# Roadmap — Closed-Loop eSIM Provisioning ("SIM Drop")

_Last updated: 2026-07-02_

## Context

**Goal.** A "SIM drop": a WiFi access point dropped into the field, pre-loaded
with a batch of eSIM profiles already registered in the 5G core, that hands
credentials to devices through a captive portal reached by QR code. If a backhaul
link to the core exists, it can also register new subscribers dynamically.

**End devices.**
- **COTS UEs** (handsets / modems) with real eUICCs.
- An in-house **software UE stack** that can load credentials from a file.

**Constraints & resources.**
- **Purely eSIM** — no physical SIM programming (Open-Cells cards on hand are not
  the target path).
- Available for testing: **srsRAN gNB + Open5GS running**, a **test eUICC / phone**.
- Deployment targets **Pi and Android**, equally.

## The hard constraint that shapes everything

Consumer eSIM (GSMA SGP.22 RSP) does **not** let you sideload a profile file into
an eUICC. The device's LPA downloads the profile from an **SM-DP+** identified by
an activation code, and **the eUICC will only trust an SM-DP+ whose certificate
chains to the GSMA CI root**.

A field-local SM-DP+ (e.g. Osmocom `osmo-smdpp`) uses **test CI keys**, which only
**test eUICCs** accept. Therefore:

- ✅ **Software UE** — loads a profile/credential file directly. Works today, no RSP.
- ✅ **Test eUICCs** (dev eUICC cards / test modems) — can install from a local
  `osmo-smdpp`. This is the realistic "real eSIM" demo path.
- ❌ **Arbitrary consumer phones with factory eUICCs** — will reject a local
  SM-DP+. Not achievable in an ad-hoc/offline deployment without a GSMA-accredited
  SM-DP+ (out of scope for emergency/NTN).

**Implication:** target the **software UE** and **test-eUICC modems**. Treat
generic consumer-phone eSIM as explicitly out of scope until/unless a real
SM-DP+ relationship exists.

## Where we are (done)

Provisioning server: credential generation (IMSI/Ki/OPc/ICCID), SQLite store,
per-MAC rate limiting, captive portal, Open5GS/free5gc adapters, `v2` + real
`SAIP` profile generation, security-hardened, 109 tests. **Missing: the last mile
(delivery to a device) and live core-integration proof.**

## Target architecture

```
Drop device (Pi / Android)
├─ WiFi AP (open) + captive portal (QR entry)
├─ Provisioning server (Flask)      ← built
├─ Subscriber DB (pre-registered batch + dynamic)  ← built, needs batch layer
├─ Local SM-DP+ (osmo-smdpp)        ← Phase 3
└─ Backhaul to core (optional)      ← dynamic registration when present

Two delivery tracks:
  Track S — Software UE:  profile file → soft-UE → attach          (Phase 1)
  Track E — Test eUICC:   QR activation code → LPA → local SM-DP+
                          → eUICC installs SAIP profile → attach   (Phase 3)
```

## Phases

### Phase 0 — Prove core attach (de-risk the foundation)
Register one generated credential in Open5GS and attach with the software UE (or
a test eUICC) on srsRAN+Open5GS; confirm authentication succeeds.
- Validates our Milenage/OPc derivation and the adapter document shape against a
  **live** core — everything downstream depends on this being correct.
- **Needs from you:** Open5GS reachability (MongoDB URI / network) or you run the
  sync; the slice (SST/SD), APN/DNN, and PLMN the gNB expects.

### Phase 1 — Software-UE loop (file delivery; first closed loop, no SM-DP+)
- Define the soft-UE profile format and add an exporter (extend
  `scripts/make_profile.py` / a new `/api/provision` format).
- Flow: WiFi → captive portal → provision → download soft-UE profile → attach.
- **Needs from you:** the exact format your soft-UE ingests (e.g. srsUE-style
  `ue.conf` with `imsi/k/opc/opc_type`, or a custom schema).

### Phase 2 — Pre-registered batch + drop packaging (the "drop" model) [software-only; can start now]
- Batch generator: pre-generate _N_ profiles, register all in the core, persist to
  the drop DB marked "available".
- Captive-portal **claim** flow: atomically hand an unclaimed pre-registered
  profile to a device (QR/portal).
- **Offline operation:** with no backhaul, hand out from the pre-loaded batch;
  queue dynamic registrations for when the core link returns.
- Deliverable: a drop that works fully offline from a pre-loaded batch.

### Phase 3 — Test-eUICC via local SM-DP+ (the real eSIM last mile)
- Stand up `osmo-smdpp` on the drop; wire our SAIP profiles into it; manage the
  (test) CI cert chain.
- Complete the SAIP profile to an installable one (PIN/PUK, ARR, security domain,
  remaining mandatory PEs) — **validated against the test eUICC** (this is where
  the deferred SAIP PE work finally gets card-validated rather than guessed).
- Captive portal renders the LPA activation-code **QR**; test device installs and
  attaches.
- Deliverable: test-eUICC device → scan QR → eSIM installed → on the network.

### Phase 4 — Field hardening (Pi + Android, first-class)
Offline/power/thermal, monitoring/observability, capacity, subscriber
revoke/expire/resync, backhaul-aware dynamic registration, secure batch loading.

## Recommended immediate next steps

1. **Phase 0** — prove live attach (software UE + Open5GS). Highest de-risking value.
2. **Phase 2 groundwork (in parallel, software-only, no hardware needed):** the
   batch pre-registration generator + atomic claim flow. This is squarely on the
   critical path for the "dropped, pre-loaded, offline" model and I can build and
   test it now.

## Open questions

- **Soft-UE profile format** — what schema does your software UE ingest?
- **Open5GS access** — reachable from the dev environment, or do you run sync?
  MongoDB URI, slice SST/SD, APN/DNN, PLMN to match the gNB.
- **SM-DP+** — OK to vendor/run `osmo-smdpp` on the drop, or a different RSP?
- **Test eUICCs** — which test eUICC(s)/modems are the real targets (so Phase 3
  profile completion is validated against them)?
- **Batch model** — expected batch size per drop; how batches are provisioned and
  loaded (offline media vs one-time backhaul).