When a connected MCP server sends a ToolListChangedNotification (per the
MCP spec), Hermes now automatically re-fetches the tool list, deregisters
removed tools, and registers new ones — without requiring a restart.
This enables MCP servers with dynamic toolsets (e.g. GitHub MCP with
GITHUB_DYNAMIC_TOOLSETS=1) to add/remove tools at runtime.
Changes:
- registry.py: add ToolRegistry.deregister() for nuke-and-repave refresh
- mcp_tool.py: extract _register_server_tools() from
_discover_and_register_server() as a shared helper for both initial
discovery and dynamic refresh
- mcp_tool.py: add _make_message_handler() and _refresh_tools() on
MCPServerTask, wired into all 3 ClientSession sites (stdio, new HTTP,
deprecated HTTP)
- Graceful degradation: silently falls back to static discovery when the
MCP SDK lacks notification types or message_handler support
- 8 new tests covering registration, refresh, handler dispatch, and
deregister
Salvaged from PR #1794 by shivvor2.
Switch MCP HTTP transport from the deprecated streamablehttp_client()
(mcp < 1.24.0) to the new streamable_http_client() API that accepts a
pre-built httpx.AsyncClient.
Changes vs the original PR #3391:
- Separate try/except imports so mcp < 1.24.0 doesn't break (graceful
fallback to deprecated API instead of losing HTTP MCP entirely)
- Wrap httpx.AsyncClient in async-with for proper lifecycle management
(the new SDK API explicitly skips closing caller-provided clients)
- Match SDK's own create_mcp_http_client defaults: follow_redirects=True,
Timeout(connect_timeout, read=300.0)
- Keep deprecated code path as fallback for older SDK versions
Co-authored-by: HenkDz <HenkDz@users.noreply.github.com>
dict.get(key, default) returns None — not the default — when the key IS
present but explicitly set to null/~ in YAML. Calling .lower() on that
raises AttributeError.
Use (config.get(key) or fallback) so both missing keys and explicit nulls
coalesce to the intended default.
Files fixed:
- tools/tts_tool.py — _get_provider()
- tools/web_tools.py — _get_backend()
- tools/mcp_tool.py — MCPServerTask auth config
- trajectory_compressor.py — _detect_provider() and config loading
Co-authored-by: dieutx <dangtc94@gmail.com>
- Registry now warns when a tool name is overwritten by a different
toolset (silent dict overwrite was the previous behavior)
- MCP tool registration checks for collisions with non-MCP (built-in)
tools before registering. If an MCP tool's prefixed name matches an
existing built-in, the MCP tool is skipped and a warning is logged.
MCP-to-MCP collisions are allowed (last server wins).
- Both regular MCP tools and utility tools (resources/prompts) are
guarded.
- Adds 5 tests covering: registry overwrite warning, same-toolset
re-registration silence, built-in collision skip, normal registration,
and MCP-to-MCP collision pass-through.
Reported by k_sze (KONG) — MiniMax MCP server's web_search tool could
theoretically shadow Hermes's built-in web_search if prefixing failed.
Add hermes mcp add/remove/list/test/configure CLI for managing MCP
server connections interactively. Discovery-first 'add' flow connects,
discovers tools, and lets users select which to enable via curses checklist.
Add OAuth 2.1 PKCE authentication for MCP HTTP servers (RFC 7636).
Supports browser-based and manual (headless) authorization, token
caching with 0600 permissions, automatic refresh. Zero external deps.
Add ${ENV_VAR} interpolation in MCP server config values, resolved
from os.environ + ~/.hermes/.env at load time.
Core OAuth module from PR #2021 by @imnotdev25. CLI and mcp_tool
wiring rewritten against current main. Closes#497, #690.
Each configured MCP server now registers as its own toolset in TOOLSETS
(e.g. TOOLSETS['github'] = {tools: ['mcp_github_list_files', ...]}),
making raw server names resolvable in platform_toolsets overrides.
