fix stale range cache prefetch state

.beads/interactions.jsonl

@@ -46,3 +46,4 @@
 {"id":"int-176e3ad2","kind":"field_change","created_at":"2026-05-26T04:14:19.812849Z","actor":"dirtydishes","issue_id":"dreamio-meh","extra":{"field":"status","new_value":"closed","old_value":"in_progress","reason":"Fixed range-cache prefetch reprioritization so foreground VLC misses cancel stale speculative work and restart around VLC's actual requested byte range; added regression coverage for the observed jump mismatch."}}
 {"id":"int-56a87fde","kind":"field_change","created_at":"2026-05-26T04:35:35.693504Z","actor":"dirtydishes","issue_id":"dreamio-3pn","extra":{"field":"status","new_value":"closed","old_value":"in_progress","reason":"Implemented backward-biased seek priming, global 1 MB range-cache chunk alignment, bounded protected eviction, partial foreground miss fetching/logging, main-actor VLC delegate handling, tests, and turn documentation."}}
 {"id":"int-91b3db21","kind":"field_change","created_at":"2026-05-26T04:40:10.299245Z","actor":"dirtydishes","issue_id":"dreamio-mi1","extra":{"field":"status","new_value":"closed","old_value":"in_progress","reason":"Used actual foreground VLC reads as prefetch follow signals on hits and changed foreground misses to fetch aligned chunks; added regression tests and updated the turn document."}}
+{"id":"int-ff0aeb09","kind":"field_change","created_at":"2026-05-26T04:47:44.48931Z","actor":"dirtydishes","issue_id":"dreamio-2hw","extra":{"field":"status","new_value":"closed","old_value":"in_progress","reason":"Fixed stale local range-cache prefetch state after cached seek reads and documented the validation."}}

.beads/issues.jsonl

@@ -1,5 +1,6 @@
 {"_type":"issue","id":"dreamio-mun","title":"fix vlc cache loopback port startup","description":"Device logs showed local-cache playback opening http://127.0.0.1:0, because the NWListener ephemeral port was read before the listener reached ready. Wait for the real assigned port before returning the local cache URL.","status":"closed","priority":0,"issue_type":"bug","assignee":"dirtydishes","owner":"dishes@dpdrm.com","created_at":"2026-05-25T22:32:41Z","created_by":"dirtydishes","updated_at":"2026-05-25T22:33:15Z","started_at":"2026-05-25T22:33:14Z","closed_at":"2026-05-25T22:33:15Z","close_reason":"Wait for NWListener ready state before returning the local cache URL; verified tests and simulator build.","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dreamio-8cz","title":"fix stremio external subtitle loading regression","description":"After adding late subtitle forwarding for native playback, Stremio external subtitle loading is failing. Investigate the injected bridge and native subtitle forwarding path, then adjust behavior so Stremio can still load external subtitles while native playback receives late candidates.","status":"closed","priority":0,"issue_type":"bug","assignee":"dirtydishes","owner":"dishes@dpdrm.com","created_at":"2026-05-25T11:05:42Z","created_by":"dirtydishes","updated_at":"2026-05-25T11:07:35Z","started_at":"2026-05-25T11:05:55Z","closed_at":"2026-05-25T11:07:35Z","close_reason":"Hardened subtitle bridge network observers so non-text Stremio subtitle loads are not touched, and made parser traversal deterministic for metadata preservation.","dependency_count":0,"dependent_count":0,"comment_count":0}
+{"_type":"issue","id":"dreamio-2hw","title":"Fix range cache prefetch cursor after cached seek reads","description":"Skipping after the local range cache has warmed can leave prefetch following an older foreground cursor instead of the post-seek cached read position. Update the cache so cached foreground reads can reset the follow cursor and add regression coverage.","status":"closed","priority":1,"issue_type":"bug","assignee":"dirtydishes","owner":"dishes@dpdrm.com","created_at":"2026-05-26T04:45:44Z","created_by":"dirtydishes","updated_at":"2026-05-26T04:47:44Z","started_at":"2026-05-26T04:46:36Z","closed_at":"2026-05-26T04:47:44Z","close_reason":"Fixed stale local range-cache prefetch state after cached seek reads and documented the validation.","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dreamio-mi1","title":"adapt vlc prefetch to actual post-seek reads","description":"Use real foreground VLC reads after a seek as a prefetch signal even when they are cache hits, and fetch aligned chunks for partial foreground misses so the cache warms ahead before VLC reaches the edge of retained data.","status":"closed","priority":1,"issue_type":"bug","assignee":"dirtydishes","owner":"dishes@dpdrm.com","created_at":"2026-05-26T04:38:14Z","created_by":"dirtydishes","updated_at":"2026-05-26T04:40:10Z","started_at":"2026-05-26T04:38:16Z","closed_at":"2026-05-26T04:40:10Z","close_reason":"Used actual foreground VLC reads as prefetch follow signals on hits and changed foreground misses to fetch aligned chunks; added regression tests and updated the turn document.","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dreamio-3pn","title":"reduce vlc seek buffering with range cache priming","description":"Improve VLC local range cache behavior after seek/jump by priming bytes behind the target, using stable global chunk boundaries, retaining useful cached ranges under a byte budget, and adding tests for the observed post-seek request pattern.","status":"closed","priority":1,"issue_type":"task","assignee":"dirtydishes","owner":"dishes@dpdrm.com","created_at":"2026-05-26T04:31:46Z","created_by":"dirtydishes","updated_at":"2026-05-26T04:35:36Z","started_at":"2026-05-26T04:31:51Z","closed_at":"2026-05-26T04:35:36Z","close_reason":"Implemented backward-biased seek priming, global 1 MB range-cache chunk alignment, bounded protected eviction, partial foreground miss fetching/logging, main-actor VLC delegate handling, tests, and turn documentation.","dependency_count":0,"dependent_count":0,"comment_count":0}
 {"_type":"issue","id":"dreamio-meh","title":"Use VLC range requests to reprioritize seek prefetch","description":"Jump logs show duration-based byteOffset estimates can be far behind VLC's actual post-seek range requests, so prefetch keeps warming stale bytes while VLC buffers on higher cache misses.","status":"closed","priority":1,"issue_type":"bug","assignee":"dirtydishes","owner":"dishes@dpdrm.com","created_at":"2026-05-26T04:11:38Z","created_by":"dirtydishes","updated_at":"2026-05-26T04:14:20Z","started_at":"2026-05-26T04:11:40Z","closed_at":"2026-05-26T04:14:20Z","close_reason":"Fixed range-cache prefetch reprioritization so foreground VLC misses cancel stale speculative work and restart around VLC's actual requested byte range; added regression coverage for the observed jump mismatch.","dependency_count":0,"dependent_count":0,"comment_count":0}

