Slate v2 Mobile Example Proof Fix

Goal

Make the document-state and multi-root-document mobile example proofs pass without weakening the architecture claim.

Current Evidence

• document-state mobile rows fail because raw click() into inputs and wrapped editor text places the caret in mobile-specific positions.
• multi-root-document mobile rows fail because raw clicks can hit mobile chrome/status controls instead of the intended root, and clipboard API permissions differ from desktop Chromium.
• The existing Slate browser harness already exposes semantic focus, selection, text insertion, and paste helpers. Use those for deterministic mobile proof.

Decisions

• Keep real browser coverage.
• Do not call a semantic-handle row native mobile text transport.
• Prefer root/editor handles for deterministic model selection and root-local paste behavior.
• Keep raw pointer rows only where the claim is specifically pointer activation.
• Fix library/runtime code only if deterministic proof still exposes a runtime bug after test transport is honest.

Plan

1. Add local Playwright helpers for append-to-input and deterministic Slate selection/text insertion.
2. Convert mobile-unstable raw clicks in document-state to explicit editor selections.
3. Convert mobile-unstable multi-root root activation rows to stable root chrome or semantic root handles.
4. Use the existing clipboard helper for root-local paste instead of privileged navigator.clipboard.writeText in mobile.
5. Rerun focused mobile specs against fresh static output.

Verification

• bun build:next
• PORT=3123 bun serve:playwright
• PLAYWRIGHT_BASE_URL=http://localhost:3123 PLAYWRIGHT_RETRIES=0 bun run playwright playwright/integration/examples/document-state.test.ts playwright/integration/examples/multi-root-document.test.ts --project=mobile --workers=1
• Focused Chromium rerun for the same specs if mobile passes.

Result

• document-state mobile rows use deterministic editor selection for editor mutations and explicit input caret placement for title edits.
• multi-root-document keeps native pointer proof isolated, while root-editing rows use SlateBrowserEditorHarness.rootAt(...) for deterministic mobile semantic transport without reaching into browser-handle internals.
• Mobile gets clipboard permission parity with Chromium; the root-local paste row uses handle-backed clipboard ingress to avoid claiming native mobile clipboard transport.

Verified:

• bun build:next
• PLAYWRIGHT_BASE_URL=http://localhost:3123 PLAYWRIGHT_RETRIES=0 bun run playwright playwright/integration/examples/document-state.test.ts playwright/integration/examples/multi-root-document.test.ts --project=mobile --workers=1
• PLAYWRIGHT_BASE_URL=http://localhost:3123 PLAYWRIGHT_RETRIES=0 bun run playwright playwright/integration/examples/document-state.test.ts playwright/integration/examples/multi-root-document.test.ts --project=chromium --workers=1
• bun lint:fix
• bun --filter slate-browser build
• bun --filter slate-browser typecheck
• bun typecheck:root
• docs/solutions/test-failures/2026-05-23-slate-v2-mobile-example-proofs-must-separate-native-pointer-from-semantic-editing.md captures the reusable mobile proof rule.