feat: store matching metadata on session file registration

Each saved file now records three additional fields:
  matched_identifier    — the literal animal_id_string or animal_name
                          substring that matched in the filename
  animal_id_string_snap — snapshot of animal.animal_id_string at
                          registration time
  animal_name_snap      — snapshot of animal.animal_name at
                          registration time

This lets future consumers (scripts, exports, re-matching) identify
the subject from the file record alone, even if animal data changes.
The matched identifier is also shown in the drop preview UI (↳ 2852).

Tests: 25 total (+2 for new payload fields).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/prisma/migrations/20250423010000_session_files_matching_metadata/migration.sql

@@ -0,0 +1,4 @@
+ALTER TABLE "session_files"
+    ADD COLUMN "matched_identifier"    TEXT,
+    ADD COLUMN "animal_id_string_snap" TEXT,
+    ADD COLUMN "animal_name_snap"      TEXT;

backend/prisma/schema.prisma

@@ -56,6 +56,9 @@ model SessionFile {
   file_size             BigInt
   file_type             String?
   last_modified         BigInt?
+  matched_identifier    String?     // the animal ID/name substring that matched in the filename
+  animal_id_string_snap String?     // snapshot of animal.animal_id_string at registration time
+  animal_name_snap      String?     // snapshot of animal.animal_name at registration time
   notes                 String?
   created_at            DateTime    @default(now())
 

backend/src/routes/sessionFiles.js

@@ -2,7 +2,8 @@ const router = require('express').Router();
 const prisma = require('../lib/prisma');
 
 // POST /api/daily-statuses/:id/files  — register file metadata (batch)
-// Body: [{ filename, file_size, file_type, last_modified, notes }, ...]
+// Body: [{ filename, file_size, file_type, last_modified,
+//          matched_identifier, animal_id_string_snap, animal_name_snap, notes }, ...]
 router.post('/daily-statuses/:id/files', async (req, res, next) => {
   try {
     const status = await prisma.dailyStatus.findUnique({ where: { id: req.params.id } });
@@ -31,6 +32,9 @@ router.post('/daily-statuses/:id/files', async (req, res, next) => {
             file_size:             BigInt(Math.round(f.file_size)),
             file_type:             f.file_type             ?? null,
             last_modified:         f.last_modified != null ? BigInt(Math.round(f.last_modified)) : null,
+            matched_identifier:    f.matched_identifier    ?? null,
+            animal_id_string_snap: f.animal_id_string_snap ?? null,
+            animal_name_snap:      f.animal_name_snap      ?? null,
             notes:                 f.notes                 ?? null,
           },
         })

frontend/src/components/FileDropZone.jsx

@@ -48,29 +48,58 @@ function fmtBytes(n) {
   return `${num} B`;
 }
 
-/** Match an array of File objects against animals. Returns { matched: Map<animalId, File[]>, unmatched: File[] } */
+/**
+ * Match an array of File objects against animals.
+ * Returns {
+ *   matched:   Map<animalId, Array<{ file, matchedIdentifier }>>
+ *   unmatched: File[]
+ * }
+ * matchedIdentifier is the animal_id_string or animal_name value that triggered the match.
+ */
 function matchFilesToAnimals(files, animals) {
-  const patterns = animals.map((a) => ({ animal: a, re: buildAnimalRegex(a) })).filter((x) => x.re);
+  // Build patterns; each entry carries both alternatives so we know which one matched.
+  const entries = animals
+    .map((animal) => {
+      const alts = [];
+      if (animal.animal_id_string) alts.push({ value: animal.animal_id_string, re: new RegExp(`(?<![a-zA-Z0-9])${escapeRegex(animal.animal_id_string)}(?![a-zA-Z0-9])`, 'i') });
+      if (animal.animal_name) {
+        const words = animal.animal_name.trim().split(/\s+/).map(escapeRegex);
+        const pat   = words.length === 1 ? words[0] : words.join('[\\s_\\-]+');
+        alts.push({ value: animal.animal_name, re: new RegExp(`(?<![a-zA-Z0-9])${pat}(?![a-zA-Z0-9])`, 'i') });
+      }
+      return { animal, alts };
+    })
+    .filter((e) => e.alts.length > 0);
+
   const matched  = new Map(animals.map((a) => [a.id, []]));
   const unmatched = [];
 
   for (const file of files) {
-    const hit = patterns.find(({ re }) => re.test(file.name));
+    let found = false;
-    if (hit) {
+    for (const { animal, alts } of entries) {
-      matched.get(hit.animal.id).push(file);
+      for (const { value, re } of alts) {
-    } else {
+        if (re.test(file.name)) {
-      unmatched.push(file);
+          matched.get(animal.id).push({ file, matchedIdentifier: value });
+          found = true;
+          break;
         }
       }
+      if (found) break;
+    }
+    if (!found) unmatched.push(file);
+  }
   return { matched, unmatched };
 }
 
 // ── Sub-components ────────────────────────────────────────────────────────────
 
