subclass Transform js to get our shit looking nice holy moly

docs/mcp_protocol_proxy_inventory.md

@@ -98,12 +98,11 @@ Tool simulate-research-query requires task augmentation (taskSupport: 'required'
 - Proxy tool projection: healthy for ordinary tools.
 - Proxy resource list/read projection: healthy for listed resources and
   templates.
-- Tool-result resource links: incomplete; embedded resource URIs need explicit
-  rewrite or a documented limitation.
-- `wf_mcp.proxy_results` now contains pure typed helpers for rewriting
-  `mcp.types.ResourceLink` content inside `mcp.types.CallToolResult`. These
-  helpers are not wired into the FastMCP proxy runtime yet because FastMCP does
-  not currently expose a result-transform hook.
+- Tool-result resource links: ordinary embedded resource URIs are now rewritten
+  by a local proxy transform so downstream clients receive namespaced URIs.
+- `wf_mcp.proxy_results` contains pure typed helpers for rewriting
+  `mcp.types.ResourceLink` content and a small FastMCP workaround transform that
+  wraps proxied tools until upstream FastMCP handles this projection itself.
 - Session resources: unresolved; needs a focused test because session affinity
   may matter.
 - Tasks: unsupported; task-required tools should remain clearly diagnosed until
@@ -115,10 +114,8 @@ Tool simulate-research-query requires task augmentation (taskSupport: 'required'
 
 - Add automated tests for listed resource/template namespacing through unified
   mode.
-- Add a fixture or Everything integration test showing tool-returned
-  `resource_link` URIs are not rewritten today.
-- Decide whether to rewrite embedded resource links in tool results or expose a
-  helper that resolves upstream resource links into proxied resource URIs.
+- Keep the fixture regression proving ordinary tool-returned `resource_link`
+  URIs are rewritten into downstream-facing namespaced URIs.
 - Investigate session resource lifecycle separately from URI rewriting.
 - Inventory current FastMCP/MCP SDK APIs for tasks, logging notifications, and
   resource update notifications before implementing protocol forwarding.

docs/superpowers/specs/2026-05-15-proxy-mount-lifecycle-design.md

@@ -178,10 +178,28 @@ actually implemented.
 - wiring `wf_mcp.proxy_results` helpers into real tool-result handling
 - replacing FastMCP behavior that should be fixed upstream instead
 
-## Open Question
+## Investigation Result
 
-Whether reused mounts should keep FastMCP `ProxyProvider` component caches across
-reload is not yet a promise. Reuse likely does preserve those caches. If that
-causes stale catalog behavior, the registry should either invalidate the provider
-cache explicitly when supported or treat reload as a reason to rebuild mounts
-for affected connections.
+FastMCP 3.3.0 makes unchanged-mount reuse reasonable, with caveats:
+
+- `create_proxy_mount()` passes a disconnected `Client` into `create_proxy(...)`.
+  FastMCP turns that into `client.new()` per request, so reusing a
+  `FastMCPProxy` does **not** keep one permanently connected upstream session
+  alive.
+- `ProxyProvider` intentionally caches tools, resources, templates, and prompts
+  for lookup efficiency. The default TTL is 300 seconds.
+- Every explicit `list_*` call refreshes the corresponding proxy cache. Direct
+  lookup paths may use a still-fresh cached list until TTL expiry.
+- `FastMCP.mount()` returns no provider handle, and no public general-purpose
+  unmount API was found. Parent-side provider-list rebuild is still the only
+  safe visible-surface removal we currently own.
+
+Therefore the current registry behavior is acceptable:
+
+- reuse unchanged enabled mounts
+- rebuild changed mounts
+- stop remounting disabled or removed mounts
+- do not claim safe close/unmount of retired mounts yet
+
+If dynamic upstream catalogs become a practical problem, prefer a documented
+refresh/invalidation policy over throwing away unchanged mounts on every reload.

docs/wf_mcp_architecture.md

@@ -64,6 +64,20 @@ Unified mode currently reuses `ProxyRuntime` as its proxy mounting engine. The
 the place where configured upstream MCP connections become mounted FastMCP
 providers. `TransparentProxyRuntime` remains a compatibility alias.
 
