🎮 The Next Input — Issue #206

The Coding Agent Cage Match

In partnership with

Wrestling Fighting GIF by DARK SIDE OF THE RING

⚡ The Briefing — 60 sec

🛠️ The Playbook — Coding Agent Benchmark Arena

Mission
Build a repeatable evaluation system that determines which coding agent performs best on your actual repositories, workflows and budget.

Difficulty
Intermediate

Build time
3–5 hours

ROI
Prevents tool-chasing, reduces coding-agent spend and gives developers evidence for choosing the right agent for each task.

0) Why This Matters

The coding-agent market is getting crowded.

Codex. Claude Code. Muse Code. Copilot. Cursor. Whatever launches next Thursday.

Every provider will demonstrate impressive benchmark results and carefully selected examples. None of those examples contain your architecture, your technical debt, your naming conventions or that one service everybody is quietly afraid to touch.

The useful question is not:

Which coding agent is best?

It is:

Which agent performs best on this kind of work, inside this repository, under our constraints?

Build the test harness once. Let the agents fight for the workload.

1) Architecture

Component

Tool

Purpose

Owner

Failure mode

Task library

GitHub Issues / JSON fixtures

Stores representative engineering tasks and acceptance criteria

Engineering Lead

Tests favour one agent

Isolated execution

Git worktrees / containers

Gives each agent an identical clean environment

Platform Engineering

Agents modify shared state

Agent layer

Codex / Claude Code / Muse Code

Plans, writes and validates code

Developers

Tool receives inconsistent context

Automated validation

GitHub Actions

Runs tests, linting, security checks and builds

DevOps

Passing checks hide poor design

Evaluation store

PostgreSQL / Airtable

Records cost, latency, output quality and human review

Operations

Results are incomplete

Reporting layer

Power BI

Compares agents by repository and task category

Leadership

One aggregate score obscures trade-offs

2) Workflow

  1. Select ten completed engineering tasks representing real work across bug fixes, features, refactors and tests.

  2. Convert each task into a clean specification with identical context and measurable acceptance criteria.

  3. Run every coding agent inside separate worktrees or containers against the same repository state.

  4. Execute automated tests, security checks and build validation without manual intervention.

  5. Have a developer review each result blindly for correctness, maintainability and unnecessary complexity.

  6. Route future tasks to the highest-performing agent by task type, cost and risk.

3) Example Prompts

Repository Task Specification

Convert the following completed engineering task into a vendor-neutral coding-agent benchmark.

Original task:
[PASTE TASK]

Repository context:
[PASTE CONTEXT]

Produce:
1. objective
2. relevant files or directories
3. constraints
4. acceptance criteria
5. required tests
6. prohibited changes
7. expected output format

Do not include implementation hints derived from the original solution.

Agent Execution Prompt

You are completing a controlled software-engineering benchmark.

Task:
[PASTE SPECIFICATION]

Requirements:
- inspect the repository before modifying files
- explain your proposed approach briefly
- make the smallest maintainable change
- preserve existing behaviour
- add or update tests
- run all available validation
- do not deploy or merge
- report files changed, tests run and unresolved concerns

Work only inside the provided environment.

Blind Review Prompt

You are reviewing an anonymised coding-agent submission.

Evaluate:
- functional correctness
- adherence to acceptance criteria
- maintainability
- architectural consistency
- security
- test quality
- unnecessary complexity
- likelihood of introducing regressions

Return:
1. blocking issues
2. non-blocking issues
3. score from 1–10 for each category
4. estimated human cleanup time
5. accept, revise or reject recommendation

4) Guardrails

  • Use identical repository snapshots and task instructions for every agent.

  • Remove provider names before human review.

  • Include simple and difficult tasks rather than only showcase examples.

  • Never allow benchmark agents to access production credentials.

  • Track retries and human intervention as part of the total cost.

  • Evaluate maintainability, not merely whether the tests pass.

  • Keep benchmark tasks private if they contain proprietary code.

  • Re-run the suite after significant model or pricing changes.

5) Pilot Rollout — 3 hours

  1. Choose three recently completed tasks with known correct solutions.

  2. Rewrite them as provider-neutral specifications with acceptance criteria.

  3. Configure isolated worktrees and the same automated checks for each agent.

  4. Run Codex, Claude Code and one alternative agent against every task.

  5. Conduct a blind developer review and record cost, speed and cleanup time.

  6. Publish a routing rule stating which agent should handle each task category.

6) Metrics

  • Acceptance-criteria pass rate

  • Automated test success rate

  • Human cleanup time

  • Cost per accepted change

  • Median task completion time

  • Security issues introduced

  • Unnecessary code added

  • Retry and intervention rate

  • Developer acceptance rate

  • Performance by task category

Pro Tip: Do not select a coding agent because it won somebody else’s benchmark. Make it earn access to your repository.

🎯 The Arsenal — Tools & Platforms

  • OpenAI Codex · handles repository-level coding, testing and implementation workflows · Link

  • Claude Code · supports terminal-based analysis and complex codebase work · Link

  • GitHub Actions · runs identical automated validation across agent submissions · Link

  • Docker · provides isolated and reproducible benchmark environments · Link

  • Power BI · compares agent quality, cost, latency and intervention requirements · Link

Copy-paste prompt block:

You are an AI coding-agent evaluation architect.

Design a benchmark system for my engineering environment.

Repositories:
[LIST]

Languages and frameworks:
[LIST]

Common engineering tasks:
[LIST]

Current coding agents:
[LIST]

Required tests and security checks:
[LIST]

Budget constraints:
[LIST]

The system must:
- use representative real-world tasks
- give every agent identical context
- isolate execution environments
- validate outputs automatically
- support blind human review
- measure total cost including retries and cleanup
- compare performance by task category
- produce routing recommendations
- remain reusable as new agents and models launch

Return:
1. benchmark architecture
2. task-selection methodology
3. evaluation rubric
4. execution workflow
5. security controls
6. reporting dashboard
7. agent-routing rules
8. pilot rollout
9. operational metrics

💡 Free Office Hours

The coding-agent market is about to become noisy, crowded and increasingly tied to each lab’s infrastructure strategy. The answer is not loyalty. It is a benchmark grounded in your own work and an architecture that lets the strongest tool win each task.

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🕹️ Game Over

The agents can fight over the code.

The frontier labs can fight over the chips.

Australia just needs to make sure it captures some of the value before the invoice arrives.

— Aaron Automating the boring. Amplifying the brilliant.

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