External action redirect -> back button -> incorrect `navigation.state`

[aaronadamsCA]

Reproduction

https://stackblitz.com/edit/github-nucwwnaj?file=app%2Froutes%2Fhome.tsx

1. Submit a form whose action redirects to a third party (e.g. Shopify checkout).
2. Press the back button to return to the page with the form.

System Info

System:
    OS: Linux 6.8 Ubuntu 24.04.3 LTS 24.04.3 LTS (Noble Numbat)
    CPU: (4) x64 AMD EPYC 7763 64-Core Processor
    Memory: 10.39 GB / 15.62 GB
    Container: Yes
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.13.0 - /home/ubuntu/.volta/tools/image/node/24.13.0/bin/node
    Yarn: 4.12.0 - /home/ubuntu/.volta/tools/image/yarn/4.12.0/bin/yarn
    npm: 11.6.2 - /home/ubuntu/.volta/tools/image/node/24.13.0/bin/npm
    pnpm: 10.28.2 - /home/ubuntu/.volta/tools/image/pnpm/10.28.2/bin/pnpm
  npmPackages:
    @react-router/cloudflare: catalog: => 7.12.0 
    @react-router/dev: catalog: => 7.12.0 
    react-router: catalog: => 7.12.0 
    vite: catalog: => 8.0.0-beta.8

Used Package Manager

pnpm

Expected Behavior

navigation.state === "idle"

Actual Behavior

navigation.state === "submitting"

As a result, if you disable a "buy now" or "start checkout" button based on navigation.state to guard against submitting twice, then if the user returns to the page with the back button, the button stays disabled.

[timdorr]

Looks like this is due to the bfcache (back/forward cache): https://web.dev/articles/bfcache I'm not sure if we should add handling for the event (pageshow) or leave it up to the user. 🤷