diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..7763238
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,15 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "rutster-signaling-sip"
+version = "0.0.0"
+
+[[package]]
+name = "rutster-spend"
+version = "0.0.0"
+
+[[package]]
+name = "rutster-tap"
+version = "0.0.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..191a497
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,41 @@
+# Cargo.toml — rutster workspace root.
+# Spec ref: slice-1 §2. The workspace pins shared dep versions here so
+# member crates can't drift (§2.1). Each member references with
+# `dep.workspace = true`.
+[workspace]
+resolver = "2"
+members = [
+    "crates/rutster-signaling-sip",
+    "crates/rutster-tap",
+    "crates/rutster-spend",
+]
+
+[workspace.package]
+license = "GPL-3.0-or-later"
+edition = "2021"
+repository = "https://github.com/anomalyco/rutster"
+
+# Pinned versions for all member crates. References are `foo.workspace = true`
+# in the member manifest. Keeps the dep tree unified (§2.1).
+[workspace.dependencies]
+# str0m 0.21: sans-IO WebRTC. Frame API (Event::MediaData + Writer::write).
+str0m = "0.21"
+# opus 0.3.1: libopus FFI (system libopus required — see README).
+opus = "0.3"
+# axum 0.7: HTTP signaling surface.
+axum = { version = "0.7", features = ["macros"] }
+# tokio 1: runtime driving the str0m poll loop (slice-1 deviation per §3.4).
+tokio = { version = "1", features = ["full"] }
+# dashmap 6: in-process session store.
+dashmap = "6"
+# uuid 1: ChannelId newtype backing.
+uuid = { version = "1", features = ["v4"] }
+thiserror = "1"
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+# tower: used by the binary crate's integration tests (ServiceExt::oneshot
+# on the axum Router). Axum re-exports parts of tower but the integration test
+# uses `tower::ServiceExt` directly, so it needs to be a workspace dep.
+tower = { version = "0.5", features = ["util"] }
diff --git a/crates/rutster-signaling-sip/Cargo.toml b/crates/rutster-signaling-sip/Cargo.toml
new file mode 100644
index 0000000..e123875
--- /dev/null
+++ b/crates/rutster-signaling-sip/Cargo.toml
@@ -0,0 +1,8 @@
+# crates/rutster-signaling-sip/Cargo.toml
+[package]
+name = "rutster-signaling-sip"
+version = "0.0.0"
+license.workspace = true
+edition.workspace = true
+repository.workspace = true
+description = "Rust-native trunk SIP — stub crate (filled in spearhead step 5)."
diff --git a/crates/rutster-signaling-sip/src/lib.rs b/crates/rutster-signaling-sip/src/lib.rs
new file mode 100644
index 0000000..2111346
--- /dev/null
+++ b/crates/rutster-signaling-sip/src/lib.rs
@@ -0,0 +1,23 @@
+//! # rutster-signaling-sip
+//!
+//! **Status:** stub. Fills in at spearhead step 5 (PSTN trunk).
+//!
+//! This crate will hold the Rust-native trunk SIP stack: the SIP parser,
+//! transaction layer, dialog state, and the carrier trunk integration. See
+//! [ADR-0003](../../../docs/adr/0003-sip-rust-native-trunk.md) for the
+//! "own the parser from day one" thesis and [PORT_PLAN §1](../../../docs/PORT_PLAN.md)
+//! for the surface area (`res_pjsip_session`, `chan_sip`, `_sdp_rtp` rows).
+//!
+//! Slice 1's WebRTC-only ingress needs no SIP — this stub exists to lock the
+//! crate boundary without anticipating code (spec §2.2). It depends on
+//! nothing in the workspace in slice 1. Its future dependency direction is
+//! `rutster-signaling-sip` → `rutster-call-model` + `rutster-media` (once
+//! the SDP help lives here, moved out of `rutster-media`'s WebRTC-ICE-coupled
+//! SDP module — see §3.7 of the slice-1 spec for the split rationale).
