Borrowing it
Nothing to install: this file belongs to cardstack/boxel. 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/cardstack/boxel/main/.claude/skills/local-host-against-remote/SKILL.mdgit clone --depth 1 https://github.com/cardstack/boxelWrote 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/cardstack/boxel/local-host-against-remote)<a href="https://agentmods.dev/skills/cardstack/boxel/local-host-against-remote"><img src="https://agentmods.dev/badge/skills/cardstack/boxel/local-host-against-remote/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/cardstack/boxel/local-host-against-remote"><img src="https://agentmods.dev/badge/skills/cardstack/boxel/local-host-against-remote.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 | $0.00188 | $0.02290 |
| Opus 5.5 | $0.00075 | $0.00916 |
| Sonnet 5.5 | $0.00038 | $0.00458 |
| Haiku 4.5 | $0.00019 | $0.00229 |
Grade A, and why
local-host-against-remote 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 3d 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 — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.
A local host app against staging or production
A host app served from your own machine can talk to a deployed environment's realm server, Matrix server and secure origin, and sign in there as you would on the real app. The host is a static bundle whose environment URLs come from env vars at build time, so pointing it elsewhere is a matter of setting them before pnpm start.
Production caution: a local host against production uses real accounts and real data. Sign in with your own account, and never run tests, seed scripts or anything that writes in bulk against it.
Pointing the host at the environment
From packages/host, in a shell where BOXEL_ENVIRONMENT is not set. That variable puts the host in env mode, which ignores MATRIX_URL, ICONS_URL and SECURE_ORIGIN_URL in favor of a local Traefik stack's hostnames, and points every variable left unset at that stack.
Staging:
unset BOXEL_ENVIRONMENT ENV_MODE
export REALM_SERVER_DOMAIN=https://realms-staging.stack.cards/
export RESOLVED_BASE_REALM_URL=https://realms-staging.stack.cards/base/
export RESOLVED_CATALOG_REALM_URL=https://realms-staging.stack.cards/catalog/
export RESOLVED_SKILLS_REALM_URL=https://realms-staging.stack.cards/skills/
export RESOLVED_OPENROUTER_REALM_URL=https://realms-staging.stack.cards/openrouter/
export RESOLVED_PRETUI_REALM_URL=https://realms-staging.stack.cards/pretui/
export MATRIX_URL=https://matrix-staging.stack.cards
export MATRIX_SERVER_NAME=stack.cards
export PUBLISHED_REALM_BOXEL_SPACE_DOMAIN=staging.boxel.dev
export PUBLISHED_REALM_BOXEL_SITE_DOMAIN=staging.boxel.build
export ICONS_URL=https://boxel-icons.boxel.ai
export SECURE_ORIGIN_URL=https://secure.stack.cards/
pnpm start
Production:
unset BOXEL_ENVIRONMENT ENV_MODE
export REALM_SERVER_DOMAIN=https://app.boxel.ai/
export RESOLVED_BASE_REALM_URL=https://app.boxel.ai/base/
export RESOLVED_CATALOG_REALM_URL=https://app.boxel.ai/catalog/
export RESOLVED_SKILLS_REALM_URL=https://app.boxel.ai/skills/
export RESOLVED_OPENROUTER_REALM_URL=https://app.boxel.ai/openrouter/
export RESOLVED_PRETUI_REALM_URL=https://app.boxel.ai/pretui/
export MATRIX_URL=https://matrix.boxel.ai
export MATRIX_SERVER_NAME=boxel.ai
export PUBLISHED_REALM_BOXEL_SPACE_DOMAIN=boxel.space
export PUBLISHED_REALM_BOXEL_SITE_DOMAIN=boxel.site
export ICONS_URL=https://boxel-icons.boxel.ai
export SECURE_ORIGIN_URL=https://secure.boxel.ai/
pnpm start
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.
- 3d ago Changed 1c52ca2f4038
- 5d ago First seen · 90 lines · 188 tokens per session scan A 7a0b98b364a5
local-host-against-remote is a skill published in the GitHub repository cardstack/boxel (27 stars, last pushed today), licensed MIT. It adds 188 tokens to every session and 2,290 once invoked, about $0.0008 per session on Opus 5.5. 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 2026-10-21.
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