Protocol-compliance and reliability hardening across the Rust core. The public Dart surface (ntsQuery, ntsWarmCookies, NtsServerSpec, NtsTimeSample, NtsError) is unchanged; consumer-visible behaviour improves on the timeout, cookie-cache, and error-classification paths. Rust crate nts_rust is bumped from 0.1.0 to 0.2.0 to mark the internal protocol-validation tightening; the bindings (lib/src/ffi/) and Native Assets bridge are unaffected.

NTS-KE handshake (rust/src/nts/ke.rs) #

• Replace the OS-default TCP connect with a deadline-aware connection loop that honours the caller's timeoutMs. Earlier releases passed the budget only to the read/write side of the socket and let TcpStream::connect block on the platform default (typically 75 s on macOS / 21 s on Linux), which made ntsQuery(..., timeoutMs: 5000) hang for the full kernel default when the KE endpoint blackholed SYNs. The new loop iterates the resolved address list, computes the per-attempt deadline from the remaining budget, and surfaces a KeError::Io(ErrorKind::TimedOut) on the first exhausted attempt rather than the last. Mapped through From<KeError> for NtsError to NtsError.timeout so the Dart-side switch arm is reached.
• Regression test connect_with_timeout_respects_budget_for_unroutable_ip exercises the deadline against 192.0.2.1 (RFC 5737 TEST-NET-1) and asserts the call returns within 1.5× the configured budget.

Cookie management (rust/src/api/nts.rs) #

• Introduce a monotonically-increasing generation: u64 on Session and propagate it into QueryContext::session_generation so each in-flight NTPv4 query carries the identity of the handshake that produced its cookies. Session::deposit_cookies now gates the cookie-jar update on a matching generation: cookies extracted from a response signed under generation N are silently dropped if the session has been re-handshaked to generation N+1 between dispatch and receipt. This closes a cross-session poisoning window where a late response from a stale session could install cookies bound to retired keys, causing the next ntsQuery to dispatch unauthenticatable cookies and fail the AEAD seal.
• The generation counter is also incremented on every successful Session::rehandshake, so the stale-cookie filter applies symmetrically to both concurrent-query races and explicit ntsWarmCookies invocations during an in-flight query.

NTPv4 header validation (rust/src/nts/ntp.rs) #

• Add STRATUM_UNSYNCHRONIZED_FLOOR = 16 and reject any post-AEAD reply with stratum >= 16 as NtpError::Unsynchronized. RFC 5905 reserves stratum 16 as the "unsynchronized" sentinel and 17–255 as reserved; previous versions only filtered LI=3, so a server in the alarm condition could surface a wall-clock offset to the discipline loop if it left LI=0.
• Reorder the validation so the Stratum-0 short-circuit (Kiss-o'-Death) runs before the LI=3 / stratum-ceiling check. Real-world KoD packets routinely arrive with LI=3 because the server has no synchronised time to advertise; the previous ordering swallowed the 4-octet kiss code (RATE, DENY, RSTR, NTSN, …) into a generic Unsynchronized error and stripped the diagnostic the caller needs to choose a back-off strategy.
• Validation remains positioned after AEAD open() and the origin-timestamp check. stratum and the leap indicator are part of the NTP AAD, so by this point the server has signed the value; off-path attackers cannot forge KoD or stratum-16 to disrupt the client. The post-AEAD ordering is pinned by the *_after_seal_*_tamper_as_aead_failure test family.
• New regression tests:
  • parse_response_prefers_kod_over_unsynchronized_when_both_set pins the new precedence (Stratum 0 + LI=3 ⇒ KissOfDeath).
  • parse_response_rejects_invalid_high_stratum pins the new stratum-ceiling check (stratum 16 + LI=0 ⇒ Unsynchronized).
• Broaden the Display arm and rustdoc on NtpError::Unsynchronized to "server reports unsynchronized clock (LI=3 or stratum >= 16)" so the diagnostic accurately reflects both triggers; the message passes through NtsError::NtpProtocol(..) to the Dart side unchanged.

Housekeeping #

• rust/src/nts/records.rs: replace body.len() % 2 != 0 with !body.len().is_multiple_of(2) in decode_u16_array to satisfy the clippy::manual_is_multiple_of lint (warn-by-default in clippy 1.92, surfaced once cargo clippy --all-targets -- -D warnings was added to the release gate). Behaviour is unchanged.

