harness engineering > prompt engineering

Harrison Chase, co-founder of LangChain, has shared perspectives on X (formerly Twitter) distinguishing "harness engineering" from traditional prompt engineering, suggesting a conceptual evolution in how developers interact with and structure AI systems. The post likely argues that modern AI development involves building scaffolding, workflows, and orchestration layers around models rather than simply crafting individual prompts. This framing positions harness engineering as a more comprehensive discipline focused on system-level design, tool integration, and agent coordination.

Harnesses Aka app servers but for AI The meta programming language went from typed interfaces to declarative injection to natural language (…
I think you should build your own harness too. Build on primitives. Models come and go.
That's actually exactly what I was saying. Value, it's in the harness.
Another banger article from the @LangChain team! Harness evolution combined with specialist local models will be the way forward undoubtedly…
@hwchase17 Exactly. he harness is where the 'soul' of the agent lives. Excited to see how Deep Agents and LangChain can keep pushing this la…
Just read @hwchase17’s excellent thread on why agent harnesses are becoming the dominant way to build agents and why they’re intimately tied…

Source: Harrison Chase (X) | 2026-04-12

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