diff --git a/src/chrome/src/agent/tools.js b/src/chrome/src/agent/tools.js
index 89f88ec8e..9ebc3d767 100644
--- a/src/chrome/src/agent/tools.js
+++ b/src/chrome/src/agent/tools.js
@@ -1266,6 +1266,25 @@ const WATCH_BEEP_TOOL = {
   },
 };
 
+function compactUploadFileTool(tool) {
+  return {
+    ...tool,
+    function: {
+      ...tool.function,
+      description: 'Attach a user-provided file directly to an existing file input without clicking the page upload control. Use attachmentId from the current user-attachment notice, or an absolute filePath the user supplied. This proves only local page attachment, not remote upload or submission. Use the exact selector for the intended input; never guess a generic input[type="file"] selector when multiple inputs exist. If the widget creates its input lazily, make one guarded click on its add-files control, then retry upload_file with the exact selector.',
+      parameters: {
+        type: 'object',
+        properties: {
+          selector: { type: 'string', description: 'Exact CSS selector for the intended file input.' },
+          attachmentId: { type: 'string', description: 'Opaque id from the current user-attachment notice. Never guess an id.' },
+          filePath: { type: 'string', description: 'Absolute local path explicitly supplied by the user. Optional when attachmentId is given.' },
+        },
+        required: ['selector'],
+      },
+    },
+  };
+}
+
 /**
  * Get tools filtered by mode.
  *
@@ -1285,7 +1304,9 @@ export function getToolsForMode(mode, opts = {}) {
   } else if (devCompactBlocked) {
     base = [];
   } else if (tier === 'compact') {
-    base = AGENT_TOOLS.filter(t => COMPACT_TOOL_NAMES.has(t.function.name));
+    base = AGENT_TOOLS
+      .filter(t => COMPACT_TOOL_NAMES.has(t.function.name))
+      .map(t => (t.function.name === 'upload_file' ? compactUploadFileTool(t) : t));
   } else if (tier === 'mid') {
     base = AGENT_TOOLS.filter(t => MID_TOOL_NAMES.has(t.function.name));
   } else {
@@ -1702,6 +1723,7 @@ export const COMPACT_TOOL_NAMES = new Set([
   'click', 'type_text', 'press_keys',
   'navigate', 'new_tab', 'wait_for_element',
   'fetch_url',
+  'upload_file',
   'scratchpad_write', 'progress_update', 'progress_read', 'clarify', 'done',
 ]);
 
@@ -1747,6 +1769,7 @@ TOOLS — use ONLY these:
 - new_tab({url}): Open a URL in a background tab for user reference. It does not activate or retarget the current run, so never use it as a site-permission workaround.
 - wait_for_element({selector}): Wait for an element to appear.
 - fetch_url({url}): Fetch a URL for its content.
+- upload_file({selector, attachmentId|filePath}): Attach a user-provided file directly to an existing file input; do not click the page upload control first. Use the exact selector and never guess generic input[type="file"] when multiple inputs exist. If the widget creates its input lazily, make one guarded initializer click, re-read the page, then retry with the exact selector. Verify the page shows the attachment before submitting.
 - scratchpad_write({text}): Save notes that persist across steps.
 - progress_update({items}) / progress_read({status}): Structured progress ledger for the active repeated item/action task. On GitHub stargazers, only "Follow USER" buttons are follow targets when following is allowed by the task; "Unfollow USER" means skip/already followed unless the ledger shows acted.
 - done({summary, outcome}): Signal success, partial progress, or a failed blocker.
diff --git a/src/firefox/src/agent/tools.js b/src/firefox/src/agent/tools.js
index 966bb4942..8d4eeffaa 100644
--- a/src/firefox/src/agent/tools.js
+++ b/src/firefox/src/agent/tools.js
@@ -993,6 +993,7 @@ export const COMPACT_TOOL_NAMES = new Set([
   'click', 'type_text', 'press_keys',
   'navigate', 'new_tab', 'wait_for_element',
   'fetch_url',
+  'upload_file',
   'scratchpad_write', 'progress_update', 'progress_read', 'clarify', 'done',
 ]);
 
@@ -1114,6 +1115,24 @@ const WATCH_BEEP_TOOL = {
   },
 };
 