+`ProxyRuntime` now owns a small `ProxyMountRegistry`. Reload still clears the
+visible mounted provider list and rebuilds it from current config, but unchanged
+enabled connections reuse their cached proxy mount instead of recreating a new
+client/proxy pair every time. Disabled or removed connections are no longer
+mounted after reload, but their cached mounts are only *retired* internally for
+now; they are not safely closed or unmounted because FastMCP does not yet expose
+the lifecycle hook we need.
+
+The reused FastMCP proxies are not holding one forever-open upstream connection.
+`create_proxy_mount()` gives `create_proxy(...)` a disconnected client, and
+FastMCP creates fresh request clients from it. What persists across reload is the
+proxy/provider object and its component-list caches. FastMCP refreshes those
+caches on explicit `list_*` calls and otherwise expires them after its TTL.
+
 After a successful reload, the runtime publishes local `tools_changed`,
 `resources_changed`, `prompts_changed`, and `catalog_changed` events when an
 event bus is supplied. The admin MCP tool projects the same event kinds into
@@ -75,11 +89,10 @@ typed result to a plain payload at the boundary.
 Proxy tool listing similarly uses `ProxyToolPayload` / `ProxyToolsPage`
 internally and serializes to admin MCP payloads at the boundary.
 
-Do not memoize mounted proxies or clients without an explicit lifecycle design.
-The tempting implementation is a dictionary keyed by connection id around
-`create_proxy(client, ...)`, but cached clients need clear close/reconnect/error
-semantics. Prefer FastMCP's official unmount/provider lifecycle when it becomes
-available.
+Do not add more lifecycle behavior outside `ProxyMountRegistry`. Cached clients
+still need clear close/reconnect/error semantics, and the registry is the single
+place where that future behavior should land. Prefer FastMCP's official
+unmount/provider lifecycle when it becomes available.
 
 Do not add notification proxying or long-lived subscription handling across
 reloads without first introducing an explicit mount lifecycle boundary.

src/wf_mcp/proxy_results/__init__.py

@@ -3,8 +3,11 @@ from .resource_links import (
     rewrite_call_tool_result_resource_links,
     rewrite_resource_link_content,
 )
+from .resource_link_transform import ResourceLinkNamespace, ResourceLinkRewritingTool
 
 __all__ = [
+    "ResourceLinkNamespace",
+    "ResourceLinkRewritingTool",
     "ResourceUriRewriter",
     "rewrite_call_tool_result_resource_links",
     "rewrite_resource_link_content",

