fix(tui): typing characters not visible until Enter pressed #11249

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opened 2026-05-20 13:26:32 +00:00 by hamza.khyari · 0 comments

hamza.khyari commented

2026-05-20 13:26:32 +00:00

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Commit Message: fix(tui): subclass Input to override _watch_value and eliminate layout=True per keystroke
Branch: bugfix/m8-tui-input-live-refresh

Background and Context

Textual's WriterThread only flushes stdout when its write queue is empty (if qsize() == 0: flush()). Every keystroke triggers Input._watch_value which sets self.virtual_size = Size(self.content_width, 1) — a Reactive(layout=True) attribute. This generates ANSI escape sequences that keep the write queue permanently non-empty during typing, so stdout is never flushed and typed characters are never rendered on screen.

When Enter is pressed, conversation.update() generates a large burst of output which eventually drains the queue, causing stdout to flush and everything to appear at once.

Root cause: Input._watch_value in Textual's built-in Input widget sets self.virtual_size on every single keystroke. virtual_size is defined as Reactive(layout=True), which calls refresh(layout=True) on every change — generating ANSI output that keeps the WriterThread write queue non-empty.

Two of the three layout=True sources per keystroke have already been eliminated:

✅ _apply_symbol now skips Static.update() when the symbol is unchanged
✅ CSS height: auto → height: 1 on #prompt > Input removes the auto_dimensions guard

One source remains: self.virtual_size = Size(self.content_width, 1) in Textual's own Input._watch_value.

Current Behaviour

User types characters into the TUI prompt → nothing visible on screen → press Enter → all typed characters and the LLM response appear simultaneously.

Expected Behaviour

Each typed character appears immediately on screen as it is entered, in real-time.

Acceptance Criteria

Characters typed in the TUI prompt appear on screen immediately as they are typed
The _watch_value override does not break cursor positioning, character insertion, or deletion
The Input.Changed event still fires correctly so mode detection (❯ / / / $ / ☰) works
All existing TUI BDD and integration tests continue to pass

Supporting Information

Fix: subclass textual.widgets.Input in src/cleveragents/tui/widgets/prompt.py, override _watch_value to skip self.virtual_size = Size(...) while preserving the rest of the method body (_suggestion, Changed event, _initial_value, cursor position).

Since the prompt widget is short and single-line, horizontal scrolling (which virtual_size enables) is not needed.

Relevant files:

src/cleveragents/tui/widgets/prompt.py — _TextualPromptInput, _watch_value override
src/cleveragents/tui/cleveragents.tcss — already fixed height: 1

Subtasks

Create _PromptInput subclass of textual.widgets.Input in prompt.py that overrides _watch_value to skip virtual_size update
Preserve _suggestion, Changed event, _initial_value, cursor position logic in overridden method
Update _TextualPromptInput to use _PromptInput instead of raw _InputBase
Verify characters appear live in TUI when running agents tui
Tests (Behave): add scenario asserting that _watch_value does not set virtual_size
Run nox (all sessions), fix any errors

Definition of Done

This issue is complete when:

All subtasks above are completed and checked off.
A Git commit is created where the first line matches the Commit Message in Metadata exactly.
The commit is pushed to the branch matching the Branch in Metadata exactly.
The commit is submitted as a PR to master, reviewed, and merged.

## Metadata - **Commit Message**: `fix(tui): subclass Input to override _watch_value and eliminate layout=True per keystroke` - **Branch**: `bugfix/m8-tui-input-live-refresh` ## Background and Context Textual's `WriterThread` only flushes stdout when its write queue is empty (`if qsize() == 0: flush()`). Every keystroke triggers `Input._watch_value` which sets `self.virtual_size = Size(self.content_width, 1)` — a `Reactive(layout=True)` attribute. This generates ANSI escape sequences that keep the write queue permanently non-empty during typing, so stdout is never flushed and typed characters are never rendered on screen. When Enter is pressed, `conversation.update()` generates a large burst of output which eventually drains the queue, causing stdout to flush and everything to appear at once. **Root cause**: `Input._watch_value` in Textual's built-in `Input` widget sets `self.virtual_size` on every single keystroke. `virtual_size` is defined as `Reactive(layout=True)`, which calls `refresh(layout=True)` on every change — generating ANSI output that keeps the `WriterThread` write queue non-empty. Two of the three `layout=True` sources per keystroke have already been eliminated: - ✅ `_apply_symbol` now skips `Static.update()` when the symbol is unchanged - ✅ CSS `height: auto → height: 1` on `#prompt > Input` removes the `auto_dimensions` guard One source remains: `self.virtual_size = Size(self.content_width, 1)` in Textual's own `Input._watch_value`. ## Current Behaviour User types characters into the TUI prompt → nothing visible on screen → press Enter → all typed characters and the LLM response appear simultaneously. ## Expected Behaviour Each typed character appears immediately on screen as it is entered, in real-time. ## Acceptance Criteria - Characters typed in the TUI prompt appear on screen immediately as they are typed - The `_watch_value` override does not break cursor positioning, character insertion, or deletion - The `Input.Changed` event still fires correctly so mode detection (`❯` / `/` / `$` / `☰`) works - All existing TUI BDD and integration tests continue to pass ## Supporting Information Fix: subclass `textual.widgets.Input` in `src/cleveragents/tui/widgets/prompt.py`, override `_watch_value` to skip `self.virtual_size = Size(...)` while preserving the rest of the method body (`_suggestion`, `Changed` event, `_initial_value`, cursor position). Since the prompt widget is short and single-line, horizontal scrolling (which `virtual_size` enables) is not needed. Relevant files: - `src/cleveragents/tui/widgets/prompt.py` — `_TextualPromptInput`, `_watch_value` override - `src/cleveragents/tui/cleveragents.tcss` — already fixed `height: 1` ## Subtasks - [ ] Create `_PromptInput` subclass of `textual.widgets.Input` in `prompt.py` that overrides `_watch_value` to skip `virtual_size` update - [ ] Preserve `_suggestion`, `Changed` event, `_initial_value`, cursor position logic in overridden method - [ ] Update `_TextualPromptInput` to use `_PromptInput` instead of raw `_InputBase` - [ ] Verify characters appear live in TUI when running `agents tui` - [ ] Tests (Behave): add scenario asserting that `_watch_value` does not set `virtual_size` - [ ] Run `nox` (all sessions), fix any errors ## Definition of Done This issue is complete when: - All subtasks above are completed and checked off. - A Git commit is created where the first line matches the Commit Message in Metadata exactly. - The commit is pushed to the branch matching the Branch in Metadata exactly. - The commit is submitted as a PR to master, reviewed, and merged.

hamza.khyari added this to the v3.7.0 milestone

2026-05-20 13:26:32 +00:00

hamza.khyari added the

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