Finding / flue
2026-09-21-flue-2-1-0-per-tool-timeoutms-mcp-tool-annotations-preserved-configurable-trace-budgets
2.1.0: per-tool timeoutMs, MCP tool annotations preserved, configurable trace budgets. A tool can declare timeoutMs; on expiry the harness aborts
the tool’s signal and settles a ToolTimeoutError the model sees, so one hung
call no longer eats the submission’s durability budget. Tools from
createMcpConnection() now carry server-sent annotations (for example
destructiveHint); the release notes state Flue does not change behavior based
on them and the docs call them not a security boundary. Trace content budget
per span is settable.
Channel: tagged-release (preceded by 2.1.0-next.0 and next.1 preview-or-beta). Half: capability. Date: 2026-09-18.
Operator consequence: Try timeoutMs on every network-bound tool; it
removes a hand-rolled AbortController wrapper. MCP annotations let your own
approval gate read destructiveHint, but they are server-asserted: gate on them
only for servers you trust. If you run Workers AI dynamic models, 2.0.8’s warning
is the first signal that your cost dashboards showed $0 for unknown, not free.
Receipt
Finding metadata
Run: 2026-09-21-weekly-digest-2026-08-20_2026-09-21-frontier-v0
Finding ID: 2026-09-21-flue-2-1-0-per-tool-timeoutms-mcp-tool-annotations-preserved-configurable-trace-budgets
Profile citations
- Flue / claim / tool-timeout-and-mcp-annotations-2-1-0
Source links
Primary links, including exact changelog lines when available.