feat(codex): add Codex (OpenAI CLI) run-mode foundation

Add Codex as a first-class session mode alongside Claude/Shell/OpenCode.

- codex-cli-resolver: locate the `codex` binary and augment PATH (mirrors the
  OpenCode resolver)
- SessionMode 'codex' + CodexConfig (model, resumeSessionId, dangerouslyBypass,
  renderMode); persisted in SessionState and threaded through CreateSession/
  RespawnPane options
- schema validation: CodexConfigSchema, CODEX_ env-var prefix allowlist, mode
  enums on create/quick-start, codexDangerouslyBypassApprovals setting
- tmux launch: buildCodexCommand, setenv for OPENAI_API_KEY/CODEX_* (keeps
  secrets out of ps), truecolor COLORTERM, codex PATH resolution
- session + routes: availability check (clear install hint), config passthrough,
  tmux-required guard; Codex skips Claude-only parsers (Ralph/respawn/token)
- run-mode UI: "Run CX" selector option + dedicated Codex CLI settings tab with
  the bypass-approvals toggle; GET /api/codex/status

Scope: foundation only. Codex terminal redraw handling and xterm snapshot/replay
are intentionally excluded and tracked separately.

Verification: tsc --noEmit, eslint, prettier --check, check:frontend-syntax all
clean; full test:ci suite green (2712 passed, 0 failed); server boot smoke OK.

Co-Authored-By: Saqeb Akhter <saqeb.akhter@gmail.com>

src/mux-interface.ts

@@ -14,6 +14,7 @@ import type {
   ClaudeMode,
   SessionMode,
   OpenCodeConfig,
+  CodexConfig,
   EffortLevel,
 } from './types.js';
 
@@ -62,6 +63,7 @@ export interface CreateSessionOptions {
   claudeMode?: ClaudeMode;
   allowedTools?: string;
   openCodeConfig?: OpenCodeConfig;
+  codexConfig?: CodexConfig;
   /** When restoring after reboot, resume a previous Claude conversation by its session ID */
   resumeSessionId?: string;
   /** Extra env vars exported before launching the CLI (e.g., CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS). Ephemeral — not written to disk. */
@@ -80,6 +82,7 @@ export interface RespawnPaneOptions {
   claudeMode?: ClaudeMode;
   allowedTools?: string;
   openCodeConfig?: OpenCodeConfig;
+  codexConfig?: CodexConfig;
   /** Resume a previous Claude conversation when respawning */
   resumeSessionId?: string;
   /** Extra env vars exported before launching the CLI (preserved across respawns). */

src/session.ts

@@ -46,6 +46,7 @@ import {
   type ClaudeMode,
   type SessionMode,
   type OpenCodeConfig,
+  type CodexConfig,
   type EffortLevel,
 } from './types.js';
 import type { TerminalMultiplexer, MuxSession } from './mux-interface.js';
@@ -123,6 +124,11 @@ const CTRL_L_PATTERN = /\x0c/g;
 /** Pattern to split by newlines (CR or LF) */
 const NEWLINE_SPLIT_PATTERN = /\r?\n/;
 
+/** True for external-CLI run modes (non-Claude) that use their own TUI and output format. */
+function isExternalCliMode(mode: SessionMode): boolean {
+  return mode === 'opencode' || mode === 'codex';
+}
+
 // Note: Claude CLI PATH resolution moved to session-cli-builder.ts (buildClaudeEnv)
 
 /** PTY fallback geometry when tmux can't be queried (matches pre-#80 hardcoded values). */
@@ -313,6 +319,8 @@ export class Session extends EventEmitter {
 
   // OpenCode configuration (only for mode === 'opencode')
   private _openCodeConfig: OpenCodeConfig | undefined;
+  // Codex configuration (only for mode === 'codex')
+  private _codexConfig: CodexConfig | undefined;
   private _resumeSessionId: string | undefined;
 
   // Ephemeral env overrides (e.g., CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS). Exported by tmux
@@ -381,6 +389,8 @@ export class Session extends EventEmitter {
       allowedTools?: string;
       /** OpenCode configuration (only for mode === 'opencode') */
       openCodeConfig?: OpenCodeConfig;
+      /** Codex configuration (only for mode === 'codex') */
+      codexConfig?: CodexConfig;
       /** Resume a previous Claude conversation (used after server reboot) */
       resumeSessionId?: string;
       /** Extra env vars exported to the CLI at spawn time (no disk persistence) */
@@ -434,6 +444,11 @@ export class Session extends EventEmitter {
       this._openCodeConfig = config.openCodeConfig;
     }
 
+    // Apply Codex configuration
+    if (config.codexConfig) {
+      this._codexConfig = config.codexConfig;
+    }
+
     // Apply env overrides (exported at spawn, not persisted to disk).
     // Legacy migration: pre-0.7.2 carried effort as the CLAUDE_CODE_EFFORT_LEVEL env var,
     // which hard-locks /effort switching. Extract it into _effort (--settings soft default)
@@ -696,6 +711,11 @@ export class Session extends EventEmitter {
     return this._allowedTools;
   }
 
+  /** Codex CLI configuration for this session. */
+  get codexConfig(): CodexConfig | undefined {
+    return this._codexConfig;
+  }
+
   // Note: _buildPermissionArgs removed — now using buildInteractiveArgs from session-cli-builder.ts
 
