diff --git a/README.md b/README.md
index fc13ed56..8d53683b 100644
--- a/README.md
+++ b/README.md
@@ -28,8 +28,8 @@ The plugin depends on the experimental `codex app-server` API. Later Codex CLI r
 https://github.com/murashit/codex-panel
 ```
 
-4. Enable `Codex Panel` from Obsidian's Community plugins list.
-5. Open the panel from the ribbon or command palette.
+1. Enable `Codex Panel` from Obsidian's Community plugins list.
+2. Open the panel from the ribbon or command palette.
 
 ### Manual
 
@@ -72,6 +72,9 @@ The status dot in the panel opens connection controls, diagnostics, usage limits
 
 ## Slash Commands
 
+- `/new`: start a new Codex thread. Add text after the command to start the new thread and send that text immediately.
+- `/resume`: resume a recent Codex thread. Add a thread ID or use composer suggestions after `/resume` to choose a thread.
+- `/fork`: fork the active Codex thread.
 - `/compact`: request context compaction for the active thread.
 - `/fast`: toggle fast service tier for subsequent turns.
 - `/plan`: toggle Plan mode for subsequent turns. Add text after the command to toggle mode and send that text immediately, for example `/plan OK, implement it`.
diff --git a/src/app-server/client.ts b/src/app-server/client.ts
index 277bbffd..7dcf840d 100644
--- a/src/app-server/client.ts
+++ b/src/app-server/client.ts
@@ -10,6 +10,7 @@ import type { HooksListResponse } from "../generated/app-server/v2/HooksListResp
 import type { ModelListResponse } from "../generated/app-server/v2/ModelListResponse";
 import type { SkillsListResponse } from "../generated/app-server/v2/SkillsListResponse";
 import type { ThreadArchiveResponse } from "../generated/app-server/v2/ThreadArchiveResponse";
+import type { ThreadForkResponse } from "../generated/app-server/v2/ThreadForkResponse";
 import type { ThreadListResponse } from "../generated/app-server/v2/ThreadListResponse";
 import type { ThreadResumeResponse } from "../generated/app-server/v2/ThreadResumeResponse";
 import type { ThreadSetNameResponse } from "../generated/app-server/v2/ThreadSetNameResponse";
@@ -47,6 +48,7 @@ interface ClientResponseByMethod {
   "hooks/list": HooksListResponse;
   "thread/start": ThreadStartResponse;
   "thread/resume": ThreadResumeResponse;
+  "thread/fork": ThreadForkResponse;
   "thread/list": ThreadListResponse;
   "thread/archive": ThreadArchiveResponse;
   "thread/unarchive": ThreadUnarchiveResponse;
@@ -193,6 +195,15 @@ export class AppServerClient {
     });
   }
 
+  forkThread(threadId: string, cwd: string): Promise<ThreadForkResponse> {
+    return this.request("thread/fork", {
+      threadId,
+      cwd,
+      excludeTurns: true,
+      persistExtendedHistory: false,
+    });
+  }
+
   listThreads(cwd: string, archived = false): Promise<ThreadListResponse> {
     return this.request("thread/list", {
       cwd,
diff --git a/src/composer/suggestions.ts b/src/composer/suggestions.ts
index 1522397a..18411ff6 100644
--- a/src/composer/suggestions.ts
+++ b/src/composer/suggestions.ts
@@ -1,5 +1,8 @@
 import type { SkillMetadata } from "../generated/app-server/v2/SkillMetadata";
+import type { Thread } from "../generated/app-server/v2/Thread";
 import { SLASH_COMMANDS, type SlashCommandName } from "../panel/slash-commands";
+import { getThreadTitle } from "../threads";
+import { shortThreadId } from "../utils";
 
 export interface ComposerSuggestion {
   display: string;
@@ -23,9 +26,15 @@ export function parseSlashCommand(text: string): { command: SlashCommandName; ar
   return { command, args: match[2]?.trim() ?? "" };
 }
 
-export function activeComposerSuggestions(beforeCursor: string, notes: NoteCandidate[], skills: SkillMetadata[]): ComposerSuggestion[] {
+export function activeComposerSuggestions(
+  beforeCursor: string,
+  notes: NoteCandidate[],
+  skills: SkillMetadata[],
+  threads: Thread[] = [],
+): ComposerSuggestion[] {
   return (
     activeWikiLinkSuggestions(beforeCursor, notes) ??
