diff --git a/DESIGN_SPEC.md b/DESIGN_SPEC.md
index 65b388c3b7..4e6f860143 100644
--- a/DESIGN_SPEC.md
+++ b/DESIGN_SPEC.md
@@ -2149,45 +2149,81 @@ The human can interact as:
 Templates are YAML/JSON files defining a complete company setup:
 
 ```yaml
-# templates/startup.yaml
+# templates/startup.yaml (simplified — real templates also declare
+# variables, departments, min_agents/max_agents, and tags)
 template:
   name: "Tech Startup"
   description: "Small team for building MVPs and prototypes"
   version: "1.0"
 
   company:
-    name: "{{ company_name }}"
     type: "startup"
     budget_monthly: "{{ budget | default(50.00) }}"
-    autonomy: "semi"
+    autonomy: 0.5
 
   agents:
-    - role: "ceo"
+    - role: "CEO"
       name: "{{ ceo_name | auto }}"
       model: "large"
       personality_preset: "visionary_leader"
 
-    - role: "full_stack_developer"
+    - role: "Full-Stack Developer"
+      merge_id: "fullstack-senior"
       name: "{{ dev1_name | auto }}"
       level: "senior"
       model: "medium"
       personality_preset: "pragmatic_builder"
 
-    - role: "full_stack_developer"
+    - role: "Full-Stack Developer"
+      merge_id: "fullstack-mid"
       name: "{{ dev2_name | auto }}"
       level: "mid"
       model: "small"
       personality_preset: "eager_learner"
 
-    - role: "product_manager"
+    - role: "Product Manager"
       name: "{{ pm_name | auto }}"
       model: "medium"
       personality_preset: "strategic_planner"
 
   workflow: "agile_kanban"
   communication: "hybrid"
+
+  workflow_handoffs:
+    - from_department: "engineering"
+      to_department: "qa"
+      trigger: "pr_ready"
+
+  escalation_paths:
+    - from_department: "engineering"
+      to_department: "security"
+      condition: "vulnerability_found"
 ```
 
+**Template Inheritance** — Templates can extend other templates using `extends`:
+
+```yaml
+template:
+  name: "Extended Startup"
+  extends: "startup"         # inherits all agents, departments, config
+  agents:
+    - role: "QA Engineer"    # appended to parent agents
+      level: "mid"
+    - role: "Full-Stack Developer"
+      merge_id: "fullstack-mid"
+      department: "engineering"
+      _remove: true          # removes matching parent agent by key
+```
+
+Inheritance resolves parent→child chains up to 10 levels deep. Merge semantics:
+- **Scalars** (`company_name`, `company_type`): child wins if present.
+- **`config`** dict: deep-merged (child keys override parent).
+- **`agents`** list: merged by `(role, department, merge_id)` key. When `merge_id` is omitted, it defaults to an empty string, making the key `(role, department, "")`. Child can override, append, or remove (`_remove: true`) parent agents.
+- **`departments`** list: merged by name (case-insensitive). Child dept replaces parent entirely.
+- **`workflow_handoffs`**, **`escalation_paths`**: child replaces entirely if present.
+
+Circular inheritance is detected via chain tracking and raises `TemplateInheritanceError`.
+
 ### 14.2 Company Builder
 
 Interactive CLI/web wizard for creating custom companies:
@@ -2334,6 +2370,7 @@ ai-company/
 │       │   ├── metrics.py          # TaskCompletionMetrics proxy overhead model
 │       │   ├── react_loop.py       # ReAct loop implementation
 │       │   ├── plan_models.py      # Plan step, plan, and plan-execute config models
+│       │   ├── plan_parsing.py     # Plan response parsing utilities
 │       │   ├── plan_execute_loop.py # Plan-and-Execute loop implementation
 │       │   ├── loop_helpers.py     # Shared stateless helpers for all loop implementations
 │       │   ├── recovery.py         # Crash recovery strategies (RecoveryStrategy protocol)
@@ -2371,6 +2408,7 @@ ai-company/
 │       │   ├── events/             # Per-domain event constants
 │       │   │   ├── __init__.py    # Package marker with usage docs; no re-exports
 │       │   │   ├── budget.py      # BUDGET_* constants
+│       │   │   ├── company.py      # COMPANY_* constants
 │       │   │   ├── communication.py # COMM_* constants
 │       │   │   ├── config.py      # CONFIG_* constants
 │       │   │   ├── correlation.py # CORRELATION_* constants
@@ -2473,6 +2511,7 @@ ai-company/
 │           ├── schema.py           # Template schema models
 │           ├── loader.py           # Template loader
 │           ├── renderer.py         # Template renderer
+│           ├── merge.py            # Template config merging for inheritance
 │           ├── presets.py          # Personality presets + auto-name generation
 │           ├── errors.py           # Template errors
 │           └── builtins/           # Pre-built company templates
@@ -2531,6 +2570,8 @@ These conventions were established during the M0–M2+ review cycle. **Adopted**
 | **State coordination** | Planned (M4) | Centralized single-writer: `TaskEngine` owns all task/project mutations via `asyncio.Queue`. Agents submit requests, engine applies `model_copy(update=...)` sequentially and publishes snapshots. `version: int` field on state models for future optimistic concurrency if multi-process scaling is needed. | Prevents lost updates by design. Trivial in single-threaded asyncio (no locks). Perfect audit trail. Industry consensus: MetaGPT, CrewAI, AutoGen all use prevention-by-design, not conflict resolution. See §6.8 State Coordination table. |
 | **Workspace isolation** | Planned (M4) | Pluggable `WorkspaceIsolationStrategy` protocol. Default: planner + git worktrees. Each agent works in an isolated worktree; sequential merge on completion. Textual conflicts detected by git; semantic conflicts reviewed by agent or human. | Industry standard (Codex, Cursor, Claude Code, VS Code). Maximum parallelism. Leverages mature git infrastructure. See §6.8. |
 | **Graceful shutdown** | Adopted (M3) | Pluggable `ShutdownStrategy` protocol. Default: cooperative with 30s timeout. Agents check shutdown event at turn boundaries. Force-cancel after timeout. `INTERRUPTED` status for force-cancelled tasks. M4/M5: upgrade to checkpoint-and-stop. | Cross-platform (Windows `signal.signal()` fallback). Bounded shutdown time. Mirrors cooperative shutdown in §6.7. |
+| **Template inheritance** | Adopted (M2.5) | `extends` field on `CompanyTemplate` triggers parent resolution at render time. `merge.py` merges configs by field type: scalars (child wins), config dicts (deep merge), agents (by `(role, department)` key with `_remove` support), departments (by name). `_ParentEntry` dataclass tracks merge state. `DEFAULT_MERGE_DEPARTMENT = "engineering"` shared between merge and renderer. Circular chains detected via `frozenset` tracking; max depth = 10. | Enables template composition without copy-paste. Merge-by-key preserves parent order. `_remove` directive enables clean agent removal without workarounds. |
+| **Pydantic alias for YAML directives** | Adopted (M2.5) | `Field(alias="_remove")` in `TemplateAgentConfig` — YAML uses `_remove: true`, Python accesses `agent.remove`. Keeps the YAML-facing name (underscore prefix signals internal directive) separate from the Python attribute name. | Underscore-prefixed YAML keys signal merge directives vs regular fields. Pydantic alias bridges the naming convention gap cleanly. |
 | **Communication foundation** | Adopted (M4) | `MessageBus` protocol with `InMemoryMessageBus` backend (asyncio queues, pull-model `receive()` with shutdown signaling via `asyncio.Event`). `MessageDispatcher` routes to concurrent handlers via `asyncio.TaskGroup` with pre-allocated error collection. `AgentMessenger` per-agent facade auto-fills sender/timestamp/ID; deterministic direct-channel naming `@{sorted_a}:{sorted_b}`. `DeliveryEnvelope` for delivery tracking. `NotBlankStr` validation on all protocol boundary identifiers. | Pull-model avoids callback complexity and enables agents to consume at their own pace. Protocol + backend split enables future persistent/distributed bus implementations. Deterministic DM channel names prevent duplicates. See §5. |
 
 ---
diff --git a/src/ai_company/observability/events/template.py b/src/ai_company/observability/events/template.py
index e0bd50bc16..3d240edfcf 100644
--- a/src/ai_company/observability/events/template.py
+++ b/src/ai_company/observability/events/template.py
@@ -15,3 +15,15 @@
 TEMPLATE_RENDER_VALIDATION_ERROR: Final[str] = "template.render.validation_error"
 TEMPLATE_PERSONALITY_PRESET_UNKNOWN: Final[str] = "template.personality_preset.unknown"
 TEMPLATE_PASS1_FLOAT_FALLBACK: Final[str] = "template.pass1.float_fallback"
+TEMPLATE_INHERIT_RESOLVE_START: Final[str] = "template.inherit.resolve_start"
+TEMPLATE_INHERIT_RESOLVE_SUCCESS: Final[str] = "template.inherit.resolve_success"
+TEMPLATE_INHERIT_CIRCULAR: Final[str] = "template.inherit.circular"
+TEMPLATE_INHERIT_DEPTH_EXCEEDED: Final[str] = "template.inherit.depth_exceeded"
+TEMPLATE_INHERIT_MERGE: Final[str] = "template.inherit.merge"
+TEMPLATE_INHERIT_MERGE_ERROR: Final[str] = "template.inherit.merge_error"
+TEMPLATE_RENDER_TYPE_ERROR: Final[str] = "template.render.type_error"
+TEMPLATE_LOAD_NOT_FOUND: Final[str] = "template.load.not_found"
+TEMPLATE_LOAD_READ_ERROR: Final[str] = "template.load.read_error"
+TEMPLATE_LOAD_PARSE_ERROR: Final[str] = "template.load.parse_error"
+TEMPLATE_LOAD_STRUCTURE_ERROR: Final[str] = "template.load.structure_error"
+TEMPLATE_LOAD_INVALID_NAME: Final[str] = "template.load.invalid_name"
diff --git a/src/ai_company/templates/__init__.py b/src/ai_company/templates/__init__.py
index f47b6e9ab6..f2564ef4e1 100644
--- a/src/ai_company/templates/__init__.py
+++ b/src/ai_company/templates/__init__.py
@@ -16,6 +16,7 @@
     TemplateAgentConfig
     TemplateDepartmentConfig
     TemplateError
+    TemplateInheritanceError
     TemplateNotFoundError
     TemplateRenderError
     TemplateValidationError
@@ -23,6 +24,7 @@
 
 from ai_company.templates.errors import (
     TemplateError,
+    TemplateInheritanceError,
     TemplateNotFoundError,
     TemplateRenderError,
     TemplateValidationError,
@@ -51,6 +53,7 @@
     "TemplateDepartmentConfig",
     "TemplateError",
     "TemplateInfo",
+    "TemplateInheritanceError",
     "TemplateMetadata",
     "TemplateNotFoundError",
     "TemplateRenderError",
diff --git a/src/ai_company/templates/builtins/agency.yaml b/src/ai_company/templates/builtins/agency.yaml
index 2c2ef240e7..d33fa91006 100644
--- a/src/ai_company/templates/builtins/agency.yaml
+++ b/src/ai_company/templates/builtins/agency.yaml
@@ -2,6 +2,8 @@ template:
   name: "Agency"
   description: "Client-focused agency with project management and creative roles"
   version: "1.0.0"
+  min_agents: 10
+  max_agents: 15
   tags:
     - "agency"
     - "client-work"
@@ -23,30 +25,84 @@ template:
 
   departments:
     - name: "operations"
-      budget_percent: 30
+      budget_percent: 20
       head_role: "Project Manager"
     - name: "engineering"
-      budget_percent: 40
+      budget_percent: 35
       head_role: "Full-Stack Developer"
     - name: "design"
-      budget_percent: 30
-      head_role: "UI Designer"
+      budget_percent: 20
+      head_role: "UX Designer"
+    - name: "quality_assurance"
+      budget_percent: 10
+      head_role: "QA Engineer"
+    - name: "creative_marketing"
+      budget_percent: 15
+      head_role: "Brand Strategist"
 
   agents:
     - role: "Project Manager"
       level: "senior"
       model: "medium"
-      personality_preset: "visionary_leader"
+      personality_preset: "process_optimizer"
       department: "operations"
+    - role: "Product Manager"
+      level: "mid"
+      model: "medium"
+      personality_preset: "strategic_planner"
+      department: "operations"
+    - role: "Scrum Master"
+      level: "senior"
+      model: "medium"
+      personality_preset: "process_optimizer"
+      department: "operations"
+    - role: "UX Designer"
+      level: "mid"
+      model: "medium"
+      personality_preset: "user_advocate"
+      department: "design"
     - role: "UI Designer"
       level: "mid"
       model: "medium"
+      personality_preset: "creative_innovator"
       department: "design"
+    - role: "Frontend Developer"
+      level: "mid"
+      model: "small"
+      personality_preset: "creative_innovator"
+      department: "engineering"
+    - role: "Backend Developer"
+      level: "senior"
+      model: "medium"
+      personality_preset: "pragmatic_builder"
+      department: "engineering"
     - role: "Full-Stack Developer"
+      merge_id: "fullstack-senior"
       level: "senior"
       model: "medium"
       personality_preset: "pragmatic_builder"
       department: "engineering"
+    - role: "QA Engineer"
+      level: "mid"
+      model: "small"
+      personality_preset: "quality_guardian"
+      department: "quality_assurance"
+    - role: "Content Writer"
+      level: "mid"
+      model: "small"
+      personality_preset: "technical_communicator"
+      department: "creative_marketing"
+    - role: "Brand Strategist"
+      level: "senior"
+      model: "medium"
+      personality_preset: "growth_hacker"
+      department: "creative_marketing"
+    - role: "Full-Stack Developer"
+      merge_id: "fullstack-mid"
+      level: "mid"
+      model: "small"
+      personality_preset: "eager_learner"
+      department: "engineering"
 
