fix(macos): name the gateway instead of addressing it, so bottles survive it moving

The shared gateway's address is DHCP-assigned and changes whenever the infra
container is recreated — a source-hash bump, an image upgrade, a crash. Every
agent-facing URL embedded that address, and the proxy URL reaches the agent
as process environment at `container exec` time. A running process's environ
cannot be rewritten from outside, so a moved gateway stranded every running
bottle permanently: not degraded, unreachable, until relaunched and its agent
session thrown away.

Give the agent a stable name instead. `GATEWAY_HOSTNAME` replaces the address
in the egress proxy URL, NO_PROXY, git-http, and supervise URLs, and resolves
through the bottle's own /etc/hosts. Unlike environ that is a file, so it can
be rewritten inside a container that is already running — which is the whole
point: a gateway that returns at a new address is picked up by live bottles.

Launch writes the entry before anything execs (every agent URL names the
gateway, so it must resolve for the first connection), and re-points every
running bottle once the gateway is up, so one stranded by an earlier restart
re-attaches instead of needing a relaunch.

The write needs root and the agent runs as `node`: the host can repoint a
bottle's gateway name, the agent cannot repoint its own. Keep that asymmetry.

Apple Container 1.0 has no container-name DNS on a user network and
`container run` has no --add-host, so the entry is written by exec after
start rather than declared at run.

Does not address the other half of #443: per-bottle egress auth tokens are
held in memory by the orchestrator and are still lost across a restart, so a
re-attached bottle resolves its policy but not its injected credentials.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/macos_container/enumerate.py

@@ -8,7 +8,11 @@ from ...bottle_state import read_metadata
 from .. import ActiveAgent
 from .infra import INFRA_NAME
 
-_PREFIX = "bot-bottle-"
+# The name every agent container carries: `bot-bottle-<slug>`. Exported
+# because callers that act on a running bottle (gateway-host rewrites,
+# registry reconciliation) have to map an enumerated slug back to a
+# container name.
+CONTAINER_NAME_PREFIX = "bot-bottle-"
 # The shared per-host infra container carries the same prefix as agent
 # containers but is infrastructure, not a bottle — one control plane + gateway
 # serves every agent, so listing it as an agent would invent one per host.
@@ -26,9 +30,9 @@ def enumerate_active() -> list[ActiveAgent]:
         return []
     out: list[ActiveAgent] = []
     for name in sorted(line.strip() for line in result.stdout.splitlines()):
-        if not name.startswith(_PREFIX) or name in _INFRA_NAMES:
+        if not name.startswith(CONTAINER_NAME_PREFIX) or name in _INFRA_NAMES:
             continue
-        slug = name[len(_PREFIX):]
+        slug = name[len(CONTAINER_NAME_PREFIX):]
         metadata = read_metadata(slug)
         out.append(ActiveAgent(
             backend_name="macos-container",

