Enum ContextSlot 

#[non_exhaustive]
pub enum ContextSlot {
    Summaries(Option<Message>),
    CrossSession(Option<Message>),
    SemanticRecall(Option<Message>, Option<f32>),
    DocumentRag(Option<Message>),
    Corrections(Option<Message>),
    CodeContext(Option<String>),
    GraphFacts(Option<Message>),
    PersonaFacts(Option<Message>),
    TrajectoryHints(Option<Message>),
    TreeMemory(Option<Message>),
    ReasoningStrategies(Option<Message>, Option<JoinHandle<()>>),
}

Tagged output of each concurrent context-fetch future.

Using an enum instead of a tuple allows individual sources to be added or removed (including cfg-gated ones) without rewriting the join combinator.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Summaries(Option<Message>)

Past-session summaries (contextual recall).

CrossSession(Option<Message>)

Cross-session memory recall.

SemanticRecall(Option<Message>, Option<f32>)

Semantic recall result. Carries the formatted message and the top-1 similarity score.

DocumentRag(Option<Message>)

Document RAG result.

Corrections(Option<Message>)

Past user corrections recalled for this turn.

CodeContext(Option<String>)

Code-index RAG result (repo-map or file context).

GraphFacts(Option<Message>)

Knowledge graph fact recall.

PersonaFacts(Option<Message>)

Persona memory facts injected after the system prompt (#2461).

TrajectoryHints(Option<Message>)

Top-k procedural trajectory hints recalled for the current turn (#2498).

TreeMemory(Option<Message>)

TiMem tree summary nodes recalled for context (#2262).

ReasoningStrategies(Option<Message>, Option<JoinHandle<()>>)

Distilled reasoning strategies recalled for the current turn (#3343).

The second field carries the JoinHandle for the background mark_reasoning_used task spawned after injection. Callers must store it in PreparedContext::background_tasks.