-function FileRow({ file, onRemove }) {
+function FileRow({ file, matchedIdentifier, onRemove }) {
   return (
     <div className="flex items-center justify-between py-1 gap-2 text-xs">
       <span className="font-mono text-gray-700 truncate min-w-0 flex-1">{file.name}</span>
+      {matchedIdentifier && (
+        <span className="text-blue-400 shrink-0 font-mono" title="matched by">↳ {matchedIdentifier}</span>
+      )}
       <span className="text-gray-400 shrink-0">{fmtBytes(file.size)}</span>
       <span className="text-gray-400 shrink-0 w-12 text-right">{classifyFile(file.name)}</span>
       {onRemove && (
@@ -185,13 +214,16 @@ export default function FileDropZone({ rows, date }) {
     try {
       const results = await Promise.all(
         statusRows.map(async ({ animal, status }) => {
-          const files = dropped.matched.get(animal.id) ?? [];
+          const entries = dropped.matched.get(animal.id) ?? [];
-          if (files.length === 0) return { statusId: status.id, saved: [] };
+          if (entries.length === 0) return { statusId: status.id, saved: [] };
-          const payload = files.map((f) => ({
+          const payload = entries.map(({ file, matchedIdentifier }) => ({
-            filename:      f.name,
+            filename:              file.name,
-            file_size:     f.size,
+            file_size:             file.size,
-            file_type:     classifyFile(f.name),
+            file_type:             classifyFile(file.name),
-            last_modified: f.lastModified ?? null,
+            last_modified:         file.lastModified ?? null,
+            matched_identifier:    matchedIdentifier,
+            animal_id_string_snap: animal.animal_id_string ?? null,
+            animal_name_snap:      animal.animal_name      ?? null,
           }));
           const saved = await sessionFilesApi.create(status.id, payload);
           return { statusId: status.id, saved };
@@ -231,7 +263,7 @@ export default function FileDropZone({ rows, date }) {
 
   // ── Derived counts ─────────────────────────────────────────────────────────
 
-  const totalDropped       = dropped ? [...dropped.matched.values()].reduce((n, a) => n + a.length, 0) : 0;
+  const totalDropped       = dropped ? [...dropped.matched.values()].reduce((n, a) => n + a.length, 0) : 0;  // entries are { file, matchedIdentifier }
   const totalUnmatched     = dropped?.unmatched.length ?? 0;
   const totalSaved         = Object.values(savedByStatus).reduce((n, a) => n + a.length, 0);
   const hasSaved           = totalSaved > 0;
@@ -281,8 +313,8 @@ export default function FileDropZone({ rows, date }) {
 
           {/* Per-subject matched files */}
           {statusRows.map(({ animal, status }) => {
-            const files = dropped.matched.get(animal.id) ?? [];
+            const entries = dropped.matched.get(animal.id) ?? [];
-            if (files.length === 0) return null;
+            if (entries.length === 0) return null;
             return (
               <div key={animal.id} className="bg-white border border-gray-200 rounded-xl p-4">
                 <div className="flex items-center justify-between mb-2">
@@ -292,11 +324,11 @@ export default function FileDropZone({ rows, date }) {
                       <span className="ml-1.5 text-xs font-normal text-gray-400">{animal.animal_id_string}</span>
                     )}
                   </span>
-                  <span className="text-xs text-gray-400">{files.length} file{files.length !== 1 ? 's' : ''}</span>
+                  <span className="text-xs text-gray-400">{entries.length} file{entries.length !== 1 ? 's' : ''}</span>
                 </div>
                 <div className="divide-y divide-gray-50">
-                  {files.map((f, i) => (
+                  {entries.map(({ file, matchedIdentifier }, i) => (
-                    <FileRow key={f.name + i} file={f} onRemove={() => removeMatchedFile(animal.id, i)} />
+                    <FileRow key={file.name + i} file={file} matchedIdentifier={matchedIdentifier} onRemove={() => removeMatchedFile(animal.id, i)} />
                   ))}
                 </div>
               </div>

frontend/tests/FileDropZone.test.jsx

@@ -249,8 +249,8 @@ describe('remove files before saving', () => {
 // ── Saving ─────────────────────────────────────────────────────────────────────
 
 describe('saving metadata', () => {
-  it('calls sessionFilesApi.create with correct payload for each subject', async () => {
+  it('calls sessionFilesApi.create with correct payload including matching metadata', async () => {
-    const file = makeFile(`${DATE}_2852_trials.csv`); // size = 1 byte (content 'x')
+    const file = makeFile(`${DATE}_2852_trials.csv`);
     const savedFile = makeSavedFile('f1', 's-a1', file.name, String(file.size));
     sessionFilesApi.create.mockResolvedValue([savedFile]);
 
@@ -267,6 +267,31 @@ describe('saving metadata', () => {
             filename:              `${DATE}_2852_trials.csv`,
             file_size:             file.size,
             file_type:             'CSV',
+            matched_identifier:    '2852',
+            animal_id_string_snap: '2852',
+            animal_name_snap:      'Rat 2852',
+          }),
+        ])
+      )
+    );
+  });
+
+  it('sets matched_identifier to animal_name when file matched by name', async () => {
+    const animal = { id: 'b1', animal_name: 'Rat A', animal_id_string: null };
+    const row    = { animal, status: { id: 's-b1', animal_id: 'b1', date: `${DATE}T00:00:00.000Z` } };
+    sessionFilesApi.create.mockResolvedValue([]);
+    render(<FileDropZone rows={[row]} date={DATE} />);
+    dropFiles([makeFile(`${DATE}_Rat_A_trials.csv`)]);
+    await waitFor(() => screen.getByTestId('save-btn'));
+    fireEvent.click(screen.getByTestId('save-btn'));
+    await waitFor(() =>
+      expect(sessionFilesApi.create).toHaveBeenCalledWith(
+        's-b1',
+        expect.arrayContaining([
+          expect.objectContaining({
+            matched_identifier:    'Rat A',
+            animal_id_string_snap: null,
+            animal_name_snap:      'Rat A',
           }),
         ])
       )