gate.cat 0.4.8

Block irreversible AI-agent actions before they run — deterministic, fail-closed action-veto (deny-list + exec-check + human-in-the-loop) for any tool-using agent, from a Claude Code hook to local LLMs.

gate.cat

Install: pip install gate-cat — then a veto in two lines:

from gatecat import check_action                     # deny-list gate
check_action("agent", "terraform destroy -auto-approve")  # -> raises ActionVetoed

The distribution is gate.cat (PyPI normalizes it, so pip install gate-cat); the import module is gatecat. 0.2.x used import cacheback — see MIGRATION.md. Honest line, up front: the gate is certain only about what it blocks. An action it does not match is unchecked, not safe.

Scope — persistent environments. gate.cat guards places where a mistake is irreversible: a dev laptop with real data, a deploy pipeline, prod, paid infra. In a throwaway CI/sandbox container (a fresh git checkout that gets discarded) nothing is irreversible, so the gate disarms itself and logs a disarmed no-op rather than crying wolf. It auto-detects CI markers; GATECAT_VETO_EPHEMERAL=0 forces it armed anyway. Measured on 14.7k real Claude Code commands and a public HF corpus of 8.6k SWE-agent commands, it intervenes on ~0.6% of commands on both — the deny-list found something structural, not tuned to one user.

Stop your AI agent before it takes an irreversible action. The action-veto is deterministic and model-agnostic — a deny-list + exec-check + human-in-the-loop that inspects the tool call at the boundary, so it protects any agent the same way: a Claude Code hook (frontier), a crewAI/LangGraph app, or a local 7-30B model on Ollama/vLLM. TruthPipeline adds an honest verdict (confirmed / refuted / uncertain / unchecked) using deterministic checks (exec/calc/lookup) plus a sample-spread uncertainty signal; veto.py consumes that verdict to block, pause, or ask a human before a tool call executes. (That uncertainty signal — a secondary feature — is where the 7-30B local-model strength lives; see "Why small/cheap models" below. The veto itself needs no such assumption.)

One mechanism, not two products: the verification engine (TruthPipeline) and the action-gate that consumes it (before_action / VetoGate) ship together — same package, same brand. Semantic cache and Cache-Augmented Synthesis (below) are the supporting engine underneath both.

An AI agent decides to run a README's install one-liner. The gate stops it before a single byte executes — a real terminal, pip install gate-cat, no montage:

_{Blocks the curl … | sh pattern specifically; obfuscated/base64 install tricks still evade — see OBJECTIONS.md. Cast: docs/demos/demo_a.cast.}

Install

pip install gate-cat                  # core
pip install "gate-cat[openai]"      # + OpenAI wrapper
pip install "gate-cat[anthropic]"   # + Anthropic wrapper
pip install "gate-cat[proxy]"       # + proxy server (FastAPI)
pip install "gate-cat[all]"         # everything

Quote the extras ("gate-cat[openai]") — zsh treats bare [...] as a glob.

The hook — the strongest mode

Enforcement in the harness, outside the model's control flow: the tool call cannot execute until the gate returns. pip install gate-cat puts the gatecat-hook console script on your PATH; register it as a Claude Code PreToolUse hook by adding this to .claude/settings.json (nothing to edit — it's called by name, no absolute paths):

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Bash|Write|Edit",
        "hooks": [{ "type": "command", "command": "gatecat-hook" }]
      }
    ]
  }
}

Now ask your agent to run rm -rf ~/project: the call is blocked (exit 2) and the model sees VETO [DELETE_ANALYZER]: deletes '/home/you/project' under protected root '/home' - requires a human. A delete under a throwaway path like /tmp/x is deliberately allowed — the gate stops deletes that touch a persistent location, and doesn't nag on scratch dirs. Run gate.cat any time to see what it's watched and stopped. Fail-closed: a missing or erroring engine blocks rather than allowing. In a throwaway CI/sandbox it disarms itself and logs a no-op (GATECAT_VETO_EPHEMERAL=0 forces it armed).

