(mempool.next_block_hash().into());
             }
             if let Ok((_, height)) = q.resolve_tx(txid)
                 && let Ok(block_hash) = q.block_hash_by_height(height)
@@ -136,7 +136,7 @@ impl AppState {
     }
 
     pub fn mempool_strategy(&self) -> CacheStrategy {
-        let hash = self.sync(|q| q.mempool().map(|m| m.next_block_hash()).unwrap_or(0));
+        let hash = self.sync(|q| q.mempool().map(|m| m.next_block_hash().into()).unwrap_or(0));
         CacheStrategy::MempoolHash(hash)
     }
 
diff --git a/crates/brk_types/src/block_template.rs b/crates/brk_types/src/block_template.rs
new file mode 100644
index 000000000..e568de0bd
--- /dev/null
+++ b/crates/brk_types/src/block_template.rs
@@ -0,0 +1,21 @@
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+use crate::{MempoolBlock, NextBlockHash, Transaction};
+
+/// Projected next-block contents from Bitcoin Core's `getblocktemplate`
+/// (block 0 of the snapshot). Returned by
+/// `GET /api/v1/mining/block-template`.
+#[derive(Debug, Clone, Serialize, Deserialize, JsonSchema)]
+#[serde(rename_all = "camelCase")]
+pub struct BlockTemplate {
+    /// Pass back as `<hash>` on
+    /// `/api/v1/mining/block-template/diff/{hash}` to fetch deltas.
+    pub hash: NextBlockHash,
+
+    /// Aggregate stats for this block (size, vsize, fee range, ...).
+    pub stats: MempoolBlock,
+
+    /// Full transaction bodies in `getblocktemplate` order.
+    pub transactions: Vec<Transaction>,
+}
diff --git a/crates/brk_types/src/block_template_diff.rs b/crates/brk_types/src/block_template_diff.rs
new file mode 100644
index 000000000..7df21ba28
--- /dev/null
+++ b/crates/brk_types/src/block_template_diff.rs
@@ -0,0 +1,25 @@
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+use crate::{NextBlockHash, Transaction, Txid};
+
+/// Delta between the current `getblocktemplate` projection and a prior
+/// one identified by `since`. Returned by
+/// `GET /api/v1/mining/block-template/diff/{hash}`.
+#[derive(Debug, Clone, Serialize, Deserialize, JsonSchema)]
+#[serde(rename_all = "camelCase")]
+pub struct BlockTemplateDiff {
+    /// Current next-block hash. Use as `since` on the next diff call.
+    pub hash: NextBlockHash,
+
+    /// Echoed prior hash the diff was computed against.
+    pub since: NextBlockHash,
+
+    /// Full bodies of transactions that joined the projected next
+    /// block since `since`.
+    pub added: Vec<Transaction>,
+
+    /// Txids that left the projected next block since `since`
+    /// (confirmed, evicted, replaced, or pushed past block 0).
+    pub removed: Vec<Txid>,
+}
diff --git a/crates/brk_types/src/lib.rs b/crates/brk_types/src/lib.rs
index 2cc13d60b..bc708b264 100644
--- a/crates/brk_types/src/lib.rs
+++ b/crates/brk_types/src/lib.rs
@@ -80,6 +80,8 @@ mod hour4;
 mod index;
 mod index_info;
 mod limit;
+mod block_template;
+mod block_template_diff;
 mod mempool_block;
 mod mempool_entry_info;
 mod mempool_info;
@@ -90,6 +92,7 @@ mod minute30;
 mod month1;
 mod month3;
 mod month6;
+mod next_block_hash;
 mod ohlc;
 mod op_return_index;
 mod option_ext;
@@ -225,6 +228,8 @@ pub use block_rewards_entry::*;
 pub use block_size_entry::*;
 pub use block_sizes_weights::*;
 pub use block_status::*;
+pub use block_template::*;
+pub use block_template_diff::*;
 pub use block_timestamp::*;
 pub use block_tx_index::*;
 pub use block_weight_entry::*;
@@ -283,6 +288,7 @@ pub use minute30::*;
 pub use month1::*;
 pub use month3::*;
 pub use month6::*;
+pub use next_block_hash::*;
 pub use ohlc::*;
 pub use op_return_index::*;
 pub use option_ext::*;
diff --git a/crates/brk_types/src/next_block_hash.rs b/crates/brk_types/src/next_block_hash.rs
new file mode 100644
index 000000000..84c54903f
--- /dev/null
+++ b/crates/brk_types/src/next_block_hash.rs
@@ -0,0 +1,51 @@
+use std::fmt;
+
+use schemars::JsonSchema;
+use serde::{Deserialize, Serialize};
+
+/// Content hash of the projected next block (block 0 of the mempool
+/// snapshot). Same value as the mempool ETag. Opaque token: pass back
+/// as `since` on `/api/v1/mining/block-template/diff/{hash}` to fetch
+/// deltas.
+#[derive(
+    Debug,
+    Default,
+    Clone,
+    Copy,
+    PartialEq,
+    Eq,
+    Hash,
+    PartialOrd,
+    Ord,
+    Serialize,
+    Deserialize,
+    JsonSchema,
+)]
+#[serde(transparent)]
+pub struct NextBlockHash(u64);
+
+impl NextBlockHash {
+    pub const ZERO: Self = Self(0);
+
+    pub const fn new(value: u64) -> Self {
+        Self(value)