   /**
@@ -867,6 +887,7 @@ export class Session extends EventEmitter {
       cliAccountType: this._cliAccountType || undefined,
       cliLatestVersion: this._cliLatestVersion || undefined,
       openCodeConfig: this._openCodeConfig,
+      codexConfig: this._codexConfig,
       resumeSessionId: this._resumeSessionId,
       effort: this._effort,
       // envOverrides intentionally NOT on the public SessionState type — they must not
@@ -1045,7 +1066,7 @@ export class Session extends EventEmitter {
 
     this._resetBuffers();
 
-    const modeLabel = this.mode === 'opencode' ? 'OpenCode' : 'Claude';
+    const modeLabel = this.mode === 'opencode' ? 'OpenCode' : this.mode === 'codex' ? 'Codex' : 'Claude';
     console.log(
       `[Session] Starting interactive ${modeLabel} session` + (this._useMux ? ` (with ${this._mux!.backend})` : '')
     );
@@ -1063,6 +1084,7 @@ export class Session extends EventEmitter {
             claudeMode: this._claudeMode,
             allowedTools: this._allowedTools,
             openCodeConfig: this._openCodeConfig,
+            codexConfig: this._codexConfig,
             resumeSessionId: this._resumeSessionId,
             envOverrides: this._envOverrides,
             effort: this._effort,
@@ -1077,6 +1099,7 @@ export class Session extends EventEmitter {
             claudeMode: this._claudeMode,
             allowedTools: this._allowedTools,
             openCodeConfig: this._openCodeConfig,
+            codexConfig: this._codexConfig,
             resumeSessionId: this._resumeSessionId,
             envOverrides: this._envOverrides,
             effort: this._effort,
@@ -1090,8 +1113,8 @@ export class Session extends EventEmitter {
         // For NEW mux sessions: wait for readiness then clean buffer
         // For RESTORED mux sessions: don't do anything - client will fetch buffer on tab switch
         if (!isRestored) {
-          if (this.mode === 'opencode') {
-            // OpenCode uses Bubble Tea TUI — no ❯ prompt to detect.
+          if (isExternalCliMode(this.mode)) {
+            // External CLIs use custom TUIs — no ❯ prompt to detect.
             // Wait for TUI to stabilize (output stops changing), then mark ready.
             // Don't clear the buffer — the TUI's initial render IS the useful content.
             // Emit needsRefresh so the client fetches the full buffer once the TUI has rendered.
@@ -1146,6 +1169,10 @@ export class Session extends EventEmitter {
       if (this.mode === 'opencode') {
         throw new Error('OpenCode sessions require tmux. Direct PTY fallback is not supported.');
       }
+      // Codex sessions require tmux for OPENAI_API_KEY injection via setenv
+      if (this.mode === 'codex') {
+        throw new Error('Codex sessions require tmux. Direct PTY fallback is not supported.');
+      }
       try {
         // Pass --session-id to use the SAME ID as the Codeman session
         // This ensures subagents can be directly matched to the correct tab
@@ -1305,9 +1332,9 @@ export class Session extends EventEmitter {
    * PTY data chunk. Receives accumulated raw data to process in one batch.
    */
   private _processExpensiveParsers(rawData: string): void {
-    // Skip Claude-specific parsers for OpenCode sessions — Ralph tracker, BashToolParser,
-    // token parsing, and CLI info parsing all depend on Claude's output format.
-    if (this.mode === 'opencode') return;
+    // Skip Claude-specific parsers for external CLI sessions (Ralph tracker,
+    // BashToolParser, token + CLI-info parsing all depend on Claude's output format).
+    if (isExternalCliMode(this.mode)) return;
 
     // Lazy ANSI strip: only compute cleanData when a consumer actually needs it.
     let _cleanData: string | null = null;

src/tmux-manager.ts

@@ -39,10 +39,11 @@ import {
   type ClaudeMode,
   type SessionMode,
   type OpenCodeConfig,
+  type CodexConfig,
   type EffortLevel,
 } from './types.js';
 import { buildEffortCliArgs } from './session-cli-builder.js';
-import { wrapWithNice, SAFE_PATH_PATTERN, findClaudeDir, resolveOpenCodeDir } from './utils/index.js';
+import { wrapWithNice, SAFE_PATH_PATTERN, findClaudeDir, resolveOpenCodeDir, resolveCodexDir } from './utils/index.js';
 import type {
   TerminalMultiplexer,
   MuxSession,
@@ -539,6 +540,32 @@ function buildOpenCodeCommand(config?: OpenCodeConfig): string {
   return parts.join(' ');
 }
 
