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We present RUDRA-512, a 512-bit cryptographic hash function that introduces a novel preprocessing pipeline fusing Byte-Pair Encoding (BPE) tokenization with a multi-stage ARX (Add-Rotate-XOR) compression function. Unlike all standard hash functions in the SHA-2, SHA-3, and BLAKE families, RUDRA-512 operates on a token-level representation of the input rather than on raw bytes, producing what we term Input-Dependent Padding (IDP): two inputs of identical byte length but different semantic content produce structurally distinct token sequences, and therefore fundamentally different internal padding structures, before a single compression round is performed. The construction combines BPE tokenization (cl100k_base vocabulary, 100,256 tokens), Scattered Salt Injection, SipHash-2-4-keyed Feistel pre-whitening, Davies-Meyer ARX block absorption with a 512-bit chaining state, and HAIFA style double-finalisation. Empirical evaluation on the NIST SP800-22 randomness test suite (100 binary sequences, all 15 statistical test families) shows all tests passing at or above the required threshold, with an observed avalanche coefficient of 50.13%, bit-frequency of 50.03%, and Shannon entropy of 1.000000 bits per bit. RUDRA-512 is published as open-source software under the Apache 2.0 licence and is available as native C++17 with Python and Node.js bindings.