Bug reportAug 21, 2026· 0:28· 15 views
Monaco Editor v0.55.1: typing over a backward selection requires two keypresses on the textarea input path
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Bug report— by SceneRecap AI
mediumeditor/browser/controller/textAreaHandler
os: macOSbrowser: Chromiumviewport: 1280x720monaco_version: 0.55.1
Repro steps
- 1.Configure Monaco editor options with editContext set to false (textarea fallback mode) and load 'const U = 19.05;' into the editor.
- 2.Click the 'Run playground' button to load the configured Monaco instance into the Preview pane.
- 3.Click into the Monaco result editor to focus at the end of the line.
- 4.Press Shift+Left to create a backward text selection over the trailing semicolon.
- 5.Type a character (such as 'a') over the backward selection.
Expected
The selected character should immediately be replaced on the first keypress.
Actual
On the textarea input path (editContext: false), typing over a backward selection does not replace the text cleanly on the first keystroke, requiring extra input.
Evidence
visualMonaco editor instance created with 'editContext: false' in the preview pane at 7.0s.
visualBackward selection active across semicolon at line 1 in the result editor at 13.0s.
visualCharacter 'a' replaces ';' only after subsequent key handling at 19.0s.
Issue markdown (copy-paste ready)
### Summary When Monaco Editor is configured with `editContext: false` (fallback `textarea` input path), typing a character over a backward selection (created via `Shift+Left`) fails to process as expected on the first keypress. ### Steps to Reproduce 1. Set `editContext: false` in Monaco editor configuration (`t = 0.0s`). 2. Click the **Run playground** button to instantiate the editor (`t = 5.6s`). 3. Click into the result editor line (`t = 10.9s`). 4. Select backwards using `Shift+Left` (`t = 11.6s`). 5. Type a replacement character (`t = 17.0s`). ### Expected Result The backward-selected character should immediately be replaced by the typed character on the first keypress. ### Actual Result Typing over a backward selection on the textarea fallback path requires multiple keypresses or drops the initial keystroke. *Recorded with SceneRecap.*
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