zed-industries/zed · error

Cannot format prompt for {:?}

Error message

Cannot format prompt for {:?}

What it means

format_prompt_for_example matches on the requested PredictionProvider to pick a prompt formatter. Teacher/TeacherNonBatching, TeacherJumps/TeacherJumpsNonBatching, and Zeta2 have formatting paths; every other variant (the client-side inference providers) has no prompt format defined, so the `_` arm panics with the provider value. It is an explicit unsupported-provider assertion, not a runtime failure.

Source

Thrown at crates/edit_prediction_cli/src/format_prompt.rs:137

                        expected_cursor_offset,
                    )
                    .ok()
                });

            let rejected_output = example.spec.rejected_patch.as_ref().and_then(|patch| {
                format_expected_output(prompt_inputs, zeta_format, patch, None).ok()
            });

            example.prompt = prompt.map(|prompt| ExamplePrompt {
                input: prompt,
                expected_output,
                rejected_output,
                provider: args.provider,
                prefill: Some(prefill),
            });
        }
        _ => {
            panic!("Cannot format prompt for {:?}", args.provider);
        }
    };
    Ok(())
}

pub struct TeacherPrompt;

impl TeacherPrompt {
    pub(crate) const EDITABLE_REGION_START: &str = "<|editable_region_start|>\n";
    pub(crate) const EDITABLE_REGION_END: &str = "\n<|editable_region_end|>";
    pub(crate) const USER_CURSOR_MARKER: &str = "<|user_cursor|>";
    pub(crate) const NO_EDITS: &str = "NO_EDITS";

    /// Truncate edit history to this number of last lines
    const MAX_HISTORY_LINES: usize = 128;

    pub fn format_prompt(
        example: &Example,

View on GitHub (pinned to f4178619ac)

Solutions

1. Use a provider that supports formatting: teacher, teacher-non-batching, teacher-jumps, teacher-jumps-non-batching, or zeta2
2. If you added a new PredictionProvider variant, implement a formatting arm in the match at crates/edit_prediction_cli/src/format_prompt.rs:68
3. Preferably return an anyhow error (`bail!`) for unsupported providers instead of panicking so the CLI reports it cleanly

Example fix

// before
let args = FormatPromptArgs { provider: PredictionProvider::Zeta(..), .. }; // panic: Cannot format prompt

// after
let args = FormatPromptArgs { provider: PredictionProvider::Zeta2(..), .. };

let supports_formatting = matches!(
    args.provider,
    PredictionProvider::Teacher(..)
        | PredictionProvider::TeacherNonBatching(..)
        | PredictionProvider::TeacherJumps(..)
        | PredictionProvider::TeacherJumpsNonBatching(..)
        | PredictionProvider::Zeta2(..)
);
anyhow::ensure!(supports_formatting, "provider does not support formatting: {:?}", args.provider);

fn supports_prompt_formatting(provider: &PredictionProvider) -> bool {
    matches!(
        provider,
        PredictionProvider::Teacher(..)
            | PredictionProvider::TeacherNonBatching(..)
            | PredictionProvider::TeacherJumps(..)
            | PredictionProvider::TeacherJumpsNonBatching(..)
            | PredictionProvider::Zeta2(..)
    )
}

When it happens

Trigger: Running the format-prompt step with a provider flag that only supports inference (e.g. the zeta client provider) instead of teacher/teacher-jumps/zeta2 variants; or adding a new PredictionProvider variant without extending this match.

Common situations: Copying a `--provider` value from another subcommand that accepts inference providers; introducing a new provider enum variant and forgetting format_prompt.rs.

Related errors

• {} has invalid example extension `{ext}`
• --in-place requires exactly one input file
• output dir is required
• Fatal error: {:?}
• prompt file not found: {name}

AI-assisted analysis of zed-industries/zed@f4178619ac (2026-08-20). Data as JSON: /api/errors/ec3542701948bde7. Report an issue: GitHub.