diff --git a/src/chrome/src/agent/agent.js b/src/chrome/src/agent/agent.js
index 5ceefe2d2..e76d32572 100644
--- a/src/chrome/src/agent/agent.js
+++ b/src/chrome/src/agent/agent.js
@@ -16631,7 +16631,13 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
       // small integer id (returned by download_files/list_downloads and
       // auto-pinned to the scratchpad) is easy to carry. Resolve it to the real
       // path here so the rest of the handler is unchanged. If both are present,
-      // downloadId wins: filePath may be stale or invented.
+      // prefer a valid downloadId because filePath may be stale or invented, but
+      // keep the supplied path as a fallback. Models occasionally add a guessed
+      // id to an otherwise valid absolute path; that extra bad id must not make
+      // the path-based upload fail.
+      const suppliedFilePath = typeof args.filePath === 'string' && args.filePath.trim()
+        ? args.filePath
+        : null;
       if (args.downloadId != null) {
         try {
           const items = await new Promise((resolve, reject) => {
@@ -16641,12 +16647,17 @@ Rules: no prose intro, no conclusion, no "this screenshot shows...", no layout d
             });
           });
           const it = items && items[0];
-          if (!it) return { success: false, error: `No download found for downloadId ${args.downloadId}. Use list_downloads to see valid ids.` };
-          if (it.state !== 'complete') return { success: false, error: `Download ${args.downloadId} is "${it.state}", not complete — wait for it to finish (wait_for_stable) then retry.` };
-          if (!it.filename) return { success: false, error: `Download ${args.downloadId} has no resolved local path yet. Retry shortly, or use list_downloads to find the path and pass filePath.` };
-          args.filePath = it.filename;
+          if (!it) {
+            if (!suppliedFilePath) return { success: false, error: `No download found for downloadId ${args.downloadId}. Use list_downloads to see valid ids.` };
+          } else if (it.state !== 'complete') {
+            if (!suppliedFilePath) return { success: false, error: `Download ${args.downloadId} is "${it.state}", not complete — wait for it to finish (wait_for_stable) then retry.` };
+          } else if (!it.filename) {
+            if (!suppliedFilePath) return { success: false, error: `Download ${args.downloadId} has no resolved local path yet. Retry shortly, or use list_downloads to find the path and pass filePath.` };
+          } else {
+            args.filePath = it.filename;
+          }
         } catch (e) {
-          return { success: false, error: `Could not resolve downloadId ${args.downloadId}: ${e.message}` };
+          if (!suppliedFilePath) return { success: false, error: `Could not resolve downloadId ${args.downloadId}: ${e.message}` };
         }
       }
       if (!args.filePath) {
diff --git a/src/chrome/src/agent/tools.js b/src/chrome/src/agent/tools.js
index 94fb26a5b..f5ccde587 100644
--- a/src/chrome/src/agent/tools.js
+++ b/src/chrome/src/agent/tools.js
@@ -923,7 +923,7 @@ export const AGENT_TOOLS = [
     type: 'function',
     function: {
       name: 'upload_file',
-      description: 'Upload a file directly to an existing file input without opening the page or OS file-picker dialog. Do NOT click "Choose file", "Select a file", an upload drop zone, or the input first when the input already exists. Provide EITHER downloadId (preferred — the id from download_files/list_downloads; you do not need to recall the path) OR filePath (absolute local path). If no file input exists because the widget creates it lazily, one guarded click on its add-files control may initialize the widget; then retry upload_file with the exact selector returned or discovered. The file must exist on the local filesystem.',
+      description: 'Upload a file directly to an existing file input without opening the page or OS file-picker dialog. Do NOT click "Choose file", "Select a file", an upload drop zone, or the input first when the input already exists. Provide EITHER downloadId (preferred — the id from download_files/list_downloads; you do not need to recall the path) OR filePath (absolute local path). Never guess a downloadId. If both are accidentally provided, a valid downloadId is preferred; if that id cannot resolve, the supplied filePath is used as a fallback. If no file input exists because the widget creates it lazily, one guarded click on its add-files control may initialize the widget; then retry upload_file with the exact selector returned or discovered. The file must exist on the local filesystem.',
       parameters: {
         type: 'object',
         properties: {
diff --git a/test/run.js b/test/run.js
index 2df2aff08..fc08d710f 100644
--- a/test/run.js
+++ b/test/run.js
@@ -49900,7 +49900,7 @@ test('Chrome click paths suppress native file choosers and redirect to upload_fi
   }
 });
 
