diff --git a/src/attachment-magic.ts b/src/attachment-magic.ts
new file mode 100644
index 00000000..f4d6d763
--- /dev/null
+++ b/src/attachment-magic.ts
@@ -0,0 +1,35 @@
+/**
+ * @fileoverview Parses terminal magic links that request attachment cards.
+ */
+
+import { isAbsolute } from 'node:path';
+import { isSupportedAttachmentExtension } from './attachment-registry.js';
+
+const MAGIC_LINK_RE = /codeman:\/\/attach\?([^\s<>"']+)/g;
+
+export function parseAttachmentMagicLinks(data: string): string[] {
+  const results: string[] = [];
+  const seen = new Set<string>();
+
+  for (const match of data.matchAll(MAGIC_LINK_RE)) {
+    const query = trimTrailingPunctuation(match[1] || '');
+    try {
+      const params = new URLSearchParams(query);
+      const filePath = params.get('path');
+      if (!filePath || !isAbsolute(filePath)) continue;
+      const extension = filePath.split('.').pop()?.toLowerCase() || '';
+      if (!isSupportedAttachmentExtension(extension)) continue;
+      if (seen.has(filePath)) continue;
+      seen.add(filePath);
+      results.push(filePath);
+    } catch {
+      // Ignore malformed terminal text. Magic links are advisory.
+    }
+  }
+
+  return results;
+}
+
+function trimTrailingPunctuation(value: string): string {
+  return value.replace(/[),.;:]+$/g, '');
+}
diff --git a/src/attachment-registry.ts b/src/attachment-registry.ts
new file mode 100644
index 00000000..fe7b64cf
--- /dev/null
+++ b/src/attachment-registry.ts
@@ -0,0 +1,216 @@
+/**
+ * @fileoverview In-memory attachment registry for live external document references.
+ *
+ * Session-local files keep using the existing workspace-scoped file routes. This
+ * registry is only for explicit, live external attachments that need a stable ID
+ * so browser requests never contain arbitrary absolute paths.
+ */
+
+import { randomUUID } from 'node:crypto';
+import { realpathSync } from 'node:fs';
+import fs from 'node:fs/promises';
+import { basename, extname, isAbsolute } from 'node:path';
+import { isBlockedAttachmentPath, loadAttachmentGuardConfig } from './config/attachment-guard.js';
+import { validateSessionFilePath } from './web/route-helpers.js';
+import type { AttachmentDetectedEvent, AttachmentDetectedType } from './types.js';
+
+const SUPPORTED_ATTACHMENT_EXTENSIONS = new Set(['png', 'pdf', 'docx', 'pptx', 'md', 'txt']);
+
+export type AttachmentSource = 'detected' | 'external';
+
+export interface AttachmentRecord {
+  attachmentId: string;
+  sessionId: string;
+  filePath: string;
+  fileName: string;
+  extension: string;
+  attachmentType: AttachmentDetectedType;
+  size: number;
+  mtimeMs: number;
+  timestamp: number;
+  source: AttachmentSource;
+}
+
+export interface AttachmentRegistrationResult extends AttachmentDetectedEvent {
+  attachmentId: string;
+  source: AttachmentSource;
+  rawUrl: string;
+  previewUrl: string;
+  thumbnailUrl: string;
+}
+
+export class AttachmentRegistrationError extends Error {
+  constructor(
+    message: string,
+    readonly statusCode: number = 400
+  ) {
+    super(message);
+  }
+}
+
+class AttachmentRegistry {
+  private recordsBySession = new Map<string, Map<string, AttachmentRecord>>();
+
+  register(record: AttachmentRecord): void {
+    let records = this.recordsBySession.get(record.sessionId);
+    if (!records) {
+      records = new Map();
+      this.recordsBySession.set(record.sessionId, records);
+    }
+    records.set(record.attachmentId, record);
+  }
+
+  get(sessionId: string, attachmentId: string): AttachmentRecord | undefined {
+    return this.recordsBySession.get(sessionId)?.get(attachmentId);
+  }
+
+  findByFilePath(sessionId: string, filePath: string): AttachmentRecord | undefined {
+    const records = this.recordsBySession.get(sessionId);
+    if (!records) return undefined;
+    for (const record of records.values()) {
+      if (record.filePath === filePath) return record;
+    }
+    return undefined;
+  }
+
+  clearSession(sessionId: string): void {
+    this.recordsBySession.delete(sessionId);
+  }
+}
+
+export const attachmentRegistry = new AttachmentRegistry();
+
+export function isSupportedAttachmentExtension(extension: string): boolean {
+  return SUPPORTED_ATTACHMENT_EXTENSIONS.has(extension.toLowerCase().replace(/^\./, ''));
+}
+
+export function getAttachmentType(extension: string): AttachmentDetectedType {
+  const normalized = extension.toLowerCase().replace(/^\./, '');
+  if (normalized === 'png') return 'image';
+  if (normalized === 'pdf') return 'pdf';
+  if (normalized === 'pptx') return 'presentation';
+  if (normalized === 'md') return 'markdown';
+  if (normalized === 'txt') return 'text';
+  return 'document';
+}
+
+export function buildAttachmentRoutes(
+  sessionId: string,
+  attachmentId: string
+): {
+  rawUrl: string;
+  previewUrl: string;
+  thumbnailUrl: string;
+} {
+  const encodedId = encodeURIComponent(attachmentId);
+  return {
+    rawUrl: `/api/sessions/${sessionId}/attachments/${encodedId}/raw`,
+    previewUrl: `/api/sessions/${sessionId}/attachments/${encodedId}/preview`,
+    thumbnailUrl: `/api/sessions/${sessionId}/attachments/${encodedId}/thumbnail`,
+  };
+}
+
+export function buildFileThumbnailRoute(sessionId: string, relativePath: string): string {
+  return `/api/sessions/${sessionId}/file-thumbnail?path=${encodeURIComponent(relativePath)}`;
+}
+
+export function attachmentRecordToEvent(record: AttachmentRecord): AttachmentRegistrationResult {
+  const routes = buildAttachmentRoutes(record.sessionId, record.attachmentId);
+  return {
+    sessionId: record.sessionId,
+    filePath: record.fileName,
+    relativePath: '',
+    fileName: record.fileName,
+    extension: record.extension,
+    attachmentType: record.attachmentType,
+    timestamp: record.timestamp,
+    size: record.size,
+    attachmentId: record.attachmentId,
+    source: record.source,
+    ...routes,
+  };
+}
+
+/** Options for {@link registerExternalAttachment}. */
+export interface RegisterExternalAttachmentOptions {
+  /**
+   * The registering session's working directory. Required only to enforce
+   * workspace confinement when that mode is enabled
+   * (`attachmentConfineToWorkspace` / `CODEMAN_ATTACHMENT_CONFINE`); ignored in
+   * the default blocklist mode.
+   */
+  sessionWorkingDir?: string;
+}
+
+export async function registerExternalAttachment(
+  sessionId: string,
+  requestedPath: string,
+  options: RegisterExternalAttachmentOptions = {}
+): Promise<AttachmentRegistrationResult> {
+  if (!requestedPath || !isAbsolute(requestedPath)) {
+    throw new AttachmentRegistrationError('Attachment path must be an absolute local path');
+  }
+
+  let resolvedPath: string;
+  try {
+    resolvedPath = realpathSync(requestedPath);
+  } catch {
+    throw new AttachmentRegistrationError('Attachment file not found', 404);
+  }
+
+  // COD-53: enforce the active attachment-guard policy on the symlink-resolved
+  // path before doing anything else.
+  const guard = await loadAttachmentGuardConfig();
+
+  if (guard.confineToWorkspace) {
+    // Strict mode (opt-in, default OFF): the file MUST resolve inside the
+    // session's workspace. Strictly more restrictive than the blocklist —
+    // breaks cross-workspace attachment, which is why it is off by default.
+    const workingDir = options.sessionWorkingDir;
+    if (!workingDir || !validateSessionFilePath(workingDir, resolvedPath)) {
+      throw new AttachmentRegistrationError('Access to this file is blocked', 403);
+    }
+  }
+
+  // Blocklist (DEFAULT, also applied alongside confinement as defense in
+  // depth): pre-populated secret locations + the /root and /etc trees + any
+  // operator-configured extra trees. Symlinks are already resolved above.
+  // Cross-workspace attachment of non-blocked files stays allowed, so
+  // codeman-publish and the ~/.codeman review loop keep working.
+  if (isBlockedAttachmentPath(resolvedPath, guard.blockedTrees)) {
+    throw new AttachmentRegistrationError('Access to this file is blocked', 403);
+  }
+
+  const extension = extname(resolvedPath).toLowerCase().replace(/^\./, '');
+  if (!isSupportedAttachmentExtension(extension)) {
+    throw new AttachmentRegistrationError('Unsupported attachment type');
+  }
+
+  const stat = await fs.stat(resolvedPath);
+  if (typeof stat.isFile === 'function' && !stat.isFile()) {
+    throw new AttachmentRegistrationError('Attachment path is not a file');
+  }
+
+  const existing = attachmentRegistry.findByFilePath(sessionId, resolvedPath);
+  if (existing) {
+    existing.size = stat.size;
+    existing.mtimeMs = stat.mtimeMs ?? 0;
+    existing.timestamp = Date.now();
+    return attachmentRecordToEvent(existing);
+  }
+
+  const record: AttachmentRecord = {
+    attachmentId: `att_${randomUUID()}`,
+    sessionId,
+    filePath: resolvedPath,
+    fileName: basename(resolvedPath),
+    extension,
+    attachmentType: getAttachmentType(extension),
+    size: stat.size,
+    mtimeMs: stat.mtimeMs ?? 0,
+    timestamp: Date.now(),
+    source: 'external',
+  };
+  attachmentRegistry.register(record);
+  return attachmentRecordToEvent(record);
+}
diff --git a/src/cli.ts b/src/cli.ts
index ea6536ac..ba5be45f 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -10,11 +10,17 @@
 import { Command } from 'commander';
 import chalk from 'chalk';
 import { createRequire } from 'module';
+import http from 'node:http';
+import https from 'node:https';
+import { readFileSync } from 'node:fs';
+import { homedir } from 'node:os';
+import { isAbsolute, join } from 'node:path';
 import { getSessionManager } from './session-manager.js';
 import { getTaskQueue } from './task-queue.js';
 import { getRalphLoop } from './ralph-loop.js';
 import { getStore } from './state-store.js';
 import { getErrorMessage } from './types.js';
+import { isSupportedAttachmentExtension } from './attachment-registry.js';
 
