chore: add changeset for new release

Add changeset to release support for Codex and GitHub Copilot slash commands with YAML frontmatter and $ARGUMENTS.

.changeset/release-minor-update.md

@@ -0,0 +1,5 @@
+---
+"@fission-ai/openspec": minor
+---
+
+Add support for Codex and GitHub Copilot slash commands with YAML frontmatter and $ARGUMENTS

AGENTS.md

@@ -1,8 +1,18 @@
 <!-- OPENSPEC:START -->
 # OpenSpec Instructions
 
-This project uses OpenSpec to manage AI assistant workflows.
+These instructions are for AI assistants working in this project.
+
+Always open `@/openspec/AGENTS.md` when the request:
+- Mentions planning or proposals (words like proposal, spec, change, plan)
+- Introduces new capabilities, breaking changes, architecture shifts, or big performance/security work
+- Sounds ambiguous and you need the authoritative spec before coding
+
+Use `@/openspec/AGENTS.md` to learn:
+- How to create and apply change proposals
+- Spec format and conventions
+- Project structure and guidelines
+
+Keep this managed block so 'openspec update' can refresh the instructions.
 
-- Full guidance lives in '@/openspec/AGENTS.md'.
-- Keep this managed block so 'openspec update' can refresh the instructions.
 <!-- OPENSPEC:END -->

CHANGELOG.md

@@ -1,5 +1,11 @@
 # @fission-ai/openspec
 
+## Unreleased
+
+### Minor Changes
+
+- Add GitHub Copilot slash command support. OpenSpec now writes prompts to `.github/prompts/openspec-{proposal,apply,archive}.prompt.md` with YAML frontmatter and `$ARGUMENTS` placeholder, and refreshes them on `openspec update`.
+
 ## 0.8.1
 
 ### Patch Changes
@@ -11,6 +17,7 @@
 ### Minor Changes
 
 - c29b06d: Add Windsurf support.
+- Add Codex slash command support. OpenSpec now writes prompts directly to Codex's global directory (`~/.codex/prompts` or `$CODEX_HOME/prompts`) and refreshes them on `openspec update`.
 
 ## 0.7.0
 

README.md

@@ -95,6 +95,8 @@ These tools have built-in OpenSpec commands. Select the OpenSpec integration whe
 | **OpenCode** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` |
 | **Kilo Code** | `/openspec-proposal.md`, `/openspec-apply.md`, `/openspec-archive.md` (`.kilocode/workflows/`) |
 | **Windsurf** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (`.windsurf/workflows/`) |
+| **Codex** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (global: `~/.codex/prompts`, auto-installed) |
+| **GitHub Copilot** | `/openspec-proposal`, `/openspec-apply`, `/openspec-archive` (`.github/prompts/`) |
 
 Kilo Code discovers team workflows automatically. Save the generated files under `.kilocode/workflows/` and trigger them from the command palette with `/openspec-proposal.md`, `/openspec-apply.md`, or `/openspec-archive.md`.
 
@@ -103,7 +105,7 @@ These tools automatically read workflow instructions from `openspec/AGENTS.md`.
 
 | Tools |
 |-------|
-| Codex • Amp • Jules • Gemini CLI • GitHub Copilot • Others |
+| Amp • Jules • Gemini CLI • Others |
 