   workflow: "kanban"
   communication: "hybrid"
diff --git a/src/ai_company/templates/builtins/dev_shop.yaml b/src/ai_company/templates/builtins/dev_shop.yaml
index ff90b7b366..0b90087e75 100644
--- a/src/ai_company/templates/builtins/dev_shop.yaml
+++ b/src/ai_company/templates/builtins/dev_shop.yaml
@@ -2,6 +2,8 @@ template:
   name: "Dev Shop"
   description: "Software development focused team with QA and DevOps"
   version: "1.0.0"
+  min_agents: 6
+  max_agents: 10
   tags:
     - "development"
     - "engineering"
@@ -36,28 +38,46 @@ template:
     - role: "Software Architect"
       level: "principal"
       model: "large"
-      personality_preset: "methodical_analyst"
+      personality_preset: "systems_thinker"
       department: "engineering"
     - role: "Backend Developer"
+      merge_id: "backend-senior-1"
       level: "senior"
       model: "medium"
       personality_preset: "pragmatic_builder"
       department: "engineering"
     - role: "Backend Developer"
+      merge_id: "backend-mid"
       level: "mid"
       model: "small"
       personality_preset: "eager_learner"
       department: "engineering"
+    - role: "Frontend Developer"
+      level: "mid"
+      model: "small"
+      personality_preset: "creative_innovator"
+      department: "engineering"
     - role: "QA Lead"
       level: "lead"
       model: "medium"
+      personality_preset: "quality_guardian"
+      department: "quality_assurance"
+    - role: "QA Engineer"
+      level: "mid"
+      model: "small"
       personality_preset: "methodical_analyst"
       department: "quality_assurance"
     - role: "DevOps/SRE Engineer"
       level: "mid"
       model: "medium"
-      personality_preset: "pragmatic_builder"
+      personality_preset: "process_optimizer"
       department: "operations"
+    - role: "Backend Developer"
+      merge_id: "backend-senior-2"
+      level: "senior"
+      model: "medium"
+      personality_preset: "disciplined_executor"
+      department: "engineering"
 
   workflow: "agile_kanban"
   communication: "hybrid"
diff --git a/src/ai_company/templates/builtins/full_company.yaml b/src/ai_company/templates/builtins/full_company.yaml
index bff871ead0..8cfcc234df 100644
--- a/src/ai_company/templates/builtins/full_company.yaml
+++ b/src/ai_company/templates/builtins/full_company.yaml
@@ -2,6 +2,8 @@ template:
   name: "Full Company"
   description: "Enterprise simulation with all departments and full hierarchy"
   version: "1.0.0"
+  min_agents: 1
+  max_agents: 50
   tags:
     - "enterprise"
     - "full-hierarchy"
@@ -15,6 +17,14 @@ template:
       description: "Monthly budget in USD"
       var_type: "float"
       default: 200.0
+    - name: "num_backend_devs"
+      description: "Number of backend developers"
+      var_type: "int"
+      default: 3
+    - name: "num_frontend_devs"
+      description: "Number of frontend developers"
+      var_type: "int"
+      default: 2
 
   company:
     type: "full_company"
@@ -23,22 +33,35 @@ template:
 
   departments:
     - name: "executive"
-      budget_percent: 15
+      budget_percent: 10
       head_role: "CEO"
     - name: "engineering"
-      budget_percent: 50
+      budget_percent: 30
       head_role: "CTO"
     - name: "product"
-      budget_percent: 15
+      budget_percent: 10
       head_role: "Product Manager"
+    - name: "design"
+      budget_percent: 8
+      head_role: "UX Designer"
     - name: "quality_assurance"
       budget_percent: 10
-      head_role: "QA Engineer"
+      head_role: "QA Lead"
+    - name: "data_analytics"
+      budget_percent: 8
+      head_role: "Data Analyst"
     - name: "operations"
-      budget_percent: 10
-      head_role: "CFO"
+      budget_percent: 8
+      head_role: "COO"
+    - name: "security"
+      budget_percent: 8
+      head_role: "Security Engineer"
+    - name: "creative_marketing"
+      budget_percent: 8
+      head_role: "Brand Strategist"
 
   agents:
+    # C-Suite (5)
     - role: "CEO"
       level: "c_suite"
       model: "large"
@@ -47,22 +70,151 @@ template:
     - role: "CTO"
       level: "c_suite"
       model: "large"
-      personality_preset: "methodical_analyst"
+      personality_preset: "systems_thinker"
       department: "executive"
     - role: "CFO"
       level: "c_suite"
       model: "large"
+      personality_preset: "data_driven_optimizer"
+      department: "executive"
+    - role: "COO"
+      level: "c_suite"
+      model: "large"
+      personality_preset: "process_optimizer"
       department: "operations"
+    - role: "CPO"
+      level: "c_suite"
+      model: "large"
+      personality_preset: "user_advocate"
+      department: "product"
+    # Product (2)
+    - role: "Product Manager"
+      level: "senior"
+      model: "medium"
+      personality_preset: "strategic_planner"
+      department: "product"
+    - role: "Technical Writer"
+      level: "mid"
+      model: "small"
+      personality_preset: "technical_communicator"
+      department: "product"
+    # Design (2)
+    - role: "UX Designer"
+      level: "mid"
+      model: "medium"
+      personality_preset: "user_advocate"
+      department: "design"
+    - role: "UX Researcher"
+      level: "mid"
+      model: "medium"
+      personality_preset: "user_advocate"
+      department: "design"
+    # Engineering — static (3)
+    - role: "Software Architect"
+      level: "principal"
+      model: "large"
+      personality_preset: "systems_thinker"
+      department: "engineering"
+    - role: "DevOps/SRE Engineer"
+      level: "mid"
+      model: "medium"
+      personality_preset: "process_optimizer"
+      department: "engineering"
+    - role: "Database Engineer"
+      level: "mid"
+      model: "medium"
+      personality_preset: "systems_thinker"
+      department: "engineering"
+    # Engineering — dynamic backend devs
+{% for i in range(num_backend_devs | default(3) | int) %}
     - role: "Backend Developer"
+      merge_id: "backend-{{ i }}"
+{% if i == 0 %}
       level: "senior"
       model: "medium"
       personality_preset: "pragmatic_builder"
+{% else %}
+      level: "mid"
+      model: "small"
+      personality_preset: "eager_learner"
+{% endif %}
+      department: "engineering"
+{% endfor %}
+    # Engineering — dynamic frontend devs
+{% for i in range(num_frontend_devs | default(2) | int) %}
+    - role: "Frontend Developer"
+      merge_id: "frontend-{{ i }}"
+{% if i == 0 %}
+      level: "senior"
+      model: "medium"
+      personality_preset: "creative_innovator"
+{% else %}
+      level: "mid"
+      model: "small"
+      personality_preset: "eager_learner"
+{% endif %}
       department: "engineering"
+{% endfor %}
+    # Quality Assurance (3)
+    - role: "QA Lead"
+      level: "lead"
+      model: "medium"
+      personality_preset: "quality_guardian"
+      department: "quality_assurance"
     - role: "QA Engineer"
       level: "mid"
       model: "small"
       personality_preset: "methodical_analyst"
       department: "quality_assurance"
+    - role: "Automation Engineer"
+      level: "mid"
+      model: "small"
+      personality_preset: "disciplined_executor"
+      department: "quality_assurance"
+    # Data & Analytics (2)
+    - role: "Data Analyst"
+      level: "mid"
+      model: "medium"
+      personality_preset: "data_driven_optimizer"
+      department: "data_analytics"
+    - role: "Data Engineer"
+      level: "mid"
+      model: "medium"
+      personality_preset: "pragmatic_builder"
+      department: "data_analytics"
+    # Operations (2)
+    - role: "Project Manager"
+      level: "senior"
+      model: "medium"
+      personality_preset: "process_optimizer"
+      department: "operations"
+    - role: "Scrum Master"
+      level: "senior"
+      model: "medium"
+      personality_preset: "process_optimizer"
+      department: "operations"
+    # Security (2)
+    - role: "Security Engineer"
+      level: "senior"
+      model: "medium"
+      personality_preset: "security_sentinel"
+      department: "security"
+    - role: "Security Operations"
+      level: "senior"
+      model: "medium"
+      personality_preset: "security_sentinel"
+      department: "security"
+    # Creative & Marketing (2)
+    - role: "Content Writer"
+      level: "mid"
+      model: "small"
+      personality_preset: "technical_communicator"
+      department: "creative_marketing"
+    - role: "Brand Strategist"
+      level: "senior"
+      model: "medium"
+      personality_preset: "growth_hacker"
+      department: "creative_marketing"
 
   workflow: "agile_kanban"
   communication: "hybrid"
diff --git a/src/ai_company/templates/builtins/product_team.yaml b/src/ai_company/templates/builtins/product_team.yaml
index fc87c197c8..9dddc8899a 100644
--- a/src/ai_company/templates/builtins/product_team.yaml
+++ b/src/ai_company/templates/builtins/product_team.yaml
@@ -2,6 +2,8 @@ template:
   name: "Product Team"
   description: "Product-focused development with design and QA"
   version: "1.0.0"
+  min_agents: 8
+  max_agents: 12
   tags:
     - "product"
     - "design"
@@ -23,25 +25,54 @@ template:
 
   departments:
     - name: "product"
-      budget_percent: 30
+      budget_percent: 25
       head_role: "Product Manager"
     - name: "engineering"
-      budget_percent: 50
+      budget_percent: 35
       head_role: "Backend Developer"
+    - name: "design"
+      budget_percent: 15
+      head_role: "UX Designer"
     - name: "quality_assurance"
-      budget_percent: 20
+      budget_percent: 15
       head_role: "QA Engineer"
+    - name: "data_analytics"
+      budget_percent: 10
+      head_role: "Data Analyst"
 
   agents:
     - role: "Product Manager"
       level: "senior"
       model: "medium"
-      personality_preset: "visionary_leader"
+      personality_preset: "strategic_planner"
       department: "product"
     - role: "UX Designer"
       level: "mid"
       model: "medium"
-      department: "product"
+      personality_preset: "user_advocate"
+      department: "design"
+    - role: "UX Researcher"
+      level: "mid"
+      model: "medium"
+      personality_preset: "user_advocate"
+      department: "design"
+    - role: "Backend Developer"
+      merge_id: "backend-senior"
+      level: "senior"
+      model: "medium"
+      personality_preset: "pragmatic_builder"
+      department: "engineering"
+    - role: "Backend Developer"
+      merge_id: "backend-mid"
+      level: "mid"
+      model: "small"
+      personality_preset: "eager_learner"
+      department: "engineering"
+    - role: "Frontend Developer"
+      level: "mid"
+      model: "small"
+      personality_preset: "creative_innovator"
+      department: "engineering"
     - role: "Full-Stack Developer"
       level: "senior"
       model: "medium"
@@ -50,8 +81,18 @@ template:
     - role: "QA Engineer"
       level: "mid"
       model: "small"
-      personality_preset: "methodical_analyst"
+      personality_preset: "quality_guardian"
       department: "quality_assurance"
+    - role: "Automation Engineer"
+      level: "mid"
+      model: "small"
+      personality_preset: "disciplined_executor"
+      department: "quality_assurance"
+    - role: "Data Analyst"
+      level: "mid"
+      model: "medium"
+      personality_preset: "data_driven_optimizer"
+      department: "data_analytics"
 
   workflow: "agile_kanban"
   communication: "hybrid"
diff --git a/src/ai_company/templates/builtins/research_lab.yaml b/src/ai_company/templates/builtins/research_lab.yaml
index 6a0bb47b3f..c93ba72229 100644
--- a/src/ai_company/templates/builtins/research_lab.yaml
+++ b/src/ai_company/templates/builtins/research_lab.yaml
@@ -2,6 +2,8 @@ template:
   name: "Research Lab"
   description: "Research and analysis focused team"
   version: "1.0.0"
+  min_agents: 5
+  max_agents: 10
   tags:
     - "research"
     - "analysis"
@@ -23,17 +25,25 @@ template:
 
   departments:
     - name: "engineering"
-      budget_percent: 40
+      budget_percent: 30
       head_role: "Software Architect"
     - name: "data_analytics"
-      budget_percent: 60
+      budget_percent: 50
       head_role: "Data Analyst"
+    - name: "product"
+      budget_percent: 20
+      head_role: "Technical Writer"
 
   agents:
     - role: "Software Architect"
       level: "principal"
       model: "large"
-      personality_preset: "methodical_analyst"
+      personality_preset: "systems_thinker"
+      department: "engineering"
+    - role: "Backend Developer"
+      level: "mid"
+      model: "medium"
+      personality_preset: "pragmatic_builder"
       department: "engineering"
     - role: "Data Engineer"
       level: "senior"
@@ -41,10 +51,27 @@ template:
       personality_preset: "pragmatic_builder"
       department: "data_analytics"
     - role: "Data Analyst"
+      merge_id: "analyst-primary"
       level: "mid"
       model: "medium"
+      personality_preset: "data_driven_optimizer"
+      department: "data_analytics"
+    - role: "ML Engineer"
+      level: "senior"
+      model: "medium"
+      personality_preset: "independent_researcher"
+      department: "data_analytics"
+    - role: "Data Analyst"
+      merge_id: "analyst-secondary"
+      level: "mid"
+      model: "small"
       personality_preset: "methodical_analyst"
       department: "data_analytics"
+    - role: "Technical Writer"
+      level: "mid"
+      model: "small"
+      personality_preset: "technical_communicator"
+      department: "product"
 
