Borrowing it
Nothing to install: this file belongs to nacre-work/nacre. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/nacre-work/nacre/main/.claude/skills/open-core-boundary/SKILL.mdgit clone --depth 1 https://github.com/nacre-work/nacreWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/nacre-work/nacre/open-core-boundary)<a href="https://agentmods.dev/skills/nacre-work/nacre/open-core-boundary"><img src="https://agentmods.dev/badge/skills/nacre-work/nacre/open-core-boundary/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/nacre-work/nacre/open-core-boundary"><img src="https://agentmods.dev/badge/skills/nacre-work/nacre/open-core-boundary.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00107 | $0.00773 |
| Opus 5 | $0.00053 | $0.00387 |
| Sonnet 5 | $0.00021 | $0.00155 |
| Haiku 4.5 | $0.00011 | $0.00077 |
Grade A, and why
open-core-boundary scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 8d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Where does this code go?
docs/licensing.md has the full split. The decision reduces to one question.
The question
Does a security team pay for it, or a developer?
If a single developer on a laptop needs it, it belongs here, in the Apache 2.0
core. If it exists because a regulated buyer's security or compliance function
requires it, it belongs in nacre-enterprise.
Blurring the line devalues both halves: the core stops being usable on its own, and the commercial half stops being worth buying.
Core, Apache 2.0
Data model · ingest · chunking · embeddings · hybrid search · reranking · the MCP server · the REST API · basic RBAC · a single organization · email and password authentication · Docker Compose.
Commercial, separate repository
Multi-tenancy and collection isolation · SSO (OIDC/SAML) and SCIM · document-level ACLs with deny rules · EMA and ID-JAG · the audit log, its export and SIEM forwarding · the global admin · quotas · closed-network delivery · HA Helm charts.
The mechanical rule
The core must not know the private repository exists. The boundary job in
CI fails the build if anything under packages/ or services/ references
@nacre.work/enterprise. The reverse direction is fine — over there,
@nacre.work/core is an ordinary dependency.
That job is the only automated part of this. Everything above it is judgement, which is why it is worth stating in the PR rather than assuming.
Extension points
Commercial modules plug into points declared by the core, in
packages/core/extensions.ts. The contract is docs/extensions.md.
registerAuthProvider(provider) // sso
registerAuthzResolver(resolver) // acl-advanced, tenancy
registerAuditSink(sink) // audit
mountAdminRoutes(...routes) // admin-global
Adding a fifth is a core change and belongs here. Its implementation may not. Design the point so the core is complete and correct with nothing plugged in — if the core only works once a commercial module registers, the boundary has already leaked, whatever the import graph says.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 8d ago First seen · 77 lines · 107 tokens per session scan A 79884d73aff7
open-core-boundary is a skill published in the GitHub repository nacre-work/nacre (0 stars, last pushed 10d ago), licensed Apache-2.0. It adds 107 tokens to every session and 773 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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