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fastly-compute-well-known-spa-fallback

fastly-compute-well-known-spa-fallback is a skill for Claude Code, Codex from divinevideo/divine-mobile. It costs 151 tokens per session (2,404 once invoked), scanned A, original, MPL-2.0.

A Fastly Compute guide for serving verification files as JSON instead of the HTML page used by a single-page app fallback. These files help Apple and Google verify links from mobile apps.

In plain words
What is it for?
Use it to protect /.well-known/apple-app-site-association and assetlinks.json, check their content type, and ensure the published files bypass the SPA fallback.
Why use it?
The fallback can return index.html with a successful status for missing paths, causing Universal Links or App Links verification to receive HTML instead of JSON.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Claude Code; installed under .agents/ (shared by several agents).

not rated 265repo today A scan SkillSpector: pass 151 tokens original MPL-2.0

Good fit Use it to protect /.well-known/apple-app-site-association and assetlinks.json, check their content type, and ensure the published files bypass the SPA fallback.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback
View source ↗ divinevideo/divine-mobile
Install

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.

Any agent
npx skills add divinevideo/divine-mobile --skill fastly-compute-well-known-spa-fallback
Clone the repo
git clone --depth 1 https://github.com/divinevideo/divine-mobile

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for fastly-compute-well-known-spa-fallback

README.md
[![agentmods](https://agentmods.dev/badge/skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback/github.svg)](https://agentmods.dev/skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback)
Your own site
<a href="https://agentmods.dev/skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback"><img src="https://agentmods.dev/badge/skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback/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.

agentmods 80×15 button for fastly-compute-well-known-spa-fallback

Your own site · 80×15
<a href="https://agentmods.dev/skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback"><img src="https://agentmods.dev/badge/skills/divinevideo/divine-mobile/fastly-compute-well-known-spa-fallback.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 151 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,404 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00151 $0.02404
Opus 5 $0.00076 $0.01202
Sonnet 5 $0.00030 $0.00481
Haiku 4.5 $0.00015 $0.00240

Measured 11d ago against content hash 2c93c6bfbb80, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

fastly-compute-well-known-spa-fallback scanned grade A with 1 finding 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 11d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- `curl -I https://yourdomain.com/.well-known/apple-app-site-association` shows `Content-Type: text/html`
.agents/skills/fastly-compute-well-known-spa-fallback/SKILL.md · 229 lines

How it starts

The opening of the file, as written. The whole thing — 229 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fastly Compute: .well-known Files Intercepted by SPA Fallback

Problem

When using @fastly/compute-js-static-publish with SPA fallback configured (spaFile: "/index.html"), the PublisherServer.serveRequest() returns index.html with status 200 and Content-Type text/html for ANY path not found in the KV store. This includes /.well-known/apple-app-site-association and /.well-known/assetlinks.json, which iOS and Android require to be served as application/json.

Symptoms:

  • iOS Universal Links don't work (Apple's verification fetches .well-known/apple-app-site-association and gets HTML)
  • Android App Links don't work (Google's verifier fetches .well-known/assetlinks.json and gets HTML)
  • curl -I https://yourdomain.com/.well-known/apple-app-site-association shows Content-Type: text/html
  • The files ARE published to KV (confirmed by npm run fastly:publish) but still return HTML

Non-Obvious Root Causes

  1. SPA fallback returns 200, not 404: The publisher's SPA mode returns index.html with HTTP 200 for missing paths. You cannot distinguish "file served" from "fallback served" by status code alone - you must inspect the Content-Type.

  2. apple-app-site-association has no file extension: The static publisher infers MIME type from file extension. With no extension, it cannot detect application/json, so even when the file IS published to KV, it may get application/octet-stream or be served incorrectly.

  3. includeWellKnown: true in publish-content.config.js is necessary but not sufficient: It ensures the files are uploaded to KV, but doesn't prevent the SPA fallback from intercepting the requests, and doesn't fix the content-type for extension-less files.

  4. Both apex domain and subdomain handlers need the fix: If your Compute handler has separate code paths for subdomains vs apex, both paths must intercept .well-known/ requests before reaching the SPA fallback.

Solution

Step 1: Ensure Files Are Published

Read the full file on GitHub · 229 lines

Changes

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.

  1. 11d ago First seen · 229 lines · 151 tokens per session scan A 2c93c6bfbb80

Subscribe to this mod's changes

fastly-compute-well-known-spa-fallback is a skill published in the GitHub repository divinevideo/divine-mobile (265 stars, last pushed today), licensed MPL-2.0. It adds 151 tokens to every session and 2,404 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

CloudDevOps and cloudMobile
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