fix(runtime): align PLATFORM_URL default to host.docker.internal across all modules

Unified the fallback default for PLATFORM_URL from `http://platform:8080`
(Docker Compose service name) to `http://host.docker.internal:8080`
across all 13 modules that declare it. This matches:
- The provisioner's default (buildContainerEnv injects PLATFORM_URL
  from cfg.PlatformURL, which defaults to host.docker.internal on the
  platform side — main.go:platformURL)
- The molecule-git-token-helper.sh script (already uses host.docker.internal)
- The MCP client (MOLECULE_URL injected by provisioner)

The provisioner always sets PLATFORM_URL in production containers, so
this is a development/Docker-only improvement: without this change,
a workspace started outside the Docker Compose network (e.g. via
`docker run` with `--network host`) would fail platform API calls
with "Connection refused" because `platform:8080` resolves nowhere.

13 modules updated: a2a_cli, a2a_client, a2a_mcp_server, adapters/base,
builtin_tools/a2a_tools, builtin_tools/approval, builtin_tools/delegation,
builtin_tools/hitl, builtin_tools/memory, consolidation, coordinator,
main, molecule_ai_status. All docstrings updated to match.

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

molecule_runtime/a2a_cli.py

@@ -24,7 +24,7 @@ import httpx
 from builtin_tools.validation import WorkspaceIdValidationError, get_validated_workspace_id
 
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")  # used for discover() headers only; URL uses validated version
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 
 
 async def discover(target_id: str) -> dict | None:

molecule_runtime/a2a_client.py

@@ -16,7 +16,7 @@ from .platform_auth import auth_headers
 logger = logging.getLogger(__name__)
 
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform: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] = {}

molecule_runtime/a2a_mcp_server.py

@@ -14,7 +14,7 @@ the claude --print invocation.
 
 Environment variables (set by the workspace container):
   WORKSPACE_ID  — this workspace's ID
-  PLATFORM_URL  — platform API base URL (e.g. http://platform:8080)
+  PLATFORM_URL  — platform API base URL (default: http://host.docker.internal:8080)
 """
 
 import argparse

molecule_runtime/adapters/base.py

@@ -229,7 +229,7 @@ class BaseAdapter(ABC):
         from builtin_tools.memory import commit_memory, search_memory
         from builtin_tools.sandbox import run_code
 
-        platform_url = os.environ.get("PLATFORM_URL", "http://platform:8080")
+        platform_url = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 
         # Load plugins from per-workspace dir first, then shared fallback
         workspace_plugins_dir = os.path.join(config.config_path, "plugins")

molecule_runtime/builtin_tools/a2a_tools.py

@@ -11,7 +11,7 @@ import httpx
 
 from builtin_tools.validation import WorkspaceIdValidationError, get_validated_workspace_id
 
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")  # used only for tracing headers; URLs use validated version
 
 

molecule_runtime/builtin_tools/approval.py

@@ -32,7 +32,7 @@ RBAC denials emit an ``rbac / rbac.deny / denied`` event instead.
 
 Environment variables
 ---------------------
-PLATFORM_URL            Platform base URL            (default: http://platform:8080)
+PLATFORM_URL            Platform base URL            (default: http://host.docker.internal:8080)
 WORKSPACE_ID            This workspace's ID (validated at startup by platform_auth)
 APPROVAL_TIMEOUT        Max wait in seconds          (default: 300)
 APPROVAL_POLL_INTERVAL  Polling interval in seconds  (default: 5, polling path only)
@@ -55,7 +55,7 @@ from builtin_tools.validation import WorkspaceIdValidationError, get_validated_w
 
 logger = logging.getLogger(__name__)
 
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 from molecule_runtime.platform_auth import WORKSPACE_ID
 APPROVAL_POLL_INTERVAL = float(os.environ.get("APPROVAL_POLL_INTERVAL", "5"))
 APPROVAL_TIMEOUT = float(os.environ.get("APPROVAL_TIMEOUT", "300"))

molecule_runtime/builtin_tools/delegation.py

@@ -30,7 +30,7 @@ from builtin_tools.telemetry import (
     inject_trace_headers,
 )
 
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 from molecule_runtime.platform_auth import WORKSPACE_ID
 DELEGATION_RETRY_ATTEMPTS = int(os.environ.get("DELEGATION_RETRY_ATTEMPTS", "3"))
 DELEGATION_RETRY_DELAY = float(os.environ.get("DELEGATION_RETRY_DELAY", "5.0"))

molecule_runtime/builtin_tools/hitl.py

@@ -177,7 +177,7 @@ async def _notify_channels(
     Errors in individual channels are logged but never re-raised so that a
     misconfigured Slack webhook cannot block the approval flow.
     """
-    platform_url = os.environ.get("PLATFORM_URL", "http://platform:8080")
+    platform_url = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
     workspace_id = os.environ.get("WORKSPACE_ID", "")
 
     for channel in cfg.channels:

molecule_runtime/builtin_tools/memory.py

@@ -42,7 +42,7 @@ try:  # pragma: no cover - optional runtime dependency in lightweight test envs
 except ImportError:  # pragma: no cover
     httpx = SimpleNamespace(AsyncClient=None)
 
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")
 
 

molecule_runtime/consolidation.py

@@ -19,7 +19,7 @@ from .platform_auth import auth_headers
 
 logger = logging.getLogger(__name__)
 
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")
 CONSOLIDATION_INTERVAL = float(os.environ.get("CONSOLIDATION_INTERVAL", "300"))  # 5 min
 CONSOLIDATION_THRESHOLD = int(os.environ.get("CONSOLIDATION_THRESHOLD", "10"))  # min memories before consolidating

molecule_runtime/coordinator.py

@@ -23,7 +23,7 @@ from policies.routing import build_team_routing_payload
 
 logger = logging.getLogger(__name__)
 
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")
 
 

molecule_runtime/main.py

@@ -63,7 +63,7 @@ from transcript_auth import transcript_authorized as _transcript_authorized
 async def main():  # pragma: no cover
     workspace_id = os.environ.get("WORKSPACE_ID", "workspace-default")
     config_path = os.environ.get("WORKSPACE_CONFIG_PATH", "/configs")
-    platform_url = os.environ.get("PLATFORM_URL", "http://platform:8080")
+    platform_url = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
     awareness_config = get_awareness_config()
 
     # 0. Normalise LLM auth env vars based on token type.

molecule_runtime/molecule_ai_status.py

@@ -25,7 +25,7 @@ import httpx
 from builtin_tools.validation import WorkspaceIdValidationError, get_validated_workspace_id
 
 WORKSPACE_ID = os.environ.get("WORKSPACE_ID", "")
-PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://platform:8080")
+PLATFORM_URL = os.environ.get("PLATFORM_URL", "http://host.docker.internal:8080")
 
 
 def set_status(task: str):