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Coding Agent Engineering Analysis

Deep-Dive Technical Report: Architecture, Tools & Special Considerations
Enhanced Edition · January 2026 · Version 3.0 · 13 Agents Analyzed

Deep-Dive Sections

This report is split into six focused parts for manageable reading. Each section covers a specific aspect of coding agent engineering:

Part 1

Tools & Agent Computer Interface

Tool inventories for all 13 agents, ACI design principles, edit patterns (search-replace vs diff vs whole-file), and tool success rate analysis.
Part 2

Hooks, MCP & Security

Claude Code's 8-event hook lifecycle, MCP ecosystem, OS-level sandboxing (Seatbelt/Landlock), approval workflows, and checkpoint systems.
Part 3

Memory & Context Management

Session-based vs persistent memory, Letta's memory blocks, Replit's trajectory compression, Aider's repo map, and compaction strategies.
Part 4

Agent Deep-Dives: A–L

Architecture diagrams and analysis for Aider, Claude Code, Cline, Codex CLI, Droid, Goose, and Letta Code.
Part 5

Agent Deep-Dives: O–W

Architecture diagrams and analysis for OpenCode, OpenManus, Qwen Code, Replit Agent, Vibe CLI, and Warp.
Part 6

Production & Enterprise

Context window management, error recovery patterns, prompt injection risks, enterprise deployment, and decision framework for choosing an agent.

Key Technical Findings

  1. Hook Systems Are Critical: Claude Code's 8-event hook lifecycle (UserPromptSubmit, PreToolUse, PostToolUse, Stop, SubagentStop, SessionStart, PreCompact, Notification) provides the most comprehensive extensibility model.
  2. Sandboxing Divergence: Codex CLI uses OS-native sandboxing (Seatbelt/Landlock/seccomp). Warp uses cloud sandboxes via Namespace. Most others rely on permission-based approval workflows.
  3. Memory Architecture Split: Letta Code's persistent memory blocks vs. Replit's trajectory compression vs. session-based approaches (most others). Each trades differently between continuity and context efficiency.
  4. Multi-Model Composition Wins: Warp, Droid, and Replit compose multiple LLMs (reasoning + coding models). Warp found single-agent with focused tools outperforms multi-agent approaches.
  5. LSP Integration Emerging: OpenCode's Language Server Protocol integration provides deterministic code intelligence, reducing edit hallucination.
  6. MCP as Universal Standard: MCP is now governed by the Linux Foundation's AAIF with 3,000+ servers. Every major agent supports it.
  7. Open-Source Parity: Qwen Code (67–69.6% SWE-bench) and OpenManus (53.9k GitHub stars) show open-source agents reaching near-parity with proprietary solutions.
  8. Tool Invocation Innovation: Replit Agent uses Python DSL code generation instead of JSON function calling, achieving ~90% tool invocation success rate.

Recommended Architecture

Based on analysis of all 13 agents, here is the recommended architecture for a competitive coding agent. This synthesizes the best patterns: Claude Code's hook system, Codex CLI's sandboxing, Letta's memory blocks, OpenCode's LSP integration, Warp's multi-model composition, and OpenManus's ReAct hierarchy.