   workflow: "kanban"
   communication: "hybrid"
diff --git a/src/ai_company/templates/builtins/solo_founder.yaml b/src/ai_company/templates/builtins/solo_founder.yaml
index d87c8f040e..5ce403188b 100644
--- a/src/ai_company/templates/builtins/solo_founder.yaml
+++ b/src/ai_company/templates/builtins/solo_founder.yaml
@@ -2,6 +2,8 @@ template:
   name: "Solo Founder"
   description: "Minimal setup for quick prototypes and solo projects"
   version: "1.0.0"
+  min_agents: 2
+  max_agents: 3
   tags:
     - "minimal"
     - "solo"
diff --git a/src/ai_company/templates/builtins/startup.yaml b/src/ai_company/templates/builtins/startup.yaml
index c60869906c..f8acb77ba8 100644
--- a/src/ai_company/templates/builtins/startup.yaml
+++ b/src/ai_company/templates/builtins/startup.yaml
@@ -2,6 +2,8 @@ template:
   name: "Tech Startup"
   description: "Small team for building MVPs and prototypes"
   version: "1.0.0"
+  min_agents: 3
+  max_agents: 5
   tags:
     - "startup"
     - "mvp"
@@ -45,11 +47,13 @@ template:
       personality_preset: "methodical_analyst"
       department: "executive"
     - role: "Full-Stack Developer"
+      merge_id: "fullstack-senior"
       level: "senior"
       model: "medium"
       personality_preset: "pragmatic_builder"
       department: "engineering"
     - role: "Full-Stack Developer"
+      merge_id: "fullstack-mid"
       level: "mid"
       model: "small"
       personality_preset: "eager_learner"
@@ -57,6 +61,7 @@ template:
     - role: "Product Manager"
       level: "senior"
       model: "medium"
+      personality_preset: "strategic_planner"
       department: "product"
 
   workflow: "agile_kanban"
diff --git a/src/ai_company/templates/errors.py b/src/ai_company/templates/errors.py
index 42e1873e66..9175eb4999 100644
--- a/src/ai_company/templates/errors.py
+++ b/src/ai_company/templates/errors.py
@@ -20,6 +20,14 @@ class TemplateRenderError(TemplateError):
     """
 
 
+class TemplateInheritanceError(TemplateRenderError):
+    """Raised when template inheritance fails.
+
+    Covers circular inheritance chains, excessive depth,
+    and merge conflicts.
+    """
+
+
 class TemplateValidationError(TemplateError):
     """Raised when a rendered template fails validation.
 
diff --git a/src/ai_company/templates/loader.py b/src/ai_company/templates/loader.py
index 2ee1baf5fa..efa458eed7 100644
--- a/src/ai_company/templates/loader.py
+++ b/src/ai_company/templates/loader.py
@@ -14,6 +14,7 @@
 from dataclasses import dataclass
 from importlib import resources
 from pathlib import Path
+from types import MappingProxyType
 from typing import Any, Literal
 
 import yaml
@@ -25,7 +26,12 @@
     TEMPLATE_BUILTIN_DEFECT,
     TEMPLATE_LIST_SKIP_INVALID,
     TEMPLATE_LOAD_ERROR,
+    TEMPLATE_LOAD_INVALID_NAME,
+    TEMPLATE_LOAD_NOT_FOUND,
+    TEMPLATE_LOAD_PARSE_ERROR,
+    TEMPLATE_LOAD_READ_ERROR,
     TEMPLATE_LOAD_START,
+    TEMPLATE_LOAD_STRUCTURE_ERROR,
     TEMPLATE_LOAD_SUCCESS,
     TEMPLATE_PASS1_FLOAT_FALLBACK,
 )
@@ -40,16 +46,17 @@
 
 _USER_TEMPLATES_DIR = Path.home() / ".ai-company" / "templates"
 
-# Registry of built-in template names -> resource filenames.
-BUILTIN_TEMPLATES: dict[str, str] = {
-    "solo_founder": "solo_founder.yaml",
-    "startup": "startup.yaml",
-    "dev_shop": "dev_shop.yaml",
-    "product_team": "product_team.yaml",
-    "agency": "agency.yaml",
-    "full_company": "full_company.yaml",
-    "research_lab": "research_lab.yaml",
-}
+BUILTIN_TEMPLATES: MappingProxyType[str, str] = MappingProxyType(
+    {
+        "solo_founder": "solo_founder.yaml",
+        "startup": "startup.yaml",
+        "dev_shop": "dev_shop.yaml",
+        "product_team": "product_team.yaml",
+        "agency": "agency.yaml",
+        "full_company": "full_company.yaml",
+        "research_lab": "research_lab.yaml",
+    }
+)
 
 
 @dataclass(frozen=True)
@@ -169,6 +176,7 @@ def load_template(name: str) -> LoadedTemplate:
     # Sanitize to prevent path traversal (OS-independent).
     if "/" in name_clean or "\\" in name_clean or ".." in name_clean:
         msg = f"Invalid template name {name!r}: must not contain path separators"
+        logger.warning(TEMPLATE_LOAD_INVALID_NAME, template_name=name)
         raise TemplateNotFoundError(
             msg,
             locations=(ConfigLocation(file_path=f"<template:{name}>"),),
@@ -225,6 +233,7 @@ def load_template_file(path: Path | str) -> LoadedTemplate:
     path = Path(path)
     if not path.is_file():
         msg = f"Template file not found: {path}"
+        logger.warning(TEMPLATE_LOAD_NOT_FOUND, path=str(path))
         raise TemplateNotFoundError(
             msg,
             locations=(ConfigLocation(file_path=str(path)),),
@@ -242,13 +251,22 @@ def _load_builtin(name: str) -> LoadedTemplate:
     filename = BUILTIN_TEMPLATES.get(name)
     if filename is None:
         msg = f"Unknown built-in template: {name!r}"
+        logger.warning(TEMPLATE_LOAD_NOT_FOUND, template_name=name)
         raise TemplateNotFoundError(
             msg,
             locations=(ConfigLocation(file_path=f"<builtin:{name}>"),),
         )
-    ref = resources.files("ai_company.templates.builtins") / filename
-    yaml_text = ref.read_text(encoding="utf-8")
     source_name = f"<builtin:{name}>"
+    try:
+        ref = resources.files("ai_company.templates.builtins") / filename
+        yaml_text = ref.read_text(encoding="utf-8")
+    except (OSError, ImportError, TypeError) as exc:
+        msg = f"Failed to read built-in template resource {filename!r}: {exc}"
+        logger.exception(TEMPLATE_LOAD_READ_ERROR, source=source_name, error=str(exc))
+        raise TemplateRenderError(
+            msg,
+            locations=(ConfigLocation(file_path=source_name),),
+        ) from exc
     template = _parse_template_yaml(yaml_text, source_name=source_name)
     return LoadedTemplate(
         template=template,
@@ -261,7 +279,8 @@ def _load_from_file(path: Path) -> LoadedTemplate:
     """Load a template from a file path.
 
     Raises:
-        TemplateRenderError: If the file cannot be read.
+        TemplateRenderError: If the file cannot be read or YAML
+            parsing fails.
         TemplateValidationError: If validation fails.
     """
     source_name = str(path)
@@ -269,12 +288,14 @@ def _load_from_file(path: Path) -> LoadedTemplate:
         yaml_text = path.read_text(encoding="utf-8")
     except OSError as exc:
         msg = f"Unable to read template file: {path}"
+        logger.warning(TEMPLATE_LOAD_READ_ERROR, path=str(path), error=str(exc))
         raise TemplateRenderError(
             msg,
             locations=(ConfigLocation(file_path=source_name),),
         ) from exc
     except UnicodeDecodeError as exc:
         msg = f"Template file is not valid UTF-8: {path}"
+        logger.warning(TEMPLATE_LOAD_READ_ERROR, path=str(path), error=str(exc))
         raise TemplateRenderError(
             msg,
             locations=(ConfigLocation(file_path=source_name),),
@@ -334,6 +355,7 @@ def _parse_template_yaml(
         data = yaml.safe_load(safe_text)
     except yaml.YAMLError as exc:
         msg = f"Template YAML syntax error in {source_name}: {exc}"
+        logger.warning(TEMPLATE_LOAD_PARSE_ERROR, source=source_name, error=str(exc))
         raise TemplateRenderError(
             msg,
             locations=(ConfigLocation(file_path=source_name),),
@@ -343,14 +365,9 @@ def _parse_template_yaml(
     try:
         normalized = _normalize_template_data(template_data)
         return CompanyTemplate(**normalized)
-    except ValidationError as exc:
-        msg = f"Template validation failed for {source_name}: {exc}"
-        raise TemplateValidationError(
-            msg,
-            locations=(ConfigLocation(file_path=source_name),),
-        ) from exc
-    except (ValueError, TypeError) as exc:
+    except (ValidationError, ValueError, TypeError) as exc:
         msg = f"Template validation failed for {source_name}: {exc}"
+        logger.warning(TEMPLATE_LOAD_PARSE_ERROR, source=source_name, error=str(exc))
         raise TemplateValidationError(
             msg,
             locations=(ConfigLocation(file_path=source_name),),
@@ -368,6 +385,7 @@ def _validate_template_structure(
     """
     if not isinstance(data, dict) or "template" not in data:
         msg = f"Template YAML must have a top-level 'template' key in {source_name}"
+        logger.warning(TEMPLATE_LOAD_STRUCTURE_ERROR, source=source_name, error=msg)
         raise TemplateValidationError(
             msg,
             locations=(ConfigLocation(file_path=source_name),),
@@ -375,6 +393,7 @@ def _validate_template_structure(
     template_data = data["template"]
     if not isinstance(template_data, dict):
         msg = f"Template 'template' key must map to an object in {source_name}"
+        logger.warning(TEMPLATE_LOAD_STRUCTURE_ERROR, source=source_name, error=msg)
         raise TemplateValidationError(
             msg,
             locations=(ConfigLocation(file_path=source_name),),
@@ -394,13 +413,17 @@ def _normalize_template_data(data: dict[str, Any]) -> dict[str, Any]:
     Returns:
         Dict suitable for ``CompanyTemplate(**result)``.
     """
-    company_raw = data.get("company", {})
-    if company_raw is None:
-        company_raw = {}
-    if not isinstance(company_raw, dict):
+    company = data.get("company")
+    if company is None:
+        company = {}
+    elif not isinstance(company, dict):
         msg = "Template field 'template.company' must be a mapping"
+        logger.warning(
+            TEMPLATE_LOAD_STRUCTURE_ERROR,
+            source="template.company",
+            error=msg,
+        )
         raise TypeError(msg)
-    company: dict[str, Any] = company_raw
 
     metadata: dict[str, Any] = {
         "description": data.get("description", ""),
@@ -410,8 +433,12 @@ def _normalize_template_data(data: dict[str, Any]) -> dict[str, Any]:
     }
     if "name" in data:
         metadata["name"] = data["name"]
+    if "min_agents" in data:
+        metadata["min_agents"] = data["min_agents"]
+    if "max_agents" in data:
+        metadata["max_agents"] = data["max_agents"]
 
