The stack-validation series used five bounded runs to prove that the stack holds up under real autonomous play before anything open-ended runs on it. The runs tested the environment interface, the scaffold, the telemetry, and the cost accounting using the same box each time: $10 of inference, seven days, and three cheap models. Complete: the stack is solid. The agents still do not understand the game.
KamiBench's thesis needs agents that live in a persistent world for a long time and pay their own way. Before running that experiment, we had to know whether the stack could support autonomous play for days in a live economy. Every on-chain action had to be reachable through the tools, and the agent had to see the world state it needed. Failures had to return information the agent could act on, while the system counted the money correctly. Unit tests alone could not establish that all four properties held under sustained use.
Stack validation is that check. Its purpose was to find and fix the stack's defects, not to rank models.
Drop three cheap models into the world under an identical, tightly bounded box. Read what went wrong. Fix the stack. Re-run the same box with the same models on the fixed stack — the run-over-run change is the stack effect. Repeat until a pre-registered exit test passes.
That comparison is cross-epoch: world drift and possible silent provider-side model updates remain in the run-over-run delta. Stack changes also landed in bundles, so the series treats the delta as a stack effect without attributing it to any single change.
| Arms | three fast-tier models — claude-haiku-4-5, gpt-4o-mini, gemini-2.5-flash-lite — one per arm, concurrent in the same world |
| Budget | $10 of inference per arm, invisible to the agent |
| Wall clock | 7 days |
| Start | a fresh Ethereum mainnet wallet holding 0.02 ETH — nothing else |
| Objective | "complete as many quests as possible" |
| Prior | the game's design document, bundled read-only. No strategy, no hints, no web |
| Stack | reference scaffold + environment interface + world-state lens, pinned per run — the treatment |
Everything downstream of the wallet — bridging to the game chain, creating an operator wallet, registering an account, buying a team, questing — is the agent's to discover and execute on-chain. No resets, no human contact, no intervention: an outage is a measurement, not a reason to restart.
Three choices explain the shape:
- Cheap models, because the stack is the thing under test. A cheap model takes a tool description literally, retries the broken call, acts on the misleading field — exactly the defects we need surfaced. And it can run for days for a few dollars.
- Three unlike models, for coverage, not a leaderboard. One model would let the tool surface silently overfit to its habits.
- Quests as the yardstick, because each completed quest is a chain-verified proof that some slice of the game was discovered, sequenced and executed correctly — a clean proxy for "the surface is usable", and the objective the agents were actually given.
Every run measured quests against inference spent, what the agent learned and wrote down, and how it paced itself. The runs also recorded where each agent got stuck and which stack layer the stuck state implicated. That final observation drove the next run.
Run 1 — the baseline. On the first stack, the three arms diverged widely. Haiku finished the onboarding chain and five quests on day one, then burned its $10 in 17 hours. gpt-4o-mini ran for the full week without registering an account, while gemini remained stuck for six days until a single readable error unblocked it. Between 58% and 97% of every arm's on-chain writes reverted.
The sharpest finding concerned errors, not models: one human-readable validation message did in one turn what four days of opaque chain reverts could not. Fixed for the next run: the interface began checking an action's preconditions before sending it and returning a factual reason instead of a revert. The scaffold gained a loop breaker, session caps, self-chosen wake times, and cache-aware cost accounting.
Run 2 — the same box on the fixed stack. Reverts fell to 0–5%. All three arms registered; quests rose at fixed budget (haiku 5→8, gemini 3→5), and cost per quest fell by half or more.
A run-long outage of the game's inventory endpoint then affected all three arms, but each failed differently. Haiku believed it held no money while holding ~820 MUSU; gpt-4o-mini looped read-only for 95-plus sessions; and gemini sacrificed its own three Kamis while chasing a quest whose verb the tool description had blurred. With transaction waste gone, these failures exposed the next weak layer: perception. Legible errors fix transactions, not beliefs.
Fixed: world-state reads moved to a dedicated lens so the agent sees what the game client sees; the ambiguous tool description was rewritten; and every transaction now reports one of three explicit states.
Run 3 — aborted at 17 hours. A defect in our own run tooling, outside the published stack, had corrupted the agents' instructions from session one. The stack verified clean; the design carried over unchanged. Reported plainly, excluded from series results.
Run 4 — the clean re-run. Every arm finished the week with money left; 638 doomed writes were blocked before gas was spent against 6 that landed and reverted; every arm registered inside 3.5 hours; and the lens served every read for seven days. After looping read-only for 95-plus sessions in Run 2, gpt-4o-mini completed 7 quests in Run 4.
One remaining failure involved belief and omission. An arm spent 5.4 days dormant on a false conclusion that it re-read twenty times and never re-tested because the one read that would have corrected the conclusion was missing from the surface. Separately, one action — collecting harvested MUSU — had not succeeded on-chain once in two runs because its gas ceiling was below the real cost.