Verification #

• cargo test --lib: 95 passed, 0 failed, 3 ignored (live-network).
• cargo clippy --tests --all-targets -- -D warnings: clean across the workspace.

Documentation and published-tarball hygiene. No changes to the published Dart surface, the Rust crate, or the Native Assets bridge.

• example/lib/src/state/nts_controller.dart: prepend a 46-line dartdoc block to runQuery that documents the NTS-KE cold-start cost (TCP + TLS 1.3 + KE handshake + first NTPv4 exchange ≈ 4 RTTs end to end, no session-ticket resumption), the steady-state path (cached session keys, in-band cookie pool replenishment, ~1 RTT), and the attribution boundary (the latency is RFC 8915 protocol overhead, not RustLib.init(), the Native Assets pipeline, or per-call FFI cost). Includes a production note pointing at example/main.dart's ntsWarmCookies() warm-then-query pattern as the canonical way to amortize the cold-start cost; the GUI deliberately does not follow it so that the protocol observation tool surfaces the unmasked latency.

• Repository-wide documentation refactor (7 files: pubspec.yaml, analysis_options.yaml, DEVELOPMENT.md, README.md, example/.pubignore, example/README.md, tool/check_bindings.dart) to replace meta-commentary about pub.dev scorecards, pana rubrics, and tag-drop heuristics with objective technical justifications. The platform allow-list now reads as RFC 8915's raw TCP/UDP requirement plus rustls+ring's lack of a wasm32 target; the FRB pin is justified by the silent-memory-corruption risk of a wire-format mismatch; the analyzer-exclude removal is justified by lockstep with the consumer's analyzer view; the // ignore_for_file: directives in lib/src/ffi/** are justified by public_member_api_docs being enabled and the FFI surface not being excluded. The IANA AEAD-registry reference in example/GUI_GUIDE.md is preserved as a legitimate protocol citation.

• .pubignore (new, root): introduce a root .pubignore that mirrors the root .gitignore patterns (per dart.dev/go/pubignore, a directory's .pubignore replaces its .gitignore for publish purposes) and additionally excludes consumer-irrelevant files: AGENTS.md, CLAUDE.md (AI-agent guidance), ARCHITECTURE.md, DEVELOPMENT.md (self-identified contributor-only documentation), analysis_options.yaml (consumer analyzers read the consumer's own config), flutter_rust_bridge.yaml (FRB codegen config; bindings ship pre-generated), tool/ (CI drift check for FRB regeneration), and test/ (internal FFI smoke test, not a public-API verifier).

• example/.pubignore: add analysis_options.yaml and test/ to the example's exclusion list for the same reasons as the root. The canonical consumer entry point remains example/main.dart.

• Net effect verified via dart pub publish --dry-run: the published tarball drops from 840 KB (1.0.6) to 824 KB, twelve maintainer-only files are stripped, and the warning/hint output is unchanged. No source files in lib/, rust/, or hook/ are touched, so the binding drift gate and Native Assets build hook are unaffected.

Binding regen consequent on the 1.0.5 analyzer-exclude removal. No changes to the published Dart surface, the Rust crate, or the Native Assets bridge.

• lib/src/ffi/frb_generated.dart: regenerate against the current analysis_options.yaml. Removing the analyzer.exclude: [lib/src/ffi/**] block in 1.0.5 (nts-2cq) had a side effect that the bindings CI job did not surface until the next commit that re-triggered the job: flutter_rust_bridge_codegen runs an analyzer-aware fix-up over the Dart it emits before exiting, that pass was a no-op while the FFI files were excluded, and with the exclude gone the pass applies prefer_final_locals and prefer_const_constructors to the synthesized dispatcher boilerplate. The committed file (last regenerated in 1.0.2, 0349077) was therefore stale relative to the codegen's deterministic output. The regen is purely cosmetic — var locals inside dco_decode_nts_error / sse_decode_* become final, and the two nullary NtsError variants gain const prefixes — and produces no wire-format or public-API change. The file-level // ignore_for_file: directives managed by tool/check_bindings.dart still suppress both rules so future codegen output that emits a non-final local or non-const constructor remains acceptable to pana without re-failing the drift gate.

Example clarity and pub.dev metadata fidelity. No changes to the published Dart surface, the Rust crate, or the Native Assets bridge.

