diff --git a/src/main/services/agent-attachment-tools.ts b/src/main/services/agent-attachment-tools.ts
new file mode 100644
index 00000000..fcee5ed5
--- /dev/null
+++ b/src/main/services/agent-attachment-tools.ts
@@ -0,0 +1,54 @@
+import type { DatabaseSync } from "node:sqlite";
+import { readFileSync } from "node:fs";
+import { FILE_SCAN_STATE } from "../../shared/domain";
+import { requireString } from "./agent-tool-args";
+import type { AgentToolContext, AgentToolDeps } from "./agent-tools";
+import type { JsonRecord } from "./provider-http";
+import type { ToolDefinition } from "./provider-tool-turn";
+
+const ATTACHMENT_CHAR_LIMIT = 24_000;
+
+export const ATTACHMENT_TOOLS: ToolDefinition[] = [
+  {
+    name: "read_attachment",
+    description: "Read a file attached to a message or handed off to you, by the file_id shown next to the message.",
+    parameters: {
+      type: "object",
+      additionalProperties: false,
+      properties: { file_id: { type: "string" } },
+      required: ["file_id"],
+    },
+  },
+];
+
+/** " [attachments: a.md (file_id=…)]" for a message, or "". */
+export function attachmentNote(db: DatabaseSync, messageId: string): string {
+  const files = db.prepare(`
+    select f.id, f.name from chat_attachments ca join file_objects f on f.id = ca.file_id
+    where ca.message_id = ? order by f.name
+  `).all(messageId) as Array<{ id: string; name: string }>;
+  if (files.length === 0) return "";
+  return ` [attachments: ${files.map((file) => `${file.name} (file_id=${file.id})`).join(", ")}]`;
+}
+
+export function readAttachmentTool(deps: AgentToolDeps, ctx: AgentToolContext, args: JsonRecord): string {
+  const fileId = requireString(args.file_id, "file_id");
+  const file = deps.db.prepare("select name, storage_path, scan_state from file_objects where id = ? and org_id = ?")
+    .get(fileId, ctx.orgId) as { name: string; storage_path: string; scan_state: string } | undefined;
+  if (!file) throw new Error(`No file with file_id "${fileId}".`);
+  if (file.scan_state !== FILE_SCAN_STATE.APPROVED) throw new Error(`${file.name} was blocked by the file scan and cannot be read.`);
+  const bytes = readFileSync(file.storage_path);
+  const content = utf8Text(bytes);
+  if (content === null) return `${file.name} is a binary file (${bytes.length} bytes); it has no text to read.`;
+  if (content.length <= ATTACHMENT_CHAR_LIMIT) return content;
+  return `${content.slice(0, ATTACHMENT_CHAR_LIMIT)}\n\n[truncated: showing the first ${ATTACHMENT_CHAR_LIMIT} of ${content.length} characters]`;
+}
+
+function utf8Text(bytes: Buffer): string | null {
+  if (bytes.includes(0)) return null;
+  try {
+    return new TextDecoder("utf-8", { fatal: true }).decode(bytes);
+  } catch {
+    return null;
+  }
+}
diff --git a/src/main/services/agent-read-messages.ts b/src/main/services/agent-read-messages.ts
index 15ae4d2a..fc929d65 100644
--- a/src/main/services/agent-read-messages.ts
+++ b/src/main/services/agent-read-messages.ts
@@ -1,3 +1,4 @@
+import { attachmentNote } from "./agent-attachment-tools";
 import { optionalString } from "./agent-tool-args";
 import type { AgentToolContext, AgentToolDeps } from "./agent-tools";
 import type { JsonRecord } from "./provider-http";
@@ -75,14 +76,14 @@ function messagePage(
   ) as Array<{ id: string; row_id: number; body_md: string; created_at: string; thread_id: string; sender_name: string }>;
   if (rows.length === 0) return `No messages${filter.query ? ` matching "${filter.query}"` : ""}${filter.before ? " before that point" : ""} in ${label}.`;
   const page = rows.slice(0, filter.limit).reverse();
-  const lines = page.map((m) => `[${m.created_at}] ${m.sender_name} (thread=${m.thread_id}): ${m.body_md}`);
+  const lines = page.map((m) => `[${m.created_at}] ${m.sender_name} (thread=${m.thread_id}): ${m.body_md}${attachmentNote(deps.db, m.id)}`);
   if (rows.length > filter.limit) lines.unshift(`(Older messages exist: pass before="${page[0].id}" to read them.)`);
   return lines.join("\n");
 }
 
