From 257fe32556b9879b0c0de0f072944f4f208f28cd Mon Sep 17 00:00:00 2001
From: Greig Menzies <138468674+gmenziesint@users.noreply.github.com>
Date: Wed, 24 Jun 2026 15:27:18 +0100
Subject: [PATCH] fix: caching middleware TypeError on cache miss due to
 mismatched call_next parameter (#4301)

---
 .../fastmcp/server/middleware/caching.py       | 18 +++++++++---------
 fastmcp_slim/fastmcp/server/server.py          |  4 ++--
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/fastmcp_slim/fastmcp/server/middleware/caching.py b/fastmcp_slim/fastmcp/server/middleware/caching.py
index 2739b9470..3a66cfca3 100644
--- a/fastmcp_slim/fastmcp/server/middleware/caching.py
+++ b/fastmcp_slim/fastmcp/server/middleware/caching.py
@@ -311,7 +311,7 @@ class ResponseCachingMiddleware(Middleware):
         if cached_value := await self._list_tools_cache.get(key=cache_key):
             return cached_value
 
-        tools: Sequence[Tool] = await call_next(context=context)
+        tools: Sequence[Tool] = await call_next(context)
 
         # Turn any subclass of Tool into a Tool
         cachable_tools: list[Tool] = [
@@ -352,7 +352,7 @@ class ResponseCachingMiddleware(Middleware):
         if cached_value := await self._list_resources_cache.get(key=cache_key):
             return cached_value
 
-        resources: Sequence[Resource] = await call_next(context=context)
+        resources: Sequence[Resource] = await call_next(context)
 
         # Turn any subclass of Resource into a Resource
         cachable_resources: list[Resource] = [
@@ -393,7 +393,7 @@ class ResponseCachingMiddleware(Middleware):
         if cached_value := await self._list_prompts_cache.get(key=cache_key):
             return cached_value
 
-        prompts: Sequence[Prompt] = await call_next(context=context)
+        prompts: Sequence[Prompt] = await call_next(context)
 
         # Turn any subclass of Prompt into a Prompt
         cachable_prompts: list[Prompt] = [
@@ -429,7 +429,7 @@ class ResponseCachingMiddleware(Middleware):
         if self._call_tool_settings.get(
             "enabled"
         ) is False or not self._matches_tool_cache_settings(tool_name=tool_name):
-            return await call_next(context=context)
+            return await call_next(context)
 
         cache_key: str = _make_call_tool_cache_key(
             msg=context.message, auth_key=_get_auth_partition_key()
@@ -438,7 +438,7 @@ class ResponseCachingMiddleware(Middleware):
         if cached_value := await self._call_tool_cache.get(key=cache_key):
             return cached_value.unwrap()
 
-        tool_result: ToolResult = await call_next(context=context)
+        tool_result: ToolResult = await call_next(context)
         cachable_tool_result: CachableToolResult = CachableToolResult.wrap(
             value=tool_result
         )
@@ -460,7 +460,7 @@ class ResponseCachingMiddleware(Middleware):
         """Read a resource from the cache, if caching is enabled, and the result is in the cache. Otherwise,
         otherwise call the next middleware and store the result in the cache if caching is enabled."""
         if self._read_resource_settings.get("enabled") is False:
-            return await call_next(context=context)
+            return await call_next(context)
 
         cache_key: str = _make_read_resource_cache_key(
             msg=context.message, auth_key=_get_auth_partition_key()
@@ -470,7 +470,7 @@ class ResponseCachingMiddleware(Middleware):
         if cached_value := await self._read_resource_cache.get(key=cache_key):
             return cached_value.unwrap()
 
-        value: ResourceResult = await call_next(context=context)
+        value: ResourceResult = await call_next(context)
         cached_value = CachableResourceResult.wrap(value)
 
         await self._read_resource_cache.put(
@@ -490,7 +490,7 @@ class ResponseCachingMiddleware(Middleware):
         """Get a prompt from the cache, if caching is enabled, and the result is in the cache. Otherwise,
         otherwise call the next middleware and store the result in the cache if caching is enabled."""
         if self._get_prompt_settings.get("enabled") is False:
-            return await call_next(context=context)
+            return await call_next(context)
 
         cache_key: str = _make_get_prompt_cache_key(
             msg=context.message, auth_key=_get_auth_partition_key()
@@ -499,7 +499,7 @@ class ResponseCachingMiddleware(Middleware):
         if cached_value := await self._get_prompt_cache.get(key=cache_key):
             return cached_value.unwrap()
 
-        value: PromptResult = await call_next(context=context)
+        value: PromptResult = await call_next(context)
         cached_value = CachablePromptResult.wrap(value)
 
         await self._get_prompt_cache.put(
diff --git a/fastmcp_slim/fastmcp/server/server.py b/fastmcp_slim/fastmcp/server/server.py
index 6a5fa00f3..461febb17 100644
--- a/fastmcp_slim/fastmcp/server/server.py
+++ b/fastmcp_slim/fastmcp/server/server.py
@@ -487,11 +487,11 @@ class FastMCP(
             next_chain: CallNext[Any, Any] = chain
 
             async def wrapped(
-                ctx: MiddlewareContext[Any],
+                context: MiddlewareContext[Any],
                 mw: Middleware = mw,
                 call_next: CallNext[Any, Any] = next_chain,
             ) -> Any:
-                return await mw(ctx, call_next)
+                return await mw(context, call_next)
 
             chain = cast(CallNext[Any, Any], wrapped)
         return await chain(context)