diff --git a/packages/mosaic/framework/install.sh b/packages/mosaic/framework/install.sh
index 80cd20a..5083a41 100755
--- a/packages/mosaic/framework/install.sh
+++ b/packages/mosaic/framework/install.sh
@@ -21,11 +21,19 @@ INSTALL_MODE="${MOSAIC_INSTALL_MODE:-prompt}"
 
 # Files/dirs preserved across upgrades (never overwritten).
 # User-created content in these paths survives rsync --delete.
-PRESERVE_PATHS=("AGENTS.md" "SOUL.md" "USER.md" "TOOLS.md" "STANDARDS.md" "memory" "sources" "credentials")
+PRESERVE_PATHS=("CONSTITUTION.md" "AGENTS.md" "SOUL.md" "USER.md" "TOOLS.md" "STANDARDS.md" "memory" "sources" "credentials")
+
+# Framework-owned contract files: re-copied from defaults/ on every upgrade (the
+# user must not edit them; a divergent copy is backed up once before overwrite).
+# USER_SEEDED files are written once on first install, then owned by the user.
+# Both lists are APPEND-FRIENDLY — add a new shipped framework file here and to the
+# matching list in packages/mosaic/src/config/file-adapter.ts.
+FRAMEWORK_OWNED=("CONSTITUTION.md" "AGENTS.md" "STANDARDS.md")
+USER_SEEDED=("TOOLS.md")
 
 # Current framework schema version — bump this when the layout changes.
 # The migration system uses this to run upgrade steps.
-FRAMEWORK_VERSION=2
+FRAMEWORK_VERSION=3
 
 # ─── colours ──────────────────────────────────────────────────────────────────
 if [[ -t 1 ]]; then
@@ -40,6 +48,45 @@ warn() { echo -e "  ${YELLOW}⚠${RESET} $1" >&2; }
 fail() { echo -e "  ${RED}✗${RESET} $1" >&2; }
 step() { echo -e "\n${BOLD}$1${RESET}"; }
 
+# ─── snapshot / restore (crash safety for upgrades) ──────────────────────────
+SNAPSHOT_DIR=""
+make_snapshot() {
+  is_existing_install || return 0
+  SNAPSHOT_DIR="$(mktemp -d "${TMPDIR:-/tmp}/mosaic-snapshot-XXXXXX")"
+  cp -a "$TARGET_DIR/." "$SNAPSHOT_DIR/" 2>/dev/null || true
+}
+restore_snapshot() {
+  [[ -n "$SNAPSHOT_DIR" && -d "$SNAPSHOT_DIR" ]] || return 0
+  fail "Install interrupted/failed — restoring previous state from snapshot"
+  rm -rf "$TARGET_DIR"; mkdir -p "$TARGET_DIR"
+  cp -a "$SNAPSHOT_DIR/." "$TARGET_DIR/" 2>/dev/null || true
+}
+cleanup_snapshot() { [[ -n "$SNAPSHOT_DIR" && -d "$SNAPSHOT_DIR" ]] && rm -rf "$SNAPSHOT_DIR"; SNAPSHOT_DIR=""; }
+
+# Reconcile contract files after sync: framework-owned overwrite (backup-once),
+# user-seeded seed-if-absent.
+reconcile_framework_files() {
+  local defaults="$TARGET_DIR/defaults" f
+  [[ -d "$defaults" ]] || return 0
+  for f in "${FRAMEWORK_OWNED[@]}"; do
+    [[ -f "$defaults/$f" ]] || continue
+    if [[ -f "$TARGET_DIR/$f" ]] && ! cmp -s "$TARGET_DIR/$f" "$defaults/$f"; then
+      if [[ ! -f "$TARGET_DIR/${f}.pre-constitution.bak" ]]; then
+        cp "$TARGET_DIR/$f" "$TARGET_DIR/${f}.pre-constitution.bak"
+        warn "$f is now framework-owned and was updated; your previous copy is saved as ${f}.pre-constitution.bak — re-apply intended changes as a .local overlay or policy/ file (see CONSTITUTION.md / constitution/LAYER-MODEL.md)."
+      fi
+    fi
+    cp "$defaults/$f" "$TARGET_DIR/$f"
+  done
+  for f in "${USER_SEEDED[@]}"; do
+    [[ -f "$defaults/$f" ]] || continue
+    if [[ ! -f "$TARGET_DIR/$f" ]]; then
+      cp "$defaults/$f" "$TARGET_DIR/$f"
+      ok "Seeded $f from defaults"
+    fi
+  done
+}
+
 # ─── helpers ──────────────────────────────────────────────────────────────────
 
