HF127 / v1.8.3 is a mandatory, non-consensus reliability release built on the HF123 Fast Chain Engine, HF124 mining-liveness engine, HF125 acknowledged block delivery, and HF126 equal-height fork recovery.

• No new activation height.
• Protocol Epoch 2 remains active from mainnet block #24000.
• Post-activation block version remains 2.
• P2P protocol number remains 2.
• Fast Chain Engine remains QUB-FCE-1.
• Block, transaction, address, reward, DAA, checkpoint, pool, QUB and JIN consensus rules are unchanged.

Ordinary wallet and protocol transactions now use explicit application-level delivery messages:

SubmitTx
TxAck

A transaction is considered delivered when QUB Core receives:

one positive official-seed ACK
or two positive ACKs from distinct direct peers
or one explicit positive ACK in an isolated deployment with no official destination

Successful socket writes are no longer presented as proof of peer acceptance. A positive ACK is returned only after the receiver has confirmed the transaction in canonical state or durably committed it to QUB-FCE-1. Raw transactions and delivery metadata remain durable in wallet-pending-txs.json until canonical confirmation depth is reached.

Seeds expose a bounded tx-submit reserve lane so transactions can still be accepted when normal inbound peer slots are full. Delivery retries run in an independent single-flight worker and do not depend on sender mining, GUI polling, Explorer availability, or manual relay.

Before signing, GUI and CLI transaction flows require validated current-chain evidence. Coin selection and signing do not proceed from a stale, incompatible or unacknowledged local branch.

Operator commands:

qubd --config <config> tx-delivery-status [txid]
qubd --config <config> relay-pending-txs

HF127 reduces the time advantage of a miner that has just found a block:

• latency-sensitive P2P sockets use TCP_NODELAY;
• official/configured bootnodes are attempted before historical peerbook entries;
• outbound dialing is detached, bounded and protected by per-peer exponential backoff;
• ephemeral block-submit and tx-submit source ports are not persisted into the peerbook;
• seeds begin outward diffusion after durable acceptance and before returning the producer ACK;
• live block/transaction relay reuses the registered in-memory canonical state when available;
• block/transaction delivery can complete without making official seeds a permanent liveness dependency.

QUB Core exposes the complete 1–100% CPU and 0–100% GPU ranges. CPU and GPU percentages are available through both sliders and exact numeric inputs.

At 85% or above, or when a manual worker/work-item override is used, QUB Core displays a red hardware-risk warning and requires a session-only mandatory confirmation before solo or pool mining can start.

At 100% CPU power, QUB Core uses all logical processors with continuous duty. Explicit CPU worker and GPU work-item overrides remain available for advanced operators and are not constrained by a QUB-specific software ceiling; operating-system and device-driver limits still apply. If any requested CPU worker cannot be created, the round fails closed instead of silently running a partial nonce-lane plan. If no CPU/GPU worker starts, the GUI does not claim that mining is active.

The reference RPC miner no longer imposes the previous 128-worker QUB limit and assigns disjoint nonce lanes to workers.

HF127 retains:

• HF123 append-only Fast Chain Engine and single canonical in-memory owner;
• HF124 consensus-valid pool-share templates, stable mining rounds, batched persistence and fair relay;
• HF125 explicit SubmitBlock / BlockAck, durable pending block retry and reserve submission lane;
• HF126 mineable equal-height PoW ties, verified re-anchor path and sibling-branch overlap delivery;
• Explorer API mempool optimization and the v0.7.1 same-origin Explorer stack.

• RELEASE_NOTES-v1.8.3-HF127.md
• HF127-v183-RELIABILITY-REVIEW.md
• HF127-v183-DEPLOY-RUNBOOK.md
• README-FAST-CHAIN-ENGINE.md
• README-RPC-MINER.md

Runtime image/audio/font assets are intentionally omitted from source-only packages. Copy known-good assets into assets/ before building the Windows GUI distribution.