JSON.parse returns unexpected keys after decoding specified JSON key

### Version 24.16.0 ### Platform ```text Microsoft Windows NT 10.0.20348.0 x64 Linux [REDACTED] 5.14.0-611.54.3.el9_7.x86_64 #1 SMP PREEMPT_DYNAMIC Thu May 7 16:31:24 EDT 2026 x86_64 x86_64 x86_64 GNU/Linux ``` ### Subsystem _No response_ ### What steps will reproduce the bug? ### Background I was fuzzing a custom JSON parser by generating random stuff, serializing them with `JSON.stringify`, parsing them with my parser, and cross-checking the result against native `JSON.parse`. The fuzz test reported divergences somehow, and during the troubleshoot I found this very weird bug. I'm able to reproduce it on two machines (Windows / Linux, Node 24.16.0 x64), but unable to reproduce it on my own machine with Node 20 / 16, nor can I reproduce it in ChatGPT's sandbox (Node v22.16.0 and Linux I guess). ### Trigger sequence definition For a given sequence pair: ```js const CANARY = '{"\\r":"value are not important","\\n":"just keys"}', CHECK = '\n'.charCodeAt(0); const TRIGGER = '{\"\\r\":[],\"\\\\\":0}'; ``` The first key of two sequences should be the same (`\r` vs `\r`, or `\f` vs `\f`, etc.). And the second of canary should be another escaped control string (We use `\n` in this case. These are all valid trigger sequences: ```js const CANARY = '{"\\r":"value are not important","\\f":"just keys"}', CHECK = '\f'.charCodeAt(0); const TRIGGER = '{"\\r":[],"\\\\":0}'; const CANARY = '{"\\f":"value are not important","\\n":"just keys"}', CHECK = '\n'.charCodeAt(0); const TRIGGER = '{"\\f":[],"\\\\":0}'; const CANARY = '{"\\n":"value are not important","\\f":"just keys"}', CHECK = '\f'.charCodeAt(0); const TRIGGER = '{"\\n":[],"\\\\":0}'; const CANARY = '{"\\f":"value are not important","\\r":"just keys"}', CHECK = '\r'.charCodeAt(0); const TRIGGER = '{"\\f":[],"\\\\":0}'; ``` ### Minimal reproduce snippet This is a hand-written version without AI slop. ```js console.info('Node version: ' + process.versions.node); const CANARY = '{"\\r":"value are not important","\\f":"just keys…