Deadlatch

The pre-trade latch for your trading agent. Advisory-only.

Three things you need to know before anything else:

1. You need an independent, cross-broker gate that you control. If an agent can place orders on your account, the last check between the agent and the broker should not be the agent itself — and it should not be locked to one broker's UI or rules.
2. Deadlatch does not predict, does not recommend, and does not place orders. It answers one question only: is this order allowed right now? It is not a signal generator and it is not a broker.
3. Every answer comes with reasons, evidence, and a local audit record on Linux/macOS. PASS / WARN / BLOCK is never a bare verdict — you can see which rule hit, why, and what was evaluated. Durable audit writes (init / append / repair / prune / shadow report) are supported on Linux and macOS only. On Windows the package still imports, and the rule engine / Guard / CLI / MCP still compute decisions; those write paths fail closed with audit_platform_unsupported. Offline verify / read of a stopped snapshot remain available. Windows MCP is a limited integration path, not a full trusted audit chain.

Honest boundary (please read): Deadlatch is advisory. It cannot force an agent that never calls it to call it, and it cannot stop an agent that ignores a BLOCK from submitting the order somewhere else. Whether the agent calls the guard and honors the result is the integrator's decision. Do not rely on this tool as a guarantee against loss — it is a gate, not an insurance policy.

• License: MIT — see LICENSE.
• 中文文档: README.zh-CN.md
• Security: SECURITY.md · Contributing: CONTRIBUTING.md · Disclaimer: DISCLAIMER.md

Start here

The current install path is the verified PyPI deadlatch==0.1.2, published on 2026-09-22. The stable GitHub v0.1.2 Release targets b072e8a4d4b053e1d5a428dbb9c47e06652fbf4c; its wheel/sdist assets match the PyPI originals.

pip install deadlatch==0.1.2

The published MCP Registry name is io.github.Diabloluo/deadlatch at version 0.1.2, verified active/latest on 2026-09-22. The local server.json matches that published version. The command below starts the verified PyPI package directly.

MCP-first start:

uvx --from deadlatch==0.1.2 deadlatch-mcp --policy policy.yaml --portfolio portfolio.json

--policy and --portfolio are required local files. --audit-path and --kill-switch-path are optional. Use fictional or your own simulated inputs only. Deadlatch is advisory-only: it never places orders and cannot stop an agent that never calls it. Option orders must use the broker's unique full contract code as symbol. A historical GitHub pre-release remains at v0.1.0.dev1; it is not the current install path.

Then:

1. Run a fictional-data Quick Start below (Python, CLI, or MCP) on Linux or macOS. Confirm PASS → BLOCK → local audit. Windows can import the package and run rule computation; it is not the audit-write Quick Start.
2. Request a 20-minute integration assessment only if you already have an order-intent or simulated execution path: open the assessment form.

That GitHub issue is public. Do not paste accounts, positions, orders, API keys, tokens, customer names, or private paths. Security defects must go through GitHub Security Advisories, not a public issue.

Quick Start (60 seconds each)

All three quick starts use fictional data and a temporary audit path. They are executed from the same source scripts by the test suite, so they cannot drift from the documentation. Full audit-write / MCP Quick Start requires Linux or macOS. Windows may import the library and evaluate rules; it will not initialize or append a durable audit collection.

1. Python API

pip install dist/deadlatch-*.whl        # or: pip install -e .
python docs/quickstart/python.py

Shows Guard.from_policy(...) → Order / Portfolio → guard.check(...): a valid order returns PASS / 0; an oversized order returns BLOCK / 3 with the hit rules; on BLOCK the example caller stops — no broker call is ever made.

2. CLI

bash docs/quickstart/cli.sh                  # requires `deadlatch` on PATH

Creates fresh inputs in a temp directory (dynamic timestamps — never goes stale), then runs deadlatch check for PASS (exit 0), BLOCK (exit 3), an input error (exit 4), and a --json check, plus shadow report --json over the audit.

3. MCP (stdio)

python docs/quickstart/mcp_client.py         # requires `deadlatch` installed

Starts deadlatch-mcp as a real subprocess over stdio, lists the five tools, and calls check_order once for PASS and once for BLOCK. policy / portfolio / audit paths are server startup configuration — an agent cannot swap them as tool arguments. BLOCK is a constraint the caller must honor; technically the guard cannot force a fully bypassing agent to call it.

What it is / is not

Who should use it

• Teams that already have an order-intent or simulated execution path and want an independent, deterministic pre-trade gate with a local audit trail.
• Developers who want a small, dependency-light, fail-closed building block they can integrate into their own execution pipeline.
• Anyone who wants to evaluate orders against a policy they control, expressed as plain YAML.

Who should not use it: anyone expecting a profit guarantee, a backtest engine, a portfolio manager, or a tool that enforces itself. If the agent never calls the guard, or ignores a BLOCK, nothing in this repository can stop it.

Core security boundary

• Local: everything runs on your machine; no account credentials are ever stored, read, or transmitted.
• No network core path: the library, CLI, and MCP server never open a socket, never register an HTTP/SSE route, and never call out for quotes or anything else (the MCP SDK's HTTP stack is a transitive dependency that business code never imports).
• Never places orders: the core package (library, CLI, MCP server) has no broker connectivity and never submits orders. Experimental read-only mapping examples exist only in the development workspace; they are not included in the public candidate or the wheel, and they are not live-verified integrations.
• Fail-closed: missing or malformed data → BLOCK (exit 3); input/config errors → exit 4; internal errors → exit 5. An uncertain state is never reported as PASS.
• Direction is snapshot-derived: order-side text is never accepted as proof of a close. Stock and option closing intent is recognized only when a fresh portfolio snapshot contains a matching, opposite-side position with sufficient quantity. For options, symbol must be the broker's unique full contract code; never reuse an underlying ticker across different expiries, strikes, or rights.
• USD-only (v0.1): any currency mismatch (order, portfolio, positions) is an input error (exit 4); the MCP account-status tool fail-closes on mismatch.

Write surface: the tool never modifies policy, portfolio, or kill-switch state, never connects to a broker, and never places an order. Two kinds of intentional local file writes exist:

1. Audit subsystem: Guard.check() / check_order append one sanitized v2 record to a UTC day shard next to the logical audit path (30-day retention). Append is a bounded tail write under a shared lock; it does not rewrite history. A new collection needs one explicit deadlatch audit init (or initialize_audit_state) before append; Guard/MCP never auto-migrate. deadlatch shadow report and deadlatch audit prune delete whole shard files that fall outside the 30-calendar-day window. deadlatch audit repair --quarantine still uses lock/tmp files and os.replace when it isolates a truncated tail. Ordinary append is not crash-atomic across files. POSIX locks are cross-process. v0.1.2 durable audit writes are Linux/macOS only; Windows writers receive audit_platform_unsupported and do not skip directory fsync to report success.
2. Explicit migration output: deadlatch migrate --output <file> writes the migrated document only when you explicitly pass --output.

The public contract for these rules, Decimal thresholds, exit codes, and option-symbol requirements is docs/rules-spec.md.

The 12 rules (v0.1)