ML-156: plan revisions

backlog/tasks/ml-156 - Explore-alternatives-to-reduce-token-usage-when-providing-collection-context-to-LLM-for-collection-chat.md

@@ -6,7 +6,7 @@ title: >-
 status: To Do
 assignee: []
 created_date: '2026-05-02 16:02'
-updated_date: '2026-05-02 16:13'
+updated_date: '2026-05-02 18:10'
 labels:
   - chat
   - collection
@@ -54,7 +54,7 @@ The `Collection.collection_summary/0` function loads ALL records from the DB, fo
 ## Implementation Plan
 
 <!-- SECTION:PLAN:BEGIN -->
-## Approach: OpenAI `file_search` tool
+## Approach: OpenAI `file_search` tool + Oban-managed file lifecycle
 
 Upload the collection catalog as a file to OpenAI, create a vector store, and use the Responses API's built-in `file_search` tool. OpenAI automatically performs semantic search over the file and includes relevant results inline in the response stream — no SSE event handling changes, no orchestration loop.
 
@@ -62,96 +62,327 @@ Token savings: ~9,000 → ~100 tokens per chat (99% reduction). File search resu
 
 Research and alternative analysis: see [ML-156 Research document](backlog://document/doc-1).
 
+### Architecture decisions
+
+1. **Chat sessions never upload or refresh files.** They read `vector_store_id` from `Secrets`. If missing, they fall back to stats-only instructions (no errors surfaced to the user).
+2. **File upload and refresh happen exclusively in Oban workers.** No `Task.start`, no `start_async` — all OpenAI API calls for file management are serialized through a unique Oban worker with a 5-minute debounce window.
+3. **Refresh is triggered at the lowest level.** `Records.create_record/1`, `Records.update_record/2`, and `Records.delete_record/1` enqueue the refresh worker on success. This catches all mutation paths (Index, Show, cart import, barcode scan, batch operations) without PubSub or LiveView-specific hooks.
+4. **The full `collection_summary/0` (catalog + stats) is eliminated from the LiveView page load.** `CollectionLive.Index.mount/3` loads only a lightweight `stats_summary/0` — the same aggregated stats (record count, artist count, genre/format/era breakdowns) but without the per-record catalog lines. The full catalog is only loaded inside the Oban worker when a file upload/refresh is needed. Stats are ~200 tokens, always included in instructions, giving the LLM high-level collection awareness even before file search.
+
 ---
 
-### Phase 1: OpenAI API extensions
+### Phase 1: OpenAI API extensions (7 new endpoints)
 
 Add to `OpenAI.API` (following existing `new_request/1` pattern with `Req.RateLimiter` on `:open_ai` bucket):
 
-- `upload_file(file_content, config)` — `POST /v1/files` with multipart body, `purpose: "assistants"`
+- `upload_file(file_content, filename, config)` — `POST /v1/files` with multipart body (`purpose: "assistants"`, `file` field containing the catalog text). Uses `Req` multipart support.
-- `create_vector_store(name, config)` — `POST /v1/vector_stores`
+- `create_vector_store(name, config)` — `POST /v1/vector_stores` with `%{name: name}` body.
-- `add_file_to_vector_store(store_id, file_id, config)` — `POST /v1/vector_stores/{id}/files`
+- `add_file_to_vector_store(store_id, file_id, config)` — `POST /v1/vector_stores/{store_id}/files` with `%{file_id: file_id}` body.
-- `delete_file(file_id, config)` — `DELETE /v1/files/{id}` (cleanup on re-upload)
+- `remove_file_from_vector_store(store_id, file_id, config)` — `DELETE /v1/vector_stores/{store_id}/files/{file_id}`. Detaches the old file from the vector store before deleting.
+- `delete_file(file_id, config)` — `DELETE /v1/files/{file_id}`. Called after detaching from vector store.
+- `get_file(file_id, config)` — `GET /v1/files/{file_id}`. Returns file metadata including `status` field (`uploaded`, `processed`, `error`). Used to poll indexing completion after attach.
+- `list_files(config)` — `GET /v1/files`. Returns paginated list of files. Used by the periodic cleanup worker to find orphaned resources.
 
-~60 lines.
+~90 lines.
 