+/**
+ * Build the codex CLI command with appropriate flags.
+ *
+ * Codeman launches Codex's native TUI and handles replay/scrollback by
+ * stripping destructive terminal sequences before xterm.js sees them.
+ */
+export function buildCodexCommand(config?: CodexConfig): string {
+  const parts = ['codex'];
+
+  if (config?.dangerouslyBypassApprovals) {
+    parts.push('--dangerously-bypass-approvals-and-sandbox');
+  }
+
+  if (config?.model) {
+    const safeModel = /^[a-zA-Z0-9._\-/]+$/.test(config.model) ? config.model : undefined;
+    if (safeModel) parts.push('--model', safeModel);
+  }
+
+  if (config?.resumeSessionId) {
+    const safeId = /^[a-zA-Z0-9_-]+$/.test(config.resumeSessionId) ? config.resumeSessionId : undefined;
+    if (safeId) parts.push('resume', safeId);
+  }
+
+  return parts.join(' ');
+}
+
 /**
  * Build the spawn command for any session mode.
  * Shared by createSession() and respawnPane() to avoid duplication.
@@ -564,6 +591,7 @@ function buildSpawnCommand(options: {
   claudeMode?: ClaudeMode;
   allowedTools?: string;
   openCodeConfig?: OpenCodeConfig;
+  codexConfig?: CodexConfig;
   resumeSessionId?: string;
   effort?: EffortLevel;
 }): string {
@@ -588,6 +616,9 @@ function buildSpawnCommand(options: {
   if (options.mode === 'opencode') {
     return buildOpenCodeCommand(options.openCodeConfig);
   }
+  if (options.mode === 'codex') {
+    return buildCodexCommand(options.codexConfig);
+  }
   return '$SHELL';
 }
 
@@ -615,6 +646,29 @@ function setOpenCodeEnvVars(tmuxCmd: string, muxName: string): void {
   }
 }
 
+/**
+ * Set sensitive environment variables for Codex on a tmux session via setenv.
+ * Codex (OpenAI CLI) needs OPENAI_API_KEY; we also forward CODEX_* keys.
+ */
+function setCodexEnvVars(tmuxCmd: string, muxName: string): void {
+  const sensitiveVars = ['OPENAI_API_KEY', 'CODEX_API_KEY', 'CODEX_HOME'];
+  for (const key of sensitiveVars) {
+    const val = process.env[key];
+    if (val) {
+      const escaped = val.replace(/'/g, "'\\''");
+      try {
+        execSync(`${tmuxCmd} setenv -t '${muxName}' ${key} '${escaped}'`, {
+          encoding: 'utf8',
+          timeout: EXEC_TIMEOUT_MS,
+          stdio: ['pipe', 'pipe', 'pipe'],
+        });
+      } catch {
+        /* Non-critical — key may not be needed */
+      }
+    }
+  }
+}
+
 /**
  * Set OPENCODE_CONFIG_CONTENT on a tmux session via setenv.
  * Uses tmux setenv to avoid shell metacharacter injection from user-supplied JSON.
@@ -797,7 +851,8 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     const exports = [
       'export LANG=en_US.UTF-8',
       'export LC_ALL=en_US.UTF-8',
-      'unset COLORTERM',
+      mode === 'codex' ? 'export COLORTERM=truecolor' : 'unset COLORTERM',
+      ...(mode === 'codex' ? ['unset NO_COLOR'] : []),
       'export CODEMAN_MUX=1',
       `export CODEMAN_SESSION_ID=${sessionId}`,
       `export CODEMAN_MUX_NAME=${muxName}`,
@@ -863,6 +918,10 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       const dir = resolveOpenCodeDir();
       return { pathExport: dir ? `export PATH="${dir}:$PATH" && ` : '', dir };
     }
+    if (mode === 'codex') {
+      const dir = resolveCodexDir();
+      return { pathExport: dir ? `export PATH="${dir}:$PATH" && ` : '', dir };
+    }
     return { pathExport: '', dir: null };
   }
 
@@ -877,6 +936,15 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
     setOpenCodeConfigContent(tmuxCmd, muxName, openCodeConfig);
   }
 
+  /**
+   * Configure Codex-specific environment on a tmux session.
+   * Sets OPENAI_API_KEY (and related keys) via tmux setenv so secrets don't
+   * appear in the bash command line.
+   */
+  private _configureCodex(muxName: string): void {
+    setCodexEnvVars(this.tmux(), muxName);
+  }
+
   /**
    * Creates a new tmux session wrapping Claude CLI or a shell.
    * In test mode: creates an in-memory session only (no real tmux session).
@@ -892,6 +960,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       claudeMode,
       allowedTools,
       openCodeConfig,
+      codexConfig,
       resumeSessionId,
       envOverrides,
       effort,
@@ -940,6 +1009,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       claudeMode,
       allowedTools,
       openCodeConfig,
+      codexConfig,
       resumeSessionId,
       effort,
     });
@@ -986,6 +1056,8 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       // (not visible in ps output or tmux history, inherited by panes)
       if (mode === 'opencode') {
         this._configureOpenCode(muxName, openCodeConfig);
+      } else if (mode === 'codex') {
+        this._configureCodex(muxName);
       }
 
       // Apply user-supplied env overrides (e.g., CLAUDE_CODE_EFFORT_LEVEL) via tmux setenv
@@ -1143,6 +1215,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       claudeMode,
       allowedTools,
       openCodeConfig,
+      codexConfig,
       resumeSessionId,
       envOverrides,
       effort,
@@ -1165,6 +1238,7 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       claudeMode,
       allowedTools,
       openCodeConfig,
+      codexConfig,
       resumeSessionId,
       effort,
     });
@@ -1176,6 +1250,8 @@ export class TmuxManager extends EventEmitter implements TerminalMultiplexer {
       // For OpenCode: set sensitive env vars via tmux setenv before respawn
       if (mode === 'opencode') {
         this._configureOpenCode(muxName, openCodeConfig);
+      } else if (mode === 'codex') {
+        this._configureCodex(muxName);
       }
 
       // Re-apply user env overrides before respawn so the new shell inherits them.

