fix: local block hash consistency in mooncake bench (#6310)

Signed-off-by: PeaBrane <yanrpei@gmail.com>

lib/kv-router/Cargo.toml

@@ -50,6 +50,7 @@ rstest_reuse = "0.7.0"
 serde_json = { workspace = true }
 tokio = { workspace = true, features = ["rt", "macros", "time"] }
 dynamo-mocker = { workspace = true }
+dynamo-tokens = { workspace = true }
 minstant = "0.1.7"
 futures = "0.3"
 

lib/kv-router/benches/mooncake_bench.rs

@@ -7,7 +7,9 @@ use dynamo_kv_router::indexer::{
     KvIndexer, KvIndexerInterface, KvIndexerMetrics, KvIndexerSharded,
 };
 use dynamo_kv_router::protocols::RouterEvent;
+use dynamo_kv_router::protocols::XXH3_SEED;
 use dynamo_kv_router::{ConcurrentRadixTree, PositionalIndexer, ThreadPoolIndexer};
+use dynamo_tokens::compute_hash_v2;
 use rand::prelude::*;
 use std::fs::File;
 use std::io::{BufRead, BufReader};
@@ -254,6 +256,15 @@ fn tokens_from_request(request: &MooncakeRequest, block_size: u32) -> Vec<u32> {
         .collect()
 }
 
+/// Compute the LocalBlockHash for a block-level hash_id the same way the mock
+/// engine does: expand to `block_size` repeated u32 tokens, then XXH3 hash.
+fn local_block_hash_from_id(hash_id: u64, block_size: u32) -> LocalBlockHash {
+    let tokens: Vec<u32> = (0..block_size).map(|_| hash_id as u32).collect();
+    let bytes: &[u8] =
+        unsafe { std::slice::from_raw_parts(tokens.as_ptr() as *const u8, tokens.len() * 4) };
+    LocalBlockHash(compute_hash_v2(bytes, XXH3_SEED))
+}
+
 /// Create a styled progress bar, optionally with a known total length.
 fn make_progress_bar(total: Option<u64>) -> ProgressBar {
     let progress = match total {
@@ -418,7 +429,7 @@ fn prepare_worker_traces(
                         request
                             .hash_ids
                             .iter()
-                            .map(|id| LocalBlockHash(*id))
+                            .map(|id| local_block_hash_from_id(*id, args.block_size))
                             .collect(),
                     ),
                 })

lib/llm/src/block_manager/kv_consolidator/tracker.rs

@@ -17,15 +17,14 @@
 
 use std::collections::{HashMap, HashSet};
 
+use dynamo_kv_router::protocols::XXH3_SEED;
+
 /// LocalBlockHash type (content hash from tokens only)
 type LocalBlockHash = u64;
 
 /// SequenceHash type (position-aware hash, includes parent context)
 type SequenceHash = u64;
 
-/// Seed for xxHash3 computation (must match the indexer's seed)
-const XXH3_SEED: u64 = 1337;
-
 /// Compute a LocalBlockHash from token IDs (content only)
 fn compute_local_block_hash(token_ids: &[u32]) -> LocalBlockHash {
     let bytes: Vec<u8> = token_ids