HadAgent: Harness-Aware Decentralized Agentic AI Serving with Proof-of-Inference Blockchain Consensus
Authors: Landy Jimenez, Mariah Weatherspoon, Bingyu Shen, Yi Sheng, Jianming Liu, Boyang Li
Organizations: Department of Computer Science and Technology, Kean University, Union, New Jersey, U.S. · Department of Computer Science and Engineering, University of Notre Dame, Notre Dame, Indiana, U.S. · Bellini College of Artificial Intelligence, Cybersecurity and Computing, University of South Florida, Tampa, Florida, U.S. · DefinanceX, U.S.
Proof-of-Work (PoW) blockchain consensus consumes vast computational resources without producing useful output, while the rapid growth of large language model (LLM) agents has created unprecedented demand for GPU computation. We present HadAgent, a decentralized agentic AI serving system that replaces hash-based mining with Proof-of-Inference (PoI), a consensus mechanism in which nodes earn block-creation rights by executing deterministic LLM inference tasks. Because verification requires only re-executing a single forward pass under identical conditions, cross-node verification operates at consensus speed. HadAgent organizes validated records into a three-lane block body with dedicated DATA, MODEL, and PROOF channels, each protected by an independent Merkle root for fine-grained tamper detection. A two-tier node architecture classifies secondary nodes as trusted or non-trusted based on historical behavior: trusted nodes serve inference results in real time through optimistic execution, while non-trusted nodes must undergo full consensus verification. A harness layer monitors node behavior through heartbeat probes, anomaly detection via deterministic recomputation, and automated trust management, creating a self-correcting feedback loop that isolates malicious or unreliable participants. Experiments on a prototype implementation demonstrate 100% detection rate and 0% false positive rate for tampered records, sub-millisecond validation latency for record and hub operations, and effective harness convergence that excludes adversarial nodes within two rounds while promoting honest nodes to trusted status within five rounds.
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Fig. 1: Overview of the HadAgent system architecture. From top to bottom: the Agent Interaction Layer handles inference requests between agents; the Two-Tier Nodes Layer organizes master and secondary nodes with cross-node verification; the Network and Harness Layer provides communication, monitoring, and fault tolerance; and the Block layer stores validated records across three Merkle-rooted lanes (DATA, MODEL, PROOF).
Fig. 2: Overview of Block Design. Each block contains a header and a three-lane body. The header stores the block height, previous block hash, timestamp, and three independent Merkle roots corresponding to the DATA, MODEL, and PROOF lanes. The Data Lane records dataset and audit hashes, the Model Lane records model hashes and version identifiers, and the Proof Lane records input/output hashes and validation scores; all lanes include digital signatures for authentication. Only cryptographic hashes, metadata, validation scores, and signatures are stored on-chain; raw datasets, model weights, and full inference outputs remain off-chain and are referenced by their content hashes.
Fig. 3: Consensus Flow with Interval Verification. The cycle proceeds in eight steps: (1) an agent submits an inference request; (2) a secondary node executes the LLM inference task; (3) the master node evaluates the returned result and computes a validation score; (4) the validated record is queued in the mempool; (5) a cross-master verification interval is triggered, in which master nodes independently re-evaluate a randomly selected subset of tasks drawn from standardized benchmarks (e.g., MMLU, HellaSwag); (6) multiple master nodes aggregate their verification outcomes through multi-master voting; (7) the agreed-upon records are committed to the chain as a finalized block; and (8) the validated response is returned to the requesting agent.
Fig. 4: Demonstration of the Two-Tier Node Architecture and Inference Paths. Left (Optimistic Execution): When a trusted secondary node handles a request, the master node routes the task, the trusted node runs inference and returns the result directly to the agent without waiting for consensus, enabling real-time serving. The master node evaluates the result and enters it into the mempool in the background. Right (Verified Execution): When a new (non-trusted) secondary node handles a request, its result is not delivered immediately. Instead, the submitted result must pass master evaluation, enter the mempool, and undergo full consensus verification with a retroactive check before the response is delivered to the agent.
Beijing Advanced Innovation Center for Future Blockchain and Privacy Computing, Beihang University, Beijing, China · School of Artificial Intelligence, Beihang University, Beijing, China · Zhongguancun Laboratory, Beihang University, Beijing, China +1