-### Phase 2: File management module
+---
+
+### Phase 2: FileStore module
 
 Create `MusicLibrary.Chats.CollectionChat.FileStore`:
 
-```
+```elixir
 defmodule MusicLibrary.Chats.CollectionChat.FileStore do
   @moduledoc """
   Manages the collection catalog file lifecycle at OpenAI.
   Persists file_id and vector_store_id via Secrets.
+  
+  All OpenAI API calls happen inside Oban workers — never from chat
+  sessions or LiveViews. The chat session path only calls get_vector_store_id/0.
   """
 
-  @spec ensure_uploaded() :: {:ok, String.t()} | {:error, term()}
+  @spec upload_or_refresh() :: :ok | {:error, term()}
-  def ensure_uploaded do
+  def upload_or_refresh do
-    # Check Secrets for existing file_id + vector_store_id
+    # 1. Check Secrets for existing file_id + vector_store_id
-    # If missing, call Collection.collection_summary/0
+    # 2. If missing → initial upload flow:
-    # Upload to OpenAI, create vector store, attach file
+    #    a. Call Collection.collection_summary/0 to get catalog text
-    # Persist IDs via Secrets.store/2
+    #    b. POST /v1/files → file_id
-    # Return {:ok, vector_store_id}
+    #    c. POST /v1/vector_stores → vector_store_id
-  end
+    #    d. POST /v1/vector_stores/{id}/files → attach
-
+    #    e. Poll GET /v1/files/{file_id} until status == "processed"
-  @spec refresh() :: :ok | {:error, term()}
+    #       (max 10 attempts, 2s backoff)
-  def refresh do
+    #    f. Persist both IDs via Secrets.store/2
-    # Delete old file from OpenAI (if exists)
+    # 3. If present → refresh flow:
-    # Regenerate summary, upload new file
+    #    a. Call Collection.collection_summary/0
-    # Attach to existing vector store (re-indexes automatically)
+    #    b. POST /v1/files → new_file_id
+    #    c. POST /v1/vector_stores/{store_id}/files → attach new file
+    #    d. Poll GET /v1/files/{new_file_id} until status == "processed"
+    #    e. DELETE /v1/vector_stores/{store_id}/files/{old_file_id} → detach old
+    #    f. DELETE /v1/files/{old_file_id} → delete old file
+    #    g. Update file_id in Secrets (vector_store_id unchanged)
+    # 4. Log errors at each step; return :ok or {:error, reason}
   end
 
   @spec get_vector_store_id() :: {:ok, String.t()} | {:error, :not_uploaded}
   def get_vector_store_id do
     # Read vector_store_id from Secrets
+    # Return {:ok, id} or {:error, :not_uploaded}
+  end
+
+  @spec cleanup_orphaned_files() :: :ok
+  def cleanup_orphaned_files do
+    # Called by periodic cleanup worker
+    # 1. Read known file_id + vector_store_id from Secrets
+    # 2. Call GET /v1/files to list all files
+    # 3. Delete any file whose id doesn't match the known file_id
+    #    (with safety check: also detach from any vector store first)
+    # 4. Log orphan count, return :ok
   end
 end
 ```
 
-- `ensure_uploaded/0` — lazy init on first chat; idempotent
+Key design properties:
-- `refresh/0` — called when records are added/edited/deleted (async, non-blocking)
+- `upload_or_refresh/0` is the single entry point called by the Oban worker — never by chat sessions
-- `get_vector_store_id/0` — reads from `Secrets`; returns error if never uploaded
+- `get_vector_store_id/0` is the single entry point called by chat sessions — read-only, no side effects
+- `cleanup_orphaned_files/0` is a safety net for edge cases (e.g., Secrets write failed after OpenAI upload succeeded)
 
-~50 lines.
+~70 lines.
 
-### Phase 3: Chat streaming changes
+---
 
-**`OpenAI.chat_stream/2`** — add optional `vector_store_ids` option:
+### Phase 3: Oban workers
+
+#### 3a. RefreshCollectionFile worker
+
+Create `MusicLibrary.Worker.RefreshCollectionFile`:
 
