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Add `ss-local --printable-salt` / `"printable_salt": true`, disabled by default. For each outgoing TCP salt it picks a prefix length uniformly from 6-12 bytes and samples those bytes as printable ASCII (0x20-0x7e) immediately before key derivation. The salt stays 32 bytes with no framing or markers, so the wire format is unchanged and any stock server interoperates. Only chacha20-ietf-poly1305 and aes-256-gcm are accepted; other ciphers fail at startup. UDP, server responses, and AEAD-2022 are untouched. Crypto unit tests cover length distribution, empty first writes, exact framing overhead, salt-tail preservation, byte-at-a-time decryption, tampering and replay rejection. CLI tests check local-only exposure and cipher rejection via flag, config key and bad config type. interop.py gains --printable-salt and --server-bin for independent stock servers. docs/printable-salt.md records the design, entropy bound, fingerprint caveats and route-experiment procedure; docs/encoding-experiments.md and tests/experiments/ hold the Base85/lowpop85/TLS outer-transport prototypes. docs/measurements/printable-salt-2026-09-23/ archives the sanitized results of the aborted field trials. Co-authored-by: Claude <noreply@anthropic.com>