The pkg/translations TranslationHelper is first-write-wins on cache
hits: if two callers pass the same key with different fallback
strings, only the first fallback is remembered. Both ListIssueFields
(MS-aware) and ListIssueFieldsLegacy shared the translation key
TOOL_LIST_ISSUE_FIELDS_DESCRIPTION, so at runtime the second-registered
variant (legacy) inherited the first's description — leaking the
MS-flavoured 'single_select, multi_select' text into the FF-off surface.
Only list_issue_fields was affected: issue_write and list_issues use
identical top-level descriptions across variants (their MS-vs-legacy
differentiation is in InputSchema property descriptions, which are
hardcoded strings not routed through the translation helper).
Fix: give the legacy variant its own translation key
(TOOL_LIST_ISSUE_FIELDS_LEGACY_DESCRIPTION). Simplify buildListIssueFields
to accept the already-resolved description string, so the two variants
resolve their translation before calling the shared builder.
Live-verified against a local binary:
- FF off: description no longer contains 'multi_select'
- FF on: description contains 'multi_select'
Regression test: Test_ListIssueFields_LegacyDoesNotLeakMSDescription
UnderRealTranslationHelper uses an in-test cache that mimics the real
helper's first-write-wins behaviour. Confirmed the test fails if both
variants share a key and passes with them split.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Owen Niblock
60ebbe13a6