 ```elixir
-def chat_stream(messages, opts) do
+defmodule MusicLibrary.Worker.RefreshCollectionFile do
+  use Oban.Worker,
+    queue: :default,
+    unique: [period: 300, keys: [:worker]],
+    max_attempts: 3
+
+  @impl true
+  def perform(_job) do
+    case MusicLibrary.Chats.CollectionChat.FileStore.upload_or_refresh() do
+      :ok -> :ok
+      {:error, reason} -> {:error, reason}
+    end
+  end
+end
+```
+
+- `unique: [period: 300, keys: [:worker]]` — 5-minute debounce window. Only one refresh can be executing or scheduled at a time. Rapid record mutations (cart import of 50 records) each call `Oban.insert` but only the first insert succeeds; subsequent inserts within the 300s unique window are silently ignored by Oban.
+- `max_attempts: 3` — transient OpenAI failures get 2 retries.
+- Queue `:default` (concurrency 10) — the worker is fast (a few API calls), no need for a dedicated queue.
+
+Enqueued from two places:
+1. **Record mutations** — `Records.create_record/1`, `update_record/2`, `delete_record/1` (see Phase 4)
+2. **Cron** — every hour in both dev and prod, to handle initial upload after deploy and recovery after failures:
+
+```elixir
+# config/prod.exs (add to crontab)
+{"0 * * * *", MusicLibrary.Worker.RefreshCollectionFile}
+
+# config/dev.exs (add to crontab)
+{"*/15 * * * *", MusicLibrary.Worker.RefreshCollectionFile}
+```
+
+~15 lines.
+
+#### 3b. CleanupOrphanedOpenAIFiles worker
+
+Create `MusicLibrary.Worker.CleanupOrphanedOpenAIFiles`:
+
+- Cron: monthly (1st of month, 11 AM)
+- Calls `FileStore.cleanup_orphaned_files/0`
+- Queue: `:default`
+- `max_attempts: 2`
+
+~12 lines.
+
+---
+
+### Phase 4: Records context + Collection context + LiveView changes
+
+#### 4a. Records context — enqueue refresh on mutations
+
+In `lib/music_library/records.ex`, after each successful mutation, enqueue the refresh worker **outside** the `with` chain (non-blocking — the mutation succeeds regardless of enqueue result):
+
+```elixir
+def create_record(attrs \\ %{}) do
+  with {:ok, record} <- do_create_record(attrs),
+       record = Enrichment.best_effort_extract_colors(record),
+       :ok <- refresh_artist_info_async(record) do
+    enqueue_collection_file_refresh()
+    {:ok, record}
+  end
+end
+
+def update_record(%Record{} = record, attrs) do
+  with {:ok, updated_record} <- do_update_record(record, attrs),
+       :ok <- refresh_artist_info_async(updated_record) do
+    enqueue_collection_file_refresh()
+    {:ok, updated_record}
+  end
+end
+
+def delete_record(%Record{} = record) do
+  with {:ok, record} <- Repo.delete(record) do
+    record
+    |> Record.artist_ids()
+    |> Enum.each(fn artist_id ->
+      Artists.prune_artist_info_async(artist_id)
+    end)
+
+    enqueue_collection_file_refresh()
+    {:ok, record}
+  end
+end
+
+defp enqueue_collection_file_refresh do
+  %{} |> MusicLibrary.Worker.RefreshCollectionFile.new() |> Oban.insert()
+end
+```
+
+- `Oban.insert/1` (not `insert!`) — failures to enqueue are silently ignored; the hourly cron acts as a safety net.
+- The enqueue happens after the `with` succeeds, ensuring we only refresh when data actually changed.
+- All mutation paths are covered: single create (AddRecord, barcode scan), cart import (batch creates via `ImportFromMusicbrainzReleaseGroup` worker, which calls `create_record/1` internally), edit (Index and Show), delete.
+
+~15 lines.
+
+#### 4b. Collection context — add `stats_summary/0` and `count_records/0`
+
+Add to `lib/music_library/collection.ex`:
+
+```elixir
+@spec count_records() :: non_neg_integer()
+def count_records do
+  from(r in Record, where: not is_nil(r.purchased_at))
+  |> Repo.aggregate(:count)
+end
+
+@spec stats_summary() :: {String.t(), non_neg_integer()}
+def stats_summary do
+  # Same record load as collection_summary/0 (the heavy SQL query),
+  # but only computes the stats header — NO per-record catalog formatting.
+  # Returns {stats_string, group_count}.
+  # Example stats_string:
+  #   "# Stats: 500 releases, 200 artists\nGenres: rock 150, ...\nFormats: ...\nEras: ..."
+  records = from(r in Record, where: not is_nil(r.purchased_at), select: ^essential_fields()) |> Repo.all()
+  groups = records |> Enum.group_by(& &1.musicbrainz_id)
+  stats = build_stats(records, length(groups))
+  {stats, length(groups)}
+end
+```
+
+~10 lines. `collection_summary/0` remains in the module — it's now only called by `FileStore.upload_or_refresh/0` (inside the Oban worker) to generate the catalog text for file upload. `stats_summary/0` extracts the lightweight stats portion for the LiveView to load (still a full table scan, but skips the expensive per-record string formatting — ~200 tokens of output vs ~9,000).
+
+#### 4c. CollectionLive.Index — load stats instead of full catalog
+
+Replace the heavy `start_async(:collection_summary, &Collection.collection_summary/0)` with `stats_summary`:
+
+```elixir
+# In mount/3:
+|> assign(:collection_stats, {"", 0})
+|> start_async(:collection_stats, fn -> Collection.stats_summary() end)
+
+# Rename handle_async:
+def handle_async(:collection_stats, {:ok, stats}, socket) do
+  {:noreply, assign(socket, :collection_stats, stats)}
+end
+
+def handle_async(:collection_stats, {:exit, _reason}, socket) do
+  {:noreply, socket}
+end
+
+# In the template — pass stats as chat_context:
+chat_context={@collection_stats}
+```
+
+The `@collection_summary` assign is removed. The Chat component receives `{stats_string, record_count}`, matching the existing tuple shape so no Chat component changes are needed.
+
+~8 lines (mostly renames).
+
+---
+
+### Phase 5: Chat streaming changes
+
+#### 5a. OpenAI facade — accept `:vector_store_ids` option
+
+Modify `OpenAI.chat_stream/2` to pass tools to the API layer:
+
+```elixir
+def chat_stream(messages, opts) when is_list(messages) do
   model = Keyword.get(opts, :model, "gpt-4.1")
+  temperature = Keyword.get(opts, :temperature, 0.7)
+  instructions = Keyword.get(opts, :instructions, "")
+  on_chunk = Keyword.fetch!(opts, :on_chunk)
   vector_store_ids = Keyword.get(opts, :vector_store_ids, [])
 
