DAG Versioning

AMFS commits form a directed acyclic graph (DAG), similar to git. Each commit records its parent commit(s), enabling ancestry queries, merge-base computation, and branch history tracking.

Commit Ancestry

When a new commit is created (via transaction() or amfs_commit_batch), AMFS automatically links it to the latest commit on the same branch via parent_ids. Merge commits can have multiple parents.

c1 ← c2 ← c3 ← c4 (main)
           ↖
            c5 ← c6 (feature branch)

Common Ancestor

To merge or compare branches, you often need to find the most recent common ancestor — the point where two lineages diverged.

ancestor_id = mem.common_ancestor("c4", "c6")
# Returns "c2" — the fork point

The algorithm uses parallel BFS from both commits, returning the first commit that appears in both traversals.

Branch HEAD Tracking

Each branch tracks its head_commit_id (the latest commit) and base_commit_id (where it forked from its parent branch). This enables efficient diff and merge operations.

API Surface

Method	Description
mem.common_ancestor(a, b)	Python SDK
mem.commonAncestor(a, b)	TypeScript SDK
amfs_merge_base(commit_a, commit_b)	MCP tool
POST /api/v1/merge-base	HTTP endpoint

OSS vs Pro

Feature	OSS	Pro
Parent commit linking	Yes	Yes
Common ancestor computation	Yes	Yes
Branch HEAD tracking	Yes	Yes
Cherry-pick across branches	—	Yes
Sacred Timeline DAG visualization	—	Yes