Route browser fs and logs endpoints directly to the VM

src/kernel/_client.py

@@ -41,8 +41,11 @@
     strip_direct_vm_auth,
     rewrite_direct_vm_options,
     browser_routing_config_from_env,
+    is_stale_direct_vm_auth_response,
     should_retry_stale_direct_vm_auth,
+    install_stale_direct_vm_auth_eviction,
     maybe_evict_browser_route_from_response,
+    install_async_stale_direct_vm_auth_eviction,
     maybe_populate_browser_route_cache_from_response,
 )
 
@@ -203,6 +206,7 @@ def __init__(
         )
         self.browser_route_cache = _browser_route_cache or BrowserRouteCache()
         self._browser_routing = browser_routing_config_from_env()
+        install_stale_direct_vm_auth_eviction(self._client, cache=self.browser_route_cache)
 
     @cached_property
     def deployments(self) -> DeploymentsResource:
@@ -365,9 +369,11 @@ def _prepare_request(self, request: httpx.Request) -> None:
 
     @override
     def _should_retry(self, response: httpx.Response) -> bool:
-        if should_retry_stale_direct_vm_auth(response):
-            maybe_evict_browser_route_from_response(response, cache=self.browser_route_cache)
-            return True
+        if is_stale_direct_vm_auth_response(response):
+            # The route was already evicted by the response hook; retry only when
+            # the body can be rebuilt, otherwise the caller sees the original auth
+            # failure and a later call goes to the control plane.
+            return should_retry_stale_direct_vm_auth(response)
         return super()._should_retry(response)
 
     @override
@@ -586,6 +592,7 @@ def __init__(
         )
         self.browser_route_cache = _browser_route_cache or BrowserRouteCache()
         self._browser_routing = browser_routing_config_from_env()
+        install_async_stale_direct_vm_auth_eviction(self._client, cache=self.browser_route_cache)
 
     @cached_property
     def deployments(self) -> AsyncDeploymentsResource:
@@ -748,9 +755,11 @@ async def _prepare_request(self, request: httpx.Request) -> None:
 
     @override
     def _should_retry(self, response: httpx.Response) -> bool:
-        if should_retry_stale_direct_vm_auth(response):
-            maybe_evict_browser_route_from_response(response, cache=self.browser_route_cache)
-            return True
+        if is_stale_direct_vm_auth_response(response):
+            # The route was already evicted by the response hook; retry only when
+            # the body can be rebuilt, otherwise the caller sees the original auth
+            # failure and a later call goes to the control plane.
+            return should_retry_stale_direct_vm_auth(response)
         return super()._should_retry(response)
 
     @override

src/kernel/lib/browser_routing/routing.py

@@ -32,6 +32,9 @@ class BrowserRoutingConfig:
     subresources: tuple[str, ...] = field(default_factory=tuple)
 
 
+_EVICTION_HOOK_CACHE_ATTR = "_kernel_browser_route_cache"
+
+
 _BROWSER_ROUTE_CACHEABLE_PATH = re.compile(r"^/(?:v\d+/)?browsers(?:/[^/]+)?/?$")
 _BROWSER_DELETE_BY_ID_PATH = re.compile(r"^/(?:v\d+/)?browsers/([^/]+)/?$")
 _BROWSER_POOL_ACQUIRE_PATH = re.compile(r"^/(?:v\d+/)?browser_pools/[^/]+/acquire/?$")
@@ -44,7 +47,17 @@ def browser_routing_config_from_env() -> BrowserRoutingConfig:
         # Path prefixes eligible for direct-to-VM routing. "telemetry/stream" is
         # the live SSE endpoint (VM); "telemetry/events" is a historical read
         # served by the control plane (S2) and must NOT be here.
-        return BrowserRoutingConfig(subresources=("curl", "telemetry/stream", "computer", "playwright", "process"))
+        return BrowserRoutingConfig(
+            subresources=(
+                "curl",
+                "telemetry/stream",
+                "computer",
+                "playwright",
+                "process",
+                "fs",
+                "logs/stream",
+            )
+        )
     if raw.strip() == "":
         return BrowserRoutingConfig()
 
@@ -188,8 +201,122 @@ def is_stale_direct_vm_auth_response(response: httpx.Response) -> bool:
     return bool(response.request.url.params.get("jwt"))
 
