diff --git a/cli/__tests__/adapters.claude.environment.test.mjs b/cli/__tests__/adapters.claude.environment.test.mjs
index cb4fdae817..d84b81816f 100644
--- a/cli/__tests__/adapters.claude.environment.test.mjs
+++ b/cli/__tests__/adapters.claude.environment.test.mjs
@@ -423,6 +423,9 @@ describe('claude adapter — ctx.environment', () => {
       expect(call.args).toContain('Read(./**)');
       expect(call.args).toContain('mcp__capture__*');
       expect(call.args).toContain('Bash');
+      // TASK-287: a public seat is not offered attach_file.
+      expect(call.args.slice(call.args.indexOf('--disallowedTools')))
+        .toContain('mcp__capture__commonly_attach_file');
       expect(call.opts.env.HOME).toBe(publicState);
       expect(call.opts.env.TMPDIR).toBe(path.join(publicState, 'tmp'));
       // Without it Claude creates /tmp/claude-<uid>, which the profile denies.
@@ -1272,6 +1275,8 @@ describe('claude adapter — a workspace seat', () => {
       'Read(./.git/**)', 'Read(./**/.git/**)',
       'mcp__commonly__commonly_self_install_into_pod',
     ]));
+    // Workspace seats follow the same list as public ones (TASK-287).
+    expect(denied).toContain('mcp__commonly__commonly_attach_file');
     expect(opts.env.HOME).toBe(publicState);
     expect(opts.env.COMMONLY_HOST_SECRET).toBeUndefined();
   });
diff --git a/cli/__tests__/adapters.codex.test.mjs b/cli/__tests__/adapters.codex.test.mjs
index b01242b459..bc92819af4 100644
--- a/cli/__tests__/adapters.codex.test.mjs
+++ b/cli/__tests__/adapters.codex.test.mjs
@@ -429,6 +429,9 @@ describe('codex adapter — spawn()', () => {
       });
       const args = calls[0].args;
       expect(args).toContain('mcp_servers.commonly.command="node"');
+      // TASK-287: a public seat is never offered attach_file. (The private
+      // spawn's exact -c list above proves the private seat keeps it.)
+      expect(args).toContain('mcp_servers.commonly.disabled_tools=["commonly_attach_file"]');
       const permissionConfig = args.find((arg) => arg.startsWith('permissions.commonly_public.filesystem='));
       expect(permissionConfig).toContain(`${JSON.stringify(versionDir)}="read"`);
       expect(permissionConfig).not.toContain(`${JSON.stringify(home)}="read"`);
diff --git a/cli/__tests__/adapters.opencode.test.mjs b/cli/__tests__/adapters.opencode.test.mjs
index 7d53981704..55c37b6e84 100644
--- a/cli/__tests__/adapters.opencode.test.mjs
+++ b/cli/__tests__/adapters.opencode.test.mjs
@@ -231,6 +231,10 @@ describe('opencode MCP config', () => {
     expect(permission.external_directory).toBe('deny');
     expect(permission['commonly_*']).toBe('allow');
     expect(permission['room_grants_*']).toBe('allow');
+    // TASK-287: attach_file is denied after the wildcard allow, so the deny wins.
+    const keys = Object.keys(permission);
+    expect(permission.commonly_commonly_attach_file).toBe('deny');
+    expect(keys.indexOf('commonly_commonly_attach_file')).toBeGreaterThan(keys.indexOf('commonly_*'));
     expect(permission.edit['*']).toBe('allow');
     expect(permission.edit['**/.npmrc']).toBe('deny');
     expect(permission.edit['**/.yarnrc*']).toBe('deny');
diff --git a/cli/__tests__/adapters.qwen.test.mjs b/cli/__tests__/adapters.qwen.test.mjs
index 1eee76b116..92cfb2f402 100644
--- a/cli/__tests__/adapters.qwen.test.mjs
+++ b/cli/__tests__/adapters.qwen.test.mjs
@@ -103,6 +103,7 @@ test('public launch isolates HOME and config, strips shadows, and never serializ
     expect(args[args.indexOf('--exclude-tools') + 1].split(','))
       .toEqual(expect.arrayContaining([
         'agent', 'workflow', 'advisor', 'replace', 'task', 'search_file_content',
+        'commonly_attach_file', 'mcp__commonly__commonly_attach_file',
       ]));
     expect(options.env.HOME).toBe(options.env.QWEN_HOME);
     expect(options.env.HOME).toContain('commonly-qwen-home-');
diff --git a/cli/src/lib/adapters/claude.js b/cli/src/lib/adapters/claude.js
index a793bffec3..57ad9649a2 100644
--- a/cli/src/lib/adapters/claude.js
+++ b/cli/src/lib/adapters/claude.js
@@ -96,6 +96,7 @@ import { buildMemoryPreamble, ROW_SLICING_CUE } from '../memory-bridge.js';
 import { claudeConfigDirFor, claudeContextTokens, claudeTranscriptPath } from '../session-recycle.js';
 import { skillsAsText } from '../skill-prompt.js';
 import { adapterFailure, spawnCredentials } from '../upstream-refusal.js';
+import { PUBLIC_WITHHELD_TOOLS } from '../public-withheld-tools.js';
 
