Code Scout

Code Scout

Purpose

Run one bounded discovery pass before the primary agent designs or edits a non-trivial code change. Keep repository-search noise out of the primary conversation by returning a small, verifiable evidence map instead of a search transcript.

Keep ownership with the primary agent. The scout identifies likely owners, couplings, tests, flows, and constraints; it does not choose the fix, edit files, or replace local verification of its result.

Apply the Eligibility Gate

Run the scout only when all of these are true:

• The task requires repository discovery.
• The work is non-trivial or crosses files, modules, layers, contracts, or tests.
• The owning files, entry points, important symbols, or closest tests are not

already sufficiently explicit.

• A fresh sub-agent can be started without inheriting the parent conversation.

Skip the scout when any of these are true:

• The task is documentation-only.
• The requested edit already names the exact file and symbol and nearby

inspection is enough.

• The change is an obvious local copy, style, or similarly bounded edit.
• The user asks only for an answer that needs no code search.
• The user forbids delegation.
• This skill already produced a verified map for the same stable task scope and

repository state.

• The repository or fresh-agent capability is unavailable.

An explicit $code-scout invocation overrides the ordinary cost/benefit heuristic, but not a user prohibition, missing capability, or safety constraint. Run exactly one scout at a time. Do not turn discovery into a review loop.

Prepare the Scout

1. Normalize the task into one implementation goal and one observable primary

signal.

1. Resolve the absolute Git repository root.
2. Identify only the repository guidance the scout needs to read, such as

AGENTS.md, a root README.md, CONTRIBUTING.md, and directly relevant architecture documents. Pass filenames and task constraints, not summaries of the expected answer.

1. Resolve scripts/repository_fingerprint.py relative to this SKILL.md.
2. Run the fingerprint script against the repository before spawning:

``bash python3 /scripts/repository_fingerprint.py ``

Preserve its head and worktree_sha256 values for the result check. The script hashes tracked changes plus non-ignored untracked file contents without printing file contents. If it cannot safely fingerprint the repository within its bounds, report that briefly and use narrow local discovery instead.

Do not pass parent reasoning, hypotheses, prior search output, expected owners, or a desired implementation. The scout must reconstruct the map from repository evidence.

Start One Fresh Terra Scout

Use the platform's fresh sub-agent mechanism with:

• model: exact gpt-5.6-terra;
• conversation inheritance: none (fork_turns: "none" when that field exists);
• one self-contained prompt;
• explicit read-only instructions and, when supported, a read-only sandbox;
• no nested delegation.

Ordinary sub-agents inherit the primary agent's sandbox and permissions. Treat the prompt constraint as required behavior, not a security boundary. When the current surface supports a custom agent configured with sandbox_mode = "read-only", prefer it without adding conversation history. The fingerprint detects stale repository state; it does not prevent temporary writes or external side effects.

Use a prompt with this content, adapted only for the current task:

You are the single read-only code scout for this task.

Repository root: 
Task: 
Primary signal: 
Repository guidance to read: 
Task and repository constraints: 
Fingerprint command:
python3 /scripts/repository_fingerprint.py 

Search the repository directly with rg/rg --files and focused reads. Read the
listed guidance before mapping code. Find the minimal evidence-backed
implementation owners, coupled contracts or consumers, closest tests, important
flow, and constraints needed by the primary agent.

Stay read-only. Do not edit, format, stage, commit, reset, stash, clean, or push.
Do not implement the task. Do not spawn or delegate to another agent, and do not
invoke code-scout recursively. Work silently.

Run the fingerprint command immediately before producing the result. Return
exactly one JSON object conforming to code-scout.v1. Return no commentary,
Markdown, code fences, prose preamble, snippets, chain of thought, or search
transcript.

If gpt-5.6-terra is unavailable, say so briefly and perform the narrowest safe local discovery. Do not silently substitute another model.

