---
name: Code Overview
slug: code-overview
category: Writing
description: Code Overview produces a progressive-disclosure summary of unfamiliar code or a pull request’s changes, explaining why it exists, what it does, and where to start. Use it to get oriented before working on or reviewing code; it writes only a scratch file and does not change the target.
github: "https://github.com/testdouble/han/tree/main/han-coding/skills/code-overview"
language: Shell
stars: 253
forks: 22
install: "npx degit https://github.com/testdouble/han/tree/main/han-coding/skills/code-overview ~/.claude/skills/code-overview"
installs_to: ~/.claude/skills/code-overview
source_path: han-coding/skills/code-overview/SKILL.md
collection_size: 25
category_size: 1060
collection_url: "https://dirskills.com/collections/testdouble/han"
added: 2026-09-02T05:20:49.981Z
last_synced: 2026-09-02T05:20:49.981Z
canonical_url: "https://dirskills.com/skills/code-overview"
---

# Code Overview

Code Overview produces a progressive-disclosure summary of unfamiliar code or a pull request’s changes, explaining why it exists, what it does, and where to start. Use it to get oriented before working on or reviewing code; it writes only a scratch file and does not change the target.

**Install:**

```bash
npx degit https://github.com/testdouble/han/tree/main/han-coding/skills/code-overview ~/.claude/skills/code-overview
```

## README

## Project Context

- git installed: !`which git 2>/dev/null || echo "not installed"`
- gh installed: !`which gh 2>/dev/null || echo "not installed"`
- CLAUDE.md: !`find . -maxdepth 1 -name "CLAUDE.md" -type f`
- project-discovery.md: !`find . -maxdepth 3 -name "project-discovery.md" -type f`
- personal config directory: !`bash "${CLAUDE_PLUGIN_ROOT}/scripts/han-config-dir.sh" 2>/dev/null || echo "$HOME/.claude"`
- project .han/config.md: !`cat .han/config.md 2>/dev/null || echo ""`

As your first action, use the Read tool on `.han/config.md` inside the `personal config directory` path above. A read
that returns no file is no personal configuration: continue silently. When that file or the `project .han/config.md`
probe supplies content, apply it per [config-rule.md](../../references/config-rule.md), which governs precedence
between the two files, relative-path resolution, and what to do with a file that reads but cannot be used.

## Operating Principles

Read these before doing anything. They constrain every step below.

- **"Why" is the organizing question.** The overview exists to answer one question first: _why does this code exist?_ —
  and the answer is the real problem it solves or the goal it accomplishes for the business or a user, never the
  technical mechanics. Why it exists, why it works the way it does, why it is the current solution to a real need: that
  is the spine of the whole document. Everything else the overview carries — what it does, how it flows, where it
  connects, where to start — flows out of the why and exists to give the reader the context to understand it. "What",
  "how", "where", and "when" are not dropped or diminished; they are framed by and subordinated to the "why" they serve.
  BECAUSE a reader who knows what code does but not why it exists cannot make sound decisions about it — the why is the
  load-bearing understanding, and the rest is scaffolding around it. State the why as a solution to a need, and never
  invent a business rationale the evidence does not support; when the why can only be inferred, mark it as inferred.
- **The skill orchestrates and synthesizes; the agents discover, validate, then refine.** The skill resolves the target,
  classifies size, dispatches exploration, and writes the overview. `han-core:codebase-explorer` agents gather the
  surrounding code and context the synthesis draws on — they do not write the overview. After the draft is written,
  `han-core:adversarial-validator` re-reads the code to challenge the draft's claims for accuracy, and
  `han-communication:readability-editor` rewrites the corrected draft against the shared readability standard,
  preserving every fact; the skill applies the validator's corrections and the editor's rewrite. The skill itself
  produces the grouping, the charts, the orientation, and the final rewrite.
- **The overview applies the shared readability standard.** As it writes and refines the overview, the skill sources the
  standard by invoking `han-communication:readability-guidance` (Step 5) and applies it, holding the default audience
  frame: a capable reader who did not do this work and lacks the author's context. The standard governs how the overview
  reads (main point first, descriptive headings, one idea per paragraph, progressive disclosure), never whether a
  required fact about the code appears. Its dedicated `han-communication:readability-editor` pass (Step 7) replaces the
  older information-architect / junior-developer readability review; the accuracy validator is a separate pass and
  stays.
- **Diagram legibility is this skill's job, not the editor's.** The readability rewrite pass is barred from touching
  diagram bodies, so nothing but this skill checks whether a chart can be read. Apply the template's diagram rule as
  you draw each chart: boxes name components and boundaries, and fields, types, and technical annotations go into the
  prose beneath. BECAUSE the exemption is right for accuracy — an editor free to reword a box could silently change
  what the chart claims about the code — and the reading load it leaves behind has to land on someone.
- **Read-only, always.** The skill explains; it never edits the target. It writes only its own scratch overview file.
  BECAUSE the job is understanding, not modification — this keeps the skill safe to point at unfamiliar code.
- **Accurate to the code, always.** Every claim the overview makes — the why it states (grounded in commit and PR/issue
  intent, comments, and what the code visibly does toward a goal), what the code does, each flow step, each named entry
  point, each change grouped by intent — must be grounded in the actual code and its intent, never inferred past the
  evidence or invented. BECAUSE a confidently wrong overview is worse than none: it sends the reader to the wrong file
  with false confidence and silently corrupts the mental model the skill exists to build. The adversarial validation
  pass (Step 7) exists to catch this. It is accuracy control on the _description_, NOT a quality judgment about the code
  — the two are different lines, and crossing into the second is still forbidden.
- **No quality judgment, ever.** The overview raises no findings, severities, or recommended changes — including in the
  PR-mode "what to watch" section, which is navigational only. BECAUSE reviewing a PR's quality is `code-review`'s job;
  this skill only helps the reader understand the PR before they review it. Crossing this line collapses the boundary
  between the two skills. Saying the code does not support a change's stated reason is not a crossing: the claim under
  test there is the document's own leading claim about the reason, which this skill already owns and already validates,
  not a judgment about the code's quality.
- **No PR statistics, ever.** The overview never states lines changed, files changed, additions/deletions, commit
  counts, or any other diff-stat figure — not in the intro, not in a section, not anywhere. BECAUSE these numbers go
  stale the instant the PR is updated and add no understanding; describe what changed and why, never how big the diff
  is.
- **Every overview cites its context.** The overview lists every source it drew on in a `Context used` section placed
  directly after the lead why section — linked directly when the source has an address (a repository file path, a PR /
  issue / commit URL), stated in one plain sentence when it does not (an uncommitted diff, the branch's commit messages,
  context supplied in conversation). BECAUSE the reader should be able to walk the same evidence the overview was built
  from, and a fabricated or broken link poisons that trust — never invent a URL or link a path that does not exist.
- **Ephemeral, not documentation.** The overview is an understand-now orientation aid, not durable documentation,
  BECAUSE durable feature and system docs are `project-documentation`'s job. That is why the skill's own default
  destination sits outside the repository, and why the skill never commits the file. This principle governs the
  skill's default only, not what a person configures: a configured output directory wins wherever it points, and the
  run says nothing about it (Step 6).
- **Default to small.** Start size classification at small and escalate only when a higher-band signal is clearly
  present. BECAUSE under-dispatching is recoverable by re-running larger; over-dispatching burns tokens and dilutes the
  overview.
- **Minimal technical detail, scoped per section.** Keep the why, flow, and context sections at the level of why the
  code exists and what it does — the why is told as a problem solved or goal met, not as technical mechanics. The
  where-to-start / what-to-watch handoff is the one exception — it must name concrete entry points or it is not
  actionable.
- **The output template lives at [references/overview-template.md](./references/overview-template.md).** Render that
  template; do not invent a structure inline.

