MCP tool name parsing breaks when server name contains underscores

[lioryx]

Summary

McpPool::parse_prefixed_name in crates/tui/src/mcp.rs uses split_once('_')
to decompose mcp_{server}_{tool} names. When a server name itself contains
underscores — e.g. my_db — the parser splits at the wrong boundary, routing
the call to a non-existent server.

Steps to reproduce

1. Configure two MCP servers in ~/.codewhale/mcp.json:

{
  "servers": {
    "db":      { "command": "npx", "args": ["-y", "mcp-db-server"] },
    "my_db":   { "command": "npx", "args": ["-y", "mcp-db-server"] }
  }
}

2. Start codewhale and invoke the tools:
   • mcp_db_execute_sql → works correctly (server=db, tool=execute_sql)
   • mcp_my_db_execute_sql → fails with "MCP server 'my' not available"

Expected behavior

mcp_my_db_execute_sql should route to server my_db, tool execute_sql.

Actual behavior

parse_prefixed_name strips mcp_ then calls split_once('_'), yielding:

Tool name	Server (parsed)	Tool (parsed)	Correct?
mcp_db_execute_sql	db	execute_sql	✅
mcp_my_db_execute_sql	my	db_execute_sql	❌

The first _ inside the server name is mistaken for the server/tool delimiter.

Root cause

In crates/tui/src/mcp.rs, line 2248:

let Some((server, tool)) = rest.split_once('_') else { ... };

The naming convention mcp_{server}_{tool} uses a single underscore _ as
both the delimiter and a legal character in sanitized server names. There
is no way for split_once to distinguish the two.

Impact

• Any MCP server whose name contains _ (e.g. my_db, prod_pg, data_warehouse)
  produces tools that cannot be called.
• This is a silent failure: the error says "server not available", not "name
  parsed incorrectly".
• The sibling crates/mcp/src/lib.rs does not have this bug — it uses
  mcp__{server}__{tool} with double-underscore delimiters and
  splitn(2, "__"), which handles embedded underscores correctly.

Affected files

• crates/tui/src/mcp.rs — all_tools (line 2096), parse_prefixed_name
  (line 2243), all_resources, all_resource_templates
• crates/tui/src/core/engine/dispatch.rs — mcp_tool_is_read_only,
  mcp_tool_is_parallel_safe
• crates/tui/src/core/engine/turn_loop.rs — MCP tool identification

Related

• crates/mcp/src/lib.rs uses qualify_tool_name / parse_qualified_tool_name
  with mcp__server__tool double-underscore format — no bug there.

Environment

• OS: Windows 11
• codewhale version: codewhale 0.8.53 (8dff2f7)
• Install method: release binary
• Model/provider: deepseek-v4-pro / deepseek
• Terminal app: Windows Terminal
• Shell: PowerShell

[github-actions]

Thanks @lioryx for the report.

This repository is currently observing a maintainer-managed contribution gate in dry-run mode, so this issue is staying open. When enforcement is enabled, issues from contributors who are not listed in .github/APPROVED_CONTRIBUTORS will be closed automatically.

Please read CONTRIBUTING.md for the expected issue shape. A maintainer can grant issue access by commenting /lgtmi on an issue.

[Hmbown]

Fixed on the public v0.9.0 integration branch through #2747 (harvest commit 9e29c221b, now in #2762). The landed parser resolves generated mcp_<server>_<tool> names by matching the longest registered server name first, so mcp_my_db_execute_sql routes to my_db rather than my; it keeps the legacy first-underscore fallback when no registered server matches.\n\nVerification recorded for the harvest: cargo test -p codewhale-tui --bin codewhale-tui --locked mcp_pool_call_tool (3 pass), including mcp_pool_call_tool_preserves_server_names_with_underscores and mcp_pool_call_tool_prefers_longest_matching_server_name.\n\nThanks @lioryx for the clear root-cause report, and thanks @cyq1017 and @puneetdixit200 for the matching PR work. This will reach users when the v0.9.0 integration branch lands; please reopen or file a follow-up if a later build still misroutes underscored MCP server names.

[Hmbown]

Follow-up polish also landed on the v0.9.0 integration branch via #2774 (merge commit b1d4d74a1, harvest commit 8869f6a72).\n\nThat PR keeps the original routing fix intact and cleans up the adjacent display/metadata paths: runtime API MCP tool listings now reuse the registered-server parser, and approval cards show the full MCP target route instead of guessing a server from the first underscore.\n\nAdditional verification recorded there: cargo test -p codewhale-tui --bin codewhale-tui --locked underscored -- --nocapture (2 pass), cargo test -p codewhale-tui --bin codewhale-tui --locked mcp_pool_call_tool -- --nocapture (3 pass), plus fmt, diff, version, clippy, and co-author audits. Thanks again @lioryx, @cyq1017, and @puneetdixit200.