@@ -11,7 +11,9 @@
 When a translation request is made, the system first checks the cache for an existing translation using a hash key. If a cached translation is found, it is returned immediately, avoiding an external translation API call. If the cache does not contain the requested translation, the system performs the translation using the selected provider (Google, Microsoft, or an AI model). After a successful translation, the result is stored in the cache with the hash key and a timestamp.
 
 ### Cache Key Generation
-The cache key is generated as a hash of the following values:
+
+#### Article Translation
+The cache key for article translation is generated as a hash of the following values:
 - The original text to be translated
 - The provider configuration
 - The configured source language code (as set by the user or 'auto'; detected language is not included)
@@ -20,6 +22,26 @@
 - **For LLM (AI) providers with AI Content Aware enabled:** Article context (title and content)
 
 **Note:** The detected language code (`detectedCode`) is intentionally excluded from the cache key. This ensures that cache lookups remain stable even if language detection changes after translation. For LLM providers, the prompt used for translation is included in the cache key. This means that if you change the translation prompt (for example, by editing or selecting a different custom prompt), the cache will be invalidated for that prompt, and new translations will be fetched and cached accordingly. For non-LLM providers, the prompt is not included in the cache key.
+
+#### Subtitle Translation
+Subtitle translation uses separate cache key generation logic from article translation. The cache key for subtitle translation includes all the standard components (text, provider, languages, prompt for LLM providers) plus additional subtitle-specific context:
+
+**When AI Content Aware is enabled:**
+- **Summary status flag:** Either `subtitleSummary=ready` or `subtitleSummary=missing`
+- **Summary content:** The actual summary text (when available), prepended with `summary:`
+
+This means that subtitle translations are cached separately based on whether AI Smart Context summary was available at translation time. The same subtitle text will have different cache entries when:
+1. Translated with AI Smart Context summary available vs. missing
+2. Translated with different summary content (e.g., different videos or context)
+
+**Implementation Details:**
+The subtitle summary context hash is computed using the `buildSubtitlesSummaryContextHash()` function in `translator.ts`, which hashes the cleaned subtitle transcript content and provider configuration. The summary is fetched asynchronously in the background via the `getSubtitlesSummary` message handler and injected into translation requests once available. If the context hash changes (e.g., video navigation), stale summaries are discarded to ensure cache consistency.
+
+**Impact on Cache Behavior:**
+- Subtitle translations without a summary are cached separately from those with a summary
+- This prevents cache mismatches when AI Smart Context becomes available
+- Cache invalidation occurs when summary content or availability changes
+- The decoupled summary fetch allows translation to start immediately without waiting for summary generation
 
 #### Article Context in Cache Keys (LLM Providers with AI Content Aware)
 
@@ -83,7 +105,9 @@
 
 **Summary of Key Points:**
 - The cache key includes the resolved prompt for LLM providers; changing the prompt invalidates the cache for those translations.
-- For LLM providers with AI Content Aware enabled, the cache key also includes article context (title and first 1000 characters of content).
+- For article translation with LLM providers and AI Content Aware enabled, the cache key includes article context (title and first 1000 characters of content).
+- For subtitle translation with AI Content Aware enabled, the cache key includes a summary status flag and summary content (when available).
+- Subtitle translations are cached separately based on whether AI Smart Context summary was available at translation time.
 - Only custom prompts are stored in user config; the default prompt is a code constant.
 - Cache entries older than 7 days are automatically deleted.
 - Users can manually clear the cache from the Options page.