Dreamio/ProgressiveHTTPRangeCache.swift

@@ -350,6 +350,7 @@ final class ProgressiveHTTPRangeCacheSession {
     private var prefetchTask: Task<Void, Never>?
     private var activePrefetchWindow: HTTPByteRange?
     private var activePrefetchPreferredOffset: Int64?
+    private var prefetchGeneration: UInt64 = 0
     private var recentSeekRange: HTTPByteRange?
     private var recentForegroundRange: HTTPByteRange?
 
@@ -441,6 +442,8 @@ final class ProgressiveHTTPRangeCacheSession {
         }
 
         prefetchTask?.cancel()
+        prefetchGeneration += 1
+        let generation = prefetchGeneration
         let window = explicitWindow ?? targetWindow(aroundByteOffset: offset)
         activePrefetchWindow = window
         activePrefetchPreferredOffset = offset
@@ -462,6 +465,9 @@ final class ProgressiveHTTPRangeCacheSession {
                 if !store.hasData(for: chunk) {
                     do {
                         let data = try await fetcher.fetch(range: chunk)
+                        guard !Task.isCancelled else {
+                            return
+                        }
                         store.insert(data: data, at: chunk.start)
                         evictOverBudget(protecting: window)
 #if DEBUG
@@ -478,6 +484,9 @@ final class ProgressiveHTTPRangeCacheSession {
                     }
                 }
             }
+            guard self.prefetchGeneration == generation else {
+                return
+            }
             self.activePrefetchWindow = nil
             self.activePrefetchPreferredOffset = nil
         }
@@ -485,6 +494,7 @@ final class ProgressiveHTTPRangeCacheSession {
 
     func cancelPrefetch() {
         prefetchTask?.cancel()
+        prefetchGeneration += 1
         activePrefetchWindow = nil
         activePrefetchPreferredOffset = nil
     }
@@ -512,10 +522,12 @@ final class ProgressiveHTTPRangeCacheSession {
               abs(range.start - preferredOffset) >= responseChunkSize else {
             return
         }
+        let nextOffset = range.end + 1
 #if DEBUG
-        print("[DreamioRangeCache] prefetch follow-foreground from=\(preferredOffset) to=\(range.end + 1)")
+        let reason = nextOffset < preferredOffset ? "reanchor-foreground" : "follow-foreground"
+        print("[DreamioRangeCache] prefetch \(reason) from=\(preferredOffset) to=\(nextOffset)")
 #endif
-        prefetch(aroundByteOffset: range.end + 1, forceRestart: true)
+        prefetch(aroundByteOffset: nextOffset, forceRestart: true)
     }
 
     private func targetWindow(aroundByteOffset offset: Int64) -> HTTPByteRange {