Where does the bug appear (feature/product)?
Cursor IDE
Describe the Bug
MCP: cursor-ide-browser ready (~16 tools) in parent
Summary
Launching a specialized browser subagent (Task + subagent_type: “browser-use”) fails at bootstrap before any model turn. Parent agent can use the same browser MCP successfully via GetMcpTools → CallMcpTool.
Exact error
[internal] Required tool GET_MCP_TOOLS not found in allTools
Subagent transcript is one line only — no browser_navigate, no snapshot.
Repro artifacts
Item
Value
Parent chat
dbcef4c5-0e8d-4a1b-b3d8-2b0ca7a00364
Failed subagent
988f462e-053e-41d9-bdf2-960531cb3f98
Launch
Task, browser-use, claude-4.6-sonnet-high-thinking, run_in_background: true
Follow-up matrix chat
36013f5d-c790-4a31-be87-970c42e97b59
Repro matrix (minimal URL https://example.com)
ID
Variant
Result
A
Parent GetMcpTools → browser_navigate → browser_snapshot
PASS
B
Task browser-use, foreground, no model
FAIL — Invalid enum value (type not in Task enum)
C
Task browser-use, background
FAIL — same enum reject
D
Task browser-use + model override
FAIL — same enum reject
E
Task browser
FAIL — same enum reject
F
Task generalPurpose told to use browser
PARTIAL — child has GetMcpTools/CallMcpTool; navigate may hit No browser tab available
G
Reduce MCP count, retest B
SKIP — B never launches on this surface; MCP catalogs identical when OURA hit GET_MCP_TOOLS
Historical contrast
Earlier launches used tool name Subagent + browser-use with flat MCP tool names (cursor-ide-browser-browser_navigate). That worked. New meta path (GetMcpTools) works on parent and on generalPurpose, but specialized browser-use children die asserting GET_MCP_TOOLS in allTools.
Expected vs actual
Expected (docs): Built-in browser subagent; subagents inherit MCP from parent.
Actual: Docs say browser; models still emit browser-use; Composer Task enum often omits both; when browser-use does launch, child lacks GET_MCP_TOOLS and dies immediately.
Suspected cause
Browser-specialized child bootstrap asserts meta-tool GET_MCP_TOOLS (SCREAMING_SNAKE) in allTools, but provisioning only exposes parent GetMcpTools (camelCase) — or does not attach MCP meta tools to the specialized browser child at all.
Steps to Reproduce
Exact error
[internal] Required tool GET_MCP_TOOLS not found in allTools
Subagent transcript is one line only — no browser_navigate, no snapshot.
Repro artifacts
Item
Value
Parent chat
dbcef4c5-0e8d-4a1b-b3d8-2b0ca7a00364
Failed subagent
988f462e-053e-41d9-bdf2-960531cb3f98
Launch
Task, browser-use, claude-4.6-sonnet-high-thinking, run_in_background: true
Follow-up matrix chat
36013f5d-c790-4a31-be87-970c42e97b59
Repro matrix (minimal URL https://example.com)
ID
Variant
Result
A
Parent GetMcpTools → browser_navigate → browser_snapshot
PASS
B
Task browser-use, foreground, no model
FAIL — Invalid enum value (type not in Task enum)
C
Task browser-use, background
FAIL — same enum reject
D
Task browser-use + model override
FAIL — same enum reject
E
Task browser
FAIL — same enum reject
F
Task generalPurpose told to use browser
PARTIAL — child has GetMcpTools/CallMcpTool; navigate may hit No browser tab available
G
Reduce MCP count, retest B
SKIP — B never launches on this surface; MCP catalogs identical when OURA hit GET_MCP_TOOLS
Historical contrast
Earlier launches used tool name Subagent + browser-use with flat MCP tool names (cursor-ide-browser-browser_navigate). That worked. New meta path (GetMcpTools) works on parent and on generalPurpose, but specialized browser-use children die asserting GET_MCP_TOOLS in allTools.
Expected vs actual
Expected (docs): Built-in browser subagent; subagents inherit MCP from parent.
Actual: Docs say browser; models still emit browser-use; Composer Task enum often omits both; when browser-use does launch, child lacks GET_MCP_TOOLS and dies immediately.
Operating System
MacOS
Version Information
Cursor: 3.11.19 stable
Commit: bf249e6efb5b
OS: Darwin arm64
MCP: cursor-ide-browser ready (~16 tools) in parent
For AI issues: which model did you use?
AUTO
Does this stop you from using Cursor
No - Cursor works, but with this issue