the picker was configured to not allow multiple picks, yet…

Error message

the picker was configured to not allow multiple picks, yet multiple picks were returned

What it means

`prompt_select` drives the interactive picker in single-select mode; it asserts that the picker returns at most one pick. If the picker backend returns multiple picks despite being configured for single selection, this bail fires, indicating a broken contract with the picker.

Solutions

Check the picker configuration: ensure multi-select is disabled end-to-end and the backend honors it
If a custom/test picker is in use, make it return at most one pick
Report a bug if the built-in picker emits multiple picks in single-select mode

Example fix

// custom picker before
Ok(vec![a, b])
// after
Ok(vec![a]) // single-select pickers must return at most one pick

Defensive patterns

Strategy: try-catch

Validate before calling

// when supplying a custom picker, assert its contract before use
assert!(picker.max_selections() <= 1, "prompt_select requires a single-select picker");

Type guard

fn single_pick(picks: &[Pick]) -> Option<&Pick> { picks.get(0).filter(|_| picks.len() == 1) }

Try / catch

let pick = match channel.prompt_select(prompt) {
    Ok(p) => p,
    Err(e) if e.to_string().contains("multiple picks") => return Err(anyhow!("picker misconfigured: single-select returned multiple picks")),
    Err(e) => return Err(e),
};

Prevention

Ensure the picker backend honors single-selection configuration
Keep picker wrappers and the underlying prompt library versions in sync
Cover single-select prompts with tests using a compliant mock picker

When it happens

Trigger: Calling `OutputChannel::prompt_select` (single-select helper) where the underlying picker returns a picks vector with more than one element — a picker-implementation or configuration bug, not a user-input error.

Common situations: Custom or mocked picker implementations returning multiple selections while `multiple` is disabled; version mismatches between the picker component and this wrapper.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of gitbutlerapp/gitbutler@58e5313667 (2026-09-18). Data as JSON: /api/errors/89644facf0de3fb6. Report an issue: GitHub.

Appendix: source

Thrown at crates/but/src/utils/output_channel.rs:514

        let Some(picks) = tui::run_picker(
            self,
            prompt.as_ref(),
            items,
            PickerOptions {
                allow_multiple: false,
                default_selected: Vec::new(),
                disabled: Vec::new(),
            },
        )?
        else {
            return Ok(None);
        };

        match &picks[..] {
            [] => Ok(None),
            [pick] => Ok(Some(pick)),
            _ => {
                anyhow::bail!(
                    "the picker was configured to not allow multiple picks, yet multiple picks were returned"
                )
            }
        }
    }

    pub fn prompt_multi_select<'a, Key, Value>(
        &mut self,
        prompt: impl AsRef<str>,
        items: &'a NonEmpty<(Key, Value)>,
    ) -> anyhow::Result<Option<Vec<&'a Value>>>
    where
        Key: std::fmt::Display,
    {
        tui::run_picker(
            self,
            prompt.as_ref(),
            items,

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