src/types/session.ts

@@ -8,7 +8,7 @@
  * - SessionConfig — creation-time config (id, workingDir, createdAt)
  * - SessionOutput — captured stdout/stderr/exitCode
  * - SessionStatus — 'idle' | 'busy' | 'stopped' | 'error'
- * - SessionMode — 'claude' | 'shell' | 'opencode' (which CLI backend)
+ * - SessionMode — 'claude' | 'shell' | 'opencode' | 'codex' (which CLI backend)
  * - ClaudeMode — CLI permission mode ('dangerously-skip-permissions' | 'normal' | 'allowedTools')
  * - SessionColor — visual differentiation color
  * - OpenCodeConfig — OpenCode-specific settings (model, autoAllowTools, continueSession)
@@ -38,7 +38,7 @@ export type SessionStatus = 'idle' | 'busy' | 'stopped' | 'error';
 export type ClaudeMode = 'dangerously-skip-permissions' | 'normal' | 'allowedTools';
 
 /** Session mode: which CLI backend a session runs */
-export type SessionMode = 'claude' | 'shell' | 'opencode';
+export type SessionMode = 'claude' | 'shell' | 'opencode' | 'codex';
 
 /**
  * Valid Claude CLI effort levels (claude >= 2.1.154).
@@ -69,6 +69,21 @@ export interface OpenCodeConfig {
   configContent?: string;
 }
 
+/** Codex (OpenAI CLI) browser rendering strategy. Hybrid TUI is the only supported mode. */
+export type CodexRenderMode = 'hybrid';
+
+/** Codex (OpenAI CLI) session configuration */
+export interface CodexConfig {
+  /** Model identifier (e.g., "gpt-5", "o4-mini"). Passed via --model. */
+  model?: string;
+  /** Resume a previous codex conversation by session id (passed via --resume) */
+  resumeSessionId?: string;
+  /** Bypass approval prompts (passes --dangerously-bypass-approvals-and-sandbox) */
+  dangerouslyBypassApprovals?: boolean;
+  /** Browser rendering strategy for Codex sessions. Hybrid TUI is the only supported mode. */
+  renderMode?: CodexRenderMode;
+}
+
 /**
  * Configuration for creating a new session
  */
@@ -158,6 +173,8 @@ export interface SessionState {
   cliLatestVersion?: string;
   /** OpenCode-specific configuration (only for mode === 'opencode') */
   openCodeConfig?: OpenCodeConfig;
+  /** Codex-specific configuration (only for mode === 'codex') */
+  codexConfig?: CodexConfig;
   /** Claude conversation session ID to resume after reboot (set by restore script) */
   resumeSessionId?: string;
   /** Claude CLI effort level (soft default via --settings, switchable in-session via /effort) */

src/utils/codex-cli-resolver.ts

@@ -0,0 +1,69 @@
+/**
+ * @fileoverview Resolve the Codex (OpenAI) CLI binary across common install paths.
+ *
+ * Mirrors opencode-cli-resolver.ts pattern. Finds the `codex` binary
+ * and provides an augmented PATH string for tmux sessions.
+ *
+ * @module utils/codex-cli-resolver
+ */
+
+import { execSync } from 'node:child_process';
+import { existsSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { homedir } from 'node:os';
+import { EXEC_TIMEOUT_MS } from '../config/exec-timeout.js';
+
+/** Common directories where the Codex CLI binary may be installed */
+const CODEX_SEARCH_DIRS = [
+  join(homedir(), '.codex', 'bin'), // Default install location
+  join(homedir(), '.local', 'bin'), // Alternative install location
+  '/usr/local/bin', // Homebrew / system
+  join(homedir(), '.bun', 'bin'), // Bun global
+  join(homedir(), '.npm-global', 'bin'), // npm global
+  join(homedir(), 'bin'), // User bin
+];
+
+/** Cached directory containing the codex binary (empty string = searched but not found) */
+let _codexDir: string | null = null;
+
+/**
+ * Finds the directory containing the `codex` binary.
+ * Checks `which codex` first, then falls back to common install locations.
+ * Result is cached for subsequent calls.
+ *
+ * @returns Directory path, or null if not found
+ */
+export function resolveCodexDir(): string | null {
+  if (_codexDir !== null) return _codexDir || null;
+
+  // Try `which` first (respects current PATH)
+  try {
+    const result = execSync('which codex', {
+      encoding: 'utf-8',
+      timeout: EXEC_TIMEOUT_MS,
+    }).trim();
+    if (result && existsSync(result)) {
+      _codexDir = dirname(result);
+      return _codexDir;
+    }
+  } catch {
+    // Codex not in PATH, will check common locations
+  }
+
+  for (const dir of CODEX_SEARCH_DIRS) {
+    if (existsSync(join(dir, 'codex'))) {
+      _codexDir = dir;
+      return _codexDir;
+    }
+  }
+
+  _codexDir = ''; // mark as searched, not found
+  return null;
+}
+
+/**
+ * Check if Codex CLI is available on the system.
+ */
+export function isCodexAvailable(): boolean {
+  return resolveCodexDir() !== null;
+}

src/utils/index.ts

@@ -28,3 +28,4 @@ export { assertNever } from './type-safety.js';
 export { wrapWithNice } from './nice-wrapper.js';
 export { findClaudeDir, getAugmentedPath } from './claude-cli-resolver.js';
 export { resolveOpenCodeDir } from './opencode-cli-resolver.js';
+export { resolveCodexDir, isCodexAvailable } from './codex-cli-resolver.js';

