feat(wifi): the SSID rewriter stands down when a project defines its own airspace

A private overlay can install window.__velxio_custom_wifi_ssids__ — a
nullary provider naming the WiFi networks the project's access-point
parts broadcast. Three consumers, one seam:

- the compile payload gains custom_wifi_ssids; when non-empty the
  ESP-IDF compiler skips SSID normalization entirely (no literal
  rewrite, no channel forcing) — the sketch connects to the network
  the user actually wrote, and a typo now fails truthfully. The dedup
  key hashes the list so with/without-APs builds never alias.
- the MicroPython network shim redirects unknown SSIDs to the FIRST
  project network instead of the hardcoded Velxio-GUEST, and its tuple
  gains the trailing comma that made a one-network list a string.
- the firmware-upload note lists the project's networks and says "add
  an access point part with this SSID" instead of "rebuild".

No provider installed (OSS build) = exactly the old behavior; the
issue-270 suite stays green (12/12).

backend/app/api/routes/compile.py

@@ -198,6 +198,7 @@ def _job_key(
     libraries: list[str] | None = None,
     owner_id: str | None = None,
     language: str | None = None,
+    custom_wifi_ssids: list[str] | None = None,
 ) -> str:
     """Stable content hash of (files, board, options, spiffs, libraries, owner)
     used as the deduplication key.
@@ -232,6 +233,15 @@ def _job_key(
         import json
         h.update(json.dumps(board_options, sort_keys=True).encode())
         h.update(b"\0")
+    if custom_wifi_ssids:
+        # Custom APs suppress the SSID rewrite, so the same source builds
+        # DIFFERENT bytes with vs without them — the key must see it. Only
+        # presence matters for the rewrite, but hash the sorted list so a
+        # rename also invalidates cleanly.
+        for ssid in sorted(custom_wifi_ssids):
+            h.update(ssid.encode())
+            h.update(b"\0")
+        h.update(b"\0custom-aps\0")
     if spiffs_files:
         for f in sorted(spiffs_files, key=lambda x: x["name"]):
             h.update(f["name"].encode())
@@ -315,6 +325,12 @@ class CompileRequest(BaseModel):
     # backend deploy — espidf_compiler.compile validates known keys and
     # ignores the rest. None / missing on non-ESP32 boards.
     board_options: dict[str, str | int | bool] | None = None
+    # Optional: the SSIDs of the project's custom WiFi access points (the
+    # velxio-wifi-ap parts on the canvas, overlay feature). When non-empty
+    # the compiler does NOT rewrite the sketch's SSID literals — the project
+    # defines its own airspace, so what the user typed is what exists. Empty
+    # / missing keeps the legacy behavior (rewrite to the built-in networks).
+    custom_wifi_ssids: list[str] | None = None
     # User-uploaded files to bake into the SPIFFS partition (#162). Empty /
     # None means the SPIFFS region stays blank (current behaviour).
     spiffs_files: list[SpiffsFileBody] | None = None
@@ -495,6 +511,7 @@ async def _run_compile(
             allowed_libraries=allowed_libraries,
             owner_id=owner_id,
             pure_idf=pure_idf,
+            custom_wifi_ssids=request.custom_wifi_ssids,
         )
         return CompileResponse(
             success=result["success"],
@@ -821,6 +838,7 @@ async def compile_start(
         sorted(allowed_libraries) if allowed_libraries else None,
         owner_id if allowed_libraries else None,
         language=request.language,
+        custom_wifi_ssids=request.custom_wifi_ssids,
     )
     existing_id = JOB_BY_KEY.get(key)
     if existing_id is not None:

backend/app/services/espidf_compiler.py

@@ -3569,10 +3569,16 @@ class ESPIDFCompiler:
         allowed_libraries: set[str] | None = None,
         owner_id: str | None = None,
         pure_idf: bool = False,
+        custom_wifi_ssids: list[str] | None = None,
     ) -> dict:
         """
         Compile Arduino sketch using ESP-IDF.
 
+        `custom_wifi_ssids` non-empty = the project carries its own access
+        point parts: the WiFi normalization below stands down entirely (no
+        SSID rewrite, no channel forcing) — the user's airspace is exactly
+        what they typed, typos included, which is now the truthful outcome.
+
         Returns dict compatible with ArduinoCLIService.compile():
             success, binary_content (base64), binary_type, stdout, stderr, error
 
@@ -3967,6 +3973,7 @@ class ESPIDFCompiler:
             # Normalization still rewrites only the entry sketch: it edits
             # string literals in place, and the SSID that matters is the one
             # WiFi.begin() is called with.
+            if not custom_wifi_ssids:
                 main_content = self._normalize_wifi_for_qemu(main_content)
 