+    }
+}
+
+impl fmt::Display for NextBlockHash {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+impl From<u64> for NextBlockHash {
+    fn from(value: u64) -> Self {
+        Self(value)
+    }
+}
+
+impl From<NextBlockHash> for u64 {
+    fn from(value: NextBlockHash) -> Self {
+        value.0
+    }
+}
diff --git a/modules/brk-client/index.js b/modules/brk-client/index.js
index 647583f8a..91cb73e9a 100644
--- a/modules/brk-client/index.js
+++ b/modules/brk-client/index.js
@@ -281,6 +281,30 @@ Matches mempool.space/bitcoin-cli behavior.
  * @property {(Height|null)=} height - Block height (only if in best chain)
  * @property {(BlockHash|null)=} nextBest - Hash of the next block in the best chain (null if tip)
  */
+/**
+ * Projected next-block contents from Bitcoin Core's `getblocktemplate`
+ * (block 0 of the snapshot). Returned by
+ * `GET /api/v1/mining/block-template`.
+ *
+ * @typedef {Object} BlockTemplate
+ * @property {NextBlockHash} hash - Pass back as `<hash>` on
+`/api/v1/mining/block-template/diff/{hash}` to fetch deltas.
+ * @property {MempoolBlock} stats - Aggregate stats for this block (size, vsize, fee range, ...).
+ * @property {Transaction[]} transactions - Full transaction bodies in `getblocktemplate` order.
+ */
+/**
+ * Delta between the current `getblocktemplate` projection and a prior
+ * one identified by `since`. Returned by
+ * `GET /api/v1/mining/block-template/diff/{hash}`.
+ *
+ * @typedef {Object} BlockTemplateDiff
+ * @property {NextBlockHash} hash - Current next-block hash. Use as `since` on the next diff call.
+ * @property {NextBlockHash} since - Echoed prior hash the diff was computed against.
+ * @property {Transaction[]} added - Full bodies of transactions that joined the projected next
+block since `since`.
+ * @property {Txid[]} removed - Txids that left the projected next block since `since`
+(confirmed, evicted, replaced, or pushed past block 0).
+ */
 /**
  * Block information returned for timestamp queries
  *
@@ -711,6 +735,20 @@ ancestors and no descendants (matches mempool.space).
 /** @typedef {number} Month1 */
 /** @typedef {number} Month3 */
 /** @typedef {number} Month6 */
+/**
+ * Content hash of the projected next block (block 0 of the mempool
+ * snapshot). Same value as the mempool ETag. Opaque token: pass back
+ * as `since` on `/api/v1/mining/block-template/diff/{hash}` to fetch
+ * deltas.
+ *
+ * @typedef {number} NextBlockHash
+ */
+/**
+ * `since` hash for `/api/v1/mining/block-template/diff/{hash}`.
+ *
+ * @typedef {Object} NextBlockHashParam
+ * @property {NextBlockHash} hash
+ */
 /**
  * OHLC (Open, High, Low, Close) data in cents
  *
@@ -11620,7 +11658,7 @@ class BrkClient extends BrkClientBase {
   /**
    * Projected mempool blocks
    *
-   * Get projected blocks from the mempool for fee estimation.
+   * Projected blocks for fee estimation. Block 0 reflects Bitcoin Core's actual next-block selection; blocks 1+ are a fee-tier approximation.
    *
    * *[Mempool.space docs](https://mempool.space/docs/api/rest#get-mempool-blocks-fees)*
    *
@@ -11636,7 +11674,7 @@ class BrkClient extends BrkClientBase {
   /**
    * Recommended fees
    *
-   * Get recommended fee rates for different confirmation targets.
+   * Recommended fee rates by confirmation target.
    *
    * *[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees)*
    *
@@ -11652,7 +11690,7 @@ class BrkClient extends BrkClientBase {
   /**
    * Precise recommended fees
    *
-   * Get recommended fee rates with up to 3 decimal places.
+   * Recommended fee rates with sub-integer precision.
    *
    * *[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees-precise)*
    *
@@ -11684,11 +11722,11 @@ class BrkClient extends BrkClientBase {
   /**
    * Mempool content hash
    *
-   * Returns an opaque `u64` that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.
+   * Returns an opaque hash that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.
    *
    * Endpoint: `GET /api/mempool/hash`
-   * @param {{ signal?: AbortSignal, onValue?: (value: number) => void }} [options]
-   * @returns {Promise<number>}
+   * @param {{ signal?: AbortSignal, onValue?: (value: NextBlockHash) => void }} [options]
+   * @returns {Promise<NextBlockHash>}
    */
   async getMempoolHash({ signal, onValue } = {}) {
     const path = `/api/mempool/hash`;
@@ -11759,6 +11797,36 @@ class BrkClient extends BrkClientBase {
     return this.getJson(path, { signal, onValue });
   }
 