 ### Install & Initialize
 
@@ -207,7 +209,7 @@ Or run the command yourself in terminal:
 $ openspec archive add-profile-filters --yes  # Archive the completed change without prompts
 ```
 
-**Note:** Tools with native slash commands (Claude Code, Cursor) can use the shortcuts shown. All other tools work with natural language requests to "create an OpenSpec proposal", "apply the OpenSpec change", or "archive the change".
+**Note:** Tools with native slash commands (Claude Code, Cursor, Codex) can use the shortcuts shown. All other tools work with natural language requests to "create an OpenSpec proposal", "apply the OpenSpec change", or "archive the change".
 
 ## Command Reference
 

openspec/changes/add-codex-slash-command-support/proposal.md

@@ -0,0 +1,25 @@
+## Why
+- Codex (the VS Code extension formerly known as Codeium Chat) exposes "slash commands" by reading Markdown prompt files from `~/.codex/prompts/`. Each file name becomes the `/command` users can run, with YAML frontmatter for metadata (`description`, `argument-hint`) and `$ARGUMENTS` to capture user input. The workflow screenshot shared by Kevin Kern ("Codex problem analyzer") shows the format OpenSpec should target so teams can invoke curated workflows straight from the chat palette.
+- Teams already rely on OpenSpec to manage the slash-command surface area for Claude, Cursor, OpenCode, Kilo Code, and Windsurf. Leaving Codex out forces them to manually copy/paste OpenSpec guardrails into `~/.codex/prompts/*.md`, which drifts quickly and undermines the "single source of truth" promise of the CLI.
+- Codex commands live outside the repository (under the user's home directory), so shipping an automated configurator that both scaffolds the prompts and keeps them refreshed via `openspec update` eliminates error-prone manual steps and keeps OpenSpec instructions synchronized across assistants.
+
+## What Changes
+- Add Codex to the `openspec init` tool picker with the same "already configured" detection we use for other editors, wiring an implementation that writes managed Markdown prompts directly to Codex's global directory (`~/.codex/prompts` or `$CODEX_HOME/prompts`) with OpenSpec marker blocks.
+- Produce three Codex prompt files—`openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`—whose content mirrors the shared slash-command templates while using YAML frontmatter (`description` and `argument-hint` fields) and `$ARGUMENTS` to capture all arguments as a single string (matching the GitHub Copilot pattern and official Codex specification).
+- Document Codex's global-only discovery and that OpenSpec writes prompts directly to `~/.codex/prompts` (or `$CODEX_HOME/prompts`).
+- Teach `openspec update` to refresh existing Codex prompts in-place (and only when they already exist) in the global directory, updating both frontmatter and body.
+- Document Codex support alongside other slash-command integrations and add regression coverage that exercises init/update behaviour against a temporary global prompts directory via `CODEX_HOME`.
+
+## Impact
+- Specs: `cli-init`, `cli-update`
+- Code: `src/core/config.ts`, `src/core/configurators/slash/*`, `src/core/templates/slash-command-templates.ts`, CLI tool summaries, docs
+- Tests: integration coverage for Codex prompt scaffolding and refresh logic
+- Docs: README and CHANGELOG entries announcing Codex slash-command support
+
+## Current Spec Reference
+- `specs/cli-init/spec.md`
+  - Requirements cover init UX, directory scaffolding, AI tool configuration, and the existing slash-command support for Claude Code, Cursor, and OpenCode.
+  - Our `## MODIFIED` delta in `changes/.../specs/cli-init/spec.md` copies the full "Slash Command Configuration" requirement (header, description, and all scenarios) before appending the new Codex scenario so archiving will retain every prior scenario.
+- `specs/cli-update/spec.md`
+  - Requirements define update preconditions, template refresh behavior, and slash-command refresh logic for Claude Code, Cursor, and OpenCode.
+  - The corresponding delta preserves the entire "Slash Command Updates" requirement while adding the Codex refresh scenario, ensuring the archive workflow replaces the block without losing the existing scenarios or the "Missing slash command file" guardrail.

openspec/changes/add-codex-slash-command-support/specs/cli-init/spec.md

@@ -0,0 +1,56 @@
+## MODIFIED Requirements
+### Requirement: AI Tool Configuration
+The command SHALL configure AI coding assistants with OpenSpec instructions using a marker system.
+#### Scenario: Prompting for AI tool selection
+- **WHEN** run interactively
+- **THEN** prompt the user with "Which AI tools do you use?" using a multi-select menu
+- **AND** list every available tool with a checkbox:
+  - Claude Code (creates or refreshes CLAUDE.md and slash commands)
+  - Cursor (creates or refreshes `.cursor/commands/*` slash commands)
+  - OpenCode (creates or refreshes `.opencode/command/openspec-*.md` slash commands)
+  - Windsurf (creates or refreshes `.windsurf/workflows/openspec-*.md` workflows)
+  - Kilo Code (creates or refreshes `.kilocode/workflows/openspec-*.md` workflows)
+  - Codex (creates or refreshes global prompts at `~/.codex/prompts/openspec-*.md`)
+  - AGENTS.md standard (creates or refreshes AGENTS.md with OpenSpec markers)
+- **AND** show "(already configured)" beside tools whose managed files exist so users understand selections will refresh content
+- **AND** treat disabled tools as "coming soon" and keep them unselectable
+- **AND** allow confirming with Enter after selecting one or more tools
+
+### Requirement: Slash Command Configuration
+The init command SHALL generate slash command files for supported editors using shared templates.
+
+#### Scenario: Generating slash commands for Claude Code
+- **WHEN** the user selects Claude Code during initialization
+- **THEN** create `.claude/commands/openspec/proposal.md`, `.claude/commands/openspec/apply.md`, and `.claude/commands/openspec/archive.md`
+- **AND** populate each file from shared templates so command text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for Cursor
+- **WHEN** the user selects Cursor during initialization