 const require = createRequire(import.meta.url);
 const pkg = require('../package.json') as { version: string };
@@ -23,6 +29,93 @@ const program = new Command();
 
 program.name('codeman').description('Claude Code session manager with autonomous Ralph Loop').version(pkg.version);
 
+function makeAttachmentMagicLink(filePath: string): string {
+  return `codeman://attach?path=${encodeURIComponent(filePath)}`;
+}
+
+function readCodemanEnv(): Record<string, string> {
+  const envPath = join(homedir(), '.codeman', '.env');
+  try {
+    const text = readFileSync(envPath, 'utf-8');
+    const result: Record<string, string> = {};
+    for (const rawLine of text.split(/\r?\n/)) {
+      const line = rawLine.trim();
+      if (!line || line.startsWith('#')) continue;
+      const match = line.match(/^([A-Za-z_][A-Za-z0-9_]*)=(.*)$/);
+      if (!match) continue;
+      let value = match[2].trim();
+      if ((value.startsWith('"') && value.endsWith('"')) || (value.startsWith("'") && value.endsWith("'"))) {
+        value = value.slice(1, -1);
+      }
+      result[match[1]] = value;
+    }
+    return result;
+  } catch {
+    return {};
+  }
+}
+
+async function postAttachment(apiUrl: string, sessionId: string, filePath: string): Promise<boolean> {
+  const envFile = readCodemanEnv();
+  const username = process.env.CODEMAN_USERNAME || envFile.CODEMAN_USERNAME || 'admin';
+  const password = process.env.CODEMAN_PASSWORD || envFile.CODEMAN_PASSWORD;
+  const url = new URL(`/api/sessions/${encodeURIComponent(sessionId)}/attachments`, apiUrl);
+  const body = JSON.stringify({ path: filePath });
+  const transport = url.protocol === 'https:' ? https : http;
+
+  return new Promise((resolve) => {
+    const headers: Record<string, string | number> = {
+      Accept: 'application/json',
+      'Content-Type': 'application/json',
+      'Content-Length': Buffer.byteLength(body),
+    };
+    if (password) {
+      headers.Authorization = `Basic ${Buffer.from(`${username}:${password}`).toString('base64')}`;
+    }
+
+    const req = transport.request(
+      {
+        protocol: url.protocol,
+        hostname: url.hostname,
+        port: url.port,
+        method: 'POST',
+        path: `${url.pathname}${url.search}`,
+        rejectUnauthorized: false,
+        headers,
+      },
+      (res) => {
+        res.resume();
+        res.on('end', () => resolve(Boolean(res.statusCode && res.statusCode >= 200 && res.statusCode < 300)));
+      }
+    );
+    req.on('error', () => resolve(false));
+    req.write(body);
+    req.end();
+  });
+}
+
+program
+  .command('attach <path>')
+  .description('Show an attachment card for a local file')
+  .option('-s, --session <id>', 'Codeman session ID (defaults to CODEMAN_SESSION_ID)')
+  .option('--url <url>', 'Codeman API URL (defaults to CODEMAN_API_URL or https://127.0.0.1:3000)')
+  .action(async (filePath, options) => {
+    const extension = String(filePath).split('.').pop()?.toLowerCase() || '';
+    if (!isAbsolute(filePath) || !isSupportedAttachmentExtension(extension)) {
+      console.error(chalk.red('✗ attach requires an absolute path to a png, pdf, docx, pptx, md, or txt file'));
+      process.exit(1);
+    }
+
+    const sessionId = options.session || process.env.CODEMAN_SESSION_ID;
+    const apiUrl = options.url || process.env.CODEMAN_API_URL || 'https://127.0.0.1:3000';
+    if (sessionId && (await postAttachment(apiUrl, sessionId, filePath))) {
+      console.log(chalk.green('✓ Attachment card requested'));
+      return;
+    }
+
+    console.log(makeAttachmentMagicLink(filePath));
+  });
+
 // ============ Session Commands ============
 