• example/main.dart: switch the minimal sample from a single ntsQuery() call to a warm-then-query flow that calls ntsWarmCookies() first and then ntsQuery(). The original one-call form lumped the NTS-KE handshake into the same latency budget as the NTPv4 exchange and never made the cookie pool visible; the new form mirrors the production access pattern, surfaces the cookies_remaining counter on NtsTimeSample, and gives readers a self-contained reference for both stages of the protocol. example/example.md is regenerated as a byte-for-byte fenced mirror so the pub.dev Example tab tracks the runnable sample. The exhaustive NtsError switch and the RustLib.init() bootstrap order are unchanged.

• example/example.md: drop the developer-facing meta-commentary about the rendering quirk that motivated the file's existence (pana priority list, the example/main.dart shadowing dance from 1.0.3 / 1.0.4). The fenced sample is the consumer-visible artefact; the rendering history is recorded in this changelog and in the nts-9td commit message, not in the file pub.dev publishes.

• analysis_options.yaml: remove the analyzer.exclude: [lib/src/ffi/**] block so local dart analyze / flutter analyze runs see the same surface pana sees on pub.dev. The FRB-generated files in lib/src/ffi/ carry file-level // ignore_for_file: directives (managed by tool/check_bindings.dart and landed in 1.0.2) for the rules they cannot satisfy, which pana respects but analyzer.exclude does not — keeping both meant local CI was strictly more permissive than the pub.dev scorecard. With the exclude removed, lint drift between the two environments is impossible.

• pubspec.yaml: add a top-level platforms: allow-list with android, ios, macos, linux, windows. Earlier releases shipped without this block, which let pana award the web and wasm platform tags on the strength of the Dart surface compiling cleanly under dart2js / dart2wasm — but actual runtime use of any nts API on Web cannot work, because RFC 8915 needs raw TCP for NTS-KE on :4460 and raw UDP for NTPv4 on :123 (neither of which browsers expose to web pages), and the rustls + ring + rustls-platform-verifier stack does not target wasm32-unknown-unknown. Declaring the supported platforms explicitly drops both incorrect tags from the next pana rescore so the pub.dev scorecard reflects the package's true platform surface.

pub.dev Example tab fix (take two). No runtime changes.

• Add example/example.md containing the minimal NTS-KE sample as a fenced ```dart block plus a pointer to the Flutter GUI showcase at example/lib/main.dart. The 1.0.3 rename of the minimal sample to example/main.dart did not unblock the Example tab: empirical check on the published version-pinned URL still rendered example/lib/main.dart. The bracket notation example[/lib]/main.dart in dart.dev's package-layout doc is shorthand for two separate slots in pana's selection list, with the lib/ form ranked higher than the bare form. The actual list lives in pana/lib/src/maintenance.dart:

  1. example/README.md
  2. example/example.md ← new in 1.0.4, secures the slot
  3. example/lib/main.dart (GUI showcase, no longer rendered)
  4. example/bin/main.dart
  5. example/main.dart (1.0.3 rename target, also no longer rendered)

  Slot 2 beats slot 3, so the new example/example.md finally wins over example/lib/main.dart. The minimal sample at example/main.dart stays in the archive as the runnable Flutter target; the .md is just a syntactic mirror so pub.dev picks it.

• No changes to the published Dart surface, the Rust crate, or the Native Assets bridge. The two new lines in pubspec.yaml and CHANGELOG.md are the only metadata edits.

pub.dev Example tab fix. No runtime changes.

• Rename example/example.dart to example/main.dart so pub.dev's Example tab renders the intended minimal single-call sample. pub.dev picks the rendered file from a hardcoded priority list documented at https://dart.dev/tools/pub/package-layout#examples; the previous layout placed the minimal sample at priority 5 (example[/lib]/example.dart) where it was shadowed by the Flutter GUI showcase at priority 2 (example/lib/main.dart). The bare example/main.dart slot also sits at priority 2 but wins over the lib/ variant, so the rename promotes the minimal sample without removing the GUI showcase from the published tarball.
• Update example/README.md to spell the GUI entry point explicitly as flutter run -t lib/main.dart (or -t example/lib/main.dart from the repo root) so contributors don't accidentally launch the new top-level example/main.dart as the Flutter target.
• Update root README.md and ARCHITECTURE.md to reference the new path. The 1.0.1 changelog entry that introduced example/example.dart is left unchanged for historical accuracy.

