diff --git a/CLAUDE.md b/CLAUDE.md
index 135cd4d..f6c836d 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -114,6 +114,7 @@ Speckit manages **what** to build (specs as living documents). RPI manages **how
 - `specs/003-combatant-state/` — HP, AC, conditions, concentration, initiative
 - `specs/004-bestiary/` — search index, stat blocks, source management, panel UX
 - `specs/005-player-characters/` — persistent player character templates (CRUD), search & add to encounters, color/icon visual distinction, `PlayerCharacterStore` port
+- `specs/006-undo-redo/` — undo/redo for encounter state mutations
 
 ## Constitution (key principles)
 
diff --git a/specs/037-undo-redo/checklists/requirements.md b/specs/006-undo-redo/checklists/requirements.md
similarity index 100%
rename from specs/037-undo-redo/checklists/requirements.md
rename to specs/006-undo-redo/checklists/requirements.md
diff --git a/specs/037-undo-redo/data-model.md b/specs/006-undo-redo/data-model.md
similarity index 99%
rename from specs/037-undo-redo/data-model.md
rename to specs/006-undo-redo/data-model.md
index d321910..497ce95 100644
--- a/specs/037-undo-redo/data-model.md
+++ b/specs/006-undo-redo/data-model.md
@@ -1,6 +1,6 @@
 # Data Model: Undo/Redo
 
-**Feature**: 037-undo-redo
+**Feature**: 006-undo-redo
 **Date**: 2026-03-26
 
 ## Entities
diff --git a/specs/037-undo-redo/plan.md b/specs/006-undo-redo/plan.md
similarity index 96%
rename from specs/037-undo-redo/plan.md
rename to specs/006-undo-redo/plan.md
index 22f1967..210e0f5 100644
--- a/specs/037-undo-redo/plan.md
+++ b/specs/006-undo-redo/plan.md
@@ -1,7 +1,7 @@
 # Implementation Plan: Undo/Redo
 
-**Branch**: `037-undo-redo` | **Date**: 2026-03-26 | **Spec**: [spec.md](spec.md)
-**Input**: Feature specification from `/specs/037-undo-redo/spec.md`
+**Branch**: `006-undo-redo` | **Date**: 2026-03-26 | **Spec**: [spec.md](spec.md)
+**Input**: Feature specification from `/specs/006-undo-redo/spec.md`
 
 ## Summary
 
@@ -40,7 +40,7 @@ Add undo/redo capability for all encounter state changes using the memento patte
 ### Documentation (this feature)
 
 ```text
-specs/037-undo-redo/
+specs/006-undo-redo/
 ├── plan.md              # This file
 ├── research.md          # Phase 0 output
 ├── data-model.md        # Phase 1 output
diff --git a/specs/037-undo-redo/quickstart.md b/specs/006-undo-redo/quickstart.md
similarity index 98%
rename from specs/037-undo-redo/quickstart.md
rename to specs/006-undo-redo/quickstart.md
index 053e62b..25f7e11 100644
--- a/specs/037-undo-redo/quickstart.md
+++ b/specs/006-undo-redo/quickstart.md
@@ -1,6 +1,6 @@
 # Quickstart: Undo/Redo
 
-**Feature**: 037-undo-redo
+**Feature**: 006-undo-redo
 **Date**: 2026-03-26
 
 ## Overview
diff --git a/specs/037-undo-redo/research.md b/specs/006-undo-redo/research.md
similarity index 99%
rename from specs/037-undo-redo/research.md
rename to specs/006-undo-redo/research.md
index a4f3e22..f10ee32 100644
--- a/specs/037-undo-redo/research.md
+++ b/specs/006-undo-redo/research.md
@@ -1,6 +1,6 @@
 # Research: Undo/Redo for Encounter Actions
 
-**Feature**: 037-undo-redo
+**Feature**: 006-undo-redo
 **Date**: 2026-03-26
 
 ## Decision 1: Undo/Redo Strategy — Memento (Snapshots) vs Command (Events)
diff --git a/specs/037-undo-redo/spec.md b/specs/006-undo-redo/spec.md
similarity index 99%
rename from specs/037-undo-redo/spec.md
rename to specs/006-undo-redo/spec.md
index 509fe4d..97044db 100644
--- a/specs/037-undo-redo/spec.md
+++ b/specs/006-undo-redo/spec.md
@@ -1,6 +1,6 @@
 # Feature Specification: Undo/Redo
 
-**Feature Branch**: `037-undo-redo`
+**Feature Branch**: `006-undo-redo`
 **Created**: 2026-03-26
 **Status**: Draft
 **Input**: Gitea issue #16 — Undo/redo for encounter actions
diff --git a/specs/037-undo-redo/tasks.md b/specs/006-undo-redo/tasks.md
similarity index 99%
rename from specs/037-undo-redo/tasks.md
rename to specs/006-undo-redo/tasks.md
index 9260626..fee2a9c 100644
--- a/specs/037-undo-redo/tasks.md
+++ b/specs/006-undo-redo/tasks.md
@@ -1,6 +1,6 @@
 # Tasks: Undo/Redo
 
-**Input**: Design documents from `/specs/037-undo-redo/`
+**Input**: Design documents from `/specs/006-undo-redo/`
 **Prerequisites**: plan.md, spec.md, research.md, data-model.md, quickstart.md
 
 **Tests**: Domain tests included (pure function testing is standard for this project per CLAUDE.md).