diff --git a/src/main/services/agent-read-messages.ts b/src/main/services/agent-read-messages.ts
index 9b7f901a..15ae4d2a 100644
--- a/src/main/services/agent-read-messages.ts
+++ b/src/main/services/agent-read-messages.ts
@@ -2,11 +2,24 @@ import { optionalString } from "./agent-tool-args";
 import type { AgentToolContext, AgentToolDeps } from "./agent-tools";
 import type { JsonRecord } from "./provider-http";
 
+interface MessageFilter {
+  before: { createdAt: string; rowid: number } | null;
+  query: string | null;
+  limit: number;
+}
+
 export function readMessagesTool(deps: AgentToolDeps, ctx: AgentToolContext, args: JsonRecord): string {
   const channel = optionalString(args.channel);
   const withTeammate = optionalString(args.with);
-  const limit = Math.min(Math.max(Number(args.limit) || 10, 1), 30);
-  if (channel && withTeammate) throw new Error('Pass either "channel" or "with", not both.');
+  const threadId = optionalString(args.thread_id);
+  if ([channel, withTeammate, threadId].filter(Boolean).length > 1) {
+    throw new Error('Pass only one of "channel", "with", or "thread_id".');
+  }
+  const filter: MessageFilter = {
+    before: beforeCursor(deps, ctx.orgId, optionalString(args.before)),
+    query: optionalString(args.query),
+    limit: Math.min(Math.max(Number(args.limit) || 10, 1), 30),
+  };
   if (withTeammate) {
     const counterpart = deps.db.prepare(`
       select id, name, 'agent' as kind from agents where org_id = ? and lower(name) = lower(?) and lifecycle = 'active'
@@ -20,19 +33,54 @@ export function readMessagesTool(deps: AgentToolDeps, ctx: AgentToolContext, arg
       { type: "agent", id: ctx.agent.id },
       { type: counterpart.kind, id: counterpart.id },
     );
-    const rows = recentMessagesIn(deps, ctx.orgId, spaceId, limit);
-    if (rows.length === 0) return `No messages yet in your direct conversation with ${counterpart.name}.`;
-    return rows.map((m) => `[${m.sender_name}] (thread=${m.thread_id}): ${m.body_md}`).join("\n");
+    return messagePage(deps, ctx.orgId, { column: "space_id", id: spaceId }, filter, `your direct conversation with ${counterpart.name}`);
   }
   if (channel) {
     const space = deps.db.prepare(
       "select id from chat_spaces where org_id = ? and lower(name) = lower(?) and space_type <> 'direct' limit 1",
     ).get(ctx.orgId, channel) as { id: string } | undefined;
     if (!space) throw new Error(`No channel named "${channel}".`);
-    const rows = recentMessagesIn(deps, ctx.orgId, space.id, limit);
-    if (rows.length === 0) return `No recent messages in #${channel}.`;
-    return rows.map((m) => `[${m.sender_name}] (thread=${m.thread_id}): ${m.body_md}`).join("\n");
+    return messagePage(deps, ctx.orgId, { column: "space_id", id: space.id }, filter, `#${channel}`);
   }
+  if (threadId) {
+    const thread = deps.db.prepare("select id from chat_threads where id = ? and org_id = ?").get(threadId, ctx.orgId);
+    if (!thread) throw new Error(`No thread with thread_id "${threadId}".`);
+    return messagePage(deps, ctx.orgId, { column: "thread_id", id: threadId }, filter, `thread ${threadId}`);
+  }
+  return unansweredMentions(deps, ctx, filter.limit);
+}
+
+function messagePage(
+  deps: AgentToolDeps,
+  orgId: string,
+  scope: { column: "space_id" | "thread_id"; id: string },
+  filter: MessageFilter,
+  label: string,
+): string {
+  const rows = deps.db.prepare(`
+    select m.id, m.rowid as row_id, m.body_md, m.created_at, m.thread_id,
+           coalesce(a.name, e.display_name, m.sender_type) as sender_name
+    from chat_messages m
+    left join agents a on a.id = m.sender_id and m.sender_type = 'agent'
+    left join employees e on e.id = m.sender_id and m.sender_type = 'employee'
+    where m.${scope.column} = ? and m.org_id = ? and m.deleted_at is null
+      and (? is null or m.created_at < ? or (m.created_at = ? and m.rowid < ?))
+      and (? is null or instr(lower(m.body_md), lower(?)) > 0)
+    order by m.created_at desc, m.rowid desc
+    limit ?
