HarnessTax: How Much Does the Harness Matter for Coding Agents?

(harnesstax.github.io)

41 points | by matt_d 3 hours ago

7 comments

  • corv 2 minutes ago
    My own findings are in line with this research:

    Having a coding harness is critical but the differences between them are overstated.

    Personally, I’ve replaced OpenCode with a thin wrapper around Pydantic-AI as the pythonic analogue to Pi-Agent for headless use via Hermes

    They’d all do the job - I just prefer to compartmentalize for access control.

    Keeping the harness’ surface area tiny had the added benefit of preserving my understanding and being able to adapt it to my preferred workflow effortlessly

  • Supermancho 1 hour ago
    The term "harness" here is being overloaded for the term "agent", which is worrying. Putting that aside, there are many factors that matter. The "harness" context, the execution pattern (parallel vs sequential), the ability to delegate to other models, etc.

    Optimal harnesses use concurrent execution + subagents and are not stuck on one model. Cost and performance are impacted GREATLY by these tactics, regardless of the native agent context (instruction). This kind of single-harness analysis is shallow and misleading, although the finding that "Provider-specific optimization does not guarantee the best pairing" is probably correct, depending on how you measure.

    It is a starting point.

  • mikert89 16 minutes ago
    As the model gets smarter, you need to tell it less
    • NewJazz 12 minutes ago
      As the black box gets bigger, you need to stop expressing yourself even more.
  • ed_mercer 1 hour ago
    Does this extend to open models like GLM 5.3? This would mean that simply changing the harness to Pi reduces cost in half?
    • roywiggins 2 minutes ago
      I've found the experience of using Pi with local models feels a lot snappier than both OpenCode or Claude Code.
  • jswelker 1 hour ago
    Much of the extra weight of Claude Code and Codex harness are (ostensibly?) for security and alignment purposes. Whether they are effective is an open question, but leaving those dimensions out and calling it a tax is disingenuous, just turning insecurity into a negative externality.

    "Why pay the waste disposal tax? Dumping into the ocean is free!"

    Pi actively omits any sort of guardrails and sandboxing in the name of speed and simplicity, so it is not shocking that it is faster and simpler.

    Doubling the cost of something in the name of vague security is standard operating procedure for big enterprises, maybe even quite cheap.

    • roywiggins 2 minutes ago
      It's not hard to sandbox Pi without adding anything substantial to the actual size of the system prompt, which is what HarnessTax is mostly measuring.
    • shshsjsj 31 minutes ago
      [dead]
  • appbeforelunch 15 minutes ago
    [dead]
  • robinpie 42 minutes ago
    claude code feels mildly shitty to use in the way that every other vibe-coded-project-got-out-of-hand project does, which is like, not that bad, but it's fucking ridiculous for a 2 trillion dollar company's main companion product