Prompt notice lines skip the region background

• Status: Todo
• Kind: Bug
• Authors: jp
• Date: 2026-09-22
• Label: package=jp_cli
• Label: package=jp_printer
• Label: type=bug

Printer::prompt_println and Printer::prompt_eprintln build a PrintTask and send it straight to the worker. Neither goes through Canvas, so neither carries the background set_prompt_background last named, and a notice printed inside a reasoning block cuts an unshaded row through it.

This is the hole T-0fg8cjs described for the prompt itself, in the two helpers that print a line beside a prompt rather than through its writer.

Reachable today

report_editor_failure (crates/jp_cli/src/editor.rs:103) writes through prompt_eprintln, and is reached from inside a shaded region two ways:

• ToolPrompter::inline_edit (prompter.rs:394), when Ctrl+X fails during an e or r prompt on a tool called from a shaded reasoning block.
• InterruptHandler (handler.rs:455, :462, :504, and the bare prompt_eprintln at :463), on the interrupt reply path. Now that the renderer publishes the region while reasoning streams, an interrupt taken during reasoning is shaded, so these land inside a region too.

prompt_println's callers are the plugin install flow (dispatch.rs:1986, :2052, install.rs:54), which is not on the query path. It has the same gap and no way to reach it today.

Severity

Contained and visible: one row renders on the terminal default in the middle of a shaded block, and the block resumes after it. Nothing leaks, since the line never opens a background to leave open.

Shape of a fix

The shading lives in Canvas, which decorates a fmt::Write. These two build a task instead, so there is no writer to wrap. Either run the content through a throwaway Canvas over a String before sending it, or move the assertion down into the worker for PrintOrigin::Prompt tasks, which would cover both helpers and anything added beside them later.

Watch for

prompt_eprintln targets Err while the prompt writer targets Tty. They are separate file descriptors onto the same terminal, so a background opened by one is not closed by the other: whatever asserts it has to close it inside the same task.

The notice starts with \n so it lands on a fresh row below the prompt. The fill belongs on that new row, not on the one the widget left mid-line.

a_prompt_notice_on_the_chrome_stream_is_not_held (printer_tests.rs:1099) asserts the exact unshaded output, so it has to move with the fix.