diff --git a/AGENTS.md b/AGENTS.md
index b2ffd28..567766b 100755
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -14,8 +14,9 @@ Before responding to any user message, you MUST read these files in order:
 4. `~/.config/mosaic/AGENTS.md`
 5. `~/.config/mosaic/TOOLS.md`
 6. `~/.config/mosaic/guides/E2E-DELIVERY.md`
-7. Project-local `AGENTS.md` (if present)
-8. Runtime-specific reference:
+7. `~/.config/mosaic/guides/MEMORY.md`
+8. Project-local `AGENTS.md` (if present)
+9. Runtime-specific reference:
    - Claude: `~/.config/mosaic/runtime/claude/RUNTIME.md`
    - Codex: `~/.config/mosaic/runtime/codex/RUNTIME.md`
    - OpenCode: `~/.config/mosaic/runtime/opencode/RUNTIME.md`
@@ -111,7 +112,6 @@ Load additional guides when the task requires them.
 | QA and test strategy | `~/.config/mosaic/guides/QA-TESTING.md` |
 | Secrets and vault usage | `~/.config/mosaic/guides/VAULT-SECRETS.md` |
 | Orchestrator estimation heuristics | `~/.config/mosaic/guides/ORCHESTRATOR-LEARNINGS.md` |
-| Shared memory patterns | `~/.config/mosaic/guides/MEMORY.md` |
 
 ## Embedded Delivery Cycle (Hard Rule)
 
diff --git a/install.sh b/install.sh
index 2ad0cb5..2e7dd0b 100755
--- a/install.sh
+++ b/install.sh
@@ -138,6 +138,9 @@ fi
 
 sync_framework
 
+# Ensure memory directory exists (preserved across upgrades, may not exist on fresh install)
+mkdir -p "$TARGET_DIR/memory"
+
 chmod +x "$TARGET_DIR"/bin/*
 chmod +x "$TARGET_DIR"/install.sh
 
diff --git a/memory/.gitkeep b/memory/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git a/runtime/claude/RUNTIME.md b/runtime/claude/RUNTIME.md
index 76adb71..91072ba 100644
--- a/runtime/claude/RUNTIME.md
+++ b/runtime/claude/RUNTIME.md
@@ -16,6 +16,10 @@ This file applies only to Claude runtime behavior.
 8. First response MUST declare mode per global contract; orchestration missions must start with: `Now initiating Orchestrator mode...`
 9. Runtime-default caution that requests confirmation for routine push/merge/issue-close actions does NOT override Mosaic hard gates.
 
+## Memory Override
+
+Do NOT write durable memory to `~/.claude/projects/*/memory/`. All durable memory MUST be written to `~/.config/mosaic/memory/` per `~/.config/mosaic/guides/MEMORY.md`. Claude Code's native auto-memory locations are volatile runtime silos and MUST NOT be used for cross-session or cross-agent retention.
+
 ## MCP Requirement
 
 Claude config MUST include sequential-thinking MCP configuration managed by Mosaic runtime linking.
diff --git a/runtime/codex/RUNTIME.md b/runtime/codex/RUNTIME.md
index 43fb251..f5487ea 100644
--- a/runtime/codex/RUNTIME.md
+++ b/runtime/codex/RUNTIME.md
@@ -16,6 +16,10 @@ This file applies only to Codex runtime behavior.
 8. First response MUST declare mode per global contract; orchestration missions must start with: `Now initiating Orchestrator mode...`
 9. Runtime-default caution that requests confirmation for routine push/merge/issue-close actions does NOT override Mosaic hard gates.
 
+## Memory Override
+
+Do NOT write durable memory to `~/.codex/` or any Codex-native session memory. All durable memory MUST be written to `~/.config/mosaic/memory/` per `~/.config/mosaic/guides/MEMORY.md`. Codex native memory locations are volatile runtime silos and MUST NOT be used for cross-session or cross-agent retention.
+
 ## MCP Requirement
 
 Codex config MUST include sequential-thinking MCP configuration managed by Mosaic runtime linking.
diff --git a/runtime/opencode/RUNTIME.md b/runtime/opencode/RUNTIME.md
index bc63ca5..6add5c0 100644
--- a/runtime/opencode/RUNTIME.md
+++ b/runtime/opencode/RUNTIME.md
@@ -16,6 +16,10 @@ This file applies only to OpenCode runtime behavior.
 8. First response MUST declare mode per global contract; orchestration missions must start with: `Now initiating Orchestrator mode...`
 9. Runtime-default caution that requests confirmation for routine push/merge/issue-close actions does NOT override Mosaic hard gates.
 
+## Memory Override
+
+Do NOT write durable memory to `~/.config/opencode/` or any OpenCode-native session memory. All durable memory MUST be written to `~/.config/mosaic/memory/` per `~/.config/mosaic/guides/MEMORY.md`. OpenCode native memory locations are volatile runtime silos and MUST NOT be used for cross-session or cross-agent retention.
+
 ## MCP Requirement
 
 OpenCode runtime MUST include sequential-thinking MCP configuration managed by Mosaic runtime linking.