AdversaryGate

High AI usage ≠ high confidence. The cost of an agentic coding pipeline is not the model's intelligence — it is the pipeline's self-deception.

A fail-closed verification gate for patches written by AI coding agents. It runs your tests on the baseline and on the patch, mutation-tests only the lines the patch wrote, and answers MERGE, BLOCK or INCONCLUSIVE — where uncertainty is a first-class result instead of a silent approval. CLI, GitHub Action and MCP server.

Python only, for now. It measures Python/pytest repositories; on other stacks it runs your suite via --test-command but answers INCONCLUSIVE, never MERGE — see Language support.

pip install adversary-gate

🎬 Watch it decide (60 seconds)

B and C are the same patch. Same code, same tests, same execution. The only difference is that C brought evidence (--diff + --coverage-json); B brought none.

That middle row is the whole product. An unproduced measurement is not a measurement, so it cannot clear a floor — and a number nobody can re-derive is an opinion with a false precision label.

python3 demo/demo.py          # runs the three scenarios; exits non-zero if one regresses
python3 demo/render_gif.py    # rebuilds demo/demo.gif from the captured frames

demo/demo.py is an acceptance test, not a screenshot: it builds the fixtures, runs the real CLI as a subprocess, reads the real exit codes, and fails if any of the three decisions changes. Its evidence artefacts are checked in under demo/out/.

INCONCLUSIVE is not an error. It is the gate saying "I did not measure that", and it is exit 2 so CI treats it as "do not merge yet", not as "pass". See How diff_coverage gets its value for the one-step path from INCONCLUSIVE to MERGE.

Related MCP server: agent-guardrail

🚀 Quick Start (CLI & GitHub Action)

First run, in one minute

From the root of a git repository whose agent's change sits on top of main (new files tracked: git add -N them), with pip install adversary-gate coverage:

BASE=main                                         # the commit before the agent's change
W=$(mktemp -d)
git worktree add -q "$W/before" "$BASE"           # the baseline, exactly as committed
git diff --no-ext-diff "$BASE" > "$W/changes.diff"  # baseline -> your working tree
coverage run -m pytest -q && coverage json -q -o "$W/coverage.json"
adversary-gate --baseline "$W/before" --patch . \
  --claim tests/test_shop.py::test_discount_never_negative \
  --diff "$W/changes.diff" --coverage-json "$W/coverage.json" > "$W/answer.json"
echo "exit $?"                                    # 0 MERGE, 1 BLOCK, 2 INCONCLUSIVE
python -c "import json,sys; a=json.load(open(sys.argv[1])); print(a['decision'], '-', a['reason'])" "$W/answer.json"
git worktree remove --force "$W/before"

Replace the --claim with the test that proves your fix (path::test). On a correct one-line fix, expect this first answer:

exit 2
inconclusive - every claim held and the fix is proven, but suite strength's lower bound is 0.38,
below the 0.75 floor (1/1 mutants killed): the change is too small to measure at this floor,
which takes at least 5 killed mutants; see next_steps

That is not a failure: the fix is proven, and the gate says plainly that it could not measure how strong the tests are on a change this small. See Small changes.

Command-Line Usage

adversary-gate \
  --baseline /path/to/before \
  --patch /path/to/after \
  --test-path tests/test_auth.py \
  --test-id test_token_expiry \
  --diff changes.diff \
  --coverage-json coverage.json \
  --model "${AGENT_MODEL_NAME}" \
  --evidence-log evidence.jsonl \
  --report

Produce the two artefacts in your own pipeline, for example:

git diff --no-ext-diff baseline...patch > changes.diff
coverage json -o coverage.json          # after: coverage run -m pytest

Which tests? Name several, or let coverage say

One run verifies any number of claims, and the decision is over all of them (one REFUTED blocks; one UNVERIFIED makes it INCONCLUSIVE):

adversary-gate ... --test-path tests/test_auth.py --test-id test_expiry --test-id test_refresh
adversary-gate ... --claim tests/test_auth.py::test_expiry --claim tests/test_api.py::TestLogin::test_ok

Or name none, and let the gate verify the tests that executed a changed source line — read from coverage.py's per-test contexts, not guessed:

printf '[run]\ndynamic_context = test_function\n' > contexts.coveragerc
coverage run --rcfile=contexts.coveragerc -m pytest
coverage json --show-contexts -o coverage.json
adversary-gate --baseline before --patch after \
      --diff changes.diff --coverage-json coverage.json --discover-claims

A test file the patch rewrote is still picked, and judged with the baseline's copy of it (the baseline oracle, above); it is named under discovery (rewritten_test_files_judged_by_baseline), next to anything that could not be resolved to a node id, and the cap (--max-claims, default 10) with how many it cut. From 3.0.9 a cut test is not left unjudged: with the full suite off (--full-suite-path ""), a patch whose kept claims would merge is INCONCLUSIVE instead, and the reason says to raise the cap or run the suite. A report recorded without contexts is a usage error (exit 3), not "no tests".

