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+Copyright (C) 2026 Doan Luu Duc Tai <doan@luuduct.ai>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License as
+published by the Free Software Foundation, either version 3 of the
+License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+
+CHAT CRYPTOGRAPHY COMPATIBILITY PROBE
+
+    Experimental, local-only work on feature/private-chat. This is a
+    cryptographic compatibility test, not a messaging application. Do not use
+    it for private conversations or real identities. It creates temporary
+    identities in memory and discards them; it does not create user chat files.
+
+    Fixed encryption: RFC 9980 ML-KEM-1024 + X448, OpenPGP v6.
+    Tested signing: ML-DSA-87 + Ed448, OpenPGP v6.
+    Backend: Sequoia 2.4.2 with OpenSSL 3.6.5. No algorithm substitution or
+    vulnerability-advisory exception was used. The first checkpoint's Rust
+    backend is historical and no longer selected.
+
+    See ../../docs/CHAT-OPENSSL-MIGRATION.txt for the complete decision record,
+    pinned source hashes, build flags, capability boundaries, dependency-policy
+    exceptions, observed results, limitations, and reproduction commands.
+    ../../docs/CHAT-SECURITY-REVIEW.txt records the original dependency findings.
+    ../../docs/CHAT-DESIGN.txt describes the planned application.
+
+QUICK CHECKS FROM THE STACK ROOT
+
+        cargo test --locked -p stack-chat-crypto
+        cargo run --locked -p stack-chat-crypto
+        sh infra/chat/build-openssl-wasi.sh
+        PLAYWRIGHT_BROWSERS_PATH="$PWD/.tools/browsers" node crates/chat-crypto/tests/browser.mjs
+        cargo stack check
+
+    Native checks require OpenSSL >=3.5 development files and libclang.
+    The cross-build script currently supports Linux x86_64 development hosts.
+    Browser tooling installation is documented in the migration record.
+
+    The harness serves only a blank document, a readable AGPL JavaScript WASI
+    bridge, and the new WASI binary on an ephemeral loopback port. It verifies
+    the actual OpenSSL backend, cryptographic round trips, tampering and invalid
+    credential rejection, repeated fresh instances, and failure without CSPRNG.
+    It checks for external requests and persistent browser application state.
+
+    The application itself, private chat-file envelope, and session workflow
+    remain unimplemented. LibreJS acceptance has not been tested; there is no
+    public chat page or compliance badge. The fixture password is public test
+    data, not a configured secret. No .env file or user private key is needed.