Static-analysis score recovery. No runtime changes.

• Suppress pana-only lints across the FRB-generated bindings via the // ignore_for_file: directive of each file, applied as a post-codegen patch step in tool/check_bindings.dart. pana's static-analysis run uses a stricter ruleset than flutter_lints and surfaced 117+ INFO lints against the synthesized freezed wrappers (NtsError), auto-generated default constructors (NtsServerSpec, NtsTimeSample), and dispatcher boilerplate that FRB cannot back with Rust docstrings, costing 10 pub points. Patched files and rules:
  • lib/src/ffi/api/nts.dart: public_member_api_docs.
  • lib/src/ffi/frb_generated.dart: public_member_api_docs, prefer_final_locals, prefer_const_constructors.
  • lib/src/ffi/frb_generated.io.dart: public_member_api_docs.
  • lib/src/ffi/frb_generated.web.dart: public_member_api_docs. Local pana 0.23.12 now reports 160 / 160 against the working tree.

Documentation and pub.dev metadata polish. No runtime changes.

• Restructure README around a What → Why → How flow and offload the Rust toolchain, build hooks, and crate breakdown into new ARCHITECTURE.md and DEVELOPMENT.md reference documents.
• Add a self-contained example/example.dart for pub.dev's Example tab.
• Resolve two dartdoc unresolved-reference warnings in lib/src/ffi/api/nts.dart by replacing Rust intra-doc link syntax with literal values in the upstream Rust docstrings and regenerating the bindings.
• Trim the package description to fit pana's 180-char ceiling, add five pub.dev topics (ntp, time, networking, security, cryptography), and register screenshots/gui_showcase.png as the package listing screenshot.
• Expand the inline comment on the flutter_rust_bridge: 2.12.0 pin to document the wire-format rationale and the accepted pana warning.

Initial stable release.

Protocol #

• Network Time Security (RFC 8915) client implementing the full NTS-KE handshake (TLS 1.3, ALPN ntske/1, port 4460) followed by AEAD-protected NTPv4 (RFC 5905) over UDP/123.
• AEAD algorithms: AES-SIV-CMAC-256 (IANA ID 15, default) and AES-128-GCM-SIV (IANA ID 16), negotiated during NTS-KE.
• Cookie management: in-memory cookie jar with automatic refresh via ntsWarmCookies() when the pool is exhausted.

API #

• ntsQuery({required NtsServerSpec spec, required int timeoutMs}) returns Future<NtsTimeSample> with server transmit time, round-trip duration, stratum, negotiated AEAD ID, and fresh cookie count.
• ntsWarmCookies({required NtsServerSpec spec, required int timeoutMs}) forces a fresh handshake and reports the number of cookies received.
• NtsError sealed class with eight typed variants (invalidSpec, network, keProtocol, ntpProtocol, authentication, timeout, noCookies, internal) for exhaustive pattern matching.

Implementation #

• Cryptographic core implemented in Rust (rustls for TLS 1.3, aes-siv / aes-gcm for AEAD, ring for primitives).
• Bridged to Dart via flutter_rust_bridge 2.12.0 (pinned exactly to match the Rust crate's wire format).
• Bundled through the stable Native Assets API (hook/build.dart + native_toolchain_rust); no manual cargo invocation required from consumers.

Platform support #

Android, iOS, macOS, Linux, Windows. Web is not supported (no UDP socket primitive in the browser).

Build #

• Default release builds use the log-strip Cargo feature, eliding info! / debug! / trace! format strings at compile time; warn! and error! survive for diagnostics.
• The verbose_logs user-define in pubspec.yaml opts into a debug build with full logging (including rustls protocol traces) for development.

Tooling #

• tool/check_bindings.dart regenerates FRB bindings and fails CI if the committed Dart bindings or rust/src/frb_generated.rs drift from the generator output.
• CI matrix exercises both the declared SDK floor (Flutter 3.38.10 / Dart 3.10.9) and the pinned development version (Flutter 3.41.7 / Dart 3.11.5).

Requirements #

• Dart ^3.10.0, Flutter >=3.38.0. The lower bound matches the hooks package (>=1.0.3) requirement.
• Native Assets API (stable since Flutter 3.24).