Fix beta desktop download selection

[kodjima33]

Summary

• make /v2/desktop/download/latest?channel=beta always return the newest desktop GitHub DMG
• stop beta download selection from depending on stale release-channel metadata
• add unit coverage for latest-release beta redirects

Testing

• pytest backend/tests/unit/test_desktop_updates.py # fails locally: missing httpx dependency in this environment

[greptile-apps]

Greptile Summary

This PR fixes the beta desktop download endpoint (/v2/desktop/download/latest?channel=beta) to always return the newest live GitHub release with a DMG asset, regardless of how that release's channel metadata is tagged. Previously, the endpoint only matched releases explicitly marked channel=beta in their release body, which could surface a stale build if the most-recent release was promoted to channel=stable. The stable path and the Sparkle appcast endpoint are unchanged.

Changes:

• backend/routers/updates.py: Adds a dedicated channel == "beta" early-return path in download_latest_desktop_release that iterates all live releases (sorted newest-first by published_at) and redirects to the first DMG found, bypassing channel-tag filtering.
• backend/tests/unit/test_desktop_updates.py: Updates test_beta_no_fallback (was expecting 404, now expects 302) to match the new behaviour and adds test_beta_uses_latest_release_even_if_marked_stable to explicitly verify the cross-channel resolution.

Issues found:

• test_beta_no_fallback was updated to assert the opposite behaviour from its original purpose, but its name was not changed. The name now actively misleads readers about what the test proves.
• test_beta_no_fallback is the only redirect test in TestDownloadEndpoint that omits follow_redirects=False from AsyncClient, creating an inconsistency with every sibling redirect test.

Confidence Score: 4/5

• Production logic is correct and safe to merge; minor test quality issues remain.
• The production code change is small (10 lines), clearly intentional, and correctly implements the stated goal. The logic is covered by two new/updated test cases. The only issues are in the test file: a now-misleading test name and a missing follow_redirects=False flag on one test. Neither affects correctness in the current httpx 0.28 environment, but the misnamed test is a readability/maintenance hazard.
• backend/tests/unit/test_desktop_updates.py — test_beta_no_fallback test name and missing follow_redirects=False

Important Files Changed

Filename	Overview
backend/routers/updates.py	Adds a fast-path for channel=beta in download_latest_desktop_release that returns the first live release with a DMG regardless of its channel metadata; stable path unchanged.
backend/tests/unit/test_desktop_updates.py	Updates test_beta_no_fallback to expect 302 (was 404) and adds test_beta_uses_latest_release_even_if_marked_stable; the renamed test assertion contradicts its original name and is the only redirect test missing follow_redirects=False.

Sequence Diagram

sequenceDiagram
    participant Client
    participant Router as download_latest_desktop_release
    participant Helper as _get_live_desktop_releases
    participant GitHub as GitHub Releases API

    Client->>Router: GET /v2/desktop/download/latest?channel=beta
    Router->>Helper: _get_live_desktop_releases(platform)
    Helper->>GitHub: get_omi_github_releases(cache_key)
    GitHub-->>Helper: All releases (sorted newest→oldest)
    Note over Helper: Filter: isLive=true, desktop tag, valid version
    Helper-->>Router: Live releases (newest first)

    alt channel == "beta" (NEW PATH)
        loop Iterate all entries (no channel filter)
            Router->>Router: _get_dmg_download_url(entry["release"])
            Router-->>Client: 302 Redirect to DMG (first hit, newest build)
        end
        Router-->>Client: 404 No DMG found (all entries exhausted)
    else channel == "stable"
        loop Filter entries where channel == "stable"
            Router->>Router: _get_dmg_download_url(entry["release"])
            Router-->>Client: 302 Redirect to stable DMG
        end
        Note over Router: Fallback: if no stable, try newest live release
        Router-->>Client: 302 or 404
    end

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Comments Outside Diff (1)

1. backend/tests/unit/test_desktop_updates.py, line 508-519 (link)

   Test name contradicts the new assertion

   The method is named test_beta_no_fallback, which originally described the old behaviour where a channel=beta request returned 404 when no beta-tagged release existed (i.e., there was no fallback to stable). After this PR the assertion has been flipped to expect a 302 to stable.dmg, meaning the beta endpoint now does resolve to a non-beta release. The test name directly contradicts what the test verifies and will mislead future readers.

   Additionally, this is the only redirect test in TestDownloadEndpoint that does not pass follow_redirects=False to AsyncClient, while tests on lines 476–478, 499–501, and 533–536 all do. Although httpx 0.28 defaults to False, the inconsistency increases the risk of a future httpx upgrade silently masking the 302 assertion if behaviour changes.

   Consider renaming and adding the flag:

_{Last reviewed commit: c8eeb9c}