+- **THEN** create `.cursor/commands/openspec-proposal.md`, `.cursor/commands/openspec-apply.md`, and `.cursor/commands/openspec-archive.md`
+- **AND** populate each file from shared templates so command text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for OpenCode
+- **WHEN** the user selects OpenCode during initialization
+- **THEN** create `.opencode/command/openspec-proposal.md`, `.opencode/command/openspec-apply.md`, and `.opencode/command/openspec-archive.md`
+- **AND** populate each file from shared templates so command text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for Windsurf
+- **WHEN** the user selects Windsurf during initialization
+- **THEN** create `.windsurf/workflows/openspec-proposal.md`, `.windsurf/workflows/openspec-apply.md`, and `.windsurf/workflows/openspec-archive.md`
+- **AND** populate each file from shared templates (wrapped in OpenSpec markers) so workflow text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for Kilo Code
+- **WHEN** the user selects Kilo Code during initialization
+- **THEN** create `.kilocode/workflows/openspec-proposal.md`, `.kilocode/workflows/openspec-apply.md`, and `.kilocode/workflows/openspec-archive.md`
+- **AND** populate each file from shared templates (wrapped in OpenSpec markers) so workflow text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for Codex
+- **WHEN** the user selects Codex during initialization
+- **THEN** create global prompt files at `~/.codex/prompts/openspec-proposal.md`, `~/.codex/prompts/openspec-apply.md`, and `~/.codex/prompts/openspec-archive.md` (or under `$CODEX_HOME/prompts` if set)
+- **AND** populate each file from shared templates that map the first numbered placeholder (`$1`) to the primary user input (e.g., change identifier or question text)
+- **AND** wrap the generated content in OpenSpec markers so `openspec update` can refresh the prompts without touching surrounding custom notes

openspec/changes/add-codex-slash-command-support/specs/cli-update/spec.md

@@ -0,0 +1,41 @@
+## MODIFIED Requirements
+### Requirement: Slash Command Updates
+The update command SHALL refresh existing slash command files for configured tools without creating new ones.
+
+#### Scenario: Updating slash commands for Claude Code
+- **WHEN** `.claude/commands/openspec/` contains `proposal.md`, `apply.md`, and `archive.md`
+- **THEN** refresh each file using shared templates
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Updating slash commands for Cursor
+- **WHEN** `.cursor/commands/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh each file using shared templates
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Updating slash commands for OpenCode
+- **WHEN** `.opencode/command/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh each file using shared templates
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Updating slash commands for Windsurf
+- **WHEN** `.windsurf/workflows/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh each file using shared templates wrapped in OpenSpec markers
+- **AND** ensure templates include instructions for the relevant workflow stage
+- **AND** skip creating missing files (the update command only refreshes what already exists)
+
+#### Scenario: Updating slash commands for Kilo Code
+- **WHEN** `.kilocode/workflows/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh each file using shared templates wrapped in OpenSpec markers
+- **AND** ensure templates include instructions for the relevant workflow stage
+- **AND** skip creating missing files (the update command only refreshes what already exists)
+
+#### Scenario: Updating slash commands for Codex
+- **GIVEN** the global Codex prompt directory contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **WHEN** a user runs `openspec update`
+- **THEN** refresh each file using the shared slash-command templates (including placeholder guidance)
+- **AND** preserve any unmanaged content outside the OpenSpec marker block
+- **AND** skip creation when a Codex prompt file is missing
+
+#### Scenario: Missing slash command file
+- **WHEN** a tool lacks a slash command file
+- **THEN** do not create a new file during update

openspec/changes/add-codex-slash-command-support/tasks.md

@@ -0,0 +1,19 @@
+## 1. CLI integration
+- [x] 1.1 Add Codex to the init tool picker with display text that clarifies prompts live in the global `.codex/prompts/` directory and implement "already configured" detection by checking for managed Codex prompt files.
+- [x] 1.2 Implement a `CodexSlashCommandConfigurator` that writes `.codex/prompts/openspec-{proposal,apply,archive}.md`, ensuring the prompt directory exists and wrapping content in OpenSpec markers.
+// (No helper command required)
+- [x] 1.3 Register the configurator with the slash-command registry and include Codex in init/update wiring so both commands invoke the new configurator when appropriate.
+
+## 2. Prompt templates
+- [x] 2.1 Extend the shared slash-command templates (or add a Codex-specific wrapper) to inject numbered placeholders (`$1`, `$2`, …) where Codex expects user-supplied arguments.
+- [x] 2.2 Verify generated Markdown stays within Codex's formatting expectations (no front matter, heading-first layout) and matches the problem-analyzer style shown in the reference screenshot.
+
+## 3. Update support & tests
+- [x] 3.1 Update the `openspec update` flow to refresh existing Codex prompts without creating new ones when files are missing.
+- [x] 3.2 Add integration coverage that exercises init/update against a temporary global Codex prompts directory by setting `CODEX_HOME`, asserting marker preservation and idempotent updates.
+- [x] 3.3 Document Codex's global-only discovery and automatic installation in README and CHANGELOG.
+- [x] 3.3 Confirm error handling surfaces clear paths when the CLI cannot write to the Codex prompt directory (permissions, missing home directory, etc.).
+
+## 4. Documentation
+- [x] 4.1 Document Codex slash-command support in the README and changelog alongside other assistant integrations.
+- [x] 4.2 Add a release note snippet that points Codex users to the generated `/openspec-proposal`, `/openspec-apply`, and `/openspec-archive` commands.

openspec/changes/add-github-copilot-prompts/proposal.md

@@ -0,0 +1,25 @@
+## Why
