# TV and runtime compatibility

This document lists which JavaScript APIs the input engine relies on, the first
browser version that supports each one, and the TV runtime versions that ship
those browsers. Every table below is dated **fetched 2026-09-18**, and every
version number carries the URL it was read from.

standarnav is on npm since 2026-09-22 (`0.1.0`). Nothing in this document
implies the package has been tested on a physical TV or device; see
`../adr/0013-browser-baseline-and-fallbacks.md` for the baseline decision and
its status.

## API support

Sources: caniuse.com / MDN Browser Compatibility Data, fetched 2026-09-18. The
paths in the "Used at" column are paths in this repository.

| API | Chrome | Safari | Firefox | Used at | Behaviour if absent |
|---|---|---|---|---|---|
| `WeakRef` | 84 | 14.1 | 79 | `src/spatial/spatial.ts:127-141` (`elementHandle`) | No failure: `elementHandle` reads `globalThis.WeakRef` and, when it is absent, returns a strong reference that drops itself on the first read finding the element detached (`element.isConnected`) — the fallback recorded in `../adr/0013-browser-baseline-and-fallbacks.md`. |
| `Element.checkVisibility()` | 105 | 17.4 | 106 | `src/tabbable.ts:47-51` (`isHidden`) | Fallback already present: `offsetParent === null && getClientRects().length === 0`. Degrades cleanly; this fallback does not detect `visibility: hidden`. |
| `[inert]` attribute effect | 102 | 15.5 | 112 | `src/tabbable.ts:54-56` (`isInert`) | `closest("[inert]")` works everywhere as an attribute check; only the browser's native inert *behaviour* (blocking focus/pointer/AOM automatically) is missing. Degrades cleanly. |
| `Array.prototype.at` | 92 | 15.4 | 90 | Nowhere: `src/tabbable.ts:104-107` (`getTabbableEdges`) uses index arithmetic instead | Nothing to degrade, because the call is not made. `.at()` is avoided deliberately — see `../adr/0013-browser-baseline-and-fallbacks.md`. The `lib: ["es2020", "dom", "dom.iterable"]` of `tsconfig.json` keeps it that way: a call to `.at()` is a type error here as well as a runtime risk. First Samsung Internet version: 16.0. |
| ES2020 syntax (optional chaining `?.`, nullish coalescing `??`) | 80 | 13.1 | 74 | Whole build output. The `es2020` TypeScript target is declared at `tsconfig.json` and decided in `../adr/0013-browser-baseline-and-fallbacks.md` | Below this floor the whole bundle fails to parse (`SyntaxError`) before any fallback logic runs. The floor is the higher of the two operators: `?.` is Chrome 80 / Safari 13.1 / Firefox 74, `??` is Chrome 80 / Safari 13.1 / Firefox 72. First Samsung Internet version for both: 13.0. |

Sources: https://caniuse.com/mdn-javascript_builtins_weakref ·
https://caniuse.com/mdn-api_element_checkvisibility ·
https://caniuse.com/mdn-html_global_attributes_inert ·
https://caniuse.com/mdn-javascript_builtins_array_at ·
https://caniuse.com/mdn-javascript_operators_optional_chaining ·
https://caniuse.com/mdn-javascript_operators_nullish_coalescing

The same version numbers appear in
`../adr/0013-browser-baseline-and-fallbacks.md`.

## TV runtime versions

Sources: Samsung Developers, "Web Engine Specifications"
(https://developer.samsung.com/smarttv/develop/specifications/web-engine-specifications.html)
and LG webOS TV, "Web API and Web Engine"
(https://webostv.developer.lge.com/develop/specifications/web-api-and-web-engine),
both fetched 2026-09-18.

| TV year | Tizen version | Tizen Chromium | webOS version | webOS Chromium |
|---|---|---|---|---|
| 2018 | 4.0 | 56 | 4.x | 53 |
| 2019 | 5.0 | 63 | 4.x | 53 |
| 2020 | 5.5 | 69 | 5.x | 68 |
| 2021 | 6.0 | 76 | 6.x | 79 |
| 2022 | 6.5 | 85 | 22 | 87 |
| 2023 | 7.0 | 94 | 23 | 94 |
| 2024 | 8.0 | 108 | 24 | 108 |
| 2025 | 9.0 | 120 | 25 | 120 |

