diff --git a/README.md b/README.md
index cb5e1dc..9699731 100644
--- a/README.md
+++ b/README.md
@@ -73,6 +73,7 @@ To use the interactive mode, you'll also need one of the following LLM CLI tools
 
 - **GitHub Copilot CLI** — Install the [GitHub CLI](https://cli.github.com/), authenticate with `gh auth login`, ensure Copilot access is enabled for your account/organization, then run `gh extension install github/gh-copilot`
 - **Claude Code** — [Install Claude Code](https://docs.anthropic.com/en/docs/claude-code)
+- **OpenAI Codex CLI** — [Install Codex CLI](https://github.com/openai/codex)
 
 Not using a CLI tool? See [Using with any LLM (manual)](#using-with-any-llm-manual).
 
@@ -179,6 +180,15 @@ cd promptkit
 claude "Read and execute bootstrap.md"
 ```
 
+### Using with Codex CLI
+
+Codex also supports reading the bootstrap file directly from the repo root:
+
+```bash
+cd promptkit
+codex "Read and execute bootstrap.md"
+```
+
 ### Using with any LLM (manual)
 
 If your tool doesn't support skills or file access, paste the bootstrap
diff --git a/cli/bin/cli.js b/cli/bin/cli.js
index 4c9a778..9e64730 100644
--- a/cli/bin/cli.js
+++ b/cli/bin/cli.js
@@ -55,7 +55,7 @@ program
   .description("Launch an interactive session with your LLM CLI (default)")
   .option(
     "--cli <name>",
-    "LLM CLI to use (copilot, gh-copilot, claude)"
+    "LLM CLI to use (copilot, gh-copilot, claude, codex)"
   )
   .option(
     "--dry-run",
diff --git a/cli/lib/launch.js b/cli/lib/launch.js
index 037b549..8461d52 100644
--- a/cli/lib/launch.js
+++ b/cli/lib/launch.js
@@ -8,18 +8,37 @@ const fs = require("fs");
 const path = require("path");
 const os = require("os");
 
+function pathDirs() {
+  return (process.env.PATH || "").split(path.delimiter).filter(Boolean);
+}
+
+function windowsPathExts() {
+  return (process.env.PATHEXT || ".EXE;.COM;.BAT;.CMD")
+    .split(";")
+    .map((e) => e.toLowerCase());
+}
+
+function isExactFileOnPath(fileName) {
+  for (const dir of pathDirs()) {
+    try {
+      fs.accessSync(path.join(dir, fileName), fs.constants.F_OK);
+      return true;
+    } catch {
+      // not found in this directory, continue
+    }
+  }
+  return false;
+}
+
 function isOnPath(cmd) {
   // Search PATH entries directly rather than shelling out to `which`/`where`.
   // This avoids requiring `which` to be on PATH itself (important in test
   // environments where PATH is restricted to a mock directory).
-  const pathDirs = (process.env.PATH || "").split(path.delimiter).filter(Boolean);
-  const exts = process.platform === "win32"
-    ? (process.env.PATHEXT || ".EXE;.COM;.BAT;.CMD").split(";").map((e) => e.toLowerCase())
-    : [""];
+  const exts = process.platform === "win32" ? windowsPathExts() : [""];
   // On Windows, X_OK is not meaningful — any file with a matching PATHEXT
   // extension is considered executable, so we check for existence (F_OK) only.