src/web/public/index.html

@@ -384,6 +384,9 @@
               <button class="run-mode-option" data-mode="opencode" onclick="app.setRunMode('opencode')">
                 <span class="run-mode-dot opencode"></span>OpenCode
               </button>
+              <button class="run-mode-option" data-mode="codex" onclick="app.setRunMode('codex')">
+                <span class="run-mode-dot codex"></span>Codex
+              </button>
               <div class="run-mode-sep"></div>
               <div class="run-mode-header">Recent Sessions</div>
               <div class="run-mode-history" id="runModeHistory"></div>
@@ -895,6 +898,7 @@
         <div class="modal-tabs">
           <button class="modal-tab-btn active" data-tab="settings-display">Display</button>
           <button class="modal-tab-btn" data-tab="settings-claude">Claude CLI</button>
+          <button class="modal-tab-btn" data-tab="settings-codex">Codex CLI</button>
           <button class="modal-tab-btn" data-tab="settings-models">Models</button>
           <button class="modal-tab-btn" data-tab="settings-paths">Paths</button>
           <button class="modal-tab-btn" data-tab="settings-notifications">Notifications</button>
@@ -1174,6 +1178,18 @@
               <span class="form-hint">Process priority (-20 to 19, higher = lower priority, default: 10)</span>
             </div>
           </div>
+          <!-- Codex CLI Tab -->
+          <div class="modal-tab-content hidden" id="settings-codex">
+            <div class="form-section-header">Codex CLI</div>
+            <div class="form-row form-row-switch">
+              <label>Bypass Approvals and Sandbox</label>
+              <label class="switch">
+                <input type="checkbox" id="appSettingsCodexDangerouslyBypassApprovals">
+                <span class="slider"></span>
+              </label>
+              <span class="form-hint">Start new Codex sessions with --dangerously-bypass-approvals-and-sandbox</span>
+            </div>
+          </div>
           <!-- Models Tab -->
           <div class="modal-tab-content hidden" id="settings-models">
             <div class="form-row">

src/web/public/session-ui.js

@@ -157,6 +157,9 @@ Object.assign(CodemanApp.prototype, {
     if (mode === 'opencode') {
       return this.runOpenCode();
     }
+    if (mode === 'codex') {
+      return this.runCodex();
+    }
     return this.runClaude();
   },
 
@@ -253,7 +256,7 @@ Object.assign(CodemanApp.prototype, {
       gearBtn.className = `btn-toolbar btn-run-gear mode-${mode}`;
     }
     if (label) {
-      label.textContent = mode === 'opencode' ? 'Run OC' : 'Run';
+      label.textContent = mode === 'opencode' ? 'Run OC' : mode === 'codex' ? 'Run CX' : 'Run';
     }
   },
 
@@ -580,6 +583,51 @@ Object.assign(CodemanApp.prototype, {
     }
   },
 
+  async runCodex() {
+    const caseName = document.getElementById('quickStartCase').value || 'testcase';
+
+    this.terminal.clear();
+    this.terminal.writeln(`\x1b[1;32m Starting Codex session in ${caseName}...\x1b[0m`);
+    this.terminal.writeln('');
+    this.terminal.focus();
+
+    try {
+      const statusRes = await fetch('/api/codex/status');
+      const status = await statusRes.json();
+      if (!status.available) {
+        this.terminal.writeln('\x1b[1;31m Codex CLI not found.\x1b[0m');
+        this.terminal.writeln('\x1b[90m Install with: npm install -g @openai/codex\x1b[0m');
+        return;
+      }
+
+      const globalSettings = this.loadAppSettingsFromStorage();
+      const envOverrides = this.buildEnvOverrides(this.getCaseSettings(caseName), globalSettings);
+      const res = await fetch('/api/quick-start', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({
+          caseName,
+          mode: 'codex',
+          codexConfig: {
+            dangerouslyBypassApprovals: globalSettings.codexDangerouslyBypassApprovals ?? false,
+            renderMode: 'hybrid',
+          },
+          ...(Object.keys(envOverrides).length > 0 ? { envOverrides } : {}),
+        })
+      });
+      const data = await res.json();
+      if (!data.success) throw new Error(data.error || 'Failed to start Codex');
+
+      if (data.sessionId) {
+        await this.selectSession(data.sessionId);
+      }
+
+      this.terminal.focus();
+    } catch (err) {
+      this.terminal.writeln(`\x1b[1;31m Error: ${err.message}\x1b[0m`);
+    }
+  },
+
 
   // ═══════════════════════════════════════════════════════════════
   // Session Options Modal
@@ -592,7 +640,7 @@ Object.assign(CodemanApp.prototype, {
     this.editingSessionId = sessionId;
 
     // Reset to an appropriate tab — Summary for OpenCode (Respawn/Ralph are Claude-only)
-    this.switchOptionsTab(session.mode === 'opencode' ? 'summary' : 'respawn');
+    this.switchOptionsTab(session.mode === 'opencode' || session.mode === 'codex' ? 'summary' : 'respawn');
 
     // Update respawn status display and buttons
     const respawnStatus = document.getElementById('sessionRespawnStatus');
@@ -621,7 +669,7 @@ Object.assign(CodemanApp.prototype, {
     }
 