+    activeThreadResumeSuggestions(beforeCursor, threads) ??
     activeSlashCommandSuggestions(beforeCursor) ??
     activeSkillSuggestions(beforeCursor, skills) ??
     []
@@ -119,6 +128,32 @@ export function activeSlashCommandSuggestions(beforeCursor: string): ComposerSug
     }));
 }
 
+export function activeThreadResumeSuggestions(beforeCursor: string, threads: Thread[]): ComposerSuggestion[] | null {
+  const match = beforeCursor.match(/(?:^|\n)\/resume\s+([^\n]{0,120})$/);
+  if (!match || match.index === undefined) return null;
+
+  const query = (match[1] ?? "").trim().toLowerCase();
+  const start = beforeCursor.length - (match[1]?.length ?? 0);
+  return threads
+    .map((thread, index) => {
+      const title = getThreadTitle(thread);
+      const id = thread.id.toLowerCase();
+      const normalizedTitle = title.toLowerCase();
+      const score = query.length === 0 ? 2 : id.startsWith(query) ? 0 : normalizedTitle.includes(query) ? 1 : id.includes(query) ? 2 : -1;
+      return { thread, title, score, index };
+    })
+    .filter((item) => item.score !== -1)
+    .sort((a, b) => a.score - b.score || a.index - b.index || a.title.localeCompare(b.title))
+    .slice(0, 8)
+    .map(({ thread, title }) => ({
+      display: title,
+      detail: shortThreadId(thread.id),
+      replacement: thread.id,
+      start,
+      appendSpaceOnInsert: true,
+    }));
+}
+
 export function activeSkillSuggestions(beforeCursor: string, skills: SkillMetadata[]): ComposerSuggestion[] | null {
   const match = beforeCursor.match(/(^|[\s([{])\$([^\s\])}]{0,120})$/);
   if (!match || match.index === undefined) return null;
diff --git a/src/main.ts b/src/main.ts
index 172d46d6..ba46aa78 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -511,6 +511,10 @@ class CodexPanelView extends ItemView {
     if (!this.client) return;
     return runSlashCommand(command, args, {
       activeThreadId: this.state.activeThreadId,
+      listedThreads: this.state.listedThreads,
+      startNewThread: () => this.startNewThread(),
+      resumeThread: (threadId) => this.resumeThread(threadId),
+      forkThread: (threadId) => this.forkThread(threadId),
       compactThread: async (threadId) => {
         await this.client?.compactThread(threadId);
       },
@@ -977,6 +981,39 @@ class CodexPanelView extends ItemView {
     }
   }
 
+  private async forkThread(threadId: string): Promise<void> {
+    if (this.state.busy) {
+      this.addSystemMessage("Finish or interrupt the current turn before forking threads.");
+      return;
+    }
+    await this.ensureConnected();
+    if (!this.client) return;
+
+    try {
+      const response = await this.client.forkThread(threadId, this.plugin.vaultPath);
+      this.state.activeThreadId = response.thread.id;
+      this.state.activeThreadCwd = response.cwd ?? response.thread.cwd ?? this.plugin.vaultPath;
+      this.state.activeTurnId = null;
+      this.state.activeModel = response.model ?? null;
+      this.state.activeServiceTier = response.serviceTier ?? null;
+      this.state.activeThreadCliVersion = response.thread.cliVersion ?? null;
+      this.state.tokenUsage = null;
+      this.state.displayItems = [];
+      this.state.historyCursor = null;
+      this.threadRename.resetThreadTurnPresence(false);
+      this.forceMessagesToBottom();
+      await this.refreshThreads();
+      await this.history.loadLatest(response.thread.id);
+      if (this.state.displayItems.length === 0) {
+        this.state.displayItems.push(this.systemItem(`Forked thread ${response.thread.id}`));
+        this.forceMessagesToBottom();
+      }
+      this.render();
+    } catch (error) {
