Bitcoin's transition from defense to proactive evolution: An in-depth look at protocol layer mempool(mempool) in 2025

From the Bitcoin Optech 2025 Annual Report, Bitcoin is undergoing a quiet yet profound technological revolution. This revolution’s core is not in price fluctuations but in systematic upgrades to underlying protocols and infrastructure—shifting from addressing immediate risks to proactively preparing for challenges ten years down the line.

Behind this transformation are three main driving features: the community’s systematic response to existential threats like quantum computing, achieving architectural goals of “bottom-layer stability and top-layer flexibility” through layered design, and investing substantial engineering resources to lower participation barriers. It is at the intersection of these forces that ten structural technological breakthroughs have emerged over the past year. Among them, the underlying optimization of the transaction mempool(mempool) is particularly critical—it directly impacts the fate of every transaction in the network.

The Three Major Technological Evolution Features: Keys to Understanding Bitcoin’s Future

Preemptive Defense: From Passive Patching to Active Reinforcement

In the past, the Bitcoin community mainly responded passively to known security vulnerabilities. Now, this approach has shifted. The roadmap for defending against quantum threats has become clear and technically feasible for the first time, extending security planning from “the present” into the “post-quantum era.” This is not only a breakthrough in theoretical research but also a concrete upgrade path translating abstract cryptographic threats into actionable steps.

Layered Functionality: Maintaining Stability While Exploring Boundaries

High-density discussions on soft fork proposals and the Lightning Network’s real-time fund adjustment capabilities reflect Bitcoin’s pursuit of a delicate balance. The underlying protocol maintains core stability, while upper-layer applications and second-layer protocols gain more flexibility. This layered philosophy is evolving from an abstract architectural concept into specific code implementations.

Decentralized Infrastructure: Combating Real-World Centralization Pressures

Whether optimizing mining protocols or significantly reducing full node operation costs, the Bitcoin community is undertaking a systematic “lowering of barriers” project. The goal is clear: enable more ordinary devices to independently verify transactions, thereby strengthening the network’s resistance to censorship.

Top Ten Technological Breakthroughs: Power to Reshape the Bitcoin Ecosystem

1. Quantum-Resistant Roadmap: From Theory to Engineering

【Progress Status: Research and Long-term Deployment】

2025 marks a qualitative shift in the Bitcoin community’s attitude toward quantum computing risks. BIP360 has been assigned a number and renamed P2TSH (Pay to Tapscript Hash), serving as a key stepping stone in the quantum defense roadmap and supporting certain Taproot use cases.

More importantly, the community has engaged in in-depth discussions on quantum-safe signature schemes, including constructing Winternitz signatures by re-enabling opcodes like OP_CAT, exploring STARK verification as a native scripting capability, and optimizing on-chain costs for hash-based signature schemes (e.g., SLH-DSA/SPHINCS+).

Why is this work so critical? Because it touches the mathematical foundation of Bitcoin. If elliptic curve discrete logarithm assumptions are weakened by quantum computing, systemic migration pressures will arise. This means long-term holders need to monitor future asset migration windows and choose custodial solutions with clear upgrade paths.

2. Surge of Soft Fork Proposals: Building Programmable Self-Protection Mechanisms

【Progress Status: High-Density Discussion Stage】

2025 has been a year of concentrated soft fork proposal bursts. Multiple contract-like proposals such as CTV (BIP119), CSFS (BIP348), LNHANCE, and OP_TEMPLATEHASH have advanced simultaneously, with the core goal of enhancing script expressiveness while maintaining minimalism. Notably, the emergence of OP_CHECKCONTRACTVERIFY (becoming BIP443) marks a significant step in Bitcoin’s exploration of programmability.

These upgrades may seem esoteric but are essentially adding new “physical laws” to the global value network. They will make native constructs like “Vaults” simpler, safer, and standardized, allowing users to set delayed withdrawals and revocation mechanisms—effectively embedding security vault logic into the protocol layer.

At the same time, these capabilities are expected to greatly reduce interaction complexity for second-layer protocols like Lightning and DLCs (Discrete Log Contracts), further accelerating Bitcoin’s usability as a global settlement layer.

3. Mining Decentralization: Distributing Power to Miners

【Progress Status: Experimental Implementations and Protocol Evolution】

Bitcoin’s resistance to censorship directly depends on the degree of mining decentralization. In 2025, Bitcoin Core 30.0 introduced an experimental IPC interface, significantly optimizing the interaction efficiency between mining pools and node verification, reducing reliance on inefficient JSON-RPC—paving the way for Stratum v2 integration.

The key innovation of Stratum v2 is its ability to further decentralize transaction selection from mining pools to more dispersed miners. What does this mean? It means ordinary miners are no longer forced to pack transactions chosen by pools but have more autonomy—directly enhancing the network’s resistance to censorship.

Meanwhile, mechanisms like MEVpool aim to address MEV issues through blind templates and market competition. Ideally, multiple marketplaces coexist to prevent the market itself from becoming a new centralization hub. This is crucial for ensuring that, even in extreme environments, ordinary users’ transactions can still be fairly included.

4. Immunity System Upgrade: Self-Check Before Real Attacks

【Progress Status: Ongoing Engineering Operations】

Security hinges on “preemptive measures.” In 2025, numerous vulnerabilities in Bitcoin Core and Lightning implementations (LDK/LND/Eclair) were discovered and fixed, covering issues like funds being stuck, privacy leaks, and potential theft risks.

Particularly noteworthy is Bitcoinfuzz, which uses “differential fuzz testing” to compare responses of different software to the same data, discovering over 35 deep bugs within a year. This intense stress testing signifies ecosystem maturity—like a vaccine, short-term exposing issues but long-term greatly enhancing system immunity.

