Harness-of-Harness scores 71.52 vs 58.24 for naive continuation on GameCraft-Bench
Long-horizon agent state and skill-file research
Google SKILL.state cuts agent token use 94%, raises accuracy
Long-horizon agents can run substantially longer tasks at a fraction of the token cost if task state can be fully captured in a schema. The result challenges the assumption that growing conversation history is necessary for agent accuracy.
The full picture
SKILL.state, from researchers at Google and Purdue, replaces the ever-growing conversation transcript in long-horizon agents with a small structured execution state. The model receives only skill instructions, a structured state, and the latest observation; reasoning traces are discarded after each step, keeping prompt size roughly constant as task length grows. On a 100-step warehouse task with Gemini 3 Flash, SKILL.state scored 0.94 using 65,408 tokens against a LangGraph-style baseline scoring 0.91 with 1,062,387 tokens, a 16.2x difference and approximately 94% fewer tokens. The method is bounded by schema completeness: it works only when all information needed in downstream steps can be captured in the state schema.
How it developed
Amazon-Microsoft SPACE paper: grouping agent actions cuts LLM rounds from 10.2 to 5.2 while raising ScienceWorld success rate from 35.9% to 67.2%
Google and Purdue's SKILL.state, published September 3, replaced growing agent transcripts with a structured state, cutting tokens 94% on a 100-step task while holding accuracy at 0.94 versus a baseline's 0.91. ByteDance's Chain-of-Experience, published September 4, offered a direct contrast: keeping full attempt history in context raised accuracy from 66.8% to 79.3% across six benchmarks. Amazon and Microsoft's SPACE added a third angle, training agents to batch safe sequential actions, raising ScienceWorld success from 35.9% to 67.2% while cutting LLM rounds from 10.2 to 5.2.
ContextPilot paper described, using RL-trained context management
JIT-Agent paper: task-specific harnesses let smaller models outscore larger ones with 36% lower cost
Three benchmarks published September 2 document frontier model struggles on extended tasks: 17 models averaged a 6.4% pass rate on multi-step terminal tasks, 10 of 17 solving zero; the best agent scored 51.3/100 after 12 hours; and the top setup on year-long decisions reached 27.3% of human earnings. Investor Chamath Palihapitiya, at Stanford's AI Club, warned AI investment could reach a trough of disillusionment if these limitations are not addressed. A separate paper found agent traces compress into finite-state machines with 7 to 43 states.
Not Diamond publishes dynamic model routing methodology claiming Pareto-dominance over Opus xhigh at 20-80% lower cost
A head-to-head experiment published September 1 comparing OpenClaw 2.0 and Hermes agents on a video generation task found that self-verification depth, not model capability, drove token consumption: OpenClaw used approximately 2.1M tokens with 10 self-fixes, Hermes approximately 2.9M with 20, the extra roughly 800K tokens spent on Hermes's render-checking harness measuring frame timing, seam visibility, and spec compliance. The experiment frames a portion of agent token use as QA allocation, raising the question of how much compute agents should spend proving their work before returning results.
ByteDance Chain-of-Experience paper shows keeping full attempt history outperforms compression for test-time improvement
Multiple papers on how agents should manage state in long tasks, reported August 30-31, reached two conclusions: structured state cuts token use and raises accuracy, while skill file injection consistently lowers performance. Google and Purdue's SKILL.state reduced tokens 94% on a 100-step warehouse task; Meta's EvoHarness-RL raised ALFWorld accuracy from 47.9% to 96.9%; Nvidia's ACES found skill document scores correlate near-zero with runtime gains; and WebDev-Skills-Bench found skill injection lowered pass rates across all tested models.
Coverage confirms 94% token reduction and accuracy improvement from 0.91 to 0.94
SKILL.state paper published; 16.2x token reduction and accuracy gain reported on 100-step warehouse task with Gemini 3 Flash
Paper testing eight leading models on year-long decision tasks finds best setup achieves 27.3% of human earnings
WebDev-Skills-Bench finds skill file injection lowers pass rates and raises token costs across all four tested models
Nvidia ACES finds skill document scores correlate near-zero with measured runtime improvement
Paper argues on-policy distillation outperforms GRPO for long-horizon agent training
Sources
- Harness-of-Harness beat repeated coding-agent runs by carrying code, QA evidence, and plans forward.
- A token is no longer a comparable unit of work.
- New Amazon Microsoft paper shows long-horizon agents should not need an LLM decision after every tiny action; the hard p…
- Long-running agents do not just need a bigger context window. They need to learn what deserves to stay in context at all…
- A smaller model with the right task-specific harness can beat a stronger model.
- Different LLMs may behave more similarly inside an agent harness than their raw traces suggest.
- Not Diamond just released the methodology behind their model routing which gets Opus xhigh quality while cutting agent c…
- Model switching mid-run has a handoff tax: stronger models often do better with less of a weaker model’s history, while …
- OpenClaw 2.0 vs Hermes experiment by @atomicbot_ai is a good example of why the model alone tells you very little about …
- New ByteDance paper shows for test-time improvement, keeping the messy history of attempts can work better than turning …
- Most agent self-improvement happens too late: the system learns from a run only after that run is already over.
- Small models fail the same way big models do, so this paper shows you can collect a cheap model's mistakes once and use …
- Long-horizon agent reliability has not arrived yet with better models.
- Another long-horizon benchmark, another reminder that current AI can work for hours and still remain far from mastering …
- Beautiful paper from Google.
- New Google paper makes a strong case for replacing ever-growing agent histories with a small, explicit execution state.
- Another paper that so clearly exposes AI’s long-horizon problem.
- This paper is a brutal reality check for long-horizon AI. Give an agent a year of interconnected decisions, delayed feed…
- Automatically patching an agent's harness is easy; keeping the patches that help is the hard part.
- Does giving research agents full autonomy add capability
- What if context management were a program the model writes rather than a rule your harness applies?
- Attaching a skill file to every prompt in a coding session is usually a net loss.
- A context window is a terrible place to store the state of an 80-minute agent run.
- The harness around a model decided more of the benchmark score than the model itself. So treat scaffold selection as a f…
- New Nvidia paper.
- Giving an agent a memory hierarchy is not what makes it reason better over long tasks. What helps is scoring each memory…
- No amount of post-training cleanly fixes weak long-horizon foundations: noisy trajectories compound errors, sparse rewar…
- Telling a research AI agent which method to use is close to telling it nothing at all.
- New Meta paper says giving an agent more memory and tools is not enough if the agent never learns when they are worth us…
- A strong LLM does not automatically make a reliable data agent: DataSpace shows that the harness, cross-source joins, an…
- What does it take for an AI to stay useful when a task lasts for hours, or weeks, and the world keeps changing?
- Agents can accumulate hundreds of skills without becoming proportionally better, which makes skill consolidation and reu…
Related
Want this in your inbox?
I send a short email each morning with the stories that moved. If you would rather just read here, that works too.
Subscribe free