 function unansweredMentions(deps: AgentToolDeps, ctx: AgentToolContext, limit: number): string {
   const rows = deps.db.prepare(`
-    select m.body_md,
+    select m.id, m.body_md,
            coalesce(a.name, e.display_name, m.sender_type) as sender_name,
            m.thread_id, s.name as channel_name, s.space_type
     from chat_mentions cm
@@ -98,11 +99,11 @@ function unansweredMentions(deps: AgentToolDeps, ctx: AgentToolContext, limit: n
       )
     order by m.created_at desc
     limit ?
-  `).all(ctx.agent.id, ctx.orgId, limit) as Array<{ body_md: string; sender_name: string; thread_id: string; channel_name: string; space_type: string }>;
+  `).all(ctx.agent.id, ctx.orgId, limit) as Array<{ id: string; body_md: string; sender_name: string; thread_id: string; channel_name: string; space_type: string }>;
   if (rows.length === 0) return "No unanswered mentions.";
   return rows.reverse().map((m) => {
     const where = m.space_type === "direct" ? "in your direct conversation" : `in #${m.channel_name}`;
-    return `[${m.sender_name} ${where}] (thread=${m.thread_id}): ${m.body_md}`;
+    return `[${m.sender_name} ${where}] (thread=${m.thread_id}): ${m.body_md}${attachmentNote(deps.db, m.id)}`;
   }).join("\n");
 }
 
diff --git a/src/main/services/agent-tools.ts b/src/main/services/agent-tools.ts
index 3fdfb635..1d5c8d2c 100644
--- a/src/main/services/agent-tools.ts
+++ b/src/main/services/agent-tools.ts
@@ -10,6 +10,7 @@ import { grantConnectorTool, listConnectorsTool } from "./agent-connector-tools"
 import { bindSkillSlugs, grantSkillTool, listSkillsTool } from "./agent-skill-tools";
 import { createDocumentTool, writeDeliverableTool } from "./agent-deliverable-tools";
 import { companyStatusTool, GOAL_TOOLS, updateGoalTool } from "./agent-goal-tools";
+import { ATTACHMENT_TOOLS, readAttachmentTool } from "./agent-attachment-tools";
 import { sendMessageTool } from "./agent-send-message";
 import { withSavepoint } from "../database/connection";
 import { optionalString, optionalStringArray, requireString } from "./agent-tool-args";
@@ -227,6 +228,7 @@ export const AGENT_TOOLS: ToolDefinition[] = [
     },
   },
   ...GOAL_TOOLS,
+  ...ATTACHMENT_TOOLS,
 ];
 
 export function dispatchAgentTool(
@@ -257,6 +259,8 @@ export function dispatchAgentTool(
         return grantConnectorTool(deps, ctx, call.arguments, "grant");
       case "revoke_connector":
         return grantConnectorTool(deps, ctx, call.arguments, "revoke");
+      case "read_attachment":
+        return readAttachmentTool(deps, ctx, call.arguments);
       case "company_status":
         return companyStatusTool(deps, ctx);
       case "update_goal":
diff --git a/src/main/services/chat-wake-context.ts b/src/main/services/chat-wake-context.ts
index 3447d634..fd865b77 100644
--- a/src/main/services/chat-wake-context.ts
+++ b/src/main/services/chat-wake-context.ts
@@ -1,10 +1,11 @@
 import type { DatabaseSync } from "node:sqlite";
 import type { ChatContextBlock } from "./task-prompts";
+import { attachmentNote } from "./agent-attachment-tools";
 