     // Hide Claude-specific options for OpenCode sessions
-    const isOpenCode = session.mode === 'opencode';
+    const isOpenCode = session.mode === 'opencode' || session.mode === 'codex';
     const claudeOnlyEls = document.querySelectorAll('[data-claude-only]');
     claudeOnlyEls.forEach(el => { el.style.display = isOpenCode ? 'none' : ''; });
 
@@ -1474,3 +1522,14 @@ Object.assign(CodemanApp.prototype, {
     setTimeout(() => modal.classList.remove('from-mobile'), 300);
   },
 });
+
+Object.defineProperty(CodemanApp.prototype, 'runMode', {
+  configurable: true,
+  enumerable: true,
+  get() {
+    return this._runMode || 'claude';
+  },
+  set(mode) {
+    this._runMode = mode === 'opencode' || mode === 'codex' || mode === 'claude' ? mode : 'claude';
+  },
+});

src/web/public/settings-ui.js

@@ -339,6 +339,9 @@ Object.assign(CodemanApp.prototype, {
     claudeModeSelect.onchange = () => {
       allowedToolsRow.style.display = claudeModeSelect.value === 'allowedTools' ? '' : 'none';
     };
+    // Codex CLI settings
+    document.getElementById('appSettingsCodexDangerouslyBypassApprovals').checked =
+      settings.codexDangerouslyBypassApprovals ?? false;
     // Claude Permissions settings
     document.getElementById('appSettingsAgentTeams').checked = settings.agentTeamsEnabled ?? false;
     document.getElementById('appSettingsOpusContext1m').checked = settings.opusContext1mEnabled ?? false;
@@ -1340,6 +1343,8 @@ Object.assign(CodemanApp.prototype, {
       // Claude CLI settings
       claudeMode: document.getElementById('appSettingsClaudeMode').value,
       allowedTools: document.getElementById('appSettingsAllowedTools').value.trim(),
+      // Codex CLI settings
+      codexDangerouslyBypassApprovals: document.getElementById('appSettingsCodexDangerouslyBypassApprovals').checked,
       // Claude Permissions settings
       agentTeamsEnabled: document.getElementById('appSettingsAgentTeams').checked,
       opusContext1mEnabled: document.getElementById('appSettingsOpusContext1m').checked,

src/web/routes/session-routes.ts

@@ -282,6 +282,17 @@ export function registerSessionRoutes(
       }
     }
 
+    // Check Codex availability if requested
+    if (body.mode === 'codex') {
+      const { isCodexAvailable } = await import('../../utils/codex-cli-resolver.js');
+      if (!isCodexAvailable()) {
+        return createErrorResponse(
+          ApiErrorCode.OPERATION_FAILED,
+          'Codex CLI not found. Install with: npm install -g @openai/codex'
+        );
+      }
+    }
+
     // Pre-validate resumeSessionId: check that the conversation file actually exists
     // in Claude's projects directory. If not, skip resume to avoid confusing
     // "No conversation found" errors from Claude CLI.
@@ -318,9 +329,11 @@ export function registerSessionRoutes(
     const model =
       mode === 'opencode'
         ? body.openCodeConfig?.model
-        : mode !== 'shell'
-          ? modelConfig?.defaultModel || undefined
-          : undefined;
+        : mode === 'codex'
+          ? body.codexConfig?.model
+          : mode !== 'shell'
+            ? modelConfig?.defaultModel || undefined
+            : undefined;
     const claudeModeConfig = await ctx.getClaudeModeConfig();
     const session = new Session({
       workingDir,
@@ -333,6 +346,7 @@ export function registerSessionRoutes(
       claudeMode: claudeModeConfig.claudeMode,
       allowedTools: claudeModeConfig.allowedTools,
       openCodeConfig: mode === 'opencode' ? body.openCodeConfig : undefined,
+      codexConfig: mode === 'codex' ? body.codexConfig : undefined,
       resumeSessionId: validatedResumeId,
       envOverrides: body.envOverrides,
       effort: body.effort,
@@ -1112,6 +1126,7 @@ export function registerSessionRoutes(
       caseName = 'testcase',
       mode = 'claude',
       openCodeConfig,
+      codexConfig,
       envOverrides,
       effort,
     } = parseBody(QuickStartSchema, req.body);
@@ -1127,6 +1142,17 @@ export function registerSessionRoutes(
       }
     }
 
+    // Check Codex availability if requested
+    if (mode === 'codex') {
+      const { isCodexAvailable } = await import('../../utils/codex-cli-resolver.js');
+      if (!isCodexAvailable()) {
+        return createErrorResponse(
+          ApiErrorCode.OPERATION_FAILED,
+          'Codex CLI not found. Install with: npm install -g @openai/codex'
+        );
+      }
+    }
+
     // Resolve case path: check linked-cases registry first, then fall back to CASES_DIR.
     // This mirrors the behaviour of resolveCasePath() in case-routes so that linked
     // external project directories are honoured by quick-start just like regular case routes.
@@ -1179,9 +1205,11 @@ export function registerSessionRoutes(
     const qsModel =
       mode === 'opencode'
         ? openCodeConfig?.model
-        : mode !== 'shell'
-          ? qsModelConfig?.defaultModel || undefined
-          : undefined;
+        : mode === 'codex'
+          ? codexConfig?.model
+          : mode !== 'shell'
+            ? qsModelConfig?.defaultModel || undefined
+            : undefined;
     const qsClaudeModeConfig = await ctx.getClaudeModeConfig();
     const session = new Session({
       workingDir: casePath,
@@ -1193,6 +1221,7 @@ export function registerSessionRoutes(
       claudeMode: qsClaudeModeConfig.claudeMode,
       allowedTools: qsClaudeModeConfig.allowedTools,
       openCodeConfig: mode === 'opencode' ? openCodeConfig : undefined,
+      codexConfig: mode === 'codex' ? codexConfig : undefined,
       envOverrides,
       effort,
     });

src/web/routes/system-routes.ts

@@ -341,6 +341,14 @@ export function registerSystemRoutes(
     };
   });
 
