Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/hookdeck/webhook-skills/supabase-webhooksnpx skills add hookdeck/webhook-skills --skill supabase-webhooksgit clone --depth 1 https://github.com/hookdeck/webhook-skillsWrote 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/hookdeck/webhook-skills/supabase-webhooks)<a href="https://agentmods.dev/skills/hookdeck/webhook-skills/supabase-webhooks"><img src="https://agentmods.dev/badge/skills/hookdeck/webhook-skills/supabase-webhooks.svg" alt="Measured on agentmods" 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 | $0.00101 | $0.03088 |
| Opus 5 | $0.00051 | $0.01544 |
| Sonnet 5 | $0.00020 | $0.00618 |
| Haiku 4.5 | $0.00010 | $0.00309 |
Grade A, and why
supabase-webhooks 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 yesterday.
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.
This is a copy
73% identical to adyen-webhooks — 261 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 236 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Supabase Webhooks
When to Use This Skill
- How do I receive Supabase Database Webhooks (INSERT / UPDATE / DELETE)?
- How do I verify a Supabase Auth Hook signature?
- Why is my Supabase
webhook-signatureverification failing? - How do I secure a Supabase Database Webhook when there is no signature?
- How do I implement a
send_email/send_sms/custom_access_tokenAuth Hook? - What does the
v1,whsec_secret prefix mean?
Two Surfaces, Two Security Models
Supabase sends outbound HTTP from two different systems. They do not share a security model — do not apply one's verification to the other.
| Database Webhooks | Auth Hooks (HTTP Hook) | |
|---|---|---|
| Source | Postgres trigger → pg_net |
Supabase Auth (GoTrue) |
| Docs | Database Webhooks | Auth Hooks |
| Events | INSERT, UPDATE, DELETE |
6 auth lifecycle hooks |
| Signature | None — no HMAC, no signing secret, no Supabase header | Standard Webhooks HMAC-SHA256 |
| Auth | Whatever headers you configure (e.g. Authorization: Bearer …) |
webhook-id / webhook-timestamp / webhook-signature |
| Semantics | Fire-and-forget, async | Request/response — your JSON body changes auth behaviour |
| Retries | None documented | Up to 3 retries (2s backoff, 5s total budget) — requires a non-empty retry-after header |
Supabase documents no source-IP allowlist and no user-agent value for
either surface. Do not build either into your receiver.
Verification (core)
Auth Hooks — Standard Webhooks HMAC-SHA256
const { Webhook } = require('standardwebhooks');
// Secret is issued as "v1,whsec_<base64>". Strip the "v1,whsec_" prefix; the
// remainder is STANDARD base64 that the library base64-DECODES to the raw HMAC
// key. Using the base64 string itself as the key rejects every real delivery.
const wh = new Webhook(process.env.SUPABASE_AUTH_HOOK_SECRET.replace('v1,whsec_', ''));
// Signs `{webhook-id}.{webhook-timestamp}.{raw_body}` and base64-compares in
// constant time against every space-delimited `v1,<sig>` entry, with a
// ±5-minute timestamp tolerance. Pass the RAW body — re-serialised JSON fails.
const payload = wh.verify(rawBody, {
'webhook-id': headers['webhook-id'],
'webhook-timestamp': headers['webhook-timestamp'],
'webhook-signature': headers['webhook-signature'],
}); // throws WebhookVerificationError on failure
What ships with it
20 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- examples/express/.env.example 745 B
- examples/express/package.json 474 B
- examples/express/README.md 3.7 KB
- examples/express/src/index.js 9.8 KB runs code
- examples/express/test/webhook.test.js 12 KB runs code
- examples/fastapi/.env.example 697 B
- examples/fastapi/main.py 9.7 KB runs code
- examples/fastapi/README.md 4.3 KB
- examples/fastapi/requirements.txt 106 B
- examples/fastapi/test_webhook.py 13 KB runs code
- examples/nextjs/.env.example 697 B
- examples/nextjs/app/webhooks/supabase/auth-hook/route.ts 6.3 KB runs code
- examples/nextjs/app/webhooks/supabase/route.ts 4.1 KB runs code
- examples/nextjs/package.json 553 B
- examples/nextjs/README.md 3.4 KB
- examples/nextjs/test/webhook.test.ts 13 KB runs code
- examples/nextjs/vitest.config.ts 162 B runs code
- references/overview.md 8.0 KB
- references/setup.md 9.0 KB
- references/verification.md 12 KB
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.
- yesterday First seen · 236 lines · 101 tokens per session scan A d6c2ea1255c1
supabase-webhooks is a skill published in the GitHub repository hookdeck/webhook-skills (84 stars, last pushed yesterday), licensed MIT. It adds 101 tokens to every session and 3,088 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 73% identical to adyen-webhooks, differing in 261 lines, and is treated as a copy.
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