Package com.google.genkit.ai.agent.internal

Class LeafSelection

java.lang.Object

com.google.genkit.ai.agent.internal.LeafSelection

public final class LeafSelection
extends Object

Utility for selecting the leaf snapshot from a collection of snapshots in a session's parent-chain.

A leaf is a snapshot whose snapshotId is not referenced as a parentId by any other snapshot in the list.

Method Summary

Modifier and Type	Method	Description
static <S> SessionSnapshot<S>	selectLeaf(List<SessionSnapshot<S>> snapshots, boolean rejectBranching)	Selects the leaf snapshot from the given list.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

selectLeaf

public static <S> SessionSnapshot<S> selectLeaf(List<SessionSnapshot<S>> snapshots,
 boolean rejectBranching)

Selects the leaf snapshot from the given list.

Selection rules:

1. Empty list — returns null. An empty input carries no information about a cycle, so returning null (no snapshot found) is the correct behaviour.
2. Exactly one leaf — returns it directly.
3. Zero leaves in a non-empty list — the chain is corrupt (cycle). Throws GenkitException with error code FAILED_PRECONDITION.
4. More than one leaf — if rejectBranching is true, throws GenkitException with error code FAILED_PRECONDITION. Otherwise the most recent leaf is returned (by createdAt parsed as Instant; null createdAt is treated as the epoch / earliest). Ties are broken by snapshotId in natural (lexicographic) ascending order, taking the greater ID.

Type Parameters:

S - the type of custom session state

Parameters:

snapshots - the full list of snapshots for a session (may be empty)

rejectBranching - if true, more than one leaf is treated as an error

Returns:

the selected leaf snapshot, or null if the input list is empty

Throws:

GenkitException - with FAILED_PRECONDITION when the chain contains a cycle or (with rejectBranching=true) multiple leaves