The pre-registered exit test held on all five checks. Fixed: the collect action and four siblings; per-objective quest progress in the lens; and a rebuilt revert-reason channel.
Run 5 — verification. Did the fixes work in the hands of an agent that does not know they exist? They did: of 36 collect attempts, 20 reached the chain and 0 reverted. The dormancy class did not recur, and the revert-reason channel corrected a failing call within one session. A cost meter running in shadow agreed with the run's own accounting to millionths of a dollar. Verdict MINOR-FIXES. The series closed.
Left: the stack converged — reverts went from most writes to almost none. Right: game progress did not — the best arm went 5, 8, 7, 9 quests, and one Kami reached level 2 in the whole series.
Two conclusions, and they point in different directions.
The stack is solid. Reverts collapsed two orders of magnitude; every arm registers within hours. Every write is either blocked with a reason, landed, or reverted with a reason the agent can act on. The collect action that failed twelve times in a row now lands every time it reaches the chain, and the money is counted to a millionth of a dollar. This is the instrument the rest of the program runs on.
The agents are still poor players. Quests barely moved across four completed runs.
Two of three models never opened the design document. The one that did open it guessed at file paths and got a quarter of them wrong.
Seven leveling tools sat in the schema every session but were called only four times in fifteen thousand calls. Meanwhile, MUSU accumulated in wallets while Kamis remained at level 1 or 2.
When arms stalled, they stopped instead of choosing a fallback. One arm spent 55 sessions asking a question to a user who does not exist.
Cheap models cannot be the whole story, because the same models fixed their behavior instantly whenever the fix arrived inside a tool result.
That delivery pattern does not change the result about the stack; it raises a separate question about the agents. The next design, knowledge delivery, holds the stack fixed and varies how the game's knowledge reaches the agent.
Newest first: what each run tested and what its findings changed.
| run | status | stack under test | what its findings changed |
|---|---|---|---|
| Run 5 | complete | scaffold v0.4.0 · interface v2.1.0, 101 tools · lens v0.3.0 · cost meter in shadow | exit test passed (MINOR-FIXES) — series closed; fixes verified in agent hands, meter validated |
| Run 4 | complete | identical pins to Run 3, fresh cohort | collect action + four siblings fixed (interface → v2.1.0); per-objective quest progress (lens → v0.3.0); revert-reason channel rebuilt |
| Run 3 | aborted | scaffold v0.3.2 · interface v2.0.0, 99 tools · lens v0.2.0 | two pre-launch gates on our own run tooling; design carried to Run 4 unchanged |
| Run 2 | complete | scaffold v0.2.0 · interface v1.5.1, 84 tools | world-state lens; sacrifice≠liquidate disambiguation; three-state transaction reporting; delegation availability gate |
| Run 1 | complete | scaffold @ 3ebd5b8 · interface v1.3.1, 84 tools |
legible pre-transaction validation (interface → v1.5.1); loop breaker, session caps, wake scheduling, cache-aware accounting (scaffold → v0.2.0) |
- Model — the model under test, through its provider's native tool-calling API. Within a run, the only thing that differs between arms.
- Workspace — the agent's only memory across sessions: a file tree that starts empty and that the agent writes itself. Fully inspectable.
- Scaffold — kami-agent — turns a stateless model into a persistent actor: session loop, file tools, self-chosen wake times, one adapter per provider. It fixes how the agent can act, never what to do.
- Environment interface — kami-harness
- lens — kami-lens — tools for every on-chain action and read, identical across arms, pinned per run. Where most of this series' findings landed.
- The world — Kamigotchi, a persistent, fully on-chain game with a live economy and human players; its design document, kamigotchi-gdd, is bundled with each agent.
Holding the scaffold fixed and swapping the model is the SWE-agent / BALROG / Vending-Bench methodology; this series runs it in the other direction — models fixed, stack swapped between runs.
- One seed per arm. Case studies with full public logs, not statistics.
- A live world, shared with humans. Reported as-lived; incidents (including PvP against study agents) are logged and annotated, never excluded.
- Run-over-run deltas are cross-epoch. They ride on world drift and on possible silent provider-side model updates; stack changes land as a bundle, so a delta is the stack effect, not per-change attribution.
- Dollars entangle capability with pricing. Tokens are the primary cross-run axis; dollar curves are shown alongside.
- This design does not rank models. Fast-tier arms under a $10 cap say nothing about frontier capability.
Design and run pages were published and git-timestamped before each run; every manifest pins exact commit SHAs of the scaffold, the interface, the lens and the design document, plus model strings, sampling parameters and price tables. Chain state is the public ground-truth action log.