+  app.get('/api/codex/status', async () => {
+    const { isCodexAvailable, resolveCodexDir } = await import('../../utils/codex-cli-resolver.js');
+    return {
+      available: isCodexAvailable(),
+      path: resolveCodexDir(),
+    };
+  });
+
   // ═══════════════════════════════════════════════════════════════
   // State & Lifecycle (cleanup, lifecycle log, stats)
   // ═══════════════════════════════════════════════════════════════

src/web/schemas.ts

@@ -46,7 +46,7 @@ const safePathSchema = z.string().max(1000).refine(isValidWorkingDir, {
 // ========== Env Var Allowlist ==========
 
 /** Allowlisted env var key prefixes */
-const ALLOWED_ENV_PREFIXES = ['CLAUDE_CODE_', 'OPENCODE_'];
+const ALLOWED_ENV_PREFIXES = ['CLAUDE_CODE_', 'OPENCODE_', 'CODEX_'];
 
 /** Env var keys that are always blocked (security-sensitive) */
 const BLOCKED_ENV_KEYS = new Set([
@@ -76,7 +76,7 @@ const safeEnvOverridesSchema = z
     },
     {
       message:
-        'envOverrides contains blocked or disallowed env var keys. Only CLAUDE_CODE_* and OPENCODE_* keys are allowed.',
+        'envOverrides contains blocked or disallowed env var keys. Only CLAUDE_CODE_*, OPENCODE_*, and CODEX_* keys are allowed.',
     }
   );
 
@@ -128,9 +128,30 @@ const OpenCodeConfigSchema = z
   })
   .optional();
 
+/** Schema for Codex (OpenAI CLI)-specific configuration */
+const CodexConfigSchema = z
+  .object({
+    model: z
+      .string()
+      .max(100)
+      .regex(/^[a-zA-Z0-9._\-/]+$/)
+      .optional(),
+    resumeSessionId: z
+      .string()
+      .max(100)
+      .regex(/^[a-zA-Z0-9_-]+$/)
+      .optional(),
+    dangerouslyBypassApprovals: z.boolean().optional(),
+    renderMode: z
+      .enum(['scrollback', 'hybrid'])
+      .optional()
+      .transform(() => 'hybrid' as const),
+  })
+  .optional();
+
 export const CreateSessionSchema = z.object({
   workingDir: safePathSchema.optional(),
-  mode: z.enum(['claude', 'shell', 'opencode']).optional(),
+  mode: z.enum(['claude', 'shell', 'opencode', 'codex']).optional(),
   name: z.string().max(100).optional(),
   envOverrides: safeEnvOverridesSchema,
   /** Claude CLI effort level (soft default via --settings, switchable in-session via /effort) */
@@ -138,6 +159,7 @@ export const CreateSessionSchema = z.object({
   /** Model override to write to .claude/settings.local.json (e.g., "opus[1m]"). Empty string clears. */
   modelOverride: z.string().max(50).optional(),
   openCodeConfig: OpenCodeConfigSchema,
+  codexConfig: CodexConfigSchema,
   /** Resume a previous Claude conversation by its session ID (used for reboot recovery) */
   resumeSessionId: z
     .string()
@@ -188,8 +210,9 @@ export const QuickStartSchema = z.object({
     .string()
     .regex(/^[a-zA-Z0-9_-]+$/, 'Invalid case name format. Use only letters, numbers, hyphens, underscores.')
     .optional(),
-  mode: z.enum(['claude', 'shell', 'opencode']).optional(),
+  mode: z.enum(['claude', 'shell', 'opencode', 'codex']).optional(),
   openCodeConfig: OpenCodeConfigSchema,
+  codexConfig: CodexConfigSchema,
   envOverrides: safeEnvOverridesSchema,
   /** Claude CLI effort level (soft default via --settings, switchable in-session via /effort) */
   effort: effortLevelSchema,
@@ -300,6 +323,8 @@ export const SettingsUpdateSchema = z
     // Claude CLI settings
     claudeMode: z.string().max(50).optional(),
     allowedTools: z.string().max(2000).optional(),
+    // Codex CLI settings
+    codexDangerouslyBypassApprovals: z.boolean().optional(),
     // CPU priority
     nice: z
       .object({