+- GitHub Copilot supports custom slash commands through markdown files in `.github/prompts/<name>.prompt.md`. Each file includes YAML frontmatter with a `description` label and uses `$ARGUMENTS` to capture user input. This format allows teams to expose curated workflows directly in Copilot's chat interface.
+- Teams already rely on OpenSpec to manage slash-command configurations for Claude Code, Cursor, OpenCode, Codex, Kilo Code, and Windsurf. Excluding GitHub Copilot forces developers to manually maintain OpenSpec prompts in `.github/prompts/`, which leads to drift and undermines OpenSpec's "single source of truth" promise.
+- GitHub Copilot discovers prompts from the repository's `.github/prompts/` directory, making it straightforward to version control and share across the team. Adding automated generation and refresh through `openspec init` and `openspec update` eliminates manual synchronization and keeps OpenSpec instructions consistent across all AI assistants.
+
+## What Changes
+- Add GitHub Copilot to the `openspec init` tool picker with "already configured" detection similar to other editors, wiring an implementation that writes managed Markdown prompt files to `.github/prompts/` with OpenSpec marker blocks.
+- Generate three GitHub Copilot prompt files—`openspec-proposal.prompt.md`, `openspec-apply.prompt.md`, and `openspec-archive.prompt.md`—whose content mirrors shared slash-command templates while conforming to Copilot's frontmatter and `$ARGUMENTS` placeholder convention.
+- Document GitHub Copilot's repository-based discovery and that OpenSpec writes prompts to `.github/prompts/` with managed blocks.
+- Teach `openspec update` to refresh existing GitHub Copilot prompts in-place (only when they already exist) in the repository's `.github/prompts/` directory.
+- Document GitHub Copilot support alongside other slash-command integrations and add test coverage that exercises init/update behavior for `.github/prompts/` files.
+
+## Impact
+- Specs: `cli-init`, `cli-update`
+- Code: `src/core/configurators/slash/github-copilot.ts` (new), `src/core/configurators/slash/registry.ts`, `src/core/templates/slash-command-templates.ts`, CLI tool summaries, docs
+- Tests: integration coverage for GitHub Copilot prompt scaffolding and refresh logic
+- Docs: README and CHANGELOG entries announcing GitHub Copilot slash-command support
+
+## Current Spec Reference
+- `specs/cli-init/spec.md`
+  - Requirements cover init UX, directory scaffolding, AI tool configuration, and existing slash-command support for Claude Code, Cursor, OpenCode, Codex, Kilo Code, and Windsurf.
+  - Our `## MODIFIED` delta in `changes/.../specs/cli-init/spec.md` will copy the full "Slash Command Configuration" requirement (header, description, and all scenarios) before appending the new GitHub Copilot scenario so archiving retains every prior scenario.
+- `specs/cli-update/spec.md`
+  - Requirements define update preconditions, template refresh behavior, and slash-command refresh logic for existing tools.
+  - The corresponding delta preserves the entire "Slash Command Updates" requirement while adding the GitHub Copilot refresh scenario, ensuring the archive workflow replaces the block without losing existing scenarios or the "Missing slash command file" guardrail.

openspec/changes/add-github-copilot-prompts/specs/cli-init/spec.md

@@ -0,0 +1,30 @@
+## MODIFIED Requirements
+
+### Requirement: Slash Command Configuration
+The init command SHALL generate slash command files for supported editors using shared templates.
+
+#### Scenario: Generating slash commands for Claude Code
+- **WHEN** the user selects Claude Code during initialization
+- **THEN** create `.claude/commands/openspec/proposal.md`, `.claude/commands/openspec/apply.md`, and `.claude/commands/openspec/archive.md`
+- **AND** populate each file from shared templates so command text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for Cursor
+- **WHEN** the user selects Cursor during initialization
+- **THEN** create `.cursor/commands/openspec-proposal.md`, `.cursor/commands/openspec-apply.md`, and `.cursor/commands/openspec-archive.md`
+- **AND** populate each file from shared templates so command text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for OpenCode
+- **WHEN** the user selects OpenCode during initialization
+- **THEN** create `.opencode/commands/openspec-proposal.md`, `.opencode/commands/openspec-apply.md`, and `.opencode/commands/openspec-archive.md`
+- **AND** populate each file from shared templates so command text matches other tools
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage
+
+#### Scenario: Generating slash commands for GitHub Copilot
+- **WHEN** the user selects GitHub Copilot during initialization
+- **THEN** create `.github/prompts/openspec-proposal.prompt.md`, `.github/prompts/openspec-apply.prompt.md`, and `.github/prompts/openspec-archive.prompt.md`
+- **AND** populate each file with YAML frontmatter containing a `description` field that summarizes the workflow stage
+- **AND** include `$ARGUMENTS` placeholder to capture user input
+- **AND** wrap the shared template body with OpenSpec markers so `openspec update` can refresh the content
+- **AND** each template includes instructions for the relevant OpenSpec workflow stage

openspec/changes/add-github-copilot-prompts/specs/cli-update/spec.md

@@ -0,0 +1,29 @@
+## MODIFIED Requirements
+
+### Requirement: Slash Command Updates
+The update command SHALL refresh existing slash command files for configured tools without creating new ones.
+
+#### Scenario: Updating slash commands for Claude Code
+- **WHEN** `.claude/commands/openspec/` contains `proposal.md`, `apply.md`, and `archive.md`
+- **THEN** refresh each file using shared templates
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Updating slash commands for Cursor
+- **WHEN** `.cursor/commands/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh each file using shared templates
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Updating slash commands for OpenCode
+- **WHEN** `.opencode/command/` contains `openspec-proposal.md`, `openspec-apply.md`, and `openspec-archive.md`
+- **THEN** refresh each file using shared templates
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Updating slash commands for GitHub Copilot