 const HISTORY_LIMIT = 20;
 
 const MESSAGE_SELECT = `
-  select m.body_md, m.created_at, m.edited_at, m.sender_type, m.sender_id,
+  select m.id, m.body_md, m.created_at, m.edited_at, m.sender_type, m.sender_id,
          coalesce(a.name, e.display_name, m.sender_type) as sender_name,
          coalesce(a.role, e.role) as sender_role
   from chat_messages m
@@ -12,6 +13,7 @@ const MESSAGE_SELECT = `
   left join employees e on e.id = m.sender_id and m.sender_type = 'employee'`;
 
 interface ThreadMessageRow {
+  id: string;
   body_md: string;
   created_at: string;
   edited_at: string | null;
@@ -46,15 +48,15 @@ export function loadChatWakeContext(db: DatabaseSync, orgId: string, agentId: st
   return {
     threadId: scope.sourceThreadId,
     spaceId: thread.space_id,
-    history: [...(omitted > 0 ? [`(${omitted} earlier messages in this thread are not shown.)`] : []), ...history.map(formatMessage)].join("\n"),
-    fresh: fresh.map(formatMessage).join("\n"),
+    history: [...(omitted > 0 ? [`(${omitted} earlier messages in this thread are not shown.)`] : []), ...history.map((m) => formatMessage(db, m))].join("\n"),
+    fresh: fresh.map((m) => formatMessage(db, m)).join("\n"),
   };
 }
 
-function formatMessage(m: ThreadMessageRow): string {
+function formatMessage(db: DatabaseSync, m: ThreadMessageRow): string {
   const who = m.sender_role ? `${m.sender_name} (${m.sender_type}, ${m.sender_role})` : `${m.sender_name} (${m.sender_type})`;
   const edited = m.edited_at ? ` (edited ${utcMinute(m.edited_at)})` : "";
-  return `[${utcMinute(m.created_at)}] ${who}${edited}: ${m.body_md}`;
+  return `[${utcMinute(m.created_at)}] ${who}${edited}: ${m.body_md}${attachmentNote(db, m.id)}`;
 }
 
