AI harnesses: The secret sauce for deterministic AI workflows

Jul 8, 2026 · Lenny's Podcast
🎧 PodShort 15 min squeezed to 2 AI SprinklerAS AI / ML New
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Key Insights
  • A harness is simply code wrapped around an AI agent to make it more effective for a specific use case, allowing for more prescriptive control over how a job gets done.
  • Building a custom harness makes sense when you have a specific workflow that needs consistent setup and outcomes, especially for tasks that are slightly more complex or require a deterministic approach.
  • The speaker built their first harness to debug Sentry issues, using internal tools and ensuring all follow-up actions (like tracking in Linear and writing documentation) were automated.
  • A harness allows you to be more efficient, consistent, and achieve better outcomes by micro-managing the AI agent's actions and tools for a specific job, rather than using a general-purpose coding tool.
  • When building a harness, it's crucial to be very specific about the workflow, the tools the agent is allowed to use, and where custom prompts make sense, especially when using agent SDKs.
  • The speaker found that both Claude Code and Codex initially resisted building a harness with AI components, instead wanting to create something purely deterministic, highlighting the need for very specific prompting.
  • Harnesses can create their own artifacts in a file store, saving evidence from runs for the agent to use in the future, which is a key feature for continuous improvement and learning.
  • The process of building a harness has shifted the speaker's perspective, realizing that constraining the work of AI agents through specific harnesses can lead to real leverage and custom outcomes, especially when combined with general-purpose agents for orchestration.

RevBots.ai View:

  • AI Sprinkler teams bolt on harnesses without full workflow transformation.
  • Harnesses create operational efficiency but don't solve SaaS Hoarder tool sprawl.
  • ARM stage requires orchestration layer beyond task-specific harnesses.
  • Custom harnesses outperform general AI tools for complex deterministic workflows.
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