Delta Types

DeltaMind defines 11 delta types. Each represents a specific kind of state change in a conversation. Deltas are typed unions — the TypeScript compiler enforces field requirements per kind.

Backbone deltas

These are the primary state mutations that drive the working set.

goal_set

What the session is trying to achieve. Goals are broad — “build a REST API” not “write the auth middleware.”

{
  kind: "goal_set",
  id: "item-1",
  summary: "Build a REST API with TypeScript",
  confidence: "high",
  scope: "session",
  sourceTurns: [{ turnId: "t-1" }],
  timestamp: "2026-03-11T..."
}

decision_made

A settled choice. The user or assistant decided something concrete.

Fields: id, summary, alternatives (rejected options, if mentioned), confidence, scope, sourceTurns.

decision_revised

A change to a prior decision. Points to the original via targetId.

Fields: targetId (must reference an existing decision), summary (the new decision), sourceTurns.

The reconciler enforces type scoping: decision_revised can only target decisions. Attempting to revise a constraint with this delta type produces a rejection.

constraint_added

A rule, boundary, or requirement. “No external databases.” “Must support offline mode.” “Budget is $500.”

Fields: id, summary, hard (boolean — hard constraints are non-negotiable), confidence, scope, sourceTurns.

constraint_revised

A change to an existing constraint. Includes a mode field:

• relaxed — the constraint was loosened (“allow commander as sole exception to zero-dep”)
• tightened — the constraint was made stricter (“actually, no exceptions at all”)
• amended — the constraint was modified in a way that’s neither purely looser nor stricter

Fields: targetId (must reference an existing constraint), summary, mode, sourceTurns.

This delta type was added in Phase 2C after model sweep data showed that constraint relaxations were being forced into decision_revised, causing type-mismatch rejections.

task_opened

Work to be done. Concrete and actionable.

Fields: id, summary, sourceTurns.

task_closed

Work completed or abandoned. Points to the open task via targetId.

Fields: targetId, resolution (“completed” or “abandoned”), sourceTurns.

Knowledge deltas

fact_learned

A stable piece of knowledge. Not a decision — a fact. “The API uses port 3000.” “The database is PostgreSQL 15.”

Fields: id, summary, confidence, scope, sourceTurns.

hypothesis_introduced

A tentative idea. Explicitly not a decision. “Maybe we should use Redis for caching?” stays a hypothesis until explicitly promoted.

This distinction is critical for safety. The system’s zero-canonization invariant depends on hypotheses remaining tentative. They are tagged with tentative status and excluded from memory promotion suggestions.

Fields: id, summary, confidence (usually “low” or “medium”), sourceTurns.

branch_created

Unresolved alternatives. “We could do A, B, or C.” Preserved as a fork, not flattened.

Fields: id, alternatives (string array), sourceTurns.

Branch items are tagged with "branch" and excluded from memory promotion.

Lifecycle delta

item_superseded

Marks an existing item as replaced by something newer. The old item’s status changes to superseded but it remains in state for history.

Fields: targetId (the item being superseded), newItemId (optional — what replaced it), reason, sourceTurns.

Delta flow

Turn text → Extractor emits CandidateDelta → Normalizer deduplicates → Reconciler applies → State updated

The extractor proposes. The reconciler decides. Invalid proposals are rejected with reasons logged to provenance.