   const accessFlag = process.platform === "win32" ? fs.constants.F_OK : fs.constants.X_OK;
-  for (const dir of pathDirs) {
+  for (const dir of pathDirs()) {
     for (const ext of exts) {
       try {
         fs.accessSync(path.join(dir, cmd + ext), accessFlag);
@@ -32,6 +51,31 @@ function isOnPath(cmd) {
   return false;
 }
 
+function resolveSpawnCommand(cmd) {
+  if (process.platform !== "win32") return cmd;
+
+  const shim = `${cmd}.cmd`;
+  return isExactFileOnPath(shim) ? shim : cmd;
+}
+
+function quoteWindowsArg(arg) {
+  if (arg === "") return '""';
+  if (!/[\s"]/u.test(arg)) return arg;
+  return `"${arg.replace(/(\\*)"/g, '$1$1\\"').replace(/(\\+)$/g, '$1$1')}"`;
+}
+
+function spawnCli(cmd, args, options) {
+  if (process.platform === "win32" && /\.cmd$/i.test(cmd)) {
+    const comspec = process.env.ComSpec || "cmd.exe";
+    const commandLine = [cmd, ...args].map(quoteWindowsArg).join(" ");
+    return spawn(comspec, ["/d", "/s", "/c", commandLine], {
+      ...options,
+      windowsVerbatimArguments: true,
+    });
+  }
+  return spawn(cmd, args, options);
+}
+
 function detectCli() {
   // Check for GitHub Copilot CLI first (most common)
   if (isOnPath("copilot")) return "copilot";
@@ -45,6 +89,7 @@ function detectCli() {
     }
   }
   if (isOnPath("claude")) return "claude";
+  if (isOnPath("codex")) return "codex";
   return null;
 }
 
@@ -76,7 +121,8 @@ function launchInteractive(contentDir, cliName, { dryRun = false } = {}) {
       "No supported LLM CLI found on PATH.\n\n" +
         "Install one of:\n" +
         "  - GitHub Copilot CLI: gh extension install github/gh-copilot\n" +
-        "  - Claude Code: https://docs.anthropic.com/en/docs/claude-code\n\n" +
+        "  - Claude Code: https://docs.anthropic.com/en/docs/claude-code\n" +
+        "  - OpenAI Codex CLI: https://github.com/openai/codex\n\n" +
         "Alternatively, load bootstrap.md in your LLM manually from:\n" +
         `  ${contentDir}`
     );
@@ -107,7 +153,7 @@ function launchInteractive(contentDir, cliName, { dryRun = false } = {}) {
   let cmd, args;
   switch (cli) {
     case "copilot":
-      cmd = "copilot";
+      cmd = resolveSpawnCommand("copilot");
       // --add-dir grants file access to the staging directory.
       args = ["--add-dir", tmpDir, "-i", bootstrapPrompt];
       break;
@@ -117,7 +163,11 @@ function launchInteractive(contentDir, cliName, { dryRun = false } = {}) {
       break;
     case "claude":
       // --add-dir grants file access to the staging directory.
-      cmd = "claude";
+      cmd = resolveSpawnCommand("claude");
+      args = ["--add-dir", tmpDir, bootstrapPrompt];
+      break;
+    case "codex":
+      cmd = resolveSpawnCommand("codex");
       args = ["--add-dir", tmpDir, bootstrapPrompt];
       break;
     default:
@@ -142,7 +192,7 @@ function launchInteractive(contentDir, cliName, { dryRun = false } = {}) {
 
   // All CLIs are spawned from the user's original directory so the LLM
   // session reflects the directory the user was working in.
-  const child = spawn(cmd, args, {
+  const child = spawnCli(cmd, args, {
     cwd: originalCwd,
     stdio: "inherit",
   });
diff --git a/cli/package.json b/cli/package.json
index 640dfc5..0ddfe91 100644
--- a/cli/package.json
+++ b/cli/package.json
@@ -37,6 +37,7 @@
     "llm",
     "ai",
     "copilot",
+    "codex",
     "prompt-templates",
     "agentic-ai",
     "developer-tools"
diff --git a/cli/specs/design.md b/cli/specs/design.md
index e9ff5be..e730ffc 100644
--- a/cli/specs/design.md
+++ b/cli/specs/design.md
@@ -108,7 +108,7 @@ validate content availability.
   by category, and displays the result. No separate `manifest.js` module
   is used (see REQ-CLI-103).
 - The `--cli` flag documents valid values (`copilot`, `gh-copilot`,
-  `claude`) in its help text (see REQ-CLI-011).
+  `claude`, `codex`) in its help text (see REQ-CLI-011).
 
 **Key function**:
 
@@ -143,13 +143,16 @@ is inlined in `cli.js`. See REQ-CLI-101, REQ-CLI-103.*
 interactive session.
 
 **Design decisions**:
-- CLI detection uses `execFileSync` with `where` (Windows) or `which`
-  (Unix) — this is the most reliable cross-platform way to check if a
-  command exists on PATH without actually executing it.
-- The detection order (copilot → gh-copilot → claude) prioritizes GitHub
+- CLI detection uses direct PATH scanning for better Windows compatibility.
+- The detection order (copilot → gh-copilot → claude → codex) prioritizes GitHub
   Copilot CLI as the primary target. The `gh copilot` variant is checked
   by actually running `gh copilot --help` to verify the extension is
   installed, not just that `gh` exists.
+- On Windows, npm-installed CLIs such as `copilot`, `claude`, and `codex`
+  may need their `.cmd` shims invoked explicitly because Node's
+  `child_process.spawn()` does not resolve commands the same way an
+  interactive shell does. The launcher therefore prefers `<name>.cmd`
+  when present on `PATH`.
