v0.21.0 - Governed Memory Under Change

Agent Memory Bridge 0.21.0 makes stored guidance more conservative when its
source, lineage, premise, or task domain changes.

0.21.0 = governed memory under change without widening the public surface.

What Shipped

• Explicit forget operations now write content-redacted tombstones in the
  same transaction as memory, FTS, and embedding-sidecar deletion. A failed
  tombstone write rolls the operation back.
• Cascades are limited to exact, structured, machine-owned lineage. Records
  with uncertain or semantic relationships are retained with degraded lineage
  evidence so the missing source remains auditable.
• Task assembly follows bounded transitive supersession, keeps only the current
  actionable generation, and surfaces current-state evidence when a premise
  such as an active rollout, incident, migration, feature, or approval changes.
• Procedures with declared domains are rejected for mismatched task domains.
  Legacy unscoped procedures remain eligible with a warning rather than being
  assigned an inferred policy automatically.

Executable Evidence

The fixed governed-change manifest defines 20 cases: five each for deletion
residue, lifecycle/supersession, changed-premise usefulness, and cross-domain
transfer. Every case runs in a fresh temporary MemoryStore with two
checkpoints.

The checked report passed its exact-manifest gate:

v021_case_count = 20
v021_flat_baseline_hazards = 17
v021_flat_baseline_hazards_expected = 17/20
v021_governed_failures = 0
v021_governed_failures_target = 0/20
v021_governed_checkpoint_passes = 40
v021_governed_checkpoint_passes_target = 40/40
v021_public_mcp_tool_count = 10
v021_auto_writeback_count = 0
v021_config_write_count = 0
v021_durable_live_writeback_count = 0

The full test suite reports 372 passed. Public-surface and onboarding checks
remain part of the release validation.

Boundaries

• The public MCP surface remains 10 tools. No lineage, task-domain, or policy
  tool was added.
• forget is still an explicit mutating operation. This release does not
  automatically delete, promote, rewrite, approve, or write back memory.
• Tombstones retain deletion metadata, not forgotten content. This is an audit
  boundary, not a claim of general machine unlearning or GDPR compliance.
• Tombstones are scoped to deleted record IDs. They do not block a caller from
  explicitly storing the same content later under a new ID.
• Supersession and dependency handling use bounded relation-lite lineage. This
  is not a graph database or a general graph-memory system.
• The executable proof is local deterministic evidence, not external vendor
  certification or a guarantee for every client and workload.

Proof details are in
benchmark/README.md and the checked
v0.21 governed-change report.