+      this.addSystemMessage(error instanceof Error ? error.message : String(error));
+    }
+  }
+
   private forceMessagesToBottom(): void {
     this.state.messagesPinnedToBottom = true;
     this.forceScrollMessagesToBottomOnNextRender = true;
@@ -1202,7 +1239,12 @@ class CodexPanelView extends ItemView {
 
     const cursor = this.composer.selectionStart;
     const beforeCursor = this.composer.value.slice(0, cursor);
-    const suggestions = activeComposerSuggestions(beforeCursor, this.noteCandidates(), this.state.availableSkills);
+    const suggestions = activeComposerSuggestions(
+      beforeCursor,
+      this.noteCandidates(),
+      this.state.availableSkills,
+      this.state.listedThreads,
+    );
 
     this.state.composerSuggestions = suggestions;
     if (this.state.composerSuggestSelected >= this.state.composerSuggestions.length) {
diff --git a/src/panel/slash-commands.ts b/src/panel/slash-commands.ts
index 9b1c9f8b..e406c757 100644
--- a/src/panel/slash-commands.ts
+++ b/src/panel/slash-commands.ts
@@ -1,7 +1,12 @@
 import type { ReasoningEffort } from "../generated/app-server/ReasoningEffort";
+import type { Thread } from "../generated/app-server/v2/Thread";
+import { getThreadTitle } from "../threads";
 import { modelOverrideMessage, parseModelOverride, parseReasoningEffortOverride, reasoningEffortOverrideMessage } from "./runtime-settings";
 
 export const SLASH_COMMANDS = [
+  { command: "/new", detail: "Start a new Codex thread, optionally sending a message." },
+  { command: "/resume", detail: "Resume a recent Codex thread." },
+  { command: "/fork", detail: "Fork the active Codex thread." },
   { command: "/compact", detail: "Compact the current conversation context." },
   { command: "/fast", detail: "Toggle fast service tier for subsequent turns." },
   { command: "/plan", detail: "Toggle Plan mode, optionally sending a message." },
@@ -22,6 +27,10 @@ export function slashCommandHelpLines(): string[] {
 
 export interface SlashCommandExecutionContext {
   activeThreadId: string | null;
+  listedThreads: Thread[];
+  startNewThread: () => Promise<void>;
+  resumeThread: (threadId: string) => Promise<void>;
+  forkThread: (threadId: string) => Promise<void>;
   compactThread: (threadId: string) => Promise<void>;
   toggleFastMode: () => void;
   toggleCollaborationMode: () => void;
@@ -44,6 +53,35 @@ export async function executeSlashCommand(
   args: string,
   context: SlashCommandExecutionContext,
 ): Promise<SlashCommandExecutionResult | void> {
+  if (command === "new") {
+    await context.startNewThread();
+    if (args) return { sendText: args };
+    return;
+  }
+
+  if (command === "resume") {
+    const thread = resolveThreadArgument(args, context.listedThreads);
+    if (!thread.ok) {
+      context.addSystemMessage(thread.message);
+      return;
+    }
+    await context.resumeThread(thread.thread.id);
+    return;
+  }
+
+  if (command === "fork") {
+    if (args) {
+      context.addSystemMessage(`Unsupported slash command arguments: ${args}`);
+      return;
+    }
+    if (!context.activeThreadId) {
+      context.addSystemMessage("No active thread to fork.");
+      return;
+    }
+    await context.forkThread(context.activeThreadId);
+    return;
+  }
+
   if (command === "compact") {
     if (!context.activeThreadId) {
       context.addSystemMessage("No active thread to compact.");
@@ -115,3 +153,24 @@ export async function executeSlashCommand(
     context.addSystemMessage(`Unsupported slash command arguments: ${args}`);
   }
 }
+
+type ThreadResolution = { ok: true; thread: Thread } | { ok: false; message: string };
+
