feat(go-opencode): Add WebFetch tool for fetching web content

go-opencode/architecture.md

@@ -0,0 +1,156 @@
+# Go-OpenCode Architecture
+
+This document describes the package structure and dependencies of the Go OpenCode implementation.
+
+## Package Dependency Graph
+
+```
+                                    ┌─────────────┐
+                                    │   server    │ ◄── HTTP API Layer
+                                    └──────┬──────┘
+                                           │
+          ┌────────────────────────────────┼────────────────────────────────┐
+          │                                │                                │
+          ▼                                ▼                                ▼
+    ┌───────────┐                   ┌───────────┐                    ┌───────────┐
+    │  session  │                   │    mcp    │                    │ executor  │
+    └─────┬─────┘                   └─────┬─────┘                    └─────┬─────┘
+          │                               │                                │
+          │         ┌─────────────────────┴────────────────────────────────┤
+          │         │                                                      │
+          ▼         ▼                                                      ▼
+    ┌───────────────────┐                                          ┌───────────┐
+    │       tool        │ ◄──────────────────────────────────────  │  provider │
+    └─────────┬─────────┘                                          └───────────┘
+              │
+    ┌─────────┴─────────┬────────────────┐
+    │                   │                │
+    ▼                   ▼                ▼
+┌─────────┐       ┌───────────┐    ┌───────────┐
+│  agent  │       │  storage  │    │   event   │
+└────┬────┘       └───────────┘    └───────────┘
+     │
+     ▼
+┌────────────┐
+│ permission │
+└────────────┘
+```
+
+## Package Descriptions
+
+### Command Layer (`cmd/`)
+
+| Package | Description |
+|---------|-------------|
+| `cmd/opencode` | Main CLI application entry point. Provides `run` and `serve` commands. |
+| `cmd/calculator-mcp` | Example MCP server implementation for testing. |
+
+### Public API (`pkg/`)
+
+| Package | Description |
+|---------|-------------|
+| `pkg/types` | Shared type definitions used across the codebase (Session, Message, Part, etc.). |
+| `pkg/mcpserver` | MCP Server implementation utilities for building MCP servers. |
+
+### Internal Packages (`internal/`)
+
+#### Foundation Layer (No internal dependencies)
+
+| Package | Description |
+|---------|-------------|
+| `event` | Type-safe pub/sub event system. Enables decoupled communication between components for session events, message updates, and tool execution notifications. |
+| `logging` | Structured logging using zerolog. Provides consistent logging across all packages. |
+| `storage` | File-based JSON storage matching TypeScript implementation. Provides persistent storage for sessions, messages, and parts. |
+| `formatter` | Code formatting integration. Supports automatic code formatting via external tools. |
+| `lsp` | Language Server Protocol client. Provides code intelligence and symbol search capabilities. |
+| `sharing` | Session sharing and collaboration features. |
+| `command` | Flexible command execution system. Supports templated commands with variable substitution from configuration or markdown files. |
+
+#### Configuration Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `config` | Configuration loading, merging, and path management. Handles hierarchical loading from multiple sources (global, project, environment) with TypeScript compatibility. | `logging` |
+
+#### Permission & Safety Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `permission` | Comprehensive permission control system. Manages user consent for file editing, bash commands, web fetching, and external directory access. | `event` |
+| `agent` | Multi-agent configuration and management. Implements flexible agent system with different operation modes (primary/subagent) and tool access controls. | `permission` |
+
+#### Tool & Execution Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `tool` | Tool registry and execution framework. Manages tool registration, lookup, and execution. Includes built-in tools: Read, Write, Edit, Bash, Glob, Grep, List, WebFetch, TodoRead, TodoWrite, Task. | `agent`, `event`, `permission`, `storage` |
+| `mcp` | Model Context Protocol (MCP) client. Connects to external MCP servers and exposes their tools, resources, and prompts to the LLM. | `tool` |
+| `clienttool` | Registry for client-side tools. Enables external clients to register and execute tools via HTTP API. | `event` |
+| `executor` | Task execution implementations. Runs subagent tasks by creating child sessions and managing their lifecycle. | `agent`, `event`, `permission`, `provider`, `session`, `storage`, `tool` |
+
+#### Provider Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `provider` | LLM provider abstraction layer using Eino framework. Supports Anthropic (Claude), OpenAI (GPT), and Volcengine ARK models. Handles streaming, tool calls, and message formatting. | (none) |
+
+#### Session Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `session` | Core agentic loop and session management. Manages conversations, message processing, tool execution, and session state. Implements the main LLM interaction loop with tool calling. | `event`, `logging`, `permission`, `provider`, `storage`, `tool` |
+
+#### Integration Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `vcs` | Version control system (Git) integration. Provides repository status, diff tracking, and file change monitoring. | `event` |
+
+#### API Layer
+
+| Package | Description | Dependencies |
+|---------|-------------|--------------|
+| `server` | HTTP server implementation for OpenCode API. Provides RESTful endpoints for sessions, messages, files, config, events (SSE), MCP management, and client tools. | `clienttool`, `command`, `event`, `formatter`, `logging`, `lsp`, `mcp`, `provider`, `session`, `storage`, `tool`, `vcs` |
+
+## Dependency Statistics
+
+### Most Depended Upon (Foundation Packages)
+
+1. **event** - 6 dependents (core pub/sub infrastructure)
+2. **tool** - 5 dependents (tool execution framework)
+3. **storage** - 4 dependents (persistence layer)
+4. **provider** - 4 dependents (LLM abstraction)
+5. **permission** - 4 dependents (safety controls)
+
+### Hub Packages (High Fan-out)
+
+1. **server** - imports 12 internal packages (API orchestration)
+2. **executor** - imports 7 internal packages (subagent coordination)
+3. **session** - imports 6 internal packages (agentic loop)
+
+## Key Design Principles
+
+1. **Layered Architecture**: Foundation packages (event, storage, logging) support higher-level abstractions (session, server).
+
+2. **No Circular Dependencies**: The import cycle between `tool` and `session` was resolved by extracting `executor` as a separate package.
+
+3. **Event-Driven Communication**: Components communicate via the `event` package for loose coupling.
+
+4. **Permission-First Design**: All potentially dangerous operations (file writes, bash commands) go through the `permission` package.
+
+5. **Provider Abstraction**: LLM providers are abstracted behind a common interface, enabling easy addition of new providers.
+
+## External Dependencies
+
+Key external packages used:
+
+| Package | Purpose |
+|---------|---------|
+| `github.com/cloudwego/eino` | LLM framework for provider abstraction |
+| `github.com/go-chi/chi/v5` | HTTP router |
+| `github.com/rs/zerolog` | Structured logging |
+| `github.com/spf13/cobra` | CLI framework |
+| `github.com/mark3labs/mcp-go` | MCP protocol implementation |
+| `github.com/JohannesKaufmann/html-to-markdown` | HTML to Markdown conversion (WebFetch tool) |
+| `github.com/PuerkitoBio/goquery` | HTML parsing and text extraction (WebFetch tool) |
+| `github.com/sergi/go-diff` | Diff computation for file changes |

