Document Android PlatformType mapping to Chrome

api/bot.mdx

@@ -406,7 +406,7 @@ Pair code runs concurrently with QR code pairing — whichever completes first w
 </Note>
 
 <Tip>
-The `companion_platform_display` shown on the phone is derived automatically from the resolved `platform_id` and the device's `os` string: web variants emit `<Browser> (<OS>)`; Android variants emit `Android (<OS>)`. There is no separate `platform_display` field on `PairCodeOptions`.
+The `companion_platform_display` shown on the phone is derived automatically from the resolved `platform_id` and the device's `os` string: web variants emit `<Browser> (<OS>)` (Android `PlatformType`s map to `Chrome`, so they show as `Chrome (Android)` by default); explicit `AndroidPhone`/`AndroidTablet`/`AndroidAmbiguous` overrides emit `Android (<OS>)`. There is no separate `platform_display` field on `PairCodeOptions`.
 </Tip>
 
 ---

api/client.mdx

@@ -244,7 +244,7 @@ This can run concurrently with QR code pairing — whichever completes first win
   - `phone_number` — Phone number in international format (e.g., `"15551234567"`)
   - `show_push_notification` — Whether to show a push notification on the phone (default: `true`)
   - `custom_code` — Optional custom 8-character code using Crockford Base32 alphabet
-  - `platform_id` — `Option<CompanionWebClientType>` override for `<companion_platform_id>`. `None` derives the wire id from `Device.device_props.platform_type` (typically `Chrome`). The matching `<companion_platform_display>` is always derived; web variants emit `<Browser> (<OS>)` and Android variants emit `Android (<OS>)`.
+  - `platform_id` — `Option<CompanionWebClientType>` override for `<companion_platform_id>`. `None` derives the wire id from `Device.device_props.platform_type` (typically `Chrome`; Android `PlatformType`s also map to `Chrome` because the server requires attestation for the Android letter codes). The matching `<companion_platform_display>` is always derived; web variants emit `<Browser> (<OS>)`, and explicit `AndroidPhone`/`AndroidTablet`/`AndroidAmbiguous` overrides emit `Android (<OS>)`.
 </ParamField>
 
 <ResponseField name="code" type="String">

concepts/authentication.mdx

@@ -248,35 +248,36 @@ pub struct PairCodeOptions {
 // wacore/src/companion_reg.rs
 pub enum CompanionWebClientType {
     // Web (digit codes from WAWebCompanionRegClientUtils.DEVICE_PLATFORM)
-    Unknown,           // b'0'
-    Chrome,            // b'1' — default
+    Chrome,            // b'1'
     Edge,              // b'2'
     Firefox,           // b'3'
     Ie,                // b'4'
     Opera,             // b'5'
     Safari,            // b'6'
     Electron,          // b'7'
     Uwp,               // b'8'
-    OtherWebClient,    // b'9'
-    // Mobile (letter codes from the official WhatsApp Android client)
+    OtherWebClient,    // b'9' — default fallback
+    // Mobile (letter codes from the official WhatsApp Android client).
+    // Reachable only via an explicit `PairCodeOptions::platform_id` override
+    // because the server requires attestation that this crate cannot fake.
     AndroidTablet,     // b'd'
     AndroidPhone,      // b'e'
     AndroidAmbiguous,  // b'f'
 }
 ```
 
-The server accepts 23 single-byte ids (`0..9` and `a..m`); only the 13 with a confirmed platform meaning are exposed. Variants without a confirmed letter fall back to `OtherWebClient` (`'9'`).
+The proto's `UNKNOWN` (wire `'0'`) is intentionally absent — WA Web never emits it from a real browser and the server rejects it. The default is `OtherWebClient` (`'9'`). The server accepts 23 single-byte ids (`0..9` and `a..m`); only the 12 with a confirmed platform meaning are exposed.
 
 #### Mapping from `PlatformType`
 
-`companion_web_client_type_for_platform` maps each `wa::device_props::PlatformType` to a wire variant. Web platforms map to their browser variant (Chrome, Firefox, Edge, etc.). Android platforms map to the dedicated Android letters. Other mobile and embedded platforms collapse to `OtherWebClient`.
+`companion_web_client_type_for_platform` maps each `wa::device_props::PlatformType` to a wire variant. Web platforms map to their browser variant (Chrome, Firefox, Edge, etc.). `Desktop` maps to `Electron`. The Android `PlatformType` variants (`AndroidPhone`, `AndroidTablet`, `AndroidAmbiguous`) map to **`Chrome`** — that's what real WA Web on Chrome-Android emits and what the server accepts without attestation. To request the Android letter codes (`'d'`/`'e'`/`'f'`) explicitly, set `PairCodeOptions::platform_id`. iOS, AR/VR, Wear OS, and the proto's `UNKNOWN` collapse to `OtherWebClient`.
 
 #### `companion_platform_display`
 
-The display string sent in `<companion_platform_display>` is built from the wire variant and the OS reported in `DeviceProps`:
+The display string sent in `<companion_platform_display>` is built from the resolved wire variant and the OS reported in `DeviceProps`:
 
-- Web variants emit `<Browser> (<OS>)`, e.g. `Chrome (Linux)`, `Firefox (Windows)`.
-- Android variants emit `Android (<OS>)`, e.g. `Android (Android)`.
+- Web variants emit `<Browser> (<OS>)`, e.g. `Chrome (Linux)`, `Firefox (Windows)`. Non-browser web variants (Electron, UWP, OtherWebClient) and Android-mapped-to-Chrome fall back to `Chrome (<OS>)`, mirroring WA Web's reported renderer name.
+- Explicit `AndroidPhone`/`AndroidTablet`/`AndroidAmbiguous` overrides emit `Android (<OS>)`, e.g. `Android (Android)`.
 - Empty OS substitutes `Linux`.
 
 The server only validates that the display string is 1..=100 bytes — there is no browser whitelist.