+- **WHEN** `.github/prompts/` contains `openspec-proposal.prompt.md`, `openspec-apply.prompt.md`, and `openspec-archive.prompt.md`
+- **THEN** refresh each file using shared templates while preserving the YAML frontmatter
+- **AND** update only the OpenSpec-managed block between markers
+- **AND** ensure templates include instructions for the relevant workflow stage
+
+#### Scenario: Missing slash command file
+- **WHEN** a tool lacks a slash command file
+- **THEN** do not create a new file during update

openspec/changes/add-github-copilot-prompts/tasks.md

@@ -0,0 +1,30 @@
+## Implementation Tasks
+
+- [x] Create `src/core/configurators/slash/github-copilot.ts` implementing `SlashCommandConfigurator` base class
+  - Implement `getRelativePath()` to return `.github/prompts/openspec-{proposal,apply,archive}.prompt.md`
+  - Implement `getFrontmatter()` to generate YAML frontmatter with `description` field and include `$ARGUMENTS` placeholder
+  - Implement `generateAll()` to create `.github/prompts/` directory and write three prompt files with frontmatter, markers, and shared template bodies
+  - Implement `updateExisting()` to refresh only the managed block between markers while preserving frontmatter
+  - Set `toolId = "github-copilot"` and `isAvailable = true`
+
+- [x] Register GitHub Copilot configurator in `src/core/configurators/slash/registry.ts`
+  - Import `GitHubCopilotSlashCommandConfigurator`
+  - Add to `SLASH_COMMAND_CONFIGURATORS` array
+  - Update tool picker display name to "GitHub Copilot"
+
+- [x] Update `src/core/init.ts` to include GitHub Copilot in the AI tool selection prompt
+  - Add GitHub Copilot to the available tools list with detection for existing `.github/prompts/openspec-*.prompt.md` files
+  - Display "(already configured)" when prompt files exist
+
+- [x] Update `src/core/update.ts` to refresh GitHub Copilot prompts when they exist
+  - Call `updateExisting()` for GitHub Copilot configurator when `.github/prompts/` contains OpenSpec prompt files
+
+- [x] Add integration tests for GitHub Copilot slash command generation
+  - Test `generateAll()` creates three prompt files with correct structure (frontmatter + markers + body)
+  - Test `updateExisting()` preserves frontmatter and only updates managed blocks
+  - Test that missing prompt files are not created during update
+
+- [x] Update documentation
+  - Add GitHub Copilot to README slash-command support table
+  - Document `.github/prompts/` as the discovery location
+  - Add CHANGELOG entry for GitHub Copilot support

src/core/config.ts

@@ -22,5 +22,7 @@ export const AI_TOOLS: AIToolOption[] = [
   { name: 'OpenCode', value: 'opencode', available: true, successLabel: 'OpenCode' },
   { name: 'Kilo Code', value: 'kilocode', available: true, successLabel: 'Kilo Code' },
   { name: 'Windsurf', value: 'windsurf', available: true, successLabel: 'Windsurf' },
-  { name: 'AGENTS.md (works with Codex, Amp, VS Code, GitHub Copilot, …)', value: 'agents', available: false, successLabel: 'your AGENTS.md-compatible assistant' }
+  { name: 'Codex', value: 'codex', available: true, successLabel: 'Codex' },
+  { name: 'GitHub Copilot', value: 'github-copilot', available: true, successLabel: 'GitHub Copilot' },
+  { name: 'AGENTS.md (works with Amp, VS Code, …)', value: 'agents', available: false, successLabel: 'your AGENTS.md-compatible assistant' }
 ];

src/core/configurators/slash/base.ts

@@ -67,7 +67,14 @@ export abstract class SlashCommandConfigurator {
   protected abstract getRelativePath(id: SlashCommandId): string;
   protected abstract getFrontmatter(id: SlashCommandId): string | undefined;
 
-  private async updateBody(filePath: string, body: string): Promise<void> {
+  // Resolve absolute path for a given slash command target. Subclasses may override
+  // to redirect to tool-specific locations (e.g., global directories).
+  resolveAbsolutePath(projectPath: string, id: SlashCommandId): string {
+    const rel = this.getRelativePath(id);
+    return path.join(projectPath, rel);
+  }
+
+  protected async updateBody(filePath: string, body: string): Promise<void> {
     const content = await FileSystemUtils.readFile(filePath);
     const startIndex = content.indexOf(OPENSPEC_MARKERS.start);
     const endIndex = content.indexOf(OPENSPEC_MARKERS.end);

src/core/configurators/slash/codex.ts

@@ -0,0 +1,119 @@
+import path from "path";
+import os from "os";
+import { SlashCommandConfigurator } from "./base.js";
+import { SlashCommandId, TemplateManager } from "../../templates/index.js";
+import { FileSystemUtils } from "../../../utils/file-system.js";
+import { OPENSPEC_MARKERS } from "../../config.js";
+
+const FILE_PATHS: Record<SlashCommandId, string> = {
+  proposal: ".codex/prompts/openspec-proposal.md",
+  apply: ".codex/prompts/openspec-apply.md",
+  archive: ".codex/prompts/openspec-archive.md",
+};
+
+export class CodexSlashCommandConfigurator extends SlashCommandConfigurator {
+  readonly toolId = "codex";
+  readonly isAvailable = true;
+
+  protected getRelativePath(id: SlashCommandId): string {
+    return FILE_PATHS[id];
+  }
+
+  protected getFrontmatter(id: SlashCommandId): string | undefined {
+    // Codex supports YAML frontmatter with description and argument-hint fields,
+    // plus $ARGUMENTS to capture all arguments as a single string.
+    const frontmatter: Record<SlashCommandId, string> = {
+      proposal: `---
+description: Scaffold a new OpenSpec change and validate strictly.
+argument-hint: request or feature description
+---
+
+$ARGUMENTS`,
+      apply: `---
+description: Implement an approved OpenSpec change and keep tasks in sync.
+argument-hint: change-id
+---
+
+$ARGUMENTS`,
+      archive: `---
+description: Archive a deployed OpenSpec change and update specs.
+argument-hint: change-id
+---
+
+$ARGUMENTS`,
+    };
+    return frontmatter[id];
+  }
+
+  private getGlobalPromptsDir(): string {
+    const home = (process.env.CODEX_HOME && process.env.CODEX_HOME.trim())
+      ? process.env.CODEX_HOME.trim()
+      : path.join(os.homedir(), ".codex");
+    return path.join(home, "prompts");
+  }
+
+  // Codex discovers prompts globally. Generate directly in the global directory
+  // and wrap shared body with markers.