 const sessionCmd = program.command('session').alias('s').description('Manage Claude sessions');
diff --git a/src/config/attachment-guard.ts b/src/config/attachment-guard.ts
new file mode 100644
index 00000000..86744b47
--- /dev/null
+++ b/src/config/attachment-guard.ts
@@ -0,0 +1,133 @@
+/**
+ * @fileoverview Attachment path-guard configuration (COD-53).
+ *
+ * Governs which host files may be registered as cross-workspace attachments
+ * and served to the browser. Two operator-facing knobs, both with safe
+ * defaults:
+ *
+ *  1. **Blocked-path blocklist (DEFAULT, configurable).** Pre-populated with the
+ *     shared secret-location blocklist (`isSensitivePath`) PLUS the directory
+ *     trees `/root` and `/etc` (anything under them is blocked). The operator
+ *     EXTENDS — never shrinks — this set with additional absolute directory
+ *     trees via the settings key `attachmentBlockedPaths: string[]` and/or the
+ *     env var `CODEMAN_ATTACHMENT_BLOCKED_PATHS` (comma-separated).
+ *
+ *  2. **Workspace confinement (OPTIONAL, default OFF).** When enabled, an
+ *     attachment must resolve INSIDE the registering session's workingDir
+ *     (reusing `validateSessionFilePath` containment semantics). This is
+ *     strictly more restrictive than the blocklist and breaks intentional
+ *     cross-workspace attachment (codeman-publish, the ~/.codeman review-card
+ *     loop), so it is OFF by default. Toggle via settings
+ *     `attachmentConfineToWorkspace: boolean` and/or env
+ *     `CODEMAN_ATTACHMENT_CONFINE` (`1`/`true`).
+ *
+ * All paths passed to the predicates here MUST be absolute and symlink-resolved
+ * (realpath) by the caller, mirroring `isSensitivePath`'s contract.
+ *
+ * @module config/attachment-guard
+ */
+
+import { sep } from 'node:path';
+import { isSensitivePath } from '../web/sensitive-path.js';
+import { readJsonConfig, SETTINGS_PATH } from '../web/route-helpers.js';
+
+/**
+ * Directory trees blocked by default, IN ADDITION to the secret-location
+ * blocklist in `isSensitivePath`. Anything resolving under one of these trees
+ * is rejected. Pre-populated with the root account home and the system config
+ * tree (which already partially overlaps `isSensitivePath`'s `/etc/shadow`
+ * etc., but here we block the WHOLE tree).
+ */
+export const DEFAULT_BLOCKED_TREES: readonly string[] = ['/root', '/etc'];
+
+/** Settings key carrying extra blocked directory trees (extends the defaults). */
+export const ATTACHMENT_BLOCKED_PATHS_SETTING = 'attachmentBlockedPaths';
+
+/** Settings key carrying the workspace-confinement toggle. */
+export const ATTACHMENT_CONFINE_SETTING = 'attachmentConfineToWorkspace';
+
+/** Resolved attachment-guard configuration. */
+export interface AttachmentGuardConfig {
+  /** Pre-populated default trees PLUS any operator extras. */
+  blockedTrees: string[];
+  /** Whether attachments must resolve inside the session workspace. */
+  confineToWorkspace: boolean;
+}
+
+/** Normalizes a tree prefix: trim, drop trailing separators (but keep root). */
+function normalizeTree(raw: string): string {
+  const trimmed = raw.trim();
+  if (!trimmed) return '';
+  // Strip trailing slashes so '/etc/' and '/etc' behave the same; never reduce
+  // a bare separator to empty.
+  const stripped = trimmed.replace(/[/\\]+$/, '');
+  return stripped || trimmed[0];
+}
+
+/**
+ * Returns true if `absPath` (absolute, symlink-resolved) is the tree itself or
+ * lives under it. Uses path-separator-aware matching so `/etc` does NOT block
+ * an unrelated `/etcetera/notes.md`.
+ */
+export function isUnderTree(absPath: string, tree: string): boolean {
+  const t = normalizeTree(tree);
+  if (!t) return false;
+  if (absPath === t) return true;
+  return absPath.startsWith(t.endsWith(sep) ? t : t + sep);
+}
+
+/** Parses the comma-separated env override into a list of normalized trees. */
+function parseEnvBlockedTrees(): string[] {
+  const raw = process.env.CODEMAN_ATTACHMENT_BLOCKED_PATHS;
+  if (!raw) return [];
+  return raw
+    .split(',')
+    .map(normalizeTree)
+    .filter((t) => t.length > 0);
+}
+
+/** Parses the env confinement toggle (`1`/`true`/`yes`/`on`, case-insensitive). */
+function parseEnvConfine(): boolean | undefined {
+  const raw = process.env.CODEMAN_ATTACHMENT_CONFINE;
+  if (raw === undefined) return undefined;
+  return /^(1|true|yes|on)$/i.test(raw.trim());
+}
+
+/**
+ * Loads the effective attachment-guard config by merging the pre-populated
+ * defaults with settings.json and env overrides. Env wins over settings for the
+ * confinement toggle; blocked-tree extras from BOTH sources are unioned on top
+ * of the defaults (operators can only EXTEND, never shrink, the blocked set).
+ */
+export async function loadAttachmentGuardConfig(): Promise<AttachmentGuardConfig> {
+  const settings = await readJsonConfig<Record<string, unknown>>(SETTINGS_PATH, 'settings.json', {});
+
+  const settingsTrees = Array.isArray(settings[ATTACHMENT_BLOCKED_PATHS_SETTING])
+    ? (settings[ATTACHMENT_BLOCKED_PATHS_SETTING] as unknown[])
+        .filter((v): v is string => typeof v === 'string')
+        .map(normalizeTree)
+        .filter((t) => t.length > 0)
+    : [];
+
+  const blockedTrees = Array.from(new Set([...DEFAULT_BLOCKED_TREES, ...settingsTrees, ...parseEnvBlockedTrees()]));
+
+  const envConfine = parseEnvConfine();
+  const settingsConfine = settings[ATTACHMENT_CONFINE_SETTING] === true;
+  const confineToWorkspace = envConfine ?? settingsConfine;
+
+  return { blockedTrees, confineToWorkspace };
+}
+
+/**
+ * Attachment-specific blocklist check. Builds on the shared `isSensitivePath`
+ * base (secret locations, shared with `/api/download`) and ADDS the configured
+ * directory trees (`/root`, `/etc`, plus operator extras). `absPath` must be
+ * absolute and symlink-resolved.
+ *
+ * NOTE: this is intentionally a SUPERSET of `isSensitivePath` so `/api/download`
+ * behavior is NOT changed — only attachment registration/serving uses this.
+ */
+export function isBlockedAttachmentPath(absPath: string, blockedTrees: readonly string[]): boolean {
+  if (isSensitivePath(absPath)) return true;
+  return blockedTrees.some((tree) => isUnderTree(absPath, tree));
+}
diff --git a/src/image-watcher.ts b/src/image-watcher.ts
index 35454909..e0f8c7ae 100644
--- a/src/image-watcher.ts
+++ b/src/image-watcher.ts
@@ -12,7 +12,7 @@ import { EventEmitter } from 'node:events';
 import { watch, type FSWatcher } from 'chokidar';
 import { basename, extname, relative } from 'node:path';
 import { statSync } from 'node:fs';
-import type { ImageDetectedEvent } from './types.js';
+import type { AttachmentDetectedEvent, AttachmentDetectedType, ImageDetectedEvent } from './types.js';
 import { KeyedDebouncer } from './utils/index.js';
 
 // ========== Types ==========
@@ -20,7 +20,9 @@ import { KeyedDebouncer } from './utils/index.js';
 // ========== Constants ==========
 
 /** Supported image file extensions (lowercase) */
-const IMAGE_EXTENSIONS = new Set(['.png', '.jpg', '.jpeg', '.gif', '.webp', '.bmp', '.svg']);
+const IMAGE_POPUP_EXTENSIONS = new Set(['.jpg', '.jpeg', '.gif', '.webp', '.bmp', '.svg']);
+const ATTACHMENT_EXTENSIONS = new Set(['.png', '.pdf', '.docx', '.pptx']);
+const DETECTED_FILE_EXTENSIONS = new Set([...IMAGE_POPUP_EXTENSIONS, ...ATTACHMENT_EXTENSIONS]);
 
 /** Time to wait for file writes to stabilize (ms) */
 const STABILITY_THRESHOLD_MS = 500;
@@ -166,8 +168,8 @@ export class ImageWatcher extends EventEmitter {
           }
           const ext = extname(path).toLowerCase();
           // Don't ignore directories (needed for watching to work)
-          // Ignore files that aren't images
-          return ext !== '' && !IMAGE_EXTENSIONS.has(ext);
+          // Ignore files that aren't previewable images/documents
+          return ext !== '' && !DETECTED_FILE_EXTENSIONS.has(ext);
         },
       });
 
@@ -229,15 +231,16 @@ export class ImageWatcher extends EventEmitter {
 
   /**
    * Handle a new file being detected.
-   * Verifies it's an image and emits the detection event.
+   * Verifies it's a previewable image/document and emits the detection event.
    */
   private handleNewFile(sessionId: string, filePath: string): void {
     const ext = extname(filePath).toLowerCase();
 
-    // Double-check it's an image extension
-    if (!IMAGE_EXTENSIONS.has(ext)) {
+    // Double-check it's a supported extension
+    if (!DETECTED_FILE_EXTENSIONS.has(ext)) {
       return;
     }
+    const isAttachment = ATTACHMENT_EXTENSIONS.has(ext);
 
     // Burst limit: skip if too many images detected for this session in a short window
     const now = Date.now();
@@ -259,7 +262,11 @@ export class ImageWatcher extends EventEmitter {
     // Debounce rapid file creation (e.g., multiple screenshots quickly)
     this.fileDeb.schedule(filePath, () => {
       this.fileToSession.delete(filePath);
-      this.emitImageDetected(sessionId, filePath);
+      if (isAttachment) {
+        this.emitAttachmentDetected(sessionId, filePath);
+      } else {
+        this.emitImageDetected(sessionId, filePath);
+      }
       // Increment burst count on actual emission (not on detection)
       const b = this.burstTrackers.get(sessionId);
       if (b) b.count++;
@@ -294,6 +301,42 @@ export class ImageWatcher extends EventEmitter {
       this.emit('image:error', error instanceof Error ? error : new Error(String(error)), sessionId);
     }
   }
+
+  /**
+   * Emit the attachment:detected event with file metadata.
+   */
+  private emitAttachmentDetected(sessionId: string, filePath: string): void {
+    try {
+      const stat = statSync(filePath);
+      const fileName = basename(filePath);
+      const workingDir = this.sessionDirs.get(sessionId);
+      const relativePath = workingDir ? relative(workingDir, filePath) : fileName;
+      const extension = extname(fileName).toLowerCase().replace(/^\./, '');
+
+      const event: AttachmentDetectedEvent = {
+        sessionId,
+        filePath,
+        relativePath,
+        fileName,
+        extension,
+        attachmentType: this.getAttachmentType(extension),
+        timestamp: Date.now(),
+        size: stat.size,
+      };
+
+      this.emit('attachment:detected', event);
+    } catch (error) {
+      this.emit('image:error', error instanceof Error ? error : new Error(String(error)), sessionId);
+    }
+  }
+
+  private getAttachmentType(extension: string): AttachmentDetectedType {
+    if (extension === 'png') return 'image';
+    if (extension === 'pdf') return 'pdf';
+    if (extension === 'docx') return 'document';
+    if (extension === 'pptx') return 'presentation';
+    return 'document';
+  }
 }
 