-    return {
+    result: dict[str, Any] = {
         "metadata": metadata,
         "variables": data.get("variables", ()),
         "agents": data.get("agents", ()),
@@ -420,7 +447,12 @@ def _normalize_template_data(data: dict[str, Any]) -> dict[str, Any]:
         "communication": data.get("communication", "hybrid"),
         "budget_monthly": _to_float(company.get("budget_monthly", 50.0)),
         "autonomy": _to_float(company.get("autonomy", 0.5)),
+        "workflow_handoffs": data.get("workflow_handoffs", ()),
+        "escalation_paths": data.get("escalation_paths", ()),
     }
+    if "extends" in data:
+        result["extends"] = data["extends"]
+    return result
 
 
 def _to_float(value: Any) -> float:
diff --git a/src/ai_company/templates/merge.py b/src/ai_company/templates/merge.py
new file mode 100644
index 0000000000..dfd994b637
--- /dev/null
+++ b/src/ai_company/templates/merge.py
@@ -0,0 +1,278 @@
+"""Template config merging for inheritance.
+
+Provides ``merge_template_configs`` which combines a parent config dict
+with a child config dict, implementing the merge semantics described in
+the template inheritance design.
+"""
+
+import copy
+from dataclasses import dataclass, field
+from typing import Any
+
+from ai_company.config.utils import deep_merge
+from ai_company.observability import get_logger
+from ai_company.observability.events.template import (
+    TEMPLATE_INHERIT_MERGE,
+    TEMPLATE_INHERIT_MERGE_ERROR,
+)
+from ai_company.templates.errors import TemplateInheritanceError
+
+logger = get_logger(__name__)
+
+# Single source of truth for the default department.
+# renderer.py re-imports this value for its own use.
+DEFAULT_MERGE_DEPARTMENT = "engineering"
+
+
+@dataclass
+class _ParentEntry:
+    """Tracking record for a parent agent during merge."""
+
+    index: int
+    agent: dict[str, Any] | None
+    matched: bool = field(default=False)
+
+
+def merge_template_configs(
+    parent: dict[str, Any],
+    child: dict[str, Any],
+) -> dict[str, Any]:
+    """Merge a parent config dict with a child config dict.
+
+    Merge strategies by field:
+
+    - ``company_name``, ``company_type``: child wins if present.
+    - ``config`` (dict): deep-merged; child keys override parent.
+    - ``agents`` (list): merged by ``(role, department, merge_id)`` key.
+    - ``departments`` (list): merged by ``name`` (case-insensitive).
+    - ``workflow_handoffs``, ``escalation_paths``: child replaces
+      entirely if present.
+
+    Args:
+        parent: Rendered parent config dict (post-Jinja2, pre-defaults).
+        child: Rendered child config dict (post-Jinja2, pre-defaults).
+
+    Returns:
+        New merged config dict.
+    """
+    logger.debug(TEMPLATE_INHERIT_MERGE, action="start")
+
+    result: dict[str, Any] = {}
+
+    # Scalars: child wins if present.
+    for key in ("company_name", "company_type"):
+        if key in child and child[key] is not None:
+            result[key] = child[key]
+        elif key in parent:
+            result[key] = parent[key]
+
+    # Config dict: deep merge.
+    parent_config = parent.get("config", {})
+    child_config = child.get("config", {})
+    if parent_config or child_config:
+        result["config"] = deep_merge(
+            parent_config if isinstance(parent_config, dict) else {},
+            child_config if isinstance(child_config, dict) else {},
+        )
+
+    # Agents: merge by (role, department) key.
+    parent_agents = parent.get("agents", [])
+    child_agents = child.get("agents", [])
+    if parent_agents or child_agents:
+        result["agents"] = _merge_agents(parent_agents, child_agents)
+
+    # Departments: merge by name.
+    parent_depts = parent.get("departments", [])
+    child_depts = child.get("departments", [])
+    if parent_depts or child_depts:
+        result["departments"] = _merge_departments(parent_depts, child_depts)
+
+    # Replace-if-present fields (deep-copied to prevent reference sharing).
+    for key in ("workflow_handoffs", "escalation_paths"):
+        if key in child and child[key] is not None:
+            result[key] = copy.deepcopy(child[key])
+        elif key in parent:
+            result[key] = copy.deepcopy(parent[key])
+
+    logger.debug(TEMPLATE_INHERIT_MERGE, action="done")
+    return result
+
+
+def _merge_agents(
+    parent_agents: list[dict[str, Any]],
+    child_agents: list[dict[str, Any]],
+) -> list[dict[str, Any]]:
+    """Merge agent lists by ``(role, department, merge_id)`` key.
+
+    Algorithm:
+    1. Index parent agents by ``(role.lower(), department.lower(),
+       merge_id.lower())``.  Duplicate keys maintain an ordered list
+       per key.
+    2. Walk child agents:
+       - ``_remove: true``: find first unmatched parent with same key,
+         remove it. Child entry is discarded.
+       - Otherwise: match against first unmatched parent with same key,
+         replace. No match -> append.
+    3. Discard ``_remove`` entries; strip ``_remove`` key from
+       replacement/appended dicts.
+    4. Result: parent agents (with replacements/removals) + appended.
+
+    Args:
+        parent_agents: Parent agent dicts, each expected to have at
+            least ``role`` and optionally ``department`` keys.
+        child_agents: Child agent dicts; may include ``_remove: True``
+            to remove a matching parent agent.
+
+    Returns:
+        Merged agent list.
+
+    Raises:
+        TemplateInheritanceError: If ``_remove`` has no matching parent.
+    """
+    parent_entries: dict[tuple[str, str, str], list[_ParentEntry]] = {}
+    for idx, agent in enumerate(parent_agents):
+        key = _agent_key(agent)
+        parent_entries.setdefault(key, []).append(
+            _ParentEntry(index=idx, agent=copy.deepcopy(agent)),
+        )
+
+    appended: list[dict[str, Any]] = []
+    for child_agent in child_agents:
+        _apply_child_agent(child_agent, parent_entries, appended)
+
+    return _collect_merged_agents(parent_entries, appended)
+
+
+def _apply_child_agent(
+    child_agent: dict[str, Any],
+    parent_entries: dict[tuple[str, str, str], list[_ParentEntry]],
+    appended: list[dict[str, Any]],
+) -> None:
+    """Apply a single child agent against parent entries.
+
+    Updates *parent_entries* and *appended* as a local mutation
+    scoped to the enclosing ``_merge_agents`` call.
+    """
+    key = _agent_key(child_agent)
+    is_remove = child_agent.get("_remove", False)
+    entries = parent_entries.get(key, [])
+
+    matched_entry = _find_unmatched(entries)
+    clean = copy.deepcopy(
+        {k: v for k, v in child_agent.items() if k not in ("_remove", "merge_id")}
+    )
+
+    if is_remove:
+        if matched_entry is None:
+            msg = f"Cannot remove agent with key {key}: no matching parent agent found"
+            logger.error(
+                TEMPLATE_INHERIT_MERGE_ERROR,
+                action="remove_failed",
+                key=key,
+            )
+            raise TemplateInheritanceError(msg)
+        matched_entry.matched = True
+        matched_entry.agent = None  # mark for removal
+    elif matched_entry is not None:
+        matched_entry.matched = True
+        matched_entry.agent = clean
+    else:
+        appended.append(clean)
+
+
+def _find_unmatched(
+    entries: list[_ParentEntry],
+) -> _ParentEntry | None:
+    """Find first unmatched entry in a parent entries list."""
+    return next((e for e in entries if not e.matched), None)
+
+
+def _collect_merged_agents(
+    parent_entries: dict[tuple[str, str, str], list[_ParentEntry]],
+    appended: list[dict[str, Any]],
+) -> list[dict[str, Any]]:
+    """Collect surviving parent agents (in order) + appended."""
+    all_entries = sorted(
+        (entry for entries in parent_entries.values() for entry in entries),
+        key=lambda e: e.index,
+    )
+    _strip_keys = {"merge_id", "_remove"}
+    result: list[dict[str, Any]] = [
+        {k: v for k, v in entry.agent.items() if k not in _strip_keys}
+        for entry in all_entries
+        if entry.agent is not None
+    ]
+    result.extend(appended)
+    return result
+
+
+def _merge_departments(
+    parent_depts: list[dict[str, Any]],
+    child_depts: list[dict[str, Any]],
+) -> list[dict[str, Any]]:
+    """Merge department lists by name (case-insensitive).
+
+    Child dept with matching name replaces parent entirely.
+    Unmatched child depts are appended.
+
+    Args:
+        parent_depts: Parent department dicts.
+        child_depts: Child department dicts.
+
+    Returns:
+        Merged department list.
+    """
+    # Build child overrides index (skip nameless departments).
+    child_by_name: dict[str, dict[str, Any]] = {}
+    nameless_child: list[dict[str, Any]] = []
+    for child_dept in child_depts:
+        name = str(child_dept.get("name", "")).lower()
+        if not name:
+            logger.warning(
+                TEMPLATE_INHERIT_MERGE,
+                action="department_no_name",
+            )
+            nameless_child.append(child_dept)
+            continue
+        child_by_name[name] = copy.deepcopy(child_dept)
+
+    # Walk parent depts: apply child override if it exists.
+    result: list[dict[str, Any]] = []
+    seen_names: set[str] = set()
+    for dept in parent_depts:
+        name = str(dept.get("name", "")).lower()
+        if not name:
+            logger.warning(
+                TEMPLATE_INHERIT_MERGE,
+                action="department_no_name",
+            )
+            result.append(copy.deepcopy(dept))
+            continue
+        if name in child_by_name:
+            result.append(child_by_name[name])
+            seen_names.add(name)
+        else:
+            result.append(copy.deepcopy(dept))
+            seen_names.add(name)
+
+    # Append unmatched child depts + nameless children.
+    for name, child_dept in child_by_name.items():
+        if name not in seen_names:
+            result.append(child_dept)
+    result.extend(copy.deepcopy(nameless_child))
+
+    return result
+
+
+def _agent_key(agent: dict[str, Any]) -> tuple[str, str, str]:
+    """Compute the merge key for an agent dict.
+
+    Uses ``(role, department, merge_id)`` when ``merge_id`` is present,
+    otherwise ``(role, department, "")`` for backwards compatibility.
+    """
+    role = str(agent.get("role", "")).lower()
+    dept = agent.get("department")
+    if not dept:
+        dept = DEFAULT_MERGE_DEPARTMENT
+    merge_id = str(agent.get("merge_id", "")).lower()
+    return (role, str(dept).lower(), merge_id)
diff --git a/src/ai_company/templates/presets.py b/src/ai_company/templates/presets.py
index cb1918a000..c2ee5e7c87 100644
--- a/src/ai_company/templates/presets.py
+++ b/src/ai_company/templates/presets.py
@@ -8,6 +8,8 @@
 from types import MappingProxyType
 from typing import Any
 
+from pydantic import ValidationError
+
 from ai_company.core.agent import PersonalityConfig
 from ai_company.observability import get_logger
 from ai_company.observability.events.template import (
@@ -16,8 +18,7 @@
 
 logger = get_logger(__name__)
 
-# Preset name -> frozen dict compatible with PersonalityConfig constructor.
-# Both the outer mapping and each inner mapping are read-only.
+# Mutable construction helper; frozen into PERSONALITY_PRESETS below.
 _RAW_PRESETS: dict[str, dict[str, Any]] = {
     "visionary_leader": {
         "traits": ("strategic", "decisive", "inspiring"),
@@ -259,7 +260,88 @@
         "verbosity": "balanced",
         "conflict_approach": "compromise",
     },
+    "user_advocate": {
+        "traits": ("empathetic", "user-focused", "observant"),
+        "communication_style": "warm",
+        "risk_tolerance": "medium",
+        "creativity": "medium",
+        "description": "A user-focused advocate who champions end-user needs.",
+        "openness": 0.7,
+        "conscientiousness": 0.65,
+        "extraversion": 0.6,
+        "agreeableness": 0.85,
+        "stress_response": 0.6,
+        "decision_making": "consultative",
+        "collaboration": "team",
+        "verbosity": "balanced",
+        "conflict_approach": "collaborate",
+    },
+    "process_optimizer": {
+        "traits": ("systematic", "efficiency-driven", "organized"),
+        "communication_style": "structured",
+        "risk_tolerance": "low",
+        "creativity": "medium",
+        "description": "A systematic optimizer who streamlines processes.",
+        "openness": 0.45,
+        "conscientiousness": 0.9,
+        "extraversion": 0.5,
+        "agreeableness": 0.55,
+        "stress_response": 0.75,
+        "decision_making": "directive",
+        "collaboration": "team",
+        "verbosity": "balanced",
+        "conflict_approach": "compromise",
+    },
+    "growth_hacker": {
+        "traits": ("experimental", "data-informed", "ambitious"),
+        "communication_style": "enthusiastic",
+        "risk_tolerance": "high",
+        "creativity": "high",
+        "description": "An experimental growth hacker who drives rapid expansion.",
+        "openness": 0.85,
+        "conscientiousness": 0.5,
+        "extraversion": 0.75,
+        "agreeableness": 0.45,
+        "stress_response": 0.5,
+        "decision_making": "intuitive",
+        "collaboration": "pair",
+        "verbosity": "terse",
+        "conflict_approach": "compete",
+    },
+    "technical_communicator": {
+        "traits": ("clear", "structured", "precise"),
+        "communication_style": "formal",
+        "risk_tolerance": "low",
+        "creativity": "medium",
+        "description": "A clear communicator who makes complex topics accessible.",
+        "openness": 0.55,
+        "conscientiousness": 0.85,
+        "extraversion": 0.4,
+        "agreeableness": 0.6,
+        "stress_response": 0.7,
+        "decision_making": "analytical",
+        "collaboration": "independent",
+        "verbosity": "verbose",
+        "conflict_approach": "avoid",
+    },
+    "systems_thinker": {
+        "traits": ("holistic", "principled", "consensus-oriented"),
+        "communication_style": "structured",
+        "risk_tolerance": "medium",
+        "creativity": "high",
+        "description": "A holistic thinker who sees the big picture in systems.",
+        "openness": 0.8,
+        "conscientiousness": 0.75,
+        "extraversion": 0.45,
+        "agreeableness": 0.65,
+        "stress_response": 0.7,
+        "decision_making": "consultative",
+        "collaboration": "team",
+        "verbosity": "balanced",
+        "conflict_approach": "collaborate",
+    },
 }
+# Both the outer mapping and each inner mapping are read-only.
 PERSONALITY_PRESETS: MappingProxyType[str, MappingProxyType[str, Any]] = (
     MappingProxyType({k: MappingProxyType(v) for k, v in _RAW_PRESETS.items()})
 )
@@ -287,6 +369,34 @@
         "data engineer": ("Reese Gallagher", "Jordan Holt", "Taylor Crane"),
         "security engineer": ("Quinn Steele", "Morgan Wolfe", "Avery Knox"),
         "content writer": ("Harper Ellis", "Kendall Frost", "Sage Monroe"),
+        "scrum master": ("Rowan Calloway", "Emery Dalton", "Finley Whitmore"),
+        "hr manager": ("Casey Pemberton", "Drew Langford", "Morgan Ashworth"),
+        "ml engineer": ("Quinn Fairchild", "Sage Navarro", "Avery Thornton"),
+        "performance engineer": (
+            "Jordan Blackwell",
+            "Taylor Winslow",
+            "Blake Prescott",
+        ),
+        "automation engineer": (
+            "Riley Kendrick",
+            "Dakota Ellsworth",
+            "Skyler Hargrove",
+        ),
+        "brand strategist": (
+            "Phoenix Carmichael",
+            "Lennox Whitfield",
+            "Kendall Beaumont",
+        ),
+        "growth marketer": ("Harper Kingsley", "Noel Radcliffe", "Kai Vandermeer"),
+        "ux researcher": ("Finley Lockwood", "Emery Ashford", "Rowan Sinclair"),
+        "technical writer": ("Drew Fairbanks", "Casey Ellington", "Blake Holcombe"),
+        "database engineer": ("Reese Northcott", "Jordan Aldridge", "Taylor Wyndham"),
+        "security operations": (
+            "Quinn Blackwood",
+            "Morgan Westbrook",
+            "Avery Cartwright",
+        ),
+        "project manager": ("Sage Pembroke", "Harley Kensington", "Lennox Beaufort"),
         "_default": ("Agent Alpha", "Agent Beta", "Agent Gamma", "Agent Delta"),
     }
 )
@@ -321,10 +431,9 @@ def get_personality_preset(name: str) -> dict[str, Any]:
 for _preset_name, _preset_dict in PERSONALITY_PRESETS.items():
     try:
         PersonalityConfig(**_preset_dict)
-    except Exception as _exc:
+    except (ValidationError, TypeError) as _exc:
         msg = f"Invalid personality preset {_preset_name!r}: {_exc}"
         raise ValueError(msg) from _exc
-# Clean up loop variables only if the loop body executed (non-empty dict).
 if PERSONALITY_PRESETS:
     del _preset_name, _preset_dict
 