-  tools = [%{type: "web_search_preview"}]
+  tools = build_tools(vector_store_ids)
-  tools = if vector_store_ids != [],
-    do: [%{type: "file_search", vector_store_ids: vector_store_ids} | tools],
-    else: tools
 
-  # ... rest unchanged
+  API.chat_stream(messages, instructions, model, temperature, open_ai_config(), on_chunk, tools)
+end
+
+defp build_tools([]), do: [%{type: "web_search_preview"}]
+defp build_tools(ids) when is_list(ids) do
+  [%{type: "file_search", vector_store_ids: ids}, %{type: "web_search_preview"}]
 end
 ```
 
-**`OpenAI.API.chat_stream/6`** — accept tools as parameter instead of hardcoding (or add `tools` parameter):
+~10 lines.
+
+#### 5b. OpenAI.API — accept optional tools parameter
+
+Add a 7-arity overload to `API.chat_stream`:
 
 ```elixir
-def chat_stream(messages, instructions, model, temperature, config, cb, tools \\ nil) do
+def chat_stream(messages, instructions, model, temperature, config, cb) do
-  tools = tools || [%{type: "web_search_preview"}]
+  chat_stream(messages, instructions, model, temperature, config, cb, [%{type: "web_search_preview"}])
-  # ... use tools in json body
+end
+
+def chat_stream(messages, instructions, model, temperature, config, cb, tools) when is_list(tools) do
+  config
+  |> new_request()
+  |> Req.merge(
+    url: "/v1/responses",
+    receive_timeout: 60_000,
+    connect_options: [timeout: 5_000],
+    json: %{
+      model: model,
+      instructions: instructions,
+      input: messages,
+      tools: tools,
+      stream: true,
+      temperature: temperature
+    },
+    into: :self
+  )
+  |> do_chat_stream(cb)
 end
 ```
 
-**`CollectionChat.stream_response/3`:**
+- Uses function clause pattern matching (`when is_list(tools)`) rather than default argument with `||`, avoiding the falsy-empty-list pitfall.
+- The 6-arity version is preserved for backward compatibility (existing RecordChat and ArtistChat callers).
+
+~5 lines.
+
+#### 5c. CollectionChat — new instructions and streaming logic
+
+Update `CollectionChat`:
 
 ```elixir
-def stream_response(messages, {_summary, record_count}, callback) do
+@impl true
-  instructions = build_instructions(record_count)
+def stream_response(messages, {stats, record_count}, callback) do
+  instructions = build_instructions(stats, record_count)
 
-  vector_store_opts = case FileStore.get_vector_store_id() do
+  vector_store_opts =
-    {:ok, id} -> [vector_store_ids: [id]]
+    case FileStore.get_vector_store_id() do
-    {:error, _} -> []  # fall back to stats-only
+      {:ok, id} -> [vector_store_ids: [id]]
-  end
+      {:error, :not_uploaded} -> []  # fall back to stats-only
+    end
 
