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Deep Dive: Orchestrating Multi-Agent Construction Audits with AWS Strands Agents SDK | Agents for Humans

Deep Dive: Orchestrating Multi-Agent Construction Audits with AWS Strands Agents SDK | Agents for Humans

A technical deep dive into orchestrating an asynchronous Tri-Track multi-agent DAG using the AWS Strands Agents SDK, featuring single-writer state reducers and durable human-in-the-loop checkpoints.

Jaguri

Multi-Agent Orchestration with AWS Strands Agents SDK

In building IRONCLAD Sentinel for the AWS Agents for Humans Hackathon, our core architectural challenge was coordinating multiple specialized agents without creating an unmanaged, recursive loop.
Rather than relying on a monolithic agent or a generic ReAct loop, we leveraged the AWS Strands Agents SDK (GraphBuilder) to implement an asynchronous Directed Acyclic Graph (DAG) with an explicit fan-out/fan-in barrier.

The Tri-Track Architecture

  1. ForensicAuditSentinel (Professional Track): Executes form-aware OCR line-item extraction from AIA G702/G703 payment applications and evaluates notarized lien waiver chronology against county disbursement records.
  2. FairPayStatutoryGuardian (Good Neighbor Track): Evaluates subcontract payment riders, classifies conditional clauses (pay-if-paid vs. pay-when-paid), and determines statutory prompt-pay countdowns across a 14-jurisdiction reference catalog.
  3. EverydayDecisionCardEmitter (Everyday Track): Sits downstream of the fan-in barrier, synthesizing verified upstream findings into a single executive deliverable.

Single-Writer State Reducer Invariants

To prevent cross-agent race conditions during concurrent execution, we implemented a custom state reducer layer where each channel in IroncladState is enforced with strict caller_node authorization:
  • extracted_line_items and retainage_audit_result are single-writer channels owned exclusively by ForensicAuditSentinel.
  • statutory_prompt_pay_clock is single-writer owned by FairPayStatutoryGuardian.
  • flagged_discrepancies and error_logs are append-only channels accessible to all authorized nodes.

Human-in-the-Loop Resumption

At the conclusion of the audit, Strands pauses execution at a durable checkpoint. The system never executes autonomous financial payouts. Instead, it emits a structured DecisionCardPayload and awaits an authenticated 1-click human action (APPROVE_RELEASE, HOLD_REQUEST_CORRECTION, or ESCALATE_LEGAL). If any discrepancy or invalid waiver status is detected, the approve gate is programmatically locked down by code-level guardrails.
AWS Strands Agents SDK provided the exact mathematical determinism and multi-agent isolation required for high-stakes enterprise fintech.
# strands# strands-agents# agents# architecture# python
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