custodian-kernel 0.3.1

Kernel-enforced authority and spend platform for AI agents

Custodian

The kernel that decides whether an AI agent's action is allowed — with 1,346 tests, cryptographic receipts, and 60-second verification.

When an AI agent can spend money, change infrastructure, or write to production, someone has to decide what's allowed. That decision can't live in the agent — the agent is the thing you're worried about. The decision has to live in a kernel that's outside the agent's process and outside the agent's own code path. Rules don't work. A smart enough model routes around rules. Prompts don't work. Prompts are soft. A model that reasons itself into approving its own refund will approve its own refund.

Custodian is that kernel. The model proposes. The kernel decides. The verifier proves. The kill switch stops. The receipt cryptographically records everything.

Verify in 60 seconds, no credentials, no cloning:

pip install custodian-kernel
custodian-verify

custodian-verify runs 3 checks: a planted-lie case through the deterministic verifier (CONTRADICTED), a live audit feed pull from the production dashboard, and a checkout-or-skip proof. 0 credentials, 0 cloning, 0 setup.

Or, for the deeper proof:

git clone https://github.com/KeyArgo/hermes-hackathon-2026
cd hermes-hackathon-2026
pip install -e ".[dev]"
python3 verify_kit.py

verify_kit.py runs 5 phases end-to-end with no credentials: re-introduces the self-approval bug to prove the test catches it, runs the 1,346-test suite, runs a planted-lie case, pulls the real Stripe PaymentIntent pi_3TkZWEPfSF4TGXT90AWlrnle, and tests the kill switch end-to-end.

What you get when the kernel runs

• @govern decorator — wrap any function with implicit kernel enforcement. Band, cap, kill switch — all automatic. Zero kernel imports in user code.
• CustodianMiddleware — drop-in ASGI middleware for FastAPI/Flask/Starlette. Governed routes return 402 on escalation, 403 on denial.
• GovernedReceipt — SHA-256 fingerprint of every governed action. The receipt is verifiable and cannot be forged.
• EventBus — pub/sub hooks for kernel lifecycle events. Wire Twilio SMS, Slack alerts, or any consumer.
• CustodianSession — sub-session band inheritance. A child session cannot exceed the parent.
• Authority bands L0-L4 — per-action caps, daily envelopes, margin gates, no-self-dealing, all opt-in.
• Operator-only kill switch — denies every request regardless of amount, band, or policy. Cannot be bypassed by the agent.

Use case

A 2.0% slice fraud team at a payments company uses 14 humans to manually approve agent-initiated refunds. They do 1,200/day. Each takes 2 minutes. $36k/yr in human time. Custodian replaces all 14 humans with a deterministic kernel — same throughput, no human in the loop for 95% of cases, full audit trail, single human via Twilio for the 5% edge cases. The agent cannot approve its own refund because the kernel is outside the agent's process. The model can propose. The kernel decides.

Any company running an AI agent with a Stripe account, a Modal spend, a NIM inference budget, a refund flow, or any other action that costs money or breaks something has this exact problem. Custodian is the kernel for it.

What's real

• 1,346 passing tests, 0 failed, 4 deselected (network only)
• Real Stripe test-mode PaymentIntent on record: pi_3TkZWEPfSF4TGXT90AWlrnle
• Real Twilio SMS escalation path
• Real OpenRouter API key wired in
• Real Modal + NVIDIA NIM in the demo commands
• 4 kernel bug fixes from adversarial review (kill switch fail-closed, fn_name in receipt, sub_session inheritance, receipt fingerprint coverage)
• Live dashboard: getcustodian.xyz
• Live operator panel: getcustodian.xyz/operator

Links

• Repo (GitHub): https://github.com/KeyArgo/hermes-hackathon-2026
• Repo (Gitea): https://git.argobox.com/KeyArgo/hermes-hackathon-2026
• PyPI: https://pypi.org/project/custodian-kernel/
• Live dashboard: https://getcustodian.xyz
• Operator panel: https://getcustodian.xyz/operator
• Hackathon entry: Hermes Agent Accelerated Business Hackathon (NVIDIA x Stripe x Nous Research)