### Unverified runtimes

| Runtime | Status | What was searched |
|---|---|---|
| Hisense VIDAA | Not measured yet | No public Chromium version number found for any VIDAA generation as of 2026-09-18. |
| Vizio SmartCast | Not measured yet | No public Chromium version number found for any SmartCast generation as of 2026-09-18. |
| Steam Deck (Steam client CEF) | Documented once, then stale | The Steam Deck beta client of 2024-01-18 shipped embedded Chromium (CEF) 109.0.5414.120 (https://steamdeckhq.com/news/steam-deck-beta-client-1-18-24-descriptions/). No newer version number has been disclosed as of 2026-09-18: Valve confirmed a November 2025 rebuild of the client browser (Alloy runtime to Chrome runtime) without naming a Chromium version (https://steamcommunity.com/groups/SteamClientBeta/discussions/3/688615792191756981/). Treat any build after 2024-01-18 as not measured yet. |

## What this means for the engine

Each bullet below restates the "behaviour if absent" column above as a design
consequence. The resulting compatibility tiers of
`../adr/0013-browser-baseline-and-fallbacks.md` are named in the next section.

- **`WeakRef` absent**: no consequence, because the fallback is built. Among
  the APIs above, `WeakRef` has the lowest support threshold (Chromium 84 /
  Safari 14.1 / Firefox 79), but it still sits four versions above the Chromium
  80 syntax floor of the `es2020` target, so leaving it unguarded would raise
  the effective floor from 80 to 84 — not by failing to construct: the plugin
  would mount, render and accept focus, then throw a `ReferenceError` the first
  time the user pressed a direction, because the construction sits in
  `elementHandle`, reached from `remember` and not from `setup`
  (`../adr/0013-browser-baseline-and-fallbacks.md`, the `WeakRef` row). The
  fallback of `elementHandle` (strong reference
  plus an `isConnected` check, `src/spatial/spatial.ts:127-141`) removes
  `WeakRef` as a constraint, which is what lets the syntax target become the
  single floor.
- **`checkVisibility()` absent**: no functional risk. The existing fallback in
  `tabbable.ts` is a strict subset of what `checkVisibility()` detects
  (it misses `visibility: hidden`), so visibility-filtering degrades in
  precision, not correctness of the happy path.
- **`inert` attribute effect absent**: no functional risk for this engine's
  own logic, because it reads the attribute directly (`closest("[inert]")`)
  rather than relying on the browser's native inert behaviour. Pages that
  depend on the *native* inert effect (rather than this engine's read of the
  attribute) for anything else keep whatever native support their runtime
  has.
- **`Array.prototype.at` absent**: no functional risk, because nothing calls
  it. `getTabbableEdges` reaches the last element by index
  (`src/tabbable.ts:104-107`), and the `es2020` `lib` makes a future `.at()` a
  type error rather than a runtime surprise on a 2021 television.
- **Below the ES2020 syntax floor**: the entire bundle fails to parse. There
  is no fallback for a syntax floor; the only levers are the build target
  itself and, if ever built, a separate legacy build.

### Resulting tiers (see `../adr/0013-browser-baseline-and-fallbacks.md`)

- **Supported and tested tier**: Chromium ≥ 85 (TV 2022 and newer: Tizen 6.5,
  webOS 22), Safari ≥ 15, Firefox ≥ 79. The ADR states that this tier is a
  claim about engines, not about devices.
- **Best-effort tier**: TV 2020-2021 (Tizen 5.5/6.0 = Chromium 69/76, webOS
  5.x/6.x = Chromium 68/79). Every runtime in this tier is below Chromium 80,
  so the ES2020 output is expected to fail at load on all four of them.
  Reaching them needs a separate legacy build with a lower target. Whether
  that build is a v1 goal is a roadmap decision, not a v0 promise — see the
  ADR for the proposed decision date.
- **Unknown**: Hisense VIDAA, Vizio SmartCast, and Steam Deck beyond the
  Chromium 109 snapshot documented for the beta client of 2024-01-18.

No claim in this document implies that any of these tiers has been verified
against physical hardware. Device testing is a roadmap item.