@kyntra/claude-hook

Real-time AI agent governance for Claude Code. Enforce your coding principles via hooks — block destructive commands, catch false "complete" reports, and get warned on soft violations before they land.

$ claude
> fix the bug and push

[KYNTRA] BLOCKED — Force push to main/master branch is blocked
         Principle: rule-no-force-push-main
         Layer: rules

This is the open-source client adapter. It communicates with Kyntra's server-side governance engine (patent-pending) over HTTPS.

Why

You told Claude "follow my rules." You pasted a reminder into every session. You still got curl OK — site is live when the site was broken.

The problem isn't the model — reminders are advisory. Hooks are enforcement. Kyntra sits in front of every AI tool call and returns allow / block / warn in under a second.

• Determinism first — a built-in regex rule engine catches the obvious classes (rm -rf /, git push --force main, git commit --no-verify, echo >> .env, "done without grep verification"). No LLM calls, no cost, no latency.
• LLM for the ambiguous rest — Kyntra's Layer 2 (Haiku) handles contextual judgements your regex can't express.
• Pro: Layer 3 Sonnet deep review — when Haiku flags a case as warn/block/uncertain, Pro subscribers get a second opinion from Sonnet using the full constitution + trust profile + custom rules. Article 0 supremacy is enforced in code, not in prompt.
• Self-evolving principles — repeat violations bubble up; reliable principles decay. Kyntra's trust-adjustment engine is patent-pending (KR claims 1 & 2).
• Auto-update notice — when a newer release is available, the bridge prints a one-per-day reminder to stderr (deduped in ~/.cache/kyntra/). Hook behavior is never affected by the notice path.

Install

npx @kyntra/claude-hook install

That registers the hook in ~/.claude/settings.json, backs up any existing config, and gives you a copy-paste next-step. Then:

export KYNTRA_API_KEY=ky_live_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

…and restart Claude Code. Try git push --force origin main — it should be refused at the hook layer, before Claude even shells out.

Get an API key

You need a Kyntra subscription. Plans start at $15/month with a 50% first-month discount and a 14-day money-back guarantee.

• Pricing — Starter $15/mo, Pro $29/mo
• Terms · Privacy · Refund

Environment

How it works

Claude Code session
  │
  │ 1. Tool call (Bash / Edit / Write / Stop)
  ▼
Hook: node bridge.js   ← this package (MIT, ~200 lines)
  │
  │ 2. POST /api/governance/check  {event, tool, command, ...}
  ▼
api.kyntra.ai.kr       ← server engine (closed-source, patent-pending)
  │
  │ 3. Layer 0 KV cache → Layer 1 rules → Layer 2 Haiku → verdict
  ▼
Hook: exit 0 (allow) | exit 2 (block)

The client adapter holds zero principle logic. It does three things: read stdin, POST to the Kyntra API, exit with the verdict. That's the entire source.

Fail-open

If api.kyntra.ai.kr is unreachable or times out (5 s default), the hook exits 0 (allow) with a note on stderr. Kyntra will never block legitimate work because of its own bugs or network issues.

CLI

npx @kyntra/claude-hook install        # install hooks into ~/.claude/settings.json
npx @kyntra/claude-hook uninstall      # remove them
npx @kyntra/claude-hook print-config   # print the hook snippet for manual setup
npx @kyntra/claude-hook --help

Manual setup

If you prefer to edit ~/.claude/settings.json yourself:

npx @kyntra/claude-hook print-config

…and merge the output into your existing hooks key.

Personal reminder block (optional)

Drop a short reminder file at ~/.claude/kyntra-userctx.txt (any text, up to 4KB). On every user prompt, the bridge prepends this file's contents to its additionalContext so Claude sees your personal checklist before it starts each turn:

⚠️ Principle check:
  - NO-DEFER — finish every request this session, don't push to "next session"
  - Verify on production (browser + console errors), not just curl
  - (whatever else your team needs)

This replaces the "just echo a static JSON via a separate UserPromptSubmit hook" pattern. Consolidating into a single hook avoids Claude Code's multi-hook additionalContext merging ambiguity — in practice only one entry surfaces, so a competing echo hook silently strips the governance feedback block (next section).

Next-turn feedback loop

When the bridge sees a UserPromptSubmit event, it also reads the last 5 minutes of verdict history from ~/.cache/kyntra/verdicts.jsonl and appends any warn / block entries:

[KYNTRA feedback] 지난 5분 내 Kyntra 경고 1건: 19:18:30Z
  warn:rule-request-fidelity-violation (L:rules)
  — 이번 턴 시작 전 동일 패턴 반복 여부 자각하고 응답을 설계할 것.

Before this, Stop-hook warns lived only in stderr — Claude Code never surfaced them to the model, so the agent happily repeated the same deferral the rule had just flagged. The bridge-level injection closes that gap on the next user turn without any Claude Code change required.

What Kyntra actually sees

For every tool call the hook sends:

• event_type — pre_tool_use / post_tool_use / stop / …
• tool — Bash / Edit / Write / …
• command — first 800 chars of the command string (Bash only)
• file_path — the path of the file being edited
• response_text — for Stop events, first 1,500 chars of the assistant's last message

That's it. Source code contents, repository listings, secrets, or environment variables are never sent. Full details in the Privacy Policy.

License

MIT — see LICENSE.

The MIT license covers this client adapter only. The server-side governance engine at api.kyntra.ai.kr is proprietary to Flowlabs and protected under Korean patent application (claims 1 and 2 cover the compliance verification engine and trust-adjustment engine respectively).

Contact

• Homepage: https://kyntra.ai.kr
• App: https://app.kyntra.ai.kr
• Issues: https://github.com/YBPartners/kyntra-claude-hook/issues
• Email: contact@kyntra.ai.kr

Built by Flowlabs. Made because I was tired of Claude telling me the deploy was "done" when it wasn't.