Clay Seal

Clay Seal

[License: MIT] [Python] [Tests] [PyPI]

Incorporating business-process-logic constraints into AI systems.

Your agent has a $1,000 refund ceiling. It issues eleven refunds of $900. Every call is inside the per-refund limit, so every per-call check passes, and $9,900 goes out the door. Nothing that looks at one call at a time can see this.

Clay Seal sits in front of your tools and judges each call against the whole session: the grant, the running totals, where the arguments came from, and what the agent has already done.

Contents

Working on the code? docs/INTEGRATION.md names which modules the shipped gateway actually executes, which is the fastest way to tell the live path from the parts that are not wired in. The decision itself is SessionBroker._authorize_locked in clayseal/capabilities/broker.py; most refusals come from _floor in the same file.

Start here

If you are a coding agent, skip to the deploy runbook.

pip install claysealclayseal try

clayseal try takes about a minute. It runs two attacks in front of you and shows the gateway stopping them. There is nothing to configure, no key to get and nothing leaves your machine.

Every verdict there is decided live by the same gateway you would deploy. The picture is generated from a real run by python scripts/render_try_svg.py, and a test fails if it drifts from what the command prints, so it cannot become a screenshot of something that used to work.

Python 3.10 to 3.14. Two dependencies, cryptography and pyyaml.

On names. The directory is agentauth-capabilities, the package is clayseal, and the import is clayseal.capabilities. The project was renamed at 0.6; agentauth still imports as a deprecation shim. See Naming at the end for the detail.

If you are an agent

Do this in the project you are editing, in order:

clayseal try --fastclayseal howtoclayseal policy new > policy.yaml# rename your_* tools; put mailboxes in egress.recipients; then:clayseal policy lint policy.yamlclayseal skill --write

Python functions: Guardrail.from_policy_file("policy.yaml").wrap_all({...}) and bind the wrappers. Keys must match tools.allow. Construct one Guardrail per session (a new one resets ceilings). Catch Refused (budget / not granted) and StepUpRequired (held — typical for off-list email). Non-file tools go in paths.pathless.

Already an MCP server (Claude Desktop / Cursor): clayseal proxy, not clayseal serve. Do not point proxy at a plain .py file. clayseal howto is the runbook.

Use it in two lines

Wrap the tools you already have. Nothing else about your agent changes.

from clayseal.capabilities import Guardrail, Refused, StepUpRequired
def list_open_refunds():    return [{"invoice": "INV-001", "amount": 900.0},            {"invoice": "INV-002", "amount": 900.0}]
def issue_refund(invoice, amount):    return f"refunded {invoice} ${amount:.2f}"
guard = Guardrail.from_dict({    "version": 1,    "goal": {"id": "refund-run",             "summary": "Refund the invoices the customer disputed."},    "expires_at": "2030-01-01T00:00:00Z",    "tools": {"allow": ["list_open_refunds", "issue_refund"],              "harmless": ["list_open_refunds"],              "effects": {"list_open_refunds": "read", "issue_refund": "transfer"}},    "paths": {"pathless": ["list_open_refunds", "issue_refund"]},    "budgets": {"value": {"ceilings": {"refunds": "1000.00"},                          "tracked": {"issue_refund": {"arg": "amount",                                                       "budget": "refunds"}}}},})tools = guard.wrap_all({"list_open_refunds": list_open_refunds,                        "issue_refund": issue_refund})
# Call them exactly as before. The gateway decides before the tool runs.for row in tools["list_open_refunds"]():    try:        print(tools["issue_refund"](invoice=row["invoice"], amount=row["amount"]))    except Refused as exc:        print("refused:", exc.reasons)      # hand the reason back to the agent    except StepUpRequired as exc:        print("needs a human:", exc.reasons)

The first refund goes through. The second is refused, because the $1,000 session ceiling is already spent. Neither call reached your function.

The policy is inline here so you can paste the whole thing into a file and run it. In a real deployment it lives in its own YAML, where a security team can review it and a pull request can gate it. clayseal policy new > policy.yaml writes a commented one to start from, and Guardrail.from_policy_file loads it.