+  async generateAll(projectPath: string, _openspecDir: string): Promise<string[]> {
+    const createdOrUpdated: string[] = [];
+    for (const target of this.getTargets()) {
+      const body = TemplateManager.getSlashCommandBody(target.id).trim();
+      const promptsDir = this.getGlobalPromptsDir();
+      const filePath = path.join(promptsDir, path.basename(target.path));
+
+      await FileSystemUtils.createDirectory(path.dirname(filePath));
+
+      if (await FileSystemUtils.fileExists(filePath)) {
+        await this.updateFullFile(filePath, target.id, body);
+      } else {
+        const frontmatter = this.getFrontmatter(target.id);
+        const sections: string[] = [];
+        if (frontmatter) sections.push(frontmatter.trim());
+        sections.push(`${OPENSPEC_MARKERS.start}\n${body}\n${OPENSPEC_MARKERS.end}`);
+        await FileSystemUtils.writeFile(filePath, sections.join("\n") + "\n");
+      }
+
+      createdOrUpdated.push(target.path);
+    }
+    return createdOrUpdated;
+  }
+
+  async updateExisting(projectPath: string, _openspecDir: string): Promise<string[]> {
+    const updated: string[] = [];
+    for (const target of this.getTargets()) {
+      const promptsDir = this.getGlobalPromptsDir();
+      const filePath = path.join(promptsDir, path.basename(target.path));
+      if (await FileSystemUtils.fileExists(filePath)) {
+        const body = TemplateManager.getSlashCommandBody(target.id).trim();
+        await this.updateFullFile(filePath, target.id, body);
+        updated.push(target.path);
+      }
+    }
+    return updated;
+  }
+
+  // Update both frontmatter and body in an existing file
+  private async updateFullFile(filePath: string, id: SlashCommandId, body: string): Promise<void> {
+    const content = await FileSystemUtils.readFile(filePath);
+    const startIndex = content.indexOf(OPENSPEC_MARKERS.start);
+
+    if (startIndex === -1) {
+      throw new Error(`Missing OpenSpec start marker in ${filePath}`);
+    }
+
+    // Replace everything before the start marker with the new frontmatter
+    const frontmatter = this.getFrontmatter(id);
+    const sections: string[] = [];
+    if (frontmatter) sections.push(frontmatter.trim());
+    sections.push(`${OPENSPEC_MARKERS.start}\n${body}\n${OPENSPEC_MARKERS.end}`);
+
+    await FileSystemUtils.writeFile(filePath, sections.join("\n") + "\n");
+  }
+
+  // Resolve to the global prompts location for configuration detection
+  resolveAbsolutePath(_projectPath: string, id: SlashCommandId): string {
+    const promptsDir = this.getGlobalPromptsDir();
+    const fileName = path.basename(FILE_PATHS[id]);
+    return path.join(promptsDir, fileName);
+  }
+}

src/core/configurators/slash/github-copilot.ts

@@ -0,0 +1,39 @@
+import { SlashCommandConfigurator } from './base.js';
+import { SlashCommandId } from '../../templates/index.js';
+
+const FILE_PATHS: Record<SlashCommandId, string> = {
+  proposal: '.github/prompts/openspec-proposal.prompt.md',
+  apply: '.github/prompts/openspec-apply.prompt.md',
+  archive: '.github/prompts/openspec-archive.prompt.md'
+};
+
+const FRONTMATTER: Record<SlashCommandId, string> = {
+  proposal: `---
+description: Scaffold a new OpenSpec change and validate strictly.
+---
+
+$ARGUMENTS`,
+  apply: `---
+description: Implement an approved OpenSpec change and keep tasks in sync.
+---
+
+$ARGUMENTS`,
+  archive: `---
+description: Archive a deployed OpenSpec change and update specs.
+---
+
+$ARGUMENTS`
+};
+
+export class GitHubCopilotSlashCommandConfigurator extends SlashCommandConfigurator {
+  readonly toolId = 'github-copilot';
+  readonly isAvailable = true;
+
+  protected getRelativePath(id: SlashCommandId): string {
+    return FILE_PATHS[id];
+  }
+
+  protected getFrontmatter(id: SlashCommandId): string {
+    return FRONTMATTER[id];
+  }
+}

src/core/configurators/slash/registry.ts

@@ -4,6 +4,8 @@ import { CursorSlashCommandConfigurator } from './cursor.js';
 import { WindsurfSlashCommandConfigurator } from './windsurf.js';
 import { KiloCodeSlashCommandConfigurator } from './kilocode.js';
 import { OpenCodeSlashCommandConfigurator } from './opencode.js';
+import { CodexSlashCommandConfigurator } from './codex.js';
+import { GitHubCopilotSlashCommandConfigurator } from './github-copilot.js';
 
 export class SlashCommandRegistry {
   private static configurators: Map<string, SlashCommandConfigurator> = new Map();
@@ -14,12 +16,16 @@ export class SlashCommandRegistry {
     const windsurf = new WindsurfSlashCommandConfigurator();
     const kilocode = new KiloCodeSlashCommandConfigurator();
     const opencode = new OpenCodeSlashCommandConfigurator();
+    const codex = new CodexSlashCommandConfigurator();
+    const githubCopilot = new GitHubCopilotSlashCommandConfigurator();
 
     this.configurators.set(claude.toolId, claude);
     this.configurators.set(cursor.toolId, cursor);
     this.configurators.set(windsurf.toolId, windsurf);
     this.configurators.set(kilocode.toolId, kilocode);
     this.configurators.set(opencode.toolId, opencode);
+    this.configurators.set(codex.toolId, codex);
+    this.configurators.set(githubCopilot.toolId, githubCopilot);
   }
 
   static register(configurator: SlashCommandConfigurator): void {

src/core/init.ts

@@ -516,7 +516,7 @@ export class InitCommand {
         value: OTHER_TOOLS_HEADING_VALUE,
         label: {
           primary:
-            'Other tools (use Universal AGENTS.md for Codex, Amp, VS Code, GitHub Copilot, …)',
+            'Other tools (use Universal AGENTS.md for Amp, VS Code, GitHub Copilot, …)',
         },
         selectable: false,
       },
@@ -564,8 +564,11 @@ export class InitCommand {
     const slashConfigurator = SlashCommandRegistry.get(toolId);
     if (!slashConfigurator) return false;
     for (const target of slashConfigurator.getTargets()) {
-      if (await FileSystemUtils.fileExists(path.join(projectPath, target.path)))
-        return true;
+      const absolute = slashConfigurator.resolveAbsolutePath(
+        projectPath,
+        target.id
+      );
+      if (await FileSystemUtils.fileExists(absolute)) return true;
     }
     return false;
   }
@@ -748,6 +751,16 @@ export class InitCommand {
         '────────────────────────────────────────────────────────────\n'
