# Vendor Daemon & gRPC API — Status, Known Issues, and Plan to Fab-Readiness

> **This is a forward-looking roadmap, not a description of shipped behaviour.**
> Every item carries a status marker. Do not read an item as "done" unless it
> says ✅. (Last full audit: 2026-06-10.)
>
> Status legend: ✅ done · 🚧 in progress · ⬜ planned · ⚠️ risk/unknown

## What this is

A vendor-facing **daemon** (`secs_gemd`) that runs the SECS/GEM engine as its
own process and exposes a small, name-based, language-agnostic API over gRPC,
so a tool's control software (in any language) can drive the equipment without
linking C++ or knowing SEMI. See `proto/secsgem/v1/equipment.proto`.

The point of the daemon model: it owns the durable HSMS relationship with the
host and stays conformant while the tool software restarts/upgrades/crashes.

## Current status (2026-06-10, end of day)

| Piece | Status | Notes |
|---|---|---|
| `proto/secsgem/v1/equipment.proto` | ✅ | v1 surface designed: universal + carrier/recipe/job tiers, `Subscribe` stream, health |
| `HostCommandRegistry::set_handler` behaviour hook | ✅ | the engine seam for command behaviour; tested |
| `EquipmentRuntime` (engine owner) | ✅ | tested (`test_runtime.cpp`); `secs_server` runs entirely on it (live GEM300 demo passes) |
| `register_default_handlers` (the 56 GEM handlers as a library fn) | ✅ | `src/gem/default_handlers.cpp`; tested (`test_default_handlers.cpp`) |
| gRPC/protobuf toolchain (Dockerfile + CMake codegen) | ✅ | grpc++ 1.51 / protoc 3.21; opt-in `SECSGEM_DAEMON`, graceful skip without grpc |
| `secs_gemd`: `SetVariables` / `FireEvent` / `GetControlState` / `GetVariables` | ✅ | **format-aware** both directions (declared SECS-II formats on write, `from_item` on read) and thread-safe (snapshot maps + posted writes + `read_sync` reads). In-process gRPC tests incl. run_async production mode (`test_daemon_service.cpp`, 61 assertions) |
| Daemon interop vs **secsgem-py** reference host | ✅ | `interop/daemon_interop.py` (via `gemd` compose service): gRPC `SetVariables(ChamberPressure=2.5)` + `FireEvent` → host receives `S6F11 CEID 300` carrying `<F4 2.5>` — value *and declared format* flow gRPC→engine→HSMS→host |
| Daemon interop vs **secs4j** (Java) | ⬜ | mirror the secsgem-py harness against `interop/secs4j` |
| `Subscribe` host→tool command stream + `CompleteCommand` | ✅ | HCACK-4 contract implemented + tested in-process AND live vs secsgem-py (full loop: S2F41 → stream → complete → S6F11) |
| Universal RPC surface complete (vars/events/alarms/control-state/health) | ✅ | Phase A done; daemon tests 101 assertions, interop 15 checks |
| Python client package (the "beautiful API") | ⬜ | thin wrapper over generated stubs |

## Known issues (found in the 2026-06-10 audit; honest list)

- ✅ ~~**`GetControlState` cross-thread read.**~~ Fixed 2026-06-10: the runtime
  keeps an atomic control-state mirror updated via an `add_state_change_handler`
  observer (`HandlerSlot` primary+observers pattern), so the mirror survives
  `register_default_handlers` claiming the primary slot. `control_state()` is
  now safe from any thread.
- ✅ ~~**Alarms have no name key.**~~ Optional `name:` added to the alarm
  config (loader + validator + shipped equipment.yaml); daemon RPCs accept
  the name or the stringified ALID.
- ⬜ **`pvd_tool` predates the behaviour hook.** It still hard-codes
  `if (rcmd=="START") recipe->start(...)` in a router handler. Migrate it to
  `commands.set_handler` so the flagship example showcases the intended seam.
- ✅ ~~**Interop harnesses are manual.**~~ `tools/run_interop.sh` runs all nine
  validation steps with one command (verified green); CI lanes added, pending
  first-push verification (Phase 0 item 2).
- ✅ ~~**TSan lane doesn't cover the daemon.**~~ Covered locally + in CI
  with `tools/tsan.supp` (third-party-only suppressions). Caught + fixed a
  real test-side contract violation on its first run.
- ⚠️ **macOS bind-mount staleness can break Docker builds mid-edit** (a build
  reading a half-synced source file). Not a product bug; re-run the build.

