diff --git a/docs_v1.0/M4_HANDOVER/2026-05-13_api_test_v2_compatibility_response.md b/docs_v1.0/M4_HANDOVER/2026-05-13_api_test_v2_compatibility_response.md
new file mode 100644
index 0000000..c35b56f
--- /dev/null
+++ b/docs_v1.0/M4_HANDOVER/2026-05-13_api_test_v2_compatibility_response.md
@@ -0,0 +1,40 @@
+# M4 Compatibility Response
+
+**Date**: 2026-05-13
+**From**: M5
+**To**: M4
+**Re**: [2026-05-13_api_test_v2_compatibility.md](2026-05-13_api_test_v2_compatibility.md)
+
+---
+
+## Resolution
+
+| # | Issue | Status | Fix |
+|---|-------|:--:|------|
+| 1 | `GET /api/v1/identity/2b0ddefe...` → 404 | ✅ Resolved | UUID `2b0ddefe` = Cary Grant (TMDB, confirmed). Exists in v2.0. Working. |
+| 2 | `GET /api/v1/file/<uuid>/chunk/0-01` → 404 | ✅ Fixed | Updated test to `chunk/0` (v2.0 format). `api_test.sh` now 39/39. |
+
+## Test Results
+
+```
+==========================================
+  Results: 39 passed, 0 failed
+==========================================
+```
+
+## v2.0 Data Format Changes
+
+| Field | v1.0.3 | v2.0 |
+|-------|--------|------|
+| `chunk_id` | `0-01`, `1-03` (parent-correction) | `0`, `1`, `2`... (sequential) |
+| identity UUIDs | Auto-generated per-file | Preserved across re-imports |
+| `chunk_index` field | Present in API response | **Removed** (chunk_id is sufficient) |
+
+## Known Server Setup Issue
+
+Server must be started from project root directory:
+```bash
+cd /Users/accusys/momentry_core_0.1
+cargo run --bin momentry_playground -- server --port 3003
+```
+Otherwise `.env.development` won't load and `DATABASE_SCHEMA` defaults to `public`.
diff --git a/docs_v1.0/M4_HANDOVER/api_test.sh b/docs_v1.0/M4_HANDOVER/api_test.sh
index aa14761..f409a41 100644
--- a/docs_v1.0/M4_HANDOVER/api_test.sh
+++ b/docs_v1.0/M4_HANDOVER/api_test.sh
@@ -176,7 +176,7 @@ test_get "GET /api/v1/agents/5w1h/status" "/api/v1/agents/5w1h/status"
 
 # ── Chunk detail endpoint ──
 title "Chunk detail"
-test_get "GET /api/v1/file/$UUID/chunk/0-01" "/api/v1/file/$UUID/chunk/0-01"
+test_get "GET /api/v1/file/$UUID/chunk/0" "/api/v1/file/$UUID/chunk/0"
 test_get "GET /api/v1/file/$UUID/chunk/nonexistent" "/api/v1/file/$UUID/chunk/nonexistent" 404
 
 # ── Specific search tests for chunk_id format ──
diff --git a/docs_v1.0/M4_workspace/2026-05-13_api_test_v2_compatibility_response.md b/docs_v1.0/M4_workspace/2026-05-13_api_test_v2_compatibility_response.md
new file mode 100644
index 0000000..c35b56f
--- /dev/null
+++ b/docs_v1.0/M4_workspace/2026-05-13_api_test_v2_compatibility_response.md
@@ -0,0 +1,40 @@
+# M4 Compatibility Response
+
+**Date**: 2026-05-13
+**From**: M5
+**To**: M4
+**Re**: [2026-05-13_api_test_v2_compatibility.md](2026-05-13_api_test_v2_compatibility.md)
+
+---
+
+## Resolution
+
+| # | Issue | Status | Fix |
+|---|-------|:--:|------|
+| 1 | `GET /api/v1/identity/2b0ddefe...` → 404 | ✅ Resolved | UUID `2b0ddefe` = Cary Grant (TMDB, confirmed). Exists in v2.0. Working. |
+| 2 | `GET /api/v1/file/<uuid>/chunk/0-01` → 404 | ✅ Fixed | Updated test to `chunk/0` (v2.0 format). `api_test.sh` now 39/39. |
+
+## Test Results
+
+```
+==========================================
+  Results: 39 passed, 0 failed
+==========================================
+```
+
+## v2.0 Data Format Changes
+
+| Field | v1.0.3 | v2.0 |
+|-------|--------|------|
+| `chunk_id` | `0-01`, `1-03` (parent-correction) | `0`, `1`, `2`... (sequential) |
+| identity UUIDs | Auto-generated per-file | Preserved across re-imports |
+| `chunk_index` field | Present in API response | **Removed** (chunk_id is sufficient) |
+
+## Known Server Setup Issue
+
+Server must be started from project root directory:
+```bash
+cd /Users/accusys/momentry_core_0.1
+cargo run --bin momentry_playground -- server --port 3003
+```
+Otherwise `.env.development` won't load and `DATABASE_SCHEMA` defaults to `public`.