MECHANISM · RELIABILITY · CORE

Session Replay and Branching

Rebuild derived session state from an append-only event log and create lineage-preserving branches without rewriting the parent run.

1 lessons0 agent snapshots1 experiments

reliabilitysession-replayproblem → policy → evidence

L0Intuitioncomplete

L1Buildcomplete

L2Engineeringpartial

L3Architecturepartial

L4Researchmissing

DEPENDENCY GRAPH · READER PATH

What feeds it, and what does it unlock?

Arrows show learning and design dependencies, not runtime data flow. Follow any node to continue through the Atlas.

Prerequisites

event-streamEvent Stream

session-replaySession Replay and BranchingCurrent research boundary

UnlocksNo dependents yet

Bilingual deep dive missing

Rebuild derived session state from an append-only event log and create lineage-preserving branches without rewriting the parent run.

The structured record is in the Atlas, but the L0–L4 article has not passed content review.

AGENT MAPPING · EVIDENCE ONLY

Snapshot implementations

An implementation enters the map only when both a snapshot and claims exist; unknowns remain visible.

UNKNOWN · EVIDENCE GAPClaude Code

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

UNKNOWN · EVIDENCE GAPCodex

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

UNKNOWN · EVIDENCE GAPGrok Build

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

UNKNOWN · EVIDENCE GAPOpenCode

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

UNKNOWN · EVIDENCE GAPPi

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

UNKNOWN · EVIDENCE GAPReasonix

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

UNKNOWN · EVIDENCE GAPReference Harness

No implementation currently clears the Snapshot + Claim threshold; this is not a claim that the product lacks the capability.

Inspect coverage boundary →

No reviewed Agent claims

The teaching-harness reference does not automatically become an architectural claim about any vendor agent.

EXPERIMENTS · EXERCISES

What has actually been tested?

Formal experiments are separate from course exercises. Exercises can validate the reference implementation but cannot replace Native evidence from a real agent.

controlled · completeReference Harness replay and branch probeCan append-only events deterministically rebuild session state and create a branch from an explicit sequence boundary?

s07-session-replayobserve

Verify replay lineage

The same run produces a stable replay fingerprint and a branch at sequence 2.

python3 -m curriculum.golden verify s07-session-replay

s07-session-replaymodify

Test journal invariants

Gapped sequences, mixed runs, and out-of-range forks are rejected without rewriting the parent log.

python3 -m unittest curriculum.tests.test_vertical_slice.VerticalSliceTests.test_s07_replays_and_branches -v

OPEN QUESTIONS · L4

01

Which derived views must be rebuildable after a schema migration?

02

Where should a branch inherit artifacts by reference instead of copying them?

03

How should corrupted or partially durable event tails be repaired?