Bluesky notification poll returns 400 Bad Request due to invalid seenAt datetime format

[houko]

Description

The Bluesky channel adapter successfully authenticates (createSession returns 200), but subsequent notification polling via app.bsky.notification.listNotifications consistently returns 400 Bad Request.

Root Cause

The binary constructs the notification poll URL as:

/xrpc/app.bsky.notification.listNotifications?limit=25&seenAt=<value>

The seenAt value does not conform to the AT Protocol datetime specification (RFC-3339 / ISO-8601). The Bluesky API responds with:

{"error":"InvalidRequest","message":"Error: seenAt must be an valid atproto datetime (both RFC-3339 and ISO-8601)"}

Reproduction

1. Configure Bluesky channel with valid credentials in config.toml
2. Start daemon
3. Observe logs: authentication succeeds, then continuous 400 errors every ~5 seconds:

INFO  openfang_channels::bluesky: Bluesky adapter authenticated as did:plc:...
INFO  openfang_api::channel_bridge: bluesky channel bridge started
WARN  openfang_channels::bluesky: Bluesky: notification fetch returned 400 Bad Request
WARN  openfang_channels::bluesky: Bluesky: notification fetch returned 400 Bad Request
(repeats every ~5s)

Verification

Direct AT Protocol API calls confirm:

• listNotifications?limit=25 (without seenAt) → 200 OK
• listNotifications?limit=25&seenAt=<invalid> → 400 Bad Request

Workaround

Binary patch &seenAt= → &_seen_= (same byte length) + codesign --force --sign - to re-sign. The Bluesky API ignores unknown query parameters and returns 200.

Expected Behavior

The seenAt parameter should be formatted as a valid RFC-3339 datetime string (e.g. 2026-03-07T11:00:00.000Z).

Environment

• OpenFang: v0.3.26
• Platform: macOS (darwin arm64)
• Bluesky handle: confirmed working via direct API test

[jaberjaber23]

Fixed the seenAt datetime format in the Bluesky adapter. Was using a custom chrono format string that produced invalid AT Protocol datetimes. Now uses to_rfc3339_opts(SecondsFormat::Millis, true) which produces proper RFC-3339 strings. Both the notification updateSeen and post createdAt are fixed.