The wrappers keep the name, docstring and signature of your originals, so any framework that introspects them sees the tool it saw before. That covers LangGraph, the OpenAI Agents SDK, CrewAI and hand-written loops. Call the wrappers the same way you called the originals, positionally or by name.

Or put it in front of an MCP server

No code change at all. The gateway speaks MCP, so it sits between your agent and the server:

clayseal proxy --policy policy.yaml -- npx @your-org/mcp-server

Or paste this into Claude Desktop's MCP config, Cursor's MCP settings, or .cursor/mcp.json. The agent talks to Clay Seal; Clay Seal talks to the server:

{  "mcpServers": {    "billing": {      "command": "clayseal",      "args": ["proxy", "--policy", "policy.yaml",               "--", "npx", "@your-org/mcp-server"]    }  }}

Tools the policy does not grant are removed from the catalogue, so the agent is never told they exist.

Write the policy

This is a whole policy. It lints clean.

version: 1
goal:  id: refund-run  summary: Refund the invoices the customer disputed.
expires_at: 2027-12-31T00:00:00Z
tools:  allow:    [list_open_refunds, issue_refund]  harmless: [list_open_refunds]                 # a read spends nothing  effects:  {list_open_refunds: read, issue_refund: transfer}
paths:  pathless: [list_open_refunds, issue_refund]   # these act on invoices, not files
egress:  domains: [acme.example]  recipients: [[email protected]]               # a domain alone is every mailbox  bind_recipients: true
budgets:  value:    ceilings: {refunds: "1000.00"}              # dollars, for the whole session    tracked:      issue_refund: {arg: amount, budget: refunds}

Run clayseal policy lint policy.yaml before you ship. It catches the mistake that matters most: a tool that can spend money but debits no budget. On the file above it reports no errors and one warning (the ceiling is per session unless you bind a principal), which names a real decision you have not made yet.

Full reference: docs/POLICY.md.

See it stop the attack

From a checkout. examples/ has seven, each runnable with no key and no network:

python examples/02_the_proxy.py

tools advertised to the agent: list_open_refunds, issue_refund  (the server offers wire_funds; the policy does not grant it, so the agent is never told it exists)
  ok   issue_refund       INV-001   paid INV-001 $900.00  DENY issue_refund       INV-002   refused by policy: value_budget_exceeded  ...  DENY issue_refund       INV-011   refused by policy: value_budget_exceeded  DENY wire_funds         ops-float refused by policy: tool 'wire_funds' is not in this session's policy
the server executed 2 call(s):  list_open_refunds {}  issue_refund {"amount": 900.0, "invoice": "INV-001"}
clayseal proxy: 2 allowed, 11 denied, 0 held for approval; withheld from the catalog: wire_funds

Read the last block. A JSON-RPC error proves the agent was told no; the server's own ledger proves the refund did not happen, and those are different claims. The same run on the command line, which is the deployment shape a deployment actually uses:

clayseal proxy --policy examples/refund.yaml -- python examples/refund_server.py

How it works

You give the gateway a policy file and a goal for the session. It seals the goal at the start, so nothing the agent reads later can widen what was approved. Every tool call then goes through one decision point before it runs.

flowchart LR    P["policy.yaml<br/>reviewed and diffed<br/>like any other file"]    A["your agent"]    G{{"Clay Seal"}}    T["your tools<br/>or MCP server"]    H["a person"]    X["never runs"]    S[("session state:<br/>running totals,<br/>where arguments<br/>came from")]
    A -- "tool call" --> G    P -. "sealed at session start" .-> G    G -- "allow" --> T    G -- "step up" --> H    G -- "deny" --> X    H -- "yes, once, for<br/>these arguments" --> T    T -- "result" --> S    S -. "the next call is judged<br/>against all of this" .-> G

That loop at the bottom is the whole idea. The gateway does not just check a call, it checks a call against everything the session has already done.