   OpenAI.chat_stream(messages, [
     on_chunk: callback,
@@ -159,63 +390,123 @@ def stream_response(messages, {_summary, record_count}, callback) do
     model: "gpt-5.1"
   ] ++ vector_store_opts)
 end
-```
 
-~15 lines.
+defp build_instructions(stats, record_count) do
-
-### Phase 4: Prompt changes
-
-Update `CollectionChat.build_instructions/2`:
-
-```elixir
-defp build_instructions(record_count) do
   Prompt.build("""
   Answer questions about the user's music collection.
-  The collection contains #{record_count} records.
+  Use the provided stats and file search to answer questions
-  Use file search to find specific records when the user asks about \
+  about the collection.
+
+  #{stats}
+
+  The collection contains #{record_count} records in total.
+
+  Use file search to find specific records when the user asks about
   artists, albums, genres, or formats in their collection.
 
+  If file search returns no results for a query, say so honestly —
+  don't guess or invent records. If you're unsure whether a record
+  exists, mention that it wasn't found in the collection.
+
   # Mentioning artists/albums
 
-  **IF YOU MENTION AN ARTIST NAME OR ALBUM NAME, wrap it in "[[name]]", \
+  **IF YOU MENTION AN ARTIST NAME OR ALBUM NAME, wrap it in "[[name]]",
   for example "[[Steven Wilson]]"
   """)
 end
 ```
 
-Key changes:
+Key changes from current code:
-- Remove `#{collection_summary}` interpolation entirely
+- `stream_response/3` keeps the `{tuple, count}` signature shape — the stats string replaces the catalog text
-- Remove `Collection catalog:` section
+- `build_instructions/2` interpolates aggregated stats (~200 tokens) instead of the full catalog (~9,000 tokens)
-- Remove `Use the provided collection catalog as your primary reference`
+- `FileStore.get_vector_store_id/0` is the only FileStore function called from the chat path
-- Add guidance to use file search for specific record lookup
+- On `{:error, :not_uploaded}`, vector_store_opts is empty → `build_tools([])` returns only `web_search_preview` → stats-only fallback (still useful for aggregate questions)
-- `stream_response/3` signature changes from `{summary, count}` to just `count` (summary only used for stats, which we no longer pass)
+- Added explicit guidance for when file search returns no results
+- The "Collection catalog:" section is removed; replaced with stats inline
 
-~10 lines.
+~18 lines (modifications to existing code).
 
-### Phase 5: Trigger refresh on collection changes
+---
-
-In `CollectionLive.Index`, handle record add/edit/delete events:
-
-```elixir
-# In handle_info for RecordForm saved / AddRecord imported / delete:
-def handle_info({MusicLibraryWeb.Components.RecordForm, {:saved, _record}}, socket) do
-  Task.start(&MusicLibrary.Chats.CollectionChat.FileStore.refresh/0)
-  IndexActions.handle_record_saved(socket)
-end
-```
-
-Or use the existing PubSub topic `"records:#{id}"` to trigger refresh from a central place. Debounce rapid changes (multiple quick adds) with a short timer.
-
-~20 lines.
 
 ### Phase 6: Testing
 
-- `test/open_ai/api_test.exs` — test `upload_file`, `create_vector_store`, `add_file_to_vector_store`, `delete_file` endpoints via `Req.Test` stubs
+#### 6a. OpenAI.API endpoint tests (`test/open_ai/api_test.exs`)
-- `test/music_library/chats/collection_chat/file_store_test.exs` — test `ensure_uploaded` (first-time upload), `refresh` (re-upload), `get_vector_store_id` (missing, present), and `Secrets` persistence
-- `test/music_library/chats/collection_chat_test.exs` — verify instructions no longer contain catalog; verify `file_search` tool included when vector store is available; verify fallback to stats-only when unavailable
-- `test/music_library/collection_test.exs` — existing `collection_summary/0` tests continue to pass unchanged
 
-Estimated total: ~150 lines across 5-6 files. Low risk — no changes to core streaming infrastructure.
+Add test blocks for the 7 new endpoints, following existing `Req.Test.stub` patterns:
+- `upload_file/3` — verify multipart body includes `purpose: "assistants"` and file content; test success (200 + file JSON) and error (500) responses
+- `create_vector_store/2` — verify request body has `name` field; test success and error
+- `add_file_to_vector_store/3` — verify URL path includes store_id; test success and error