 - Content is copied to a temp directory (`os.tmpdir()` + `mkdtempSync`)
   because LLM CLIs need to read the files from their CWD, and the npm
   package's `content/` directory may be in a read-only or non-obvious
@@ -176,7 +179,7 @@ Internal helper. Checks if a command exists on PATH using platform-
 appropriate lookup.
 
 ```
-detectCli() → "copilot" | "gh-copilot" | "claude" | null
+detectCli() → "copilot" | "gh-copilot" | "claude" | "codex" | null
 ```
 Probes PATH for supported LLM CLIs in priority order.
 
@@ -397,7 +400,7 @@ Global options:
 
 Interactive options:
   --cli <name>      Override LLM CLI auto-detection
-                    Valid values: copilot, gh-copilot, claude
+                    Valid values: copilot, gh-copilot, claude, codex
 ```
 
 ### 5.2 Module Exports
@@ -405,7 +408,7 @@ Interactive options:
 **launch.js**:
 ```javascript
 module.exports = {
-  detectCli,          // () → "copilot" | "gh-copilot" | "claude" | null
+  detectCli,          // () → "copilot" | "gh-copilot" | "claude" | "codex" | null
   launchInteractive,  // (contentDir: string, cliName: string | null) → never
   copyContentToTemp   // (contentDir: string) → string (tmpDir path)
 }
diff --git a/cli/specs/requirements.md b/cli/specs/requirements.md
index 0ae456b..b7c0803 100644
--- a/cli/specs/requirements.md
+++ b/cli/specs/requirements.md
@@ -526,4 +526,4 @@ dirs) in all normal and error scenarios.
 `lib/launch.js`, and `content/` with all prompt components. The tarball
 MUST NOT contain `lib/assemble.js` or `lib/manifest.js`.
 
-**AC-005**: The CLI runs without errors on Node.js 18, 20, and 22.
+**AC-005**: The CLI runs without errors on Node.js 18, 20, and 22.
\ No newline at end of file
diff --git a/cli/specs/validation.md b/cli/specs/validation.md
index 483bed0..97176b1 100644
--- a/cli/specs/validation.md
+++ b/cli/specs/validation.md
@@ -221,6 +221,12 @@ See REQ-CLI-100.*
 - *Steps*: Ensure only `claude` is on PATH.
 - *Expected*: Returns `"claude"`.
 
+**TC-CLI-072A**: detectCli finds codex after claude is absent.
+- *Requirement*: REQ-CLI-010
+- *Type*: Unit
+- *Steps*: Ensure only `codex` is on PATH.
+- *Expected*: Returns `"codex"`.
+
 **TC-CLI-073**: detectCli returns null when nothing found.
 - *Requirement*: REQ-CLI-010
 - *Type*: Unit
@@ -275,7 +281,7 @@ See REQ-CLI-100.*
 **TC-CLI-081**: Correct command construction for each CLI.
 - *Requirement*: REQ-CLI-017
 - *Type*: Unit
-- *Steps*: Verify spawn cmd/args for `copilot`, `gh-copilot`, `claude`.
+- *Steps*: Verify spawn cmd/args for `copilot`, `gh-copilot`, `claude`, `codex`.
 - *Expected*:
   - copilot: `cmd="copilot"`, args include `"--add-dir"`, `<tmpDir>`,
     `"-i"`, `"Read and execute <abs>/bootstrap.md"`
@@ -283,6 +289,8 @@ See REQ-CLI-100.*
     `<tmpDir>`, `"-i"`, `"Read and execute <abs>/bootstrap.md"`
   - claude: `cmd="claude"`, args include `"--add-dir"`, `<tmpDir>`,
     `"Read and execute <abs>/bootstrap.md"`
+  - codex: `cmd="codex"`, args include `"--add-dir"`, `<tmpDir>`,
+    `"Read and execute <abs>/bootstrap.md"`
 