Your project's interpreter, its limits, its environment

adversary-gate ... --python .venv/bin/python \
      --timeout 120 --cpu-seconds 60 --memory 2G \
      --pass-env PATH --env PYTEST_DISABLE_PLUGIN_AUTOLOAD=1

The same choices apply to every run — claims, mutants and the collateral suite — except time and memory: the whole suite gets its own limits, because ones sized for a single test killed every suite of real size on both sides (out of time, or pytest dying with MemoryError under 512M of address space): never a MERGE (two failing sides are unverifiable), but the regression the suite would have caught came back INCONCLUSIVE instead of BLOCK (AG-033). The output records them under execution, with the names of the variables and never their values. A run the memory limit killed (MemoryError, Fatal process out of memory, Could not reserve enough space…) is reported as the harness dying, not as a failing test: it says nothing about the patch.

Not a pytest suite, or running a patch you have not seen?

# 1. run your own command instead of pytest (any language, any runner)
adversary-gate --baseline before --patch after \
      --test-path run_tests.sh --test-command "./run_tests.sh"

# 2. wrap every run in bubblewrap: no network, private PID//tmp,
#    read-only system, only the repo writable
adversary-gate ... --sandbox bwrap

# 3. both together -- the usual shape for a patch from someone else
adversary-gate ... --test-command "make check" --sandbox bwrap \
      --require-network-isolation

--test-command needs no --test-id (there are no node IDs to name), and it feeds the collateral full-suite run too unless you pass --full-suite-command. --sandbox bwrap needs bubblewrap installed and refuses to start without it — see Execution boundary for exactly what it does and does not contain.

Exit Codes for CI Integration:

• 0 — MERGE: Every claim executed cleanly and cleared coverage & suite strength floors.

• 1 — BLOCK: Regressions or collateral suite failures detected.

• 2 — INCONCLUSIVE: Infrastructure error, missing test, missing coverage evidence, or weak suite (blocks merge).

• 3 — USAGE_ERROR: Bad arguments, malformed JSON, or a coverage claim that was not declared as untrusted.

GitHub Action Integration (action.yml)

One ref in. base-sha derives the baseline, the diff and the coverage report itself, so the first thing you install is not a INCONCLUSIVE:

name: Verification Gate

on: [pull_request]

jobs:
  verify-agent-patch:
    runs-on: ubuntu-latest
    steps:
      # base-sha is a commit in history: this is not optional.
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      # Your Python, your dependencies -- the tests run here.
      - uses: actions/setup-python@v5
        with:
          python-version: '3.11'
      - run: pip install -r requirements.txt pytest coverage

      - name: Run AdversaryGate
        uses: Sanflow10/adversary-gate@v3
        with:
          base-sha: ${{ github.event.pull_request.base.sha }}
          evidence-log: 'evidence.jsonl'

No test is named: the Action records coverage per test and verifies the tests that executed the lines the pull request changed. Name them yourself with claims (one path::test per line) or test-path + test-id (one id per line); either one turns discovery off unless discover-claims: 'true'.

Any non-zero exit fails the step, and that is the safe default. BLOCK (1), INCONCLUSIVE (2) and a usage or harness error (3/4) all turn the check red. Do not add continue-on-error and stop there: that lets a BLOCK through along with everything else. If some pull requests are INCONCLUSIVE by nature (a change to C++ or SQL, which the gate runs but cannot measure), keep the step from failing and branch on the exit-code output instead (2.13.0 and later):

      - name: Run AdversaryGate
        id: gate
        uses: Sanflow10/adversary-gate@v3
        continue-on-error: true
        with:
          base-sha: ${{ github.event.pull_request.base.sha }}

      - name: Act on the decision
        if: always()
        env:
          EXIT_CODE: ${{ steps.gate.outputs.exit-code }}
        run: |
          case "$EXIT_CODE" in
            0) echo "MERGE" ;;
            2) echo "::warning::INCONCLUSIVE: the gate could not measure this change; a human decides" ;;
            1) echo "::error::BLOCK"; exit 1 ;;
            *) echo "::error::the gate did not finish (exit '${EXIT_CODE}')"; exit 1 ;;
          esac

Branch on exit-code, not on decision: a run that printed no verdict (exit 3/4) still reports decision: inconclusive, and an empty exit-code means the Action stopped before the gate ran. Let 2 pass only where you know the gate cannot measure the change, for example with paths: on a separate workflow; everywhere else, leave the default.