 
+def install_stale_direct_vm_auth_eviction(client: httpx.Client, *, cache: BrowserRouteCache) -> None:
+    """Evict stale direct-to-VM routes as soon as the response status is known.
+
+    httpx reads the body of a non-streamed response inside `send()`, so a caller
+    that only inspects the returned response never learns the status of a 401/403
+    whose body read fails — the read error surfaces from `send()` instead and the
+    dead route would stay cached, wedging every later call for that session. A
+    response event hook runs after the status is known and before any body is
+    read, which keeps eviction independent of the body. It is prepended so that a
+    caller-supplied hook cannot pre-empt it by reading a failing body or raising.
+    """
+    hooks = client.event_hooks.setdefault("response", [])
+    if _has_eviction_hook(hooks, cache):
+        return
+
+    def evict(response: httpx.Response) -> None:
+        if is_stale_direct_vm_auth_response(response):
+            maybe_evict_browser_route_from_response(response, cache=cache)
+
+    setattr(evict, _EVICTION_HOOK_CACHE_ATTR, cache)
+    hooks.insert(0, evict)
+
+
+def install_async_stale_direct_vm_auth_eviction(client: httpx.AsyncClient, *, cache: BrowserRouteCache) -> None:
+    """Async counterpart of `install_stale_direct_vm_auth_eviction`."""
+    hooks = client.event_hooks.setdefault("response", [])
+    if _has_eviction_hook(hooks, cache):
+        return
+
+    async def evict(response: httpx.Response) -> None:
+        if is_stale_direct_vm_auth_response(response):
+            maybe_evict_browser_route_from_response(response, cache=cache)
+
+    setattr(evict, _EVICTION_HOOK_CACHE_ATTR, cache)
+    hooks.insert(0, evict)
+
+
+def _has_eviction_hook(hooks: list[Any], cache: BrowserRouteCache) -> bool:
+    # A copied client shares both the httpx client and the route cache, so the
+    # hook is registered once per cache instead of once per client.
+    return any(getattr(hook, _EVICTION_HOOK_CACHE_ATTR, None) is cache for hook in hooks)
+
+
 def should_retry_stale_direct_vm_auth(response: httpx.Response) -> bool:
-    return is_stale_direct_vm_auth_response(response)
+    """Whether a stale direct-to-VM auth failure can be retried on the control plane.
+
+    A retry rebuilds the request from the original options, so it is only safe when
+    the body can be serialized again byte for byte. Streamed bodies (e.g. a file
+    object passed to fs.write_file) are consumed by the direct request, so retrying
+    would send a truncated or empty body to the control plane.
+    """
+    if not is_stale_direct_vm_auth_response(response):
+        return False
+    return direct_vm_request_body_is_replayable(response.request)
+
+
+def direct_vm_request_body_is_replayable(request: httpx.Request) -> bool:
+    try:
+        _ = request.content
+    except httpx.RequestNotRead:
+        pass
+    else:
+        # httpx already buffered the body, so rebuilding it yields the same bytes.
+        return True
+
+    # httpx encodes multipart bodies as a stream of fields it re-renders per attempt.
+    fields = getattr(request.stream, "fields", None)
+    if fields is None:
+        # A streamed body (file object, iterator or async iterator) cannot be replayed.
+        return False
+    return all(_multipart_field_is_replayable(field) for field in cast("list[Any]", fields))
+
+
+def _multipart_field_is_replayable(field: Any) -> bool:
+    file = getattr(field, "file", None)
+    if file is None:
+        # A data field renders from an in-memory value.
+        return True
+    if isinstance(file, (bytes, str)):
+        return True
+    if getattr(file, "closed", False):
+        return False
+    return _rewind_succeeds(file)
+
+
+def _rewind_succeeds(file: Any) -> bool:
+    """Whether the file field can actually be rewound for another render.
+
+    `seekable()` is not proof: a wrapper can report True and still raise from
+    `seek()`, which would render the field as an empty part on the retry. The
+    only reliable check is to perform the rewind httpx would perform.
+    """
+    seek = getattr(file, "seek", None)
+    if not callable(seek):
+        return False
+
+    position: object = None
+    tell = getattr(file, "tell", None)
+    if callable(tell):
+        try:
+            position = tell()
+        except Exception:
+            position = None
+
+    try:
+        seek(0)
+    except Exception:
+        return False
+
+    if isinstance(position, int) and position > 0:
+        try:
+            seek(position)
+        except Exception:
+            # The field is left rewound, which is where httpx renders it from anyway.
+            pass
+    return True
 
 
 def _session_id_from_browser_delete_path(path: str) -> str | None:

src/kernel/lib/multipart.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from typing import Mapping, Sequence, cast
+
+from .._utils import is_given
+
+__all__ = ["indexed_multipart_body"]
+
+
+def indexed_multipart_body(body: object) -> dict[str, object]:
+    """Flatten a multipart body so that array entries carry their index.
+
+    Endpoints that take an array of objects with a file field need each entry's
+    fields grouped together: `files[0][dest_path]` pairs with the `files[0][file]`
+    part, while repeated `files[][dest_path]` names cannot be matched back to
+    their file. The returned mapping is already flat, so the client's generic
+    multipart serialization passes the names through untouched and every other
+    endpoint keeps its existing encoding.
+    """
+    flattened: dict[str, object] = {}
+    if isinstance(body, Mapping):
+        for key, value in cast(Mapping[object, object], body).items():
+            _flatten(str(key), value, flattened)
+    return flattened
+
+
+def _flatten(key: str, value: object, out: dict[str, object]) -> None:
+    if not is_given(value):
+        return
+
+    if isinstance(value, Mapping):
+        for child_key, child in cast(Mapping[object, object], value).items():
+            _flatten(f"{key}[{child_key}]", child, out)
+        return
+
+    if isinstance(value, (list, tuple)):
+        for index, child in enumerate(cast(Sequence[object], value)):
+            _flatten(f"{key}[{index}]", child, out)
+        return
+
+    out[key] = value

src/kernel/resources/browsers/fs/fs.py

@@ -48,6 +48,7 @@
     async_to_custom_streamed_response_wrapper,
 )
 from ...._base_client import make_request_options
+from ....lib.multipart import indexed_multipart_body
 from ....types.browsers import (
     f_move_params,
     f_upload_params,
@@ -510,14 +511,19 @@ def upload(
             raise ValueError(f"Expected a non-empty value for `id_or_name` but received {id_or_name!r}")
         extra_headers = {"Accept": "*/*", **(extra_headers or {})}
         body = deepcopy_with_paths({"files": files}, [["files", "<array>", "file"]])
-        extracted_files = extract_files(cast(Mapping[str, object], body), paths=[["files", "<array>", "file"]])
+        # The remote filesystem pairs each file part with the sibling fields of the
+        # same array entry, so both halves of the form use indexed names
+        # (`files[0][file]`, `files[0][dest_path]`).
+        extracted_files = extract_files(
+            cast(Mapping[str, object], body), paths=[["files", "<array>", "file"]], array_format="indices"
+        )
         # It should be noted that the actual Content-Type header that will be
         # sent to the server will contain a `boundary` parameter, e.g.
         # multipart/form-data; boundary=---abc--
         extra_headers["Content-Type"] = "multipart/form-data"
         return self._post(
             path_template("/browsers/{id_or_name}/fs/upload", id_or_name=id_or_name),
-            body=maybe_transform(body, f_upload_params.FUploadParams),
+            body=indexed_multipart_body(maybe_transform(body, f_upload_params.FUploadParams)),
             files=extracted_files,
             options=make_request_options(
                 extra_headers=extra_headers, extra_query=extra_query, extra_body=extra_body, timeout=timeout
@@ -1073,14 +1079,19 @@ async def upload(
             raise ValueError(f"Expected a non-empty value for `id_or_name` but received {id_or_name!r}")
         extra_headers = {"Accept": "*/*", **(extra_headers or {})}
         body = deepcopy_with_paths({"files": files}, [["files", "<array>", "file"]])
-        extracted_files = extract_files(cast(Mapping[str, object], body), paths=[["files", "<array>", "file"]])
+        # The remote filesystem pairs each file part with the sibling fields of the
+        # same array entry, so both halves of the form use indexed names
+        # (`files[0][file]`, `files[0][dest_path]`).
+        extracted_files = extract_files(
+            cast(Mapping[str, object], body), paths=[["files", "<array>", "file"]], array_format="indices"
+        )
         # It should be noted that the actual Content-Type header that will be
         # sent to the server will contain a `boundary` parameter, e.g.
         # multipart/form-data; boundary=---abc--
         extra_headers["Content-Type"] = "multipart/form-data"
         return await self._post(
             path_template("/browsers/{id_or_name}/fs/upload", id_or_name=id_or_name),
-            body=await async_maybe_transform(body, f_upload_params.FUploadParams),
+            body=indexed_multipart_body(await async_maybe_transform(body, f_upload_params.FUploadParams)),
             files=extracted_files,
             options=make_request_options(
                 extra_headers=extra_headers, extra_query=extra_query, extra_body=extra_body, timeout=timeout