RECOMMENDED CODING AGENT ARCHITECTURE ═══════════════════════════════════════════════════════════════════ ┌─────────────────────────────────────────────────────────────────┐ │ MULTI-INTERFACE LAYER │ │ ┌──────────┐ ┌──────────┐ ┌──────────┐ ┌──────────┐ │ │ │ CLI │ │ VS Code │ │ JetBrains│ │ GitHub │ │ │ │ (TUI) │ │Extension │ │ Plugin │ │ Action │ │ │ └────┬─────┘ └────┬─────┘ └────┬─────┘ └────┬─────┘ │ └───────┼─────────────┼────────────┼─────────────┼───────────────┘ └─────────────┴──────┬─────┴─────────────┘ │ gRPC / Protocol ┌────────────────────────────┼───────────────────────────────────┐ │ CORE AGENT ENGINE │ │ ┌──────────────────────────────────────────────────────────┐ │ │ │ MULTI-MODEL COMPOSITION │ │ │ │ Planning: Reasoning Model (o3/Opus) │ │ │ │ Execution: Code Model (Sonnet/GPT-5/Devstral) │ │ │ │ Fallback: Alternate provider (rate limit recovery) │ │ │ └──────────────────────────────────────────────────────────┘ │ │ │ │ ┌──────────────────────────────────────────────────────────┐ │ │ │ HOOK SYSTEM (8 events) │ │ │ │ SessionStart → UserPromptSubmit → PreToolUse → │ │ │ │ [Execute] → PostToolUse → Stop/SubagentStop │ │ │ │ PreCompact, Notification │ │ │ └──────────────────────────────────────────────────────────┘ │ │ │ │ ┌──────────────────────────────────────────────────────────┐ │ │ │ TOOL ORCHESTRATOR │ │ │ │ ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐ ┌────────┐ │ │ │ │ │ File │ │Search │ │ Exec │ │ Web │ │ Memory │ │ │ │ │ │ Ops │ │(+LSP) │ │(sand- │ │ (MCP) │ │ Blocks │ │ │ │ │ │ │ │ │ │ boxed) │ │ │ │ │ │ │ │ │ └────────┘ └────────┘ └────────┘ └────────┘ └────────┘ │ │ │ └──────────────────────────────────────────────────────────┘ │ │ │ │ ┌──────────────────────────────────────────────────────────┐ │ │ │ SUBAGENT DISPATCHER │ │ │ │ Task (parallel) │ Explore (read-only) │ Plan (design) │ │ │ └──────────────────────────────────────────────────────────┘ │ └────────────────────────────────────────────────────────────────┘ │ ┌────────────────────────────┼───────────────────────────────────┐ │ PERSISTENCE LAYER │ │ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ │ │ │Session State│ │Memory Blocks│ │Skill Library│ │ │ │(SQLite/JSONL│ │(Server-side)│ │(.md files) │ │ │ └─────────────┘ └─────────────┘ └─────────────┘ │ └────────────────────────────────────────────────────────────────┘ │ ┌────────────────────────────┼───────────────────────────────────┐ │ SECURITY LAYER │ │ ┌─────────────┐ ┌─────────────┐ ┌─────────────┐ │ │ │ OS Sandbox │ │ Approval │ │ Checkpoint │ │ │ │ (Seatbelt/ │ │ Workflow │ │ System │ │ │ │ Landlock) │ │(configurable│ │(shadow git) │ │ │ └─────────────┘ └─────────────┘ └─────────────┘ │ └────────────────────────────────────────────────────────────────┘

Implementation Priority

  1. Phase 1 — Foundation: Core tool system (file ops, search, exec), basic approval workflow, single-model execution
  2. Phase 2 — Extensibility: Hook system (8 events), MCP client, plugin architecture, multi-model composition
  3. Phase 3 — Intelligence: LSP integration, persistent memory blocks, skill learning, subagent dispatch
  4. Phase 4 — Enterprise: OS sandboxing, MDM config, OpenTelemetry audit logging, SSO, cloud sandbox infrastructure

Technology Stack Recommendations

ComponentRecommendedRationale
LanguageRust + TypeScriptRust for core/sandbox (Codex CLI pattern), TS for extensions/UI (Claude Code pattern)
TUI FrameworkRatatui (Rust) or Bubble Tea (Go)Native performance, rich terminal UI; Warp uses GPU-rendered Rust
IDE ExtensionVS Code Extension APIWidest reach; Cline and Qwen Code prove the model
IPC ProtocolgRPC with Protocol BuffersType-safe, efficient; OpenCode and Warp validate this approach
State StorageSQLite + JSONLLocal-first, portable, auditable; Codex CLI uses RolloutRecorder
Tool ExtensionsMCP (Model Context Protocol)Industry standard, 3000+ servers, Linux Foundation governance
Agent FrameworkReAct loop with stuck detectionOpenManus validates 4-level hierarchy: Base → ReAct → ToolCall → Domain
SandboxingSeatbelt (macOS) + Landlock (Linux)Codex CLI proves OS-native sandboxing is production-ready