 // Export singleton instance for convenience
diff --git a/src/session.ts b/src/session.ts
index f5b6c60f..1bd5d5f7 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -80,6 +80,7 @@ import {
 import { SessionAutoOps } from './session-auto-ops.js';
 import { detectUsageLimitPause } from './usage-limit-patterns.js';
 import { SessionTaskCache } from './session-task-cache.js';
+import { parseAttachmentMagicLinks } from './attachment-magic.js';
 
 export type { BackgroundTask } from './task-tracker.js';
 export type { RalphTrackerState, RalphTodoItem, ActiveBashTool } from './types.js';
@@ -311,6 +312,9 @@ export class Session extends EventEmitter {
   private _parentAgentId: string | null = null;
   private _childAgentIds: string[] = [];
 
+  // Bounded dedup set for terminal attachment magic-links already requested.
+  private _attachmentMagicSeen = new Set<string>();
+
   // Nice prioritying configuration
   private _niceConfig: NiceConfig = { ...DEFAULT_NICE_CONFIG };
 
@@ -1135,6 +1139,20 @@ export class Session extends EventEmitter {
         .replace(/\x1b\[\?(?:1000|1001|1002|1003|1005|1006|1007)[hl]/g, '');
     }
 
+    // Scan terminal output for `codeman://attach?path=...` magic links and emit
+    // an attachmentRequested event for each newly-seen absolute path. The web
+    // server turns these into registered attachment cards.
+    const attachmentPaths = parseAttachmentMagicLinks(data);
+    for (const attachmentPath of attachmentPaths) {
+      if (this._attachmentMagicSeen.has(attachmentPath)) continue;
+      this._attachmentMagicSeen.add(attachmentPath);
+      if (this._attachmentMagicSeen.size > 200) {
+        const oldest = this._attachmentMagicSeen.values().next().value;
+        if (oldest) this._attachmentMagicSeen.delete(oldest);
+      }
+      this.emit('attachmentRequested', { sessionId: this.id, path: attachmentPath, timestamp: Date.now() });
+    }
+
     // BufferAccumulator handles auto-trimming when max size exceeded
     this._terminalBuffer.append(data);
     this._lastActivityAt = Date.now();
diff --git a/src/types/tools.ts b/src/types/tools.ts
index 1e3de918..233c0205 100644
--- a/src/types/tools.ts
+++ b/src/types/tools.ts
@@ -7,13 +7,14 @@
  * - ActiveBashTool — a live bash command with extracted file paths and status
  * - ActiveBashToolStatus — 'running' | 'completed'
  * - ImageDetectedEvent — screenshot/image file detection trigger for UI popup
+ * - AttachmentDetectedEvent — document/image file detection trigger for attachment cards
  *
  * Cross-domain relationships:
  * - ActiveBashTool.sessionId links to SessionState.id (session domain)
  * - ImageDetectedEvent.sessionId links to SessionState.id (session domain)
  *
  * Both types are in-memory only (not persisted). Broadcast via SSE events
- * `subagent:tool_call` and `image:detected`. Parsed by BashToolParser
+ * `subagent:tool_call`, `image:detected`, and `attachment:detected`. Parsed by BashToolParser
  * (`src/bash-tool-parser.ts`).
  */
 
@@ -61,3 +62,38 @@ export interface ImageDetectedEvent {
   /** File size in bytes */
   size: number;
 }
+
+export type AttachmentDetectedType = 'image' | 'pdf' | 'document' | 'presentation' | 'markdown' | 'text';
+
+/**
+ * Event emitted when a new previewable attachment file is detected in a session's
+ * working directory. Used to render a compact attachment card in the web UI.
+ */
+export interface AttachmentDetectedEvent {
+  /** Codeman session ID where the attachment was detected */
+  sessionId: string;
+  /** Full path to the detected attachment file */
+  filePath: string;
+  /** Path relative to the session's working directory (for file-raw/file-preview endpoints) */
+  relativePath: string;
+  /** Attachment file name (basename) */
+  fileName: string;
+  /** Lowercase extension without a leading dot */
+  extension: string;
+  /** Viewer category used by the web UI */
+  attachmentType: AttachmentDetectedType;
+  /** Timestamp when the attachment was detected */
+  timestamp: number;
+  /** File size in bytes */
+  size: number;
+  /** Registered attachment id for explicit live external attachments */
+  attachmentId?: string;
+  /** Source of the attachment card request */
+  source?: 'detected' | 'external';
+  /** Raw file route for explicit attachments */
+  rawUrl?: string;
+  /** Inline preview route for explicit attachments */
+  previewUrl?: string;
+  /** First-page thumbnail route for card previews */
+  thumbnailUrl?: string;
+}
diff --git a/src/web/public/constants.js b/src/web/public/constants.js
index c3b22714..1dc86bc1 100644
--- a/src/web/public/constants.js
+++ b/src/web/public/constants.js
@@ -336,6 +336,7 @@ const SSE_EVENTS = {
 
   // Images
   IMAGE_DETECTED: 'image:detected',
+  ATTACHMENT_DETECTED: 'attachment:detected',
 
   // Tunnel
   TUNNEL_STARTED: 'tunnel:started',
diff --git a/src/web/routes/file-routes.ts b/src/web/routes/file-routes.ts
index 2b8051df..8f40febd 100644
--- a/src/web/routes/file-routes.ts
+++ b/src/web/routes/file-routes.ts
@@ -3,16 +3,146 @@
  * Provides directory listing, file content preview, raw file serving, and tail streaming.
  */
 
-import { FastifyInstance } from 'fastify';
+import { FastifyInstance, type FastifyReply } from 'fastify';
 import { basename as pathBasename, join } from 'node:path';
-import { homedir } from 'node:os';
+import { createReadStream, realpathSync, type ReadStream } from 'node:fs';
 import fs from 'node:fs/promises';
 import { ApiErrorCode, createErrorResponse, getErrorMessage } from '../../types.js';
 import { fileStreamManager } from '../../file-stream-manager.js';
+import {
+  AttachmentRegistrationError,
+  attachmentRegistry,
+  registerExternalAttachment,
+  type AttachmentRecord,
+} from '../../attachment-registry.js';
+import { isBlockedAttachmentPath, loadAttachmentGuardConfig } from '../../config/attachment-guard.js';
 import { findSessionOrFail, validateSessionFilePath } from '../route-helpers.js';
-import type { SessionPort } from '../ports/index.js';
+import { isSensitivePath } from '../sensitive-path.js';
+import { SseEvent } from '../sse-events.js';
+import type { EventPort, SessionPort } from '../ports/index.js';
 
-export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort): void {
+const MIME_TYPES: Record<string, string> = {
+  png: 'image/png',
+  jpg: 'image/jpeg',
+  jpeg: 'image/jpeg',
+  gif: 'image/gif',
+  webp: 'image/webp',
+  ico: 'image/x-icon',
+  bmp: 'image/bmp',
+  pdf: 'application/pdf',
+  docx: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+  pptx: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+  json: 'application/json',
+  md: 'text/markdown',
+  txt: 'text/plain',
+};
+
+function sanitizeDownloadName(fileName: string): string {
+  return fileName.replace(/["\\\r\n]/g, '_');
+}
+
+function sendRawStream(reply: FastifyReply, content: ReadStream): void {
+  const headers = reply.getHeaders();
+  reply.hijack();
+
+  for (const [name, value] of Object.entries(headers)) {
+    if (value !== undefined) {
+      reply.raw.setHeader(name, value);
+    }
+  }
+
+  content.on('error', (err) => {
+    if (reply.raw.headersSent) {
+      reply.raw.destroy(err);
+      return;
+    }
+
+    reply.raw.statusCode = 500;
+    reply.raw.end('Failed to read file');
+  });
+  content.pipe(reply.raw);
+}
+
+async function serveRawFile(
+  reply: FastifyReply,
+  resolvedPath: string,
+  fileName: string,
+  extension: string,
+  download?: boolean
+): Promise<void> {
+  const stat = await fs.stat(resolvedPath);
+  const content = createReadStream(resolvedPath);
+  const safeName = sanitizeDownloadName(fileName);
+  if (download || extension === 'svg') {
+    reply.header(
+      'Content-Type',
+      extension === 'svg' ? 'application/octet-stream' : MIME_TYPES[extension] || 'application/octet-stream'
+    );
+    reply.header('Content-Disposition', `attachment; filename="${safeName}"`);
+    reply.header('Content-Length', stat.size);
+    reply.header('X-Content-Type-Options', 'nosniff');
+    sendRawStream(reply, content);
+    return;
+  }
+
+  reply.header('Content-Type', MIME_TYPES[extension] || 'application/octet-stream');
+  reply.header('Content-Disposition', `inline; filename="${safeName}"`);
+  reply.header('Content-Length', stat.size);
+  reply.header('X-Content-Type-Options', 'nosniff');
+  sendRawStream(reply, content);
+}
+
+function getAttachmentOr404(
+  reply: FastifyReply,
+  sessionId: string,
+  attachmentId: string
+): AttachmentRecord | undefined {
+  const record = attachmentRegistry.get(sessionId, attachmentId);
+  if (!record) {
+    reply.code(404).send(createErrorResponse(ApiErrorCode.NOT_FOUND, 'Attachment not found'));
+    return undefined;
+  }
+  return record;
+}
+
+/**
+ * COD-53 defense-in-depth: refuse to stream a record whose underlying path is
+ * blocked by the active attachment-guard policy, even though registration
+ * already blocks them. Guards against records that predate the guard or were
+ * crafted to point at a sensitive file. Resolves symlinks before the check so a
+ * record pointing at a symlink that now resolves to a sensitive target is also
+ * caught; if the path can't be resolved (deleted/unreadable) the check still
+ * runs on the stored path. When workspace confinement is enabled it additionally
+ * rejects any record outside the session workspace. Returns true (and sends a
+ * 403) when blocked.
+ */
+async function rejectIfSensitiveRecord(
+  reply: FastifyReply,
+  record: AttachmentRecord,
+  sessionWorkingDir?: string
+): Promise<boolean> {
+  let pathToCheck = record.filePath;
+  try {
+    pathToCheck = realpathSync(record.filePath);
+  } catch {
+    // Fall back to the stored (already realpath-resolved at registration) path.
+  }
+
+  const guard = await loadAttachmentGuardConfig();
+
+  const blocked =
+    isBlockedAttachmentPath(pathToCheck, guard.blockedTrees) ||
+    isBlockedAttachmentPath(record.filePath, guard.blockedTrees) ||
+    (guard.confineToWorkspace && (!sessionWorkingDir || !validateSessionFilePath(sessionWorkingDir, pathToCheck)));
+
+  if (blocked) {
+    reply.code(403).send(createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Access to this file is blocked'));
+    return true;
+  }
+  return false;
+}
+
+export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort & EventPort): void {
   // File tree listing
   app.get('/api/sessions/:id/files', async (req) => {
     const { id } = req.params as { id: string };
@@ -315,6 +445,58 @@ export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort): void
     }
   });
 