+  /**
+   * Projected next block template
+   *
+   * Bitcoin Core's `getblocktemplate` selection: full transaction bodies in GBT order with aggregate stats. The returned `hash` is an opaque content token; pass it as `<hash>` on `/api/v1/mempool/block-template/diff/{hash}` to fetch deltas instead of refetching the whole template.
+   *
+   * Endpoint: `GET /api/v1/mempool/block-template`
+   * @param {{ signal?: AbortSignal, onValue?: (value: BlockTemplate) => void }} [options]
+   * @returns {Promise<BlockTemplate>}
+   */
+  async getBlockTemplate({ signal, onValue } = {}) {
+    const path = `/api/v1/mempool/block-template`;
+    return this.getJson(path, { signal, onValue });
+  }
+
+  /**
+   * Block template diff since hash
+   *
+   * Delta of the projected next block since `<hash>`. `added` carries full transaction bodies; `removed` is just txids. Returns `404` when `<hash>` has aged out of server history; clients should fall back to `/api/v1/mempool/block-template`.
+   *
+   * Endpoint: `GET /api/v1/mempool/block-template/diff/{hash}`
+   *
+   * @param {NextBlockHash} hash
+   * @param {{ signal?: AbortSignal, onValue?: (value: BlockTemplateDiff) => void }} [options]
+   * @returns {Promise<BlockTemplateDiff>}
+   */
+  async getBlockTemplateDiff(hash, { signal, onValue } = {}) {
+    const path = `/api/v1/mempool/block-template/diff/${hash}`;
+    return this.getJson(path, { signal, onValue });
+  }
+
   /**
    * Live BTC/USD price
    *
diff --git a/packages/brk_client/brk_client/__init__.py b/packages/brk_client/brk_client/__init__.py
index d730161a4..8bfbc5eee 100644
--- a/packages/brk_client/brk_client/__init__.py
+++ b/packages/brk_client/brk_client/__init__.py
@@ -68,6 +68,37 @@ BlockHash = str
 # Position of a transaction within a single block (0 = coinbase).
 # Distinct from `TxIndex`, which is the chain-wide global tx index.
 BlockTxIndex = int
+# Content hash of the projected next block (block 0 of the mempool
+# snapshot). Same value as the mempool ETag. Opaque token: pass back
+# as `since` on `/api/v1/mining/block-template/diff/{hash}` to fetch
+# deltas.
+NextBlockHash = int
+# Transaction locktime. Values below 500,000,000 are interpreted as block heights; values at or above are Unix timestamps.
+RawLockTime = int
+# BIP-141 sigop cost. The block-level budget is 80,000, so a `u32`
+# fits a single tx's count with room to spare.
+# 
+# Witness sigops count as 1; legacy and P2SH-redeem sigops count as 4.
+# Five vbytes per sigop is the policy adjustment Core applies in
+# `nSigOpCost` to discourage sigop-heavy txs (`max(weight/4, sigops*5)`).
+SigOps = int
+# Index of the output being spent in the previous transaction
+Vout = int
+# Transaction witness: a stack of byte arrays, one per witness item.
+# 
+# Wraps `bitcoin::Witness` (single-buffer layout with offsets, much
+# more compact than `Vec<Vec<u8>>`). Serializes as a JSON array of
+# hex strings - the format used by Bitcoin Core REST and mempool.space