-test('upload_file prefers downloadId over a supplied stale filePath (chrome)', async () => {
+test('upload_file prefers a valid downloadId and falls back to filePath for an invalid id (chrome)', async () => {
   const originalChrome = globalThis.chrome;
   const originalCdp = {
     attach: cdpClientCh.attach,
@@ -49912,18 +49912,21 @@ test('upload_file prefers downloadId over a supplied stale filePath (chrome)', a
   };
   const realPath = '/Users/x/Downloads/real.zip';
   const stalePath = '/Users/Shared/made-up.zip';
+  const exactPath = '/root/Downloads/github-avatar-carloslopez.jpg';
   const uploaded = [];
   const releasedGroups = [];
   let queryCount = 0;
   let selectorMatches = ['input-501'];
+  let expectedPath = realPath;
 
   try {
     globalThis.chrome = {
       runtime: { lastError: null },
       downloads: {
         search(query, cb) {
-          assert.deepEqual(query, { id: 9123 });
-          cb([{ id: 9123, state: 'complete', filename: realPath }]);
+          if (query.id === 9123) cb([{ id: 9123, state: 'complete', filename: realPath }]);
+          else if (query.id === 0) cb([]);
+          else assert.fail(`unexpected download id ${query.id}`);
         },
       },
     };
@@ -49936,14 +49939,14 @@ test('upload_file prefers downloadId over a supplied stale filePath (chrome)', a
       releasedGroups.push(objectGroup);
     };
     cdpClientCh.probeLocalFile = async (_tabId, filePath) => {
-      assert.equal(filePath, realPath, 'downloadId-resolved path should override stale filePath before probing');
+      assert.equal(filePath, expectedPath);
       return { exists: true, readable: true, size: 123 };
     };
     cdpClientCh.setFileInputFiles = async (_tabId, objectId, files) => {
       assert.equal(objectId, 'input-501');
       uploaded.push(files);
     };
-    cdpClientCh.getFileInputFiles = async () => [{ name: 'real.zip', size: 123, readable: true }];
+    cdpClientCh.getFileInputFiles = async () => [{ name: expectedPath.split('/').pop(), size: 123, readable: true }];
 
     const agent = new AgentCh({});
     const args = { selector: 'input[type=file]', downloadId: 9123, filePath: stalePath };
@@ -49955,6 +49958,15 @@ test('upload_file prefers downloadId over a supplied stale filePath (chrome)', a
     assert.deepEqual(uploaded, [[realPath]]);
     assert.deepEqual(releasedGroups, ['upload-query-1'], 'successful uploads must release selector handles');
 
+    expectedPath = exactPath;
+    const fallbackArgs = { selector: 'input[type=file]', downloadId: 0, filePath: exactPath };
+    const fallback = await agent.executeTool(42, 'upload_file', fallbackArgs);
+    assert.equal(fallback.success, true);
+    assert.equal(fallback.file, exactPath);
+    assert.equal(fallbackArgs.filePath, exactPath, 'an unresolved downloadId must not replace a supplied absolute path');
+    assert.deepEqual(uploaded, [[realPath], [exactPath]]);
+
+    expectedPath = realPath;
     selectorMatches = ['input-501', 'input-502'];
     const ambiguous = await agent.executeTool(42, 'upload_file', {
       selector: 'input[type=file]',
@@ -49963,10 +49975,10 @@ test('upload_file prefers downloadId over a supplied stale filePath (chrome)', a
     assert.equal(ambiguous.success, false);
     assert.match(ambiguous.error, /matched 2 elements/);
     assert.match(ambiguous.error, /exact, unique selector/);
-    assert.deepEqual(uploaded, [[realPath]], 'ambiguous selectors must fail before attaching the file');
+    assert.deepEqual(uploaded, [[realPath], [exactPath]], 'ambiguous selectors must fail before attaching the file');
     assert.deepEqual(
       releasedGroups,
-      ['upload-query-1', 'upload-query-2'],
+      ['upload-query-1', 'upload-query-2', 'upload-query-3'],
       'early upload failures must release selector handles',
     );
   } finally {