+
+#[cfg(test)]
+mod tests {
+    /// Stub crates lock boundaries; the compile-test is the lock.
+    #[test]
+    fn crate_compiles() {}
+}
diff --git a/crates/rutster-spend/Cargo.toml b/crates/rutster-spend/Cargo.toml
new file mode 100644
index 0000000..3e834dd
--- /dev/null
+++ b/crates/rutster-spend/Cargo.toml
@@ -0,0 +1,8 @@
+# crates/rutster-spend/Cargo.toml
+[package]
+name = "rutster-spend"
+version = "0.0.0"
+license.workspace = true
+edition.workspace = true
+repository.workspace = true
+description = "In-boundary spend / abuse gate — stub crate (filled in spearhead step 6)."
diff --git a/crates/rutster-spend/src/lib.rs b/crates/rutster-spend/src/lib.rs
new file mode 100644
index 0000000..2ea0d1c
--- /dev/null
+++ b/crates/rutster-spend/src/lib.rs
@@ -0,0 +1,21 @@
+//! # rutster-spend
+//!
+//! **Status:** stub. Fills in at spearhead step 6 (spend cap / abuse gate).
+//!
+//! In-boundary spend and abuse control is constitutive of the wedge
+//! ([ADR-0002](../../../docs/adr/0002-north-star-and-fused-core.md)): the
+//! runaway brain structurally cannot exceed spend or pacing because it
+//! doesn't hold the wire — the trunk termination + spend gate do, in one
+//! boundary. Pulling spend out into a service re-introduces the 3-vendor
+//! structural hole the fused vertical was chosen to eliminate.
+//!
+//! This crate will hold: spend caps, pacing caps, deny-by-default routing,
+//! rate-limits, toll-fraud pattern detection — co-located with trunk
+//! termination in `rutster-signaling-sip` (step 5). Depends on nothing in
+//! the workspace in slice 1.
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn crate_compiles() {}
+}
diff --git a/crates/rutster-tap/Cargo.toml b/crates/rutster-tap/Cargo.toml
new file mode 100644
index 0000000..2ccb1d7
--- /dev/null
+++ b/crates/rutster-tap/Cargo.toml
@@ -0,0 +1,8 @@
+# crates/rutster-tap/Cargo.toml
+[package]
+name = "rutster-tap"
+version = "0.0.0"
+license.workspace = true
+edition.workspace = true
+repository.workspace = true
+description = "Agent audio tap — stub crate (filled in spearhead step 2)."
diff --git a/crates/rutster-tap/src/lib.rs b/crates/rutster-tap/src/lib.rs
new file mode 100644
index 0000000..7843deb
--- /dev/null
+++ b/crates/rutster-tap/src/lib.rs
@@ -0,0 +1,21 @@
+//! # rutster-tap
+//!
+//! **Status:** stub. Fills in at spearhead step 2 (the tap itself).
+//!
+//! Slice 1 *pre-paves* the tap by exposing the canonical PCM boundary as
+//! the `AudioSource` / `AudioSink` traits in [`rutster_media`](../rutster-media/index.html),
+//! and wires an `EchoAudioPipe` between sink and source. Step 2 swaps that
+//! pipe for a real WSS tap client (core-as-client, brain-as-server —
+//! [ADR-0006](../../../docs/adr/0006-ingress-posture.md)). No code changes to
+//! `RtcSession` itself in step 2 — that's the test of the seam.
+//!
+//! This crate will, when filled in, re-export `PcmFrame` from
+//! `rutster-media` (one canonical home — spec §3.1) and ship the WSS
+//! tap client + the versioned framing protocol. It depends on nothing in
+//! the workspace in slice 1.
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn crate_compiles() {}
+}
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..84ef13d
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,4 @@
+# rust-toolchain.toml — pins the toolchain for reproducible builds.
+[toolchain]
+channel = "1.80"
+components = ["rustfmt", "clippy"]