+export function resolveThreadArgument(args: string, threads: Thread[]): ThreadResolution {
+  const query = args.trim();
+  if (!query) {
+    const thread = threads[0];
+    return thread ? { ok: true, thread } : { ok: false, message: "No recent threads to resume." };
+  }
+
+  const idMatches = threads.filter((thread) => thread.id === query || thread.id.startsWith(query));
+  if (idMatches.length === 1) return { ok: true, thread: idMatches[0] };
+  if (idMatches.length > 1) return { ok: false, message: `Multiple matching threads: ${idMatches.map((thread) => thread.id).join(", ")}` };
+
+  const titleQuery = query.toLowerCase();
+  const titleMatches = threads.filter((thread) => getThreadTitle(thread).toLowerCase().includes(titleQuery));
+  if (titleMatches.length === 1) return { ok: true, thread: titleMatches[0] };
+  if (titleMatches.length > 1) return { ok: false, message: `Multiple matching threads: ${titleMatches.map(getThreadTitle).join(", ")}` };
+
+  return { ok: false, message: `No matching thread: ${query}` };
+}
diff --git a/tests/app-server-client.test.ts b/tests/app-server-client.test.ts
index 1f4f37c7..639fcc79 100644
--- a/tests/app-server-client.test.ts
+++ b/tests/app-server-client.test.ts
@@ -332,32 +332,41 @@ describe("AppServerClient", () => {
     transport.emitLine({ id: 3, result: { thread: { id: "thread-1", title: null }, cwd: "/vault" } });
     await resuming;
 
-    const skills = client.listSkills("/vault");
+    const forking = client.forkThread("thread-1", "/vault");
     expect(transport.sent[4]).toMatchObject({
       id: 4,
+      method: "thread/fork",
+      params: { threadId: "thread-1", cwd: "/vault", excludeTurns: true, persistExtendedHistory: false },
+    });
+    transport.emitLine({ id: 4, result: { thread: { id: "thread-2", title: null }, cwd: "/vault" } });
+    await forking;
+
+    const skills = client.listSkills("/vault");
+    expect(transport.sent[5]).toMatchObject({
+      id: 5,
       method: "skills/list",
       params: { cwds: ["/vault"], forceReload: false },
     });
-    expect((transport.sent[4] as { params?: Record<string, unknown> }).params?.perCwdExtraUserRoots).toBeUndefined();
-    transport.emitLine({ id: 4, result: { data: [] } });
+    expect((transport.sent[5] as { params?: Record<string, unknown> }).params?.perCwdExtraUserRoots).toBeUndefined();
+    transport.emitLine({ id: 5, result: { data: [] } });
     await skills;
 
     const turns = client.threadTurnsList("thread-1", "cursor-1", 10);
-    expect(transport.sent[5]).toMatchObject({
-      id: 5,
-      method: "thread/turns/list",
-      params: { threadId: "thread-1", cursor: "cursor-1", limit: 10, sortDirection: "desc", itemsView: "full" },
-    });
-    transport.emitLine({ id: 5, result: { data: [], nextCursor: null } });
-    await turns;
-
-    const firstTurn = client.threadTurnsList("thread-1", null, 1, "asc");
     expect(transport.sent[6]).toMatchObject({
       id: 6,
       method: "thread/turns/list",
-      params: { threadId: "thread-1", cursor: null, limit: 1, sortDirection: "asc", itemsView: "full" },
+      params: { threadId: "thread-1", cursor: "cursor-1", limit: 10, sortDirection: "desc", itemsView: "full" },
     });
     transport.emitLine({ id: 6, result: { data: [], nextCursor: null } });
+    await turns;
+
+    const firstTurn = client.threadTurnsList("thread-1", null, 1, "asc");
+    expect(transport.sent[7]).toMatchObject({
+      id: 7,
+      method: "thread/turns/list",
+      params: { threadId: "thread-1", cursor: null, limit: 1, sortDirection: "asc", itemsView: "full" },
+    });
+    transport.emitLine({ id: 7, result: { data: [], nextCursor: null } });