test/run-mode-ui.test.ts

@@ -0,0 +1,129 @@
+/**
+ * @fileoverview Unit tests for the Codex run-mode UI surface in session-ui.js /
+ * settings-ui.js / index.html. Loads the browser modules into a vm sandbox (no
+ * real DOM) and exercises run-mode selection + Codex quick-start wiring.
+ */
+import { readFileSync } from 'node:fs';
+import { resolve } from 'node:path';
+import vm from 'node:vm';
+import { describe, expect, it } from 'vitest';
+
+function loadRunModeHarness() {
+  const elements: Record<string, any> = {};
+  const storage = new Map<string, string>();
+  const CodemanApp = function CodemanApp(this: any) {};
+
+  const context = vm.createContext({
+    CodemanApp,
+    VoiceInput: {},
+    localStorage: {
+      getItem: (key: string) => storage.get(key) ?? null,
+      setItem: (key: string, value: string) => storage.set(key, value),
+    },
+    document: {
+      getElementById: (id: string) => elements[id] ?? null,
+    },
+    console,
+  });
+
+  const settingsUi = readFileSync(resolve(import.meta.dirname, '../src/web/public/settings-ui.js'), 'utf8');
+  const sessionUi = readFileSync(resolve(import.meta.dirname, '../src/web/public/session-ui.js'), 'utf8');
+  vm.runInContext(settingsUi, context, { filename: 'settings-ui.js' });
+  vm.runInContext(sessionUi, context, { filename: 'session-ui.js' });
+
+  const runModeMenu = { classList: { remove: () => {} } };
+  const gearBtn = { className: '' };
+  const runBtn = { className: '', nextElementSibling: gearBtn };
+  const runBtnLabel = { textContent: '' };
+  elements.runModeMenu = runModeMenu;
+  elements.runBtn = runBtn;
+  elements.runBtnLabel = runBtnLabel;
+
+  const app = new (CodemanApp as any)();
+  app.loadAppSettingsFromStorage = () => ({});
+  app.saveAppSettingsToStorage = () => {};
+  app._apiPut = () => Promise.resolve();
+
+  return { app, storage, runBtnLabel };
+}
+
+describe('run mode UI', () => {
+  it('updates the visible mode when selecting Claude after server sync set Codex', async () => {
+    const { app, storage, runBtnLabel } = loadRunModeHarness();
+
+    storage.set('codeman_runMode', 'claude');
+    await app.loadAppSettingsFromServer(Promise.resolve({ runMode: 'codex' }));
+    expect(app.runMode).toBe('codex');
+    expect(runBtnLabel.textContent).toBe('Run CX');
+
+    app.setRunMode('claude');
+
+    expect(app.runMode).toBe('claude');
+    expect(runBtnLabel.textContent).toBe('Run');
+  });
+});
+
+describe('Codex quick start settings', () => {
+  it('renders Codex CLI settings in a dedicated app settings tab', () => {
+    const html = readFileSync(resolve(import.meta.dirname, '../src/web/public/index.html'), 'utf8');
+
+    expect(html).toContain('data-tab="settings-codex">Codex CLI</button>');
+
+    const claudeTab = html.match(
+      /<div class="modal-tab-content hidden" id="settings-claude">([\s\S]*?)<!-- Codex CLI Tab -->/
+    );
+    expect(claudeTab?.[1]).not.toContain('appSettingsCodexDangerouslyBypassApprovals');
+
+    const codexTab = html.match(
+      /<div class="modal-tab-content hidden" id="settings-codex">([\s\S]*?)<\/div>\s*<!-- Models Tab -->/
+    );
+    expect(codexTab?.[1]).toContain('appSettingsCodexDangerouslyBypassApprovals');
+    expect(codexTab?.[1]).not.toContain('appSettingsCodexRenderMode');
+  });
+
+  it('passes global Codex settings into quick-start config for new sessions', async () => {
+    const elements: Record<string, any> = {
+      quickStartCase: { value: 'codex-case' },
+    };
+    const requests: Array<{ url: string; body?: any }> = [];
+    const CodemanApp = function CodemanApp(this: any) {};
+
+    const context = vm.createContext({
+      CodemanApp,
+      localStorage: {
+        getItem: () => null,
+        setItem: () => {},
+      },
+      document: {
+        getElementById: (id: string) => elements[id] ?? null,
+      },
+      fetch: async (url: string, init?: { body?: string }) => {
+        requests.push({ url, body: init?.body ? JSON.parse(init.body) : undefined });
+        if (url === '/api/codex/status') return { json: async () => ({ available: true }) };
+        if (url === '/api/quick-start') return { json: async () => ({ success: true, sessionId: 'sess-1' }) };
+        throw new Error(`unexpected fetch: ${url}`);
+      },
+      console,
+    });
+
+    const sessionUi = readFileSync(resolve(import.meta.dirname, '../src/web/public/session-ui.js'), 'utf8');
+    vm.runInContext(sessionUi, context, { filename: 'session-ui.js' });
+
+    const app = new (CodemanApp as any)();
+    app.terminal = { clear: () => {}, writeln: () => {}, focus: () => {} };
+    app.loadAppSettingsFromStorage = () => ({
+      codexDangerouslyBypassApprovals: true,
+    });
+    app.getCaseSettings = () => ({});
+    app.buildEnvOverrides = () => ({});
+    app.selectSession = async () => {};
+
+    await app.runCodex();
+
+    expect(requests.find((req) => req.url === '/api/quick-start')?.body).toMatchObject({
+      caseName: 'codex-case',
+      mode: 'codex',
+      codexConfig: { dangerouslyBypassApprovals: true, renderMode: 'hybrid' },
+    });
+  });
+});