Dhpk Feasibility Study

---
name: dhpk-feasibility-study
description: "Feasibility analysis from first principles. Use when: evaluating solutions before dhpk-tech-spec, comparing approaches, risk assessment. Not for: implementation (use dhpk-adaptive-dev-workflow in feature mode), architecture advice (use dhpk-codex-architect). Output: quantitative comparison + recommendation."
metadata:
  dhpk-invocation-class: "implicit-eligible"
---

# Feasibility Study Skill

## Supplementary Agent

For each solution option, dispatch background exploration:

Agent({
  description: "Explore feasibility of solution option",
  subagent_type: "general-purpose",
  prompt: `Research the feasibility of: <solution description>
Evaluate technical feasibility, effort, risk, extensibility, and maintenance cost.`
})

## When NOT to Use

- Already have a tech spec (use `/deep-analyze`)
- Need implementation, not analysis (use `/dhpk:dhpk-codex-implement`)
- Quick question (use `/dhpk:dhpk-codebase-exploration --explain` or `/dhpk:dhpk-codex-architect`)

## Workflow

```
Decompose → Constraints → Code research → Solutions → Codex discussion → Decision → Report
```

### Phase 1: Requirement Decomposition

**Input source priority**:
1. If `canonical_docs.requirements` is non-null → consume as authoritative requirement source, validate via 5-Why
2. Otherwise → extract requirements from user input via 5-Why analysis

Use "5 Why" to uncover essence:
1. Surface requirement (what user asks for)
2. Underlying problem (why they need it)
3. Success criteria (quantifiable acceptance)

### Phase 2: Constraint Analysis

Inventory constraints by type (Technical, Business, Resource, Compatibility) with flexibility rating.

### Phase 3: Code Research

Research existing codebase:
- Related modules and reusable logic
- Existing design patterns
- Tech debt to work around

### Phase 4: Solution Exploration

Brainstorm 2-3+ solutions, each with:
1. Core idea (one sentence)
2. Implementation path
3. Quantified feasibility (see `references/analysis-phases.md`)
4. Cost and trade-offs

### Phase 5: In-Depth Codex Discussion

**⚠️ Core step — not optional (unless `--no-codex`) ⚠️**

See `references/codex-discussion-guide.md` for full rules and examples.

| Tool | Purpose | When |
|------|---------|------|
| `/dhpk:dhpk-codex-architect --mode adversarial` | Independently enumerate and critique options | At start |
| `/dhpk:dhpk-codex-architect --mode review` | Evaluate design | After proposal forms |
| `mcp__codex__codex-reply` | Ask details | Anytime |

### Phase 6: Comparative Decision

Side-by-side comparison → recommendation + backup + open questions.

## Evaluation Dimensions

| Dimension             | Green | Yellow | Red |
| --------------------- | ----- | ------ | --- |
| Technical Feasibility | Has existing patterns | Needs adaptation | Major innovation |
| Effort                | < 3 person-days | 3-10 person-days | > 10 person-days |
| Risk                  | Small scope | Some uncertainty | Many unknowns |
| Extensibility         | Easy to extend | Needs refactoring | Hard to extend |
| Maintenance Cost      | Clean, easy | Some complexity | Complex |

## Output

```markdown
## Feasibility Study: <title>
### Quantitative Comparison
| Criterion | Option A | Option B | Option C |
|-----------|----------|----------|----------|

### Recommendation
<selected option with rationale>
```

## Verification

- [ ] 5 Why decomposition completed
- [ ] Constraints inventoried with flexibility
- [ ] Existing code researched (grep/read)
- [ ] 2-3+ solutions explored with quantified assessment
- [ ] Codex discussion documented (unless `--no-codex`)
- [ ] Comparison table + recommendation + open questions

## References

- Analysis phases: `references/analysis-phases.md`
- Codex discussion: `references/codex-discussion-guide.md`
- Output template: `references/output-template.md`

## Relationship with Other Commands

```
/dhpk:dhpk-feasibility-study → /dhpk:dhpk-tech-spec → /deep-analyze → /dhpk:dhpk-codex-implement
```

## Examples

```
Input: /dhpk:dhpk-feasibility-study "Add user quota management"
Action: 5 Why → constraints → code research → 3 solutions → Codex discussion → recommendation

Input: /dhpk:dhpk-feasibility-study "Optimize cache" --context src/service/cache.ts
Action: Read cache code → constraints → solutions → Codex brainstorm → comparison → report
```