 **TC-CLI-082**: All CLIs are spawned with the user's original working directory.
 - *Requirement*: REQ-CLI-024
@@ -422,7 +430,7 @@ concern.*
 | REQ-CLI-002 | TC-CLI-001, TC-CLI-004 | High | Active |
 | REQ-CLI-003 | TC-CLI-002 | Medium | Active |
 | REQ-CLI-004 | TC-CLI-003, TC-CLI-003a | High | Active |
-| REQ-CLI-010 | TC-CLI-070 through TC-CLI-074 | High | Active |
+| REQ-CLI-010 | TC-CLI-070 through TC-CLI-074, TC-CLI-072A | High | Active |
 | REQ-CLI-011 | TC-CLI-075 | Medium | Active |
 | REQ-CLI-012 | TC-CLI-076 | High | Active |
 | REQ-CLI-013 | TC-CLI-077 | Low | Active |
diff --git a/cli/tests/launch.test.js b/cli/tests/launch.test.js
index c584525..19b9856 100644
--- a/cli/tests/launch.test.js
+++ b/cli/tests/launch.test.js
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-// cli/tests/launch.test.js — Launch module unit tests
+// cli/tests/launch.test.js ??? Launch module unit tests
 
 const { describe, it, before, after } = require("node:test");
 const assert = require("node:assert");
@@ -46,7 +46,7 @@ describe("Launch Module", () => {
   before(() => {
     assert.ok(
       fs.existsSync(contentDir),
-      "content/ must exist — run 'npm run prepare' first"
+      "content/ must exist ??? run 'npm run prepare' first"
     );
   });
 
@@ -110,8 +110,8 @@ describe("Launch Module", () => {
 
     // Run an inline Node script that requires launch.js by absolute path
     // and calls detectCli() with PATH set to mockDir only.
-    // isOnPath() in launch.js searches PATH directories directly (no `which`),
-    // so mockDir is sufficient — no system binary directories are needed.
+    // isOnPath() in launch.js scans PATH directories directly,
+    // so mockDir is sufficient and no system binary directories are needed.
     function runDetectCli() {
       const testPath = mockDir;
       const script = [
@@ -140,6 +140,14 @@ describe("Launch Module", () => {
       assert.strictEqual(runDetectCli(), "claude");
     });
 
+    it("TC-CLI-072A: detectCli finds codex after claude", () => {
+      removeMockCmd("copilot");
+      removeMockCmd("gh");
+      removeMockCmd("claude");
+      createMockCmd("codex");
+      assert.strictEqual(runDetectCli(), "codex");
+    });
+
     it("TC-CLI-074: gh without copilot extension is not detected as gh-copilot", () => {
       removeMockCmd("copilot");
       removeMockCmd("claude");
@@ -249,7 +257,7 @@ describe("Launch Module", () => {
         .join("\n");
       assert.ok(
         !/\bshell\s*:\s*true\b/.test(nonCommentLines),
-        "launch.js must not pass shell: true to spawn() — doing so splits the bootstrap prompt into multiple arguments"
+        "launch.js must not pass shell: true to spawn() ??? doing so splits the bootstrap prompt into multiple arguments"
       );
     });
   });
@@ -287,7 +295,7 @@ describe("Launch Module", () => {
       if (process.platform === "win32") {
         fs.writeFileSync(
           path.join(mockBinDir, `${binName}.cmd`),
-          `@"${process.execPath}" "${implScript}" %*\r\n`
+          `@echo off\r\n"${process.execPath}" "${implScript}" %*\r\n`
         );
       } else {
         const p = path.join(mockBinDir, binName);
@@ -322,8 +330,8 @@ describe("Launch Module", () => {
       return JSON.parse(fs.readFileSync(captureFile, "utf8"));
     }
 
-    for (const cliName of ["claude", "copilot", "gh-copilot"]) {
-      // TC-CLI-082 and TC-CLI-083 combined — run once per CLI
+    for (const cliName of ["claude", "copilot", "gh-copilot", "codex"]) {
+      // TC-CLI-082 and TC-CLI-083 combined ??? run once per CLI
       it(`TC-CLI-082/083: ${cliName} spawned with originalCwd and --add-dir for staging dir`, () => {
         const mockBinDir = path.join(cwdTestTmpDir, `mock-bin-${cliName}`);
         fs.mkdirSync(mockBinDir, { recursive: true });
@@ -371,7 +379,7 @@ describe("Launch Module", () => {
   });
 
   describe("--dry-run flag", () => {
-    for (const cliName of ["copilot", "gh-copilot", "claude"]) {
+    for (const cliName of ["copilot", "gh-copilot", "claude", "codex"]) {
       it(`TC-CLI-085: --dry-run prints spawn command for ${cliName} without launching`, () => {
         // --dry-run must print the command and args then exit 0 without
         // spawning the real LLM CLI.  We run with an empty PATH so that
@@ -379,6 +387,13 @@ describe("Launch Module", () => {
         const emptyBinDir = fs.mkdtempSync(
           path.join(os.tmpdir(), "promptkit-dryrun-empty-")
         );
+        if (process.platform === "win32" && cliName !== "gh-copilot") {
+          // Provide a local .cmd shim so resolveSpawnCommand() can find it.