+  // ===== Live external attachments =====
+  // Register an explicit, live external file (absolute host path) as an
+  // attachment with a stable id so browser requests never carry arbitrary
+  // paths. Registration enforces the COD-53 attachment-guard policy. Serving is
+  // by id via the /raw route below; document previews/thumbnails and the
+  // attachment-history list are layered on separately.
+  app.post('/api/sessions/:id/attachments', async (req, reply) => {
+    const { id } = req.params as { id: string };
+    const session = findSessionOrFail(ctx, id);
+    const body = (req.body || {}) as { path?: string };
+
+    if (!body.path || typeof body.path !== 'string') {
+      reply.code(400).send(createErrorResponse(ApiErrorCode.INVALID_INPUT, 'Missing attachment path'));
+      return;
+    }
+
+    try {
+      const event = await registerExternalAttachment(id, body.path, { sessionWorkingDir: session.workingDir });
+      ctx.broadcast(SseEvent.AttachmentDetected, event);
+      return { success: true, data: event };
+    } catch (err) {
+      if (err instanceof AttachmentRegistrationError) {
+        reply.code(err.statusCode).send(createErrorResponse(ApiErrorCode.INVALID_INPUT, err.message));
+        return;
+      }
+      return reply
+        .code(500)
+        .send(
+          createErrorResponse(ApiErrorCode.OPERATION_FAILED, `Failed to register attachment: ${getErrorMessage(err)}`)
+        );
+    }
+  });
+
+  // Serve the raw bytes of a registered attachment by id. Re-checks the
+  // attachment-guard policy on every request (defense-in-depth) before streaming.
+  app.get('/api/sessions/:id/attachments/:attachmentId/raw', async (req, reply) => {
+    const { id, attachmentId } = req.params as { id: string; attachmentId: string };
+    const { download } = req.query as { download?: string };
+    const session = findSessionOrFail(ctx, id);
+    const record = getAttachmentOr404(reply, id, attachmentId);
+    if (!record) return;
+    if (await rejectIfSensitiveRecord(reply, record, session.workingDir)) return;
+
+    try {
+      await serveRawFile(reply, record.filePath, record.fileName, record.extension, download === 'true');
+    } catch (err) {
+      reply
+        .code(500)
+        .send(createErrorResponse(ApiErrorCode.OPERATION_FAILED, `Failed to read file: ${getErrorMessage(err)}`));
+    }
+  });
+
   // Stream file content via tail -f (SSE endpoint)
   app.get('/api/sessions/:id/tail-file', async (req, reply) => {
     const { id } = req.params as { id: string };
@@ -387,24 +569,8 @@ export function registerFileRoutes(app: FastifyInstance, ctx: SessionPort): void
   });
   // Session-scoped file download.
   // Uses the same realpath-based workspace boundary as file preview/raw routes;
-  // the sensitive-path blocklist remains defense-in-depth, not the primary boundary.
-  const SENSITIVE_PATTERNS: RegExp[] = [
-    /^\/etc\/shadow$/,
-    /^\/etc\/gshadow$/,
-    /^\/etc\/master\.passwd$/,
-    new RegExp(`^${homedir().replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}\\/\\.ssh\\/`),
-    /\/\.env$/,
-    /\/\.env\./,
-    /\/credentials(\.json|\.yml|\.yaml|\.xml)?$/i,
-    /\/\.aws\/credentials$/,
-    /\/\.gcloud\/credentials\.db$/,
-    /\/\.docker\/config\.json$/,
-  ];
-
-  function isSensitivePath(absPath: string): boolean {
-    return SENSITIVE_PATTERNS.some((pattern) => pattern.test(absPath));
-  }
-
+  // the shared sensitive-path blocklist (../sensitive-path.js, also used by the
+  // attachment guard) remains defense-in-depth, not the primary boundary.
   app.get('/api/download', async (req, reply) => {
     const { path: filePath, sessionId } = req.query as { path?: string; sessionId?: string };
 
diff --git a/src/web/sensitive-path.ts b/src/web/sensitive-path.ts
new file mode 100644
index 00000000..cb3e8624
--- /dev/null
+++ b/src/web/sensitive-path.ts
@@ -0,0 +1,41 @@
+/**
+ * @fileoverview Shared sensitive-path blocklist.
+ *
+ * A small defense-in-depth blocklist of absolute paths that must never be
+ * served to the browser regardless of how the path was obtained (workspace
+ * download, cross-workspace attachment registration, raw/preview serving).
+ *
+ * This is intentionally a BLOCKLIST, not a workspace-confinement check:
+ * cross-workspace attachment is a supported feature (codeman-publish skill +
+ * the automated review-card loop attaching files under ~/.codeman/), so a
+ * strict session-workspace boundary would break legitimate use. The blocklist
+ * rejects well-known secret locations (system password files, SSH keys, cloud
+ * credentials, dotenv files) while leaving ordinary cross-workspace files
+ * attachable.
+ *
+ * Callers MUST resolve symlinks (realpath) BEFORE calling isSensitivePath so a
+ * symlink pointing at a sensitive target is also caught.
+ */
+
+import { homedir } from 'node:os';
+
+const SENSITIVE_PATTERNS: RegExp[] = [
+  /^\/etc\/shadow$/,
+  /^\/etc\/gshadow$/,
+  /^\/etc\/master\.passwd$/,
+  new RegExp(`^${homedir().replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}\\/\\.ssh\\/`),
+  /\/\.env$/,
+  /\/\.env\./,
+  /\/credentials(\.json|\.yml|\.yaml|\.xml)?$/i,
+  /\/\.aws\/credentials$/,
+  /\/\.gcloud\/credentials\.db$/,
+  /\/\.docker\/config\.json$/,
+];
+
+/**
+ * Returns true if the given ABSOLUTE, symlink-resolved path matches the
+ * sensitive-file blocklist and must not be served to the browser.
+ */
+export function isSensitivePath(absPath: string): boolean {
+  return SENSITIVE_PATTERNS.some((pattern) => pattern.test(absPath));
+}
diff --git a/src/web/server.ts b/src/web/server.ts
index aeb57a14..ae812568 100644
--- a/src/web/server.ts
+++ b/src/web/server.ts
@@ -60,6 +60,7 @@ import {
   type SubagentToolResult,
 } from '../subagent-watcher.js';
 import { imageWatcher } from '../image-watcher.js';
+import { attachmentRegistry, registerExternalAttachment } from '../attachment-registry.js';
 import { TranscriptWatcher } from '../transcript-watcher.js';
 import { TeamWatcher } from '../team-watcher.js';
 import { TunnelManager } from '../tunnel-manager.js';
@@ -110,6 +111,7 @@ import {
   type PersistedRespawnConfig,
   type NiceConfig,
   type ImageDetectedEvent,
+  type AttachmentDetectedEvent,
   DEFAULT_NICE_CONFIG,
 } from '../types.js';
 import {
@@ -248,6 +250,7 @@ export class WebServer extends EventEmitter {
   } | null = null;
   private imageWatcherHandlers: {
     detected: (event: ImageDetectedEvent) => void;
+    attachmentDetected: (event: AttachmentDetectedEvent) => void;
     error: (error: Error, sessionId?: string) => void;
   } | null = null;
   private tunnelManager: TunnelManager = new TunnelManager();
@@ -436,12 +439,15 @@ export class WebServer extends EventEmitter {
     // Store handlers for cleanup on shutdown
     this.imageWatcherHandlers = {
       detected: (event: ImageDetectedEvent) => this.broadcast(SseEvent.ImageDetected, event),
+      attachmentDetected: (event: AttachmentDetectedEvent) =>
+        this.broadcast(SseEvent.AttachmentDetected, { ...event, source: event.source || 'detected' }),
       error: (error: Error, sessionId?: string) => {
         console.error(`[ImageWatcher] Error${sessionId ? ` for ${sessionId}` : ''}:`, error.message);
       },
     };
 
