[ch-z-hc]

Bug

fill and select dispatch synthetic input events with bubbles: true but the default composed: false. For a control inside a shadow root, listeners on its host or document never receive those events. In particular, fill("") clears the DOM value and reports success without notifying document-level input listeners; there is no subsequent native text-insertion event to compensate.

Fix

Set composed: true on the existing input events in fill preparation, fill completion, and select completion. Leave change events and the rest of the interaction flow unchanged.

Reuse the existing real-Chrome harness for foreground/background shadow-input clearing and add a select regression that executes the actual CDP function against a connected shadow-root select. All three new regressions fail on the original product code and pass with the three-line fix.

Validation

• Default extension suite: 2583 passed, 235 conditionally skipped, including the two opt-in Chrome regressions. Those two were also run explicitly with Chrome and pass, alongside the select regression.
• Extension typecheck and production build, repository Biome (626 files), Stylelint, and DSH typecheck pass.
• DSH suite: 492 passed, 2 failed in existing runner kill-grace tests. Unchanged main reproduces the same two failures (28 passed in that file).
• Full opt-in fill/interaction run: 309 passed, 1 failed at an existing foreground document.hasFocus() setup assertion, before the affected fill operation. The new regressions pass. Unchanged main initially passed all 107 browser tests; a repeat has 106 passed, 1 failed at the same focus setup assertion. This establishes that main can also fail there, not the underlying cause or an entirely green opt-in suite.

No assertions/timeouts were relaxed and no new skip conditions were added. Rust and the other opt-in browser suites were not run. Implemented and tested with Codex assistance; no independent human review is claimed.