Hmbown/CodeWhale · error · io::Error

Ambiguous prefix ' ' matches sessions

Error message

Ambiguous prefix '{}' matches {} sessions

What it means

Prefix resolution also rejects a prefix matching more than one session, returning an InvalidInput io::Error listing the match count. The library throws this because it cannot choose between multiple candidates and refuses to pick arbitrarily.

Solutions

1. Lengthen the prefix until it uniquely identifies one session (copy more characters from the full id).
2. Use the full session id to be unambiguous.
3. Enumerate sessions first and disambiguate in your own tooling before resolving.

Example fix

// before
let id = manager.resolve_session_prefix("2026")?; // ambiguous
// after
let id = manager.resolve_session_prefix("20260921-a1b2")?; // longer, unique

fn prefix_is_unique(prefix: &str, sessions: &[SessionInfo]) -> bool {
    sessions.iter().filter(|s| s.id.starts_with(prefix)).count() == 1
}

match resolve_session_prefix(prefix) {
    Err(e) if e.kind() == std::io::ErrorKind::InvalidInput => {
        eprintln!("prefix '{prefix}' is ambiguous; use a longer prefix");
        Err(e)
    }
    other => other,
}

When it happens

Trigger: Calling the prefix-resolution API with a prefix shared by two or more session ids (e.g. a single common character or a shared timestamp prefix).

Common situations: Short prefixes in scripts or shell history where many sessions share the leading characters.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• No session found with prefix
• Agent session name ' ' is ambiguous; use an agent_id
• Ambiguous task prefix
• correction must match exactly one active note on the…
• could not resolve spillover path (empty/invalid id or…

AI-assisted analysis of Hmbown/CodeWhale@73e0f67d83 (2026-09-22). Data as JSON: /api/errors/bcdf7d404215ef57. Report an issue: GitHub.

Appendix: source

Thrown at crates/tui/src/session_manager.rs:2499

        self.load_session(&self.resolve_session_id_prefix(prefix)?)
    }

    /// Resolve a unique ID without applying resume-time repair to its record.
    pub(crate) fn resolve_session_id_prefix(&self, prefix: &str) -> std::io::Result<String> {
        let sessions = self.list_sessions()?;

        let matches: Vec<_> = sessions
            .into_iter()
            .filter(|s| s.id.starts_with(prefix))
            .collect();

        match matches.len() {
            0 => Err(std::io::Error::new(
                std::io::ErrorKind::NotFound,
                format!("No session found with prefix: {prefix}"),
            )),
            1 => Ok(matches[0].id.clone()),
            _ => Err(std::io::Error::new(
                std::io::ErrorKind::InvalidInput,
                format!(
                    "Ambiguous prefix '{}' matches {} sessions",
                    prefix,
                    matches.len()
                ),
            )),
        }
    }

    /// List all saved sessions, sorted by most recently updated
    pub fn list_sessions(&self) -> std::io::Result<Vec<SessionMetadata>> {
        let mut sessions = Vec::new();

        for entry in fs::read_dir(&self.sessions_dir)? {
            let entry = entry?;
            let path = entry.path();

View on GitHub (pinned to 73e0f67d83)