A call gets one of three answers:

• allow and the call goes to the tool
• step up and the call waits for a person to approve it
• deny and the call never runs

Step-up exists because a wrong refusal is expensive. An autonomous attacker is stopped just as hard by a call that waits for approval as by one that is refused, and a legitimate agent is not stopped permanently. Denial is reserved for cases with positive evidence of a problem.

The checks that produce those answers run in a fixed order, cheapest and strictest first, so a call refused early never reaches the expensive layers.

1. Floor. The flat rules: has the grant expired, is this tool allowed, is this path in scope, is this destination on the egress list, is there budget left. Fastest and most of the denials.
2. Declaration. If the agent states a plan up front, the plan is checked against the sealed goal before any of it runs.
3. Content. Checks that a declared write matches the goal, and inspects the payload of a write that has an effect. Produces a step-up, never a denial.
4. Session state. Running totals, which values came from untrusted text, and any rules written against them.
5. Provenance. Where a destination came from. A payee named in the sealed goal is trusted; one that appeared in text the agent read afterwards is not.
6. Behavioural. Watches the shape of the session against the goal. Advisory by default: it escalates, it does not block. Its blocking tiers are also arithmetically incapable of firing until enough benign sessions have been observed to calibrate them, because a conformal p-value cannot go below 1/(n+1) and the alpha they are gated at sits under that floor. The detector names the inert tiers, so one that cannot fire does not look like one that looked and found nothing.

The word budget below means a running total the gateway keeps for the whole session: money, calls, or anything else countable. It is the only check that can see a sequence of individually legal calls adding up to something illegal, and the measurements below show it is what decides whether this helps you.

What it measures

The scenarios and the sweep live in the repository rather than the wheel, so this needs a clone. It takes about ten seconds and reaches no network:

git clone https://github.com/clayseal/clayseal-capabilities.gitcd clayseal-capabilitiespip install -e .python -m benchmarks.bpl_sweep --suite full

132 business-process scenarios, each with a scripted attack and its benign twin. Two columns, because either is trivially winnable alone: refuse everything and you win containment, allow everything and you win completion. The column that matters is the conjunction.

The attack was contained AND its benign twin completed, full suite, n=132:

Against dataflow taint that is 28.0 points [18.2, 37.9], exact McNemar p=1.2e-07. Of the 132 benign twins this gate refuses 2, and neither loses work; taint refuses 49 and loses work on 43.

The one number to read before the headline

39.4% is an average over two different cases, not a rate. What decides which case you are in is the rule, and you can tell by reading your own policy before running anything:

Fisher exact p = 6.5e-11.

So write your rules as ceilings on something you can count. "No more than $1,000 in refunds per session" is enforced. "Do not do anything inappropriate" is not: there is no running total for the gateway to keep. clayseal policy lint already flags a tool that can spend but debits no budget, and this measurement is what that warning is worth.

The rest of it

The suite above is one we wrote, which is the first thing to distrust. docs/EVIDENCE.md carries the evidence that is not ours, what the gate costs, and the limits, in full:

Every headline result and the command that reproduces it: benchmarks/results/README.md.

Where the boundary is

Three ways to place the enforcement point. They differ in what an agent has to do to get past them, and the difference is worth stating plainly instead of collapsing into one number.

The proxy also runs three checks the in-process path cannot. It screens every path a call names, not just the one the action carries. It refuses a message whose JSON has duplicate keys. And it holds an effectful call until earlier results arrive, so it is never asked where a destination came from before it has been told. The table in docs/POLICY.md lists the differences, and what an in-process integration has to do itself.

Most deployments want the proxy. The agent connects to clayseal proxy, and clayseal proxy runs the real MCP server, so a denied call is answered with a JSON-RPC error and the server subprocess never receives the frame. Tools outside the policy are also removed from the advertised catalog, so the agent does not plan around a tool it will then be refused.

The syscall tier compiles an envelope's egress and path scope into a sandbox policy and takes back an unforgeable verdict stream. The reference backend drives iVisor.

It catches one class nothing above it can. A DNS tunnel encodes its payload into subdomains, and the data leaves through the resolver. No tool is involved. There is no tool call, so authorize() is never asked, and every layer above denies nothing. On the captured trace iVisor denies all four queries and the tool-call layers deny none (syscall_tier.md).

