> ## Documentation Index > Fetch the complete documentation index at: https://docs.mezmo.com/llms.txt > Use this file to discover all available pages before exploring further. # Breaking Changes: 5 October 2026 > Find out which tool-name patterns stop AURA v0.2.18 from starting, what `:`, `[abc]`, and `{a,b}` now match, and which MCP server provides a shared tool name. # 5 October 2026 # !!BREAKING CHANGES!! ## Summary AURA v0.2.18 changes how tool-name patterns and shared MCP tool names work: * **Invalid patterns stop startup.** AURA now checks every tool-name pattern when it loads the config. This covers `[agent].mcp_filter`, `[orchestration.worker.].mcp_filter`, `[hitl].require_approval`, `[agent].client_tool_filter`, and the keys of `[mcp.servers..scratchpad]`. * **Some patterns match differently.** `:`, `[abc]`, and `{a,b}` now have pattern meanings in `mcp_filter`, `client_tool_filter`, and scratchpad keys instead of matching those characters literally. In `require_approval`, `:` now scopes a pattern to one MCP server. * **Shared tool names resolve to one server.** When multiple MCP servers advertise the same tool name, the server whose `[mcp.servers.]` key sorts first always provides it. * **The web server connects to MCP servers before it starts accepting requests.** Slow or unreachable servers lengthen startup. **CONFIGS WITH AN INVALID TOOL-NAME PATTERN FAIL TO LOAD AND THE APP FAILS TO START.** See [Startup Errors](#startup-errors). For the full pattern syntax, see [Tool-Name Patterns](/aura/configuration-reference#tool-name-patterns) in the configuration reference. ## Why Before this release, the pattern fields didn't share one syntax: * `mcp_filter`, `client_tool_filter`, and scratchpad keys understood only `*` and `?`, and treated every other character literally. * `require_approval` accepted `[abc]` and `{a,b}`, but `mcp_filter` didn't. * A pattern that could never match a tool name, such as one containing a space, loaded without an error. The mistake showed up only as a tool that was never selected or never gated. * Patterns had no way to tell apart tools with the same name from different MCP servers. Which server's tool the agent could call could change from run to run. ## Patterns That Now Fail at Startup A pattern that loaded before can now stop AURA from starting: | Pattern | Why it fails | Fix | | - | - | - | | `"list pods"`, `"get+user"` | Only letters, digits, `_`, `-`, `/`, and `.` are allowed outside wildcards, classes, and alternatives. | Remove the character, or match it with `?` or `*`. | | `""` | A pattern can't be empty. | Remove the entry. An empty list such as `mcp_filter = []` is still valid. | | `"git\\*"` | There is no escape character. | Remove the `\`. | | `"github::*"`, `"a:b:c"`, `"github:"` | A pattern can contain only one `:`, with a non-empty segment on each side. | Use `:`, such as `"github:*"`. | | `"get_[*]"`, `"get_{a,{b,c}}"`, `"get_[abc"` | A class holds only literal characters, alternatives can't nest, and every `[` and `{` needs its closing bracket. | Rewrite the class or alternative, for example `"get_{a,b,c}"`. | | A run of more than 64 letters, digits, `_`, `-`, `/`, and `.` | A literal run can be at most 64 characters, even when a wildcard follows it. | Shorten the run, or replace part of it with `?` or `*`. | ## Patterns That Now Match Differently These patterns load without an error but select different tools than before: | Pattern | Before | Now | | - | - | - | | `github:create_issue` | Matched only a tool literally named `github:create_issue`. | Matches `create_issue` from `[mcp.servers.github]`. In `client_tool_filter`, it never matches. | | `pod[sx]` | In `mcp_filter`, `client_tool_filter`, and scratchpad keys, matched only the literal name `pod[sx]`. | Matches `pods` or `podx`. | | `get_{pods,events}` | In `mcp_filter`, `client_tool_filter`, and scratchpad keys, matched only the literal name `get_{pods,events}`. | Matches `get_pods` or `get_events`. | `[hitl].require_approval` already treated `[abc]` and `{a,b}` as a class and an alternation, so only the meaning of `:` changed there. ## Shared Tool Names Resolve to One Server AURA presents MCP tools to the model by their bare names, so only one server's tool can hold a given name. When more than one server advertises the same tool name, the agent now always gets the tool from the server whose `[mcp.servers.]` key sorts first. Only servers whose tool passes the agent's or worker's `mcp_filter` count. For example, `[mcp.servers.alpha]` wins over `[mcp.servers.beta]`, whatever transport each server uses. Text-fallback tool calls (`fallback_tool_parsing`) now resolve to the same server. Before, they could call the first server that advertised the name, even a server the agent's `mcp_filter` excluded. The web server logs a warning for each shared name at startup, and governance catalog sync logs the same warning: ```text theme={null} agent '': MCP tool '' is advertised by servers (); only '' will be reachable. Scope each agent with [agent].mcp_filter, or rename the tool on all but one server. ``` The warning names the server that sorts first and doesn't account for `mcp_filter`, so an agent's filter can select a different server than the warning names. ## Web Server Startup Takes Longer To find shared tool names, the web server now connects to each agent's MCP servers once before it starts accepting requests. The servers are checked one at a time, and each connection can take up to [`[mcp].connect_timeout_secs`](/aura/configuration-reference#mcp). The check starts each `stdio` server's command. The check sends only static `headers`. A server that needs headers from `headers_from_request` logs a connection warning at startup, and the web server still starts. ## Migration To upgrade a config to AURA v0.2.18: 1. Check every pattern in `mcp_filter`, `require_approval`, `client_tool_filter`, and scratchpad keys against [Tool-Name Patterns](/aura/configuration-reference#tool-name-patterns). Fix each pattern listed in [Patterns That Now Fail at Startup](#patterns-that-now-fail-at-startup). 2. Search `mcp_filter`, `client_tool_filter`, and scratchpad keys for `:`, `[`, and `{`. Confirm that the new meaning selects the tools you want. 3. Start the web server and look for `is advertised by` warnings in the startup log. For each shared name, confirm that the winning server is the one you want. 4. Optional. To use a shared tool from a server other than the winner, scope `mcp_filter` to that server, for example `mcp_filter = ["other-server:*"]`. You can also rename the tool on all but one server. 5. Check that your startup and readiness probe timeouts leave room for the MCP connection check: up to `[mcp].connect_timeout_secs` for each MCP server of each agent. ## Startup Errors An invalid pattern fails config load. The web server and CLI exit before they bind a port or open the REPL, and the error includes one of these messages. A character, construct, or `:` that the syntax doesn't allow: ```text theme={null} invalid tool name pattern at column : expected a name character (a-z A-Z 0-9 _ - . /), a wildcard (* ?), a class ([abc]), or an alternate ({a,b}) ``` To fix it, correct the pattern at the reported column. A literal run longer than 64 characters: ```text theme={null} tool name pattern has a run of literal characters ending at column ; the limit is 64 ``` To fix it, shorten the run that ends at the reported column, or replace part of it with `?` or `*`.