     imageWatcher.on('image:detected', this.imageWatcherHandlers.detected);
+    imageWatcher.on('attachment:detected', this.imageWatcherHandlers.attachmentDetected);
     imageWatcher.on('image:error', this.imageWatcherHandlers.error);
   }
 
@@ -451,6 +457,7 @@ export class WebServer extends EventEmitter {
   private cleanupImageWatcherListeners(): void {
     if (this.imageWatcherHandlers) {
       imageWatcher.off('image:detected', this.imageWatcherHandlers.detected);
+      imageWatcher.off('attachment:detected', this.imageWatcherHandlers.attachmentDetected);
       imageWatcher.off('image:error', this.imageWatcherHandlers.error);
       this.imageWatcherHandlers = null;
     }
@@ -1067,6 +1074,8 @@ export class WebServer extends EventEmitter {
       session.removeAllListeners();
       // Close any active file streams for this session
       fileStreamManager.closeSessionStreams(sessionId);
+      // Drop live external attachment registrations for this session
+      attachmentRegistry.clearSession(sessionId);
       // Stop watching for images in this session's directory
       imageWatcher.unwatchSession(sessionId);
       // Clean up pasted images directory for this session
@@ -1252,9 +1261,23 @@ export class WebServer extends EventEmitter {
         }
       },
       getStore: () => this.store,
+      registerAttachment: (id: string, filePath: string) => this.registerAttachment(id, filePath),
     };
   }
 
+  /**
+   * Register a terminal-requested external file as a live attachment and
+   * broadcast it. Triggered by the session's `attachmentRequested` event
+   * (codeman://attach magic links). Registration enforces the COD-53
+   * attachment-guard policy.
+   */
+  private async registerAttachment(sessionId: string, filePath: string): Promise<void> {
+    const session = this.sessions.get(sessionId);
+    if (!session) return;
+    const event = await registerExternalAttachment(sessionId, filePath, { sessionWorkingDir: session.workingDir });
+    this.broadcast(SseEvent.AttachmentDetected, event);
+  }
+
   private setupRespawnListeners(sessionId: string, controller: RespawnController): void {
     wireRespawnListeners(sessionId, controller, this.buildRespawnWiringDeps());
   }
diff --git a/src/web/session-listener-wiring.ts b/src/web/session-listener-wiring.ts
index 40817f83..5a0f9a4f 100644
--- a/src/web/session-listener-wiring.ts
+++ b/src/web/session-listener-wiring.ts
@@ -58,6 +58,7 @@ export interface SessionListenerRefs {
   bashToolStart: (tool: ActiveBashTool) => void;
   bashToolEnd: (tool: ActiveBashTool) => void;
   bashToolsUpdate: (tools: ActiveBashTool[]) => void;
+  attachmentRequested: (event: { path: string }) => void;
 }
 
 /** Dependencies injected by WebServer — keeps listener creation decoupled from server internals. */
@@ -77,10 +78,11 @@ interface SessionListenerDeps {
   removeSessionListenerRefs(sessionId: string): void;
   cleanupRespawnOnExit(sessionId: string): void;
   getStore(): import('../state-store.js').StateStore;
+  registerAttachment(sessionId: string, filePath: string): Promise<void>;
 }
 
 /**
- * Creates all 25 session listener handlers, capturing dependencies via closure.
+ * Creates all 26 session listener handlers, capturing dependencies via closure.
  * Call `attachSessionListeners()` after to wire them to the session.
  */
 export function createSessionListeners(session: Session, deps: SessionListenerDeps): SessionListenerRefs {
@@ -355,6 +357,13 @@ export function createSessionListeners(session: Session, deps: SessionListenerDe
     bashToolsUpdate: (tools: ActiveBashTool[]) => {
       deps.broadcast(SseEvent.SessionBashToolsUpdate, { sessionId: session.id, tools });
     },
+
+    /** Registers an explicit attachment card requested by terminal magic text. */
+    attachmentRequested: (event: { path: string }) => {
+      deps.registerAttachment(session.id, event.path).catch((err) => {
+        console.error(`[Attachment] Failed to register ${event.path} for ${session.id}:`, err);
+      });
+    },
   };
 }
 
@@ -388,6 +397,7 @@ export function attachSessionListeners(session: Session, refs: SessionListenerRe
   session.on('bashToolStart', refs.bashToolStart);
   session.on('bashToolEnd', refs.bashToolEnd);
   session.on('bashToolsUpdate', refs.bashToolsUpdate);
+  session.on('attachmentRequested', refs.attachmentRequested);
 }
 
 /** Detach all listeners from a session (prevents memory leaks from closure references). */
@@ -420,4 +430,5 @@ export function detachSessionListeners(session: Session, refs: SessionListenerRe
   session.off('bashToolStart', refs.bashToolStart);
   session.off('bashToolEnd', refs.bashToolEnd);
   session.off('bashToolsUpdate', refs.bashToolsUpdate);
+  session.off('attachmentRequested', refs.attachmentRequested);
 }
diff --git a/src/web/sse-events.ts b/src/web/sse-events.ts
index 98e98d92..e851dfd6 100644
--- a/src/web/sse-events.ts
+++ b/src/web/sse-events.ts
@@ -284,6 +284,8 @@ export const TunnelQrAuthUsed = 'tunnel:qrAuthUsed' as const;
 
 /** New image file detected (e.g. screenshot upload). */
 export const ImageDetected = 'image:detected' as const;
+/** New document/image attachment detected in a session working directory. */
+export const AttachmentDetected = 'attachment:detected' as const;
 
 // ─── Hooks ───────────────────────────────────────────────────────────────────
 
@@ -479,6 +481,7 @@ export const SseEvent = {
 
   // Image
   ImageDetected,
+  AttachmentDetected,
 
   // Hooks
   HookIdlePrompt,
diff --git a/test/attachment-magic.test.ts b/test/attachment-magic.test.ts
new file mode 100644
index 00000000..0acbae2d
--- /dev/null
+++ b/test/attachment-magic.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest';
+import { Session } from '../src/session.js';
+import { parseAttachmentMagicLinks } from '../src/attachment-magic.js';
+
+describe('attachment magic links', () => {
+  it('extracts absolute paths from codeman attach magic URLs', () => {
+    const links = parseAttachmentMagicLinks(
+      'Preview this: codeman://attach?path=%2Fmnt%2Fc%2FDecks%2FBoard%20Update.pptx'
+    );
+
+    expect(links).toEqual(['/mnt/c/Decks/Board Update.pptx']);
+  });
+
+  it('ignores duplicate links in one terminal chunk', () => {
+    const links = parseAttachmentMagicLinks(
+      [
+        'codeman://attach?path=/tmp/report.pdf',
+        'codeman://attach?path=/tmp/report.pdf',
+        'codeman://attach?path=/tmp/brief.docx',
+      ].join('\n')
+    );
+
+    expect(links).toEqual(['/tmp/report.pdf', '/tmp/brief.docx']);
+  });
+
+  it('accepts markdown and plain-text magic paths', () => {
+    const links = parseAttachmentMagicLinks(
+      ['codeman://attach?path=/tmp/notes.md', 'codeman://attach?path=/tmp/run.txt'].join('\n')
+    );
+
+    expect(links).toEqual(['/tmp/notes.md', '/tmp/run.txt']);
+  });
+
+  it('rejects relative or unsupported magic paths', () => {
+    const links = parseAttachmentMagicLinks(
+      [
+        'codeman://attach?path=relative.pdf',
+        'codeman://attach?path=/tmp/archive.zip',
+        'codeman://attach?path=/tmp/deck.pptx',
+      ].join('\n')
+    );
+
+    expect(links).toEqual(['/tmp/deck.pptx']);
+  });
+
+  it('emits attachmentRequested from raw terminal output', () => {
+    const session = new Session({ id: 'session-attach-test', workingDir: '/tmp', mode: 'codex' });
+    const requested: string[] = [];
+    session.on('attachmentRequested', (event: { path: string }) => requested.push(event.path));
+
+    (session as unknown as { _handleTerminalOutput(data: string): void })._handleTerminalOutput(
+      'codeman://attach?path=%2Ftmp%2Fdeck.pptx'
+    );
+
+    expect(requested).toEqual(['/tmp/deck.pptx']);
+  });
+});
diff --git a/test/image-watcher.test.ts b/test/image-watcher.test.ts
index 19832091..c7e97955 100644
--- a/test/image-watcher.test.ts
+++ b/test/image-watcher.test.ts
@@ -145,9 +145,9 @@ describe('ImageWatcher', () => {
   // ========== Image Detection ==========
 