It runs the other way too. Beaconing over an allow-listed channel gives iVisor nothing to refuse, because each syscall really is permitted; what is anomalous is the running total, and only the session budget holds that. Neither layer subsumes the other, which is the argument for running both.

iVisor is macOS only by construction: Hypervisor.framework allows one VM per process and applies an irreversible Seatbelt profile to its caller. The agentauth.sandbox_backends entry point makes the substrate swappable, and a Linux seccomp or Landlock backend is open work, not something we ship.

The gap this does not close

In-scope staging. An agent reads a secret-classed object inside its grant and writes the content to a publication-classed object inside the same grant. Both actions are authorized and the path scope cannot help, because the agent was legitimately given the workspace that holds both. Measured against an oracle attacker, the escaped-task set is byte-identical to allow-all (in_scope_exfiltration.md). The confidentiality flow tracker covers part of it as a step-up layer; wide fragment splits and unkeyed encodings remain open. Any containment claim for a coding agent has to carry this one.

The policy document

The authority is a file, so a security team can read it, diff it in a pull request, and gate a merge on it.

version: 1goal:  id: billing-triage-2026-08  summary: Triage the open billing tickets and email a summary to the ops archive.profile: supervised          # autonomous | supervised | benchmarkexpires_at: 2026-12-31T00:00:00Z
tools:  allow:    [list_tickets, read_ticket, write_summary, send_email]  harmless: [list_tickets, read_ticket, write_summary]  effects:  {write_summary: write, send_email: send}
paths:  allow: ["out/**", "tickets/**"]  deny:  [".env", ".git/**"]  arg_names: {write_summary: path}     # which argument carries the path  pathless:  [send_email]              # asserted to act on no path
egress:  domains: [acme-internal.com]  bind_recipients: true
budgets:  calls:    ceilings: {emails: 3}    tracked:  {send_email: emails}

clayseal policy show policy.yaml   # what it authorizesclayseal policy lint policy.yaml   # what a reviewer should ask about

lint exits non-zero on an error finding, so it works as a pre-merge gate. It reports what the gateway would refuse to start on, so the author does not find out from a traceback:

ERROR   untracked-effectful-tool issue_refund: reachable and in the 'value'        family but debits no budget, so no ceiling applies to it at allWARNING session-scoped-ceiling   emails: counted per session, so a second        session gets a second ceiling

The compiled policy carries a digest over the document, and the gateway attaches it to every decision, so an audit trail says which authority produced a decision and not only what the decision was.

Pointing it at your own tools

Two declarations do the work, and both exist because the defaults are tuned on benchmark catalogs, not on real ones.

tools.effects says what each tool does. The verb decides which floor rules apply, and guessing it from the name works on names like send_email and fails on names like terraform_destroy: of 24 tool names taken from widely used MCP servers, 17 are unrecognised by the classifier.

paths.arg_names says which argument carries the path. The gateway looks for file_path, path, filename and file; a tool that calls it target_dir or key yields no path, and a path scope that cannot find a path does not apply. An effectful call whose path cannot be resolved is refused, not allowed unchecked, so the failure is loud instead of silent.

clayseal policy lint names every tool that is missing either one. Read docs/POLICY.md before you write the first policy for a catalog you did not design.

If the person who signs off works in risk and not engineering, docs/CONTROLS.md says which obligations this produces evidence for, quoting the framework text where the mapping is exact and staying at the function level where it is not. It opens by saying what it is not: a library is not a control regime and cannot make anyone compliant with anything.

Writing the first one from what you already have

Two commands exist so the first policy is not written from a blank file. Both produce a draft a person finishes, never a grant.

# What the tools are called, from the server you already run.clayseal policy init -- npx @your-org/mcp-server
# What the organisation permits, from the document that already says so.clayseal policy draft delegation_of_authority.md
# Both halves in one file. This is the one worth running.clayseal policy init --rules delegation_of_authority.md \    -- npx @your-org/mcp-server > draft.yamlclayseal policy lint draft.yaml

init asks the server for tools/list and reads the tool names, the effect of each one, and the argument each carries its path in out of the schemas the server already publishes. draft reads the ceilings, windows, once-only rules, directories and allowed domains out of prose, from sentences like "a single vendor payment must not exceed $10,000".

