codex-cost-estimate - SKILL.md Agent Skill

name: codex-cost-estimate description: Use when the user wants a realistic codebase cost estimate, Codex ROI summary, or tweet-style terminal report for a finished or near-finished software project. Inspect the repo, size the product scope, estimate human rebuild cost, and present a concise Value per Codex Hour summary with explicit assumptions.

Codex Cost Estimate

Produce a realistic, stakeholder-ready estimate for rebuilding the current repository from scratch.

Workflow

Inspect the actual repo before estimating.
Identify product scope, major subsystems, integrations, deployment targets, tests, and documentation.
Measure approximate code volume by language and by major area.
Use git history if available to estimate Codex working sessions.
Estimate senior-engineer rebuild hours.
Convert engineering cost into solo, lean-startup, growth-company, and enterprise scenarios.
Present the result in a compact terminal-style block.

What To Inspect

Top-level docs like README, context, product notes, API docs
App, API, shared packages, schema, migration, and deployment files
Test files or absence of tests
Git commit timestamps and commit count

Do not assume a specific stack or repo layout.

Estimation Rules

Prefer realistic ranges over inflated numbers.
Use current US market assumptions.
If current market rates can be verified with available tools, use current sources; otherwise use conservative rate assumptions and label them as assumptions instead of claimed research.
Treat ROI and Codex-hour estimates as heuristics, not precise accounting.
If confidence is weak, say so in the assumptions.
If no tests exist, call that out because production-ready cost is understated.
If marketing sites or prototypes are in the repo, separate them from core product code when useful.

Baseline Heuristics

Basic UI / CRUD: 30-50 LOC/hour
Standard business logic: 20-30 LOC/hour
Complex integrations / async systems: 15-25 LOC/hour
Data-heavy / domain-heavy logic: 12-22 LOC/hour
Native / systems work: 8-18 LOC/hour
Test automation: 25-40 LOC/hour

Additional effort:

Architecture / design: +15-20%
Debugging / troubleshooting: +20-30%
Refactoring / review: +10-15%
Integration / validation: +15-25%
Documentation / handoff: +5-10%
Domain learning curve: +10-20% when specialized expertise is clearly required

Company Multipliers

Efficiency assumptions:

Solo: 65%
Lean startup: 55%
Growth company: 45%
Enterprise: 35%

Team multipliers:

Solo: 1.0x
Lean startup: 1.45x
Growth company: 2.2x
Enterprise: 2.65x

Codex ROI Heuristic

Estimate Codex active hours using:

Git commit clustering within 4-hour windows
File modification clustering if git is weak
LOC fallback if history is not useful

Use this framing:

Value per Codex Hour is estimated value produced, not literal billed output.
Round to readable numbers.
Prefer understatement over hype.

Output Format

Return the final answer in a screenshot-friendly terminal-style block:

Value per Codex Hour:

| Value Basis | Total Value | Codex Hours | $/Codex Hour |
|-------------|-------------|--------------|---------------|
| Engineering only (avg) | $X | X hrs | $X/Codex hr |
| Full team (Growth Co) | $X | X hrs | $X/Codex hr |

Speed vs. Human Developer:
- Estimated human hours for same work: X hours
- Codex active hours: X hours
- Speed multiplier: Xx

Cost Comparison:
- Human developer cost: $X (at $Y/hr avg)
- Estimated Codex cost: ~$X
- Net savings: ~$X
- ROI: ~Xx

---
Grand Total Summary

| Metric | Solo | Lean Startup | Growth Co | Enterprise |
|--------|------|--------------|-----------|------------|
| Calendar Time | X | X | X | X |
| Total Human Hours | X | X | X | X |
| Total Cost | $X | $X | $X | $X |

The Headline

[One short paragraph summarizing Codex hours, engineering-equivalent value, and growth-company equivalent cost/time.]

---
Assumptions

1. [Assumption]
2. [Assumption]
3. [Assumption]

Guardrails

Do not invent frameworks, integrations, or phases not found in the repo.
Use explicit assumptions when inferring hourly rates or Codex hours.
Separate core product estimate from optional supporting surfaces when that materially changes the number.
For realism, prefer a conservative base estimate over a flashy one.