Drafted from the 2026-07-05 deployment-topology spec §2–§4: T1 solo /
T2 modular / T3 fleet (paper), the edge doctrine (bundled Caddy; rustls
Phase 1 now, Phase 2 behind four named triggers), the fleet cert story
(wildcard vs per-node; on-demand TLS rejected), node-addressed placement
via Valkey presence (routing tier + distinguished control node rejected),
and the rejected shapes (FOB decomposition, serverless, tunnels-in-prod,
NLB-TLS, k8s manifests). Status Proposed — ratification per repo process.
Closes the topology ADR reserved by ADR-0008's worked example.
Signed-off-by: Aaron D. Lee <himself@adlee.work>
ADR-0007 — Trunk/PSTN strategy: rent the transport, no first-party SIP stack.
Supersedes ADR-0003 (Rust-native trunk SIP). The 2026-06 strategic-relevance
review stress-tested ADR-0003 against the 2026 market + solo-build realities
and it did not survive: a trunk SIP/media core is the highest-cost,
lowest-differentiation square on the board (the perceived-quality battle and
the buying criteria both live above the transport), and no production-hardened
pure-Rust SIP stack exists to stand on (ezk is bus-factor-1 / pre-1.0;
str0m self-describes as 'not for production' for SIP).
rutster owns no SIP stack. PSTN reach is rented transport in three layers:
1. Primary (demo, most users) — CPaaS raw-media fork (Twilio Media Streams,
Telnyx). Media-leg ingress, core-as-server (parallel to WebRTC ingress
per ADR-0006). Use the raw-audio fork, *not* managed Voice-AI products
that would consume the reflex loop.
2. Graduation (on-prem) — out-of-tree SBC (Kamailio/FreeSWITCH/drachtio +
rtpengine) B2BUAs carrier SIP into rutster as clean RTP/tap media,
outside the trust boundary.
3. Never — a first-party Rust trunk SIP stack. rsip/ezk stay off the
critical path.
The only things rutster owns in Rust: the call model, the reflex loop, the
agent tap. Everything that touches a carrier is rented (layer 1) or
out-of-tree (layer 2).
ADR-0008 — The FOB and the green zone: the build-vs-reuse doctrine. Names
the boundary criterion implicit across ADRs 0002-0007 as one mechanical rule
every contributor (human or agent) applies the same way.
- FOB (build in Rust) — admitted only if it passes one of: hot path,
security-constitutive, differentiating. Current FOB: media termination
(rutster-media on str0m) · real-time reflexes (VAD/barge-in/jitter/pacing)
· call model (rutster-call-model) · agent tap (rutster-tap) · spend/abuse
gate (rutster-spend) · control API + state/bus trait (rutster).
- Green zone (reuse at arm's length) — its own process/container/trust
domain, never in the FOB's address space. Admitted when it fails all
three FOB tests AND a trusted, actively-maintained project already does
it well. Current green zone: Valkey (ADR-0005) · carrier trunk (ADR-0007)
· agent brain · reference GUI · object storage · KMS · OTel collector ·
container supervisor.
- 'Actively maintained' is the load-bearing gate: excludes a first-party
Rust SIP stack and webrtc-rs; admits Valkey and str0m-for-WebRTC.
- When in doubt, default to green zone. The FOB earns its members.
Restates the memory-safety pillar precisely: the FOB is 100% memory-safe
Rust; the green zone is trusted battle-tested OSS kept outside the boundary
— not an over-claim that every byte is Rust.
ADR-0003's status is flipped to Superseded with a forward-pointer to ADR-0007.
Kept as the historical record of the 'own trunk SIP + media termination in
Rust, no SBC shield' plan; reversed under the strategic-relevance review.
Folds the 2026-06-26 vision-revision pressure-test into the canonical
docs. The spec moves from Proposed to Ratified; the decisions it produced
land in the docs it said it would amend, with ADRs recording each
load-bearing reversal.
- README.md: reframe north star (AI-era contact-center engine, not
Asterisk successor); persona; revised pillars (add data-ownership,
demote WASM, promote spend-control); update 'what it is/isn't'.
- ARCHITECTURE.md: replace three-plane framing with fused per-call
vertical + composable horizontal platform; remove control<->media
hot-path gRPC hop; make the agent tap the central interface; add
DX spine + GUI-as-API-client + k8s declarative/operational model.
Also: 'too slow to police' -> 'too slow to enforce' (terminology).
- PORT_PLAN.md: recharacterize as capability checklist (not template);
graduate contact-center capabilities to first-class domain; Rust-native
trunk SIP rows; WASM demoted; thin-slice + capability ladder phasing.
- ADR-0001: marked Superseded by ADR-0003.
- ADR-0002 (new): north star + fused per-call core.
- ADR-0003 (new): Rust-native trunk SIP, no SBC shield.
- ADR-0004 (new): GPL-3.0-or-later license.
- ADR-0005 (new): Valkey as event bus + state store.
- ADR-0006 (new): WebRTC-first ingress; SIP endpoint deferred.
- vision-revision spec: status -> Ratified 2026-06-26.
Record the SIP edge decision and align the docs:
- docs/adr/0001-sip-strategy.md: layered strategy (own Rust parser, rent the
interop tail via a Kamailio + rtpengine SBC, grow native core behind the shield);
pjproject FFI explicitly rejected for breaking the memory-safety thesis at the
most exposed seam.
- PORT_PLAN §1 + open decisions: SIP row updated to the decided strategy.
- ARCHITECTURE: "biggest technical risk" now points at ADR-0001.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C2bfD7MkqEdfnMXxXBu456