diff --git a/src/ai_company/templates/renderer.py b/src/ai_company/templates/renderer.py
index 742e29b69d..d4d5e21452 100644
--- a/src/ai_company/templates/renderer.py
+++ b/src/ai_company/templates/renderer.py
@@ -6,6 +6,10 @@
 2. Render the raw YAML text through a Jinja2 ``SandboxedEnvironment``.
 3. YAML-parse the rendered text.
 4. Build a ``RootConfig``-compatible dict and validate.
+
+Template inheritance (``extends``) is resolved at the renderer level:
+each template's Jinja2 is rendered independently, then configs are
+merged via :func:`~ai_company.templates.merge.merge_template_configs`.
 """
 
 from typing import TYPE_CHECKING, Any
@@ -22,17 +26,25 @@
 from ai_company.core.agent import PersonalityConfig
 from ai_company.observability import get_logger
 from ai_company.observability.events.template import (
+    TEMPLATE_INHERIT_CIRCULAR,
+    TEMPLATE_INHERIT_DEPTH_EXCEEDED,
+    TEMPLATE_INHERIT_RESOLVE_START,
+    TEMPLATE_INHERIT_RESOLVE_SUCCESS,
+    TEMPLATE_PERSONALITY_PRESET_UNKNOWN,
     TEMPLATE_RENDER_JINJA2_ERROR,
     TEMPLATE_RENDER_START,
     TEMPLATE_RENDER_SUCCESS,
+    TEMPLATE_RENDER_TYPE_ERROR,
     TEMPLATE_RENDER_VALIDATION_ERROR,
     TEMPLATE_RENDER_VARIABLE_ERROR,
     TEMPLATE_RENDER_YAML_ERROR,
 )
 from ai_company.templates.errors import (
+    TemplateInheritanceError,
     TemplateRenderError,
     TemplateValidationError,
 )
+from ai_company.templates.merge import DEFAULT_MERGE_DEPARTMENT, merge_template_configs
 from ai_company.templates.presets import (
     generate_auto_name,
     get_personality_preset,
@@ -42,7 +54,10 @@
 _DEFAULT_PROVIDER = "default"
 
 # Default department when not specified in template agent config.
-_DEFAULT_DEPARTMENT = "engineering"
+_DEFAULT_DEPARTMENT = DEFAULT_MERGE_DEPARTMENT
+
+# Maximum inheritance chain depth.
+_MAX_INHERITANCE_DEPTH = 10
 
 if TYPE_CHECKING:
     from ai_company.templates.loader import LoadedTemplate
@@ -57,6 +72,8 @@ def render_template(
 ) -> RootConfig:
     """Render a loaded template into a validated RootConfig.
 
+    Resolves template inheritance (``extends``) before validation.
+
     Args:
         loaded: :class:`LoadedTemplate` from the loader.
         variables: User-supplied variable values (overrides defaults).
@@ -67,11 +84,41 @@ def render_template(
     Raises:
         TemplateRenderError: If rendering fails.
         TemplateValidationError: If validation fails.
+        TemplateInheritanceError: If inheritance resolution fails.
     """
     logger.info(
         TEMPLATE_RENDER_START,
         source_name=loaded.source_name,
     )
+    config_dict = _render_to_dict(loaded, variables)
+
+    # Merge with defaults and validate.
+    merged = deep_merge(default_config_dict(), config_dict)
+    result = _validate_as_root_config(merged, loaded.source_name)
+    logger.info(
+        TEMPLATE_RENDER_SUCCESS,
+        source_name=loaded.source_name,
+    )
+    return result
+
+
+def _render_to_dict(
+    loaded: LoadedTemplate,
+    variables: dict[str, Any] | None = None,
+    *,
+    _chain: frozenset[str] = frozenset(),
+) -> dict[str, Any]:
+    """Render a template to a config dict, resolving inheritance.
+
+    Args:
+        loaded: Loaded template.
+        variables: User-supplied variables.
+        _chain: Set of already-seen template identifiers for circular
+            detection (internal use).
+
+    Returns:
+        Config dict suitable for merging with defaults.
+    """
     template = loaded.template
     vars_dict = _collect_variables(template, variables or {})
 
@@ -85,16 +132,148 @@ def render_template(
     # Parse the rendered YAML.
     rendered_data = _parse_rendered_yaml(rendered_text, loaded.source_name)
 
-    # Build RootConfig dict from the rendered data.
-    config_dict = _build_config_dict(rendered_data, template, vars_dict)
+    # Build config dict from the rendered data.
+    child_config = _build_config_dict(rendered_data, template, vars_dict)
+
+    # If no inheritance, return child config directly.
+    if template.extends is None:
+        return child_config
+
+    # Resolve inheritance chain.
+    return _resolve_inheritance(
+        child_config=child_config,
+        loaded=loaded,
+        vars_dict=vars_dict,
+        _chain=_chain,
+    )
+
+
+def _resolve_inheritance(
+    *,
+    child_config: dict[str, Any],
+    loaded: LoadedTemplate,
+    vars_dict: dict[str, Any],
+    _chain: frozenset[str],
+) -> dict[str, Any]:
+    """Resolve template inheritance for a child config.
+
+    Loads and renders the parent, detects circular dependencies and
+    depth violations, then merges parent + child.
+
+    Args:
+        child_config: Already-rendered child config dict.
+        loaded: The child's :class:`LoadedTemplate`.
+        vars_dict: Child's resolved variables.
+        _chain: Already-visited parent names for circular detection.
+
+    Returns:
+        Merged config dict (parent + child).
+
+    Raises:
+        TemplateInheritanceError: On circular chains or depth overflow.
+    """
+    # Guaranteed by _render_to_dict caller.
+    assert loaded.template.extends is not None  # noqa: S101
+    parent_name: str = loaded.template.extends
+    child_id = loaded.source_name
 
-    # Merge with defaults and validate.
-    merged = deep_merge(default_config_dict(), config_dict)
-    result = _validate_as_root_config(merged, loaded.source_name)
     logger.info(
-        TEMPLATE_RENDER_SUCCESS,
-        source_name=loaded.source_name,
+        TEMPLATE_INHERIT_RESOLVE_START,
+        child=child_id,
+        parent=parent_name,
+    )
+
+    _validate_inheritance_chain(child_id, parent_name, _chain)
+
+    merged = _render_and_merge_parent(
+        parent_name,
+        child_config,
+        vars_dict,
+        _chain,
+    )
+    logger.info(
+        TEMPLATE_INHERIT_RESOLVE_SUCCESS,
+        child=child_id,
+        parent=parent_name,
+    )
+    return merged
+
+
+def _validate_inheritance_chain(
+    child_id: str,
+    parent_name: str,
+    _chain: frozenset[str],
+) -> None:
+    """Check for circular inheritance and depth overflow."""
+    if parent_name in _chain:
+        logger.error(
+            TEMPLATE_INHERIT_CIRCULAR,
+            child=child_id,
+            parent=parent_name,
+            chain=sorted(_chain),
+        )
+        msg = (
+            f"Circular template inheritance: {child_id!r} extends "
+            f"{parent_name!r}, which is already in the inheritance chain"
+        )
+        raise TemplateInheritanceError(msg)
+
+    if len(_chain) >= _MAX_INHERITANCE_DEPTH:
+        logger.error(
+            TEMPLATE_INHERIT_DEPTH_EXCEEDED,
+            child=child_id,
+            depth=len(_chain),
+            max_depth=_MAX_INHERITANCE_DEPTH,
+        )
+        msg = (
+            f"Template inheritance depth exceeded ({len(_chain)} >= "
+            f"{_MAX_INHERITANCE_DEPTH}): {child_id!r}"
+        )
+        raise TemplateInheritanceError(msg)
+
+
+def _render_and_merge_parent(
+    parent_name: str,
+    child_config: dict[str, Any],
+    vars_dict: dict[str, Any],
+    _chain: frozenset[str],
+) -> dict[str, Any]:
+    """Load, render, and merge a parent template with a child config."""
+    from ai_company.templates.loader import load_template  # noqa: PLC0415
+
+    parent_loaded = load_template(parent_name)
+    parent_vars = _collect_parent_variables(
+        parent_loaded.template,
+        vars_dict,
     )
+    parent_config = _render_to_dict(
+        parent_loaded,
+        parent_vars,
+        _chain=_chain | {parent_name},
+    )
+    return merge_template_configs(parent_config, child_config)
+
+
+def _collect_parent_variables(
+    parent_template: CompanyTemplate,
+    child_vars: dict[str, Any],
+) -> dict[str, Any]:
+    """Collect variables for a parent template.
+
+    Child's resolved variables serve as defaults for the parent.
+    Parent's own defaults fill gaps.
+
+    Args:
+        parent_template: The parent template.
+        child_vars: Child's resolved variables.
+
+    Returns:
+        Variable dict for parent rendering.
+    """
+    result: dict[str, Any] = dict(child_vars)
+    for var in parent_template.variables:
+        if var.name not in result and var.default is not None:
+            result[var.name] = var.default
     return result
 
 
@@ -259,10 +438,10 @@ def _build_config_dict(
     Returns:
         Dict suitable for ``RootConfig(**deep_merge(defaults, result))``.
     """
-    company = rendered_data.get("company", {})
+    company = rendered_data.get("company")
     if company is None:
         company = {}
-    if not isinstance(company, dict):
+    elif not isinstance(company, dict):
         msg = "Rendered template 'company' must be a mapping"
         logger.error(TEMPLATE_RENDER_YAML_ERROR, error=msg)
         raise TemplateRenderError(msg)
@@ -272,7 +451,11 @@ def _build_config_dict(
         template.metadata.name,
     )
 
-    agents = _expand_agents(_validate_list(rendered_data, "agents"))
+    has_extends = template.extends is not None
+    agents = _expand_agents(
+        _validate_list(rendered_data, "agents"),
+        has_extends=has_extends,
+    )
     departments = _build_departments(_validate_list(rendered_data, "departments"))
 
     autonomy, budget_monthly = _extract_numeric_config(company, template)
@@ -292,12 +475,20 @@ def _build_config_dict(
         },
     }
 
+    _attach_optional_lists(rendered_data, result)
+
+    return result
+
+
+def _attach_optional_lists(
+    rendered_data: dict[str, Any],
+    result: dict[str, Any],
+) -> None:
+    """Extract optional list fields from rendered data into result."""
     for key in ("workflow_handoffs", "escalation_paths"):
         if key in rendered_data and rendered_data[key] is not None:
             result[key] = _validate_list(rendered_data, key)
 
-    return result
-
 
 def _validate_list(
     rendered_data: dict[str, Any],
@@ -309,6 +500,12 @@ def _validate_list(
         raw = []
     if not isinstance(raw, list):
         msg = f"Rendered template {key!r} must be a list"
+        logger.warning(
+            TEMPLATE_RENDER_TYPE_ERROR,
+            field=key,
+            expected="list",
+            got=type(raw).__name__,
+        )
         raise TemplateRenderError(msg)
     for i, item in enumerate(raw):
         if not isinstance(item, dict):
@@ -316,6 +513,12 @@ def _validate_list(
                 f"Rendered template {key!r}[{i}] must be a "
                 f"mapping, got {type(item).__name__}"
             )
+            logger.warning(
+                TEMPLATE_RENDER_TYPE_ERROR,
+                field=f"{key}[{i}]",
+                expected="mapping",
+                got=type(item).__name__,
+            )
             raise TemplateRenderError(msg)
     return raw
 
@@ -337,27 +540,40 @@ def _extract_numeric_config(
         )
     except ValueError as exc:
         msg = f"Invalid numeric value in rendered template {source_name!r}: {exc}"
+        logger.warning(
+            TEMPLATE_RENDER_TYPE_ERROR,
+            source=source_name,
+            error=str(exc),
+        )
         raise TemplateRenderError(msg) from exc
     return autonomy, budget_monthly
 
 
 def _expand_agents(
     raw_agents: list[dict[str, Any]],
+    *,
+    has_extends: bool,
 ) -> list[dict[str, Any]]:
     """Expand template agent dicts into AgentConfig-compatible dicts.
 
