chronogrid/DECISION_LOG.md

Architectural Decision Log (ADL)

[2026-08-09] - ADL-001: Distributed Local-First System Baseline

• Status: Accepted
• Context: Design a multi-platform (Windows, Linux, Android, Headless) productivity engine for time, project, and note management without centralized servers.
• Decision: Adopted Rust core with SQLCipher local storage, Automerge CRDT delta sync over libp2p, and Flutter presentation layer bound via C-FFI.

[2026-08-19] - ADL-003: chronogrid_core Crate – SQLCipher 4.x Database Initializer

• Status: Accepted
• Context: Task 1.3 required implementing the chronogrid_core crate with SQLCipher 4.x encrypted database initialization matching docs/API_CONTRACTS/schema.sql.
• Decision:
  • rusqlite v0.31 with bundled-sqlcipher-vendored-openssl feature bundles both SQLCipher and OpenSSL, ensuring a hermetic build with no external C library dependencies.
  • The 32-byte Argon2id-derived master key is passed as a raw hex key via PRAGMA key = "x'…'", bypassing SQLCipher's internal PBKDF2 derivation since Argon2id already provides equivalent or stronger protection.
  • PRAGMA cipher_compatibility = 4 enforces SQLCipher 4.x defaults (AES-256-CBC, HMAC-SHA512 page auth, 64 KiB page size).
  • PRAGMA foreign_keys = ON is set on every connection per the schema specification.
  • The canonical schema SQL from docs/API_CONTRACTS/schema.sql is embedded via include_str! at compile time, ensuring single-source-of-truth alignment without runtime file I/O.
  • Post-initialization validation confirms all 6 expected tables exist (namespaces, projects, tasks, notes, task_note_links, ingestion_logs) plus 4 indexes.
  • Database struct provides open(path, key) for file-backed and open_in_memory(key) for test databases; key length is validated at 32 bytes.
  • 11 unit tests cover: table/index creation, FK enforcement, cascade deletes, wrong-key rejection, key length validation, schema idempotency, and CRUD round-trips across all tables.

[2026-08-09] - ADL-002: chronogrid_crypto Crate – Argon2id KDF & OS Keychain

• Status: Accepted
• Context: Task 1.2 required implementing the chronogrid_crypto crate with Argon2id master-key derivation and OS-native keychain bindings per docs/ARCHITECTURE/02-security-and-crypto.md.
• Decision:
  • Argon2id parameters pinned: 64 MiB memory, 3 iterations, 4 threads, 16-byte random salt, 32-byte output.
  • DerivedKey struct implements Zeroize + Drop to scrub sensitive memory on scope exit.
  • OS keychain abstracted via keyring crate v3 (Windows Credential Manager / DPAPI, Linux SecretService / libsecret). Android keychain is excluded (cfg(not(target_os = "android"))) and will be handled by Flutter KeyStore bridge in Task 1.5.
  • Raw key material is Base64-encoded before credential-store insertion for UTF-8 backend compatibility.
  • Inline Base64 encode/decode helpers avoid adding an external Base64 dependency.