Enum ProtocolVersion 

pub enum ProtocolVersion {
    V2024_11_05,
    V2025_03_26,
    V2025_06_18,
    V2025_11_25,
    V2026_07_28,
    Unknown(ReleaseDate),
}

A published MCP revision, or one published after this build was compiled.

Ordered oldest to newest, which is also publication order. See the module docs for why that is an invariant rather than a coincidence.

Variants

V2024_11_05

The first published revision. Defines stdio and the legacy HTTP+SSE transport, and is the only revision where TransportKind::LegacySse is defined at all.

V2025_03_26

Replaced the legacy HTTP+SSE transport with Streamable HTTP.

V2025_06_18

Removed JSON-RPC batching and added structured tool output.

V2025_11_25

Added URL-mode elicitation, icons, and experimental tasks.

V2026_07_28

Made the protocol stateless: the initialize handshake is gone and every request carries its version in _meta.

Unknown(ReleaseDate)

A revision published after this build, identified by its release date.

Only ever holds a date at or after ReleaseDate::V2024_11_05, and in practice only one newer than ProtocolVersion::V2026_07_28 — see the module docs.

Implementations

impl ProtocolVersion

pub const KNOWN: [Self; 5]

Every revision this build has wire types for, oldest first.

draft is not a separate version: upstream’s floating draft schema declares LATEST_PROTOCOL_VERSION = "2026-07-28", the same as the final revision, so it negotiates as that revision. The two differ in schema shape, not in version string, and T08 keys the codec off the version.

pub const fn latest_known() -> Self

The newest revision this build knows.

pub const fn earliest_known() -> Self

The oldest revision this build supports.

pub const fn date(self) -> ReleaseDate

The revision’s release date.

pub fn as_wire(self) -> Cow<'static, str>

The string this revision is negotiated as, borrowed when it is a known one.

Cow rather than &'static str because Unknown has no static spelling; the six known revisions, which is what a codec asks about on the hot path, allocate nothing.

pub const fn is_known(self) -> bool

Whether this build has wire types for the revision.

pub fn is_newer_than_all_known(self) -> bool

Whether this revision was published after the newest one this build knows.

Not const: the comparison comes from a derived Ord, and a derived Ord is not a const-callable operator.

pub fn unknown_after_known( date: ReleaseDate, ) -> Result<Self, UnknownVersionError>

Builds an Unknown from a date, refusing one that would break the ordering invariant.

The public enum variant means this cannot be the only way in, so the function is not private; making it the obvious one is what keeps the invariant from being broken by accident.

Errors

Returns UnknownVersionError::NotAfterKnown when date is at or before Self::latest_known — a date this build should have a variant for, and FromStr would have matched it exactly.

Examples

use protocol_droid::domain::{ProtocolVersion, ReleaseDate};

let future = ProtocolVersion::unknown_after_known("2027-01-01".parse().unwrap())?;
assert!(future.is_newer_than_all_known());

Trait Implementations

impl Clone for ProtocolVersion

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for ProtocolVersion

impl Debug for ProtocolVersion

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for ProtocolVersion

fn fmt(&self, formatter: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for ProtocolVersion

impl FromStr for ProtocolVersion

fn from_str(text: &str) -> Result<Self, Self::Err>

Parses a negotiated version string.

Three outcomes, in order:

1. A known revision’s string becomes that variant. Matched on the whole string first, because that is the only way to reject 2025-03-26x without first having to date-parse it.
2. A well-formed date this build has not heard of becomes Unknown, provided it is at or after the first revision.
3. Everything else is an error.

type Err = ParseProtocolVersionError

The associated error which can be returned from parsing.

impl Hash for ProtocolVersion

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for ProtocolVersion

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl PartialEq for ProtocolVersion

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl PartialOrd for ProtocolVersion

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for ProtocolVersion