## The `Subscribe` design (settled — implement to this)

`S2F42` is an *acknowledgement*, not a completion: SEMI separates "I accept
your command" from "the work finished". The conformant, non-blocking flow:

1. Host sends `S2F41 START`. The engine's `on_command` handler (registered by
   the daemon) runs on the io thread.
2. If no tool client is subscribed → fall back to the YAML declarative ack.
   If a tool is subscribed → push the command onto its `Subscribe` stream and
   **return `HCACK=4` (AcceptedWillFinishLater) immediately** — never block
   the io thread or the T3 window on the tool.
3. The tool does the work and reports the outcome via `FireEvent` (success
   event) / `SetAlarm` (failure) — exactly how secsgem-py applications and
   commercial gateways do it.
4. `CompleteCommand` therefore only correlates/audits the command lifecycle in
   v1. A *synchronous gating* mode (tool decides HCACK 0/2 before the S2F42
   goes out) requires a deferred-reply mechanism in the engine — explicitly a
   v2 refinement, not needed for conformance.

Sub-decisions (settled 2026-06-10, implemented + tested):
- v1 is a firehose: every subscriber receives every host request.
- NO buffering: with no subscriber a command takes its declarative YAML ack
  and is not replayed on reconnect — never "will finish later" for work no
  tool will do. Documented in the proto's Subscribe contract.

## Plan — ordered next steps

### Phase 0 — structural debts (from the 2026-06-10 design review; pay before sprinting)
The review's verdict: architecture and API bets are sound, but two structural
debts tax every later phase, and the most valuable tests aren't automated.

1. 🚧 **Multi-observer callbacks** (THE structural blocker — hit twice already).
   `HandlerSlot` (primary slot keeps legacy set_ semantics; append-only add_
   observers survive it) — done for `ControlStateMachine` + PJ/CJ stores, plus
   runtime atomic control-state mirror (race retired) and `add_link_observer`
   (WatchHealth foundation). ⬜ Remaining: roll the same 3-line pattern onto the
   other single-slot classes (comm-state, EPT, exceptions, substrates, modules,
   carriers, E84) as each phase needs them — mechanical now that the type exists.
2. 🚧 **CI the interop + conformance harnesses.** `tools/run_interop.sh` ✅ —
   one command runs ALL nine validation steps (build, unit, daemon-unit,
   py-host 31 checks, conformance 47, daemon bridge, spool restart, tshark,
   secs4j 55) with a PASS/FAIL summary; verified green end-to-end 2026-06-10.
   CI ✅ added but UNVERIFIED until pushed: grpc deps + `secs_gemd_tests` in
   the build job (fails loudly if the daemon silently drops out), and a new
   `python-interop` lane (py-host + conformance + daemon harness against
   localhost, no docker-in-docker). ⬜ Verify the lanes on the first push.
3. ✅ **Fix `CompleteCommand` proto comment** — it described the rejected
   blocking model; now states the HCACK-4 contract.
4. ✅ **Table-driven handler conformance test** — one ordered scenario
   drives 53 of the 56 handlers through `router.dispatch` (236 assertions).
   Golden frames: S1F13, S5F1, and a composed S6F11, all hand-computed from
   E5 rules (external pins, not codec-derived).
5. ⬜ **Decompose `register_default_handlers` per GEM capability** (it is a
   relocated main(), not a designed component) and replace magic constants
   (SVIDs 1/2 `refresh()`, CEIDs 400/401) with YAML role bindings
   (`control_state_svid:`, `cj_executing_ceid:` …). Gradual; aligns with the
   capability structure GEM itself defines (S1F19) and enables vendor subsetting.
6. ✅ **Standardize the mutable-read pattern** — `EquipmentRuntime::read_sync`
   (post-to-io + future with deadline; nullopt => UNAVAILABLE at the RPC edge).
   Precedent set by `GetVariables`; every future mutable read copies it.
7. ✅ `equipment_service.hpp` moved to `include/secsgem/daemon/` (apps/
   include-path hack removed). TSan daemon lane added locally + in CI
   (`tools/tsan.supp` suppresses UNinstrumented system libgrpc/libabsl
   internals only — our frames stay checked). The lane caught a real
   contract violation on its first run (a test reading the model from the
   test thread under run_async — fixed to read_sync); now TSan-clean with
   halt_on_error=1.
8. ✅ Identifier-safe name validation: `ConfigValidator` warns (not errors)
   on non-identifier variable/event/alarm/command names — bindings expose
   names as kwargs/attributes. Format-compliance property test ✅; unset-
   `Value` guard ✅.

### Phase A — finish the universal daemon surface (small, unblock vendors)
1. ✅ `GetVariables` — `from_item` reverse conversion (scalar for 1-element
   arrays, List otherwise; C2-as-text and U8>2^63 noted as TODOs) + reads via
   `read_sync`. Tested under **run_async (production threading)** — write
   through the API, read back through the API — plus empty-query-returns-all,
   INVALID_ARGUMENT on unknown names, and a live round-trip check in
   `daemon_interop.py`.
2. ✅ Alarm `name:` config field (optional local key; `name` appended LAST on
   the Alarm struct so existing brace-inits compile unchanged) + `SetAlarm`/
   `ClearAlarm` RPCs (addressable by config name AND stringified ALID).
   Validated end-to-end: gRPC `SetAlarm(chiller_temp_high)` -> secsgem-py host
   receives `S5F1 ALCD=0x84 ALID=1`.
3. ✅ `RequestControlState` — fires operator events on the io thread and
   reports what the E30 table actually did (ACCEPT iff landed in the requested
   state; the shipped table has NO operator path to EquipmentOffline and the
   test pins that honesty). ✅ `WatchHealth` — initial snapshot + push on
   link/control-state change (+ spool depth sampled at 500ms); unit-tested
   incl. the change push; link state still SELECTED/DISCONNECTED only
   (CONNECTED reserved, TODO in code). Interop covers RequestControlState;
   WatchHealth external check rides with Phase B.
4. ✅ Done per-item above (daemon suite at 101 assertions; interop at 15 checks).

### Phase B — the command stream (the big one)
5. ✅ `Subscribe`/`CompleteCommand` implemented per the HCACK-4 design.
   Reconnect decision settled and documented in the proto: **no buffering** —
   a command with no subscriber takes its declarative YAML ack (the honest
   pre-daemon behaviour) and is not replayed. Firehose fan-out; per-command
   forwarding handlers registered from the registry (new `names()`/`spec()`
   accessors); pending-id audit map. In-process tests drive a REAL S2F41
   through the default-handler router on the io thread: HCACK 4 with a
   subscriber (params arrive on the stream), declarative Accept without,
   CompleteCommand known/unknown ids, fallback restored after unsubscribe.
6. ✅ The full conformant loop runs against secsgem-py live: host `S2F41
   START` → `S2F42 HCACK=4` → tool receives Command(name=START, id) on the
   stream → `CompleteCommand` → tool fires the event → host receives `S6F11`.
   (interop now 20 checks.)
7. ⬜ Java interop: `secs4j` host variant of the same scenario.

### Phase C — the beautiful Python client
8. ⬜ `clients/python/` package (`pip install secsgem-client`): wraps generated
   stubs in the agreed API — `eq.set(chamber_pressure=2.5)`, `eq.fire("wafer_complete", thickness=1.2)`,
   `eq.alarm("pressure_high")`, `@eq.on("START")` consuming the stream,
   `eq.health()`. Pure Python (no compiled ext). Ship stubs pre-generated.
9. ⬜ Example: rewrite a minimal `pvd_tool`-equivalent in ~40 lines of Python
   against the daemon; also migrate the C++ `pvd_tool` to `set_handler`.

### Phase D — GEM300 in-the-loop (process/carrier tools)
10. ⬜ Settle job/carrier semantics (who acks S16F5/S3F17, gate vs observe —
    see proto comments), then wire `ProcessJob`/`CarrierAction` onto the
    stream + `ReportProcessJob`/`ReportCarrier` into the PJ/CJ/carrier stores.
11. ⬜ Recipe download (`ProcessProgram` on the stream when S7F3 lands) and
    EC-change notification (`ConstantChange` when S2F15 lands).
12. ⬜ Interop scenarios for jobs/carriers vs secsgem-py + secs4j.

### Phase E — hardening & operations
13. ⬜ gRPC exposure: default to localhost + document UDS; optional TLS creds.
14. ⬜ `tools/run_interop.sh` + CI lanes: all interop harnesses + TSan daemon lane.
15. ⬜ Daemon Prometheus metrics + supervised deployment recipe (systemd unit).
16. ⬜ Remaining Layer-1 API: traces, limits, substrates/modules, terminal
    services, spool depth/flush, `Describe` RPC.

### Phase F — fab acceptance (parallel track; the hard gate)
- ⚠️ **Standards correctness remains unverified against SEMI texts** (behaviour
  reconstructed without the standards; interop with secsgem-py/secs4j/Wireshark
  mitigates but does not prove). The #1 fab-readiness risk; needs real
  standards access and/or a fab's MES qualification run (`docs/MES_INTEROP.md`).
- ⬜ GEM compliance statement + manual matching the tool's data dictionary.
- ⬜ SECS-I serial driver (asio `serial_port` adapter; FSM done) — only if a
  target tool uses RS-232.