 // See codex.js for the rationale on bumping the default + env override.
 // Keeping both adapters in lockstep so any wrapper agent runtime has the
@@ -446,6 +447,10 @@ const buildPublicClaudePolicyArgs = (mcpToolPatterns, { trust, allow = [], memor
   const memoryDenies = memoryWithheld
     ? MEMORY_TOOLS.flatMap((tool) => mcpToolPatterns.map((pattern) => pattern.replace(/\*$/, tool)))
     : [];
+  // Nor, on any confined trust, the tools no public seat is offered
+  // (public-withheld-tools.js).
+  const withheldDenies = PUBLIC_WITHHELD_TOOLS
+    .flatMap((tool) => mcpToolPatterns.map((pattern) => pattern.replace(/\*$/, tool)));
   return [
     // HOME points at an isolated, sanitized state directory. Ignore settings
     // from user/project/local sources and disable slash-command extensions;
@@ -457,7 +462,7 @@ const buildPublicClaudePolicyArgs = (mcpToolPatterns, { trust, allow = [], memor
     '--permission-mode', 'dontAsk',
     '--allowedTools', 'Read(./**)', ...granted, ...mcpToolPatterns,
     '--disallowedTools', ...PUBLIC_DENIED_TOOLS.filter((tool) => !granted.includes(tool)),
-    ...deniedReads, ...workspaceDenies, ...memoryDenies,
+    ...deniedReads, ...workspaceDenies, ...memoryDenies, ...withheldDenies,
   ];
 };
 
diff --git a/cli/src/lib/adapters/codex.js b/cli/src/lib/adapters/codex.js
index f6fcfc1766..2c422b7c20 100644
--- a/cli/src/lib/adapters/codex.js
+++ b/cli/src/lib/adapters/codex.js
@@ -71,6 +71,7 @@ import { buildMemoryPreamble, ROW_SLICING_CUE } from '../memory-bridge.js';
 import { resolveSkillSource, skillsAsText } from '../skill-prompt.js';
 import { isLegacySandboxTrust, normalizeSandboxTrust, refuseWorkspaceTrust } from '../environment.js';
 import { adapterFailure, spawnCredentials } from '../upstream-refusal.js';
+import { PUBLIC_WITHHELD_TOOLS } from '../public-withheld-tools.js';
 
 // Default timeout for a single codex spawn (exec mode).
 //
@@ -212,6 +213,10 @@ const buildMcpOverrideArgs = (mcpServers, ctx = {}) => {
       '-c',
       `mcp_servers.${server.name}.default_tools_approval_mode="approve"`,
     );
+    // ...except the tools no public seat is offered (public-withheld-tools.js).
+    if (ctx.publicSeat) {
+      flags.push('-c', `mcp_servers.${server.name}.disabled_tools=[${PUBLIC_WITHHELD_TOOLS.map(toml).join(',')}]`);
+    }
     if (rest.length) {
       flags.push('-c', `mcp_servers.${server.name}.args=[${rest.map(toml).join(',')}]`);
     }
diff --git a/cli/src/lib/adapters/opencode.js b/cli/src/lib/adapters/opencode.js
index b7394b425e..62f77c5d15 100644
--- a/cli/src/lib/adapters/opencode.js
+++ b/cli/src/lib/adapters/opencode.js
@@ -58,6 +58,7 @@ import { resolveProviderKeyFile, startProviderProxy } from '../provider-proxy.js
 import { isShippedCommonlyMcpCommand } from '../declared-mcp-guard.js';
 import { isAnswerableToolError } from '../public-tool-error.js';
 import { startInstanceProxy } from '../instance-proxy.js';
+import { PUBLIC_WITHHELD_TOOLS } from '../public-withheld-tools.js';
 