It runs your tests on your Python. The gate itself lives in a private venv on its own 3.12, and your job's python is the same before and after the step. The tests run on the first python/python3 on PATH that can import pytest — the one your setup-python step put there — or on the interpreter you name with python:. When there is none, they run on the gate's own and the run says so. timeout, cpu-seconds, memory, pass-env and env are the CLI flags above.

Which ref? v3.0.17 carries every fix, and the Release workflow that publishes it also moves the floating v3 tag, which follows every 3.x release. Versions before 3.0.4 are unsupported. @main follows main and picks up whatever lands next. For anything that matters, pin the full commit SHA instead (uses: Sanflow10/adversary-gate@<full-sha>), which cannot be moved under you.

What that does, and where each piece comes from:

If the ref is not in your local history the Action stops with exit 4 and tells you fetch-depth: 0 rather than measuring against a baseline it invented. coverage-command defaults to coverage run -m pytest + coverage json (with per-test contexts when claims are discovered), and coverage in it is coverage.py on your interpreter — installed beside it, not into it, when it is missing. Override it to point at your own suite, or pass coverage-json to supply the artefact yourself.

Everything it derived is one git diff you could have run by hand. When you would rather assemble it yourself — a monorepo, a generated diff, coverage from a non-coverage.py tool — pass the paths explicitly instead:

      - name: Collect coverage evidence
        run: |
          git diff --no-ext-diff ${{ github.event.pull_request.base.sha }}...HEAD > changes.diff
          python -m pip install pytest coverage
          coverage run -m pytest
          coverage json -o coverage.json

      - name: Run AdversaryGate
        uses: Sanflow10/adversary-gate@main
        with:
          baseline: './baseline'
          patch: './patch'
          test-path: 'tests/test_token_expiry.py'
          test-id: 'test_token_expiry'
          diff: 'changes.diff'
          coverage-json: 'coverage.json'
          coverage-floor: '0.80'
          suite-strength-floor: '0.75'
          model: '${{ matrix.model }}'
          evidence-log: 'evidence.jsonl'

Without diff + coverage-json (and without base-sha to derive them) the Action reports INCONCLUSIVE, because there is no coverage evidence to clear the floor with. If you deliberately want to assert the number instead, set coverage-ratio and coverage-source: 'untrusted'.

📦 Installation

pip install adversary-gate

Check what PyPI is serving before you trust it — pip index versions adversary-gate. Versions before 3.0.4 are unsupported: each lacks fail-open fixes (a patch reaching MERGE it should not) that came after it. PyPI gets a release when a signed tag is pushed (Trusted Publishing, AG-008 closed), and the GitHub Release below gets the same build. Every other route works too, and none of them needs PyPI:

# straight from the repository
pip install git+https://github.com/Sanflow10/adversary-gate.git

# or clone it
git clone https://github.com/Sanflow10/adversary-gate.git
cd adversary-gate && pip install .

# or don't install it at all
PYTHONPATH=src python3 -m adversary_gate --help

Install a released wheel

git+… always follows main. For a fixed, versioned build there are two, and today they carry the same code:

# PyPI -- 3.0.17. Versions before 3.0.4 are unsupported: each lacks fixes the
# CHANGELOG lists after it.
pip install adversary-gate==3.0.17

# GitHub Release -- 3.0.17: every fix in this document.
# The tag carries the "v", the filename does not.
pip install https://github.com/Sanflow10/adversary-gate/releases/download/v3.0.17/adversary_gate-3.0.17-py3-none-any.whl

The second is a plain public URL — no PyPI, no GitHub login, no git — and it needs a GitHub Release for that tag to exist: if it answers 404, the Release for v3.0.17 has not been published yet. A release takes two steps, in this order, and only the first is done by hand:

1. A person pushes a signed tag: git tag -s vX.Y.Z -m "X.Y.Z" and git push origin vX.Y.Z. The push starts Publish to PyPI, which builds the tag's own tree — the core and the MCP package, adversary-gate-mcp — and uploads both through Trusted Publishing, so every file carries a PyPI provenance attestation. It refuses a tag whose pyproject.toml names another version, and it reads no API token. Before it builds anything it checks the tag's signature with git verify-tag against the key in the repository variable RELEASE_ALLOWED_SIGNERS (an allowed_signers line, kept outside the tree so a push cannot bring its own key): a lightweight tag, an annotated tag with no signature, a signature from another key, or no variable at all, and nothing is published.

2. Actions → Release → Run workflow. It refuses to run without that tag, or with one the same signature check refuses, and refuses while PyPI lacks either package. Then it runs the full test suite and refuses to publish if it fails, builds the wheel and sdist, installs the wheel into a clean interpreter, attaches them to the release, and moves the floating tag of the release's major line (v3) — only forward, so re-releasing an old version does not drag it back.

