feat: implement openspec plugin core logic

Author: Octane0411

DESIGN.md

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+# OpenCode Plugin OpenSpec Design
+
+## 1. Overview
+This plugin integrates OpenSpec into OpenCode. It is **context-aware**: it activates only when it detects an OpenSpec-initialized project. When active, it dynamically registers an `openspec-plan` agent via the `config` hook, tailored for architectural planning.
+
+## 2. Activation Logic
+The plugin checks for OpenSpec presence at startup.
+
+- **Condition**: Existence of `openspec/AGENTS.md` (or `AGENTS.md`).
+- **Action**: If detected, the plugin hooks into the configuration loading process to inject the OpenSpec agent.
+
+## 3. Features (Active Mode)
+
+### 3.1. Agent Injection (`config` hook)
+Instead of just relying on runtime hooks, we will use the `config` hook to modify the OpenCode configuration directly. This is how `oh-my-opencode` replaces the default plan agent.
+
+**Implementation Strategy:**
+1.  **Hook**: `config`
+2.  **Logic**:
+    - Check if `openspec/AGENTS.md` exists.
+    - If yes, inject a new agent `openspec-plan` into the `agent` configuration object.
+    - **Agent Configuration**:
+        - `name`: "openspec-plan"
+        - `mode`: "primary"
+        - `description`: "OpenSpec Architect - Plan and specify software architecture."
+        - `prompt`: (Custom System Prompt for OpenSpec)
+        - `permission`:
+            - Explicitly `allow` editing `**/*.spec.md`, `project.md`, `AGENTS.md`.
+            - This avoids reliance on the global `permission.ask` hook for basic operations, though we can keep `permission.ask` as a fallback or for finer control.
+    - **Optional**: Hide/Demote default `plan` or `sisyphus-plan` to reduce confusion.
+
+### 3.2. Auto-Permission (Fallback)
+While the agent config handles most permissions, we can still use `permission.ask` for edge cases or to ensure a smooth experience if the static permission config isn't enough.
+
+- **Scope**: `openspec/**/*.md`, `specs/**/*.md`.
+- **Logic**: Intercept `permission.ask` and return `allow` for these patterns.
+
+## 4. Dependencies
+- `@opencode-ai/plugin`: ^1.1.1
+- `@opencode-ai/sdk`: ^1.1.1
+
+## 5. Project Structure
+```
+opencode-plugin-openspec/
+├── package.json
+├── tsconfig.json
+├── README.md
+├── DESIGN.md
+└── src/
+    ├── index.ts           # Plugin entry point
+    ├── config.ts          # Config hook implementation (Agent injection)
+    ├── prompts.ts         # System prompts
+    └── utils/
+        └── detection.ts   # Detection logic
+```
+
+## 6. Implementation Details
+
+### 6.1. Config Hook (`src/config.ts`)
+```typescript
+export const configHook: Hooks["config"] = async (config, ctx) => {
+  if (!await isOpenSpecProject(ctx)) return config;
+
+  // Define OpenSpec Plan Agent
+  const openSpecAgent = {
+    name: "openspec-plan",
+    mode: "primary",
+    description: "OpenSpec Architect",
+    prompt: OPENSPEC_SYSTEM_PROMPT,
+    permission: {
+      edit: {
+        "**/*.spec.md": "allow",
+        "**/project.md": "allow",
+        "**/AGENTS.md": "allow"
+      }
+    }
+  };
+
+  // Inject into config
+  return {
+    ...config,
+    agent: {
+      ...(config.agent || {}),
+      "openspec-plan": openSpecAgent
+    }
+  };
+};
+```
+
+### 6.2. System Prompt
+The prompt will instruct the model to:
+- Act as an Architect.
+- Read `project.md` and `AGENTS.md` for context.
+- Create/Update `specs/*.spec.md` files.
+- **NOT** write implementation code.

README.md

@@ -1,2 +1,12 @@
 # opencode-plugin-openspec
-An OpenCode plugin that integrates OpenSpec, allowing Plan Mode to create and edit spec files.
+
+An OpenCode plugin that integrates OpenSpec.
+
+## Features
+
+- **New Mode: `openspec-plan`**: A dedicated planning mode that allows creating and editing OpenSpec files (`*.spec.md`), while keeping the rest of the codebase read-only.
+- **Auto-Permission**: Automatically grants write permissions for openSpec files in `openspec-plan` mode.
+
+## Installation
+
+(Instructions to be added)

package.json

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+{
+  "name": "opencode-plugin-openspec",
+  "version": "0.1.0",
+  "main": "src/index.ts",
+  "peerDependencies": {
+    "@opencode-ai/plugin": "^1.1.1",
+    "@opencode-ai/sdk": "^1.1.1"
+  },
+  "devDependencies": {
+    "bun-types": "latest",
+    "typescript": "^5.0.0"
+  }
+}

