eval is only supported for Codex sessions; use `f codex eval

Error message

eval is only supported for Codex sessions; use `f codex eval`

What it means

The Eval action (running evaluations) is Codex-only. When dispatched with Provider::Cursor, run_provider bails with this message pointing to `f codex eval`.

Source

Thrown at src/ai.rs:573

                count,
                path,
            }) => copy_context(session, Provider::Cursor, count, path)?,
            Some(ProviderAiAction::Show {
                session,
                path,
                count,
                full,
            }) => show_session(session, Provider::Cursor, count, path, full)?,
            Some(ProviderAiAction::Runtime { .. }) => {
                bail!(
                    "runtime helpers are only supported for Codex sessions; use `f codex runtime ...`"
                );
            }
            Some(ProviderAiAction::Doctor { .. }) => {
                bail!("doctor is only supported for Codex sessions; use `f codex doctor`");
            }
            Some(ProviderAiAction::Eval { .. }) => {
                bail!("eval is only supported for Codex sessions; use `f codex eval`");
            }
            Some(ProviderAiAction::TouchLaunch { .. }) => {
                bail!(
                    "touch-launch is only supported for Codex sessions; use `f codex touch-launch`"
                );
            }
            Some(ProviderAiAction::EnableGlobal { .. }) => {
                bail!(
                    "global Codex enablement is only supported for Codex sessions; use `f codex enable-global`"
                );
            }
            Some(ProviderAiAction::Daemon { .. }) => {
                bail!("daemon is only supported for Codex sessions; use `f codex daemon ...`");
            }
            Some(ProviderAiAction::Memory { .. }) => {
                bail!("memory is only supported for Codex sessions; use `f codex memory ...`");
            }
            Some(ProviderAiAction::Telemetry { .. }) => {

View on GitHub (pinned to a747e741ae)

Solutions

Use `f codex eval ...` for evaluations
Skip Cursor in eval automation loops or gate on provider capability
Check `f cursor --help` for the supported Cursor subcommand list

Example fix

// before
$ f cursor eval suite.yaml
// error: eval is only supported for Codex sessions
// after
$ f codex eval suite.yaml

Defensive patterns

Strategy: validation

Validate before calling

fn assert_codex_for_eval(provider: &Provider) -> Result<()> {
    if *provider != Provider::Codex {
        bail!("eval requires the codex provider");
    }
    Ok(())
}

Type guard

fn supports_eval(p: &Provider) -> bool { matches!(p, Provider::Codex) }

Try / catch

if let Err(e) = run_provider(Provider::Cursor, Some(ProviderAiAction::Eval { .. })) {
    if e.to_string().contains("eval is only supported") {
        eprintln!("use: f codex eval ...");
    }
}

Prevention

Run evaluations only via `f codex eval`
Skip Cursor providers in eval loops or check capabilities first
Consult `f cursor --help` for the supported action set

When it happens

Trigger: Running `f cursor eval ...` with any eval arguments.

Common situations: Attempt to run prompt evaluations against Cursor sessions; benchmark scripts iterating over providers assuming eval exists everywhere.

Related errors

AI-assisted analysis of nikivdev/code@a747e741ae (2026-09-01). Data as JSON: /api/errors/67cf3811e6d5b12f. Report an issue: GitHub.