Interview Starter: Code Research Agent

A small Go HTTP service that answers questions about a sample repository by asking a model to call code-search and file-reading tools.

The included model is deterministic. It keeps the exercise reproducible and removes the need for API keys, while preserving the control flow of a tool-using agent.

The candidate is required to use an agentic coding assistant (Amp, Claude Code, Codex, Cursor, etc.) during the interview.

Setup before the interview

Clone the repository and verify that its tests pass:

git clone https://github.com/sourcegraph/interview-agent-starter.git
cd interview-agent-starter
go test ./...

Start the service:

go run . --root ./sample-repo --port 48081

In another terminal, ask a question:

curl -sS http://localhost:48081/answer \
  -H 'Content-Type: application/json' \
  -d '{"question":"Where is ErrUnauthorized defined?"}' | jq

You should receive an answer with a citation and a trace containing one search call.

You can also try a question that the starter does not yet support:

curl -sS http://localhost:48081/answer \
  -H 'Content-Type: application/json' \
  -d '{"question":"How does authentication read the bearer token?"}' | jq

Do not fix that limitation before the interview. We will extend the system together.

API

POST /answer

Request:

{"question":"Where is ErrUnauthorized defined?"}

Successful response:

{
  "answer": "ErrUnauthorized is defined in auth/errors.go. [auth/errors.go:5]",
  "steps": [
    {
      "call": {"name": "search", "query": "var ErrUnauthorized"},
      "output": "auth/errors.go:5:var ErrUnauthorized = errors.New(\"unauthorized\")\n"
    }
  ],
  "usage": {"input_tokens": 200, "output_tokens": 36, "cost_usd": 0.0002}
}

Repository layout

• agent.go contains the current agent execution flow.
• model.go defines the model boundary and deterministic demo model.
• tools.go implements code search and file reading.
• testdata/evals.json contains example questions for later evaluation work.
• sample-repo is the repository the agent researches.