Symptom

Scanning the WeChat QR code shown in the dashboard does not log in — the WeChat app shows a meaningless string of characters instead of a login confirmation.

Root cause

iLink's GET /ilink/bot/get_bot_qrcode returns two relevant fields:

• qrcode — an opaque status-poll key, passed to get_qrcode_status?qrcode=…. It is not scannable.
• qrcode_img_content — the payload the WeChat app actually decodes on scan (what makes WeChat recognise it as a login).

The pre-migration in-process Rust adapter surfaced qrcode_img_content as the QR payload — that was the explicit fix in #1560 / #1572 ("use iLink qr_url for WeChat QR code so WeChat can recognise the scan"). Its dashboard handler did:

let qrcode     = body["qrcode"].as_str()             // poll key
let qrcode_url = body["qrcode_img_content"].as_str() // scannable payload
json!({ "qr_code": qrcode, "qr_url": qrcode_url })   // front-end encodes qr_url

The WeChat → sidecar migration (#5421) dropped qrcode_img_content. _qr_login read only qrcode and encoded that opaque poll token into the QR, with a comment claiming "iLink does not surface a pre-formed deep-link URL." So the dashboard canvas encodes the poll key, WeChat can't recognise it as a login, and the user sees a plain string — re-introducing the exact bug #1572 had fixed.

Fix

sdk/python/librefang/sidecar/adapters/wechat.py::_qr_login:

• Read qrcode_img_content and emit it as the qr_ready payload (qr_code), which the dashboard encodes into the scannable canvas.
• Keep using the qrcode token for status polling (get_qrcode_status).
• If iLink ever omits qrcode_img_content, fall back to the token with a WARN (degraded — renders something rather than crashing) instead of silently shipping an unscannable QR.
• Corrected the module docstring + the inline comment that wrongly claimed the raw qrcode string is what operators scan.

Tests

• Updated test_qr_login_emits_ready_then_confirmed_without_token_on_wire to provide qrcode_img_content and assert the qr_ready payload is that value (not the token) — a regression guard tied to WeChat does not display QR codes #1560 / fix(dashboard): display WeChat QR code for iLink login #1572.
• Added test_qr_login_qr_payload_falls_back_to_token_when_img_content_absent covering the degraded path (token fallback + WARN).
• Full sdk/python suite: 1874 passed (local venv, pytest).

Scope

Python sidecar only; independent of the other open channel PRs (#6085 describe-probe, #6083 goal-runner). No Rust changes.