Narrow terminal crash: rendered powerline line exceeds terminal width

[davidmoshal]

Summary

pi-powerline can render a footer/status line wider than the terminal, causing pi's TUI to crash with an uncaught render-width exception in narrow terminals.

Error

pi exiting due to uncaughtException:
Error: Rendered line 10422 exceeds terminal width (45 > 31).

This is likely caused by a custom TUI component not truncating its output.
Use visibleWidth() to measure and truncateToWidth() to truncate lines.

Debug log written to: /Users/davem/.pi/agent/pi-crash.log
    at TUI.doRender (.../@earendil-works/pi-tui/dist/tui.js:1252:23)

A later crash log from a 27-column terminal showed the offending line:

Terminal width: 27
Line 2815 visible width: 45

[2815] (w=45)  ─── ◈ pi / dm ──────────────────────────────
[2816] (w=27)  ─ Kimi K2.7 Code / pi ─────

The over-wide line appears to be the powerline breadcrumb/status segment containing project/branch info (pi / dm) plus a fixed-width separator.

Expected behavior

All rendered lines should fit within the width passed to the component renderer. On narrow terminals, the statusline should truncate or drop segments rather than emitting a line wider than the terminal.

Actual behavior

A rendered footer line exceeded terminal width, and pi exited due to the TUI invariant violation.

Environment

• Package: pi-powerline 0.8.0
• pi: 0.79.10
• Terminal width in crash log: 27 columns
• Model/session at time: Fireworks Kimi, branch dm

Suggested fix

Ensure every rendered line uses pi-tui width helpers before returning:

• visibleWidth() to measure rendered ANSI strings
• truncateToWidth() or equivalent segment-dropping logic before return

For powerline-style bars, a robust approach is:

1. reserve prompt/editor width first;
2. render segments in priority order;
3. drop low-priority segments as width shrinks;
4. truncate the final segment/separator to the exact remaining width;
5. assert every returned line is <= width in tests, including widths under 30 columns.

[davidmoshal]

Additional review found a more precise likely source and workaround.

Corrections/clarifications:

1. The offending line appears to be the editor top border from PromptPrefixEditor in editor.ts, not the footer. It is emitted when breadcrumb is set to "inner". The footer/token-stats line appears to be separate and may already truncate.
2. The dm segment in the crash log is likely the basename of the current working directory, not the git branch. getBreadcrumbData in breadcrumb.ts uses basename(ctx.cwd), so the breadcrumb is project folder / current folder info.
3. The exact ◈ glyph in the crash log is uncertain. pi-powerline appears to use Nerd Font icons or fallbacks; the diamond may be a misrendered Nerd Font icon or from another theme/extension.
4. Workaround until fixed: use /powerline breadcrumb:top or /powerline breadcrumb:hide to avoid breadcrumb:inner mode.
5. More specific suspected root cause: in editor.ts, the replacement string like border + ' ' + info + ' ' + dashes can exceed width when the breadcrumb info is not truncated aggressively enough, or when ANSI reset sequences in renderBreadcrumbInfo cause visible-width miscalculation.

Suggested fix addition:

• Add a final guard before returning rendered editor lines, e.g. result[0] = truncateToWidth(result[0], width).
• Add tests asserting every returned line is <= width, especially for widths under 10, 20, and 30 columns, with breadcrumb:inner enabled.

[jwu]

Thanks for the detailed report and crash log. This has been fixed and published in pi-powerline@0.8.1.

What changed:

• The custom editor now caps its effective render width using the current tui.terminal.columns when available, so resize/narrow-terminal cases cannot keep rendering against a wider stale width.
• Every editor-rendered line is now passed through a final truncateToWidth(..., renderWidth, '') guard before returning to pi TUI.
• Added a regression test for the narrow-terminal case: rendering with a wider requested width while the terminal is only 27 columns must never emit lines wider than 27.

This addresses the immediate crash invariant by ensuring the editor/breadcrumb line does not exceed the terminal width.

Your suggested priority-based segment layout is a good direction for a more graceful visual behavior. The current patch is intentionally minimal and defensive; I will consider a follow-up design that renders powerline segments by priority, drops lower-priority segments as space shrinks, and truncates the final separator/segment to the exact remaining width.

[jwu]

Adding the concrete fix reference:

• Fix commit: 12c8ced (fix(editor): prevent over-wide lines in narrow terminals)
• Release commit: ff4bb6a (chore(release): 0.8.1 [skip ci])
• Published version: pi-powerline@0.8.1

The fix is included in the v0.8.1 release.