Features

Core

• 1,346 tests, 0 failures (network tests excluded)
• Deterministic claim verifier (CONTRADICTED / VERIFIED / UNVERIFIABLE)
• Operator-only kill switch with resume logic
• Authority bands L0-L4 with per-request caps
• Real Stripe PaymentIntent on record (pi_3TkZWEPfSF4TGXT90AWlrnle)
• Real Twilio SMS escalation
• Self-approval regression test (proves the kernel fix)
• 100 governed tools in custodian/bundled_skills/

CLI Commands

• custodian request — spend decision with policy evaluation
• custodian audit — full audit ledger
• custodian demo-verify — 4 claim-verification scenarios (no creds)
• custodian earn-and-buy — closes the economic cycle on camera (no creds)
• custodian status-banner — one-screen kernel state (totals + last 5)
• custodian poison-tests — 5 planted-bad-claim tests (no creds)
• custodian beancount — export ledger to Beancount v2
• custodian confirm <id> — post-action confirm (60s deadline)

Policy Directives (all opt-in)

• daily_envelope: $50 — rolling 24-hour cap per band
• margins: { minimum_margin: $0.10, minimum_margin_pct: 20 } — refuse if margin too low
• band_after_task: L0 — auto-downgrade after a skill completes
• policies: { no_self_dealing: true } — block self-paying agents

Verify Kit

• python3 verify_kit.py — 4-phase self-verifying proof
  • Regresses the self-approval bug live
  • Pulls fresh dashboard + Stripe data
  • Runs the full test suite
  • Tests the kill switch end-to-end
• custodian demo-verify — 4 claim-verifier scenarios
• custodian poison-tests — 5 attack patterns the kernel catches
• custodian earn-and-buy — full economic cycle (earn → gate → spend → verify)

What Custodian is

Custodian is a kernel-enforced authority and spend platform for AI agents.

An agent cannot exceed its band or approve its own escalation because the boundary is enforced outside the agent's own process and outside its own code path — not by the agent's good behavior.

The agent submits a spend request. The policy engine decides: autonomous (within your configured band, no human needed) or escalation (over the cap, human approval required via Twilio Verify). The agent never holds the keys to both sides of that decision, so self-approval is structurally impossible, not just discouraged.

New here? Read docs/WHAT_THIS_IS.md first — a plain-language walkthrough of what this actually does, why it needs AI in exactly one place and nowhere else, and a worked real example end to end.

Wondering what this is actually for beyond one demo? See docs/BUSINESSES_THIS_UNLOCKS.md — the same enforcement pattern applied to five concrete, named business shapes, not just the one shown here.

Installation

pip install custodian-kernel

For development (clone first):

pip install -e ".[dev]"

Quickstart

# Scaffold a workspace
custodian init --dir myagent

# Edit the generated policy.yaml to configure authority bands
# (see docs/POLICY_LANGUAGE.md)

# Autonomous request (under the $2.00 default cap)
custodian request --amount 1.00 --description "API credits"

# Escalation request (over the cap — will warn about missing Twilio config)
custodian request --amount 50.00 --description "Server upgrade"

# Check authority state
custodian status

# View audit log
custodian audit

Documentation

• Architecture — design, flow diagram, privilege separation model
• Policy Language — complete YAML format reference
• Security — threat model, self-approval fix, verification model
• Security Hardening — credential/adapter/bridge scan and findings
• Caduceus — the credential broker (the agent never sees the value)
• Guard Adapters — money/security/privacy/guardrail hooks around every action
• Hermes Bridge — governed invoke surface + context-loss re-anchoring
• Verification — how to check every claim yourself
• Getting Started — 10-minute walkthrough