+  `).all(
+    scope.id, orgId,
+    filter.before?.createdAt ?? null, filter.before?.createdAt ?? null, filter.before?.createdAt ?? null, filter.before?.rowid ?? null,
+    filter.query, filter.query, filter.limit + 1,
+  ) 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}): ${m.body_md}`);
+  if (rows.length > filter.limit) lines.unshift(`(Older messages exist: pass before="${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,
            coalesce(a.name, e.display_name, m.sender_type) as sender_name,
@@ -58,22 +106,20 @@ export function readMessagesTool(deps: AgentToolDeps, ctx: AgentToolContext, arg
   }).join("\n");
 }
 
-function recentMessagesIn(
-  deps: AgentToolDeps,
-  orgId: string,
-  spaceId: string,
-  limit: number,
-): Array<{ body_md: string; sender_name: string; thread_id: string }> {
-  const rows = deps.db.prepare(`
-    select m.body_md,
-           coalesce(a.name, e.display_name, m.sender_type) as sender_name,
-           m.thread_id
-    from chat_messages m
-    left join agents a on a.id = m.sender_id and m.sender_type = 'agent'
-    left join employees e on e.id = m.sender_id and m.sender_type = 'employee'
-    where m.space_id = ? and m.org_id = ? and m.deleted_at is null
-    order by m.created_at desc
-    limit ?
-  `).all(spaceId, orgId, limit) as Array<{ body_md: string; sender_name: string; thread_id: string }>;
-  return rows.reverse();
+/** A message_id cursor from a previous page, or a UTC time. */
+function beforeCursor(deps: AgentToolDeps, orgId: string, text: string | null): MessageFilter["before"] {
+  if (!text) return null;
+  if (text.startsWith("msg_")) {
+    const row = deps.db.prepare("select created_at, rowid as row_id from chat_messages where id = ? and org_id = ?")
+      .get(text, orgId) as { created_at: string; row_id: number } | undefined;
+    if (!row) throw new Error(`No message with id "${text}".`);
+    return { createdAt: row.created_at, rowid: row.row_id };
+  }
+  const match = /^(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2})(\.\d{3})?Z$/.exec(text);
+  const normalized = match ? `${match[1]}${match[2] ?? ".000"}Z` : "";
+  const time = new Date(normalized);
+  if (!match || Number.isNaN(time.getTime()) || time.toISOString() !== normalized) {
+    throw new Error(`"before" must be a message_id from a previous page or a UTC ISO timestamp like 2026-01-31T09:00:00Z, got "${text}".`);
+  }
+  return { createdAt: normalized, rowid: -1 };
 }
diff --git a/src/main/services/agent-tools.ts b/src/main/services/agent-tools.ts
index 58dc407d..3fdfb635 100644
--- a/src/main/services/agent-tools.ts
+++ b/src/main/services/agent-tools.ts
@@ -135,14 +135,17 @@ export const AGENT_TOOLS: ToolDefinition[] = [
   },
   {
     name: "read_messages",
-    description: "Read recent messages from a channel, a direct conversation, or (with no arguments) the mentions you have not answered in their thread yet. Check what your teammates have been saying before you respond or start work.",
+    description: "Read messages from a channel, a direct conversation, or one thread — newest first page, with before= to page back and query= to search — or, with no arguments, the mentions you have not answered in their thread yet.",
     parameters: {
       type: "object",
       additionalProperties: false,
       properties: {
         channel: { type: "string", description: "Channel name: 'engineering', 'product', 'general'." },
         with: { type: "string", description: "Teammate name to read your direct conversation with, e.g. 'CEO'." },
-        limit: { type: "number", description: "Number of recent messages (default 10, max 30)." },
+        thread_id: { type: "string", description: "Read one thread, e.g. a thread_id from a message or handoff." },
+        before: { type: "string", description: "Page back: the message_id a previous page told you to pass, or a UTC ISO timestamp." },
+        query: { type: "string", description: "Only messages containing this text (case-insensitive)." },
+        limit: { type: "number", description: "Number of messages (default 10, max 30)." },
       },
       required: [],
     },
diff --git a/tests/unit/agent-direct-messages.test.ts b/tests/unit/agent-direct-messages.test.ts
index 9e55a116..90ba5fc0 100644
--- a/tests/unit/agent-direct-messages.test.ts
+++ b/tests/unit/agent-direct-messages.test.ts
@@ -153,6 +153,6 @@ describe("agent direct messages", () => {
     dispatchAgentTool(deps, h.ctx, call("send_message", { to: "Dana", body: "Morning - priorities for today are in the doc." }));