 const DEFAULT_TIMEOUT_MS = 15 * 60 * 1000;
 const ISOLATED_PROXY_PORT = 8765;
@@ -246,6 +247,10 @@ const publicPermissions = (mode, mcpNames) => {
     todoread: 'allow',
     lsp: 'allow',
     ...Object.fromEntries(mcpNames.map((name) => [`${permissionMcpName(name)}_*`, 'allow'])),
+    // After the wildcard allow, since the last matching rule wins
+    // (public-withheld-tools.js).
+    ...Object.fromEntries(mcpNames.flatMap((name) => PUBLIC_WITHHELD_TOOLS
+      .map((tool) => [`${permissionMcpName(name)}_${tool}`, 'deny']))),
   };
 };
 
diff --git a/cli/src/lib/adapters/qwen.js b/cli/src/lib/adapters/qwen.js
index 3713c920e7..09bf955f7f 100644
--- a/cli/src/lib/adapters/qwen.js
+++ b/cli/src/lib/adapters/qwen.js
@@ -15,6 +15,7 @@ import { detectBwrap, wrapArgvWithBwrap } from '../sandbox/bwrap.js';
 import { wrapArgvWithSeatbelt } from '../sandbox/seatbelt.js';
 import { resolveProviderKeyFile, startProviderProxy } from '../provider-proxy.js';
 import { adapterFailure, spawnCredentials } from '../upstream-refusal.js';
+import { PUBLIC_WITHHELD_TOOLS } from '../public-withheld-tools.js';
 
 // Add a version only with a passing real clean-box sandbox smoke that names it.
 const TESTED_QWEN_VERSIONS = Object.freeze(['0.25.1', '0.26.2']);
@@ -38,6 +39,9 @@ const EXCLUDED_TOOLS = [
 // per-spawn MCP credential file, so public turns cannot expose OS read tools.
 const PUBLIC_READ_TOOLS = [
   'read_file', 'grep_search', 'search_file_content', 'glob', 'list_directory', 'lsp',
+  // Both spellings of a Commonly MCP tool, as with the aliases above
+  // (public-withheld-tools.js).
+  ...PUBLIC_WITHHELD_TOOLS.flatMap((tool) => [tool, `mcp__commonly__${tool}`]),
 ];
 
 const parseVersion = (output) => {
diff --git a/cli/src/lib/public-withheld-tools.js b/cli/src/lib/public-withheld-tools.js
new file mode 100644
index 0000000000..6b8cd14236
--- /dev/null
+++ b/cli/src/lib/public-withheld-tools.js
@@ -0,0 +1,5 @@
+// Commonly MCP tools that public seats are not offered, on any adapter.
+// Claude workspace seats follow the same list. Each
+// adapter removes them in its own vocabulary (TASK-287; Goose's public list
+// already leaves them out).
+export const PUBLIC_WITHHELD_TOOLS = Object.freeze(['commonly_attach_file']);
diff --git a/docs/agents/COMMONLY_MCP.md b/docs/agents/COMMONLY_MCP.md
index 31dab1a148..c0766e4738 100644
--- a/docs/agents/COMMONLY_MCP.md
+++ b/docs/agents/COMMONLY_MCP.md
@@ -113,7 +113,7 @@ All tools are namespaced `commonly_*`. Names match the earlier extension surface
 | `commonly_react_to_message` | React to a message with an emoji (dual-auth kernel endpoint) | `messageId`, `emoji` |
 | `commonly_list_files` | List files uploaded into a pod (metadata) | `podId` |
 | `commonly_read_file` | Read a pod file's content (text ≤256KB; binary → metadata + note) | `podId`, `fileName` |
-| `commonly_attach_file` | Upload a local file into a pod + post it as a file card | `podId`, `filePath` |
+| `commonly_attach_file` | Upload a local file into a pod + post it as a file card. Not offered to public seats on any adapter (`cli/src/lib/public-withheld-tools.js`) | `podId`, `filePath` |
 
 GitHub PR tools were removed (they lent a shared server credential to any
 caller). Shell-capable runtimes use `gh pr diff` / `gh pr review`.