feat: add OpenCode and Codex to tool compatibility

.tool-configs/README.md

@@ -1,7 +1,7 @@
 # Tool Configuration Files
 
 These files make the scaffold work with specific AI coding tools.
-All contain the same content — a pointer to `.mex/ROUTER.md`.
+Most embed the same content — a pointer to `.mex/ROUTER.md`. OpenCode uses a JSON config that references `.mex/AGENTS.md` instead.
 
 ## Which file does your tool use?
 
@@ -11,6 +11,8 @@ All contain the same content — a pointer to `.mex/ROUTER.md`.
 | Cursor | `.cursorrules` → copy or symlink to project root |
 | Windsurf | `.windsurfrules` → copy or symlink to project root |
 | GitHub Copilot | `copilot-instructions.md` → copy to `.github/` in project root |
+| OpenCode | `opencode.json` → copy to `.opencode/` in project root |
+| Codex (OpenAI) | Copy `CLAUDE.md` as `AGENTS.md` to project root |
 | Any other tool | Point agent to `.mex/AGENTS.md` |
 
 ## Setup
@@ -29,6 +31,12 @@ cp .tool-configs/.windsurfrules ./.windsurfrules
 
 # Copilot
 mkdir -p .github && cp .tool-configs/copilot-instructions.md ./.github/copilot-instructions.md
+
+# OpenCode
+mkdir -p .opencode && cp .tool-configs/opencode.json ./.opencode/opencode.json
+
+# Codex (OpenAI)
+cp .tool-configs/CLAUDE.md ./AGENTS.md
 ```
 
 ## If your tool is not listed
@@ -38,5 +46,5 @@ or paste it at the start of each session. The scaffold works identically.
 
 ## Content
 
-All files contain identical content — the Circle 1 anchor from `.mex/AGENTS.md`.
+Most files embed the Circle 1 anchor from `.mex/AGENTS.md`. OpenCode's `opencode.json` references it by path instead.
 `.mex/AGENTS.md` is the source of truth. If you update it, update your root tool config too.

.tool-configs/opencode.json

@@ -0,0 +1,4 @@
+{
+  "$schema": "https://opencode.ai/config.json",
+  "instructions": [".mex/AGENTS.md"]
+}

README.md

@@ -243,9 +243,11 @@ your-project/
 | Claude Code | `CLAUDE.md` |
 | Cursor | `.cursorrules` |
 | Windsurf | `.windsurfrules` |
-| GitHub Copilot | `copilot-instructions.md` |
+| GitHub Copilot | `.github/copilot-instructions.md` |
+| OpenCode | `.opencode/opencode.json` |
+| Codex (OpenAI) | `AGENTS.md` |
 
-All config files contain identical content. `mex setup` asks which tool you use and copies the right one.
+Most config files embed the same instructions directly. OpenCode is the exception — `.opencode/opencode.json` references `.mex/AGENTS.md` instead of embedding content. `mex setup` asks which tool you use and creates the appropriate config.
 
 ## Contributing
 

setup.sh

@@ -226,10 +226,12 @@ echo "  1) Claude Code"
 echo "  2) Cursor"
 echo "  3) Windsurf"
 echo "  4) GitHub Copilot"
-echo "  5) Multiple (select next)"
-echo "  6) None / other (skip)"
+echo "  5) OpenCode"
+echo "  6) Codex (OpenAI)"
+echo "  7) Multiple (select next)"
+echo "  8) None / other (skip)"
 echo ""
-printf "Choice [1-6] (default: 1): "
+printf "Choice [1-8] (default: 1): "
 read -r tool_choice
 tool_choice="${tool_choice:-1}"
 
@@ -251,22 +253,29 @@ copy_tool_config() {
       [ "$DRY_RUN" -eq 0 ] && mkdir -p "$PROJECT_DIR/.github"
       safe_copy "$SCRIPT_DIR/.tool-configs/copilot-instructions.md" "$PROJECT_DIR/.github/copilot-instructions.md"
       ;;
+    5)
+      [ "$DRY_RUN" -eq 0 ] && mkdir -p "$PROJECT_DIR/.opencode"
+      safe_copy "$SCRIPT_DIR/.tool-configs/opencode.json" "$PROJECT_DIR/.opencode/opencode.json"
+      ;;
+    6)
+      safe_copy "$SCRIPT_DIR/.tool-configs/CLAUDE.md" "$PROJECT_DIR/AGENTS.md"
+      ;;
   esac
 }
 
 case "$tool_choice" in
-  1|2|3|4)
+  1|2|3|4|5|6)
     copy_tool_config "$tool_choice"
     ;;
-  5)
+  7)
     echo ""
-    printf "Enter tool numbers separated by spaces (e.g. 1 2 4): "
+    printf "Enter tool numbers separated by spaces (e.g. 1 2 5): "
     read -r multi_choices
     for choice in $multi_choices; do
       copy_tool_config "$choice"
     done
     ;;
-  6|"")
+  8|"")