Framework adapters (crewAI / LangGraph / AutoGen) exist too, but they are in-process convention — a prompt injection can route around them. Only the hook is enforcement the agent cannot skip. See examples/veto_integrations/ for adapter usage.

Truth Pipeline (koryto → gate → veto)

One entry point that composes the SDK's verification blocks into a truth + compliance pipeline for ANY model (a 3B SLM on a phone and a frontier LLM use the same sample_fn callback).

from gatecat import TruthPipeline, ActionPolicy, ActionVetoed

pipe = TruthPipeline(
    sample_fn=my_llm,                              # callback(prompt) -> str
    fact_base={"capital of france": "Paris"},      # lookup channel (optional)
    policy=ActionPolicy(deny=[r"terraform.*prod"], max_amount=100.0),
)

r = pipe.evaluate("Evaluate: 6 / 2 * 3", answer="1")
r.verdict   # "refuted" — caught confident-wrong, deterministically, $0
r.truth     # "9" — the correct value, so the caller can self-correct

@pipe.guard()                                      # compliance on ACTIONS
def deploy(target): ...
deploy(target="terraform apply prod")              # raises ActionVetoed BEFORE executing

pipe.compliance_report()                           # audit trail: verdicts + vetoes

A policy in action: dev runs, destroy prod is denied, apply staging escalates to a human — one deterministic gate, three outcomes:

_{Source: examples/veto_terraform.py. Cast: docs/demos/demo_b.cast.}

Honest verdicts — the pipeline never claims more than it measured:

Verdict	Meaning	reliable	trusted
confirmed	answer matches a verified atom (exec/calc/lookup)	✅	✅
refuted	answer contradicts a verified atom	❌	❌
uncertain	soft disagreement without arbiter, or high sample spread	❌	❌
unchecked	outside verification reach — not "true", just "couldn't check"	❌	✅

For critical systems filter on report.reliable (confirmed only), not trusted.

Gate catches HESITATION, not LYING. When the model is confidently wrong (same N probes, same wrong answer — zero spread), that's invisible to disagreement. The gate is an uncertainty signal → pause/escalate, NOT a correctness guarantee.

Verdict precedence (conflicts are resolved by construction):

1. exec/calc (hard, physically independent of the model) always win — the gate isn't even asked.
2. lookup disagreement goes to the optional arbiter_fn; without one → uncertain (set lookup_hard_block=True only if your fact base is fresh at query time).
3. gate (sample-spread) runs only when no verified atom exists.
4. veto is an orthogonal axis: it judges actions, is fail-closed, and guard() without a policy raises instead of silently allowing everything.

Methods: evaluate(q, answer) verifies an existing answer · ask(q) generates with sample_fn then verifies · guard() decorates a tool function with pre-execution veto · check_action(repr) evaluates an action without running it.

arbiter_fn contract: (question, answer, KorytoVerdict) -> Optional[bool] — True = the fact base is right (refute stands), False = the model was right (stale base, answer confirmed), None/exception = no ruling → uncertain. Every stage that spoke is recorded in report.stages for debugging.

Why small/cheap models (this is about the uncertainty signal, not the veto — the veto is model-agnostic): agents increasingly run on cheap/local models (7-30B via Ollama/vLLM) for cost and data-residency. That's where the gate's uncertainty signal is strongest (AUC 0.77–0.90, measured N=4800) and where frontier-first guardrail vendors don't aim — on frontier models the signal weakens (AUC 0.68–0.71). The action-veto's deny-list + exec-check does not depend on model size at all; it protects a Claude Code (frontier) agent exactly as it protects a local one.

Naming note: koryto (Polish: riverbed) is the project's canonical term for the deterministic verification layer — the probabilistic "river" (model output) is held by a deterministic "riverbed" (exec/calc/lookup). It is a deliberate brand term, not an accident of translation.