 is_existing_install() {
@@ -113,11 +160,14 @@ sync_framework() {
   fi
 
   if command -v rsync >/dev/null 2>&1; then
-    local rsync_args=(-a --delete --exclude ".git" --exclude ".framework-version")
+    local rsync_args=(-a --delete --exclude ".git" --exclude ".framework-version" --exclude "*.pre-constitution.bak")
 
     if [[ "$INSTALL_MODE" == "keep" ]]; then
+      # Anchor to the transfer root (leading /) so we preserve the TOP-LEVEL
+      # ~/.config/mosaic/<file> without also excluding defaults/<file> from sync
+      # (reconcile_framework_files needs the freshly-synced defaults/ copies).
       for path in "${PRESERVE_PATHS[@]}"; do
-        rsync_args+=(--exclude "$path")
+        rsync_args+=(--exclude "/$path")
       done
     fi
 
@@ -137,7 +187,7 @@ sync_framework() {
     done
   fi
 
-  find "$TARGET_DIR" -mindepth 1 -maxdepth 1 ! -name ".git" ! -name ".framework-version" -exec rm -rf {} +
+  find "$TARGET_DIR" -mindepth 1 -maxdepth 1 ! -name ".git" ! -name ".framework-version" ! -name "*.pre-constitution.bak" -exec rm -rf {} +
   cp -R "$SOURCE_DIR"/. "$TARGET_DIR"/
   rm -rf "$TARGET_DIR/.git"
 
@@ -195,10 +245,15 @@ run_migrations() {
     fi
   fi
 
-  # ── Future migrations go here ──────────────────────────────────────────────
-  # if [[ "$from_version" -lt 3 ]]; then
-  #   ...
-  # fi
+  # ── Migration: v2 → v3 (Constitution split) ───────────────────────────────
+  # CONSTITUTION.md / AGENTS.md / STANDARDS.md become framework-owned (overwritten
+  # on upgrade). reconcile_framework_files() has already run before this point: it
+  # backed up any user-edited copy to <file>.pre-constitution.bak and installed the
+  # new framework version. Nothing further to do here — the advisory was emitted at
+  # reconcile time. (STANDARDS.local.md composition lands with the overlay composer.)
+  if [[ "$from_version" -lt 3 ]]; then
+    ok "Migrated to the Constitution layout (framework-owned CONSTITUTION/AGENTS/STANDARDS)"
+  fi
 }
 
 # ═══════════════════════════════════════════════════════════════════════════════
@@ -216,6 +271,10 @@ else
   ok "Install mode: overwrite"
 fi
 
+# Snapshot before any destructive file operation; restore on interrupt/failure.
+make_snapshot
+trap 'restore_snapshot' ERR INT TERM
+
 sync_framework
 
 # Ensure persistent directories exist
@@ -230,15 +289,7 @@ mkdir -p "$TARGET_DIR/credentials"
 # packages/mosaic/src/config/file-adapter.ts (FileConfigAdapter.syncFramework).
 # SOUL.md and USER.md are intentionally NOT seeded here — they are generated
 # by `mosaic init` from templates with user-supplied values.
-DEFAULTS_DIR="$TARGET_DIR/defaults"
-if [[ -d "$DEFAULTS_DIR" ]]; then
-  for default_file in CONSTITUTION.md AGENTS.md STANDARDS.md TOOLS.md; do
-    if [[ -f "$DEFAULTS_DIR/$default_file" ]] && [[ ! -f "$TARGET_DIR/$default_file" ]]; then
-      cp "$DEFAULTS_DIR/$default_file" "$TARGET_DIR/$default_file"
-      ok "Seeded $default_file from defaults"
-    fi
-  done
-fi
+reconcile_framework_files
 
 # Ensure tool scripts are executable
 find "$TARGET_DIR/tools" -name "*.sh" -exec chmod +x {} + 2>/dev/null || true
@@ -249,6 +300,18 @@ ok "Framework synced to $TARGET_DIR"
 # Run migrations before post-install (migrations may remove old bin/ etc.)
 run_migrations
 
+# File-system phase complete and consistent — clear the restore trap.
+trap - ERR INT TERM
+cleanup_snapshot
+
+# Testability / minimal-install hook: stop after the file-system phase, before any
+# environment-touching post-install steps (runtime linking, MCP setup, skills, doctor).
+if [[ "${MOSAIC_SYNC_ONLY:-0}" == "1" ]]; then
+  write_framework_version
+  ok "Sync-only mode: file phase complete"
+  exit 0
+fi
+
 step "Post-install tasks"
 
