fix(lease): restore uniform settings array replacement

AMD1213-B1: preserve the gated Claude hook composition explicitly in the lease overlay while restoring last-layer-wins arrays and null tombstones.

packages/mosaic/framework/runtime/claude/lease-overlay.json

@@ -44,6 +44,16 @@
       }
     ],
     "PreToolUse": [
+      {
+        "matcher": "Write|Edit|MultiEdit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.config/mosaic/tools/qa/prevent-memory-write.sh",
+            "timeout": 10
+          }
+        ]
+      },
       {
         "matcher": ".*",
         "hooks": [
@@ -56,6 +66,15 @@
       }
     ],
     "Stop": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "~/.config/mosaic/tools/qa/reflect-stop-hook.sh",
+            "timeout": 15
+          }
+        ]
+      },
       {
         "hooks": [
           {

packages/mosaic/src/commands/fleet-launch-command.spec.ts

@@ -94,7 +94,7 @@ describe('three-layer settings merge', () => {
     ).toEqual({ nested: { keep: true } });
   });
 
-  it('concatenates hook event arrays so an overlay adds gating without erasing base hooks', () => {
+  it('replaces a hook event array wholesale with the higher layer', () => {
     const qaStop = { hooks: [{ type: 'command', command: 'qa-stop.sh' }] };
     const leaseStop = { hooks: [{ type: 'command', command: 'receipt-observer.py' }] };
     const qaPre = { matcher: 'Write', hooks: [{ type: 'command', command: 'qa-pre.sh' }] };
@@ -103,7 +103,140 @@ describe('three-layer settings merge', () => {
         { hooks: { Stop: [qaStop], PreToolUse: [qaPre] } },
         { hooks: { Stop: [leaseStop] } },
       ),
-    ).toEqual({ hooks: { Stop: [qaStop, leaseStop], PreToolUse: [qaPre] } });
+    ).toEqual({ hooks: { Stop: [leaseStop], PreToolUse: [qaPre] } });
+  });
+
+  it('reconstructs every gated hook event from the base and lease overlay', () => {
+    const fx = fixture({ schema: 1, harness: 'claude', overlay: 'lease-overlay.json' });
+    const frameworkRuntime = join(process.cwd(), 'framework', 'runtime', 'claude');
+    writeFileSync(
+      join(fx.systemHome, 'runtime', 'claude', 'settings.json'),
+      readFileSync(join(frameworkRuntime, 'settings.json'), 'utf8'),
+    );
+    writeFileSync(
+      join(fx.agentDir, 'lease-overlay.json'),
+      readFileSync(join(frameworkRuntime, 'lease-overlay.json'), 'utf8'),
+    );
+
+    const plan = resolveFleetLaunchComposition('fred', {
+      systemHome: fx.systemHome,
+      userHome: fx.userHome,
+    });
+
+    expect(plan.settings.merged['hooks']).toEqual({
+      PreToolUse: [
+        {
+          matcher: 'Write|Edit|MultiEdit',
+          hooks: [
+            {
+              type: 'command',
+              command: '~/.config/mosaic/tools/qa/prevent-memory-write.sh',
+              timeout: 10,
+            },
+          ],
+        },
+        {
+          matcher: '.*',
+          hooks: [
+            {
+              type: 'command',
+              command:
+                'python3 ~/.config/mosaic/tools/lease-broker/mutator-gate.py --runtime claude --recovery-command ~/.config/mosaic/tools/lease-broker/recover-context.py',
+              timeout: 3,
+            },
+          ],
+        },
+      ],
+      PostToolUse: [
+        {
+          matcher: 'Edit|MultiEdit|Write',
+          hooks: [
+            {
+              type: 'command',
+              command: '~/.config/mosaic/tools/qa/qa-hook-stdin.sh',
+              timeout: 60,
+            },
+          ],
+        },
+        {
+          matcher: 'Edit|MultiEdit|Write',
+          hooks: [
+            {
+              type: 'command',
+              command: '~/.config/mosaic/tools/qa/typecheck-hook.sh',
+              timeout: 30,
+            },
+          ],
+        },
+      ],
+      Stop: [
+        {
+          hooks: [
+            {
+              type: 'command',
+              command: '~/.config/mosaic/tools/qa/reflect-stop-hook.sh',
+              timeout: 15,
+            },
+          ],
+        },
+        {
+          hooks: [
+            {
+              type: 'command',
+              command:
+                'python3 ~/.config/mosaic/tools/lease-broker/receipt-observer-client.py --runtime claude --latest-entry; observer_status=$?; python3 ~/.config/mosaic/tools/lease-broker/promote-complete.py; exit $observer_status',
+              timeout: 15,
+            },
+          ],
+        },
+      ],
+      PreCompact: [
+        {
+          matcher: '.*',
+          hooks: [
+            {
+              type: 'command',
+              command:
+                'python3 "$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py" --runtime claude --reason pre-compact',
+            },
+          ],
+        },
+      ],
+      SessionStart: [
+        {
+          matcher: 'compact',
+          hooks: [
+            {
+              type: 'command',
+              command:
+                'python3 "$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py" --runtime claude --reason session-start-compact',
+            },
+          ],
+        },
+        {
+          matcher: 'resume|clear',
+          hooks: [
+            {
+              type: 'command',
+              command:
+                'python3 "$HOME/.config/mosaic/tools/lease-broker/revoke-lease.py" --runtime claude --reason session-start-rollover --bump-generation',
+            },
+          ],
+        },
+      ],
+      UserPromptSubmit: [
+        {
+          matcher: '^/mosaic-promote$',
+          hooks: [
+            {
+              type: 'command',
+              command: 'python3 ~/.config/mosaic/tools/lease-broker/promote-begin.py',
+              timeout: 15,
+            },
+          ],
+        },
+      ],
+    });
   });
 