 function utcMinute(iso: string): string {
@@ -80,6 +82,6 @@ export function createRunMessagePoller(
     if (rows.length === 0) return null;
     watermark = rows[rows.length - 1].created_at;
     console.info(`[run-inbox] agent ${input.agentId}: ${rows.length} new message(s) injected mid-run`);
-    return ["Messages that arrived while you were working (they may change what you should do):", ...rows.map(formatMessage)].join("\n");
+    return ["Messages that arrived while you were working (they may change what you should do):", ...rows.map((m) => formatMessage(db, m))].join("\n");
   };
 }
diff --git a/tests/integration/chat-context.test.ts b/tests/integration/chat-context.test.ts
index ab1dddb3..9e86c4a3 100644
--- a/tests/integration/chat-context.test.ts
+++ b/tests/integration/chat-context.test.ts
@@ -1,4 +1,5 @@
 import { randomUUID } from "node:crypto";
+import { writeFileSync } from "node:fs";
 import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { describe, expect, test } from "vitest";
@@ -8,6 +9,8 @@ import { ProviderService } from "../../src/main/services/provider-service";
 import { providerAdapters } from "../../src/main/services/provider-adapters";
 import { TaskExecutionService } from "../../src/main/services/task-execution-service";
 import { ChatService } from "../../src/main/services/chat-service";
+import { OrganizationService } from "../../src/main/services/organization-service";
+import { dispatchAgentTool, type AgentToolContext } from "../../src/main/services/agent-tools";
 import { ensureCeoDirectSpace } from "../../src/main/services/ceo-direct-space";
 import { claimNextQueuedRun } from "../../src/main/app/task-queue-worker";
 import type { AgentTurnResult, ProviderToolTurnInput } from "../../src/main/services/provider-tool-turn";
@@ -51,8 +54,8 @@ async function founderLine() {
   const spaceId = ensureCeoDirectSpace(connection.db, orgId)!;
   const kickoff = claimNextQueuedRun(connection);
   await execution.executeRun(kickoff!.org_id, kickoff!.id);
-  const say = (bodyMd: string, threadId: string | null) => {
-    const id = chat.sendMessage({ orgId, spaceId, threadId, senderType: "employee", senderId: founderId, bodyMd, attachmentFileIds: [] });
+  const say = (bodyMd: string, threadId: string | null, attachmentFileIds: string[] = []) => {
+    const id = chat.sendMessage({ orgId, spaceId, threadId, senderType: "employee", senderId: founderId, bodyMd, attachmentFileIds });
     return (connection.db.prepare("select thread_id from chat_messages where id = ?").get(id) as { thread_id: string }).thread_id;
   };
   const runWake = async () => {
@@ -77,7 +80,17 @@ async function founderLine() {
     const row = connection.db.prepare("select id from chat_messages where body_md = ?").get(bodyMd) as { id: string };
     chat.deleteMessage({ orgId, messageId: row.id, actorType: "employee", actorId: founderId });
   };
-  return { connection, wakePrompts, wakeInputs, say, runWake, runManually, edit, remove, onWakeTurn };
+  const addFile = (name: string, content: string) => {
+    const path = join(tmpdir(), `ac-attach-${randomUUID()}-${name}`);
+    writeFileSync(path, content);
+    const fileId = `fil_${randomUUID()}`;
+    connection.db.prepare(`
+      insert into file_objects(id, org_id, name, kind, size_bytes, sha256, storage_path, owner_type, owner_id, created_at)
+      values (?, ?, ?, 'md', ?, 'x', ?, 'employee', ?, ?)
+    `).run(fileId, orgId, name, content.length, path, founderId, new Date().toISOString());
+    return fileId;
+  };
+  return { connection, orgId, ceoId, wakePrompts, wakeInputs, say, runWake, runManually, edit, remove, onWakeTurn, addFile };
 }
 