     Args:
         raw_agents: List of agent dicts from rendered YAML.
+        has_extends: Whether the template uses inheritance.
 
     Returns:
         List of dicts suitable for ``AgentConfig`` construction.
     """
-    expanded: list[dict[str, Any]] = []
     used_names: set[str] = set()
-
+    expanded: list[dict[str, Any]] = []
     for idx, agent in enumerate(raw_agents):
-        expanded.append(_expand_single_agent(agent, idx, used_names))
-
+        expanded.append(
+            _expand_single_agent(
+                agent,
+                idx,
+                used_names,
+                has_extends=has_extends,
+            ),
+        )
     return expanded
 
 
@@ -365,6 +581,8 @@ def _expand_single_agent(
     agent: dict[str, Any],
     idx: int,
     used_names: set[str],
+    *,
+    has_extends: bool,
 ) -> dict[str, Any]:
     """Expand a single template agent dict.
 
@@ -374,6 +592,7 @@ def _expand_single_agent(
     role = agent.get("role")
     if not role:
         msg = f"Agent at index {idx} is missing required 'role' field"
+        logger.warning(TEMPLATE_RENDER_VARIABLE_ERROR, index=idx, field="role")
         raise TemplateRenderError(msg)
     name = str(agent.get("name", "")).strip()
 
@@ -394,6 +613,47 @@ def _expand_single_agent(
         "level": agent.get("level", "mid"),
     }
 
+    _resolve_agent_personality(agent, name, agent_dict)
+
+    model_tier = agent.get("model", "medium")
+    agent_dict["model"] = {"provider": _DEFAULT_PROVIDER, "model_id": model_tier}
+
+    # Preserve _remove merge directive for inheritance.
+    if agent.get("_remove"):
+        if not has_extends:
+            msg = (
+                f"Agent {name!r} uses '_remove' but the template "
+                "has no 'extends' — directive has no effect"
+            )
+            logger.warning(
+                TEMPLATE_RENDER_VARIABLE_ERROR,
+                agent=name,
+                field="_remove",
+            )
+            raise TemplateRenderError(msg)
+        agent_dict["_remove"] = True
+
+    return agent_dict
+
+
+def _resolve_agent_personality(
+    agent: dict[str, Any],
+    name: str,
+    agent_dict: dict[str, Any],
+) -> None:
+    """Resolve personality from inline config or named preset.
+
+    Mutates *agent_dict* to add the ``personality`` key when resolved.
+
+    Args:
+        agent: Raw agent dict from rendered YAML.
+        name: Resolved agent name for error context.
+        agent_dict: Partially-built agent dict (mutated in place).
+
+    Raises:
+        TemplateRenderError: If personality config is invalid or preset
+            is unknown.
+    """
     inline_personality = agent.get("personality")
     preset_name = agent.get("personality_preset")
     if inline_personality is not None:
@@ -402,6 +662,12 @@ def _expand_single_agent(
                 f"Personality for agent {name!r} must be a mapping, "
                 f"got {type(inline_personality).__name__}"
             )
+            logger.warning(
+                TEMPLATE_RENDER_TYPE_ERROR,
+                agent=name,
+                field="personality",
+                got=type(inline_personality).__name__,
+            )
             raise TemplateRenderError(msg)
         _validate_inline_personality(inline_personality, name)
         agent_dict["personality"] = inline_personality
@@ -410,12 +676,13 @@ def _expand_single_agent(
             agent_dict["personality"] = get_personality_preset(preset_name)
         except KeyError as exc:
             msg = f"Unknown personality preset {preset_name!r} for agent {name!r}"
+            logger.warning(
+                TEMPLATE_PERSONALITY_PRESET_UNKNOWN,
+                agent=name,
+                preset=preset_name,
+            )
             raise TemplateRenderError(msg) from exc
 
-    model_tier = agent.get("model", "medium")
-    agent_dict["model"] = {"provider": _DEFAULT_PROVIDER, "model_id": model_tier}
-    return agent_dict
-
 
 def _validate_inline_personality(
     personality: dict[str, Any],
@@ -462,6 +729,12 @@ def _build_departments(
             )
         except ValueError as exc:
             msg = f"Invalid department budget value: {exc}"
+            logger.warning(
+                TEMPLATE_RENDER_TYPE_ERROR,
+                department=dept.get("name", ""),
+                field="budget_percent",
+                error=str(exc),
+            )
             raise TemplateRenderError(msg) from exc
         dept_name = dept.get("name", "")
         head_role = dept.get("head_role")
@@ -482,12 +755,26 @@ def _build_departments(
         if reporting_lines is not None:
             if not isinstance(reporting_lines, list):
                 msg = f"Department {dept_name!r} 'reporting_lines' must be a list"
+                logger.warning(
+                    TEMPLATE_RENDER_TYPE_ERROR,
+                    department=dept_name,
+                    field="reporting_lines",
+                    expected="list",
+                    got=type(reporting_lines).__name__,
+                )
                 raise TemplateRenderError(msg)
             dept_dict["reporting_lines"] = reporting_lines
         policies = dept.get("policies")
         if policies is not None:
             if not isinstance(policies, dict):
                 msg = f"Department {dept_name!r} 'policies' must be a mapping"
+                logger.warning(
+                    TEMPLATE_RENDER_TYPE_ERROR,
+                    department=dept_name,
+                    field="policies",
+                    expected="mapping",
+                    got=type(policies).__name__,
+                )
                 raise TemplateRenderError(msg)
             dept_dict["policies"] = policies
         departments.append(dept_dict)
diff --git a/src/ai_company/templates/schema.py b/src/ai_company/templates/schema.py
index a8c5c95c72..ee47c88b4d 100644
--- a/src/ai_company/templates/schema.py
+++ b/src/ai_company/templates/schema.py
@@ -3,7 +3,7 @@
 from collections import Counter
 from typing import Any, Literal, Self
 
-from pydantic import BaseModel, ConfigDict, Field, model_validator
+from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
 
 from ai_company.core.enums import CompanyType, SeniorityLevel
 from ai_company.core.types import NotBlankStr  # noqa: TC001
@@ -34,7 +34,9 @@ class TemplateVariable(BaseModel):
         default="str",
         description="Expected value type",
     )
-    default: Any = Field(default=None, description="Default value")
+    default: str | int | float | bool | None = Field(
+        default=None, description="Default value"
+    )
     required: bool = Field(default=False, description="Whether required")
 
     @model_validator(mode="after")
@@ -89,8 +91,14 @@ class TemplateAgentConfig(BaseModel):
         personality_preset: Named personality preset from the presets registry.
         personality: Inline personality config dict (alternative to
             ``personality_preset``).
-        department: Department override (``None`` defaults to
-            ``"engineering"`` during rendering).
+        department: Department override (``None`` uses the template
+            system default during rendering).
+        merge_id: Stable identity for inheritance merge.  When a
+            template has multiple agents with the same ``(role,
+            department)`` pair, ``merge_id`` disambiguates them so
+            child templates can target a specific agent.
+        remove: Merge directive — when ``True``, removes matching
+            parent agent during inheritance.
     """
 
     model_config = ConfigDict(frozen=True, extra="forbid")
@@ -114,6 +122,15 @@ class TemplateAgentConfig(BaseModel):
         default=None,
         description="Department override",
     )
+    merge_id: str = Field(
+        default="",
+        description="Stable identity for inheritance merge",
+    )
+    remove: bool = Field(
+        default=False,
+        alias="_remove",
+        description="Merge directive: remove matching parent agent",
+    )
 
     @model_validator(mode="after")
     def _validate_personality_mutual_exclusion(self) -> Self:
@@ -221,6 +238,8 @@ class CompanyTemplate(BaseModel):
             1.0 = fully autonomous).
         workflow_handoffs: Cross-department workflow handoff definitions.
         escalation_paths: Cross-department escalation path definitions.
+        extends: Parent template name for inheritance (``None`` for
+            standalone templates).
     """
 
     model_config = ConfigDict(frozen=True, extra="forbid")
@@ -264,10 +283,31 @@ class CompanyTemplate(BaseModel):
         default=(),
         description="Cross-department escalation paths",
     )
+    extends: NotBlankStr | None = Field(
+        default=None,
+        description="Parent template name for inheritance",
+    )
+
+    @field_validator("extends", mode="before")
+    @classmethod
+    def _normalize_extends(cls, value: Any) -> Any:
+        """Normalize extends to lowercase stripped form."""
+        if value is None:
+            return None
+        if not isinstance(value, str):
+            return value  # let Pydantic's type validation reject it
+        return value.strip().lower()
 
     @model_validator(mode="after")
     def _validate_agent_count_in_range(self) -> Self:
-        """Agent count must be within metadata min/max."""
+        """Agent count must be within metadata min/max.
+
+        Skipped when ``extends`` is set because the child may define
+        zero agents (inheriting all from parent).  The final merged
+        result is validated separately.
+        """
+        if self.extends is not None:
+            return self
         count = len(self.agents)
         if count < self.metadata.min_agents:
             msg = (
diff --git a/tests/unit/templates/conftest.py b/tests/unit/templates/conftest.py
index dffdaf5b86..d86c990164 100644
--- a/tests/unit/templates/conftest.py
+++ b/tests/unit/templates/conftest.py
@@ -97,6 +97,88 @@ def __call__(self, content: str, name: str = ...) -> Path: ...
 agents: []
 """
 
+CHILD_EXTENDS_STARTUP_YAML = """\
+template:
+  name: "Child of Startup"
+  description: "Extends startup with extra agents"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 20
+  extends: "startup"
+
+  company:
+    type: "startup"
+
+  agents:
+    - role: "QA Engineer"
+      level: "mid"
+      model: "small"
+      personality_preset: "quality_guardian"
+      department: "engineering"
+"""
+
+CHILD_OVERRIDE_AGENT_YAML = """\
+template:
+  name: "Override Child"
+  description: "Overrides a parent agent"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 20
+  extends: "solo_founder"
+
+  company:
+    type: "solo_founder"
+
+  agents:
+    - role: "Full-Stack Developer"
+      level: "lead"
+      model: "large"
+      personality_preset: "visionary_leader"
+      department: "engineering"
+"""
+
+CHILD_REMOVE_AGENT_YAML = """\
+template:
+  name: "Remove Child"
+  description: "Removes a parent agent"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 20
+  extends: "solo_founder"
+
+  company:
+    type: "solo_founder"
+
+  agents:
+    - role: "Full-Stack Developer"
+      department: "engineering"
+      _remove: true
+    - role: "Backend Developer"
+      level: "senior"
+      model: "medium"
+      personality_preset: "pragmatic_builder"
+      department: "engineering"
+"""
+
+CIRCULAR_SELF_YAML = """\
+template:
+  name: "Self Loop"
+  description: "Extends itself"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 10
+  extends: "self_loop"
+
+  company:
+    type: "custom"
+
+  agents:
+    - role: "Backend Developer"
+      level: "mid"
+      model: "medium"
+      department: "engineering"
+"""
+
 
