hermes-tenuo

Give each Hermes agent a signed, expiring permission slip. Nothing outside it runs.

See it without installing Hermes or talking to a model:

pip install hermes-tenuo
hermes-tenuo demo

A nightly job gets a permission slip: read /data/reports,
write /tmp/nightly, then stop. Nothing else runs.
No Hermes process, no API key.

== Cron ==
The job does the work. Then it tries to leave the slip.
  ALLOW  read_file  path=/data/reports/q3.csv
  ALLOW  write_file  path=/tmp/nightly/report.md
  DENY   read_file  path=/opt/private/payroll.csv
         Constraint 'path' not satisfied: value does not match constraint  ← /opt/private/payroll.csv is not under /data/reports
  DENY   terminal  command=ls
         Tool 'terminal' is not authorized  ← terminal is not on the slip
  (one second later)
  DENY   read_file  path=/data/reports/q3.csv
         Warrant has expired  ← the job window ended

That slip is a Tenuo warrant: signed, expiring, checked before
the handler runs. Same check, two more shapes:

== delegate_task ==
Same rule, after a handoff. The researcher was only granted web_search.
  [orchestrator] ALLOW  read_file  path=/data/input.csv
  [orchestrator] ALLOW  delegate_task  task=research q3  context=web_search only
  [researcher] ALLOW  web_search  query=AI papers 2026
  [researcher] DENY   write_file  path=/data/output/x.md
         Tool 'write_file' is not authorized  ← the researcher was not granted write_file

== Gateway ==
Same server, two slips.
  [analyst] ALLOW  read_file  path=/data/reports/q1.csv
  [analyst] DENY   write_file  path=/data/output/x.txt
         Tool 'write_file' is not authorized  ← write_file is not on the analyst's slip
  [viewer] ALLOW  read_file  path=/data/public/faq.md
  [viewer] DENY   read_file  path=/data/reports/q1.csv
         Constraint 'path' not satisfied: value does not match constraint  ← /data/reports is not on the viewer's slip

A Tenuo warrant is that slip. Each Hermes tool call is checked against it — tool name and arguments — before the handler runs. A delegate_task child only gets what the parent granted. A gateway user carries their own slip. Keys and decisions stay local.

The plugin returns the denial as the tool result, so the model sees why the handler never ran:

read_file  path=/opt/private/payroll.csv
Constraint 'path' not satisfied: value does not match constraint

For a recorded session with a real model and a planted prompt injection, see docs/walkthrough.md.

Install into Hermes

1. Install.

# into the venv Hermes uses (pulls in tenuo):
pip install hermes-tenuo

# or as a directory plugin under ~/.hermes/plugins:
hermes plugins install tenuo-ai/hermes-tenuo
pip install "tenuo>=0.3.1"   # Hermes does not install plugin dependencies

To run the latest unreleased code instead: pip install "git+https://github.com/tenuo-ai/hermes-tenuo.git".

Requires Hermes Agent 0.20 or newer. A nightly job loads the plugin through the plugin loader of upstream Hermes main, both install routes; the badge above is its latest result. The pip route installs tenuo>=0.3.1 for you; the directory route needs the extra pip install line above.

2. Mint a warrant. This generates a key pair and a warrant, and prints the exact config block to paste.

hermes-tenuo mint --ttl 1h \
  --allow read_file:path=/data \
  --allow web_search

# ~/.hermes/config.yaml   (printed by the command above)
plugins:
  enabled:
    - hermes-tenuo
  entries:
    hermes-tenuo:
      warrant: <base64>            # or a path to a .warrant file
      trusted_root: <base64>       # the public key that signed it
      signing_key_env: TENUO_SIGNING_KEY

export TENUO_SIGNING_KEY=<printed by mint>

3. Check the wiring, then run Hermes.

hermes-tenuo doctor
hermes

Ask the agent to read /opt/private/payroll.csv. It gets the same denial as the tool result. Load skill_view("hermes-tenuo:tenuo-scope") to mint a warrant for a cron job, a delegate_task child, or a gateway session.

Scoping arguments

Each --allow names a tool and, optionally, constraints on its arguments. A tool with no constraints is allowed with any arguments.

Any argument the warrant does not name is unconstrained for that tool. The --ttl flag takes 30m, 1h, 7d, and so on (default 24h).

For anything the flag syntax cannot express, mint in Python with the full constraint set (numeric ranges, case-insensitive paths, and more):

import base64, os
from tenuo import SigningKey, Warrant, Subpath, Pattern, Range

control_key = SigningKey.generate()   # keep private; its public key is trusted_root
agent_key = SigningKey.generate()     # export its secret as TENUO_SIGNING_KEY

warrant = (
    Warrant.mint_builder()
    .holder(agent_key.public_key)
    .capability("read_file", path=Subpath("/data"))
    .capability("web_search", query=Pattern("acme*"))
    .capability("scale_cluster", replicas=Range.max_value(10))
    .ttl(3600)
    .mint(control_key)
)

path = os.path.expanduser("~/.hermes/tenuo/warrant")
os.makedirs(os.path.dirname(path), exist_ok=True)
with open(path, "w") as f:
    f.write(base64.b64encode(warrant.to_bytes()).decode())

Point warrant: at that file. Set trusted_root to the base64 of control_key.public_key.to_bytes() and TENUO_SIGNING_KEY to the base64 of agent_key.secret_key_bytes().

