feasibility-study

name	feasibility-study
description	Feasibility analysis from first principles. Use when: evaluating solutions before tech-spec, comparing approaches, risk assessment. Not for: implementation (use feature-dev), architecture advice (use codex-architect). Output: quantitative comparison + recommendation.
allowed-tools	Read, Grep, Glob, Bash(git:*), Bash(codex:*), Bash(bash:*), Write, mcp__codex__codex, mcp__codex__codex-reply, Agent

Feasibility Study Skill

Supplementary Agent

For each solution option, dispatch background exploration:

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

Trigger

• Keywords: feasibility, is this possible, can we, should we, explore options, before tech spec

When NOT to Use

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

Workflow

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

Phase 0: Resolve the feature context

The sets Phase 1 reads have to come from somewhere, and this skill is invoked directly (/feasibility-study <topic>) as often as it is invoked from another skill — so it resolves them itself rather than assuming a caller supplied them:

# The shim over the wrapper. This skill grants `Bash(bash:*)` and no node permission, and the rule
# is that a skill names the entrypoint it is permitted to run — which is also why the shared
# algorithm reference is deliberately not linked from here: it teaches the node entrypoint, and a
# file of commands this skill cannot execute has no business in its reachable graph.
bash scripts/resolve-feature.sh [--feature <key>]

The reply is one JSON document. What this skill reads out of it: scan_error first — the gate below decides whether anything else in the payload means what it says — then current_authority (what the system does today) and the design_records entries — design records carry the rationale; it is the type: requirements subset of them that states what was asked for, which is why Phase 1 filters before it selects. Each entry is { file, type, namespace, confidence, is_canonical, role }, file relative to docs_path. An empty or non-JSON reply is a failure too — node may be unavailable, which the shim cannot report as a payload. Treat it exactly as scan_error !== false below.

Phase 1: Requirement Decomposition

Input source priority:

1. If a requirements doc resolves from design_records → consume as the authoritative statement of what was asked for, validate via 5-Why. It is a design record, not a description of current behaviour: for "what does the system do today", read code, rules/ and current_authority
2. Otherwise → extract requirements from user input via 5-Why analysis

design_records is an array, so "a requirements doc" needs a rule rather than an assumption — a split or variant-backed phase contributes more than one. Filter to type: requirements first, then:

#	Candidates (design_records where type: requirements)	Result
1	none	Path 2 — extract from user input. A feature with no requirements doc is a normal state, not an exit
2	exactly one	that one
3	two or more, exactly one with is_canonical: true	that one
4	two or more, and none or several canonical	Gate: Need Human, naming the candidates

Rows 1 and 4 are different answers: "there is none" is acted on, "there are two" must not be resolved by picking. The same order /architecture applies to its tech-spec candidates.

scan_error gate. Gate on scan_error !== false, not on scan_error === true. When it is not exactly false the four source sets are unknown, not empty — the corpus could not be enumerated (unreadable directory, broken taxonomy, no repository), or the resolver never ran and a shell fallback supplied a payload with no such field at all. {} is the shape that made the stricter test useless: it has no scan_error, so === true is false and the gate passes a payload that contains nothing. Do not proceed as though the feature has no authority documents — report and take the ⚠️ Need Human exit. A key may still be present, so a non-null key is not evidence the sets are complete.

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
/codex-brainstorm	Enumerate all options	At start
/codex-architect	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

## 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

/feasibility-study → /tech-spec → /deep-analyze → /codex-implement

Examples

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

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