diff --git a/CONTEXT.md b/CONTEXT.md
index 418ec45..8ad2f03 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -56,6 +56,36 @@ _Avoid_: Armonia (the whole stack), workspace, folder
 The scheduled agentic-work context — a registered set of jobs that run unattended on a schedule, each producing staged, reviewable output rather than direct changes. Already live as the team-facing nightly Slack automation in `harmoniqs/amico` (morning brief, per-member briefs, EOD check-in, news posts) on GitHub Actions; the unified context grows it to all scheduled agentic work, including local repo/Julia-heavy jobs. Subsumes the dream cycle: `dream-reflect` runs as one job within Notturno. One night's run of the registered jobs is "tonight's notturno".
 _Avoid_: cron, scheduler (as concept names), night shift
 
+### Fleet & serving
+
+**Server mode**:
+The per-machine stance for where Sessions are served from, in three values. `standalone` — this machine spawns and owns its own chat server (the default; the only mode that ever spawns). `server` — this machine runs the Canonical Server as a system service and the panel attaches to it. `client` — this machine never serves; the panel attaches to the Canonical Server through a Managed Tunnel. Machine-scoped, never synced: a synced "client" landing on the server would silence the fleet.
+_Avoid_: profile, spawn vs attach (as concept names)
+
+**Canonical Server**:
+The one chat server that owns the fleet's Session store — the single writer every panel attaches to. Runs as a system service on the machine in `server` Server mode, available headless (no editor required). Only one may exist per Fleet.
+_Avoid_: master, primary, host
+
+**Fleet**:
+The user's machines acting as one logical studio: exactly one Canonical Server plus zero-or-more clients, all attaching to the same Session store.
+_Avoid_: mesh, cluster
+
+**Local fallback**:
+The deliberate, user-invoked escape hatch: a `client` machine temporarily serving itself locally (a `standalone` spawn) while the Canonical Server is unreachable. Explicit about its trade-off — fleet history returns on reconnect, and Sessions made during fallback merge back into the Canonical Server on rejoin. Never silent: an active Local fallback is a first-class, visible state.
+_Avoid_: offline mode, degraded mode
+
+**Rejoin**:
+The closing half of Local fallback: on reconnect, the client ships its local Session shard to the Canonical Server, which merges it as the single writer (id-guarded inserts, strictly-newer-wins per row, event-position guard, schema-drift column mapping). After Rejoin, fleet history is whole again — nothing strands on the client.
+_Avoid_: sync (bidirectional connotation), upload
+
+**Fleet token**:
+The shared secret authenticating a client to the Canonical Server's data routes — minted when the fleet server is enabled, stored at 0600, handed to clients during the ssh-based setup flow. The sibling of the per-boot server password (ADR 0002): that guards a spawned server its extension owns; this guards the service no extension spawns.
+_Avoid_: API key, password
+
+**Managed Tunnel**:
+The self-healing SSH local-forward a `client` uses to reach the Canonical Server — one component with two launchers. The extension spawns and supervises it for interactive panels (reconnect with backoff, address candidates probed LAN-before-overlay, health surfaced in the status bar); a headless launcher (`amico fleet tunnel`) serves panel-less consumers such as scheduled jobs. Failures are always visible to its consumer — never an invisible external service.
+_Avoid_: port forward (as a concept name), launchd tunnel
+
 ### Orthogonal axes
 
 **Entitlement**:
diff --git a/docs/adr/0005-managed-fleet.md b/docs/adr/0005-managed-fleet.md
new file mode 100644
index 0000000..a4fc2a1
--- /dev/null
+++ b/docs/adr/0005-managed-fleet.md
@@ -0,0 +1,68 @@
+# Managed Fleet: one canonical server, clients attach, nothing silently forks
+
+Status: draft (2026-08-07)
+
+A user's machines form one logical studio — one canonical chat server, many panels — but
+until now that topology lived entirely in ops duct tape: a hand-written ssh config, a
+hand-rolled launchd tunnel agent, and an extension whose only behavior was to spawn a local
+server, so the "client attaches through the tunnel" design worked *by accident* (the spawn
+lost a port race and the health probe rode the tunnel). On 2026-08-07 this failed three
+times in one day on one fleet: a silent three-week fork (279 sessions invisible to the
+canonical store), a fork reborn during a tunnel reconnect gap, and a panel stranded dead
+after a tunnel outage with no self-recovery. Each failure mode was detected by a human
+running diagnostics by hand; the product saw nothing.