 describe("chat wake context", () => {
@@ -257,4 +270,21 @@ describe("chat wake context", () => {
     expect(h.connection.db.prepare("select count(*) as n from tasks where title like '%99-1234%' or description like '%99-1234%'").get()).toEqual({ n: 0 });
     h.connection.close();
   });
+
+  test("attachments travel with the message and can be read by file_id", async () => {
+    const h = await founderLine();
+    const fileId = h.addFile("spec.md", "# Spec\nShip the booking API by Friday.");
+    h.say("Please review the attached spec.", null, [fileId]);
+    await h.runWake();
+    expect(h.wakePrompts[0]).toContain(`Please review the attached spec. [attachments: spec.md (file_id=${fileId})]`);
+
+    const deps = { db: h.connection.db, organization: new OrganizationService(h.connection.db), chat: new ChatService(h.connection.db) };
+    const ctx: AgentToolContext = {
+      orgId: h.orgId, agent: { id: h.ceoId, modelProviderId: null, modelId: null },
+      taskProjectId: null, taskGoalId: null, taskId: null, sourceThreadId: null, workspace: null,
+    };
+    expect(dispatchAgentTool(deps, ctx, { id: "c1", name: "read_messages", arguments: { with: "Yang" } })).toContain(`[attachments: spec.md (file_id=${fileId})]`);
+    expect(dispatchAgentTool(deps, ctx, { id: "c2", name: "read_attachment", arguments: { file_id: fileId } })).toContain("Ship the booking API by Friday.");
+    h.connection.close();
+  });
 });
diff --git a/tests/unit/agent-attachment-tools.test.ts b/tests/unit/agent-attachment-tools.test.ts
new file mode 100644
index 00000000..7b1a9c85
--- /dev/null
+++ b/tests/unit/agent-attachment-tools.test.ts
@@ -0,0 +1,62 @@
+import { randomUUID } from "node:crypto";
+import { writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { describe, expect, test } from "vitest";
+import { DatabaseConnection } from "../../src/main/database/connection";
+import { OrganizationService } from "../../src/main/services/organization-service";
+import { ChatService } from "../../src/main/services/chat-service";
+import { dispatchAgentTool, type AgentToolContext } from "../../src/main/services/agent-tools";
+
+function harness() {
+  const connection = new DatabaseConnection(join(tmpdir(), `ac-attach-${randomUUID()}.db`));
+  const organization = new OrganizationService(connection.db);
+  let orgId = "";
+  let otherOrgId = "";
+  connection.transaction(() => {
+    orgId = organization.createOrganization({ organizationName: "A", employeeName: "Yang", mission: "m", goal: "g" });
+    otherOrgId = organization.createOrganization({ organizationName: "B", employeeName: "Lee", mission: "m", goal: "g" });
+  });
+  const addFile = (owner: string, name: string, content: string | Buffer, scanState = "approved") => {
+    const path = join(tmpdir(), `ac-attach-${randomUUID()}-${name}`);
+    writeFileSync(path, content);
+    const fileId = `fil_${randomUUID()}`;
+    connection.db.prepare(`
+      insert into file_objects(id, org_id, name, kind, size_bytes, sha256, storage_path, owner_type, owner_id, created_at, scan_state)
+      values (?, ?, ?, 'md', 1, 'x', ?, 'employee', null, ?, ?)
+    `).run(fileId, owner, name, path, new Date().toISOString(), scanState);
+    return fileId;
+  };
+  const ctx: AgentToolContext = {
+    orgId, agent: { id: "agt_x", modelProviderId: null, modelId: null },
+    taskProjectId: null, taskGoalId: null, taskId: null, sourceThreadId: null, workspace: null,
+  };
+  const read = (fileId: string) => dispatchAgentTool(
+    { db: connection.db, organization, chat: new ChatService(connection.db) },
+    ctx,
+    { id: "c", name: "read_attachment", arguments: { file_id: fileId } },
+  );
+  return { connection, orgId, otherOrgId, addFile, read };
+}
+
+describe("read_attachment", () => {
+  test("reads text, caps long files, and names binary files", () => {
+    const h = harness();
+    expect(h.read(h.addFile(h.orgId, "notes.md", "hello attachment"))).toBe("hello attachment");
+    const long = h.read(h.addFile(h.orgId, "big.md", "x".repeat(30_000)));
+    expect(long).toContain("[truncated: showing the first 24000 of 30000 characters]");
+    expect(h.read(h.addFile(h.orgId, "logo.png", Buffer.from([137, 80, 78, 71, 0, 1, 2])))).toBe("logo.png is a binary file (7 bytes); it has no text to read.");
+    expect(h.read(h.addFile(h.orgId, "blob.bin", Buffer.from([0x80, 0x81, 0xfe, 0xff])))).toBe("blob.bin is a binary file (4 bytes); it has no text to read.");
+    expect(h.read(h.addFile(h.orgId, "zh.md", "中文说明"))).toBe("中文说明");
+    h.connection.close();
+  });
+
+  test("refuses blocked files, unknown ids, and other companies' files", () => {
+    const h = harness();
+    expect(h.read(h.addFile(h.orgId, "virus.txt", "bad", "blocked"))).toBe("ERROR: virus.txt was blocked by the file scan and cannot be read.");
+    expect(h.read("fil_missing")).toBe('ERROR: No file with file_id "fil_missing".');
+    const foreign = h.addFile(h.otherOrgId, "secret.md", "other company");
+    expect(h.read(foreign)).toBe(`ERROR: No file with file_id "${foreign}".`);
+    h.connection.close();
+  });
+});