 SCRIPTS="$TARGET_DIR/tools/_scripts"
diff --git a/packages/mosaic/framework/tools/_scripts/mosaic-init b/packages/mosaic/framework/tools/_scripts/mosaic-init
index 57704c9..08830f9 100755
--- a/packages/mosaic/framework/tools/_scripts/mosaic-init
+++ b/packages/mosaic/framework/tools/_scripts/mosaic-init
@@ -274,6 +274,13 @@ detect_existing_config
 echo "[mosaic-init] Generating SOUL.md — agent identity contract"
 echo ""
 
+# Fail-closed persona: in non-interactive mode the agent NAME must be supplied
+# explicitly (--name) — never silently ship an agent named "Assistant".
+if [[ $NON_INTERACTIVE -eq 1 && -z "$AGENT_NAME" ]]; then
+  echo "[mosaic-init] ERROR: --name (agent name) is required in non-interactive mode." >&2
+  exit 1
+fi
+
 prompt_if_empty AGENT_NAME "What name should agents use" "Assistant"
 prompt_if_empty ROLE_DESCRIPTION "Agent role description" "execution partner and visibility engine"
 
diff --git a/packages/mosaic/framework/tools/quality/scripts/test-install-migration.sh b/packages/mosaic/framework/tools/quality/scripts/test-install-migration.sh
new file mode 100755
index 0000000..9b8647a
--- /dev/null
+++ b/packages/mosaic/framework/tools/quality/scripts/test-install-migration.sh
@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+# test-install-migration.sh — fixture matrix for the v2→v3 (Constitution) upgrade
+# migration in install.sh. Runs the installer against throwaway MOSAIC_HOME dirs
+# with MOSAIC_SYNC_ONLY=1 (file phase only — no environment-touching post-install)
+# and asserts the framework-owned-overwrite + user-preserve + backup semantics.
+#
+# Mirrors the TS fixture suite in packages/mosaic/src/config/file-adapter.test.ts;
+# both installers MUST behave identically.
+#
+# Usage:  bash test-install-migration.sh
+set -uo pipefail
+
+FW="$(cd "$(dirname "${BASH_SOURCE[0]}")/../../.." && pwd)"   # packages/mosaic/framework
+INSTALL="$FW/install.sh"
+DEFA="$FW/defaults"
+
+pass=0; fail=0
+chk() { if eval "$2"; then echo "  ✓ $1"; pass=$((pass + 1)); else echo "  ✗ $1"; fail=$((fail + 1)); fi; }
+run() { MOSAIC_HOME="$1" MOSAIC_INSTALL_MODE="$2" MOSAIC_SYNC_ONLY=1 bash "$INSTALL" >/dev/null 2>&1; }
+
+echo "install.sh v2→v3 migration fixture matrix:"
+
+# F1 — fresh install
+T1=$(mktemp -d); run "$T1" overwrite
+chk "F1 fresh: CONSTITUTION/AGENTS/STANDARDS/TOOLS seeded" \
+  "[ -f '$T1/CONSTITUTION.md' ] && [ -f '$T1/AGENTS.md' ] && [ -f '$T1/STANDARDS.md' ] && [ -f '$T1/TOOLS.md' ]"
+chk "F1 fresh: AGENTS == shipped default" "cmp -s '$T1/AGENTS.md' '$DEFA/AGENTS.md'"
+chk "F1 fresh: framework-version stamped 3" "[ \"\$(cat '$T1/.framework-version' 2>/dev/null)\" = 3 ]"
+
+# F2 — legacy install with a user-edited AGENTS.md (the sanctioned pre-constitution customization)
+T2=$(mktemp -d); mkdir -p "$T2/credentials"
+printf '# user-edited AGENTS pre-constitution\n' > "$T2/AGENTS.md"
+printf '# my persona\n' > "$T2/SOUL.md"
+printf 'token\n' > "$T2/credentials/c.json"
+echo 2 > "$T2/.framework-version"
+run "$T2" keep
+chk "F2 legacy-edited: AGENTS overwritten to framework version" "cmp -s '$T2/AGENTS.md' '$DEFA/AGENTS.md'"
+chk "F2 legacy-edited: prior AGENTS saved to .pre-constitution.bak" \
+  "grep -q 'user-edited AGENTS pre-constitution' '$T2/AGENTS.md.pre-constitution.bak'"
+chk "F2 legacy-edited: SOUL.md preserved" "grep -q 'my persona' '$T2/SOUL.md'"
+chk "F2 legacy-edited: credentials preserved" "grep -q token '$T2/credentials/c.json'"