Require the code-scout.v1 Contract

Require every top-level field and no additional top-level fields:

{
  "schema_version": "code-scout.v1",
  "status": "ready",
  "repository_state": {
    "head": "40- or 64-character lowercase Git commit SHA, or unborn",
    "worktree_sha256": "64-character lowercase SHA-256"
  },
  "task_summary": "One-sentence normalized implementation goal",
  "primary_signal": "Observable behavior that should prove the task",
  "targets": [
    {
      "path": "src/repository-relative-file.ts",
      "lines": [10, 42],
      "symbols": ["owningSymbol"],
      "kind": "implementation",
      "role": "owner",
      "reason": "Concrete repository evidence for this exact target"
    }
  ],
  "flow": [
    {
      "from": "src/entry.ts:entrySymbol",
      "to": "src/owner.ts:owningSymbol",
      "relation": "dispatches"
    }
  ],
  "open_questions": []
}

Apply these invariants:

• schema_version is exactly code-scout.v1.
• status is exactly ready, not_found, or needs_clarification.
• repository_state is the scout's final fingerprint output.
• repository_state.head is unborn or a lowercase 40- or 64-character Git

object ID.

• task_summary and primary_signal are non-empty single sentences.
• targets contains no more than 16 entries.
• Each target contains exactly path, lines, symbols, kind, role, and

reason.

• kind is exactly implementation, coupled, test, or constraint.
• role is a concise lowercase role token such as owner, entrypoint,

caller, consumer, contract, validator, serializer, renderer, persistence, test, or constraint.

• path is repository-relative, exists inside the repository, contains neither

.. nor an absolute prefix, and does not point into generated output, vendored dependencies, coverage, logs, or test artifacts.

• lines is an inclusive pair of positive integers with start less than or equal

to end. Keep ranges current and tight.

• symbols is a non-empty array. Cite declared symbol names when available. For

anonymous test or describe callbacks, cite the exact test or suite title, not the generic identifier test or describe. Use "" only for a genuine file-level constraint; headings, JSON keys, and CSS selectors count as symbols.

• reason identifies concrete evidence and coupling, not speculation.
• flow contains no more than eight entries. Every entry contains exactly

from, to, and relation; endpoints use path:symbol, and relation is a concise lowercase verb such as calls, imports, dispatches, validates, serializes, renders, persists, loads, transforms, or tests.

• open_questions contains no more than five short strings.
• A ready result contains at least one implementation target and, when the

behavior is testable and tests exist, at least one test target.

• not_found and needs_clarification may use empty targets and flow.

needs_clarification includes at least one concrete question.

Keep the payload minimal. Include a file only when the primary agent needs it to understand ownership, preserve a coupled contract, verify the behavior, or obey a task-relevant repository constraint.

Validate Before Consuming

After the scout finishes:

1. Parse the final response as one JSON object. Do not inspect or request the

scout's chain of thought or search transcript.

1. Validate the schema, exact enums, limits, path safety, ranges, required owner,

and test expectation.

1. Run repository_fingerprint.py again in the primary process.
2. Accept the map only when the primary pre-scout fingerprint, the scout's

reported fingerprint, and the primary post-scout fingerprint all match.

1. Verify every reported path exists. Open only the reported ranges plus

immediately required definitions, then confirm each symbol appears in or directly adjacent to its range.

1. Use narrow import, export, caller, validator, serializer, and test searches

only as needed to verify the map.

Treat unexpected workspace changes as a shared-workspace conflict to inspect and preserve. Do not revert them, attribute them to the scout without evidence, or consume a stale map.

The primary agent owns all design, implementation, tests, and validation after the evidence map is verified. Repeat broad discovery only when a cited range is stale, the task scope materially changes, or implementation exposes a concrete missing edge.

Correct One Invalid Result

If the response is malformed, stale, unsafe, internally inconsistent, or insufficient, send the same scout one focused follow-up. List only validation defects, such as:

• invalid JSON or schema;
• missing implementation owner or discoverable test;
• unsafe or nonexistent path;
• symbol absent from the cited range;
• stale repository fingerprint;
• vague reason or excessive target surface.

Require a complete replacement code-scout.v1 object and no narrative. Do not leak a proposed answer or implementation into the correction.

Allow only one correction. After a second invalid result, timeout, tool error, or unstable worktree, report the problem briefly and continue with the narrowest safe local discovery. Do not lower the contract or substitute another model silently.

For a valid needs_clarification, first try to resolve the question from narrow repository evidence. Ask the user only when the missing decision is genuinely blocking. For a valid not_found, report the bounded result and continue locally only when useful.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: di-sukharev
• Source: di-sukharev/code-scout-skill
• License: MIT

Install and usage instructions live in the source repository linked above.