Neither one is authority, for two different reasons. The document is an artefact edited by people who are not thinking about an agent, so whoever controls it would otherwise control the grant. The catalog is written by the server this policy constrains, so a server describing wire_funds as "reads the balance" would be writing its own limits. Three properties follow:

• Every rule cites the line of the document it came from, so a reviewer checks the YAML against the sentence without re-reading the source.
• A sentence that reads like a rule and did not translate becomes a TODO comment. A draft that looks complete is worse than one that admits what it dropped, because a rule that vanished in translation is one nobody notices.
• The catalog may raise a tool's effect and never lower one, and a server calling its own effectful tool read-only is reported, not believed. A tool that publishes no schema is not recorded as taking no path: "the server did not say" and "the server said no" are different facts.

What is deliberately left blank is budgets.tracked, where a ceiling meets a tool. The document knows the ceiling and the catalog knows which argument carries the amount; which tool debits which ceiling is in neither, and naming the wrong one splits a shared limit in two. Both are printed as commented suggestions for a person to connect.

Worked end to end on a 30-line delegation-of-authority document and a seven-tool AP server. It extracted 9 rules and left 3 sentences as TODOs. After review the gateway denies four things: a payment taking the rolling 24-hour total past $50,000, a second payment of an invoice already paid, a write to a .ledger file, and a write outside /finance/ap/. One of those TODOs is "the person who prepares a payment may not approve it", which is a real rule this layer does not express, and it appears as a comment in the output, not a silence.

Adding a rule for your own workload

Every knob above tunes behaviour someone else chose. This is where "in our shop X is also forbidden" goes, without forking:

from clayseal.capabilities import GoalSpecfrom clayseal.capabilities.deployable_stack import DeployableStackfrom clayseal.capabilities.session_rules import SessionRuleHit
def no_competitor_domains(action, session, *, goal_summary, egress_verbs):    if "competitor.test" in str(action.args or {}):        return SessionRuleHit("house-rules", "destination is a competitor domain")    return None      # None means "this rule has nothing to say"
goal = GoalSpec(query_id="refund-run", summary="Refund the disputed invoices.")stack = DeployableStack.from_goal(goal, house_rules=(no_competitor_domains,))

A hit becomes a step-up, never a denial. A rule written against your workload has not been measured against the traffic it will refuse, and a step-up halts an autonomous attacker just as hard while leaving a person able to say yes. Your rules run after the shipped ones, so a house rule cannot mask one that ships. A rule that raises is skipped and counted in session_rules.RULE_FAILURES, and the decision still goes through. A gateway that stops authorizing because a regex threw is worse than one that misses a rule.

The lower-level API

Guardrail above is the wrapper most integrations want. If you are building your own loop and would rather call the gateway directly, the decision API is one method:

from clayseal.capabilities.monitor.action import Actionfrom clayseal.capabilities.policy import compile_policyfrom clayseal.capabilities.tool_verbs import classify_verb
gateway = compile_policy({    "version": 1,    "goal": {"id": "billing",             "summary": "Triage tickets and email [email protected]"},    "expires_at": "2030-01-01T00:00:00Z",    "tools": {"allow": ["read_ticket", "send_email"],              "harmless": ["read_ticket"],              "effects": {"read_ticket": "read", "send_email": "send"}},    "paths": {"pathless": ["read_ticket", "send_email"]},    "egress": {"domains": ["acme-internal.com"], "bind_recipients": True},}).build()
agent_calls = [    ("read_ticket", {"id": "T-1042"}),    ("send_email", {"to": "[email protected]", "body": "3 open, 1 escalated"}),    ("send_email", {"to": "collector-metrics.example", "body": "3 open, 1 escalated"}),]
for step, (tool, args) in enumerate(agent_calls):    decision = gateway.authorize(Action(        step=step, tool=tool, resource=f"mcp:tool:{tool}",        verb=classify_verb(tool), args=args,    ))    print(tool, decision.outcome, decision.reasons)    if not decision.allowed:        continue                    # hand the reasons back to the agent    # run(tool, args)

examples/01_gateway.py (from a checkout) runs this end to end against a prompt injection planted in a ticket the agent was allowed to read. The fourth call is allowed and the fifth is held for a person.