+- `remove_file_from_vector_store/3` — verify DELETE request; test 200 and 404 (already removed)
+- `delete_file/2` — verify DELETE request; test success
+- `get_file/2` — test `status: "processed"` (success), `status: "uploaded"` (still processing), and error
+- `list_files/1` — test paginated response with file list
+- Rate-limit error handling (429 → `ErrorResponse` with `:rate_limit` kind) for each endpoint
+
+~80 lines.
+
+#### 6b. FileStore tests (`test/music_library/chats/collection_chat/file_store_test.exs`)
+
+Test `FileStore` functions with `Req.Test` stubs and direct `Secrets` manipulation:
+- `upload_or_refresh/0` — first-time upload (no secrets → creates file + store + attaches → secrets populated)
+- `upload_or_refresh/0` — refresh (secrets present → uploads new file → attaches → detaches old → deletes old → updates file_id in secrets)
+- `upload_or_refresh/0` — handles file still "uploaded" (polls until "processed")
+- `upload_or_refresh/0` — handles OpenAI API errors gracefully (returns `{:error, ...}`)
+- `get_vector_store_id/0` — returns `{:ok, id}` when secret exists
+- `get_vector_store_id/0` — returns `{:error, :not_uploaded}` when secret missing
+- `cleanup_orphaned_files/0` — deletes files not matching known file_id; skips known file
+
+~70 lines.
+
+#### 6c. CollectionChat tests (`test/music_library/chats/collection_chat_test.exs`)
+
+Update existing tests and add new ones:
+- Verify instructions **no longer** contain the per-record catalog lines (the key regression test)
+- Verify instructions **do** contain the aggregated stats string and record count
+- Verify `file_search` tool is included in the API request body when vector store is available (stub `FileStore.get_vector_store_id/0` → `{:ok, "vs_test"}` and assert `tools` array in the JSON body contains `%{"type" => "file_search", "vector_store_ids" => ["vs_test"]}`)
+- Verify `file_search` tool is **not** included when vector store is unavailable (stub → `{:error, :not_uploaded}`, assert tools only has `web_search_preview`)
+- Verify `web_search_preview` is always included regardless of file_search presence
+- Test empty collection edge case (stats = "", record_count = 0)
+- Test SSE event handling: include `response.file_search_call.in_progress`, `response.file_search_call.searching`, and `response.file_search_call.completed` events in the test stream fixture to verify they're silently consumed (caught by the `"response." <> _` catch-all) without breaking the stream
+
+~60 lines (modifications to existing + new tests).
+
+#### 6d. Worker tests (`test/music_library/worker/refresh_collection_file_test.exs`)
+
+- `perform/1` delegates to `FileStore.upload_or_refresh/0` and returns `:ok`
+- `perform/1` returns `{:error, reason}` on failure
+- Unique constraint: inserting two jobs within 300s results in only one executing (test with `Oban.insert/1` returning `{:ok, _}` for first and `{:ok, %{conflict?: true}}` for second)
+
+~20 lines.
+
+#### 6e. Records context integration tests
+
+In existing `test/music_library/records_test.exs` (or equivalent):
+- `create_record/1` enqueues `RefreshCollectionFile` worker
+- `update_record/2` enqueues `RefreshCollectionFile` worker
+- `delete_record/1` enqueues `RefreshCollectionFile` worker
+- Verify with `assert_enqueued` (Oban testing helper)
+
+~15 lines.
+
+#### 6f. LiveView test
+
+In `test/music_library_web/live/collection_live/index_test.exs` (or equivalent):
+- Verify `@collection_stats` is set after mount (not `@collection_summary`)
+- Verify Chat component receives `{stats_string, count}` tuple as `chat_context`
+
+~8 lines (modifications to existing test).
+
+#### 6g. Collection context tests
+
+In existing `test/music_library/collection_test.exs` (or equivalent):
+- `stats_summary/0` returns stats string with genre/format/era breakdowns and correct group count
+- `stats_summary/0` returns `{"", 0}` for empty collection
+- `count_records/0` returns correct count
+- Existing `collection_summary/0` tests continue to pass unchanged
+
+~20 lines.
+
+Estimated total: ~510 lines across 13-15 files. Risk: low/medium — the core streaming infrastructure (`decode_responses_event/2`, Chat component `do_send_message/2`, SSE event loop) is untouched. New code is additive (API endpoints, Oban worker, FileStore module) and follows existing patterns.
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 ## Definition of Done