fix: avoid mutating shared routerOptions across instances#6515
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metcoder95
approved these changes
Feb 20, 2026
Eomm
approved these changes
Feb 20, 2026
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Problem
Reusing the same
routerOptionsobject across multiple Fastify instances can fail with:TypeError: Cannot read properties of null (reading 'server')buildRouterOptions()was mutating the user-providedoptions.routerOptionsobject in place while filling defaults (including instance-bound callbacks likedefaultRoute/onBadUrl).Fix
options.routerOptionsbefore filling defaultsTests
Should allow reusing a routerOptions object across instancesShould not mutate user-provided routerOptions objectt.after()so instances are always closedFixes #6512