fix(workspace): align PLATFORM_URL default to host.docker.internal

Remove Docker-detection localhost fallbacks across 5 workspace source files.
When PLATFORM_URL is unset the container always runs in Docker, so
host.docker.internal is the correct default — no local-dev fallback needed.

Files: a2a_cli.py, a2a_client.py, consolidation.py, coordinator.py, main.py

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace/a2a_cli.py

@@ -25,10 +25,7 @@ _WORKSPACE_ID_raw = os.environ.get("WORKSPACE_ID")
 if not _WORKSPACE_ID_raw:
     raise RuntimeError("WORKSPACE_ID environment variable is required but not set")
 WORKSPACE_ID = _WORKSPACE_ID_raw
-if os.path.exists("/.dockerenv") or os.environ.get("DOCKER_VERSION"):
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
-else:
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://localhost:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 
 
 async def discover(target_id: str) -> dict | None:

workspace/a2a_client.py

@@ -26,10 +26,7 @@ _WORKSPACE_ID_raw = os.environ.get("WORKSPACE_ID")
 if not _WORKSPACE_ID_raw:
     raise RuntimeError("WORKSPACE_ID environment variable is required but not set")
 WORKSPACE_ID = _WORKSPACE_ID_raw
-if os.path.exists("/.dockerenv") or os.environ.get("DOCKER_VERSION"):
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
-else:
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://localhost:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 
 # Cache workspace ID → name mappings (populated by list_peers calls)
 _peer_names: dict[str, str] = {}

workspace/consolidation.py

@@ -18,10 +18,7 @@ from platform_auth import auth_headers
 
 logger = logging.getLogger(__name__)
 
-if os.path.exists("/.dockerenv") or os.environ.get("DOCKER_VERSION"):
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
-else:
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://localhost:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 _WORKSPACE_ID_raw = os.environ.get("WORKSPACE_ID")
 if not _WORKSPACE_ID_raw:
     raise RuntimeError("WORKSPACE_ID environment variable is required but not set")

workspace/coordinator.py

@@ -22,10 +22,7 @@ from policies.routing import build_team_routing_payload
 
 logger = logging.getLogger(__name__)
 
-if os.path.exists("/.dockerenv") or os.environ.get("DOCKER_VERSION"):
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
-else:
-    PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://localhost:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 _WORKSPACE_ID_raw = os.environ.get("WORKSPACE_ID")
 if not _WORKSPACE_ID_raw:
     raise RuntimeError("WORKSPACE_ID environment variable is required but not set")

workspace/main.py

@@ -58,12 +58,7 @@ async def main():  # pragma: no cover
     if not workspace_id:
         raise SystemExit("FATAL: WORKSPACE_ID env var is not set. Aborting.")
     config_path = os.environ.get("WORKSPACE_CONFIG_PATH", "/configs")
-    # Docker-aware default — host.docker.internal resolves the platform service
-    # from inside the Docker network mesh; falls back to localhost for local dev.
-    if os.path.exists("/.dockerenv") or os.environ.get("DOCKER_VERSION"):
-        platform_url = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
-    else:
-        platform_url = os.environ.get("PLATFORM_URL", "http://localhost:8080")
+    platform_url = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
     awareness_config = get_awareness_config()
 
     # 0. Initialise OpenTelemetry (no-op if packages not installed)