         # Arduino-as-component only when compile() decided so: the core must
@@ -3996,6 +4003,7 @@ class ESPIDFCompiler:
                     continue
                 content = f.get('content', '')
                 if has_wifi:
+                    if not custom_wifi_ssids:
                         content = self._normalize_wifi_for_qemu_idf(content)
                 (main_dir / name).write_text(content, encoding='utf-8')
                 wrote_any = True

frontend/src/services/compilation.ts

@@ -131,6 +131,13 @@ export async function compileCode(
     : null;
   // P2.3 — library manifest (resolution scope). null = legacy scan-all.
   const libraries = extras?.libraries && extras.libraries.length ? extras.libraries : null;
+  // Custom WiFi access points (overlay feature): when the project carries its
+  // own AP parts, their SSIDs ride along and the backend's SSID rewriter
+  // stands down — the sketch connects to the network the user actually wrote.
+  // OSS builds have no provider installed → null → legacy rewrite.
+  const customWifiSsids =
+    (window as { __velxio_custom_wifi_ssids__?: () => string[] | null })
+      .__velxio_custom_wifi_ssids__?.() ?? null;
 
   let jobId: string;
   try {
@@ -147,6 +154,7 @@ export async function compileCode(
         libraries,
         language: extras?.language ?? null,
         initiated_by: extras?.initiatedBy ?? null,
+        custom_wifi_ssids: customWifiSsids,
       },
       { withCredentials: true, timeout: 30000 },
     );

frontend/src/store/useSimulatorStore.ts

@@ -2131,17 +2131,25 @@ export const useSimulatorStore = create<SimulatorState>((set, get) => {
           // reviving the fake stub for them. Known SSIDs pass through
           // untouched, and the rewrite is announced on serial so nobody
           // debugs a connection they didn't make.
+          // Custom AP parts (overlay-provided window seam) replace the
+          // network list the shim knows about — and the redirect target
+          // becomes the FIRST project network instead of Velxio-GUEST.
+          // Without the provider (OSS build) the classic four stand.
+          const customSsids =
+            (window as { __velxio_custom_wifi_ssids__?: () => string[] | null })
+              .__velxio_custom_wifi_ssids__?.() ?? null;
+          const shimSsids: readonly string[] = customSsids ?? EMULATED_WIFI_SSIDS;
           const networkStub = wifiOn ? [
             'import network as _vlx_net',
             'import time as _vlx_time',
-            `_VLX_SSIDS = (${EMULATED_WIFI_SSIDS.map((s) => JSON.stringify(s)).join(', ')})`,
+            `_VLX_SSIDS = (${shimSsids.map((s) => JSON.stringify(s)).join(', ')},)`,
             'class _VlxWLAN:',
             '    def __init__(self, *a, **k):',
             '        self._w = _vlx_net.WLAN(*a, **k)',
             '    def connect(self, ssid=None, key=None, **kw):',
             '        if ssid is not None and ssid not in _VLX_SSIDS:',
-            '            print("[velxio] SSID %r is not part of the emulated network; connecting to \'Velxio-GUEST\' instead" % ssid)',
-            '            ssid, key = "Velxio-GUEST", ""',
+            `            print("[velxio] SSID %r is not part of the emulated network; connecting to ${JSON.stringify(shimSsids[0]).replace(/"/g, "'")} instead" % ssid)`,
+            `            ssid, key = ${JSON.stringify(shimSsids[0])}, ""`,
             '        if ssid is None:',
             '            return self._w.connect()',
             '        return self._w.connect(ssid, key, **kw)',

frontend/src/utils/firmwareWifiNote.ts

@@ -52,11 +52,26 @@ export async function wifiSsidNoteFor(file: File): Promise<string | null> {
     return null; // unreadable is the caller's problem, not ours to report twice
   }
   if (!WIFI_MARKERS.some((m) => containsAscii(bytes, m))) return null;
-  if (EMULATED_WIFI_SSIDS.some((s) => containsAscii(bytes, s))) return null;
+  // A project with its own AP parts (overlay window seam) defines the
+  // airspace; without them the classic four stand. Either way, firmware
+  // that names one of the on-air networks needs no note.
+  const custom =
+    (window as { __velxio_custom_wifi_ssids__?: () => string[] | null })
+      .__velxio_custom_wifi_ssids__?.() ?? null;
+  const onAir: readonly string[] = custom ?? EMULATED_WIFI_SSIDS;
+  if (onAir.some((s) => containsAscii(bytes, s))) return null;
+  if (custom) {
+    return (
+      'This firmware uses WiFi but does not name any network in this project. ' +
+      `The project's access points broadcast: ${custom.join(', ')}. ` +
+      'Add a WiFi Access Point part with the SSID the firmware expects and it will connect.'
+    );
+  }
   return (
     'This firmware uses WiFi but does not name any network the emulator has. ' +
     `The emulated radio broadcasts only: ${EMULATED_WIFI_SSIDS.join(', ')} — all open, ` +
-    'no password. Rebuild it with one of those as the SSID and it will connect. ' +
+    'no password. Rebuild it with one of those as the SSID — or add a WiFi Access ' +
+    'Point part with your SSID (paid feature) — and it will connect. ' +
     '(Sketches compiled here are rewritten automatically; an uploaded binary cannot be.)'
   );
 }