+
+This ADR makes the fleet a product feature: explicit **Server mode** (`standalone` /
+`server` / `client`), the **Canonical Server** as a product-managed system service, the
+**Managed Tunnel** as a self-healing extension-owned component, an identity handshake and
+**Fleet token** on the server, and **Local fallback** with **Rejoin** merge as the
+user-facing repair hatch. Terms per `CONTEXT.md` (Fleet & serving).
+
+**Why:** the deciding requirement is not elegance but repairability for an open-source
+user: when the fleet breaks, the user must be able to keep working (Local fallback) and
+later rejoin without losing sessions — and the product must never, under any network
+condition, silently serve a forked store. Weighing the alternatives: Remote-SSH moves the
+user's whole editing context to the server (rejected as the primary pattern — "chat on the
+laptop about the laptop's files" breaks); ops-only hardening keeps the fragility (rejected
+— we spent a day chasing it); spawning on the server machine from its editor ties fleet
+liveness to an editor's lifetime (rejected — the couch scenario). The server-side merge and
+identity routes follow ADR 0002's seam precedent: the fork server owns what it owns, with
+CLI/headless parity.
+
+**Conditions of merge (the hardening grafts):** the never-fork invariant is enforced by
+construction (client/server modes contain no spawn path) and pinned by tests; machine-scoped
+settings (`scope: machine`) so Settings Sync can never carry `client` onto the server or leak
+the token into a synced file; the merge policy is locked by golden-shard fixtures recovered
+from the 2026-08-07 incident (id-guarded inserts, strictly-newer-wins per row with
+`directory` excluded, event `(aggregate_id, seq)` position guard, column-name mapping for
+schema drift, single FK-off transaction, refuse-and-preserve on unmappable drift); identity
+handshake verified before every attach (role + fleet id), mismatch refused with actionable
+copy; loopback-only binding with mutation routes refusing otherwise (ADR 0002 graft
+persists); the service binary lives at a stable path with the upgrade choreography
+(replace → restart → health probe) owned by the extension.
+
+**Flip condition:** revisit the Managed Tunnel + identity ownership if opencode upstream
+gains a native remote-attach capability with identity and auth (we would adopt rather than
+maintain ours); revisit the Rejoin merge toward park-local if cross-version schema drift
+produces merges we cannot verify — the invariant is "never lose, never silently corrupt",
+and a merge we cannot verify violates it.
+
+**Accepted costs:** the vendored fork's route surface grows again (identity + rejoin) —
+ADR 0002's highest-conflict-on-rebase spot gets busier; the rejoin merge is the most
+intricate component and its correctness budget is paid in fixtures and tests, not in review
+cleverness; the service installer is per-platform (launchd now, systemd when a Linux server
+appears); headless fleet consumers wait for the tunnel's second launcher.
+
+**Considered:** Remote-SSH pivot (zero fleet code, wrong workflow); ops-only hardening
+(zero build, keeps the fragility); two modes spawn/attach (server behaviors smear into
+spawn); a named Fleet object with membership (heavier than a studio needs); CLI-daemon
+tunnel (invisible failures); editor-owned canonical server (fleet dies with the editor);
+mDNS auto-discovery setup (LAN-only, extra surface — ssh bootstrap with manual fallback
+chosen); anonymous loopback auth (SSH as the boundary — rejected per ADR 0002's threat
+model; the fleet token is the per-boot password's sibling for a service no extension
+spawns).
+
+**Prior art / source:** the 2026-08-07 incident and recovery (fixtures at
+`~/.amico/fleet-recovery/2026-08-07/`); harmoniqs/amicode#279 (attach-only mode, filed from
+the incident); the fleet playbook in the Amico skill set; ADR 0001 (at-rest secret
+discipline), ADR 0002 (server-route seam, per-boot password, loopback graft).