Summary
Allow conversations to be forked at any message index — creating a new session that starts from a checkpoint of an existing one. Enables A/B testing of agent configurations, user "what-if" exploration, and red-teaming. Only LangGraph offers this today — a differentiating feature for the framework.
Requirements
POST /v1/sessions/{id}/fork endpoint with at_message parameter (0-based index)- Creates a new session with messages
[0..at_message] copied from the source
- Forked session inherits tenant context and configuration but gets a new
session_id
- Session store schema changes: messages stored as ordered, addressable sequence (not a single JSON blob)
- Fork metadata:
source_session_id, fork_point tracked for lineage
GET /v1/sessions/{id}/forks — list all sessions forked from a given session
FIPS Considerations
No specific concerns. Forking is a data copy operation. No new cryptographic operations introduced.
Implementation Notes
Requires refactoring session storage from blob-level to message-level addressing. Each message gets an index and is independently queryable. This is the most architecturally impactful change in this batch — it affects SqliteSessionStore and PostgresSessionStore schemas and will require a migration path for existing sessions. The fork lineage tracking enables tree visualization of conversation branches for evaluation and debugging workflows.
Companion Issues
Companion issues will be filed on fips-agents/gateway-template, fips-agents/ui-template, fips-agents/fips-agents-cli, and fips-agents/examples.
Size
M-L
Summary
Allow conversations to be forked at any message index — creating a new session that starts from a checkpoint of an existing one. Enables A/B testing of agent configurations, user "what-if" exploration, and red-teaming. Only LangGraph offers this today — a differentiating feature for the framework.
Requirements
POST /v1/sessions/{id}/forkendpoint withat_messageparameter (0-based index)[0..at_message]copied from the sourcesession_idsource_session_id,fork_pointtracked for lineageGET /v1/sessions/{id}/forks— list all sessions forked from a given sessionFIPS Considerations
No specific concerns. Forking is a data copy operation. No new cryptographic operations introduced.
Implementation Notes
Requires refactoring session storage from blob-level to message-level addressing. Each message gets an index and is independently queryable. This is the most architecturally impactful change in this batch — it affects
SqliteSessionStoreandPostgresSessionStoreschemas and will require a migration path for existing sessions. The fork lineage tracking enables tree visualization of conversation branches for evaluation and debugging workflows.Companion Issues
Companion issues will be filed on fips-agents/gateway-template, fips-agents/ui-template, fips-agents/fips-agents-cli, and fips-agents/examples.
Size
M-L