The deal

Sixty seconds of your time, in exchange for:

• a deterministic gate your agent cannot run terraform destroy, rm -rf, DROP TABLE or gh repo delete through — 28 default policies for the irreversible-action class, fail-closed, ~0.6% intervention rate measured on real traffic (it won't nag you);
• a ready-to-paste Claude Code PreToolUse hook — the strongest mode: enforcement in the harness, outside the model's control flow;
• adapters for crewAI / LangGraph / AutoGen (honestly labeled: in-process convention, weaker than the hook);
• one-line uninstall if it's not for you. Worst case, you lost a minute.

What we ask back — this project runs on one currency:

• 🐛 a veto story — tell us what got caught, or what slipped through. Misses are worth more than praise: reported gaps get fixed and credited in the CHANGELOG, and the bypass suite grows from exactly these reports. …and if the gate ever blocks something dumb before it happened, a ⭐ helps other people find this.

Pricing (announced — checkout opens when the hosted layer ships)

The local gate is free forever — including local reports. The paid layer, gate.cat Cloud, is the off-machine copy of your veto history — the one an agent with shell access can't delete or rewrite (a local log is inside its blast radius). Announced prices: Solo $9/mo · Team $199/mo flat (up to 10 devs) · audit-readiness pilots by invoice. We deliberately don't take money until fulfillment is zero-touch; the founding list locks the price: PRICING.md.

Verify the numbers

Every public number traces to a row in FACTS.md (claim → source → allowed wording), and the corpus harnesses behind the headline measurements are in scripts/ — reproduce them, and if your numbers disagree with ours, that's a bug report we want. The 14.7k-command half of the ~0.6% claim is our own private log (labeled as such in FACTS.md); the public corpus half you can re-run yourself.

Recall — the claim we care about most (does anything dangerous get through?) is measured on two axes in RECALL.md. The deterministic one needs no datasets and runs in seconds:

git clone https://github.com/BGMLAI/gate.cat && cd gate.cat
pip install -e .                       # the veto engine (zero-dependency core)
python scripts/recall_danger_axis.py   # 43/43 known danger classes through the FULL gate, 0 false-blocks

(The harness lives in scripts/ — not shipped inside the pip wheel — so verify it from a clone, where you can also read the danger catalog it checks against.)

Cache / Cache-Augmented Synthesis (supporting engine)

The verification/veto layer above runs on top of a semantic cache. Used standalone, the cache also works as a drop-in wrapper for OpenAI/Anthropic SDKs with a three-tier response: verbatim cache, synthesis, upstream — cache semantically similar queries and return instant responses (<10ms), or synthesize from cached knowledge (~300ms, ~$0.002) instead of a full upstream call.

Quick Start

OpenAI (drop-in, zero code change)

from gatecat import CachedOpenAI

client = CachedOpenAI(api_key="sk-...")

# First call: ~500ms (API + cache populate)
response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "What is the capital of France?"}],
)

# Second call with similar query: ~5ms (cache hit)
response2 = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "capital of France?"}],
)
print(response2.gatecat_hit)  # True

Anthropic

from gatecat import CachedAnthropic

client = CachedAnthropic(api_key="sk-ant-...")
message = client.messages.create(
    model="claude-sonnet-4-20250514",
    max_tokens=1024,
    messages=[{"role": "user", "content": "What is Python?"}],
)
print(message.gatecat_hit)  # True on cache hit

Streaming

Streaming works transparently. Cache misses buffer and store the response; cache hits replay as a synthetic stream.

stream = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Explain quantum computing"}],
    stream=True,
)
for chunk in stream:
    print(chunk.choices[0].delta.content or "", end="")

Cache-Augmented Synthesis (CAS)

When a query is similar to cached entries but not an exact match, CAS synthesizes a fresh response from cached knowledge using a cheap LLM — instead of calling the expensive upstream API.

