fix: resolve broken forked sessions with compactions due to missing parent-child message references #6445
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…arent-child message references When forking a session, message IDs are regenerated but parentID references in assistant messages were not updated to point to the new IDs. This broke features that rely on parent-child relationships, such as compaction breakpoints. ## Problem Forking a compacted session would fail with: ``` prompt is too long: 203573 tokens > 200000 maximum ``` The forked session didn't honor the compaction breakpoint because the parent-child message relationships were broken. ## Fix Added an ID mapping that tracks old ID -> new ID, then updates parentID references when cloning assistant messages. ## Changes - packages/opencode/src/session/index.ts - Add ID mapping in fork function to preserve parent-child relationships
ryanwyler
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Summary
Forking a compacted session fails with:
The bug was introduced in commit
9a0735de7on October 6, 2025 with the commit message "Add session forking functionality and simplify remove logic".This was a bug from day one of the fork feature - it just wasn't noticed until compaction logic (which relies on parent-child relationships) was added later.
The Bug
When forking was originally implemented, each message gets a new
idviaIdentifier.ascending("message"), but the code never updated theparentIDfield. Assistant messages have aparentIDthat points to their corresponding user message. After forking, thoseparentIDvalues still reference the old message IDs from the source session, which don't exist in the forked session.Fix
Maintain an ID mapping (old -> new) when cloning messages, updating
parentIDreferences to point to the new IDs. This restores the parent-child relationships thatfilterCompacted()relies on to detect compaction breakpoints.