@@ -47,4 +47,10 @@ __pycache__/
 cecli/website/_site/*
 cecli/website/.sass-cache/*
 cecli/website/.docmd-*/*
-cecli/website/node_modules/*
+cecli/website/node_modules/*
+
+# Beads / Dolt files (added by bd init)
+.dolt/
+*.db
+.beads-credential-key
+.beads/proxieddb/
@@ -3187,7 +3187,8 @@ def _find_mcp_server_for_tool(self, tool_call):
                 tool_name_from_schema = nested.getter(tool, "function.name")
                 if (
                     tool_name_from_schema
-                    and tool_name_from_schema.lower() == unprefixed_tool_name.lower()
+                    and responses.sanitize_tool_name(tool_name_from_schema).lower()
+                    == responses.sanitize_tool_name(unprefixed_tool_name).lower()
                 ):
                     # Find the McpServer instance that will be used for communication
                     for server in self.mcp_manager:
@@ -3409,6 +3410,10 @@ async def call_mcp_tool_from_session(self, session, tool_call):
         # with a "missing required parameter" error.
         arguments = responses.coerce_tool_structure(arguments)
 
+        # Providers require a provider-safe tool name, so the name coming back
+        # from the model may not be the name the MCP server advertises.
+        name = responses.original_tool_name(name, self.mcp_tools)
+
         return await session.call_tool(name=name, arguments=arguments)
 
     async def process_tool_calls(self, tool_call_response):
 
@@ -247,6 +247,32 @@ def extract_tools_from_pseudo_json(content: str) -> Optional[List[ChatCompletion
         return None
 
 
+def sanitize_tool_name(name: str) -> str:
+    """Make a name acceptable in OpenAI-style ``tools[].function.name``.
+
+    Providers enforce ``^[A-Za-z0-9_-]{1,64}$`` on the function name, which
+    rejects names an MCP server may legitimately advertise (``browser.fetch``).
+    Idempotent, so it is also safe on an incoming tool call before the name is
+    compared against, or mapped back to, the server's own name.
+    """
+    return re.sub(r"[^A-Za-z0-9_-]", "_", name)[:64]
+
+
+def original_tool_name(name: str, server_tools) -> str:
+    """Map a sanitized tool name back to the name the MCP server advertises.
+
+    ``server_tools`` is an iterable of ``(server_name, tools)`` pairs. Returns
+    ``name`` unchanged when nothing matches, so an unsanitized name still
+    reaches the server as-is.
+    """
+    for _server_name, tools in server_tools or []:
+        for tool in tools:
+            candidate = nested.getter(tool, "function.name", "")
+            if candidate and sanitize_tool_name(candidate) == name:
+                return candidate
+    return name
+
+
 def prefix_tool_name(server_name: str, tool_name: str) -> str:
     """
     Prefix a tool name with the server name.
@@ -256,9 +282,9 @@ def prefix_tool_name(server_name: str, tool_name: str) -> str:
         tool_name: Original tool name
 
     Returns:
-        Prefixed tool name in format "{server_name}--{tool_name}"
+        Prefixed, provider-safe tool name in format "{server_name}--{tool_name}"
     """
-    return f"{server_name}--{tool_name}"
+    return sanitize_tool_name(f"{server_name}--{tool_name}")
 
 
 def unprefix_tool_name(prefixed_name: str) -> tuple[str, str]:
 
@@ -0,0 +1,119 @@
+"""Tests for provider-safe MCP tool names.
+
+Providers enforce ``^[A-Za-z0-9_-]{1,64}$`` on ``tools[].function.name``, so a
+dotted MCP name such as ``browser.fetch`` is sanitized on the way to the model
+and mapped back to the server's own name when the call comes back.
+"""
+
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from cecli.coders import Coder
+from cecli.helpers import responses
+
+
+def _tool(name):
+    """Build a minimal OpenAI-style function tool dict."""
+    return {
+        "type": "function",
+        "function": {"name": name, "description": "", "parameters": {}},
+    }
+
+
+def _call(name):
+    return {
+        "id": "call-1",
+        "type": "function",
+        "function": {"name": name, "arguments": "{}"},
+    }
+
+
+class TestSanitizeToolName:
+    def test_dots_become_underscores(self):
+        assert responses.sanitize_tool_name("browser.fetch") == "browser_fetch"
+
+    def test_is_idempotent(self):
+        once = responses.sanitize_tool_name("browser.persisted_session.list")
+
+        assert responses.sanitize_tool_name(once) == once
+
+    def test_honors_provider_length_limit(self):
+        assert len(responses.sanitize_tool_name("a" * 200)) == 64
+
+
+class TestGetToolListSanitizesNames:
+    def _coder(self, tools):
+        return SimpleNamespace(
+            mcp_tools=[("browser", tools)],
+            registered_servers={"included": set(), "excluded": set()},
+            registered_tools={"included": set(), "excluded": set()},
+        )
+
+    def test_dotted_names_are_sanitized_for_the_model(self):
+        coder = self._coder([_tool("browser.fetch"), _tool("browser.persisted_session.list")])
+
+        names = [t["function"]["name"] for t in Coder.get_tool_list(coder)]
+
+        assert names == [
+            "browser--browser_fetch",
+            "browser--browser_persisted_session_list",
+        ]
+
+    def test_underscore_name_is_unchanged(self):
+        coder = self._coder([_tool("brave_web_search")])
+
+        names = [t["function"]["name"] for t in Coder.get_tool_list(coder)]
+
+        assert names == ["browser--brave_web_search"]
+
+
+class TestFindMcpServerForSanitizedCall:
+    def test_sanitized_call_resolves_to_its_server(self):
+        server = SimpleNamespace(name="browser")
+        coder = SimpleNamespace(
+            mcp_tools=[("browser", [_tool("browser.fetch")])],
+            mcp_manager=[server],
+        )
+        tool_call = SimpleNamespace(
+            id="call-1",
+            type="function",
+            function=SimpleNamespace(name="browser--browser_fetch"),
+        )
+
+        assert Coder._find_mcp_server_for_tool(coder, tool_call) is server
+
+
+class TestCallToolMapsBackToAdvertisedName:
+    """The name the model calls must reach the server unsanitized."""
+
+    @pytest.mark.asyncio
+    async def test_sanitized_name_is_mapped_back(self):
+        coder = SimpleNamespace(mcp_tools=[("browser", [_tool("browser.fetch")])])
+        session = MagicMock()
+        session.call_tool = AsyncMock(return_value="ok")
+
+        await Coder.call_mcp_tool_from_session(coder, session, _call("browser_fetch"))
+
+        assert session.call_tool.await_args.kwargs["name"] == "browser.fetch"
+
+    @pytest.mark.asyncio
+    async def test_unsanitized_name_passes_through(self):
+        coder = SimpleNamespace(mcp_tools=[("browser", [_tool("browser.fetch")])])
+        session = MagicMock()
+        session.call_tool = AsyncMock(return_value="ok")
+
+        await Coder.call_mcp_tool_from_session(coder, session, _call("browser.fetch"))
+
+        assert session.call_tool.await_args.kwargs["name"] == "browser.fetch"
+
+    @pytest.mark.asyncio
+    async def test_unknown_name_is_not_rewritten(self):
+        coder = SimpleNamespace(mcp_tools=[("browser", [_tool("browser.fetch")])])
+        session = MagicMock()
+        session.call_tool = AsyncMock(return_value="ok")
+
+        await Coder.call_mcp_tool_from_session(coder, session, _call("read_file"))
+
+        assert session.call_tool.await_args.kwargs["name"] == "read_file"