   it('still deletes a whole hook event via the null tombstone', () => {
@@ -115,13 +248,13 @@ describe('three-layer settings merge', () => {
     ).toEqual({ hooks: {} });
   });
 
-  it('keeps replace semantics for arrays outside the top-level hooks object', () => {
+  it('replaces an allowedCommands-shaped non-hook array wholesale', () => {
     expect(
       deepMergeSettings(
-        { plugins: ['base'], nested: { hooks: { Stop: ['base'] } } },
+        { allowedCommands: ['pnpm', 'git'], nested: { hooks: { Stop: ['base'] } } },
-        { plugins: ['user'], nested: { hooks: { Stop: ['user'] } } },
+        { allowedCommands: ['node'], nested: { hooks: { Stop: ['user'] } } },
       ),
-    ).toEqual({ plugins: ['user'], nested: { hooks: { Stop: ['user'] } } });
+    ).toEqual({ allowedCommands: ['node'], nested: { hooks: { Stop: ['user'] } } });
   });
 
   it('deep-merges all three layers in precedence order', () => {

packages/mosaic/src/commands/fleet-launch-command.ts

@@ -253,12 +253,9 @@ function cloneValue(value: unknown): unknown {
   return value;
 }
 
-type MergeContext = 'root' | 'hooks' | 'nested';
-
 function mergeObject(
   lower: Record<string, unknown>,
   higher: Record<string, unknown>,
-  context: MergeContext = 'nested',
 ): Record<string, unknown> {
   const result = cloneValue(lower) as Record<string, unknown>;
   for (const [key, highValue] of Object.entries(higher)) {
@@ -267,36 +264,23 @@ function mergeObject(
       continue;
     }
     const lowValue = result[key];
-    if (context === 'hooks' && Array.isArray(lowValue) && Array.isArray(highValue)) {
-      result[key] = [...(lowValue as unknown[]), ...(cloneValue(highValue) as unknown[])];
-      continue;
-    }
     result[key] =
       isPlainObject(lowValue) && isPlainObject(highValue)
-        ? mergeObject(
+        ? mergeObject(lowValue, highValue)
-            lowValue,
-            highValue,
-            context === 'root' && key === 'hooks' ? 'hooks' : 'nested',
-          )
         : cloneValue(highValue);
   }
   return result;
 }
 
 /**
- * Deep object merge. Scalars and arrays replace; null in a higher layer
+ * Deep object merge. Objects merge recursively; scalar and array conflicts
- * deletes. Exception: hook event arrays directly under the top-level `hooks`
+ * resolve last-layer-wins; null in a higher layer deletes the key.
- * key concatenate (base entries first), so an overlay ADDS gating without
- * erasing the base QA hooks that share an event — replacing them would make
- * the gap-7 base/overlay split unimplementable without duplicating base
- * hooks inside the lease overlay. Removing an event entirely still works via
- * the null tombstone.
  */
 export function deepMergeSettings(
   ...layers: ReadonlyArray<Record<string, unknown> | undefined>
 ): Record<string, unknown> {
   return layers.reduce<Record<string, unknown>>(
-    (merged, layer) => (layer === undefined ? merged : mergeObject(merged, layer, 'root')),
+    (merged, layer) => (layer === undefined ? merged : mergeObject(merged, layer)),
     {},
   );
 }