+chk "F2 legacy-edited: CONSTITUTION.md installed" "[ -f '$T2/CONSTITUTION.md' ]"
+run "$T2" keep
+chk "F2 idempotent: .pre-constitution.bak preserved across a 2nd upgrade" \
+  "grep -q 'user-edited AGENTS pre-constitution' '$T2/AGENTS.md.pre-constitution.bak'"
+
+# F3 — user-tuned STANDARDS.md
+T3=$(mktemp -d); printf '# tuned standards\n' > "$T3/STANDARDS.md"; printf '# persona\n' > "$T3/SOUL.md"; echo 2 > "$T3/.framework-version"
+run "$T3" keep
+chk "F3 tuned-standard: STANDARDS overwritten" "cmp -s '$T3/STANDARDS.md' '$DEFA/STANDARDS.md'"
+chk "F3 tuned-standard: tuned copy backed up" "grep -q 'tuned standards' '$T3/STANDARDS.md.pre-constitution.bak'"
+
+# F4 — unattended / no TTY (stdin closed): must complete without hanging, default to keep
+T4=$(mktemp -d); printf '# persona\n' > "$T4/SOUL.md"; printf '# old\n' > "$T4/AGENTS.md"; echo 2 > "$T4/.framework-version"
+MOSAIC_HOME="$T4" MOSAIC_SYNC_ONLY=1 bash "$INSTALL" </dev/null >/dev/null 2>&1
+chk "F4 no-TTY: completed, AGENTS updated" "cmp -s '$T4/AGENTS.md' '$DEFA/AGENTS.md'"
+
+# F5 — failure path must not corrupt existing data (invalid mode rejected before any file op)
+T5=$(mktemp -d); mkdir -p "$T5/credentials"; printf '# orig\n' > "$T5/SOUL.md"; printf 'keepme\n' > "$T5/credentials/c.json"; echo 2 > "$T5/.framework-version"
+MOSAIC_HOME="$T5" MOSAIC_INSTALL_MODE=bogus MOSAIC_SYNC_ONLY=1 bash "$INSTALL" >/dev/null 2>&1; rc=$?
+chk "F5 failure: invalid mode rejected (nonzero exit)" "[ $rc -ne 0 ]"
+chk "F5 failure: SOUL + credentials intact" "grep -q orig '$T5/SOUL.md' && grep -q keepme '$T5/credentials/c.json'"
+
+rm -rf "$T1" "$T2" "$T3" "$T4" "$T5"
+echo
+echo "RESULT: $pass passed, $fail failed"
+[ "$fail" -eq 0 ]
diff --git a/packages/mosaic/framework/tools/quality/scripts/verify-sanitized.sh b/packages/mosaic/framework/tools/quality/scripts/verify-sanitized.sh
index 4324f8e..9de53c7 100755
--- a/packages/mosaic/framework/tools/quality/scripts/verify-sanitized.sh
+++ b/packages/mosaic/framework/tools/quality/scripts/verify-sanitized.sh
@@ -53,9 +53,15 @@ _selftest() {
   local tmp; tmp="$(mktemp -d)" || return 1
   printf 'contact jason.woltje at jarvis-brain (PDA-friendly)\n' > "$tmp/planted.md"
   printf 'X="${VAR:-$HOME/src/whatever/x.json}"\n' > "$tmp/planted.sh"
+  printf 'name: jason-woltje\n' > "$tmp/planted.yaml"
+  printf '[Service]\nUser=jarvis\n' > "$tmp/planted.service"
   local rc=0
   grep -qIEi "$DENYLIST" "$tmp/planted.md" || { echo "✗ SELF-TEST: identity denylist regex broken" >&2; rc=1; }
   grep -qIE  "$STRUCTURAL_SH" "$tmp/planted.sh" || { echo "✗ SELF-TEST: structural regex broken" >&2; rc=1; }
+  # Prove the identity scan covers the config formats it claims to (yaml/service/etc).
+  local n_ext
+  n_ext=$(find "$tmp" -type f \( -name '*.yaml' -o -name '*.service' \) -print0 | xargs -0 -r grep -lIEi "$DENYLIST" 2>/dev/null | wc -l)
+  [[ "$n_ext" -eq 2 ]] || { echo "✗ SELF-TEST: identity scan does not cover .yaml/.service extensions" >&2; rc=1; }
   rm -rf "$tmp"; return $rc
 }
 _selftest || exit 2
diff --git a/packages/mosaic/src/config/file-adapter.test.ts b/packages/mosaic/src/config/file-adapter.test.ts
index 48f411a..b8629d7 100644
--- a/packages/mosaic/src/config/file-adapter.test.ts
+++ b/packages/mosaic/src/config/file-adapter.test.ts
@@ -99,11 +99,8 @@ describe('FileConfigAdapter.syncFramework — defaults seeding', () => {
     );
   });
 
-  it('preserves existing contract files — never overwrites user customization', async () => {
-    // Also plant a root-level AGENTS.md in sourceDir so that `syncDirectory`
-    // itself (not just the seed loop) has something to try to overwrite.
-    // Without this, the test would silently pass even if preserve semantics
-    // were broken in syncDirectory.
+  it('overwrites framework-owned files (backup-once) but preserves user-seeded files', async () => {
+    // Plant a root-level AGENTS.md in sourceDir so syncDirectory's preserve is exercised.
     writeFileSync(join(fixture.sourceDir, 'AGENTS.md'), '# shipped AGENTS from source root\n');
 
     writeFileSync(join(fixture.mosaicHome, 'TOOLS.md'), '# user-customized TOOLS\n');
@@ -112,18 +109,50 @@ describe('FileConfigAdapter.syncFramework — defaults seeding', () => {
     const adapter = new FileConfigAdapter(fixture.mosaicHome, fixture.sourceDir);
     await adapter.syncFramework('keep');
 
+    // User-seeded TOOLS.md is preserved.
     expect(readFileSync(join(fixture.mosaicHome, 'TOOLS.md'), 'utf-8')).toBe(
       '# user-customized TOOLS\n',
     );
-    expect(readFileSync(join(fixture.mosaicHome, 'AGENTS.md'), 'utf-8')).toBe(
+    // Framework-owned AGENTS.md is overwritten from defaults/ ...
+    expect(readFileSync(join(fixture.mosaicHome, 'AGENTS.md'), 'utf-8')).toBe('# AGENTS default\n');
+    // ... and the user's prior copy is backed up exactly once.
+    expect(readFileSync(join(fixture.mosaicHome, 'AGENTS.md.pre-constitution.bak'), 'utf-8')).toBe(
       '# user-customized AGENTS\n',
     );
-    // And the missing contract file still gets seeded.
+    // Framework-owned STANDARDS.md (absent) gets installed.
     expect(readFileSync(join(fixture.mosaicHome, 'STANDARDS.md'), 'utf-8')).toContain(
       '# STANDARDS default',
     );
   });
 
+  it('backs up a divergent framework-owned file only once (idempotent across re-sync)', async () => {
+    writeFileSync(join(fixture.mosaicHome, 'AGENTS.md'), '# user-customized AGENTS\n');
+    const adapter = new FileConfigAdapter(fixture.mosaicHome, fixture.sourceDir);
+
+    await adapter.syncFramework('keep'); // 1st: backup created, AGENTS overwritten
+    await adapter.syncFramework('keep'); // 2nd: AGENTS already == default, no new backup
+
+    expect(readFileSync(join(fixture.mosaicHome, 'AGENTS.md.pre-constitution.bak'), 'utf-8')).toBe(
+      '# user-customized AGENTS\n',
+    );
+  });
+
+  it('preserves SOUL.md and credentials through a framework-owned overwrite', async () => {
+    writeFileSync(join(fixture.mosaicHome, 'SOUL.md'), '# my persona\n');
+    writeFileSync(join(fixture.mosaicHome, 'AGENTS.md'), '# user-customized AGENTS\n');
+    mkdirSync(join(fixture.mosaicHome, 'credentials'), { recursive: true });
+    writeFileSync(join(fixture.mosaicHome, 'credentials', 'c.json'), 'token\n');
+
+    const adapter = new FileConfigAdapter(fixture.mosaicHome, fixture.sourceDir);
+    await adapter.syncFramework('keep');
+
+    expect(readFileSync(join(fixture.mosaicHome, 'SOUL.md'), 'utf-8')).toBe('# my persona\n');
+    expect(readFileSync(join(fixture.mosaicHome, 'credentials', 'c.json'), 'utf-8')).toBe(
+      'token\n',
+    );
+    expect(readFileSync(join(fixture.mosaicHome, 'AGENTS.md'), 'utf-8')).toBe('# AGENTS default\n');
+  });
+
   it('is a no-op for seeding when defaults/ dir does not exist', async () => {
     rmSync(fixture.defaultsDir, { recursive: true });
 
diff --git a/packages/mosaic/src/config/file-adapter.ts b/packages/mosaic/src/config/file-adapter.ts
index 3b6cd9c..ea92f6d 100644
--- a/packages/mosaic/src/config/file-adapter.ts
+++ b/packages/mosaic/src/config/file-adapter.ts
@@ -13,12 +13,17 @@ import { join } from 'node:path';
  * This list must match the explicit seed loop in
  * packages/mosaic/framework/install.sh.
  */
-export const DEFAULT_SEED_FILES = [
-  'CONSTITUTION.md',
-  'AGENTS.md',
-  'STANDARDS.md',
-  'TOOLS.md',
-] as const;
+// Framework-owned contract files: re-copied from defaults/ on every upgrade (a
+// divergent existing copy is backed up once to <file>.pre-constitution.bak first).
+// MUST match FRAMEWORK_OWNED in packages/mosaic/framework/install.sh (append-friendly).
+export const FRAMEWORK_OWNED_FILES = ['CONSTITUTION.md', 'AGENTS.md', 'STANDARDS.md'] as const;
+
+// User-seeded contract files: written once on first install, then owned by the user.
+// MUST match USER_SEEDED in packages/mosaic/framework/install.sh.
+export const USER_SEEDED_FILES = ['TOOLS.md'] as const;
+
+// Union, retained for callers/tests that assert the full seed set on a fresh install.
+export const DEFAULT_SEED_FILES = [...FRAMEWORK_OWNED_FILES, ...USER_SEEDED_FILES] as const;
 import type { ConfigService, ConfigSection, ResolvedConfig } from './config-service.js';
 import type { SoulConfig, UserConfig, ToolsConfig, InstallAction } from '../types.js';
 import { soulSchema, userSchema, toolsSchema } from './schemas.js';
@@ -159,6 +164,7 @@ export class FileConfigAdapter implements ConfigService {
     const preservePaths =
       action === 'keep' || action === 'reconfigure'
         ? [
+            'CONSTITUTION.md',
             'AGENTS.md',
             'SOUL.md',
             'USER.md',
@@ -175,10 +181,10 @@ export class FileConfigAdapter implements ConfigService {
       excludeGit: true,
     });
 
-    // Copy framework-contract files (AGENTS.md, STANDARDS.md, TOOLS.md)
-    // from framework/defaults/ into the mosaic home root if they don't
-    // exist yet. These are written on first install only and are never
-    // overwritten afterwards — the user may have customized them.
+    // Reconcile framework-contract files from framework/defaults/ into the mosaic
+    // home root: framework-owned files (CONSTITUTION/AGENTS/STANDARDS) are overwritten
+    // every upgrade (backup-once); user-seeded files (TOOLS) are written on first
+    // install only. Mirrors reconcile_framework_files() in install.sh.
     //
     // SOUL.md and USER.md are deliberately NOT seeded here. They are
     // generated from templates by the soul/user wizard stages with
@@ -186,7 +192,20 @@ export class FileConfigAdapter implements ConfigService {
     // identity flow and leak placeholder content into the mosaic home.
     const defaultsDir = join(this.sourceDir, 'defaults');
     if (existsSync(defaultsDir)) {
-      for (const entry of DEFAULT_SEED_FILES) {
+      // Framework-owned: overwrite from defaults/ every sync; back up a divergent
+      // existing copy ONCE to <file>.pre-constitution.bak before the first overwrite.
+      for (const entry of FRAMEWORK_OWNED_FILES) {
+        const src = join(defaultsDir, entry);
+        const dest = join(this.mosaicHome, entry);
+        if (!existsSync(src) || !statSync(src).isFile()) continue;
+        const bak = `${dest}.pre-constitution.bak`;
+        if (existsSync(dest) && !readFileSync(src).equals(readFileSync(dest)) && !existsSync(bak)) {
+          copyFileSync(dest, bak);
+        }
+        copyFileSync(src, dest);
+      }
+      // User-seeded: write only if absent.
+      for (const entry of USER_SEEDED_FILES) {
         const src = join(defaultsDir, entry);
         const dest = join(this.mosaicHome, entry);
         if (existsSync(dest)) continue;