+# and matching brk's `script_sig: ScriptBuf` (bytes internally, hex
+# on the wire).
+Witness = List[str]
+# Chain-wide transaction index (0 = the genesis coinbase). For an
+# in-block position, use `BlockTxIndex` instead.
+TxIndex = int
+# Raw transaction version (i32) from Bitcoin protocol.
+# Unlike TxVersion (u8, indexed), this preserves non-standard values
+# used in coinbase txs for miner signaling/branding.
+TxVersionRaw = int
 # Unsigned cents (u64) - for values that should never be negative.
 # Used for invested capital, realized cap, etc.
 Cents = int
@@ -106,13 +137,6 @@ UrpdAggregation = Literal["raw", "lin200", "lin500", "lin1000", "log10", "log50"
 # Position of a transaction inside a `CpfpCluster.txs` array. Cluster-local,
 # has no meaning outside the enclosing cluster.
 CpfpClusterTxIndex = int
-# BIP-141 sigop cost. The block-level budget is 80,000, so a `u32`
-# fits a single tx's count with room to spare.
-# 
-# Witness sigops count as 1; legacy and P2SH-redeem sigops count as 4.
-# Five vbytes per sigop is the policy adjustment Core applies in
-# `nSigOpCost` to discourage sigop-heavy txs (`max(weight/4, sigops*5)`).
-SigOps = int
 # Virtual size in vbytes (weight / 4, rounded up). Max block vsize is ~1,000,000 vB.
 VSize = int
 # Date in YYYYMMDD format stored as u32
@@ -179,8 +203,6 @@ P2WPKHAddrIndex = TypeIndex
 P2WPKHBytes = U8x20
 P2WSHAddrIndex = TypeIndex
 P2WSHBytes = U8x32
-# Transaction locktime. Values below 500,000,000 are interpreted as block heights; values at or above are Unix timestamps.
-RawLockTime = int
 # Fractional satoshis (f64) - for representing USD prices in sats
 # 
 # Formula: `sats_fract = usd_value * 100_000_000 / btc_price`
@@ -219,23 +241,6 @@ StoredU64 = int
 # Used to specify the lookback window for pool statistics, hashrate calculations,
 # and other time-based mining series.
 TimePeriod = Literal["24h", "3d", "1w", "1m", "3m", "6m", "1y", "2y", "3y", "all"]
-# Index of the output being spent in the previous transaction
-Vout = int
-# Transaction witness: a stack of byte arrays, one per witness item.
-# 
-# Wraps `bitcoin::Witness` (single-buffer layout with offsets, much
-# more compact than `Vec<Vec<u8>>`). Serializes as a JSON array of
-# hex strings - the format used by Bitcoin Core REST and mempool.space
-# and matching brk's `script_sig: ScriptBuf` (bytes internally, hex
-# on the wire).
-Witness = List[str]
-# Chain-wide transaction index (0 = the genesis coinbase). For an
-# in-block position, use `BlockTxIndex` instead.
-TxIndex = int
-# Raw transaction version (i32) from Bitcoin protocol.
-# Unlike TxVersion (u8, indexed), this preserves non-standard values
-# used in coinbase txs for miner signaling/branding.
-TxVersionRaw = int
 # Hierarchical tree node for organizing series into categories
 TreeNode = Union[dict[str, "TreeNode"], "SeriesLeafWithSchema"]
 TxInIndex = int
@@ -640,6 +645,142 @@ class BlockStatus(TypedDict):
     height: Union[Height, None]
     next_best: Union[BlockHash, None]
 