+          fs.writeFileSync(
+            path.join(emptyBinDir, `${cliName}.cmd`),
+            "@echo off\r\nexit /b 0\r\n"
+          );
+        }
 
         let stdout = "";
         let exitCode = 0;
@@ -406,10 +421,25 @@ describe("Launch Module", () => {
 
           // Parse the args line as JSON so we verify structure, not wording.
           const lines = stdout.split("\n");
+          const cmdLine = lines.find((l) => l.trim().startsWith("cmd:"));
           const argsLine = lines.find((l) => l.trim().startsWith("args:"));
+          assert.ok(cmdLine, `--dry-run output should include a 'cmd:' line for ${cliName}`);
           assert.ok(argsLine, `--dry-run output should include an 'args:' line for ${cliName}`);
+          const parsedCmd = cmdLine.trim().slice("cmd:".length).trim();
           const parsedArgs = JSON.parse(argsLine.trim().slice("args:".length).trim());
 
+          if (cliName === "gh-copilot") {
+            assert.strictEqual(parsedCmd, "gh", "gh-copilot should spawn gh");
+          } else if (process.platform === "win32") {
+            assert.strictEqual(
+              parsedCmd,
+              `${cliName}.cmd`,
+              `${cliName} should spawn the Windows .cmd shim`
+            );
+          } else {
+            assert.strictEqual(parsedCmd, cliName, `${cliName} should spawn its bare command`);
+          }
+
           // The bootstrap prompt must appear as exactly one element containing bootstrap.md,
           // not split across multiple elements (the shell: true regression).
           const bootstrapArgs = parsedArgs.filter((a) => a.includes("bootstrap.md"));
@@ -436,3 +466,4 @@ describe("Launch Module", () => {
     }
   });
 });
+
diff --git a/docs/faq.md b/docs/faq.md
index eb2bebb..837d9f0 100644
--- a/docs/faq.md
+++ b/docs/faq.md
@@ -23,12 +23,12 @@ Yes. PromptKit generates standard Markdown prompts. The assembled output
 can be pasted into any LLM interface — ChatGPT, Claude, Gemini, Copilot
 Chat, or any other tool that accepts text input.
 
-Interactive mode requires GitHub Copilot CLI or Claude Code, but the
+Interactive mode requires GitHub Copilot CLI, Claude Code, or OpenAI Codex CLI, but the
 `assemble` command produces a plain text file usable anywhere.
 
 ### Do I need GitHub Copilot CLI?
 
-No. GitHub Copilot CLI (or Claude Code) is only needed for **interactive
+No. GitHub Copilot CLI (or Claude Code or OpenAI Codex CLI) is only needed for **interactive
 mode**, which launches a live prompt-building session. The `list` and
 `assemble` commands work standalone with just Node.js 18+.
 
@@ -205,8 +205,8 @@ npx promptkit list
 
 ### Interactive mode says "No supported LLM CLI found"
 
-Interactive mode requires GitHub Copilot CLI (`copilot`) or Claude Code
-(`claude`) on your PATH. Install one of them, or use `assemble` mode
+Interactive mode requires GitHub Copilot CLI (`copilot`), Claude Code
+(`claude`), or OpenAI Codex CLI (`codex`) on your PATH. Install one of them, or use `assemble` mode
 instead.
 
 ### The assembled prompt is missing a section
diff --git a/docs/getting-started.md b/docs/getting-started.md
index 203b901..ac9c758 100644
--- a/docs/getting-started.md
+++ b/docs/getting-started.md
@@ -16,7 +16,8 @@ your behalf.
 
 - **Node.js 18+** — required for the `npx` CLI
 - **Optional:** [GitHub Copilot CLI](https://docs.github.com/en/copilot)
-  or [Claude Code](https://docs.anthropic.com/en/docs/claude-code) for
+  or [Claude Code](https://docs.anthropic.com/en/docs/claude-code) or
+  [OpenAI Codex CLI](https://github.com/openai/codex) for
   interactive mode
 
 ## Quick Start
@@ -59,8 +60,8 @@ and you're running.
 npx promptkit
 ```
 
-Interactive mode auto-detects your LLM CLI (GitHub Copilot CLI or Claude
-Code), copies PromptKit's content to a temp directory, and launches an
+Interactive mode auto-detects your LLM CLI (GitHub Copilot CLI, Claude
+Code, or OpenAI Codex CLI), copies PromptKit's content to a temp directory, and launches an
 interactive session with `bootstrap.md` as the custom instruction. The
 bootstrap engine walks you through: