diff --git a/CHANGELOG.md b/CHANGELOG.md
index 17daa1b..e371740 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+(nothing yet)
+
+## 0.13.0 — 2026-05-21
+
 ### Added
 
 - **`add-encoding-partition` Phase 1** — locks the API surface for
diff --git a/openspec/changes/add-encoding-partition/design.md b/openspec/changes/archive/2026-05-21-add-encoding-partition/design.md
similarity index 100%
rename from openspec/changes/add-encoding-partition/design.md
rename to openspec/changes/archive/2026-05-21-add-encoding-partition/design.md
diff --git a/openspec/changes/add-encoding-partition/proposal.md b/openspec/changes/archive/2026-05-21-add-encoding-partition/proposal.md
similarity index 100%
rename from openspec/changes/add-encoding-partition/proposal.md
rename to openspec/changes/archive/2026-05-21-add-encoding-partition/proposal.md
diff --git a/openspec/changes/add-encoding-partition/specs/pareto-compression/spec.md b/openspec/changes/archive/2026-05-21-add-encoding-partition/specs/pareto-compression/spec.md
similarity index 100%
rename from openspec/changes/add-encoding-partition/specs/pareto-compression/spec.md
rename to openspec/changes/archive/2026-05-21-add-encoding-partition/specs/pareto-compression/spec.md
diff --git a/openspec/changes/add-encoding-partition/tasks.md b/openspec/changes/archive/2026-05-21-add-encoding-partition/tasks.md
similarity index 100%
rename from openspec/changes/add-encoding-partition/tasks.md
rename to openspec/changes/archive/2026-05-21-add-encoding-partition/tasks.md
diff --git a/polygram/__init__.py b/polygram/__init__.py
index b57171b..40e7032 100644
--- a/polygram/__init__.py
+++ b/polygram/__init__.py
@@ -96,7 +96,7 @@
     load_toy_sae,
 )
 
-__version__ = "0.12.0"
+__version__ = "0.13.0"
 
 __all__ = [
     "BatchExperiment",