aiase-cli-first

name	aiase-cli-first
description	CLI-first architecture principle for AI-era software — why all business logic must be reachable via CLI/headless interfaces before adding UI; how Skill/MCP/A2A/CLI map to OS IPC primitives; Agentic OS concept and UI decoupling. Load when designing software architecture, choosing interface layers, discussing agent interoperability, or asking why GUI-first apps fail in agentic pipelines.

CLI-First Architecture

"CLI 才是未來 Programming 的核心溝通介面" — 莊坤達教授, AIASE 2026 W1

Core Principle

Every piece of business logic must be callable from CLI before any UI is added. UI is just one more interface on top — not the product itself. In an agentic world, the callers are agents, not humans, so the interface must be machine-composable.

Business Logic
  └── CLI / API  ← agents call here
       └── MCP wrapper  ← optional discovery layer
            └── GUI / Web  ← optional for humans

Why this order matters: if you build GUI-first, your logic is entangled in event handlers and cannot be composed by agents without re-writing it.

The OS Analogy (Agentic OS)

Every "new" agent communication pattern maps directly to OS IPC primitives:

Agentic term	OS concept	When to use
Skill / Extension	Shared-memory function call (intra-process)	Same process, deterministic — default choice
MCP tool	IPC / local socket (inter-process, same machine)	Separate process, needs isolation or reusability across agents
A2A protocol	Network service (RPC, REST)	Different organizations / cross-machine
CLI agent	Shell fork / exec	Spawning a sub-process to do a bounded task

The naming chaos is temporary — every vendor is racing to claim "Agentic OS." Underneath, it's all process communication you already know.

Why CLI-First for AI-Readable Code

1. AI agents call CLI natively. Claude Code, Codex, any agent harness can invoke command arg1 arg2 without additional glue.
2. Composability by pipes. generate | review | commit is a multi-agent pipeline without orchestration framework.
3. No coordinate-system mismatch. GUI click targets break between OS versions, resolutions, themes. CLI args are stable.
4. Headless = free. No display server, no browser, no human in the loop.

Design Checklist

Before writing any UI, verify:

• Can the core action be invoked as myapp <verb> <args>?
• Does the CLI return machine-parseable output (JSON or exit codes)?
• Is auth injectable via env var, not UI dialog?
• Can the app run with zero stdin interaction (all inputs as args/flags)?
• Is there a --dry-run or --plan flag before destructive actions?

Anti-Patterns

GUI-first trap: Building a rich dashboard before the underlying operations are CLI-accessible. Agents cannot drive this; every integration requires a browser driver or screen scraper.

MCP-first over-engineering: Wrapping everything in MCP before validating the core logic works as a plain function. Start with Skill (intra-process call), promote to MCP only when cross-process isolation is needed.

UI as the spec: Designing workflows by sketching screens. Design workflows as command sequences; screens are a rendering of those sequences.

Agentic OS Convergence

The OS is being redesigned for agent-native workloads:

• Kernel / Runtime → agent execution harness (Claude Code, Codex CLI)
• Process → any agent (LLM-backed or deterministic)
• IPC → Skill / MCP / A2A depending on boundary
• Memory → context window, with same pressure as RAM — manage it consciously
• Fork → spawn sub-agent

Future OS courses will include agentic primitives. Engineers who understand this mapping navigate tool proliferation without being confused by marketing names.

Practical Starting Point

# Every new feature starts here — not in a React component
myapp init --config ./config.json
myapp run --input data.csv --output result.json
myapp validate --schema schema.json result.json

Build the CLI. Test it. Then (optionally) wrap it in MCP so agents can discover it. Then (optionally) build a UI for humans who need one.

References

• AIASE 2026 W1 live archive: CLI as core interface (01:41–01:48)
• AIASE 2026 W8 live archive: Agentic OS concept, IPC mapping (00:51–01:12, 01:35–01:44)
• AIASE 2026 W4 live archive: autoresearch / gstack CLI-first design (01:35–02:05)

See also: [[aiase-harness]] for harness structure that enforces CLI-first, [[aiase-sdd]] for spec writing before adding interfaces, [[aiase-multi-agent]] for the full 4-layer agentic stack.