+function compactUploadFileTool(tool) {
+  return {
+    ...tool,
+    function: {
+      ...tool.function,
+      description: 'Attach a user-provided file directly to an existing file input without clicking the page upload control. Use attachmentId from the current user-attachment notice, or omit it to open WebBrain\'s file picker. This proves only local page attachment, not remote upload or submission. Use the exact selector for the intended input; never guess a generic input[type="file"] selector when multiple inputs exist. If the widget creates its input lazily, make one guarded click on its add-files control, then retry upload_file with the exact selector.',
+      parameters: {
+        type: 'object',
+        properties: {
+          selector: { type: 'string', description: 'Exact CSS selector for the intended file input.' },
+          attachmentId: { type: 'string', description: 'Opaque id from the current user-attachment notice. Omit only to ask the user through WebBrain\'s file picker; never guess an id.' },
+        },
+        required: ['selector'],
+      },
+    },
+  };
+}
+
 /**
  * Get tools filtered by mode.
  *
@@ -1132,7 +1151,9 @@ export function getToolsForMode(mode, opts = {}) {
   } else if (devCompactBlocked) {
     base = [];
   } else if (tier === 'compact') {
-    base = AGENT_TOOLS.filter(t => COMPACT_TOOL_NAMES.has(t.function.name));
+    base = AGENT_TOOLS
+      .filter(t => COMPACT_TOOL_NAMES.has(t.function.name))
+      .map(t => (t.function.name === 'upload_file' ? compactUploadFileTool(t) : t));
   } else if (tier === 'mid') {
     base = AGENT_TOOLS.filter(t => MID_TOOL_NAMES.has(t.function.name));
   } else {
@@ -1230,6 +1251,7 @@ TOOLS - use only these:
 - new_tab({url}): Open a URL in a background tab for user reference. It does not activate or retarget the current run, so never use it as a site-permission workaround.
 - wait_for_element({selector}): Wait for an element to appear.
 - fetch_url({url}): Fetch other URLs for reading only; do not use it to re-read the active tab.
+- upload_file({selector, attachmentId?}): Attach a user-provided file directly to an existing file input; do not click the page upload control first. Use the current attachmentId or omit it for WebBrain's picker. Use the exact selector and never guess generic input[type="file"] when multiple inputs exist. If the widget creates its input lazily, make one guarded initializer click, re-read the page, then retry with the exact selector. Verify the page shows the attachment before submitting.
 - scratchpad_write({text}): Save notes that persist across steps.
 - progress_update({items}) / progress_read({status}): Structured progress ledger for the active repeated item/action task. On GitHub stargazers, only "Follow USER" buttons are follow targets when following is allowed by the task; "Unfollow USER" means skip/already followed unless the ledger shows acted.
 - clarify({question, options?}): Ask the user only when materially blocked or ambiguous. Unanswered clarifies auto-select options[0] after timeout (source=timeout is not user approval for high-risk steps; source=auto Instant is intentional auto-approve).
diff --git a/test/run.js b/test/run.js
index 8c24ea4a2..00c1c93e6 100644
--- a/test/run.js
+++ b/test/run.js
@@ -12785,6 +12785,7 @@ test('getToolsForMode: compact mode restricts act tools in both browsers', () =>
       [...compactNames].sort(),
     );
     assert.ok(compactNamesActual.includes('done'), `[${label}] compact mode must keep done`);
+    assert.ok(compactNamesActual.includes('upload_file'), `[${label}] compact mode must expose upload_file`);
     for (const excluded of ['resize_window', 'download_social_media', 'solve_captcha']) {
       assert.equal(compactNamesActual.includes(excluded), false, `[${label}] compact mode must omit ${excluded}`);
     }
@@ -12792,6 +12793,49 @@ test('getToolsForMode: compact mode restricts act tools in both browsers', () =>
   }
 });
 
+test('compact Act exposes a direct-upload-only file workflow in both browsers', () => {
+  for (const [label, getTools, prompt] of [
+    ['chrome', getToolsForModeCh, SYSTEM_PROMPT_ACT_COMPACT_CH],
+    ['firefox', getToolsForModeFx, SYSTEM_PROMPT_ACT_COMPACT_FX],
+  ]) {
+    const askNames = getTools('ask').map(tool => tool.function.name);
+    const compactTools = getTools('act', { tier: 'compact' });
+    const compactNames = compactTools.map(tool => tool.function.name);
+    const upload = compactTools.find(tool => tool.function.name === 'upload_file');
+    const fullUpload = getTools('act').find(tool => tool.function.name === 'upload_file');
+
+    assert.ok(upload, `[${label}] compact Act must expose upload_file`);
+    assert.equal(askNames.includes('upload_file'), false, `[${label}] Ask must remain read-only`);
+    for (const unavailable of [
+      'download_files',
+      'download_resource_from_page',
+      'list_downloads',
+      'read_downloaded_file',
+    ]) {
+      assert.equal(compactNames.includes(unavailable), false, `[${label}] compact Act exposed ${unavailable}`);
+    }
+    assert.match(upload.function.description, /directly to an existing file input/i);
+    assert.match(upload.function.description, /without clicking the page upload control/i);
+    assert.match(upload.function.description, /exact selector/i);
+    assert.match(upload.function.description, /one guarded click/i);
+    assert.doesNotMatch(upload.function.description, /download_files|list_downloads|downloadId/i);
+    assert.ok(upload.function.parameters.properties.attachmentId, `[${label}] compact upload must accept attachmentId`);
+    assert.equal(upload.function.parameters.properties.downloadId, undefined, `[${label}] compact upload must hide downloadId`);
+    assert.ok(fullUpload.function.parameters.properties.downloadId, `[${label}] full upload must retain downloadId`);
+    assert.match(prompt, /upload_file[\s\S]{0,180}do not click the page upload control/i);
+    assert.match(prompt, /upload_file[\s\S]{0,360}exact selector/i);
+    assert.match(prompt, /upload_file[\s\S]{0,420}one guarded initializer click/i);
+    assert.doesNotMatch(prompt, /download_files|list_downloads|downloadId/i);
+
+    if (label === 'chrome') {
+      assert.ok(upload.function.parameters.properties.filePath, 'chrome: compact upload must accept a user-supplied filePath');
+    } else {
+      assert.equal(upload.function.parameters.properties.filePath, undefined, 'firefox: compact upload must not invent filePath support');
+      assert.match(upload.function.description, /WebBrain's file picker/i);
+    }
+  }
+});
+
 test('getToolsForMode: mode/tier redesign exposes the intended normal and Dev tools', () => {
   for (const [label, getTools] of [
     ['chrome', getToolsForModeCh],
@@ -50221,7 +50265,7 @@ test('user attachment upload guidance follows the active tier tool catalog', ()
     ]);
 
     for (const [mode, tier, shouldAdvertiseUpload] of [
-      ['act', 'compact', false],
+      ['act', 'compact', true],
       ['act', 'mid', true],
       ['act', 'full', true],
       ['ask', 'full', false],