     await firstTurn;
   });
 
diff --git a/tests/composer-suggestions.test.ts b/tests/composer-suggestions.test.ts
index 19e526a5..b0ec6c93 100644
--- a/tests/composer-suggestions.test.ts
+++ b/tests/composer-suggestions.test.ts
@@ -1,5 +1,6 @@
 import { describe, expect, it } from "vitest";
 
+import type { Thread } from "../src/generated/app-server/v2/Thread";
 import {
   activeComposerSuggestions,
   applyComposerSuggestionInsertion,
@@ -9,6 +10,31 @@ import {
   parseSlashCommand,
 } from "../src/composer/suggestions";
 
+function thread(overrides: Partial<Thread> = {}): Thread {
+  return {
+    id: "019abcde-0000-7000-8000-000000000001",
+    sessionId: "session-1",
+    forkedFromId: null,
+    preview: "Preview",
+    ephemeral: false,
+    modelProvider: "openai",
+    createdAt: 1,
+    updatedAt: 1,
+    status: "idle",
+    path: null,
+    cwd: "/vault",
+    cliVersion: "0.130.0",
+    source: "appServer",
+    threadSource: null,
+    agentNickname: null,
+    agentRole: null,
+    gitInfo: null,
+    name: null,
+    turns: [],
+    ...overrides,
+  } as Thread;
+}
+
 describe("composer suggestions", () => {
   const notes = [
     { basename: "Alpha", path: "thoughts/Alpha.md", mtime: 10 },
@@ -18,6 +44,9 @@ describe("composer suggestions", () => {
 
   it("parses supported slash commands only", () => {
     expect(parseSlashCommand("/status")).toEqual({ command: "status", args: "" });
+    expect(parseSlashCommand("/new")).toEqual({ command: "new", args: "" });
+    expect(parseSlashCommand("/resume thread-1")).toEqual({ command: "resume", args: "thread-1" });
+    expect(parseSlashCommand("/fork")).toEqual({ command: "fork", args: "" });
     expect(parseSlashCommand("/doctor")).toEqual({ command: "doctor", args: "" });
     expect(parseSlashCommand("/fast now")).toEqual({ command: "fast", args: "now" });
     expect(parseSlashCommand("/plan")).toEqual({ command: "plan", args: "" });
@@ -44,6 +73,37 @@ describe("composer suggestions", () => {
     expect(activeComposerSuggestions("/doc", notes, [])[0]?.replacement).toBe("/doctor");
   });
 
+  it("suggests recent threads for /resume arguments", () => {
+    const threads = [
+      thread({ id: "019abcde-0000-7000-8000-000000000001", name: "Codex Panel実装" }),
+      thread({ id: "019abcde-0000-7000-8000-000000000002", name: "別件" }),
+    ];
+
+    const suggestions = activeComposerSuggestions("/resume codex", notes, [], threads);
+
+    expect(suggestions[0]).toMatchObject({
+      display: "Codex Panel実装",
+      detail: "019abcde",
+      replacement: "019abcde-0000-7000-8000-000000000001",
+      appendSpaceOnInsert: true,
+    });
+    expect(applyComposerSuggestionInsertion("/resume codex", 13, suggestions[0])).toEqual({
+      value: "/resume 019abcde-0000-7000-8000-000000000001 ",
+      cursor: 45,
+    });
+  });
+
+  it("does not suggest threads for /fork arguments", () => {
+    const suggestions = activeComposerSuggestions(
+      "/fork codex",
+      notes,
+      [],
+      [thread({ id: "019abcde-0000-7000-8000-000000000001", name: "Codex Panel実装" })],
+    );
+
+    expect(suggestions).toEqual([]);
+  });
+
   it("adds a trailing space for slash command and skill insertions only", () => {
     const slash = activeComposerSuggestions("/sta", notes, [])[0];
     const skill = activeComposerSuggestions("$obs", notes, [
diff --git a/tests/slash-commands.test.ts b/tests/slash-commands.test.ts
index 660f7377..bd7c1cfe 100644
--- a/tests/slash-commands.test.ts
+++ b/tests/slash-commands.test.ts
@@ -1,10 +1,15 @@
 import { describe, expect, it, vi } from "vitest";
 
+import type { Thread } from "../src/generated/app-server/v2/Thread";
