coding · tool agent
Coding Agent
Make inspectable changes to a codebase and check them.
- coding
- repository
- tests
- agentic-coding
How to watch
Play starts at Input. Each station works, then a labeled packet travels the wire.
On station · 5.2s · 0/0
Packets stay on the wire. This is a conceptual simulation, not a live model run.
What Coding Agent does
A coding agent is an AI system that plans a software change, edits a repository with tools, runs tests, and reads the result. It is not an autocomplete box. It is a loop over files, commands, and verification.
The agent reads the task, inspects relevant files, plans edits, applies patches, runs tests, and stops on failure or completion. This page simulates observable workflow events, not hidden chain-of-thought.
Workflow
Each step maps to a node in the lab above. and watch the packets travel.
- 01Input
Receive the task
Load the issue and constraints.
Data preview
In
Add canonical URLs to agent pages.
- 02Plan
Inspect and plan
Find files and outline edits.
- 03Tool
Edit files
Apply patches.
- 04Tool
Run tests
Execute the relevant suite.
Failure path
Red tests send the agent back to planning. Shipping anyway is a product failure.
- 05Verify
Review the diff
Confirm the change matches the task.
- 06Output
Return the change
Diff plus test summary.
Architecture
Task, inspect, edit, test, output.
Pattern: Tool Agent
intake
Task
Change request.
agent
Plan
Edit plan.
tool
Repo
Read/write files.
tool
Tests
Test runner.
fault
Fail
Red tests.
gate
Check
Diff review.
output
Diff
Change set.
Tools
- Repository · Reads and edits files in a project workspace.
- Terminal · Runs commands and captures output in a controlled environment.
- Test Runner · Executes tests and returns pass, fail, and traces.
Inputs and outputs
Inputs
- task (string)
Implementation request.
e.g. Generate sitemap entries for every agent slug.
Outputs
- diff (patch)
Code changes.
e.g. sitemap.ts includes /agents/*.
Example run
Run example
Sitemap entries
Scenario
Add all agent canonical paths to sitemap.ts and typecheck.
Result
A small diff and a passing typecheck in a real system; here, a conceptual walkthrough.
Prompt
Educational prompt template. Not claimed to be compatible with any specific vendor runtime.
How to build
- Give repo + test tools.
- Require a plan.
- Fail the run on red tests.
- Log every patch.
Limitations
- Cannot replace human design judgment.
- Tests only catch what they cover.
- This simulation does not execute real code.
Common mistakes
- Editing without reading.
- Skipping tests.
- Huge unrelated diffs.
FAQ
What is a coding agent?
A coding agent plans a software change, edits files with tools, runs tests, and uses the results to decide whether the work is done.
How is this different from code autocomplete?
Autocomplete predicts the next tokens in a file. A coding agent is a system with tools, state, and a verification loop.
Sources
- Building effective agents · Anthropic, Dec 2024
- OpenAI Agents SDK · OpenAI, Mar 2025
- LangGraph documentation · LangChain, Jan 2024
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