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Session object has no field identifying fork origin (parentID only distinguishes subagent children) #53777
Description
Activity
Thanks for the detailed write-up!
OpenCode v2 should already have this. On v2 (including v2.0.24), the
Sessioninfo returned bysession.getandsession.listhas an optionalforkfield. It is set when a session is created by forking:fork?: { sessionID: string // the session it was forked from boundary: { type: "before" | "through"; messageID: string } }
So
session.fork?.sessionIDtells you whether a session is a fork and which session it came from.parentIDis still only for subagent children. Plugins can also listen for thesession.forkedevent, which includes the newsessionID, the source session asparentID, and theboundary.The fields you list (
summary,share,version, …) are from the v1Sessiontype. Your plugin may still be using v1 SDK/plugin types, or calling a v1-style client.Could you check whether
forkshows up when you read a forked session through the v2 plugin client (@opencode/plugin)? If it's still missing, please share:- which package/client and method you call (e.g. the
client.session.getfrom the v2 plugin context, or@opencode-ai/sdk) - the raw JSON you get back for a session created with
/forkorsession.fork
You can reply here or edit the issue. If you edit it, please also leave a comment saying you've updated it, so we know you're done.
Related issues, ordered by likelihood of relevance:
- Feature: generic /compact command, auto-compaction, and fork-aware conversations #4317: the earlier, broader fork-aware conversations proposal (closed as stale)
- [FEATURE]:Expose session metadata in the V2 API so programmatic run sessions are attributable #40384: exposing session metadata in the v2 API
- Forked parent session opens original child session, so Back returns to original parent #42341: UI navigation bug with forked sessions and their children
- which package/client and method you call (e.g. the
Closing this for now. We haven't heard back on whether the existing
forkfield covers your use case.On v2 (including v2.0.24), the
Sessioninfo returned bysession.getandsession.listhas an optionalfork: { sessionID, boundary }field. It is set when a session is created by forking, sosession.fork?.sessionIDtells you whether a session is a fork and which session it came from. Plugins can also listen for thesession.forkedevent. The fields you listed (summary,share,version) are from the v1Sessiontype, so your plugin may still be using v1 types or the v1 SDK.If
forkis still missing when you read a forked session through the v2 plugin client, please reopen this or open a new issue. Include the client and method you call and the raw JSON response, and we'll look into it.
What happened
Plugins that watch forked sessions (built with the
event/session.getplugin hooks) can't tell a forked session apart from a fresh one, because theSessionobject returned byclient.session.get/client.session.messageshas no field identifying its fork origin.Currently
Sessionexposes:id, parentID, title, summary, share, version, time, revert.parentIDidentifies a subagent child session./fork, OpenChamber's fork action, orsession.forkin the API) hasparentID: null, identical to a brand-new top-level session. There is noforkID/sourceSessionID/equivalent field to distinguish the two.Why this matters
A plugin that needs to treat forks differently from fresh sessions (e.g. not re-running first-message logic, or reporting results back to the session a fork came from) has no reliable way to detect that a session is a fork, or which session it was forked from.
Related prior art
This was flagged as part of #4317 ("fork-aware conversations", proposing
parentConversationId/forkID), which was auto-closed as stale (NOT_PLANNED, closed by the 60-day inactivity bot) rather than resolved or rejected on its merits. Its own closing comment invites opening a new issue if still relevant — this is narrower in scope than that issue: just the missing fork-origin field onSession, not the full compaction/provider-cache-key proposal.Suggested fix
Add an optional field to
Session(e.g.fork?: { sessionID: string }orforkedFrom?: string) set when a session is created via fork, so plugins and the SDK consumer can reliably detect and trace fork lineage without guessing fromparentIDabsence.Environment