src/wf_mcp/proxy_results/resource_link_transform.py

@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+import re
+from collections.abc import Callable, Sequence
+from typing import Any
+
+from fastmcp.server.transforms import GetToolNext, Transform
+from fastmcp.tools.base import Tool, ToolResult
+from fastmcp.utilities.versions import VersionSpec
+from pydantic import ConfigDict
+from pydantic.json_schema import SkipJsonSchema
+
+from .resource_links import rewrite_resource_link_content
+
+_URI_PATTERN = re.compile(r"^([^:]+://)(.*?)$")
+
+
+class ResourceLinkRewritingTool(Tool):
+    """Delegate tool execution while rewriting returned resource-link URIs."""
+
+    model_config = ConfigDict(extra="allow", arbitrary_types_allowed=True)
+
+    parent_tool: SkipJsonSchema[Tool]
+    rewrite_uri: SkipJsonSchema[Callable[[str], str]]
+
+    async def run(self, arguments: dict[str, Any]) -> ToolResult:
+        """Run the parent tool and project any resource links downstream."""
+        result = await self.parent_tool.run(arguments)
+        return ToolResult(
+            content=[
+                rewrite_resource_link_content(content, self.rewrite_uri)
+                for content in result.content
+            ],
+            structured_content=result.structured_content,
+            meta=result.meta,
+        )
+
+    @classmethod
+    def wrap(
+        cls,
+        tool: Tool,
+        rewrite_uri: Callable[[str], str],
+    ) -> ResourceLinkRewritingTool:
+        """Copy one tool's public schema while replacing only execution."""
+        return cls.model_validate(
+            {
+                **tool.model_dump(),
+                "parent_tool": tool,
+                "rewrite_uri": rewrite_uri,
+            }
+        )
+
+
+class ResourceLinkNamespace(Transform):
+    """Rewrite resource links returned by tools into one namespace."""
+
+    def __init__(self, prefix: str) -> None:
+        self._prefix = prefix
+
+    def __repr__(self) -> str:
+        return f"ResourceLinkNamespace({self._prefix!r})"
+
+    async def list_tools(self, tools: Sequence[Tool]) -> Sequence[Tool]:
+        """Wrap listed tools so downstream callers receive projected links."""
+        return [self._wrap_tool(tool) for tool in tools]
+
+    async def get_tool(
+        self,
+        name: str,
+        call_next: GetToolNext,
+        *,
+        version: VersionSpec | None = None,
+    ) -> Tool | None:
+        """Wrap fetched tools so direct calls also receive projected links."""
+        tool = await call_next(name, version=version)
+        return None if tool is None else self._wrap_tool(tool)
+
+    def _wrap_tool(self, tool: Tool) -> ResourceLinkRewritingTool:
+        return ResourceLinkRewritingTool.wrap(tool, self._transform_uri)
+
+    def _transform_uri(self, uri: str) -> str:
+        """Match FastMCP Namespace URI projection for tool-returned links."""
+        match = _URI_PATTERN.match(uri)
+        if match is None:
+            return uri
+        protocol, path = match.groups()
+        return f"{protocol}{self._prefix}/{path}"

src/wf_mcp/transparent_proxy/mounts.py

@@ -13,6 +13,7 @@ from fastmcp.server import create_proxy
 from fastmcp.server.transforms import Namespace
 
 from ..models import BrokerConfig, ConnectionConfig
+from ..proxy_results import ResourceLinkNamespace
 from ..proxy_config import broker_config_to_fastmcp_config
 
 ProxyT = TypeVar("ProxyT")
@@ -98,6 +99,7 @@ def create_proxy_mount(
     client = Client(transport=transport, name=f"wf-mcp:{connection.id}")
     proxy: FastMCP[Any] = create_proxy(client, name=f"Proxy-{connection.id}")
     proxy.add_transform(Namespace(connection.id))
+    proxy.add_transform(ResourceLinkNamespace(connection.id))
     return ProxyMount(
         connection_id=connection.id,
         fingerprint=connection_fingerprint(connection),

tests/fixtures/mcp_echo_server.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from typing import Annotated, TypedDict
 
+import mcp.types as mcp_types
 from mcp.server.fastmcp import FastMCP
 from pydantic import Field
 
@@ -20,6 +21,21 @@ async def echo_tool(
     return {"echoed": text}
 
 
+@server.tool(title="Resource link tool")
+async def resource_link_tool() -> list[mcp_types.ResourceLink]:
+    """Return a link to a fixture resource so proxy URI rewriting is testable."""
+    return [
+        mcp_types.ResourceLink.model_validate(
+            {
+                "type": "resource_link",
+                "name": "resource.welcome",
+                "uri": "fixture://docs/welcome",
+                "mimeType": "text/plain",
+            }
+        )
+    ]
+
+
 @server.resource(
     "fixture://docs/welcome",
     name="resource.welcome",

