feat: modal tool execution - NO FEATURE FLAGS USES MODAL [LET-4357] (#5120)

* initial commit

* add delay to deploy

* fix tests

* add tests

* passing tests

* cleanup

* and use modal

* working on modal

* gate on tool metadata

* agent state

* cleanup

---------

Co-authored-by: Letta Bot <noreply@letta.com>

letta/helpers/tool_helpers.py

@@ -0,0 +1,69 @@
+import hashlib
+
+from letta.constants import MODAL_VERSION_HASH_LENGTH
+from letta.schemas.tool import Tool
+
+
+def _serialize_dependencies(tool: Tool) -> str:
+    """
+    Serialize dependencies in a consistent way for hashing.
+    TODO: This should be improved per LET-3770 to ensure consistent ordering.
+    For now, we convert to string representation.
+    """
+    parts = []
+
+    if tool.pip_requirements:
+        # TODO: Sort these consistently
+        parts.append(f"pip:{str(tool.pip_requirements)}")
+
+    if tool.npm_requirements:
+        # TODO: Sort these consistently
+        parts.append(f"npm:{str(tool.npm_requirements)}")
+
+    return ";".join(parts)
+
+
+def compute_tool_hash(tool: Tool):
+    """
+    Calculate a hash representing the current version of the tool and configuration.
+    This hash changes when:
+    - Tool source code changes
+    - Tool dependencies change
+    - Sandbox configuration changes
+    - Language/runtime changes
+    """
+    components = [
+        tool.source_code if tool.source_code else "",
+        tool.source_type if tool.source_type else "",
+        _serialize_dependencies(tool),
+    ]
+
+    combined = "|".join(components)
+    return hashlib.sha256(combined.encode()).hexdigest()[:MODAL_VERSION_HASH_LENGTH]
+
+
+def generate_modal_function_name(tool_name: str, organization_id: str, project_id: str = "default") -> str:
+    """
+    Generate a Modal function name from tool name and project ID.
+    Shortens the project ID to just the prefix and first UUID segment.
+
+    Args:
+        tool_name: Name of the tool
+        organization_id: Full organization ID (not used in function name, but kept for future use)
+        project_id: Project ID (e.g., project-12345678-90ab-cdef-1234-567890abcdef or "default")
+
+    Returns:
+        Modal function name (e.g., tool_name_project-12345678 or tool_name_default)
+    """
+    from letta.constants import MAX_TOOL_NAME_LENGTH
+
+    max_tool_name_length = 64
+
+    # Shorten the organization_id to just the first segment (e.g., project-12345678)
+    short_organization_id = organization_id[: (max_tool_name_length - MAX_TOOL_NAME_LENGTH - 1)]
+
+    # make extra sure the tool name is not too long
+    name = f"{tool_name[:MAX_TOOL_NAME_LENGTH]}_{short_organization_id}"
+
+    # safe fallback
+    return name