 def _make_template_dict(**overrides: Any) -> dict[str, Any]:
     """Build a minimal valid CompanyTemplate kwargs dict with overrides."""
diff --git a/tests/unit/templates/test_inheritance.py b/tests/unit/templates/test_inheritance.py
new file mode 100644
index 0000000000..079a2d3e66
--- /dev/null
+++ b/tests/unit/templates/test_inheritance.py
@@ -0,0 +1,512 @@
+"""Tests for template inheritance (extends) and merge logic."""
+
+from typing import TYPE_CHECKING, Any
+from unittest.mock import patch
+
+if TYPE_CHECKING:
+    from pathlib import Path
+
+import pytest
+
+from ai_company.config.schema import RootConfig
+from ai_company.core.enums import CompanyType
+from ai_company.templates.errors import TemplateInheritanceError
+from ai_company.templates.loader import load_template, load_template_file
+from ai_company.templates.merge import (
+    _merge_agents,
+    _merge_departments,
+    merge_template_configs,
+)
+from ai_company.templates.renderer import _collect_parent_variables, render_template
+from ai_company.templates.schema import (
+    CompanyTemplate,
+    TemplateAgentConfig,
+    TemplateMetadata,
+    TemplateVariable,
+)
+
+from .conftest import (
+    CHILD_EXTENDS_STARTUP_YAML,
+    CHILD_OVERRIDE_AGENT_YAML,
+    CHILD_REMOVE_AGENT_YAML,
+    CIRCULAR_SELF_YAML,
+)
+
+pytestmark = pytest.mark.timeout(30)
+
+
+# ── TestMergeAgents ──────────────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestMergeAgents:
+    def test_inherit_parent_agents(self) -> None:
+        """Child with no agents inherits all parent agents."""
+        parent = [
+            {"role": "CEO", "department": "executive"},
+            {"role": "Dev", "department": "engineering"},
+        ]
+        result = _merge_agents(parent, [])
+        assert len(result) == 2
+        assert result[0]["role"] == "CEO"
+        assert result[1]["role"] == "Dev"
+
+    def test_override_by_role_dept(self) -> None:
+        """Child agent replaces matching parent by (role, department)."""
+        parent = [{"role": "Dev", "department": "engineering", "level": "mid"}]
+        child = [{"role": "Dev", "department": "engineering", "level": "senior"}]
+        result = _merge_agents(parent, child)
+        assert len(result) == 1
+        assert result[0]["level"] == "senior"
+
+    def test_add_new_agent(self) -> None:
+        """Unmatched child agent is appended."""
+        parent = [{"role": "CEO", "department": "executive"}]
+        child = [{"role": "QA Engineer", "department": "qa"}]
+        result = _merge_agents(parent, child)
+        assert len(result) == 2
+        assert result[1]["role"] == "QA Engineer"
+
+    def test_multiple_same_role_positional_match(self) -> None:
+        """Multiple parents with same key are matched positionally."""
+        parent = [
+            {"role": "Dev", "department": "eng", "name": "first"},
+            {"role": "Dev", "department": "eng", "name": "second"},
+        ]
+        child = [
+            {"role": "Dev", "department": "eng", "name": "replaced-first"},
+        ]
+        result = _merge_agents(parent, child)
+        assert len(result) == 2
+        assert result[0]["name"] == "replaced-first"
+        assert result[1]["name"] == "second"
+
+    def test_remove_marker(self) -> None:
+        """_remove: true removes matching parent agent."""
+        parent = [
+            {"role": "CEO", "department": "executive"},
+            {"role": "Dev", "department": "engineering"},
+        ]
+        child = [{"role": "Dev", "department": "engineering", "_remove": True}]
+        result = _merge_agents(parent, child)
+        assert len(result) == 1
+        assert result[0]["role"] == "CEO"
+
+    def test_remove_nonexistent_raises(self) -> None:
+        """_remove with no matching parent raises error."""
+        parent = [{"role": "CEO", "department": "executive"}]
+        child = [{"role": "QA", "department": "qa", "_remove": True}]
+        with pytest.raises(TemplateInheritanceError, match="no matching parent"):
+            _merge_agents(parent, child)
+
+    def test_remove_marker_stripped_from_output(self) -> None:
+        """_remove key is not in the output for non-remove agents."""
+        parent = [{"role": "Dev", "department": "eng"}]
+        child = [{"role": "Dev", "department": "eng", "_remove": False, "level": "sr"}]
+        result = _merge_agents(parent, child)
+        assert "_remove" not in result[0]
+
+
+# ── TestMergeDepartments ─────────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestMergeDepartments:
+    def test_inherit_parent_departments(self) -> None:
+        """Child with no departments inherits all parent depts."""
+        parent = [{"name": "engineering"}, {"name": "product"}]
+        result = _merge_departments(parent, [])
+        assert len(result) == 2
+
+    def test_override_by_name(self) -> None:
+        """Child dept with matching name replaces parent entirely."""
+        parent = [{"name": "engineering", "budget_percent": 50}]
+        child = [{"name": "Engineering", "budget_percent": 80}]
+        result = _merge_departments(parent, child)
+        assert len(result) == 1
+        assert result[0]["budget_percent"] == 80
+
+    def test_add_new_department(self) -> None:
+        """Unmatched child dept is appended."""
+        parent = [{"name": "engineering"}]
+        child = [{"name": "marketing"}]
+        result = _merge_departments(parent, child)
+        assert len(result) == 2
+        assert result[1]["name"] == "marketing"
+
+
+# ── TestMergeTemplateConfigs ─────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestMergeTemplateConfigs:
+    def test_scalars_child_wins(self) -> None:
+        """Child scalars override parent."""
+        parent: dict[str, Any] = {"company_name": "Parent Co"}
+        child: dict[str, Any] = {"company_name": "Child Co"}
+        result = merge_template_configs(parent, child)
+        assert result["company_name"] == "Child Co"
+
+    def test_scalars_parent_fallback(self) -> None:
+        """Parent scalar used when child doesn't provide it."""
+        parent: dict[str, Any] = {
+            "company_name": "Parent Co",
+            "company_type": "startup",
+        }
+        child: dict[str, Any] = {}
+        result = merge_template_configs(parent, child)
+        assert result["company_name"] == "Parent Co"
+        assert result["company_type"] == "startup"
+
+    def test_config_deep_merge(self) -> None:
+        """Config dicts are deep-merged."""
+        parent: dict[str, Any] = {
+            "config": {"autonomy": 0.5, "budget_monthly": 100.0},
+        }
+        child: dict[str, Any] = {
+            "config": {"autonomy": 0.8},
+        }
+        result = merge_template_configs(parent, child)
+        assert result["config"]["autonomy"] == 0.8
+        assert result["config"]["budget_monthly"] == 100.0
+
+    def test_full_merge_integration(self) -> None:
+        """Full merge with agents, departments, and config."""
+        parent: dict[str, Any] = {
+            "company_name": "Parent",
+            "agents": [{"role": "CEO", "department": "exec"}],
+            "departments": [{"name": "exec"}],
+            "config": {"autonomy": 0.5},
+        }
+        child: dict[str, Any] = {
+            "company_name": "Child",
+            "agents": [{"role": "Dev", "department": "eng"}],
+            "departments": [{"name": "eng"}],
+            "config": {"budget_monthly": 200.0},
+        }
+        result = merge_template_configs(parent, child)
+        assert result["company_name"] == "Child"
+        assert len(result["agents"]) == 2
+        assert len(result["departments"]) == 2
+        assert result["config"]["autonomy"] == 0.5
+        assert result["config"]["budget_monthly"] == 200.0
+
+    def test_workflow_handoffs_child_replaces(self) -> None:
+        """Child workflow_handoffs replace parent entirely."""
+        parent: dict[str, Any] = {
+            "workflow_handoffs": [{"from": "a", "to": "b"}],
+        }
+        child: dict[str, Any] = {
+            "workflow_handoffs": [{"from": "x", "to": "y"}],
+        }
+        result = merge_template_configs(parent, child)
+        assert len(result["workflow_handoffs"]) == 1
+        assert result["workflow_handoffs"][0]["from"] == "x"
+
+    def test_escalation_paths_parent_fallback(self) -> None:
+        """Parent escalation_paths used when child doesn't provide them."""
+        parent: dict[str, Any] = {
+            "escalation_paths": [{"from": "eng", "to": "security"}],
+        }
+        child: dict[str, Any] = {}
+        result = merge_template_configs(parent, child)
+        assert result["escalation_paths"] == [{"from": "eng", "to": "security"}]
+
+    def test_none_child_scalar_uses_parent(self) -> None:
+        """None child scalar falls back to parent value."""
+        parent: dict[str, Any] = {"company_name": "Parent Co"}
+        child: dict[str, Any] = {"company_name": None}
+        result = merge_template_configs(parent, child)
+        assert result["company_name"] == "Parent Co"
+
+
+# ── TestCollectParentVariables ────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestCollectParentVariables:
+    def test_child_vars_override_parent_defaults(self) -> None:
+        """Child variables take precedence over parent defaults."""
+        parent = CompanyTemplate(
+            metadata=TemplateMetadata(name="P", company_type=CompanyType.CUSTOM),
+            variables=(
+                TemplateVariable(name="x", default="parent_x"),
+                TemplateVariable(name="y", default="parent_y"),
+            ),
+            agents=(TemplateAgentConfig(role="Backend Developer"),),
+        )
+        child_vars = {"x": "child_x", "z": "child_z"}
+        result = _collect_parent_variables(parent, child_vars)
+        assert result["x"] == "child_x"
+        assert result["y"] == "parent_y"
+        assert result["z"] == "child_z"
+
+    def test_parent_defaults_fill_gaps(self) -> None:
+        """Parent defaults fill variables not in child."""
+        parent = CompanyTemplate(
+            metadata=TemplateMetadata(name="P", company_type=CompanyType.CUSTOM),
+            variables=(TemplateVariable(name="a", default="default_a"),),
+            agents=(TemplateAgentConfig(role="Backend Developer"),),
+        )
+        result = _collect_parent_variables(parent, {})
+        assert result["a"] == "default_a"
+
+    def test_required_parent_var_without_child_value(self) -> None:
+        """Required parent var with no child value or default is omitted."""
+        parent = CompanyTemplate(
+            metadata=TemplateMetadata(name="P", company_type=CompanyType.CUSTOM),
+            variables=(TemplateVariable(name="req", required=True),),
+            agents=(TemplateAgentConfig(role="Backend Developer"),),
+        )
+        result = _collect_parent_variables(parent, {})
+        assert "req" not in result
+
+
+# ── TestResolveInheritance ───────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestResolveInheritance:
+    def test_single_level_extends(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """Child extends builtin and inherits its agents."""
+        child_path = tmp_path / "child.yaml"
+        child_path.write_text(CHILD_EXTENDS_STARTUP_YAML, encoding="utf-8")
+        loaded = load_template_file(child_path)
+        config = render_template(loaded)
+        assert isinstance(config, RootConfig)
+        # Should have startup's 5 agents + 1 new QA agent.
+        assert len(config.agents) == 6
+
+    def test_override_agent_via_extends(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """Child overrides a parent agent by (role, department)."""
+        child_path = tmp_path / "override.yaml"
+        child_path.write_text(CHILD_OVERRIDE_AGENT_YAML, encoding="utf-8")
+        loaded = load_template_file(child_path)
+        config = render_template(loaded)
+        assert isinstance(config, RootConfig)
+        # solo_founder has CEO + Full-Stack Dev. Child overrides Full-Stack Dev.
+        assert len(config.agents) == 2
+        fs_agents = [a for a in config.agents if a.role == "Full-Stack Developer"]
+        assert len(fs_agents) == 1
+        assert fs_agents[0].level.value == "lead"
+
+    def test_remove_agent_via_extends(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """Child removes a parent agent and adds a new one."""
+        child_path = tmp_path / "remove.yaml"
+        child_path.write_text(CHILD_REMOVE_AGENT_YAML, encoding="utf-8")
+        loaded = load_template_file(child_path)
+        config = render_template(loaded)
+        assert isinstance(config, RootConfig)
+        # solo_founder: CEO + FS Dev. Remove FS Dev, add Backend Dev => 2 agents.
+        roles = [a.role for a in config.agents]
+        assert "CEO" in roles
+        assert "Backend Developer" in roles
+        assert "Full-Stack Developer" not in roles
+
+    def test_variable_flow_to_parent(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """Child variables flow to parent template."""
+        child_path = tmp_path / "var_child.yaml"
+        child_path.write_text(CHILD_EXTENDS_STARTUP_YAML, encoding="utf-8")
+        loaded = load_template_file(child_path)
+        config = render_template(
+            loaded,
+            variables={"company_name": "Custom Name"},
+        )
+        # Child's company_name overrides parent's (child wins in merge).
+        assert config.company_name == "Custom Name"
+
+    def test_multi_level_extends(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """A→B→C multi-level inheritance resolves correctly."""
+        # B extends startup
+        child_b_yaml = CHILD_EXTENDS_STARTUP_YAML
+        child_b_path = tmp_path / "child_b.yaml"
+        child_b_path.write_text(child_b_yaml, encoding="utf-8")
+
+        # A extends B (using file path won't work for name-based lookup,
+        # so we use user template directory patching)
+        child_a_yaml = """\
+template:
+  name: "Grandchild"
+  description: "Two levels deep"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 30
+  extends: "child_b"
+
+  company:
+    type: "startup"
+
+  agents:
+    - role: "Data Analyst"
+      level: "mid"
+      model: "medium"
+      personality_preset: "data_driven_optimizer"
+      department: "engineering"
+"""
+        child_a_path = tmp_path / "child_a.yaml"
+        child_a_path.write_text(child_a_yaml, encoding="utf-8")
+
+        # Patch user templates dir so child_b is found by name.
+        with patch(
+            "ai_company.templates.loader._USER_TEMPLATES_DIR",
+            tmp_path,
+        ):
+            loaded = load_template_file(child_a_path)
+            config = render_template(loaded)
+            assert isinstance(config, RootConfig)
+            # startup(5) + child_b adds QA(1) + child_a adds Data Analyst(1) = 7
+            assert len(config.agents) == 7
+
+
+# ── TestCircularDetection ────────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestCircularDetection:
+    def test_self_extends_raises(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """Template extending itself raises TemplateInheritanceError."""
+        path = tmp_path / "self_loop.yaml"
+        path.write_text(CIRCULAR_SELF_YAML, encoding="utf-8")
+
+        with patch(
+            "ai_company.templates.loader._USER_TEMPLATES_DIR",
+            tmp_path,
+        ):
+            loaded = load_template_file(path)
+            with pytest.raises(
+                TemplateInheritanceError,
+                match="Circular template inheritance",
+            ):
+                render_template(loaded)
+
+    def test_a_b_a_cycle_raises(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """A→B→A cycle raises TemplateInheritanceError."""
+        a_yaml = """\
+template:
+  name: "Template A"
+  description: "test"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 10
+  extends: "template_b"
+
+  company:
+    type: "custom"
+
+  agents:
+    - role: "Backend Developer"
+      level: "mid"
+      model: "medium"
+      department: "engineering"
+"""
+        b_yaml = """\
+template:
+  name: "Template B"
+  description: "test"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 10
+  extends: "template_a"
+
+  company:
+    type: "custom"
+
+  agents:
+    - role: "Backend Developer"
+      level: "mid"
+      model: "medium"
+      department: "engineering"
+"""
+        (tmp_path / "template_a.yaml").write_text(a_yaml, encoding="utf-8")
+        (tmp_path / "template_b.yaml").write_text(b_yaml, encoding="utf-8")
+
+        with patch(
+            "ai_company.templates.loader._USER_TEMPLATES_DIR",
+            tmp_path,
+        ):
+            loaded = load_template("template_a")
+            with pytest.raises(
+                TemplateInheritanceError,
+                match="Circular template inheritance",
+            ):
+                render_template(loaded)
+
+    def test_depth_limit_exceeded_raises(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """Exceeding max depth raises TemplateInheritanceError."""
+        # Create a chain of 12 templates: t0 → t1 → ... → t11
+        for i in range(12):
+            parent_ref = f"chain_{i - 1}" if i > 0 else ""
+            extends_line = f'  extends: "{parent_ref}"' if i > 0 else ""
+            yaml_content = f"""\
+template:
+  name: "Chain {i}"
+  description: "test"
+  version: "1.0.0"
+  min_agents: 1
+  max_agents: 100
+{extends_line}
+
+  company:
+    type: "custom"
+
+  agents:
+    - role: "Backend Developer"
+      level: "mid"
+      model: "medium"
+      department: "engineering"
+"""
+            (tmp_path / f"chain_{i}.yaml").write_text(yaml_content, encoding="utf-8")
+
+        with patch(
+            "ai_company.templates.loader._USER_TEMPLATES_DIR",
+            tmp_path,
+        ):
+            loaded = load_template("chain_11")
+            with pytest.raises(
+                TemplateInheritanceError,
+                match="depth exceeded",
+            ):
+                render_template(loaded)
+
+
+# ── TestInheritanceIntegration ───────────────────────────────────
+
+
+@pytest.mark.unit
+class TestInheritanceIntegration:
+    def test_child_extends_builtin_renders_to_valid_root_config(
+        self,
+        tmp_path: Path,
+    ) -> None:
+        """File-based child extending a builtin renders to valid RootConfig."""
+        child_path = tmp_path / "custom.yaml"
+        child_path.write_text(CHILD_EXTENDS_STARTUP_YAML, encoding="utf-8")
+        loaded = load_template_file(child_path)
+        config = render_template(loaded)
+        assert isinstance(config, RootConfig)
+        assert len(config.agents) >= 1
+        assert len(config.departments) >= 1
diff --git a/tests/unit/templates/test_loader.py b/tests/unit/templates/test_loader.py
index 114c7bd26e..e4cecf41be 100644
--- a/tests/unit/templates/test_loader.py
+++ b/tests/unit/templates/test_loader.py
@@ -53,6 +53,54 @@ def test_count_matches_registry(self) -> None:
         assert len(list_builtin_templates()) == len(BUILTIN_TEMPLATES)
 