   describe('image detection', () => {
-    it('should emit image:detected for .png files', () => {
+    it('should emit attachment:detected for .png files', () => {
       const handler = vi.fn();
-      watcher.on('image:detected', handler);
+      watcher.on('attachment:detected', handler);
 
       watcher.watchSession('session-1', '/home/user/project');
       const chokidarWatcher = mockWatchers.get('/home/user/project')!;
@@ -161,9 +161,42 @@ describe('ImageWatcher', () => {
       expect(event.fileName).toBe('screenshot.png');
       expect(event.filePath).toBe('/home/user/project/screenshot.png');
       expect(event.relativePath).toBe('screenshot.png');
+      expect(event.extension).toBe('png');
+      expect(event.attachmentType).toBe('image');
       expect(event.size).toBe(2048);
     });
 
+    it('should not emit legacy image:detected for .png attachment cards', () => {
+      const handler = vi.fn();
+      watcher.on('image:detected', handler);
+
+      watcher.watchSession('session-1', '/home/user/project');
+      mockWatchers.get('/home/user/project')!.emit('add', '/home/user/project/screenshot.png');
+      vi.advanceTimersByTime(300);
+
+      expect(handler).not.toHaveBeenCalled();
+    });
+
+    it.each([
+      ['report.pdf', 'pdf'],
+      ['brief.docx', 'document'],
+      ['deck.pptx', 'presentation'],
+    ])('should emit attachment:detected for %s files', (fileName, attachmentType) => {
+      const handler = vi.fn();
+      watcher.on('attachment:detected', handler);
+
+      watcher.watchSession('session-1', '/home/user/project');
+      mockWatchers.get('/home/user/project')!.emit('add', `/home/user/project/${fileName}`);
+      vi.advanceTimersByTime(300);
+
+      expect(handler).toHaveBeenCalledTimes(1);
+      expect(handler.mock.calls[0][0]).toMatchObject({
+        sessionId: 'session-1',
+        fileName,
+        attachmentType,
+      });
+    });
+
     it('should emit for .jpg files', () => {
       const handler = vi.fn();
       watcher.on('image:detected', handler);
@@ -250,10 +283,10 @@ describe('ImageWatcher', () => {
       watcher.on('image:detected', handler);
 
       watcher.watchSession('session-1', '/home/user/project');
-      mockWatchers.get('/home/user/project')!.emit('add', '/home/user/project/assets/img.png');
+      mockWatchers.get('/home/user/project')!.emit('add', '/home/user/project/assets/img.jpg');
       vi.advanceTimersByTime(300);
 
-      expect(handler.mock.calls[0][0].relativePath).toBe('assets/img.png');
+      expect(handler.mock.calls[0][0].relativePath).toBe('assets/img.jpg');
     });
   });
 
@@ -268,11 +301,11 @@ describe('ImageWatcher', () => {
       const chokidarWatcher = mockWatchers.get('/home/user/project')!;
 
       // Rapid adds of the same file
-      chokidarWatcher.emit('add', '/home/user/project/screenshot.png');
+      chokidarWatcher.emit('add', '/home/user/project/screenshot.jpg');
       vi.advanceTimersByTime(100); // not yet past debounce
-      chokidarWatcher.emit('add', '/home/user/project/screenshot.png');
+      chokidarWatcher.emit('add', '/home/user/project/screenshot.jpg');
       vi.advanceTimersByTime(100);
-      chokidarWatcher.emit('add', '/home/user/project/screenshot.png');
+      chokidarWatcher.emit('add', '/home/user/project/screenshot.jpg');
       vi.advanceTimersByTime(300); // now past debounce from last emit
 
       // Should only emit once (the last debounced one)
@@ -286,8 +319,8 @@ describe('ImageWatcher', () => {
       watcher.watchSession('session-1', '/home/user/project');
       const chokidarWatcher = mockWatchers.get('/home/user/project')!;
 
-      chokidarWatcher.emit('add', '/home/user/project/a.png');
-      chokidarWatcher.emit('add', '/home/user/project/b.png');
+      chokidarWatcher.emit('add', '/home/user/project/a.jpg');
+      chokidarWatcher.emit('add', '/home/user/project/b.jpg');
       vi.advanceTimersByTime(300);
 
       expect(handler).toHaveBeenCalledTimes(2);
@@ -306,7 +339,7 @@ describe('ImageWatcher', () => {
 
       // Emit 25 unique images in quick succession
       for (let i = 0; i < 25; i++) {
-        chokidarWatcher.emit('add', `/home/user/project/img${i}.png`);
+        chokidarWatcher.emit('add', `/home/user/project/img${i}.jpg`);
         vi.advanceTimersByTime(250); // past debounce, within burst window
       }
 
@@ -323,7 +356,7 @@ describe('ImageWatcher', () => {
 
       // Fill up burst limit
       for (let i = 0; i < 20; i++) {
-        chokidarWatcher.emit('add', `/home/user/project/img${i}.png`);
+        chokidarWatcher.emit('add', `/home/user/project/img${i}.jpg`);
         vi.advanceTimersByTime(250);
       }
       expect(handler).toHaveBeenCalledTimes(20);
@@ -332,7 +365,7 @@ describe('ImageWatcher', () => {
       vi.advanceTimersByTime(11_000);
 
       // Should accept new images
-      chokidarWatcher.emit('add', '/home/user/project/new.png');
+      chokidarWatcher.emit('add', '/home/user/project/new.jpg');
       vi.advanceTimersByTime(300);
 
