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patch_history/RETRIEX_SSE_RECONNECT_REPLAY_FIX_README.md

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+# RetrieX SSE reconnect replay fix
+
+Patch-only fix for fragile browser streaming after the job-based EventSource flow.
+
+## Problem
+
+EventSource is allowed to reconnect automatically when the browser, proxy or PHP/Nginx connection is interrupted. The previous job guard treated a second `/ask-sse/{jobId}` connection while the job was still `running` as an application error. In the UI this could append messages like:
+
+```text
+event: error
+data: Der Antwort-Stream läuft bereits oder wurde nach einem Verbindungsabbruch erneut geöffnet...
+```
+
+This happened especially in slower Shopware/search flows, but it could also happen in pure RAG answers.
+
+## Change
+
+- Streamed answer chunks now receive monotonically increasing SSE `id:` values.
+- Each streamed chunk is additionally written to a per-job replay buffer under `var/stream_jobs/*.stream.ndjson`.
+- If EventSource reconnects to a job that is already `running`, the controller no longer emits the misleading duplicate-stream error.
+- Instead, the reconnecting request reads `Last-Event-ID`, replays missing chunks and tails the still-running job until it completes, fails or is marked interrupted.
+- Completed jobs can replay any missing chunks and then emit `done`.
+- The frontend tracks `event.lastEventId` and ignores duplicate/replayed chunks defensively.
+- Expired job cleanup also removes the replay buffer sidecar file.
+
+## Changed files
+
+- `src/Controller/AskSseController.php`
+- `public/assets/js/base.js`
+
+## Safety
+
+This patch does not change retrieval, PromptBuilder, AgentRunner, scoring, intent detection, Shopware query generation or RAG behavior. It only changes the transport/reconnect layer for SSE.
+
+## After installing
+
+```bash
+php bin/console cache:clear
+php bin/console mto:agent:config:validate
+php bin/console mto:agent:regression:test
+```
+
+Hard-refresh the browser or clear browser cache because `public/assets/js/base.js` changed.