What it unlocks

Runnable versions of the first three live in examples/.

See what your agent actually calls

Every decision is appended to a local JSONL audit log, on by default at ~/.hermes/tenuo/audit.jsonl (profile-aware under HERMES_HOME). No account needed.

hermes-tenuo audit --last 20          # one line per tool call
hermes-tenuo audit --denied           # only what the warrant blocked
hermes-tenuo audit --json | jq ...    # raw records

2026-09-12 10:00:00  ALLOW  read_file  path=/data/q3.md
2026-09-12 10:00:01  DENY   terminal  command=ls  — Tool 'terminal' is not authorized

Not sure what to allow yet? Set on_denial: log. Every call is still checked and recorded, but nothing is blocked. Run the agent, read the denied lines, tighten the warrant, then remove the line (the default is block).

plugins:
  entries:
    hermes-tenuo:
      warrant: ~/.hermes/tenuo/warrant
      trusted_root: <base64>
      on_denial: log

How it works

The decision itself runs in Tenuo's Rust core: signature, expiry, holder proof-of-possession, and every argument constraint. The plugin holds only the issuer's public key. It never sees the key that minted the warrant.

Denials are returned to the model as the tool result, so the agent can explain what it was not allowed to do. Raise the hermes_tenuo logger level to see the same lines as an operator.

Coverage

On upstream Hermes, enforcement runs at pre_tool_call. That covers every tool call made through the agent loop, including the tools run_agent.py handles before the registry (todo, memory, session_search, delegate_task). It does not cover:

• callers that pass skip_pre_tool_call_hook=True;
• plugins that call registry.dispatch() directly;
• the execute_code sandbox's internal tool dispatch.

A registry-level hook that closes all three is proposed upstream in hermes-agent#32719. The plugin detects it at load time and uses it automatically, and hermes-tenuo doctor reports which path is active.

Neither path inspects what an execute_code script does on its own, such as subprocess.run(...). Use a container backend (Docker, Modal, Daytona) for that threat model.

CLI

hermes-tenuo demo        # local allow/deny transcript (no Hermes process)
hermes-tenuo mint --allow TOOL[:ARG=VALUE,...] [--allow ...] [--ttl 1h] [--task ID] [--output full|yaml|env]
hermes-tenuo status      # what the plugin will load from config and env
hermes-tenuo verify      # signature (if trusted_root is set), expiry, capabilities
hermes-tenuo doctor      # end-to-end install check
hermes-tenuo audit [--last N] [--denied] [--json] [--path FILE]

Run doctor from the same venv Hermes uses. It checks plugin discovery, config wiring, warrant validity, that the signing key matches the warrant holder, and which enforcement path is active. Run it after every install.

Configuration reference

All keys live under plugins.entries.hermes-tenuo. Each has an environment variable equivalent.

Keep secret key material in env vars or a secrets manager, never in config.yaml.

Things to know

• Enabled but unconfigured is a no-op. Without a warrant, the plugin loads, logs a warning, and enforces nothing. doctor fails that check.
• Multiplexed profiles. Under gateway.multiplex_profiles, TENUO_* values are read through Hermes get_secret, so put each profile's keys in that profile's .env. A secondary profile does not inherit the launch profile's credentials.
• Rotate by re-minting. The control key is not saved by mint. To change scope, mint a new warrant and replace the config values; the old warrant stops being accepted when you change trusted_root, or when its TTL ends.

Managed scope (fleet and multi-user)

Hermes overlays a root-owned /etc/hermes/config.yaml on every user's config. hermes-tenuo reads its keys through the same loader, so an administrator can pin the warrant and trust anchor for the whole fleet:

# /etc/hermes/config.yaml  (root-owned)
plugins:
  entries:
    hermes-tenuo:
      warrant: /etc/hermes/tenuo/fleet.warrant
      trusted_root: <base64>
      on_denial: block

Pin warrant, trusted_root, and on_denial. Leave signing_key_env to the environment. Override the managed directory with HERMES_MANAGED_DIR for containers or non-standard layouts.

Connecting a control plane (optional)

Everything above runs from files and environment variables on one machine. That is the right shape for one developer and a handful of agents. Once you run a fleet of Hermes agents, cron jobs, and gateway users, the hard part stops being the check itself and becomes operating the authority around it: who may mint production warrants, how keys rotate, how a bad warrant is pulled back before its TTL ends, and where you look when something was denied at 3 a.m. A Tenuo control plane takes that over.

When TENUO_CONNECT_TOKEN is set, the Tenuo SDK inside this plugin connects on its own and every allow and deny decision from every Hermes agent streams there, with nothing else to configure. On top of that stream the control plane gives you:

• Revocation before expiry. Pull a warrant, a key, or an agent the moment something looks wrong instead of waiting for the TTL. Revocation lists are published to every verifier.
• Central issuance and rotation. Mint per-job warrants from policy rather than by hand, and rotate root and holder keys on a schedule without touching each agent's environment.
• Human approval gates. Route calls to sensitive tools to a person, so the agent can proceed only with a signed approval.
• One searchable audit trail. Signed receipts from every agent, session, and profile in one place, instead of one audit.jsonl per machine.

Tenuo Cloud is the managed version of that control plane. See tenuo.ai for access, or the Tenuo repo for running your own.

License

Apache-2.0