feat: pass AGENTEX_DEPLOYMENT_ID in registration metadata (#305)

* feat: pass AGENTEX_DEPLOYMENT_ID in registration metadata

Read AGENTEX_DEPLOYMENT_ID env var at startup and include it as
deployment_id in registration_metadata when calling POST /agents/register.
This links the agent pod to its deployment record in the Agentex backend,
enabling versioned deployments, preview routing, and promotion.

When the env var is not set, behavior is identical to before.

* style: add comment explaining or None coercion

Author: smoreinis

src/agentex/lib/environment_variables.py

@@ -39,6 +39,8 @@ class EnvVarKeys(str, Enum):
     # Build Information
     BUILD_INFO_PATH = "BUILD_INFO_PATH"
     AGENT_INPUT_TYPE = "AGENT_INPUT_TYPE"
+    # Deployment
+    AGENTEX_DEPLOYMENT_ID = "AGENTEX_DEPLOYMENT_ID"
     # Claude Agents SDK Configuration
     ANTHROPIC_API_KEY = "ANTHROPIC_API_KEY"
     CLAUDE_WORKSPACE_ROOT = "CLAUDE_WORKSPACE_ROOT"
@@ -78,6 +80,8 @@ class EnvironmentVariables(BaseModel):
     AUTH_PRINCIPAL_B64: str | None = None
     # Build Information
     BUILD_INFO_PATH: str | None = None
+    # Deployment
+    AGENTEX_DEPLOYMENT_ID: str | None = None
     # Claude Agents SDK Configuration
     ANTHROPIC_API_KEY: str | None = None
     CLAUDE_WORKSPACE_ROOT: str | None = None  # Defaults to project/workspace if not set

src/agentex/lib/utils/registration.py

@@ -44,14 +44,19 @@ async def register_agent(env_vars: EnvironmentVariables):
         or f"Generic description for agent: {env_vars.AGENT_NAME}"
     )
 
+    # Build registration metadata from build-info.json + deployment env var
+    registration_metadata = get_build_info() or {}
+    if env_vars.AGENTEX_DEPLOYMENT_ID:
+        registration_metadata["deployment_id"] = env_vars.AGENTEX_DEPLOYMENT_ID
+
     # Prepare registration data
     registration_data = {
         "name": env_vars.AGENT_NAME,
         "description": description,
         "acp_url": full_acp_url,
         "acp_type": env_vars.ACP_TYPE,
         "principal_context": get_auth_principal(env_vars),
-        "registration_metadata": get_build_info()
+        "registration_metadata": registration_metadata or None,  # Send null instead of {} when no metadata
     }
 
     if env_vars.AGENT_ID: