Struct SessionState 

pub struct SessionState { /* private fields */ }

Thread-safe session state container for per-session key-value storage.

This allows handlers to store and retrieve state that persists across requests within a single MCP session. The state is typed as JSON values to support flexible data storage.

Thread Safety

SessionState is designed for concurrent access from multiple handlers. Operations are synchronized via an internal mutex.

Example

// In a tool handler:
ctx.set_state("counter", 42);
let count: Option<i32> = ctx.get_state("counter");

Implementations

impl SessionState

pub fn new() -> Self

Creates a new empty session state.

pub fn with_local_overrides(&self) -> Self

Returns a view with request-local overrides layered on top of the shared session state.

Cloning the returned value preserves the same local override map, while ordinary writes continue to target the shared session state.

pub fn snapshot(&self) -> Self

Creates an isolated snapshot of the current session state.

Unlike Clone, which shares the same underlying storage, this copies the current key-value map into a fresh container so later writes do not bleed across requests.

pub fn get<T: DeserializeOwned>(&self, key: &str) -> Option<T>

Gets a value from session state by key.

Returns None if the key doesn’t exist or if deserialization fails.

Type Parameters

• T - The expected type of the value (must implement Deserialize)

pub fn get_raw(&self, key: &str) -> Option<Value>

Gets a raw JSON value from session state by key.

Returns None if the key doesn’t exist.

pub fn set<T: Serialize>(&self, key: impl Into<String>, value: T) -> bool

Sets a value in session state.

The value is serialized to JSON for storage. Returns true if the value was successfully stored.

Type Parameters

• T - The type of the value (must implement Serialize)

pub fn set_raw(&self, key: impl Into<String>, value: Value) -> bool

Sets a raw JSON value in session state.

Returns true if the value was successfully stored.

pub fn set_local_raw(&self, key: impl Into<String>, value: Value) -> bool

Sets a request-local raw JSON value layered over the shared session state.

Returns false if this state does not have local overrides enabled.

pub fn set_local<T: Serialize>(&self, key: impl Into<String>, value: T) -> bool

Sets a request-local value layered over the shared session state.

Returns false if serialization fails or local overrides are unavailable.

pub fn remove(&self, key: &str) -> Option<Value>

Removes a value from session state.

Returns the previous value if it existed.

pub fn contains(&self, key: &str) -> bool

Checks if a key exists in session state.

pub fn len(&self) -> usize

Returns the number of entries in session state.

pub fn is_empty(&self) -> bool

Returns true if session state is empty.

pub fn clear(&self)

Clears all session state.

impl SessionState

pub fn is_tool_enabled(&self, name: &str) -> bool

Returns whether a tool is enabled (not disabled) for this session.

Tools are enabled by default unless explicitly disabled.

pub fn is_resource_enabled(&self, uri: &str) -> bool

Returns whether a resource is enabled (not disabled) for this session.

Resources are enabled by default unless explicitly disabled.

pub fn is_prompt_enabled(&self, name: &str) -> bool

Returns whether a prompt is enabled (not disabled) for this session.

Prompts are enabled by default unless explicitly disabled.

pub fn disabled_tools(&self) -> HashSet<String>

Returns the set of disabled tools.

pub fn disabled_resources(&self) -> HashSet<String>

Returns the set of disabled resources.

pub fn disabled_prompts(&self) -> HashSet<String>

Returns the set of disabled prompts.

Trait Implementations

impl Clone for SessionState

fn clone(&self) -> SessionState

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SessionState

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

Formats the value using the given formatter.

impl Default for SessionState

fn default() -> SessionState

Returns the “default value” for a type.