go-opencode/cmd/opencode/commands/run.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/opencode-ai/opencode/internal/agent"
 	"github.com/opencode-ai/opencode/internal/config"
+	"github.com/opencode-ai/opencode/internal/executor"
 	"github.com/opencode-ai/opencode/internal/mcp"
 	"github.com/opencode-ai/opencode/internal/permission"
 	"github.com/opencode-ai/opencode/internal/provider"
@@ -198,7 +199,7 @@ func runInteractive(cmd *cobra.Command, args []string) error {
 	}
 
 	// Create and configure SubagentExecutor for task tool
-	subagentExecutor := tool.NewSubagentExecutor(tool.SubagentExecutorConfig{
+	subagentExecutor := executor.NewSubagentExecutor(executor.SubagentExecutorConfig{
 		Storage:           store,
 		ProviderRegistry:  providerReg,
 		ToolRegistry:      toolReg,

go-opencode/cmd/opencode/commands/serve.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/opencode-ai/opencode/internal/agent"
 	"github.com/opencode-ai/opencode/internal/config"
+	"github.com/opencode-ai/opencode/internal/executor"
 	"github.com/opencode-ai/opencode/internal/logging"
 	"github.com/opencode-ai/opencode/internal/mcp"
 	"github.com/opencode-ai/opencode/internal/provider"
@@ -108,7 +109,7 @@ func runServe(cmd *cobra.Command, args []string) error {
 	}
 
 	// Create and configure SubagentExecutor for task tool
-	subagentExecutor := tool.NewSubagentExecutor(tool.SubagentExecutorConfig{
+	subagentExecutor := executor.NewSubagentExecutor(executor.SubagentExecutorConfig{
 		Storage:           store,
 		ProviderRegistry:  providerReg,
 		ToolRegistry:      toolReg,

go-opencode/go.mod

@@ -1,6 +1,6 @@
 module github.com/opencode-ai/opencode
 
-go 1.25
+go 1.24
 
 require (
 	// Eino LLM Framework
@@ -21,11 +21,14 @@ require (
 )
 
 require (
+	github.com/JohannesKaufmann/html-to-markdown v1.6.0
+	github.com/PuerkitoBio/goquery v1.10.0
 	github.com/ThreeDotsLabs/watermill v1.5.1
 	github.com/agnivade/levenshtein v1.2.1
 	github.com/bmatcuk/doublestar/v4 v4.9.1
 	github.com/cenkalti/backoff/v4 v4.3.0
 	github.com/cloudwego/eino-ext/components/model/ark v0.1.50
+	github.com/fsnotify/fsnotify v1.9.0
 	github.com/joho/godotenv v1.5.1
 	github.com/mark3labs/mcp-go v0.43.1
 	github.com/modelcontextprotocol/go-sdk v1.1.0
@@ -41,6 +44,7 @@ require (
 
 require (
 	github.com/Masterminds/semver/v3 v3.4.0 // indirect
+	github.com/andybalholm/cascadia v1.3.2 // indirect
 	github.com/anthropics/anthropic-sdk-go v1.19.0 // indirect
 	github.com/aws/aws-sdk-go-v2 v1.33.0 // indirect
 	github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.6.3 // indirect
@@ -67,7 +71,6 @@ require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/eino-contrib/jsonschema v1.0.2 // indirect
 	github.com/evanphx/json-patch v0.5.2 // indirect
-	github.com/fsnotify/fsnotify v1.9.0 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-task/slim-sprig/v3 v3.0.0 // indirect
 	github.com/google/go-cmp v0.7.0 // indirect
@@ -122,4 +125,4 @@ require (
 
 replace github.com/sst/opencode-sdk-go => ../packages/sdk/go
 
-replace github.com/cloudwego/eino-ext/components/model/claude => /Users/joohwi.lee/repos/cloudwego/eino-ext/components/model/claude
+// replace github.com/cloudwego/eino-ext/components/model/claude => /Users/joohwi.lee/repos/cloudwego/eino-ext/components/model/claude