     info "Skipped tool config — AGENTS.md in .mex/ works with any tool that can read files"
     ;;
   *)

src/setup/index.ts

@@ -44,6 +44,8 @@ const TOOL_CONFIGS: Record<string, { src: string; dest: string }> = {
   "2": { src: ".tool-configs/.cursorrules", dest: ".cursorrules" },
   "3": { src: ".tool-configs/.windsurfrules", dest: ".windsurfrules" },
   "4": { src: ".tool-configs/copilot-instructions.md", dest: ".github/copilot-instructions.md" },
+  "5": { src: ".tool-configs/opencode.json", dest: ".opencode/opencode.json" },
+  "6": { src: ".tool-configs/CLAUDE.md", dest: "AGENTS.md" },  // Codex reads AGENTS.md at root
 };
 
 // ── Helpers ──
@@ -309,11 +311,13 @@ async function selectToolConfig(
   console.log("  2) Cursor");
   console.log("  3) Windsurf");
   console.log("  4) GitHub Copilot");
-  console.log("  5) Multiple (select next)");
-  console.log("  6) None / skip");
+  console.log("  5) OpenCode");
+  console.log("  6) Codex (OpenAI)");
+  console.log("  7) Multiple (select next)");
+  console.log("  8) None / skip");
   console.log();
 
-  const choice = (await rl.question("Choice [1-6] (default: 1): ")).trim() || "1";
+  const choice = (await rl.question("Choice [1-8] (default: 1): ")).trim() || "1";
 
   let selectedClaude = false;
 
@@ -352,16 +356,18 @@ async function selectToolConfig(
     case "2":
     case "3":
     case "4":
+    case "5":
+    case "6":
       copyConfig(choice);
       break;
-    case "5": {
-      const multi = (await rl.question("Enter tool numbers separated by spaces (e.g. 1 2 4): ")).trim();
+    case "7": {
+      const multi = (await rl.question("Enter tool numbers separated by spaces (e.g. 1 2 5): ")).trim();
       for (const c of multi.split(/\s+/)) {
         copyConfig(c);
       }
       break;
     }
-    case "6":
+    case "8":
       info("Skipped tool config — AGENTS.md in .mex/ works with any tool that can read files");
       break;
     default:

templates/.tool-configs/README.md

@@ -0,0 +1,50 @@
+# Tool Configuration Files
+
+These files make the scaffold work with specific AI coding tools.
+Most embed the same content — a pointer to `.mex/ROUTER.md`. OpenCode uses a JSON config that references `.mex/AGENTS.md` instead.
+
+## Which file does your tool use?
+
+| Tool | File to use |
+|------|-------------|
+| Claude Code | `CLAUDE.md` → copy or symlink to project root |
+| Cursor | `.cursorrules` → copy or symlink to project root |
+| Windsurf | `.windsurfrules` → copy or symlink to project root |
+| GitHub Copilot | `copilot-instructions.md` → copy to `.github/` in project root |
+| OpenCode | `opencode.json` → copy to `.opencode/` in project root |
+| Codex (OpenAI) | Copy `CLAUDE.md` as `AGENTS.md` to project root |
+| Any other tool | Point agent to `.mex/AGENTS.md` |
+
+## Setup
+
+Copy the relevant file to the correct location in your project root:
+
+```bash
+# Claude Code
+cp .tool-configs/CLAUDE.md ./CLAUDE.md
+
+# Cursor
+cp .tool-configs/.cursorrules ./.cursorrules
+
+# Windsurf
+cp .tool-configs/.windsurfrules ./.windsurfrules
+
+# Copilot
+mkdir -p .github && cp .tool-configs/copilot-instructions.md ./.github/copilot-instructions.md
+
+# OpenCode
+mkdir -p .opencode && cp .tool-configs/opencode.json ./.opencode/opencode.json
+
+# Codex (OpenAI)
+cp .tool-configs/CLAUDE.md ./AGENTS.md
+```
+
+## If your tool is not listed
+
+Add "Read .mex/ROUTER.md before starting any task" to your tool's system prompt
+or paste it at the start of each session. The scaffold works identically.
+
+## Content
+
+Most files embed the Circle 1 anchor from `.mex/AGENTS.md`. OpenCode's `opencode.json` references it by path instead.
+`.mex/AGENTS.md` is the source of truth. If you update it, update your root tool config too.

templates/.tool-configs/opencode.json

@@ -0,0 +1,4 @@
+{
+  "$schema": "https://opencode.ai/config.json",
+  "instructions": [".mex/AGENTS.md"]
+}