feat(agents): Add software-engineer as universal default ACT agent

[JeremyDev87]

Parent Issue

Closes part of #560

Problem

frontend-developer is currently the DEFAULT_ACT_AGENT — the fallback when no intent pattern matches. This is inappropriate for the majority of tasks:

Scenario	frontend-developer provides	Actually needed
NestJS API work	React/Vue/CSS perspective	Server logic expertise
Utility scripts	UI component patterns	Language-agnostic implementation
Refactoring	Frontend best practices	Domain-neutral code quality
Rust / Python / Go code	Nothing relevant	General programming competence

Solution

Create a new software-engineer agent designed specifically to be the universal default — domain-agnostic, language-agnostic, web-agnostic.

Why not just switch to backend-developer?

backend-developer still carries domain assumptions (APIs, servers, authentication). software-engineer is intentionally neutral:

Agent	Domain assumption
frontend-developer	Web UI, React/Vue/CSS
backend-developer	APIs, servers, databases
software-engineer	None — any language, any domain

Design Principles

software-engineer intentionally has no intent patterns.
It only activates when all other agents fail to match.
This is by design — it is the fallback of last resort.

Default behavior: analyze existing code context first, then implement without domain assumptions.

Implementation

1. Agent JSON — packages/rules/.ai-rules/agents/software-engineer.json

Key fields:

• role: General-purpose implementation engineer
• expertise: Language-agnostic coding (TypeScript, Python, Go, Rust, SQL, Shell), TDD, SOLID, Design Patterns, Refactoring, Algorithms & Data Structures
• default_behavior: Read existing code context → infer domain → implement accordingly
• no domain assumptions: Does not default to web UI, API, or any specific paradigm

2. keyword.types.ts

// Change default
export const DEFAULT_ACT_AGENT = 'software-engineer' as const;

// Add to ACT_PRIMARY_AGENTS — placed LAST to signal it's not a pattern-match target
export const ACT_PRIMARY_AGENTS = [
  'tooling-engineer',
  'platform-engineer',
  'data-engineer',
  'ai-ml-engineer',
  'mobile-developer',
  'frontend-developer',
  'backend-developer',
  'devops-engineer',
  'agent-architect',
  'software-engineer', // ← fallback default, no intent patterns
] as const;

// Add to ACT_AGENT_DISPLAY_INFO
'software-engineer': {
  name: 'Software Engineer',
  description: 'General-purpose engineer — any language, any domain, TDD-first',
},

3. act-agent.strategy.ts

Update fallback reason string:

'ACT mode default: software-engineer (no domain detected — language-agnostic generalist)'

4. act-mode.json

Update delegates_to from frontend-developer to software-engineer.

5. No changes to intent-pattern-checks.ts

software-engineer is intentionally excluded from intent patterns.

Acceptance Criteria

• software-engineer.json created with full role definition
• DEFAULT_ACT_AGENT changed to 'software-engineer'
• software-engineer added to ACT_PRIMARY_AGENTS (last position)
• software-engineer added to ACT_AGENT_DISPLAY_INFO
• act-mode.json updated — delegates_to: software-engineer
• Unit test: unrecognized prompts resolve to software-engineer (not frontend-developer)
• Unit test: software-engineer is NOT selectable via intent patterns
• All existing agent resolution tests pass (no regression)
• plan-agent.strategy.ts fallback also benefits (references DEFAULT_ACT_AGENT)

Files

• packages/rules/.ai-rules/agents/software-engineer.json (new)
• apps/mcp-server/src/keyword/keyword.types.ts
• apps/mcp-server/src/keyword/strategies/act-agent.strategy.ts
• apps/mcp-server/src/keyword/strategies/act-agent.strategy.spec.ts
• packages/rules/.ai-rules/agents/act-mode.json

Related

• Supersedes the DEFAULT_ACT_AGENT change planned in refactor(agent-selection): Update act-mode.json hardcoding + reorder intent patterns #567 (scope updated accordingly)
• Blocks refactor(agent-selection): Update act-mode.json hardcoding + reorder intent patterns #567 — refactor(agent-selection): Update act-mode.json hardcoding + reorder intent patterns #567's act-mode.json update depends on this issue completing first
• Part of feat(agent-selection): Improve ACT Mode Primary Agent Selection [Parent] #560