Previously MCP tools were only injected into hermes-* umbrella toolsets,
so gateway sessions using raw toolset names like ['terminal', 'github']
in platform_toolsets couldn't resolve MCP tools.
Skips server names that collide with built-in toolsets. Also handles
idempotent reloads (syncs toolsets even when no new servers connect).
Inspired by PR #1876 by @kshitijk4poor.
Adds 2 tests (standalone toolset creation + built-in collision guard).
Add the ability to selectively enable/disable individual MCP server
tools through the interactive 'hermes tools' TUI.
Changes:
- tools/mcp_tool.py: Add probe_mcp_server_tools() — lightweight function
that temporarily connects to configured MCP servers, discovers their
tools (names + descriptions), and disconnects. No registry side effects.
- hermes_cli/tools_config.py: Add 'Configure MCP tools' option to the
interactive menu. When selected:
1. Probes all enabled MCP servers for their available tools
2. Shows a per-server curses checklist with tool descriptions
3. Pre-selects tools based on existing include/exclude config
4. Writes changes back as tools.exclude entries in config.yaml
5. Reports which servers failed to connect
The existing CLI commands (hermes tools enable/disable server:tool)
continue to work unchanged. This adds the interactive TUI counterpart
so users can browse and toggle MCP tools visually.
Tests: 22 new tests covering probe function edge cases and interactive
flow (pre-selection, exclude/include modes, description truncation,
multi-server handling, error paths).
Extend the salvaged MCP filtering work so utility tools are also governed by policy and server capabilities. Store the registered tool subset per server so rediscovery and status reporting stay accurate after filtering.
Add optional config keys under each mcp_servers entry:
- tools.include: whitelist, only listed tools are registered
- tools.exclude: blacklist, all tools except listed are registered
- enabled: false: skip server entirely, no connection attempt
Backward-compatible: no config keys = all tools registered as before.
Tests: TestMCPSelectiveToolLoading (4 tests), 134 passed total.
Salvaged from PR #977 onto current main.
Preserves the MCP stdio command resolution and improved error diagnostics,
with deterministic regression tests for the npx/node PATH cases.
Co-authored-by: kshitij <82637225+kshitijk4poor@users.noreply.github.com>
- gateway/run.py: Take main's _resolve_gateway_model() helper
- hermes_cli/setup.py: Re-apply nous-api removal after merge brought
it back. Fix provider_idx offset (Custom is now index 3, not 4).
- tests/hermes_cli/test_setup.py: Fix custom setup test index (3→4)
Add centralized call_llm() and async_call_llm() functions that own the
full LLM request lifecycle:
1. Resolve provider + model from task config or explicit args
2. Get or create a cached client for that provider
3. Format request args (max_tokens handling, provider extra_body)
4. Make the API call with max_tokens/max_completion_tokens retry
5. Return the response
Config: expanded auxiliary section with provider:model slots for all
tasks (compression, vision, web_extract, session_search, skills_hub,
mcp, flush_memories). Config version bumped to 7.
Migrated all auxiliary consumers:
- context_compressor.py: uses call_llm(task='compression')
- vision_tools.py: uses async_call_llm(task='vision')
- web_tools.py: uses async_call_llm(task='web_extract')
- session_search_tool.py: uses async_call_llm(task='session_search')
- browser_tool.py: uses call_llm(task='vision'/'web_extract')
- mcp_tool.py: uses call_llm(task='mcp')
- skills_guard.py: uses call_llm(provider='openrouter')
- run_agent.py flush_memories: uses call_llm(task='flush_memories')
Tests updated for context_compressor and MCP tool. Some test mocks
still need updating (15 remaining failures from mock pattern changes,
2 pre-existing).
_discover_one() caught all exceptions and returned [], making
asyncio.gather(return_exceptions=True) redundant. The
isinstance(result, Exception) branch in _discover_all() was dead
code, so failed_count was always 0. This caused:
- No summary printed when all servers fail (silent failure)
- ok_servers always equaling total_servers (misleading count)
- Unused variables transport_desc and transport_type
Fix: let exceptions propagate to gather() so failed_count increments
correctly. Move per-server failure logging to _discover_all(). Remove
dead variables.
