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+# Archive.org Integration for Dead Links
+
+**Date:** 2026-02-10
+**Status:** Proposed
+**Branch:** tumble-dark
+
+## Problem
+
+Tumble has ~20 years of archived links. Over time, many have gone dead
+(404s, domain expirations, content removals). The existing system
+detects dead links and shows an error badge, but offers no way to view
+the original content. Archive.org's Wayback Machine likely has snapshots
+of many of these links.
+
+## Solution
+
+Integrate with the Wayback Machine Availability API to check whether
+dead links have archived snapshots. When a snapshot exists, show a
+"View on Archive.org" link alongside the error badge so users can still
+access the original content.
+
+## Data Model
+
+New `archive_lookups` table, independent of `ircLink` and
+`link_previews`:
+
+| Column | Type | Purpose |
+|--------|------|---------|
+| `url` | string, primary key | The original link URL |
+| `archive_url` | string, nullable | Wayback snapshot URL |
+| `snapshot_at` | timestamp, nullable | When the snapshot was captured |
+| `status` | string | `found`, `not_found`, or `error` |
+| `checked_at` | timestamp | When we last queried archive.org |
+
+GORM model:
+
+```go
+type ArchiveLookup struct {
+    URL        string     `gorm:"column:url;primaryKey"`
+    ArchiveURL *string    `gorm:"column:archive_url"`
+    SnapshotAt *time.Time `gorm:"column:snapshot_at"`
+    Status     string     `gorm:"column:status"`
+    CheckedAt  time.Time  `gorm:"column:checked_at"`
+}
+```
+
+### Key decisions
+
+- **Keyed on URL, not IRCLink ID.** Multiple IRCLinks can share the
+  same URL (duplicates). One lookup per unique URL.
+- **Three-state status.** `found` = snapshot exists, `not_found` =
+  checked but no snapshot, `error` = archive.org was unreachable.
+  No row = never checked.
+- **No cascade on IRCLink deletion.** Orphaned rows are harmless and
+  small. This matches existing `link_previews` behavior.
+
+## Archive.org API Wrapper
+
+Single function wrapping the Wayback Machine Availability API:
+
+- **Endpoint:** `GET https://archive.org/wayback/available?url={url}`
+- **Response:** `{"archived_snapshots": {"closest": {"url": "...",
+  "timestamp": "20190115120000", "status": "200"}}}`
+- Empty `archived_snapshots` or missing `closest` means no snapshot.
+- Parses `timestamp` (format `YYYYMMDDHHmmss`) into `time.Time`.
+- Returns `(archiveURL, snapshotTime, error)`.
+- Uses `golang.org/x/time/rate` limiter at 5 req/s.
+
+## Lookup Strategy: Hybrid
+
+Two paths for checking archive.org:
+
+### Background batch job
+
+Runs alongside the existing scheduler (daily kittens):
+
+- **Trigger:** On app startup, then once daily.
+- **Targets:** URLs with a cached error in `link_previews` but no row
+  (or `error`-status row) in `archive_lookups`.
+- **Rate:** ~5 req/s with sleeps between requests.
+- **Logging:** Progress updates (e.g. "checked 50/500 dead links").
+
+Recheck policy:
+
+| Status | Recheck after |
+|--------|---------------|
+| `found` | Never |
+| `not_found` | 30 days |
+| `error` | 24 hours |
+
+On first deploy, backfills ~500-1000 dead links in a few minutes.
+Subsequent daily runs only process newly dead links and stale
+`not_found`/`error` rechecks.
+
+**Restart safety:** Results are persisted. Restarting the app resumes
+from where it left off — already-checked URLs are skipped.
+
+### Lazy on-demand lookup
+
+For newly detected dead links:
+
+1. After `cacheErrorPreview()` stores an error, check if an
+   `archive_lookups` row exists for the URL.
+2. If no row (or stale row), call the Wayback API inline (~200-500ms).
+3. Store the result in `archive_lookups`.
+4. Return archive data alongside the error response.
+
+If a row already exists and is fresh, include it in the response
+without an API call.
+
+## API Response Changes
+
+The existing `GET /api/v1/preview?url=...` error response is extended:
+
+```json
+{
+  "error": "Not Found",
+  "status": "404",
+  "archive_url": "https://web.archive.org/web/20190115/...",
+  "archive_snapshot_at": "2019-01-15T12:00:00Z"
+}
+```
+
+No new API endpoints. Archive data piggybacks on the existing preview
+flow.
+
+## Frontend Changes
+
+In `handlePreviewData()`, when `data.error` is present and
+`data.archive_url` exists, append an archive link after the error
+badge:
+
+```
+[404] example.com/dead-page  ·  View on Archive.org (Jan 2019)
+```
+
+- Archive link opens in a new tab.
+- Styled for both the default theme and Scott Mode.
+- If no archive snapshot exists, behavior is unchanged from today.
+
+## Store Interface Additions
+
+Four new methods on the Store interface:
+
+```go
+GetArchiveLookup(ctx context.Context, url string) (*ArchiveLookup, error)
+UpsertArchiveLookup(ctx context.Context, lookup *ArchiveLookup) error
+GetUncheckedDeadLinkURLs(ctx context.Context) ([]string, error)
+GetStaleArchiveLookups(ctx context.Context, recheckAfter time.Duration) ([]string, error)
+```
+
+## Scope
+
+### What changes
+
+- New `ArchiveLookup` model in `internal/data/store.go`
+- Four new store methods in `internal/data/gorm_store.go`
+- New archive.org API wrapper (new file in `internal/handler/` or
+  `internal/service/`)
+- New scheduled job in `internal/scheduler/`
+- Extended `cacheErrorPreview()` flow in `internal/handler/preview.go`
+- Extended error response in preview handler
+- Frontend JS in `index.html` (both default and Scott Mode)
+- CSS for archive link styling (both themes)
+
+### What does NOT change
+
+- IRCLink model or table
+- LinkPreview model or table
+- Preview cache TTL logic
+- Search exclusion logic
+- Non-error preview rendering
+- API endpoints or authentication
+- OpenAPI spec (archive data is an optional extension of existing
+  preview response, not a new endpoint)
+
+## Future Work
+
+- Submit dead links to archive.org's Save Page Now API for links with
+  no snapshot
+- Show archive availability in search results
+- Admin dashboard showing dead link / archive coverage stats