       )
     );
+
+    // Codex heads-up: prompts installed globally
+    const selectedToolIds = new Set(selectedTools.map((t) => t.value));
+    if (selectedToolIds.has('codex')) {
+      console.log(PALETTE.white('Codex setup note'));
+      console.log(
+        PALETTE.midGray('Prompts installed to ~/.codex/prompts (or $CODEX_HOME/prompts).')
+      );
+      console.log();
+    }
   }
 
   private formatToolNames(tools: AIToolOption[]): string {

src/core/update.ts

@@ -123,5 +123,7 @@ export class UpdateCommand {
     }
 
     console.log(summaryParts.join(' | '));
+
+    // No additional notes
   }
 }

test/core/init.test.ts

@@ -36,6 +36,7 @@ function queueSelections(...values: string[]) {
 describe('InitCommand', () => {
   let testDir: string;
   let initCommand: InitCommand;
+  let prevCodexHome: string | undefined;
 
   beforeEach(async () => {
     testDir = path.join(os.tmpdir(), `openspec-init-test-${Date.now()}`);
@@ -44,6 +45,10 @@ describe('InitCommand', () => {
     mockPrompt.mockReset();
     initCommand = new InitCommand({ prompt: mockPrompt });
 
+    // Route Codex global directory into the test sandbox
+    prevCodexHome = process.env.CODEX_HOME;
+    process.env.CODEX_HOME = path.join(testDir, '.codex');
+
     // Mock console.log to suppress output during tests
     vi.spyOn(console, 'log').mockImplementation(() => {});
   });
@@ -51,6 +56,8 @@ describe('InitCommand', () => {
   afterEach(async () => {
     await fs.rm(testDir, { recursive: true, force: true });
     vi.restoreAllMocks();
+    if (prevCodexHome === undefined) delete process.env.CODEX_HOME;
+    else process.env.CODEX_HOME = prevCodexHome;
   });
 
   describe('execute', () => {
@@ -309,6 +316,48 @@ describe('InitCommand', () => {
       expect(archiveContent).toContain('openspec list --specs');
     });
 
+    it('should create Codex prompts with templates and placeholders', async () => {
+      queueSelections('codex', DONE);
+
+      await initCommand.execute(testDir);
+
+      const proposalPath = path.join(
+        testDir,
+        '.codex/prompts/openspec-proposal.md'
+      );
+      const applyPath = path.join(
+        testDir,
+        '.codex/prompts/openspec-apply.md'
+      );
+      const archivePath = path.join(
+        testDir,
+        '.codex/prompts/openspec-archive.md'
+      );
+
+      expect(await fileExists(proposalPath)).toBe(true);
+      expect(await fileExists(applyPath)).toBe(true);
+      expect(await fileExists(archivePath)).toBe(true);
+
+      const proposalContent = await fs.readFile(proposalPath, 'utf-8');
+      expect(proposalContent).toContain('description: Scaffold a new OpenSpec change and validate strictly.');
+      expect(proposalContent).toContain('argument-hint: request or feature description');
+      expect(proposalContent).toContain('$ARGUMENTS');
+      expect(proposalContent).toContain('<!-- OPENSPEC:START -->');
+      expect(proposalContent).toContain('**Guardrails**');
+
+      const applyContent = await fs.readFile(applyPath, 'utf-8');
+      expect(applyContent).toContain('description: Implement an approved OpenSpec change and keep tasks in sync.');
+      expect(applyContent).toContain('argument-hint: change-id');
+      expect(applyContent).toContain('$ARGUMENTS');
+      expect(applyContent).toContain('Work through tasks sequentially');
+
+      const archiveContent = await fs.readFile(archivePath, 'utf-8');
+      expect(archiveContent).toContain('description: Archive a deployed OpenSpec change and update specs.');
+      expect(archiveContent).toContain('argument-hint: change-id');
+      expect(archiveContent).toContain('$ARGUMENTS');
+      expect(archiveContent).toContain('openspec archive <id> --yes');
+    });
+
     it('should create Kilo Code workflows with templates', async () => {
       queueSelections('kilocode', DONE);
 
@@ -345,6 +394,48 @@ describe('InitCommand', () => {
       expect(archiveContent).not.toContain('---\n');
     });
 
+    it('should create GitHub Copilot prompt files with templates', async () => {
+      queueSelections('github-copilot', DONE);
+
+      await initCommand.execute(testDir);
+
+      const proposalPath = path.join(
+        testDir,
+        '.github/prompts/openspec-proposal.prompt.md'
+      );
+      const applyPath = path.join(
+        testDir,
+        '.github/prompts/openspec-apply.prompt.md'
+      );
+      const archivePath = path.join(
+        testDir,
+        '.github/prompts/openspec-archive.prompt.md'
+      );
+
+      expect(await fileExists(proposalPath)).toBe(true);
+      expect(await fileExists(applyPath)).toBe(true);
+      expect(await fileExists(archivePath)).toBe(true);
+
+      const proposalContent = await fs.readFile(proposalPath, 'utf-8');
+      expect(proposalContent).toContain('---');
+      expect(proposalContent).toContain('description: Scaffold a new OpenSpec change and validate strictly.');
+      expect(proposalContent).toContain('$ARGUMENTS');
+      expect(proposalContent).toContain('<!-- OPENSPEC:START -->');
+      expect(proposalContent).toContain('**Guardrails**');
+
+      const applyContent = await fs.readFile(applyPath, 'utf-8');
+      expect(applyContent).toContain('---');
+      expect(applyContent).toContain('description: Implement an approved OpenSpec change and keep tasks in sync.');
+      expect(applyContent).toContain('$ARGUMENTS');
+      expect(applyContent).toContain('Work through tasks sequentially');
+
+      const archiveContent = await fs.readFile(archivePath, 'utf-8');
+      expect(archiveContent).toContain('---');
+      expect(archiveContent).toContain('description: Archive a deployed OpenSpec change and update specs.');
+      expect(archiveContent).toContain('$ARGUMENTS');
+      expect(archiveContent).toContain('openspec archive <id> --yes');
+    });
+
     it('should add new tool when OpenSpec already exists', async () => {
       queueSelections('claude', DONE, 'cursor', DONE);
       await initCommand.execute(testDir);
@@ -455,6 +546,30 @@ describe('InitCommand', () => {
       );
       expect(wsChoice.configured).toBe(true);
     });
+
+    it('should mark Codex as already configured during extend mode', async () => {
+      queueSelections('codex', DONE, 'codex', DONE);
