Slate Browser Next System Move

Specialist testing/proof doc. For current queue and roadmap truth, see master-roadmap.md.

Purpose

This doc answers one question: what is the highest-leverage targeted move for slate-browser if this work reopens after the first public package tranche?

This is conditional follow-on guidance, not the current default queue for the Slate v2 program.

Current State

slate-browser already has the first tranche it needed:

• real workspace package under /Users/zbeyens/git/slate-v2/packages/slate-browser
• public split:
  • slate-browser
  • slate-browser/core
  • slate-browser/browser
  • slate-browser/playwright
• live root commands:
  • yarn test:slate-browser
  • yarn test:slate-browser:core
  • yarn test:slate-browser:dom
  • yarn test:slate-browser:selection
  • yarn test:slate-browser:e2e
  • yarn test:slate-browser:e2e:local
  • yarn test:slate-browser:ime
  • yarn test:slate-browser:ime:local
  • yarn test:slate-browser:anchors
• public Playwright surface already includes:
  • getter namespace
  • selection namespace
  • exact-vs-contains HTML assertions
  • clipboard assertion helpers
  • exclusive clipboard serialization
  • real clipboard write plus real paste gesture

So the next move is not:

• another package split
• a fake fixture API
• a fake generic driver abstraction

The real pressure from slate-v2 is narrower:

• renderer/input policy
• zero-width policy
• IME-sensitive empty-state behavior

Decision Criteria

The next move should:

1. directly help prove the remaining slate-v2 browser-facing seam
2. improve test honesty, not abstraction count
3. make later cross-browser and perf lanes easier
4. avoid fake lane-neutral API design before a second backend exists

Direction Read

1. Stronger openExample(...) Readiness Contract

This is the strongest move.

Why:

• every remaining browser-facing proof starts by mounting an example
• the current openExample(...) surface is useful, but still thin
• readiness is still described as a handful of waits, not as a real contract

What it should do:

• keep openExample(...) as the only routing entrypoint
• make readiness explicit and intentional
• distinguish:
  • page navigation
  • editor root visibility
  • example-specific mounted state
  • selection-sensitive readiness

What it should not become:

• a Lexical-sized kitchen sink initializer
• a generic runner abstraction
• a new public openFixture(...)

Strong take:

• steal Lexical’s setup discipline
• do not copy Lexical’s whole initialize(...) blob

2. Cross-Browser Lane

This is important. It is not first.

Why it loses right now:

• the docs already reject fake cross-browser IME abstraction theater
• Chromium is still the honest first lane for IME and clipboard-heavy example proof
• a cross-browser lane without a sharper readiness contract just gives you wider flakes

Best posture:

• add test:slate-browser:cross after the readiness contract lands
• start with non-IME proof:
  • placeholder visibility
  • semantic selection normalization
  • plain clipboard behavior

Do not start with:

• Safari/WebKit IME heroics

3. Perf / Accuracy Lane

This should happen. It should happen after the next correctness seam is pinned.

Why:

• Premirror and Pretext are the right influence for lane naming and benchmark honesty
• but performance lanes are worth a lot more once correctness targets stop moving

Best later shape:

• test:slate-browser:perf
• maybe test:slate-browser:accuracy

Strong take:

• no perf lane before the renderer/input policy gauntlet exists

4. Less Playwright-Specific Public Boundary

This is the wrong move today.

Why:

• there is one real public backend today: slate-browser/playwright
• building a generic EditorDriver now would be abstraction cosplay
• the package already has the right split:
  • lane-neutral nouns in core and browser
  • backend-specific harness in playwright

Rule:

• keep the API nouns editor-shaped
• keep the backend surface explicit until a second backend is real

5. Release Posture

This matters least right now.

Why:

• package shape is already real
• package promise should still stay conservative
• release strategy does not unlock the next slate-v2 seam

Best posture:

• keep the package experimental/private until one more real proof lane lands on top of the public API

Recommendation

The strongest next system-level move is:

1. make openExample(...) a real readiness contract
2. use that contract to build the first renderer/input-policy gauntlet

That gauntlet should target the live unresolved seam:

• empty block placeholder policy
• zero-width rendering policy
• selection normalization around sentinel text
• IME commit behavior on empty and zero-width-sensitive starts

Concrete Tranche

Do this next:

1. tighten OpenExampleOptions around readiness semantics instead of ad hoc waits
2. add readiness-sensitive browser regressions for zero-width / empty-state / IME-adjacent behavior
3. only after that, branch outward into:
   • test:slate-browser:cross
   • test:slate-browser:perf
   • maybe test:slate-browser:accuracy

Anti-Rules

Do not do these first:

• reintroduce openFixture(...)
• add fake public synthetic paste helpers
• invent a lane-neutral driver abstraction
• start with cross-browser IME theater
• turn release semantics into the main architectural decision

Bottom Line

The public package tranche is done.

The next move is not “more surface area”.

It is:

• a sharper readiness contract at openExample(...)
• then a renderer/input-policy proof gauntlet for the remaining slate-v2 seam

That is the cleanest path to honest cross-browser, perf, and release decisions later.