from gatecat import CachedOpenAI

client = CachedOpenAI(
    synthesis_mode="auto",  # enable three-tier response
    # Uses Gemini Flash Lite via OpenRouter by default (~$0.002/synthesis)
    # Or point to local llama-cpp: synthesis_model="local/phi-4-mini"
)

response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Explain photosynthesis"}],
)

if response.gatecat_hit:
    print("Verbatim cache hit (<10ms, $0.00)")
elif response.gatecat_synthesized:
    print("Synthesized from cache (~300ms, ~$0.002)")
else:
    print("Upstream API call (~500ms, ~$0.03)")

Three-tier response:

  Query  -->  Embed  -->  HNSW search
                |
    sim >= 0.92 |  VERBATIM HIT   -->  Return cached response     <10ms   $0.00
    sim >= 0.80 |  SYNTHESIS       -->  Top-K cached Q&A + LLM    ~300ms  ~$0.002
    sim <  0.80 |  UPSTREAM MISS   -->  Call API, cache response   ~500ms  ~$0.03

Validated with 100-question benchmark across 5 domains: 0.892 mean quality ratio vs direct API responses.

Proxy Mode — veto any local agent, zero code (Ollama / NIM / OpenRouter / vLLM)

Ollama, NIM, OpenRouter, vLLM and LM Studio all speak the OpenAI API, so one proxy in front of them protects them all — your agent changes one base_url, writes no code. When the model asks to run a tool, the proxy checks the proposed call against the 21 deny policies and blocks the dangerous ones before the agent executes them (rm -rf, terraform destroy, DROP TABLE, disk wipes, repo deletion, ...).

pip install "gate-cat[proxy]"

# point the proxy at your provider (local Ollama shown; NIM/OpenRouter/vLLM the same)
export OPENAI_BASE_URL="http://localhost:11434/v1"    # your real provider
export GATECAT_ALLOW_INSECURE_UPSTREAM=1              # only for a local http provider
gatecat-proxy                                         # listens on :8080

Then your agent points at the proxy instead of the provider — that's the whole change:

client = OpenAI(base_url="http://localhost:8080/v1")  # was 11434; now guarded

A dangerous tool call comes back as a refusal, not an execution. Modes: GATECAT_PROXY_TOOL_VETO=block (default) / flag (annotate only) / off. Caveat: this gates tool calls the model makes through the API; an agent that shells out directly still needs the harness hook (gatecat-hook).

---

Run gate.cat as a standalone proxy server. No SDK integration needed — just change base_url:

# Docker (recommended)
docker run -e OPENAI_API_KEY=sk-... -p 8080:8080 gatecat/proxy

# Or pip
pip install "gate-cat[proxy]"
gatecat-proxy  # starts on :8080

Then point your existing code at the proxy:

from openai import OpenAI

client = OpenAI(base_url="http://localhost:8080/v1")  # that's it
response = client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "What is Python?"}],
)
# Cache headers: X-Gatecat-Hit, X-Gatecat-Synthesized

Works with any OpenAI-compatible client (curl, LangChain, LiteLLM, etc). Configure via environment variables:

Variable	Default	Description
OPENAI_API_KEY	—	API key for upstream provider
GATECAT_SIMILARITY_THRESHOLD	0.92	Cache hit threshold
GATECAT_SYNTHESIS_MODE	off	off / auto / always
GATECAT_TTL	86400	Cache TTL in seconds
GATECAT_PORT	8080	Server port

Async

from gatecat import AsyncCachedOpenAI, AsyncCachedAnthropic

async_client = AsyncCachedOpenAI()
response = await async_client.chat.completions.create(
    model="gpt-4o",
    messages=[{"role": "user", "content": "Hello"}],
)

Standalone Cache

Use SemanticCache directly for any embedding-based caching:

from gatecat import SemanticCache

cache = SemanticCache(
    similarity_threshold=0.92,
    cache_ttl=86400,  # 24 hours
)

cache.populate("What is Python?", "Python is a programming language...")
result = cache.lookup("Tell me about Python")  # cache hit