+      await initCommand.execute(testDir);
+      await initCommand.execute(testDir);
+
+      const secondRunArgs = mockPrompt.mock.calls[1][0];
+      const codexChoice = secondRunArgs.choices.find(
+        (choice: any) => choice.value === 'codex'
+      );
+      expect(codexChoice.configured).toBe(true);
+    });
+
+    it('should mark GitHub Copilot as already configured during extend mode', async () => {
+      queueSelections('github-copilot', DONE, 'github-copilot', DONE);
+      await initCommand.execute(testDir);
+      await initCommand.execute(testDir);
+
+      const secondRunArgs = mockPrompt.mock.calls[1][0];
+      const githubCopilotChoice = secondRunArgs.choices.find(
+        (choice: any) => choice.value === 'github-copilot'
+      );
+      expect(githubCopilotChoice.configured).toBe(true);
+    });
   });
 
   describe('error handling', () => {

test/core/update.test.ts

@@ -10,6 +10,7 @@ import { randomUUID } from 'crypto';
 describe('UpdateCommand', () => {
   let testDir: string;
   let updateCommand: UpdateCommand;
+  let prevCodexHome: string | undefined;
 
   beforeEach(async () => {
     // Create a temporary test directory
@@ -21,11 +22,17 @@ describe('UpdateCommand', () => {
     await fs.mkdir(openspecDir, { recursive: true });
 
     updateCommand = new UpdateCommand();
+
+    // Route Codex global directory into the test sandbox
+    prevCodexHome = process.env.CODEX_HOME;
+    process.env.CODEX_HOME = path.join(testDir, '.codex');
   });
 
   afterEach(async () => {
     // Clean up test directory
     await fs.rm(testDir, { recursive: true, force: true });
+    if (prevCodexHome === undefined) delete process.env.CODEX_HOME;
+    else process.env.CODEX_HOME = prevCodexHome;
   });
 
   it('should update only existing CLAUDE.md file', async () => {
@@ -249,6 +256,127 @@ Old body
     consoleSpy.mockRestore();
   });
 
+  it('should refresh existing Codex prompts', async () => {
+    const codexPath = path.join(
+      testDir,
+      '.codex/prompts/openspec-apply.md'
+    );
+    await fs.mkdir(path.dirname(codexPath), { recursive: true });
+    const initialContent = `---\ndescription: Old description\nargument-hint: old-hint\n---\n\n$ARGUMENTS\n<!-- OPENSPEC:START -->\nOld body\n<!-- OPENSPEC:END -->`;
+    await fs.writeFile(codexPath, initialContent);
+
+    const consoleSpy = vi.spyOn(console, 'log');
+
+    await updateCommand.execute(testDir);
+
+    const updated = await fs.readFile(codexPath, 'utf-8');
+    expect(updated).toContain('description: Implement an approved OpenSpec change and keep tasks in sync.');
+    expect(updated).toContain('argument-hint: change-id');
+    expect(updated).toContain('$ARGUMENTS');
+    expect(updated).toContain('Work through tasks sequentially');
+    expect(updated).not.toContain('Old body');
+    expect(updated).not.toContain('Old description');
+
+    const [logMessage] = consoleSpy.mock.calls[0];
+    expect(logMessage).toContain(
+      'Updated slash commands: .codex/prompts/openspec-apply.md'
+    );
+
+    consoleSpy.mockRestore();
+  });
+
+  it('should not create missing Codex prompts on update', async () => {
+    const codexApply = path.join(
+      testDir,
+      '.codex/prompts/openspec-apply.md'
+    );
+
+    // Only create apply; leave proposal and archive missing
+    await fs.mkdir(path.dirname(codexApply), { recursive: true });
+    await fs.writeFile(
+      codexApply,
+      '---\ndescription: Old\nargument-hint: old\n---\n\n$ARGUMENTS\n<!-- OPENSPEC:START -->\nOld\n<!-- OPENSPEC:END -->'
+    );
+
+    await updateCommand.execute(testDir);
+
+    const codexProposal = path.join(
+      testDir,
+      '.codex/prompts/openspec-proposal.md'
+    );
+    const codexArchive = path.join(
+      testDir,
+      '.codex/prompts/openspec-archive.md'
+    );
+
+    // Confirm they weren't created by update
+    await expect(FileSystemUtils.fileExists(codexProposal)).resolves.toBe(false);
+    await expect(FileSystemUtils.fileExists(codexArchive)).resolves.toBe(false);
+  });
+
+  it('should refresh existing GitHub Copilot prompts', async () => {
+    const ghPath = path.join(
+      testDir,
+      '.github/prompts/openspec-apply.prompt.md'
+    );
+    await fs.mkdir(path.dirname(ghPath), { recursive: true });
+    const initialContent = `---
+description: Implement an approved OpenSpec change and keep tasks in sync.
+---
+
+$ARGUMENTS
+<!-- OPENSPEC:START -->
+Old body
+<!-- OPENSPEC:END -->`;
+    await fs.writeFile(ghPath, initialContent);
+
+    const consoleSpy = vi.spyOn(console, 'log');
+
+    await updateCommand.execute(testDir);
+
+    const updated = await fs.readFile(ghPath, 'utf-8');
+    expect(updated).toContain('description: Implement an approved OpenSpec change and keep tasks in sync.');
+    expect(updated).toContain('$ARGUMENTS');
+    expect(updated).toContain('Work through tasks sequentially');
+    expect(updated).not.toContain('Old body');
+
+    const [logMessage] = consoleSpy.mock.calls[0];
+    expect(logMessage).toContain(
+      'Updated slash commands: .github/prompts/openspec-apply.prompt.md'
+    );
+
+    consoleSpy.mockRestore();
+  });
+
+  it('should not create missing GitHub Copilot prompts on update', async () => {
+    const ghApply = path.join(
+      testDir,
+      '.github/prompts/openspec-apply.prompt.md'
+    );
+
+    // Only create apply; leave proposal and archive missing
+    await fs.mkdir(path.dirname(ghApply), { recursive: true });
+    await fs.writeFile(
+      ghApply,
+      '---\ndescription: Old\n---\n\n$ARGUMENTS\n<!-- OPENSPEC:START -->\nOld\n<!-- OPENSPEC:END -->'
+    );
+
+    await updateCommand.execute(testDir);
+
+    const ghProposal = path.join(
+      testDir,
+      '.github/prompts/openspec-proposal.prompt.md'
+    );
+    const ghArchive = path.join(
+      testDir,
+      '.github/prompts/openspec-archive.prompt.md'
+    );
+
+    // Confirm they weren't created by update
+    await expect(FileSystemUtils.fileExists(ghProposal)).resolves.toBe(false);
+    await expect(FileSystemUtils.fileExists(ghArchive)).resolves.toBe(false);
+  });
+
   it('should preserve Windsurf content outside markers during update', async () => {
     const wsPath = path.join(
       testDir,