What stops it there is the egress allow-list, which is a per-call rule. The injected address is off-domain, so the cheapest floor catches it and the provenance layer is never consulted. That is the gateway working in the right order, and it is not a demonstration of anything this document claims is distinctive, so the example prints which layer fired and examples/README.md runs the same session with the domain list removed, where provenance is what answers.

If your policy names a domain and an attacker names an address inside it, the floor has nothing to say and egress.recipients is what binds the mailbox. It is not on by default and clayseal policy lint does not require it, so a policy that grants a domain grants every mailbox on it.

Security posture

The guards fail closed unless the environment names itself development.

CLAYSEAL_ENV=development    # relaxes them, and says so once per process

Unset, or set to production, means an unpinned commit-token minting key is refused, a missing replay store is refused, an unsigned step-up approval is refused, and an intent envelope from an unpinned signer is refused. The polarity used to be the other way around, which meant every deployment that had not read this section accepted all four.

See docs/THREAT_MODEL.md for what is signed, who signs it, and what is out of scope.

Build from source

git clone https://github.com/clayseal/clayseal-capabilities.gitcd clayseal-capabilitiespython -m venv .venv && source .venv/bin/activatepip install -e ".[dev]"pytest python/tests -qpython examples/01_gateway.py

Optional extras:

pip install "clayseal[oidc]"     # live OIDC/JWKS verificationpip install "clayseal[spiffe]"   # SPIFFE Workload APIpip install "clayseal[redis]"    # shared replay and ledger storespip install "clayseal[monitor]"  # the learned trajectory scorer

Identity

The gateway does not need an identity layer. Bring verified claims from your own IdP, build an IdentitySession, and issue commit tokens from there. Adapters ship for SPIFFE JWT-SVID, OIDC, Auth0, AWS STS, Entra Agent ID, Azure AD, GCP, and A2A signed agent cards.

from clayseal.capabilities.identity_adapters import get_identity_provider
session = get_identity_provider("oidc").build_session(    verified_claims,          # your IdP already checked signature, aud, exp    evidence_verified=True,)

Documentation

docs/README.md is the index. The ones you are most likely to want:

• Your first ten minutes to go from the demo to your own agent
• Agent notes if you are a coding agent deploying this
• llms.txt for a machine-readable index
• Evidence for every measured number and the limit it does not cross
• API reference for the exported names, tiered by what most integrations actually use
• Developer guide to install it and wire it in
• Policy reference for what a policy file can say
• Threat model for what it defends against and what it does not
• Privacy and data handling for what it stores and what leaves the process

For reporting a vulnerability see SECURITY.md; to contribute see CONTRIBUTING.md and the code of conduct. Upgrading from agentauth-capabilities: docs/MIGRATION.md. Corpora and their licences: THIRD_PARTY.md. Cutting a release: docs/RELEASING.md.

Naming

The product, the distribution, the import root and the CLI are all clayseal.

Before 0.6 this shipped to design partners on a private feed as agentauth-capabilities, importing from agentauth.capabilities. Those import paths still resolve and emit a DeprecationWarning; they are removed in 0.7. The aliased module is the same object as the real one, so a plugin registered through the old path is visible through the new one. Migration is a search and replace: docs/MIGRATION.md.

Storage keys and wire identifiers were deliberately not renamed. The replay store still keys commit tokens under agentauth:commit:, because a gateway that silently stopped recognising the tokens it had already spent would reopen the replay window it exists to close.

clayseal.core, the shared contracts and crypto helpers, used to be a separate private distribution and now lives in this repository. The identity and receipts layers remain separate distributions and neither is required here.

License

MIT. See LICENSE.