Fix worker templates: add pydantic to pip_install and add_local_file for simulation.py

Discovered during GA test app migration that all three worker image
templates were missing pydantic in pip_install (simulation.py uses it
at module level) and add_local_file for simulation.py (Modal only
auto-mounts module-level imports). Also adds architecture validator
checks and scaffold checklist items for both.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: anth-volk

agents/dashboard/backend-builder.md

@@ -263,13 +263,16 @@ Generate `backend/app.py`. Only `modal` at module level. Imports business logic
 
 ```python
 import modal
+from pathlib import Path
 from _image_setup import snapshot_models
 
+_BACKEND_DIR = Path(__file__).parent
 app = modal.App("DASHBOARD_NAME-workers")
 image = (
     modal.Image.debian_slim(python_version="3.11")
-    .pip_install("policyengine-us==LATEST_VERSION")  # Pinned — looked up from PyPI in Step 1
+    .pip_install("policyengine-us==LATEST_VERSION", "pydantic")  # Pinned — looked up from PyPI in Step 1
     .run_function(snapshot_models)
+    .add_local_file(str(_BACKEND_DIR / "simulation.py"), remote_path="/root/simulation.py")
 )
 
 @app.function(image=image, cpu=8.0, memory=32768, timeout=3600)

agents/dashboard/dashboard-architecture-validator.md

@@ -133,6 +133,18 @@ grep -n 'run_function' backend/app.py
 # Should find the snapshot call
 ```
 
+**app.py must include pydantic in pip_install (simulation.py uses it at module level):**
+```bash
+grep -n 'pydantic' backend/app.py
+# Should find "pydantic" in the .pip_install() call
+```
+
+**app.py must include add_local_file for simulation.py (not auto-mounted):**
+```bash
+grep -n 'add_local_file.*simulation' backend/app.py
+# Should find the .add_local_file() call — Modal only auto-mounts module-level imports
+```
+
 **simulation.py must have policyengine imports at module level (snapshotted):**
 ```bash
 grep -n '^from policyengine\|^import policyengine' backend/simulation.py

agents/dashboard/dashboard-scaffold.md

@@ -587,6 +587,8 @@ If either fails, fix before proceeding.
 - [ ] If custom-modal: `app.py` only imports `modal` at module level
 - [ ] If custom-modal: `simulation.py` has policyengine imports at module level (snapshotted)
 - [ ] If custom-modal: image uses `.run_function(snapshot_models)` for fast cold starts
+- [ ] If custom-modal: worker image `pip_install` includes `"pydantic"` (simulation.py uses it at module level)
+- [ ] If custom-modal: worker image uses `.add_local_file()` for `simulation.py` (not auto-mounted since it's imported inside function bodies)
 - [ ] If custom-modal: gateway is lightweight (no policyengine in its Modal image)
 - [ ] If custom-modal: gateway image explicitly includes `pydantic`
 - [ ] If custom-modal: workers have `cpu=8.0`, `memory=32768`, `timeout >= 3600`

changelog.d/modal-three-file-backend.changed.md

@@ -1 +1 @@
-Pattern C (custom-modal) backend now uses three-file structure mirroring api-v2: _image_setup.py (snapshot), app.py (Modal decorators), simulation.py (pure logic). Adds .run_function() for fast cold starts, cpu=8.0/memory=32768 resource specs, and architecture validator check #6 for Modal backend structure.
+Pattern C (custom-modal) backend now uses three-file structure mirroring api-v2: _image_setup.py (snapshot), app.py (Modal decorators), simulation.py (pure logic). Adds .run_function() for fast cold starts, cpu=8.0/memory=32768 resource specs, explicit pydantic in worker pip_install, .add_local_file() for simulation.py mounting, and architecture validator check #6 for Modal backend structure.

commands/new-tool.md

@@ -212,13 +212,16 @@ Create `backend/app.py` (worker app, only `modal` at module level):
 
 ```python
 import modal
+from pathlib import Path
 from _image_setup import snapshot_models
 
+_BACKEND_DIR = Path(__file__).parent
 app = modal.App("TOOL_NAME-workers")
 image = (
     modal.Image.debian_slim(python_version="3.11")
-    .pip_install("policyengine-us==LATEST_VERSION")
+    .pip_install("policyengine-us==LATEST_VERSION", "pydantic")
     .run_function(snapshot_models)
+    .add_local_file(str(_BACKEND_DIR / "simulation.py"), remote_path="/root/simulation.py")
 )
 
 @app.function(image=image, cpu=8.0, memory=32768, timeout=3600)

skills/tools-and-apis/policyengine-interactive-tools-skill/SKILL.md

@@ -193,13 +193,16 @@ Only `modal` at module level. Imports business logic **inside each function body
 
 ```python
 import modal
+from pathlib import Path
 from _image_setup import snapshot_models
 
 app = modal.App("my-tool-workers")
+_BACKEND_DIR = Path(__file__).parent
 image = (
     modal.Image.debian_slim(python_version="3.11")
-    .pip_install("policyengine-us==X.Y.Z")  # Pin to latest — look up from PyPI
+    .pip_install("policyengine-us==X.Y.Z", "pydantic")  # Pin to latest — look up from PyPI
     .run_function(snapshot_models)
+    .add_local_file(str(_BACKEND_DIR / "simulation.py"), remote_path="/root/simulation.py")
 )
 
 @app.function(image=image, cpu=8.0, memory=32768, timeout=3600)