SamplingHandler.__call__ accessed response.choices[0] without checking
if the list was non-empty. LLM APIs can return empty choices on content
filtering, provider errors, or rate limits, causing an unhandled
IndexError that propagates to the MCP SDK and may crash the connection.
Add a defensive guard that returns a proper ErrorData when choices is
empty, None, or missing. Includes three test cases covering all
variants.
Add MCP sampling/createMessage capability via SamplingHandler class.
Text-only sampling + tool use in sampling with governance (rate limits,
model whitelist, token caps, tool loop limits). Per-server audit metrics.
Based on concept from PR #366 by eren-karakus0. Restructured as class-based
design with bug fixes and tests using real MCP SDK types.
50 new tests, 2600 total passing.
Banner integration:
- MCP Servers section in CLI startup banner between Tools and Skills
- Shows each server with transport type, tool count, connection status
- Failed servers shown in red; section hidden when no MCP configured
- Summary line includes MCP server count
- Removed raw print() calls from discovery (banner handles display)
/reload-mcp command:
- New slash command in both CLI and gateway
- Disconnects all MCP servers, re-reads config.yaml, reconnects
- Reports what changed (added/removed/reconnected servers)
- Allows adding/removing MCP servers without restarting
Resources & Prompts support:
- 4 utility tools registered per server: list_resources, read_resource,
list_prompts, get_prompt
- Exposes MCP Resources (data sources) and Prompts (templates) as tools
- Proper parameter schemas (uri for read_resource, name for get_prompt)
- Handles text and binary resource content
- 23 new tests covering schemas, handlers, and registration
Test coverage: 74 MCP tests total, 1186 tests pass overall.
- Discovery is now parallel (asyncio.gather) instead of sequential,
fixing the 60s shared timeout issue with multiple servers
- Startup messages use print() so users see connection status even
with default log levels (the 'tools' logger is set to ERROR)
- Summary line shows total tools and failed servers count
- Validate conflicting config: warn if both 'url' and 'command' are
present (HTTP takes precedence)
- Update TODO.md: mark MCP as implemented, list remaining work
- Add test for conflicting config detection (51 tests total)
All 1163 tests pass.
- Add threading.Lock protecting all shared state (_servers, _mcp_loop, _mcp_thread)
- Fix deadlock in shutdown_mcp_servers: _stop_mcp_loop was called inside
a _lock block but also acquires _lock (non-reentrant)
- Fix race condition in _ensure_mcp_loop with concurrent callers
- Change idempotency to per-server (retry failed servers, skip connected)
- Dynamic toolset injection via startswith("hermes-") instead of hardcoded list
- Parallel shutdown via asyncio.gather instead of sequential loop
- Add tests for partial failure retry, parallel shutdown, dynamic injection
When discover_mcp_tools() is called multiple times (e.g. direct call
then model_tools import), return existing tool names instead of opening
new connections that would orphan the previous ones.
Refactor MCP connections from AsyncExitStack to task-per-server
architecture. Each server now runs as a long-lived asyncio Task
with `async with stdio_client(...)`, ensuring anyio cancel-scope
cleanup happens in the same Task that opened the connection.
Connect to external MCP servers via stdio transport, discover their tools
at startup, and register them into the hermes-agent tool registry.
- New tools/mcp_tool.py: config loading, server connection via background
event loop, tool handler factories, discovery, and graceful shutdown
- model_tools.py: trigger MCP discovery after built-in tool imports
- cli.py: call shutdown_mcp_servers in _run_cleanup
- pyproject.toml: add mcp>=1.2.0 as optional dependency
- 27 unit tests covering config, schema conversion, handlers, registration,
SDK interaction, toolset injection, graceful fallback, and shutdown
Config format (in ~/.hermes/config.yaml):
mcp_servers:
filesystem:
command: "npx"
args: ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