Publish to PyPI → Run workflow with a tag finishes a run that stopped halfway: files already on PyPI are skipped, never replaced.

Until 3.0.3 the Release workflow created the tag itself, with the workflow's token, and uploaded the core alone with an API token. Events from that token start no other workflow, so for 3.0.2 and 3.0.3 the PyPI publisher never ran: uvx adversary-gate-mcp kept serving 3.0.0, the core files carry no attestation, and those tags are not signed. Like every version before 3.0.4, they are unsupported.

PyPI

Versions before 3.0.4 are unsupported. The audit this project grew from was run against 2.0.1, which predates every fix in this document: --diff and --coverage-json did not exist yet (AG-002).

AG-008 is closed (2026-10-04). The Trusted Publisher is registered in the PyPI project settings (Sanflow10 / adversary-gate / pypi-publish.yml, no environment), and 2.4.0 went up through it — OIDC, no token — with PyPI provenance attestations attached to the wheel and the sdist. Until then the upload step had failed on every tag with invalid-publisher: valid token, but no corresponding publisher, and 2.2.0/2.3.0 never reached PyPI at all.

🤖 Coding agents: Hermes (MCP) and Jev (triage)

Two integrations, one rule: nothing an integration says can make the gate more lenient.

An agent that cannot grade itself — MCP server (Hermes, any MCP client)

pip install "adversary-gate[mcp]"          # in an environment the agent cannot write to
# or, without installing anything:  uvx adversary-gate-mcp  (the same server, as its own PyPI package)
adversary-gate-mcp                         # stdio MCP server
adversary-gate-mcp --print-hermes-skill    # SKILL.md for ~/.hermes/skills/adversary-gate/
adversary-gate-mcp --print-hermes-config   # the mcp_servers block for ~/.hermes/config.yaml

Tools: verify_repo(repo, claims?, pytest_args?, base_ref?) and gate_policy(). verify_repo judges the repository's working tree — committed or not, untracked files included — against a baseline: it writes the baseline commit's tree into a scratch directory, every file as committed (not with git archive, which applies the repository's export attributes — AG-044), writes the diff, runs coverage.py with per-test contexts (data file in a scratch directory, nothing written into the repo), discovers the claims when none are named, and runs the gate. The answer carries decision, mergeable, fix_proven, every claim's oracle, and the full artefact.

The agent says what to judge; the operator says how strictly, and against what. The tool arguments name evidence only. Everything that decides the answer comes from the server's environment, set in the agent's MCP config by whoever runs it:

pytest_args accepts test paths only; an option (-p evil) is refused. The shipped Hermes skill tells the agent to call the gate before saying "done", to fix code rather than tests on block, to never report inconclusive as success, and to promote a self-written skill only on merge.

Risk triage with Jev (TypeSafe AI) — advice that can only tighten

export TYPESAFE_API_KEY=sk-...
adversary-gate ... --diff change.diff --triage jev     # --triage-threshold 0.70 by default

Jev is a calibrated decision model: text and a schema in, a typed answer with a probability out, in ~100 ms. The gate asks it one choice (low / medium / high risk) and one yes/no (does this change a contract callers rely on?). A confident high raises this run's floors — strength confidence to 0.95, coverage floor to 0.90 — so a 5-of-5 mutant score that merges an ordinary change is INCONCLUSIVE for a risky one. A low, a medium, an unconfident high, an error or a timeout change nothing; there is no path from Jev's answer to a more lenient decision, which is what makes it safe to feed it text the patch's author wrote. The answer is recorded in execution.triage either way.

• The diff leaves the machine (truncated to 64 KiB, https only). That is why it is opt-in.

• Jev is early-access (launched 2026-09-15). The client follows TypeSafe's published request/response shape and is tested against a local server speaking it — not against the live API from this repository.

🎯 Why

Agents write fluent, plausible code, and naive pipelines that collapse infrastructure errors into "pass" approve patches whose tests are broken, never ran, or were rewritten to agree with the bug. Switching models does not fix that; deterministic verification does. AdversaryGate puts no LLM in the verifier: the same harness judges every patch, whichever model wrote it, and when it did not measure something it says so instead of showing a green check.

📚 Read more

📄 License

Copyright © 2026 Sanflow (Sanflow10).

Releases from 3.0.0 on are distributed under the GNU Affero General Public License v3.0 (AGPL-3.0-only), with the additional terms that section 7 of that license allows — see NOTICE. The 2.x line, up to and including 2.14.2, was published under the MIT License, and copies obtained under it keep that license. Only the latest release is distributed: the tags, GitHub Releases and PyPI files of earlier versions are no longer published.

For a commercial license without the AGPL obligations, write to sanflow086@gmail.com.