 import { executeSlashCommand, slashCommandHelpLines, type SlashCommandExecutionContext } from "../src/panel/slash-commands";
 
 function context(overrides: Partial<SlashCommandExecutionContext> = {}): SlashCommandExecutionContext {
   return {
     activeThreadId: "thread-1",
+    listedThreads: [thread({ id: "thread-1", name: "Current" })],
+    startNewThread: vi.fn().mockResolvedValue(undefined),
+    resumeThread: vi.fn().mockResolvedValue(undefined),
+    forkThread: vi.fn().mockResolvedValue(undefined),
     compactThread: vi.fn().mockResolvedValue(undefined),
     toggleFastMode: vi.fn(),
     toggleCollaborationMode: vi.fn(),
@@ -20,7 +25,97 @@ function context(overrides: Partial<SlashCommandExecutionContext> = {}): SlashCo
   };
 }
 
+function thread(overrides: Partial<Thread> = {}): Thread {
+  return {
+    id: "thread-1",
+    sessionId: "session-1",
+    forkedFromId: null,
+    preview: "Preview",
+    ephemeral: false,
+    modelProvider: "openai",
+    createdAt: 1,
+    updatedAt: 1,
+    status: "idle",
+    path: null,
+    cwd: "/vault",
+    cliVersion: "0.130.0",
+    source: "appServer",
+    threadSource: null,
+    agentNickname: null,
+    agentRole: null,
+    gitInfo: null,
+    name: null,
+    turns: [],
+    ...overrides,
+  } as Thread;
+}
+
 describe("slash commands", () => {
+  it("starts a new thread for /new", async () => {
+    const ctx = context();
+
+    await executeSlashCommand("new", "", ctx);
+
+    expect(ctx.startNewThread).toHaveBeenCalledOnce();
+  });
+
+  it("returns message text after starting a new thread for /new arguments", async () => {
+    const ctx = context();
+
+    const result = await executeSlashCommand("new", "最初の依頼です", ctx);
+
+    expect(ctx.startNewThread).toHaveBeenCalledOnce();
+    expect(result).toEqual({ sendText: "最初の依頼です" });
+  });
+
+  it("resumes the latest listed thread for bare /resume", async () => {
+    const ctx = context({
+      listedThreads: [thread({ id: "latest", name: "Latest" }), thread({ id: "older", name: "Older" })],
+    });
+
+    await executeSlashCommand("resume", "", ctx);
+
+    expect(ctx.resumeThread).toHaveBeenCalledWith("latest");
+  });
+
+  it("resumes a thread by id argument", async () => {
+    const ctx = context({
+      listedThreads: [thread({ id: "thread-alpha", name: "Alpha" }), thread({ id: "thread-beta", name: "Beta" })],
+    });
+
+    await executeSlashCommand("resume", "thread-beta", ctx);
+
+    expect(ctx.resumeThread).toHaveBeenCalledWith("thread-beta");
+  });
+
+  it("reports ambiguous resume matches", async () => {
+    const ctx = context({
+      listedThreads: [thread({ id: "thread-alpha", name: "Draft" }), thread({ id: "thread-beta", name: "Draft notes" })],
+    });
+
+    await executeSlashCommand("resume", "Draft", ctx);
+
+    expect(ctx.resumeThread).not.toHaveBeenCalled();
+    expect(ctx.addSystemMessage).toHaveBeenCalledWith("Multiple matching threads: Draft, Draft notes");
+  });
+
+  it("forks the active thread for /fork", async () => {
+    const ctx = context({ activeThreadId: "active-thread" });
+
+    await executeSlashCommand("fork", "", ctx);
+
+    expect(ctx.forkThread).toHaveBeenCalledWith("active-thread");
+  });
+
+  it("rejects /fork arguments", async () => {
+    const ctx = context();
+
+    await executeSlashCommand("fork", "anything", ctx);
+
+    expect(ctx.forkThread).not.toHaveBeenCalled();
+    expect(ctx.addSystemMessage).toHaveBeenCalledWith("Unsupported slash command arguments: anything");
+  });
+
   it("toggles Plan mode without sending text for bare /plan", async () => {
     const ctx = context();