Tool Layer — 102 governed tools

Custodian ships a governed tool library. Every tool is a Hermes-compatible skill (SKILL.md frontmatter) that declares a custodian-band from L0–L4. The ToolRegistry auto-discovers them — no registration code needed.

custodian tools list              # show all 102 tools grouped by band
custodian tools run http-get --url https://example.com
custodian tools summary           # JSON band breakdown

Tool categories:

Category	Count	Band	Example
Utilities	8	L0	base64, hash-sha256, url-parse, json-transform, timezone, currency-convert
Web	5	L0–L1	http-get, http-post, web-scrape, web-search, news-search
Files	3	L0–L1	file-read, file-list, shell-exec (read-only allowlist)
Memory	5	L0	kv-get/set/delete/list, sqlite-query
Scheduling	5	L1	task-queue-add/list, cron-create/list/delete
Communication	6	L1–L2	email-send, sms-send, slack-message, discord-webhook, webhook-post, push-notification
Docker	4	L1–L2	docker-list, docker-logs, docker-start, docker-stop
GitHub	3	L0–L1	github-file-read, github-issue-create, github-pr-list
NVIDIA NIM	4	L2	nim-model-list, nim-job-submit, nim-job-status, nim-cost-estimate
Stripe (extended)	8	L2–L3	stripe-balance, stripe-customer-lookup, stripe-invoice, stripe-refund
Financial AI	5	L2–L3	modal-run, huggingface-infer, openai-complete, anthropic-complete
Calendar	5	L1–L2	calendar-list, calendar-create, calendar-update

Tools with missing credentials return {"ok": false, "stub": true} — the framework works without any env vars configured; stub tools show in the registry with their band and description so the capability surface is visible during review.

Authority bands

Band	Policy	Use case
L0	Always autonomous, no spend	Read-only data fetching
L1	Autonomous, trivial side effects	Creating records, sending low-stakes messages
L2	Autonomous up to per-action cap	AI inference, Stripe calls under threshold
L3	Always escalates to operator	Refunds, subscription changes, payouts
L4	Always escalates, unlimited scope	Reserved for future high-stakes tools

What's real right now

• A real Stripe (test-mode) PaymentIntent is on record: pi_3TkZWEPfSF4TGXT90AWlrnle — confirm it at Stripe's own API or dashboard.
• A real Twilio Verify integration sends SMS approval codes to an operator's phone. The code is never written to any file the agent can read.
• A real, operator-only kill switch (custodian kill --by <name> / custodian resume --by <name>) is wired into the live, authoritative spend.py — not a separate demo path. Verified live: a real autonomous spend succeeded, the kill switch was engaged, the exact same request was denied by the real script running inside the live sandbox, then released, then the real spend succeeded again. The full sequence is in the real audit log.
• 1,346 passing tests (4 network-dependent tests deselected by default), tested with Python 3.11+.
• The test suite includes test_self_approval_regression.py — a regression test for the exact security bug this design prevents. The fix was proven by deliberately reintroducing the bug, confirming the test failed, then restoring the fix. That test exists so the bug can never silently return.
• Public commit history at github.com/KeyArgo/hermes-hackathon-2026.

Don't take any of this on faith. Everything verifiable from pip:

pip install custodian-kernel       # install the kernel
custodian demo-verify              # live claim check against the running system
pip install custodian-kernel[dev] && pytest tests/   # 1,346 tests, 0 failures
git clone https://github.com/KeyArgo/hermes-hackathon-2026  # read every line

See docs/VERIFICATION.md for the full manual breakdown.

Limitations

• Only one approval backend is shipped: twilio_verify. Backends named other than twilio_verify or none are rejected at policy validation time.
• Only one storage backend is shipped: SQLite (via SqliteStorage).
• No multi-tenant support. No plugin marketplace. No general-purpose expression language in the policy DSL — the match vocabulary is a fixed, small set (skill name, context flags, spend-amount threshold).
• No third-party security audit has been performed.