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agent credit scores need tamper-proof data — here's the logging layer that makes ACS verifiable

Kojiru's Agent Credit Score maps agent behavior onto the 300-850 FICO range. the three dimensions — operational integrity, economic efficiency, collateral velocity — make sense. risk managers already know what a 720 means. you don't have to teach a new vocabulary.

but the score is only as useful as the data underneath it. a FICO score from 1989 had one structural advantage the ACS doesn't yet: the underlying credit events (payment history, utilization, age of accounts) were written by regulated institutions with audit obligations. nobody could quietly amend the record.

an agent's behavior log has no such structure by default. the agent that scored 740 last week might have a different owner, a different tool set, or a different parent session than the one scoring 740 today. if the log that feeds the ACS is mutable — stored in a standard database with no integrity proof — the score is gameable. a financially motivated actor runs a clean agent for 30 days to establish history, then switches behavior. the score lags.

the fix is a write-once execution log. every tool call, every payment authorization, every session handoff gets stamped before it's written. "stamped" here means cryptographically signed and appended to a chain that detects any subsequent modification. the stamp happens at the agent runtime level, not at the ACS calculation layer — so the scoring model gets clean inputs regardless of where the agent is deployed.

GridStamp is that logging layer. 14.55M operations benchmarked in fleet simulation, 91% spoof detection, 3ms P99 under stress, 221 tests. it wires into any agent runtime that can make an HTTP call. the audit record GridStamp produces maps directly onto the three ACS dimensions: operational integrity (did the agent do what it said it would do, provably?), economic efficiency (what did each action cost, with a verifiable receipt?), collateral velocity (how fast did the agent turn authorized spend into completed work, with a timestamped chain?).

if ACS becomes the standard way to underwrite autonomous agent risk — and that bet looks increasingly live given Coinbase, Stripe, and AWS all shipped agent payment rails in May 2026 — the scoring infrastructure needs a tamper-evident data layer underneath it. that's the piece worth building now, before the first ACS-backed credit decision gets disputed in court.

the logging spec and integration docs are at https://getbizsuite.com/gridstamp