For users relying on privacy tools or the Lightning Network, this serves as a warning: no software is perfect. Keeping key components updated is fundamental to fund security.

5. Lightning Network Splicing: Real-Time Channel Fund Adjustment

【Progress Status: Cross-Implementation Experimental Support】

In 2025, Lightning Network achieved a major usability breakthrough: Splicing (channel hot updates). This technology allows users to dynamically adjust channel funds without closing the channel—recharges or withdrawals can be done without breaking the existing connection, with experimental support now available in LDK, Eclair, and Core Lightning.

The significance of Splicing lies in eliminating a long-standing operational friction for Lightning users. Traditionally, adjusting channel funds required closing and reopening channels—this process was complex. Splicing aims to significantly lower the learning curve for channel engineering, making Lightning more like a “balance account” payment layer. This is a key piece for Bitcoin payments to reach large-scale daily use.

6. Cost of Verification Revolution: Making Full Nodes Accessible to Ordinary People

【Progress Status: Prototype (SwiftSync) / BIP Draft (Utreexo)】

The decentralization moat depends on low verification barriers. Technologies like SwiftSync and Utreexo are directly challenging this threshold.

SwiftSync optimizes UTXO set writing during initial block download (IBD), only adding outputs to chainstate if they remain unspent at IBD end, and uses “minimal trust” hints files. In prototype implementations, it accelerates IBD by over 5 times—also opening space for parallel verification.

Utreexo (BIP181-183) takes a completely different approach: using Merkle forest accumulators, allowing nodes to verify transactions without storing the full UTXO set locally. What does this mean? It means older devices or resource-constrained servers can finally run full nodes.

The ultimate goal of these technologies is to increase the number of independent verifiers in the network, strengthening Bitcoin’s resistance to censorship.

7. Cluster Mempool Reconstruction: Systematic Upgrade of the Transaction Pool Layer

【Progress Status: Near Release Stage】

In Bitcoin Core 31.0, the Cluster Mempool implementation is nearing completion. This is a fundamental overhaul of the transaction mempool(mempool), introducing data structures like TxGraph to abstract complex transaction dependencies into efficiently solvable “transaction cluster linearization” problems.

This may sound like a technical detail, but it has far-reaching implications. Cluster Mempool is expected to improve fee estimation stability and predictability by eliminating anomalous ordering caused by algorithmic limitations, leading to more rational and smooth network performance during congestion. User fee bumping requests (CPFP/RBF) will also work under more predictable logic, directly improving fee market predictability.

In short, Cluster Mempool is an intelligent upgrade to the transaction buffer—making transaction fate more controllable and transparent.

8. Fine-Grained Governance of P2P Propagation Layer: Balancing Reachability and Economics

【Progress Status: Strategy Updates and Continuous Optimization】

Over the past year, Bitcoin’s P2P network has undergone an important strategic adjustment. Facing a surge in low-fee transactions, Bitcoin Core 29.1 lowered the default minimum relay fee to 0.1 sat/vB. Meanwhile, the Erlay protocol continues to advance to reduce node bandwidth consumption; proposals like “block template sharing” are also being developed, along with ongoing optimization of compact block reconstruction strategies.

What is the background of these strategy changes? It’s a rethinking of fairness. With more consistent policies and lower default node thresholds, the feasibility of propagating low-fee transactions has greatly increased. This not only reduces the bandwidth requirements for running nodes but also maintains true network democracy—ensuring resource-constrained users’ transactions are treated more fairly.

9. OP_RETURN and the Philosophy of Block Space

【Progress Status: Mempool Policy Changes (Core 30.0)】

Bitcoin Core 30.0 relaxed OP_RETURN policy restrictions, allowing more outputs and removing some size limits—this seemingly technical change sparked intense philosophical debates about Bitcoin’s use cases in 2025.

It’s important to note that this pertains to Bitcoin Core’s Mempool Policy (default relay standards), not consensus rules. However, mempool policies significantly influence how easily transactions propagate and are seen by miners, thus affecting the competitive landscape for block space.

Supporters argue this corrects incentive distortions, while opponents worry it endorses “on-chain data storage.” This debate reminds us: as block space is a scarce resource, its usage rules—even at the non-consensus level—are the result of continuous interests and power struggles—there is no absolute technical neutrality.

10. Bitcoin Kernel: Modular Decoupling of Core Code Components

【Progress Status: Architectural Reengineering and API Release】

In 2025, Bitcoin Core took a key step toward architectural decoupling: introducing the Bitcoin Kernel C API. This marks the separation of “consensus verification logic” from the large node software into an independent, reusable standard component. The kernel now supports external projects to reuse block validation and chain state logic.

What does this mean? It means the Bitcoin ecosystem finally has a standardized “factory engine.” Wallet backends, indexers, analysis tools can directly invoke official verification logic, avoiding risks of divergence caused by re-implementing consensus. This is a structural enhancement for ecosystem security—applications built on Bitcoin Kernel will be significantly more robust.

Conclusion: From Passive to Proactive, Bitcoin Enters a Deep Development Stage

The protocol evolution in 2025 reflects not showy technology but a more mature and responsible attitude. From forward-looking quantum defenses, to systematic infrastructure optimization like mempool, to enabling ordinary users to independently verify transactions—each step points in the same direction: building a more robust, censorship-resistant, and inclusive monetary network.

These technological breakthroughs may not immediately impact prices, but they are shaping Bitcoin’s core competitiveness over the next five to ten years. For developers, this is an era of technological dividends; for long-term holders, a crucial lesson in asset security; for ordinary users, better, safer payment experiences are on the horizon.