+class MempoolBlock(TypedDict):
+    """
+    Block info in a mempool.space like format for fee estimation.
+
+    Attributes:
+        blockSize: Total serialized block size in bytes (witness + non-witness).
+        blockVSize: Total block virtual size in vbytes
+        nTx: Number of transactions in the projected block
+        totalFees: Total fees in satoshis
+        medianFee: Median fee rate in sat/vB
+        feeRange: Fee rate range: [min, 10%, 25%, 50%, 75%, 90%, max]
+    """
+    blockSize: int
+    blockVSize: float
+    nTx: int
+    totalFees: Sats
+    medianFee: FeeRate
+    feeRange: List[FeeRate]
+
+class TxOut(TypedDict):
+    """
+    Transaction output
+
+    Attributes:
+        scriptpubkey: Script pubkey (locking script)
+        value: Value of the output in satoshis
+    """
+    scriptpubkey: str
+    value: Sats
+
+class TxIn(TypedDict):
+    """
+    Transaction input
+
+    Attributes:
+        txid: Transaction ID of the output being spent
+        vout: Output index being spent (u16: coinbase is 65535, mempool.space uses u32: 4294967295)
+        prevout: Information about the previous output being spent
+        scriptsig: Signature script (hex, for non-SegWit inputs)
+        scriptsig_asm: Signature script in assembly format
+        witness: Witness data (stack items, present for SegWit inputs; hex-encoded on the wire)
+        is_coinbase: Whether this input is a coinbase (block reward) input
+        sequence: Input sequence number
+        inner_redeemscript_asm: Inner redeemscript in assembly (for P2SH-wrapped SegWit: scriptsig + witness both present)
+        inner_witnessscript_asm: Inner witnessscript in assembly (for P2WSH: last witness item decoded as script)
+    """
+    txid: Txid
+    vout: Vout
+    prevout: Union[TxOut, None]
+    scriptsig: str
+    scriptsig_asm: str
+    witness: Witness
+    is_coinbase: bool
+    sequence: int
+    inner_redeemscript_asm: str
+    inner_witnessscript_asm: str
+
+class TxStatus(TypedDict):
+    """
+    Transaction confirmation status
+
+    Attributes:
+        confirmed: Whether the transaction is confirmed
+        block_height: Block height (only present if confirmed)
+        block_hash: Block hash (only present if confirmed)
+        block_time: Block timestamp (only present if confirmed)
+    """
+    confirmed: bool
+    block_height: Union[Height, None]
+    block_hash: Union[BlockHash, None]
+    block_time: Union[Timestamp, None]
+
+class Transaction(TypedDict):
+    """
+    Transaction information compatible with mempool.space API format
+
+    Attributes:
+        index: Internal transaction index (brk-specific, not in mempool.space)
+        txid: Transaction ID
+        version: Transaction version (raw i32 from Bitcoin protocol, may contain non-standard values in coinbase txs)
+        locktime: Transaction lock time
+        vin: Transaction inputs
+        vout: Transaction outputs
+        size: Transaction size in bytes
+        weight: Transaction weight
+        sigops: Number of signature operations
+        fee: Transaction fee in satoshis
+        status: Confirmation status (confirmed, block height/hash/time)
+    """
+    index: Union[TxIndex, None]
+    txid: Txid
+    version: TxVersionRaw
+    locktime: RawLockTime
+    vin: List[TxIn]
+    vout: List[TxOut]
+    size: int
+    weight: Weight
+    sigops: SigOps
+    fee: Sats
+    status: TxStatus
+
+class BlockTemplate(TypedDict):
+    """
+    Projected next-block contents from Bitcoin Core's `getblocktemplate`
+    (block 0 of the snapshot). Returned by
+    `GET /api/v1/mining/block-template`.
+
+    Attributes:
+        hash: Pass back as `<hash>` on
+`/api/v1/mining/block-template/diff/{hash}` to fetch deltas.
+        stats: Aggregate stats for this block (size, vsize, fee range, ...).
+        transactions: Full transaction bodies in `getblocktemplate` order.
+    """
+    hash: NextBlockHash
+    stats: MempoolBlock
+    transactions: List[Transaction]
+
+class BlockTemplateDiff(TypedDict):
+    """
+    Delta between the current `getblocktemplate` projection and a prior
+    one identified by `since`. Returned by
+    `GET /api/v1/mining/block-template/diff/{hash}`.
+
+    Attributes:
+        hash: Current next-block hash. Use as `since` on the next diff call.
+        since: Echoed prior hash the diff was computed against.
+        added: Full bodies of transactions that joined the projected next
+block since `since`.
+        removed: Txids that left the projected next block since `since`
+(confirmed, evicted, replaced, or pushed past block 0).
+    """
+    hash: NextBlockHash
+    since: NextBlockHash
+    added: List[Transaction]
+    removed: List[Txid]
+
 class BlockTimestamp(TypedDict):
     """
     Block information returned for timestamp queries
@@ -1022,25 +1163,6 @@ class LegacySeriesWithIndex(TypedDict):
     metric: SeriesName
     index: Index
 