src/config.ts

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+import type { Hooks } from "@opencode-ai/plugin";
+import { isOpenSpecProject } from "./utils/detection";
+import { OPENSPEC_SYSTEM_PROMPT } from "./prompts";
+
+export function createConfigHook(ctx: { directory: string }): Hooks["config"] {
+  return async (config) => {
+    // 1. Check if this is an OpenSpec project
+    const mockCtx = { directory: ctx.directory } as any;
+    
+    if (!await isOpenSpecProject(mockCtx)) {
+      return;
+    }
+
+    // 2. Define the OpenSpec Plan Agent
+    const openSpecAgent = {
+      name: "openspec-plan",
+      mode: "primary",
+      description: "OpenSpec Architect - Plan and specify software architecture.",
+      prompt: OPENSPEC_SYSTEM_PROMPT,
+      permission: {
+        edit: {
+          "**/*.spec.md": "allow",
+          "**/project.md": "allow",
+          "**/AGENTS.md": "allow",
+          // Allow creating new spec directories
+          "specs/**": "allow",
+          "openspec/**": "allow"
+        }
+      },
+      color: "#FF6B6B" // Distinctive color for the agent
+    };
+
+    // 3. Inject into configuration
+    // We use 'any' cast here to bypass strict type checking on the config object structure
+    // because we are dynamically extending it.
+    const agentConfig = (config.agent || {}) as any;
+    agentConfig["openspec-plan"] = openSpecAgent;
+    config.agent = agentConfig;
+  };
+}

src/index.ts

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+import type { Plugin } from "@opencode-ai/plugin";
+import { createConfigHook } from "./config";
+import { isOpenSpecProject } from "./utils/detection";
+
+const OpenSpecPlugin: Plugin = async (ctx) => {
+  const isActive = await isOpenSpecProject(ctx);
+
+  if (!isActive) {
+    return {};
+  }
+
+  return {
+    config: createConfigHook(ctx),
+  };
+};
+
+export default OpenSpecPlugin;

src/prompts.ts

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+export const OPENSPEC_SYSTEM_PROMPT = `
+<Role>
+You are the **OpenSpec Architect**.
+Your goal is to design, specify, and document software architecture using the OpenSpec standard.
+You work primarily with Markdown files in the \`openspec/\` and \`specs/\` directories.
+</Role>
+
+<Context>
+This project follows the OpenSpec standard for documentation-driven development.
+Key files:
+- \`project.md\`: High-level project vision, goals, and scope.
+- \`openspec/AGENTS.md\` (or \`AGENTS.md\`): Definitions of agents and their roles.
+- \`specs/**/*.spec.md\`: Detailed specifications for components or features.
+</Context>
+
+<Rules>
+1. **Focus on Specifications**: Your primary output should be modifications to \`*.spec.md\` files.
+2. **No Implementation**: Do NOT write implementation code (TypeScript, Python, etc.) unless explicitly requested to "implement" or "prototype". Your job is to *plan*, not to *build*.
+3. **Structure**:
+   - When designing a new feature, create a new spec file in \`specs/<feature-name>/spec.md\`.
+   - Link back to \`project.md\` to ensure alignment with high-level goals.
+4. **Format**: Follow the existing Markdown structure found in the project. Use clear headers, bullet points, and diagrams (Mermaid) where appropriate.
+</Rules>
+`.trim();

src/utils/detection.ts

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+import type { PluginInput } from "@opencode-ai/plugin";
+import { existsSync } from "node:fs";
+import { join } from "node:path";
+
+/**
+ * Checks if the current workspace is an OpenSpec project.
+ * 
+ * Detection logic:
+ * 1. Checks for `openspec/AGENTS.md` (Primary indicator)
+ * 2. Checks for `AGENTS.md` in root (Secondary indicator)
+ */
+export async function isOpenSpecProject(ctx: PluginInput): Promise<boolean> {
+  const openspecAgentsPath = join(ctx.directory, "openspec", "AGENTS.md");
+  const rootAgentsPath = join(ctx.directory, "AGENTS.md");
+
+  return existsSync(openspecAgentsPath) || existsSync(rootAgentsPath);
+}

tsconfig.json

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+{
+  "compilerOptions": {
+    "lib": ["ESNext"],
+    "module": "esnext",
+    "target": "esnext",
+    "moduleResolution": "bundler",
+    "moduleDetection": "force",
+    "allowImportingTsExtensions": true,
+    "noEmit": true,
+    "composite": true,
+    "strict": true,
+    "downlevelIteration": true,
+    "skipLibCheck": true,
+    "jsx": "react-jsx",
+    "allowSyntheticDefaultImports": true,
+    "forceConsistentCasingInFileNames": true,
+    "allowJs": true,
+    "types": [
+      "bun-types" // add Bun global
+    ]
+  }
+}