 
+@pytest.mark.unit
+class TestMinMaxPassthrough:
+    def test_min_max_agents_from_yaml(
+        self,
+        tmp_template_file: TemplateFileFactory,
+    ) -> None:
+        """min_agents/max_agents pass through from YAML to TemplateMetadata."""
+        yaml_with_minmax = """\
+template:
+  name: "MinMax Test"
+  description: "test"
+  version: "1.0.0"
+  min_agents: 3
+  max_agents: 10
+
+  company:
+    type: "custom"
+
+  agents:
+    - role: "Backend Developer"
+      level: "mid"
+      model: "medium"
+      department: "engineering"
+    - role: "Frontend Developer"
+      level: "mid"
+      model: "medium"
+      department: "engineering"
+    - role: "QA Engineer"
+      level: "mid"
+      model: "small"
+      department: "engineering"
+"""
+        path = tmp_template_file(yaml_with_minmax)
+        loaded = load_template_file(path)
+        assert loaded.template.metadata.min_agents == 3
+        assert loaded.template.metadata.max_agents == 10
+
+    def test_defaults_when_not_specified(
+        self,
+        tmp_template_file: TemplateFileFactory,
+    ) -> None:
+        """Without min/max in YAML, defaults apply (1, 100)."""
+        path = tmp_template_file(MINIMAL_TEMPLATE_YAML)
+        loaded = load_template_file(path)
+        assert loaded.template.metadata.min_agents == 1
+        assert loaded.template.metadata.max_agents == 100
+
+
 # ── list_templates ───────────────────────────────────────────────
 
 
diff --git a/tests/unit/templates/test_presets.py b/tests/unit/templates/test_presets.py
index dee2dc06f2..d1e0c31611 100644
--- a/tests/unit/templates/test_presets.py
+++ b/tests/unit/templates/test_presets.py
@@ -2,7 +2,9 @@
 
 import pytest
 
+from ai_company.core.agent import PersonalityConfig
 from ai_company.templates.presets import (
+    _AUTO_NAMES,
     PERSONALITY_PRESETS,
     generate_auto_name,
     get_personality_preset,
@@ -41,12 +43,28 @@ def test_all_presets_have_required_keys(self) -> None:
             preset = get_personality_preset(name)
             assert required_keys.issubset(preset.keys()), f"{name} missing keys"
 
-    def test_preset_count_at_least_15(self) -> None:
-        assert len(PERSONALITY_PRESETS) >= 15
+    def test_preset_count_at_least_20(self) -> None:
+        assert len(PERSONALITY_PRESETS) >= 20
+
+    @pytest.mark.parametrize(
+        "preset_name",
+        [
+            "user_advocate",
+            "process_optimizer",
+            "growth_hacker",
+            "technical_communicator",
+            "systems_thinker",
+        ],
+    )
+    def test_new_presets_produce_valid_personality_config(
+        self,
+        preset_name: str,
+    ) -> None:
+        preset = get_personality_preset(preset_name)
+        config = PersonalityConfig(**preset)
+        assert isinstance(config, PersonalityConfig)
 
     def test_all_presets_produce_valid_personality_config(self) -> None:
-        from ai_company.core.agent import PersonalityConfig
-
         for name in PERSONALITY_PRESETS:
             preset = get_personality_preset(name)
             config = PersonalityConfig(**preset)
@@ -97,3 +115,15 @@ def test_whitespace_stripped_from_role(self) -> None:
         a = generate_auto_name("  CEO  ", seed=0)
         b = generate_auto_name("CEO", seed=0)
         assert a == b
+
+
+@pytest.mark.unit
+class TestAutoNameCoverage:
+    def test_auto_names_cover_all_builtin_roles(self) -> None:
+        """Every role in BUILTIN_ROLES has an auto-name pool."""
+        from ai_company.core.role_catalog import BUILTIN_ROLES
+
+        pool_keys = {k for k in _AUTO_NAMES if k != "_default"}
+        role_keys = {r.name.lower() for r in BUILTIN_ROLES}
+        missing = role_keys - pool_keys
+        assert not missing, f"Roles missing auto-name pools: {sorted(missing)}"
diff --git a/tests/unit/templates/test_renderer.py b/tests/unit/templates/test_renderer.py
index 65756993bf..586fd0f9fb 100644
--- a/tests/unit/templates/test_renderer.py
+++ b/tests/unit/templates/test_renderer.py
@@ -12,7 +12,11 @@
     TEMPLATE_RENDER_SUCCESS,
 )
 from ai_company.templates.errors import TemplateRenderError
-from ai_company.templates.loader import load_template, load_template_file
+from ai_company.templates.loader import (
+    BUILTIN_TEMPLATES,
+    load_template,
+    load_template_file,
+)
 from ai_company.templates.renderer import render_template
 
 from .conftest import TEMPLATE_REQUIRED_VAR_YAML, TEMPLATE_WITH_VARIABLES_YAML
@@ -42,8 +46,6 @@ def test_render_builtin_startup(self) -> None:
         assert len(config.agents) == 5
 
     def test_render_all_builtins_produce_valid_root_config(self) -> None:
-        from ai_company.templates.loader import BUILTIN_TEMPLATES
-
         for name in BUILTIN_TEMPLATES:
             loaded = load_template(name)
             config = render_template(loaded)
@@ -310,7 +312,7 @@ def test_inline_personality_applied(self) -> None:
                 "communication_style": "custom",
             },
         }
-        result = _expand_single_agent(agent, 0, set())
+        result = _expand_single_agent(agent, 0, set(), has_extends=False)
         assert result["personality"]["communication_style"] == "custom"
         assert "custom-trait" in result["personality"]["traits"]
 
@@ -393,7 +395,7 @@ def test_invalid_inline_personality_raises_template_render_error(self) -> None:
             "personality": {"openness": 99.0},
         }
         with pytest.raises(TemplateRenderError, match="Invalid inline personality"):
-            _expand_single_agent(agent, 0, set())
+            _expand_single_agent(agent, 0, set(), has_extends=False)
 
     def test_non_dict_personality_raises_template_render_error(self) -> None:
         """Non-dict personality value raises TemplateRenderError."""
@@ -404,7 +406,7 @@ def test_non_dict_personality_raises_template_render_error(self) -> None:
             "personality": "not-a-dict",
         }
         with pytest.raises(TemplateRenderError, match="must be a mapping"):
-            _expand_single_agent(agent, 0, set())
+            _expand_single_agent(agent, 0, set(), has_extends=False)
 
 
 @pytest.mark.unit
@@ -414,7 +416,7 @@ def test_missing_role_raises_template_render_error(self) -> None:
         from ai_company.templates.renderer import _expand_single_agent
 
         with pytest.raises(TemplateRenderError, match="missing required 'role'"):
-            _expand_single_agent({}, 0, set())
+            _expand_single_agent({}, 0, set(), has_extends=False)
 
 
 @pytest.mark.unit
@@ -486,7 +488,7 @@ def test_unknown_preset_raises_template_render_error(self) -> None:
             "personality_preset": "does_not_exist",
         }
         with pytest.raises(TemplateRenderError, match="Unknown personality preset"):
-            _expand_single_agent(agent, 0, set())
+            _expand_single_agent(agent, 0, set(), has_extends=False)
 
 
 @pytest.mark.unit
@@ -506,3 +508,40 @@ def test_non_dict_item_raises(self) -> None:
 
         with pytest.raises(TemplateRenderError, match="must be a mapping"):
             _validate_list({"agents": [{"role": "Dev"}, "bad"]}, "agents")
+
+
+# ── Roster count tests ──────────────────────────────────────────
+
+
+@pytest.mark.unit
+class TestRosterCounts:
+    @pytest.mark.parametrize("name", sorted(BUILTIN_TEMPLATES))
+    def test_template_agent_count_in_range(self, name: str) -> None:
+        """Each template renders agents within its declared metadata range."""
+        loaded = load_template(name)
+        config = render_template(loaded)
+        lo = loaded.template.metadata.min_agents
+        hi = loaded.template.metadata.max_agents
+        assert lo <= len(config.agents) <= hi, (
+            f"{name}: expected {lo}-{hi} agents, got {len(config.agents)}"
+        )
+        assert isinstance(config, RootConfig)
+
+    def test_full_company_variable_override(self) -> None:
+        """full_company num_backend_devs override changes agent count."""
+        loaded = load_template("full_company")
+        default_config = render_template(loaded)
+        override_config = render_template(
+            loaded,
+            variables={"num_backend_devs": 5},
+        )
+        # Default is 3 backend devs, override is 5 → +2 agents.
+        default_backend = sum(
+            1 for a in default_config.agents if a.role == "Backend Developer"
+        )
+        override_backend = sum(
+            1 for a in override_config.agents if a.role == "Backend Developer"
+        )
+        assert default_backend == 3
+        assert override_backend == 5
+        assert override_backend - default_backend == 2
diff --git a/tests/unit/templates/test_schema.py b/tests/unit/templates/test_schema.py
index 78fa890f5e..f0333c2763 100644
--- a/tests/unit/templates/test_schema.py
+++ b/tests/unit/templates/test_schema.py
@@ -124,6 +124,14 @@ def test_both_personality_and_preset_rejected(self) -> None:
                 personality={"openness": 0.9},
             )
 
+    def test_remove_alias(self) -> None:
+        a = TemplateAgentConfig(role="Dev", _remove=True)
+        assert a.remove is True
+
+    def test_remove_default_false(self) -> None:
+        a = TemplateAgentConfig(role="Dev")
+        assert a.remove is False
+
 
 # ── TemplateDepartmentConfig ─────────────────────────────────────
 
@@ -406,6 +414,27 @@ def test_escalation_paths_accepted(
         )
         assert len(t.escalation_paths) == 1
 
+    def test_extends_field_accepted(
+        self,
+        make_template_dict: Callable[..., dict[str, Any]],
+    ) -> None:
+        t = CompanyTemplate(**make_template_dict(extends="startup", agents=()))
+        assert t.extends == "startup"
+
+    def test_extends_normalizes_case(
+        self,
+        make_template_dict: Callable[..., dict[str, Any]],
+    ) -> None:
+        t = CompanyTemplate(**make_template_dict(extends="  StartUp  ", agents=()))
+        assert t.extends == "startup"
+
+    def test_extends_skips_agent_count_validation(
+        self,
+        make_template_dict: Callable[..., dict[str, Any]],
+    ) -> None:
+        t = CompanyTemplate(**make_template_dict(extends="startup", agents=()))
+        assert len(t.agents) == 0
+
     def test_frozen(
         self,
         make_template_dict: Callable[..., dict[str, Any]],