     const readBack = dispatchAgentTool(deps, h.ctx, call("read_messages", { with: "Dana" }));
     expect(readBack).toContain("priorities for today");
-    expect(readBack).toContain("[CEO]");
+    expect(readBack).toMatch(/\] CEO \(thread=/);
   });
 });
diff --git a/tests/unit/mention-resolution.test.ts b/tests/unit/mention-resolution.test.ts
index 90371654..5f90f611 100644
--- a/tests/unit/mention-resolution.test.ts
+++ b/tests/unit/mention-resolution.test.ts
@@ -144,3 +144,63 @@ describe("mention resolution", () => {
     expect(dispatchAgentTool(deps, danaCtx, call("read_messages", {}))).toContain("status on the rollback");
   });
 });
+
+describe("read_messages history access", () => {
+  test("reads one thread, pages back with before, and searches with query", () => {
+    const connection = new DatabaseConnection(join(tmpdir(), `ac-history-${randomUUID()}.db`));
+    const organization = new OrganizationService(connection.db);
+    let orgId = "";
+    let ceoId = "";
+    connection.transaction(() => {
+      orgId = organization.createOrganization({ organizationName: "HistCorp", employeeName: "Yang", mission: "m", goal: "g" });
+      const providerId = (connection.db.prepare("select id from providers where org_id = ? and provider_key = 'openai'").get(orgId) as { id: string }).id;
+      ceoId = organization.createAgent({
+        orgId, name: "CEO", role: "CEO", department: "Executive",
+        modelProviderId: providerId, modelId: "gpt-5.4", budgetCents: 25000, managerAgentId: null,
+      });
+    });
+    const deps = { db: connection.db, organization, chat: new ChatService(connection.db) };
+    const ctx: AgentToolContext = {
+      orgId, agent: { id: ceoId, modelProviderId: null, modelId: null },
+      taskProjectId: null, taskGoalId: null, taskId: null, sourceThreadId: null, workspace: null,
+    };
+    const first = dispatchAgentTool(deps, ctx, call("send_message", { channel: "general", body: "Decision 0: use Postgres" }));
+    const threadId = /thread_id="([^"]+)"/.exec(first)![1];
+    for (let index = 1; index <= 14; index += 1) {
+      dispatchAgentTool(deps, ctx, call("send_message", { channel: "general", body: `Decision ${index}`, thread_id: threadId }));
+    }
+    dispatchAgentTool(deps, ctx, call("send_message", { channel: "general", body: "Unrelated chatter" }));
+    connection.db.prepare("update chat_messages set created_at = '2026-01-01T00:00:' || printf('%02d', rowid) || '.000Z'").run();
+
+    const page = dispatchAgentTool(deps, ctx, call("read_messages", { thread_id: threadId, limit: 5 }));
+    expect(page).not.toContain("Unrelated chatter");
+    expect(page).toContain("Decision 14");
+    expect(page).not.toContain("Decision 9");
+    const before = /before="([^"]+)"/.exec(page)![1];
+    const older = dispatchAgentTool(deps, ctx, call("read_messages", { thread_id: threadId, limit: 5, before }));
+    expect(older).toContain("Decision 9");
+    expect(older).not.toContain("Decision 10");
+
+    const found = dispatchAgentTool(deps, ctx, call("read_messages", { channel: "general", query: "postgres" }));
+    expect(found).toContain("Decision 0: use Postgres");
+    expect(found).not.toContain("Decision 1");
+    expect(dispatchAgentTool(deps, ctx, call("read_messages", { thread_id: threadId, channel: "general" }))).toContain('Pass only one of');
+    for (const bad of ["yesterday", "2026-02-30T00:00:00.000Z", "2026-01-01 00:00:00", "2026-01-01T00:00:00+08:00"]) {
+      expect(dispatchAgentTool(deps, ctx, call("read_messages", { channel: "general", before: bad }))).toContain('"before" must be a message_id from a previous page or a UTC ISO timestamp');
+    }
+    expect(dispatchAgentTool(deps, ctx, call("read_messages", { thread_id: threadId, before: "2026-01-01T00:00:03Z" }))).toContain("Decision 1");
+
+    // Messages sharing one timestamp still page through completely.
+    connection.db.prepare("update chat_messages set created_at = '2026-01-01T00:00:00.000Z' where thread_id = ?").run(threadId);
+    const seen = new Set<string>();
+    let cursor: string | undefined;
+    for (let pageIndex = 0; pageIndex < 5; pageIndex += 1) {
+      const result = dispatchAgentTool(deps, ctx, call("read_messages", { thread_id: threadId, limit: 4, ...(cursor ? { before: cursor } : {}) }));
+      for (const match of result.matchAll(/: (Decision \d+)/g)) seen.add(match[1].split(":")[0]);
+      cursor = /before="([^"]+)"/.exec(result)?.[1];
+      if (!cursor) break;
+    }
+    expect(seen.size).toBe(15);
+    connection.close();
+  });
+});