-class MempoolBlock(TypedDict):
-    """
-    Block info in a mempool.space like format for fee estimation.
-
-    Attributes:
-        blockSize: Total serialized block size in bytes (witness + non-witness).
-        blockVSize: Total block virtual size in vbytes
-        nTx: Number of transactions in the projected block
-        totalFees: Total fees in satoshis
-        medianFee: Median fee rate in sat/vB
-        feeRange: Fee rate range: [min, 10%, 25%, 50%, 75%, 90%, max]
-    """
-    blockSize: int
-    blockVSize: float
-    nTx: int
-    totalFees: Sats
-    medianFee: FeeRate
-    feeRange: List[FeeRate]
-
 class MempoolInfo(TypedDict):
     """
     Mempool statistics with incrementally maintained fee histogram.
@@ -1084,6 +1206,12 @@ class MerkleProof(TypedDict):
     merkle: List[str]
     pos: int
 
+class NextBlockHashParam(TypedDict):
+    """
+    `since` hash for `/api/v1/mining/block-template/diff/{hash}`.
+    """
+    hash: NextBlockHash
+
 class OHLCCents(TypedDict):
     """
     OHLC (Open, High, Low, Close) data in cents
@@ -1517,88 +1645,6 @@ class TimestampParam(TypedDict):
     """
     timestamp: Timestamp
 
-class TxOut(TypedDict):
-    """
-    Transaction output
-
-    Attributes:
-        scriptpubkey: Script pubkey (locking script)
-        value: Value of the output in satoshis
-    """
-    scriptpubkey: str
-    value: Sats
-
-class TxIn(TypedDict):
-    """
-    Transaction input
-
-    Attributes:
-        txid: Transaction ID of the output being spent
-        vout: Output index being spent (u16: coinbase is 65535, mempool.space uses u32: 4294967295)
-        prevout: Information about the previous output being spent
-        scriptsig: Signature script (hex, for non-SegWit inputs)
-        scriptsig_asm: Signature script in assembly format
-        witness: Witness data (stack items, present for SegWit inputs; hex-encoded on the wire)
-        is_coinbase: Whether this input is a coinbase (block reward) input
-        sequence: Input sequence number
-        inner_redeemscript_asm: Inner redeemscript in assembly (for P2SH-wrapped SegWit: scriptsig + witness both present)
-        inner_witnessscript_asm: Inner witnessscript in assembly (for P2WSH: last witness item decoded as script)
-    """
-    txid: Txid
-    vout: Vout
-    prevout: Union[TxOut, None]
-    scriptsig: str
-    scriptsig_asm: str
-    witness: Witness
-    is_coinbase: bool
-    sequence: int
-    inner_redeemscript_asm: str
-    inner_witnessscript_asm: str
-
-class TxStatus(TypedDict):
-    """
-    Transaction confirmation status
-
-    Attributes:
-        confirmed: Whether the transaction is confirmed
-        block_height: Block height (only present if confirmed)
-        block_hash: Block hash (only present if confirmed)
-        block_time: Block timestamp (only present if confirmed)
-    """
-    confirmed: bool
-    block_height: Union[Height, None]
-    block_hash: Union[BlockHash, None]
-    block_time: Union[Timestamp, None]
-
-class Transaction(TypedDict):
-    """
-    Transaction information compatible with mempool.space API format
-
-    Attributes:
-        index: Internal transaction index (brk-specific, not in mempool.space)
-        txid: Transaction ID
-        version: Transaction version (raw i32 from Bitcoin protocol, may contain non-standard values in coinbase txs)
-        locktime: Transaction lock time
-        vin: Transaction inputs
-        vout: Transaction outputs
-        size: Transaction size in bytes
-        weight: Transaction weight
-        sigops: Number of signature operations
-        fee: Transaction fee in satoshis
-        status: Confirmation status (confirmed, block height/hash/time)
-    """
-    index: Union[TxIndex, None]
-    txid: Txid
-    version: TxVersionRaw
-    locktime: RawLockTime
-    vin: List[TxIn]
-    vout: List[TxOut]
-    size: int
-    weight: Weight
-    sigops: SigOps
-    fee: Sats
-    status: TxStatus
-
 class TxIndexParam(TypedDict):
     """
     Transaction index path parameter
@@ -8482,7 +8528,7 @@ class BrkClient(BrkClientBase):
     def get_mempool_blocks(self) -> List[MempoolBlock]:
         """Projected mempool blocks.
 