bot_bottle/backend/macos_container/gateway_hosts.py

@@ -0,0 +1,96 @@
+"""Stable gateway name for macOS agents, via each bottle's `/etc/hosts`.
+
+The shared gateway's address is assigned by vmnet's DHCP and changes whenever
+the infra container is recreated — a source-hash bump, an image upgrade, a
+crash. Every agent-facing URL (egress proxy, git-http, supervise) embeds that
+address, and the proxy URL reaches the agent as **process environment** at
+`container exec` time. A running process's `environ` cannot be rewritten from
+outside, so a moved gateway used to strand every running bottle permanently:
+not degraded, unreachable, until the bottle was relaunched and its session
+thrown away.
+
+So the agent never learns the address. It is given a stable *name*
+(`GATEWAY_HOSTNAME`) in every URL, resolved through its own `/etc/hosts`.
+Unlike `environ`, that is a file — it can be rewritten inside a container that
+is already running, so a gateway that comes back at a new address is picked up
+by live bottles instead of orphaning them.
+
+Apple Container 1.0 offers no container-name DNS on a user network (the only
+nameserver an agent sees is vmnet's, which does not know container names) and
+`container run` has no `--add-host`, so the entry is written by exec after the
+container starts.
+
+Writing it needs root, and the agent runs as `node`: the agent therefore
+cannot repoint its own gateway name, while the host (which drives `container
+exec --user root`) can. That asymmetry is deliberate — keep it.
+"""
+
+from __future__ import annotations
+
+from ...log import warn
+from . import util as container_mod
+from .enumerate import CONTAINER_NAME_PREFIX, enumerate_active
+
+# The name every agent-facing gateway URL uses. Must not collide with a real
+# DNS name the agent might resolve; it is bottle-local by construction.
+GATEWAY_HOSTNAME = "bot-bottle-gateway"
+
+# Marker so the rewrite is idempotent and only ever touches our own line —
+# the rest of /etc/hosts (localhost, the container's own name) is preserved.
+_MARKER = "# bot-bottle gateway"
+
+
+def _rewrite_script(gateway_ip: str) -> str:
+    """A shell one-liner that replaces our managed line in `/etc/hosts`.
+
+    Rewrites in place via a temp file + `cat` rather than `mv`, so the file
+    keeps its original inode, ownership, and mode — a bind-mounted or
+    pre-created `/etc/hosts` must not be replaced by a root-owned 0644 copy
+    that the runtime then refuses to update.
+    """
+    return (
+        "set -e; "
+        f"grep -v '{_MARKER}' /etc/hosts > /tmp/.bb-hosts || true; "
+        f"printf '%s %s %s\\n' '{gateway_ip}' '{GATEWAY_HOSTNAME}' "
+        f"'{_MARKER}' >> /tmp/.bb-hosts; "
+        "cat /tmp/.bb-hosts > /etc/hosts; "
+        "rm -f /tmp/.bb-hosts"
+    )
+
+
+def set_gateway_host(container_name: str, gateway_ip: str) -> None:
+    """Point `GATEWAY_HOSTNAME` at `gateway_ip` inside one running container.
+
+    Must run before the agent is exec'd: the agent's proxy URL names the
+    gateway, so the entry has to exist for its first connection. Idempotent —
+    re-running with the same address is a no-op in effect.
+    """
+    container_mod.exec_container_as_root(
+        container_name, ["sh", "-c", _rewrite_script(gateway_ip)],
+    )
+
+
+def refresh_gateway_host(gateway_ip: str) -> list[str]:
+    """Re-point every running bottle at the current gateway address.
+
+    Called once the shared gateway is known to be up, so a bottle stranded by
+    an earlier gateway restart re-attaches instead of needing a relaunch.
+    Returns the containers updated.
+
+    Best-effort per bottle: one container that refuses the write (already
+    exiting, say) must not stop the others from being repaired, and must not
+    fail the launch that triggered the sweep.
+    """
+    updated: list[str] = []
+    for agent in enumerate_active():
+        name = f"{CONTAINER_NAME_PREFIX}{agent.slug}"
+        try:
+            set_gateway_host(name, gateway_ip)
+            updated.append(name)
+        # One bad bottle must not stop the sweep, so this is deliberately broad.
+        except Exception as e:  # noqa: BLE001  # pylint: disable=broad-exception-caught
+            warn(f"could not re-point {name} at the gateway: {e}")
+    return updated
+
+
+__all__ = ["GATEWAY_HOSTNAME", "set_gateway_host", "refresh_gateway_host"]

bot_bottle/backend/macos_container/launch.py

@@ -59,6 +59,11 @@ from ..docker.egress import EGRESS_PORT
 from ..util import AGENT_CA_BUNDLE, AGENT_CA_PATH
 from . import util as container_mod
 from .bottle import MacosContainerBottle
+from .gateway_hosts import (
+    GATEWAY_HOSTNAME,
+    refresh_gateway_host,
+    set_gateway_host,
+)
 from .bottle_plan import MacosContainerBottlePlan
 from .consolidated_launch import (
     GatewayEndpoint,
@@ -100,6 +105,11 @@ def launch(
         # Step 1: the per-host singletons. Must precede the agent run — its
         # proxy env needs the gateway's address at `container run` time.
         endpoint = ensure_gateway()
+        # The gateway's address may have changed since these bottles launched
+        # (any infra recreate re-runs DHCP). They name the gateway rather than
+        # address it, so re-pointing /etc/hosts re-attaches them in place
+        # instead of leaving them stranded until relaunch.
+        refresh_gateway_host(endpoint.gateway_ip)
 