Agent Landscape: 13 Tools Analyzed

Agent Vendor Type License Stars Key Differentiator
Aider Open Source CLI Apache-2.0 ~25k Architect/Editor dual-model, repo map via tree-sitter
Claude Code Anthropic CLI Proprietary — 8-event hook system, 18 built-in tools, subagent dispatch
Cline Community VS Code Ext Apache-2.0 ~30k Shadow git checkpoints, 33+ LLM providers, browser automation
Codex CLI OpenAI CLI (Rust) Apache-2.0 ~18k OS-native sandboxing (Seatbelt/Landlock/seccomp)
Droid Factory.ai CLI Proprietary ~504 HyperCode/ByteRank retrieval, Terminal-Bench #1
Goose Block (Square) CLI + Desktop Apache-2.0 ~10k MCP-first architecture, 3000+ extension ecosystem
Letta Code Letta CLI Apache-2.0 — Persistent memory blocks, archival vector DB, skill learning
OpenCode Community CLI (Go) MIT ~5k LSP integration, 75+ LLM providers, client-server design
OpenManus MetaGPT Framework MIT ~53.9k 4-level ReAct hierarchy, PlanningFlow orchestration
Qwen Code Alibaba CLI (TS) Apache-2.0 ~17.9k Free 2000 req/day, forked from Gemini CLI, Docker sandbox
Replit Agent Replit Web IDE Proprietary — Python DSL tool invocation, 200-min autonomy, self-testing
Vibe CLI Mistral CLI Apache-2.0 — Cheapest inference ($0.40/1M input), single-GPU deployable
Warp Warp ADE Proprietary — Full Terminal Control (interactive PTY), GPU-rendered Rust UI

Benchmark Comparison

Agent SWE-bench Verified Terminal-Bench Other Benchmarks
Warp 75.8% (GPT-5) 52% (#1) 3.2B total lines edited
Codex CLI 74.9% (GPT-5) 42.8% Code review mode
Vibe CLI 72.2% (Devstral 2) — 68.0% (Small 2, 24B)
Claude Code ~72% (Sonnet 4) 43.2% 200k context window
Qwen Code 67–69.6% 37.5% (480B) SOTA open-source agentic coding
Droid 31.67% (Lite) 58.8% (#1) Top 3 across 3 models
Replit Agent 2nd place (Lite) — 135 apps in 24h (Rokt)
OpenManus — — GAIA: 74.3%
Aider — — Architect+Editor: 85% (polyglot)
Cline — — 33+ provider support
OpenCode — — LSP-assisted editing
Goose — — 3000+ MCP extensions
Letta Code — — #1 model-agnostic on TerminalBench

⚠️ Benchmark Caveats

SWE-bench scores depend heavily on the underlying model, not just the agent harness. Factory (Droid) stopped running SWE-bench citing its Python-only, debugging-only limitations. Terminal-Bench provides a more holistic evaluation spanning coding, build/test, data/ML, systems, networking, security, and CLI workflows across 80 Dockerized tasks.

Cost & Licensing

Agent Pricing Model Free Tier Open Source
AiderFree (BYOK)✓ Unlimited✓ Apache-2.0
Claude Code$20–200/mo (API usage)✗✗ Proprietary
ClineFree (BYOK)✓ Unlimited✓ Apache-2.0
Codex CLIChatGPT plan includedWith plan✓ Apache-2.0
DroidFree–$40/mo + overage✓ (BYOK)✗ Proprietary
GooseFree (BYOK)✓ Unlimited✓ Apache-2.0
Letta CodeFree (BYOK + Letta server)✓ Unlimited✓ Apache-2.0
OpenCodeFree (BYOK)✓ Unlimited✓ MIT
OpenManusFree (BYOK)✓ Unlimited✓ MIT
Qwen CodeFree (OAuth: 2000 req/day)✓ 2000/day✓ Apache-2.0
Replit Agent$0–35/mo + creditsLimited daily✗ Proprietary
Vibe CLIFree API (promotional)✓✓ Apache-2.0
WarpFree–Pro (100–10k req/mo)✓ 100 req/mo✗ Proprietary

💡 Model Cost Comparison (per 1M tokens)

ModelInputOutputUsed By
Devstral Small 2 (24B)$0.10$0.30Vibe CLI
Devstral 2 (123B)$0.40$2.00Vibe CLI
Qwen3-Coder-480BFree (OAuth)Free (OAuth)Qwen Code
Claude Sonnet 4$3.00$15.00Claude Code, Warp, Droid
Claude Opus 4$15.00$75.00Claude Code, Droid
GPT-5~$2.50~$10.00Codex CLI, Warp, Droid

Sources & References

GitHub Repositories: Claude Code (Anthropic), Codex CLI, Qwen Code, OpenManus, Aider, Cline, Goose, OpenCode, Droid/Factory

Benchmarks: SWE-bench, Terminal-Bench, GAIA

Platforms: Warp, Replit, Factory.ai, Mistral, Letta

Document Version: 3.0 Enhanced Edition · January 2026 · Classification: Internal Engineering Document

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