Negative Cache (blocklist)

Block known-bad query patterns before they hit the API:

# Block a query pattern
client.cache.negative.add(
    "What is the airspeed of an unladen swallow?",
    reason="hallucination",
)

# Similar queries are now blocked
client.cache.negative.check("airspeed of swallows")  # returns match info

# Manage the blocklist
client.cache.negative.list(limit=50)
client.cache.negative.remove(entry_id=42)
client.cache.negative.report_false_positive(entry_id=42)

Configuration

client = CachedOpenAI(
    # Cache settings
    cache_dir="~/.gatecat",        # where to store cache data
    similarity_threshold=0.92,        # cosine similarity for cache hit (0-1)
    negative_threshold=0.85,          # threshold for negative cache
    cache_ttl=86400,                  # TTL in seconds (24h default)
    cache_max_entries=100_000,        # max entries before LRU eviction
    cache_enabled=True,               # set False to disable
    on_negative_hit="raise",          # "raise" | "skip" | callable

    # Synthesis settings (CAS)
    synthesis_mode="off",             # "off" | "auto" | "always"
    synthesis_model="google/gemini-2.0-flash-lite-001",  # any OpenAI-compatible model
    synthesis_model_base_url=None,    # auto-detected from OPENROUTER_API_KEY
    synthesis_model_api_key=None,     # auto-detected from env
    synthesis_threshold=0.80,         # min similarity for synthesis candidates
    synthesis_top_k=5,                # number of cached Q&A pairs for synthesis

    # OpenAI settings (passthrough)
    api_key="sk-...",
)

How It Works

Query --> Embed (MiniLM-L6, 384-dim) --> Search HNSW index
  |-- VERBATIM HIT  (sim >= 0.92) --> Return cached response (<10ms)
  |-- SYNTHESIS      (sim >= 0.80) --> Top-K cached Q&A + cheap LLM (~300ms)
  '-- MISS           (sim <  0.80) --> Call upstream API, cache response (~500ms)

• Embedder: ONNX MiniLM-L6-v2 (90MB, runs locally, no API calls)
• Index: hnswlib HNSW for fast approximate nearest neighbor search
• Store: SQLite with WAL mode for concurrent access
• Fallback: numpy brute-force if hnswlib is unavailable

CLI

gatecat-cli stats          # Show cache statistics
gatecat-cli entries        # List cached entries
gatecat-cli evict          # Remove expired entries
gatecat-cli clear          # Clear all entries
gatecat-cli lookup "query" # Test a cache lookup

Custom Embedders

Register your own embedder for any modality:

from gatecat.embedders import BaseEmbedder, register_embedder
import numpy as np

class MyEmbedder(BaseEmbedder):
    dim = 256
    modality = "custom"

    def encode(self, input_data) -> np.ndarray:
        # Your embedding logic here
        ...

register_embedder("my-embedder", MyEmbedder)
cache = SemanticCache(embedder="my-embedder")

Built-in embedders: minilm (text), clip (image, coming soon), clap (voice, coming soon).

Comparison

Feature	gate.cat	GPTCache	LiteLLM	Redis LangCache
Semantic similarity	Yes	Yes	Exact only	Yes
Cache-Augmented Synthesis	Yes	No	No	No
OpenAI drop-in	Yes	Partial	Yes	No
Anthropic drop-in	Yes	No	Yes	No
Streaming support	Yes	No	No	No
Negative cache	Yes	No	No	No
Multimodal (planned)	Yes	No	No	No
Async	Yes	No	Yes	No
Zero config	Yes	No	No	No
Proxy mode (Docker)	Yes	No	Yes	No
Local (no server)	Yes	Yes	No	No
License	Apache 2.0	MIT	MIT	Redis

License

Apache 2.0 — see LICENSE.

Built by BGML.ai / Fundacja BLOOM.