         # Step 2: mint this bottle's deploy keys, then point it at the SHARED
         # gateway's CA + git-http/supervise ports.
@@ -117,6 +127,9 @@ def launch(
         # attribution key; `--cap-drop CAP_NET_RAW` at run is what makes it
         # unforgeable. Poll: `container run --detach` can return before vmnet's
         # DHCP has assigned the address.
+        # Resolve the gateway name before anything execs: every agent-facing
+        # URL uses it, so the entry must exist for the first connection.
+        set_gateway_host(plan.container_name, endpoint.gateway_ip)
         source_ip = container_mod.wait_container_ipv4_on_network(
             plan.container_name, endpoint.network,
         )
@@ -231,13 +244,20 @@ def _stamp_agent_urls(
 ) -> MacosContainerBottlePlan:
     """Point the agent's git-gate insteadOf rewrites + supervise MCP at the
     shared gateway's ports. Both bypass the egress proxy (NO_PROXY covers the
-    gateway address)."""
+    gateway name).
+
+    Addressed by `GATEWAY_HOSTNAME`, never by IP: these URLs are baked into
+    the agent's gitconfig and MCP config at provision time, so an address here
+    would strand the bottle the moment the gateway moved. The name is resolved
+    per connection through `/etc/hosts`, which stays rewritable while the
+    bottle runs."""
+    del endpoint  # addressed by name; the address reaches the bottle via /etc/hosts
     git_gate_url = (
-        f"http://{endpoint.gateway_ip}:{_GIT_HTTP_PORT}"
+        f"http://{GATEWAY_HOSTNAME}:{_GIT_HTTP_PORT}"
         if plan.git_gate_plan.upstreams else ""
     )
     supervise_url = (
-        f"http://{endpoint.gateway_ip}:{SUPERVISE_PORT}/"
+        f"http://{GATEWAY_HOSTNAME}:{SUPERVISE_PORT}/"
         if plan.supervise_plan is not None else ""
     )
     return dataclasses.replace(
@@ -247,19 +267,25 @@ def _stamp_agent_urls(
     )
 
 
-def _proxy_url(gateway_ip: str, identity_token: str = "") -> str:
+def _proxy_url(identity_token: str = "") -> str:
     """The agent's egress proxy URL. The identity token rides as proxy
     credentials — the gateway reads Proxy-Authorization, resolves the
     (source_ip, token) pair against the control plane, and strips it before
-    upstream. Without a valid pair `/resolve` denies the request (#366)."""
+    upstream. Without a valid pair `/resolve` denies the request (#366).
+
+    Names the gateway rather than addressing it: this URL reaches the agent as
+    process environment, which cannot be rewritten once the agent is running,
+    so an address baked here is unfixable if the gateway moves."""
     cred = f"bottle:{identity_token}@" if identity_token else ""
-    return f"http://{cred}{gateway_ip}:{EGRESS_PORT}"
+    return f"http://{cred}{GATEWAY_HOSTNAME}:{EGRESS_PORT}"
 
 
-def _no_proxy(gateway_ip: str) -> str:
+def _no_proxy() -> str:
     # git-http + supervise live on the gateway and must NOT go through the
-    # egress proxy — the agent reaches them directly by its address.
-    return f"localhost,127.0.0.1,{gateway_ip}"
+    # egress proxy — the agent reaches them directly by name. Deliberately
+    # address-free: NO_PROXY is baked into the run-time env and is therefore
+    # just as unfixable as the proxy URL if the gateway moves.
+    return f"localhost,127.0.0.1,{GATEWAY_HOSTNAME}"
 
 
 def _identity_proxy_env(
@@ -276,7 +302,8 @@ def _identity_proxy_env(
     `_agent_env_entries`."""
     if not identity_token:
         return {}
-    url = _proxy_url(endpoint.gateway_ip, identity_token)
+    del endpoint  # the gateway is named, not addressed
+    url = _proxy_url(identity_token)
     return {
         "HTTPS_PROXY": url, "HTTP_PROXY": url,
         "https_proxy": url, "http_proxy": url,
@@ -338,7 +365,7 @@ def _agent_env_entries(
     # silently dropping attribution for. Without it a process that egresses
     # before the exec-time env still fails closed — the agent network is
     # host-only, so there is no route off it except the gateway.
-    no_proxy = _no_proxy(endpoint.gateway_ip)
+    no_proxy = _no_proxy()
     env = [
         f"NO_PROXY={no_proxy}",
         f"no_proxy={no_proxy}",

bot_bottle/backend/macos_container/util.py

@@ -360,6 +360,21 @@ def exec_container(name: str, argv: list[str]) -> None:
         )
 
 
+def exec_container_as_root(name: str, argv: list[str]) -> None:
+    """`exec_container`, but as uid 0 inside the container.
+
+    For host-driven maintenance the agent itself must not be able to perform —
+    rewriting `/etc/hosts` to point the gateway name at an address. The agent
+    runs as `node`, so it cannot repoint its own gateway; the host can.
+    """
+    result = _run_container_op([_CONTAINER, "exec", "--user", "root", name, *argv])
+    if result.returncode != 0:
+        die(
+            f"container exec (root) in {name} failed: "
+            f"{(result.stderr or '').strip() or '<no stderr>'}"
+        )
+
+
 def _run_container_op(cmd: list[str]) -> subprocess.CompletedProcess[str]:
     result = subprocess.run(
         cmd,