-        Get projected blocks from the mempool for fee estimation.
+        Projected blocks for fee estimation. Block 0 reflects Bitcoin Core's actual next-block selection; blocks 1+ are a fee-tier approximation.
 
         *[Mempool.space docs](https://mempool.space/docs/api/rest#get-mempool-blocks-fees)*
 
@@ -8492,7 +8538,7 @@ class BrkClient(BrkClientBase):
     def get_recommended_fees(self) -> RecommendedFees:
         """Recommended fees.
 
-        Get recommended fee rates for different confirmation targets.
+        Recommended fee rates by confirmation target.
 
         *[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees)*
 
@@ -8502,7 +8548,7 @@ class BrkClient(BrkClientBase):
     def get_precise_fees(self) -> RecommendedFees:
         """Precise recommended fees.
 
-        Get recommended fee rates with up to 3 decimal places.
+        Recommended fee rates with sub-integer precision.
 
         *[Mempool.space docs](https://mempool.space/docs/api/rest#get-recommended-fees-precise)*
 
@@ -8519,10 +8565,10 @@ class BrkClient(BrkClientBase):
         Endpoint: `GET /api/mempool`"""
         return self.get_json('/api/mempool')
 
-    def get_mempool_hash(self) -> int:
+    def get_mempool_hash(self) -> NextBlockHash:
         """Mempool content hash.
 
-        Returns an opaque `u64` that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.
+        Returns an opaque hash that changes whenever the projected next block changes. Same value as the mempool ETag. Useful as a freshness/liveness signal: if it stays constant for tens of seconds on a live network, the mempool sync loop has stalled.
 
         Endpoint: `GET /api/mempool/hash`"""
         return self.get_json('/api/mempool/hash')
@@ -8567,6 +8613,22 @@ class BrkClient(BrkClientBase):
         Endpoint: `GET /api/v1/fullrbf/replacements`"""
         return self.get_json('/api/v1/fullrbf/replacements')
 
+    def get_block_template(self) -> BlockTemplate:
+        """Projected next block template.
+
+        Bitcoin Core's `getblocktemplate` selection: full transaction bodies in GBT order with aggregate stats. The returned `hash` is an opaque content token; pass it as `<hash>` on `/api/v1/mempool/block-template/diff/{hash}` to fetch deltas instead of refetching the whole template.
+
+        Endpoint: `GET /api/v1/mempool/block-template`"""
+        return self.get_json('/api/v1/mempool/block-template')
+
+    def get_block_template_diff(self, hash: NextBlockHash) -> BlockTemplateDiff:
+        """Block template diff since hash.
+
+        Delta of the projected next block since `<hash>`. `added` carries full transaction bodies; `removed` is just txids. Returns `404` when `<hash>` has aged out of server history; clients should fall back to `/api/v1/mempool/block-template`.
+
+        Endpoint: `GET /api/v1/mempool/block-template/diff/{hash}`"""
+        return self.get_json(f'/api/v1/mempool/block-template/diff/{hash}')
+
     def get_live_price(self) -> Dollars:
         """Live BTC/USD price.