       expect(handler).toHaveBeenCalledTimes(21);
diff --git a/test/routes/file-routes-attachment-path-guard.test.ts b/test/routes/file-routes-attachment-path-guard.test.ts
new file mode 100644
index 00000000..258335b9
--- /dev/null
+++ b/test/routes/file-routes-attachment-path-guard.test.ts
@@ -0,0 +1,324 @@
+/**
+ * @fileoverview COD-53 — attachment path-traversal / sensitive-file guard.
+ *
+ * Verifies the sensitive-path blocklist is enforced at:
+ *  - attachment registration (POST /api/sessions/:id/attachments)
+ *  - raw / preview / thumbnail serving (defense-in-depth against a record that
+ *    was crafted or registered before the guard existed)
+ * while still allowing legitimate cross-workspace attachment (codeman-publish
+ * skill + the ~/.codeman review-card loop) to succeed.
+ *
+ * Uses app.inject() — no real HTTP ports needed.
+ * Port: N/A (app.inject doesn't open ports)
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import { Readable } from 'node:stream';
+import { homedir } from 'node:os';
+import { createRouteTestHarness, type RouteTestHarness } from './_route-test-utils.js';
+import { registerFileRoutes } from '../../src/web/routes/file-routes.js';
+
+// Mock fs/promises for file operations
+vi.mock('node:fs/promises', () => ({
+  default: {
+    readdir: vi.fn(async () => []),
+    readFile: vi.fn(async () => 'file content'),
+    writeFile: vi.fn(async () => undefined),
+    stat: vi.fn(async () => ({ size: 100, isFile: () => true, mtimeMs: 1 })),
+    mkdir: vi.fn(async () => undefined),
+    mkdtemp: vi.fn(async () => '/tmp/codeman-preview-test'),
+    rename: vi.fn(async () => undefined),
+    rm: vi.fn(async () => undefined),
+  },
+}));
+
+// Mock realpathSync for symlink resolution (identity by default)
+vi.mock('node:fs', async (importOriginal) => {
+  const actual = await importOriginal<typeof import('node:fs')>();
+  return {
+    ...actual,
+    realpathSync: vi.fn((p: string) => p),
+    createReadStream: vi.fn(() => Readable.from([Buffer.from('file content')])),
+  };
+});
+
+vi.mock('../../src/file-stream-manager.js', () => ({
+  fileStreamManager: {
+    createStream: vi.fn(async () => ({ success: true, streamId: 'stream-1' })),
+    closeStream: vi.fn(() => true),
+  },
+}));
+
+import fs from 'node:fs/promises';
+import { createReadStream, realpathSync } from 'node:fs';
+import { attachmentRegistry, type AttachmentRecord } from '../../src/attachment-registry.js';
+
+const mockedStat = vi.mocked(fs.stat);
+const mockedRealpathSync = vi.mocked(realpathSync);
+const mockedCreateReadStream = vi.mocked(createReadStream);
+
+describe('file-routes attachment path guard (COD-53)', () => {
+  let harness: RouteTestHarness;
+
+  beforeEach(async () => {
+    harness = await createRouteTestHarness(registerFileRoutes);
+    vi.clearAllMocks();
+    attachmentRegistry.clearSession('test-session-1');
+    mockedRealpathSync.mockImplementation((p: string) => p as never);
+    mockedStat.mockResolvedValue({ size: 100, isFile: () => true, mtimeMs: 1 } as never);
+    mockedCreateReadStream.mockReturnValue(Readable.from([Buffer.from('file content')]) as never);
+  });
+
+  afterEach(async () => {
+    await harness.app.close();
+    attachmentRegistry.clearSession(harness.ctx._sessionId);
+    // Reset attachment-guard env knobs so one test can't leak into the next.
+    delete process.env.CODEMAN_ATTACHMENT_BLOCKED_PATHS;
+    delete process.env.CODEMAN_ATTACHMENT_CONFINE;
+  });
+
+  // ===== BLOCK: registration rejects a sensitive path =====
+
+  it('rejects registering a .env file that carries a supported extension', async () => {
+    // A dotenv-style secret file named with a supported extension still leaks
+    // secrets; the blocklist's /\.env\./ pattern catches `.env.<ext>`.
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/home/someone/project/.env.txt' },
+    });
+
+    expect(res.statusCode).toBe(403);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(false);
+  });
+
+  it('rejects registering an SSH key path even with a supported extension', async () => {
+    const sshTxt = `${homedir()}/.ssh/id_rsa.txt`;
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: sshTxt },
+    });
+
+    expect(res.statusCode).toBe(403);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(false);
+  });
+
+  it('rejects registering a sensitive path that a symlink resolves to', async () => {
+    // The requested path looks innocent (.md) but realpath resolves it to an SSH key dir.
+    mockedRealpathSync.mockReturnValue(`${homedir()}/.ssh/known_hosts.md` as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/home/someone/project/innocent.md' },
+    });
+
+    expect(res.statusCode).toBe(403);
+  });
+
+  // ===== BLOCK (defense-in-depth): raw serving rejects a sensitive record =====
+
+  it('refuses to serve raw bytes for a record whose path is sensitive', async () => {
+    // Simulate a record that was registered before the guard existed (or crafted).
+    const record: AttachmentRecord = {
+      attachmentId: 'att_sensitive',
+      sessionId: harness.ctx._sessionId,
+      filePath: `${homedir()}/.ssh/id_rsa.txt`,
+      fileName: 'id_rsa.txt',
+      extension: 'txt',
+      attachmentType: 'text',
+      size: 100,
+      mtimeMs: 1,
+      timestamp: Date.now(),
+      source: 'external',
+    };
+    attachmentRegistry.register(record);
+
+    const res = await harness.app.inject({
+      method: 'GET',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments/att_sensitive/raw`,
+    });
+
+    expect(res.statusCode).toBe(403);
+    expect(mockedCreateReadStream).not.toHaveBeenCalled();
+  });
+
+  // ===== PRESERVE: legitimate cross-workspace attachment still works =====
+
+  it('still registers a normal cross-workspace file (codeman-publish / loop review card)', async () => {
+    mockedStat.mockResolvedValue({ size: 512, isFile: () => true, mtimeMs: 5 } as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: `${homedir()}/.codeman/jira-autoloop-questions.md` },
+    });
+
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(true);
+    expect(body.data.fileName).toBe('jira-autoloop-questions.md');
+    expect(body.data.extension).toBe('md');
+  });
+
+  it('still registers an arbitrary project-dir file (WSL path)', async () => {
+    mockedStat.mockResolvedValue({ size: 4096, isFile: () => true, mtimeMs: 5 } as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/mnt/c/decks/board-update.pdf' },
+    });
+
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(true);
+    expect(body.data.fileName).toBe('board-update.pdf');
+  });
+
+  it('still serves raw bytes for a legitimately registered cross-workspace file', async () => {
+    const content = Buffer.from('# notes');
+    mockedCreateReadStream.mockReturnValue(Readable.from([content]) as never);
+    mockedStat.mockResolvedValue({ size: content.length, isFile: () => true, mtimeMs: 5 } as never);
+
+    const registerRes = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: `${homedir()}/.codeman/review-card.md` },
+    });
+    const attachmentId = JSON.parse(registerRes.body).data.attachmentId;
+
+    const rawRes = await harness.app.inject({
+      method: 'GET',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments/${attachmentId}/raw`,
+    });
+
+    expect(rawRes.statusCode).toBe(200);
+    expect(rawRes.headers['content-type']).toBe('text/markdown');
+  });
+
+  // ===== BLOCK (broadened defaults): /root and /etc trees =====
+
+  it('rejects registering a file anywhere under /root by default', async () => {
+    // /root is the root account home — blocked as a whole tree by default,
+    // even for an ordinary-looking note with a supported extension.
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/root/secret-notes.md' },
+    });
+
+    expect(res.statusCode).toBe(403);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(false);
+  });
+
+  it('rejects registering a file anywhere under /etc by default', async () => {
+    // The whole /etc tree is blocked by default (not just /etc/shadow).
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/etc/codeman/config-dump.txt' },
+    });
+
+    expect(res.statusCode).toBe(403);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(false);
+  });
+
+  it('does not block a lookalike sibling dir like /etcetera (separator-aware)', async () => {
+    // The /etc tree block must be path-separator-aware so an unrelated
+    // /etcetera/... path is NOT caught by accident.
+    mockedStat.mockResolvedValue({ size: 10, isFile: () => true, mtimeMs: 5 } as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/etcetera/notes.md' },
+    });
+
+    expect(res.statusCode).toBe(200);
+  });
+
+  // ===== CONFIG: extend the blocked set via env =====
+
+  it('rejects a path added via the extra-blocked-paths config', async () => {
+    process.env.CODEMAN_ATTACHMENT_BLOCKED_PATHS = '/srv/secrets,/data/private';
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/srv/secrets/keys.pdf' },
+    });
+
+    expect(res.statusCode).toBe(403);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(false);
+  });
+
+  it('still allows a normal path NOT in the configured blocked set', async () => {
+    process.env.CODEMAN_ATTACHMENT_BLOCKED_PATHS = '/srv/secrets,/data/private';
+    mockedStat.mockResolvedValue({ size: 20, isFile: () => true, mtimeMs: 5 } as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/srv/public/report.pdf' },
+    });
+
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(true);
+    expect(body.data.fileName).toBe('report.pdf');
+  });
+
+  // ===== CONFINEMENT MODE ON (opt-in) =====
+
+  it('confinement ON: rejects a file OUTSIDE the session workspace', async () => {
+    process.env.CODEMAN_ATTACHMENT_CONFINE = '1';
+    // Mock session workspace is /tmp/test-workdir; this file resolves elsewhere.
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: '/home/someone/elsewhere/report.pdf' },
+    });
+
+    expect(res.statusCode).toBe(403);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(false);
+  });
+
+  it('confinement ON: allows a file INSIDE the session workspace', async () => {
+    process.env.CODEMAN_ATTACHMENT_CONFINE = '1';
+    // Mock session workspace is /tmp/test-workdir (see MockSession).
+    const insidePath = '/tmp/test-workdir/docs/report.pdf';
+    mockedRealpathSync.mockReturnValue(insidePath as never);
+    mockedStat.mockResolvedValue({ size: 30, isFile: () => true, mtimeMs: 5 } as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: insidePath },
+    });
+
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(true);
+    expect(body.data.fileName).toBe('report.pdf');
+  });
+
+  // ===== CONFINEMENT OFF (default) regression: legit cross-workspace attach =====
+
+  it('confinement OFF (default): legit cross-workspace attach still succeeds', async () => {
+    // No CODEMAN_ATTACHMENT_CONFINE set → default OFF. A ~/.codeman review-card
+    // file lives OUTSIDE the /tmp/test-workdir session workspace and must still
+    // attach (protects codeman-publish + the loop's review-card channel).
+    mockedStat.mockResolvedValue({ size: 64, isFile: () => true, mtimeMs: 5 } as never);
+    const res = await harness.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${harness.ctx._sessionId}/attachments`,
+      payload: { path: `${homedir()}/.codeman/jira-autoloop-questions.md` },
+    });
+
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.success).toBe(true);
+    expect(body.data.fileName).toBe('jira-autoloop-questions.md');
+  });
+});