tests/wf_mcp/test_transparent_proxy.py

@@ -83,12 +83,16 @@ def test_transparent_proxy_lists_and_calls_upstream_tools() -> None:
             proxy_tools_payload = _structured(proxy_tools_result)
             proxy_tools = proxy_tools_payload["tools"]
             assert proxy_tools_payload["nextCursor"] is None
-            assert proxy_tools_payload["total"] == 1
-            assert len(proxy_tools) == 1
+            assert proxy_tools_payload["total"] == 2
+            assert len(proxy_tools) == 2
             assert proxy_tools[0]["proxy_name"] == "fixture.personal_echo_tool"
             assert proxy_tools[0]["connection_id"] == "fixture.personal"
             assert proxy_tools[0]["local_name"] == "echo_tool"
             assert proxy_tools[0]["enabled"] is True
+            assert (
+                proxy_tools[1]["proxy_name"]
+                == "fixture.personal_resource_link_tool"
+            )
 
             proxy_tool_result = await client.call_tool(
                 "wf.admin.get_proxy_tool",
@@ -103,6 +107,38 @@ def test_transparent_proxy_lists_and_calls_upstream_tools() -> None:
     asyncio.run(run_proxy())
 
 
+def test_transparent_proxy_rewrites_resource_links_returned_by_tools() -> None:
+    config = BrokerConfig(
+        store_root=local_temp_root() / "transparent_proxy_resource_link_store",
+        connections=[
+            ConnectionConfig(
+                id="fixture.personal",
+                server="fixture",
+                account="personal",
+                metadata={
+                    "transport": "stdio",
+                    "command": sys.executable,
+                    "args": [fixture_server_path()],
+                },
+            )
+        ],
+    )
+
+    async def run_proxy() -> None:
+        client = create_transparent_proxy_client(config)
+        async with client:
+            result = await client.call_tool("fixture.personal_resource_link_tool")
+            link = result.content[0]
+            assert isinstance(link, mcp_types.ResourceLink)
+            assert str(link.uri) == "fixture://fixture.personal/docs/welcome"
+
+            contents = await client.read_resource(str(link.uri))
+            assert isinstance(contents[0], mcp_types.TextResourceContents)
+            assert contents[0].text == "Welcome from the fixture MCP server."
+
+    asyncio.run(run_proxy())
+
+
 def test_transparent_proxy_rejects_invalid_connection_config() -> None:
     config = BrokerConfig(
         store_root=local_temp_root() / "transparent_proxy_invalid_store",
@@ -267,7 +303,7 @@ def test_transparent_proxy_proxy_tool_listing_supports_filters_and_cursor() -> N
             first_page = _structured(first_page_result)
             assert len(first_page["tools"]) == 1
             assert first_page["nextCursor"] is not None
-            assert first_page["total"] == 2
+            assert first_page["total"] == 4
 
             second_page_result = await client.call_tool(
                 "wf.admin.list_proxy_tools",
@@ -561,6 +597,34 @@ def test_transparent_proxy_runtime_reload_publishes_local_change_events() -> Non
     assert catalog_changed[0].payload["reason"] == "transparent_reload"
 
 
+def test_transparent_proxy_runtime_reload_reuses_unchanged_mounts() -> None:
+    config = BrokerConfig(
+        store_root=local_temp_root() / "transparent_proxy_reuse_store",
+        connections=[
+            ConnectionConfig(
+                id="fixture.personal",
+                server="fixture",
+                account="personal",
+                metadata={
+                    "transport": "stdio",
+                    "command": sys.executable,
+                    "args": [fixture_server_path()],
+                },
+            )
+        ],
+    )
+    runtime = ProxyRuntime(config)
+    first_mount = runtime.mounts.active_mounts_for(config)[0]
+
+    result = runtime.reload()
+    second_mount = runtime.mounts.active_mounts_for(config)[0]
+
+    assert result["mounted_connections"] == ["fixture.personal"]
+    assert result["connection_count"] == 1
+    assert result["enabled_connection_count"] == 1
+    assert first_mount is second_mount
+
+
 def test_proxy_reload_result_serializes_and_drives_reload_events() -> None:
     result = ProxyReloadResult(
         mounted_connections=["fixture.personal"],