# Produce a Code Overview

## Step 1: Resolve the Target and Select the Mode

**Bind `$size`.** If the user passed `small`, `medium`, `large`, or `dynamic` as the first positional argument, bind
`$size` to it. Anything else is part of the target, not a size; bind `$size` to the literal `none provided`.

**Note tool availability.** Read `git installed` and `gh installed` from Project Context. If `git installed` is empty or
reads `not installed`, git is unavailable — see the degraded paths below.

**Resolve the target and mode by this fixed precedence**, so an ambiguous string never silently selects the wrong mode:

1. **An explicit pull request reference or URL** (e.g. `#82`, `https://github.com/owner/repo/pull/82`) → **PR mode**
   against that pull request. Requires `gh`; if `gh installed` is empty or reads `not installed`, tell the user `gh` is
   needed to read a named pull request and offer code mode against a local target instead.
2. **An existing file or directory path** (confirm it resolves with Glob or find) → **code mode** on that path.
3. **A symbol** (a function, class, type, or other named code entity) → **code mode** on that symbol. Resolve it with
   Grep across the repository.
4. **No target string given** → **PR mode** against the current branch's changes (the local diff). This requires git,
   not a remote pull request.

**Handle the unresolvable and empty cases** (state the problem plainly and stop; never guess):

- A path or symbol that resolves to nothing, or a symbol ambiguous across several definitions → report what could not be
  resolved and ask the user to disambiguate.
- No target given and the working tree is clean with no branch changes → ask the user for a code target rather than
  producing an empty overview.
- No target given and git is unavailable → tell the user PR mode and the bare-invocation default need git to read
  changes, and ask for a named code target (code mode still runs without git).

**Resolve project context.** If `CLAUDE.md` is present, read its `## Project Discovery` section for conventions; fall
back to `project-discovery.md`. These resolve language and framework questions so the explorers infer less. If neither
exists, note that surrounding-code inference applies and pass that into the briefs.

## Step 2: Classify Size and Announce

**Classify the target's size. Default to small**; escalate only on a clear signal, and stay at the smaller band when a
signal is borderline.

- **Small** _(default)_ — a single file, a single symbol, or a small change set (a few files in one subsystem).
- **Medium** — a directory or module, or a moderate change set (several files across one or two adjacent subsystems).
- **Large** — multiple subsystems, or a large change set (many files across several subsystems).

**Apply the size override.** If `$size` is not `none provided`, use it: a band value is the band and skips the
signal-based classification, while `dynamic` forces the signal-based classification even when the project config sets
a default band. If `$size` is `none provided` and the project config supplies a band via `default-swarm-size` (per the
config rule in [../../references/config-rule.md](../../references/config-rule.md)), use that band, skip the
signal-based classification, and name the config as the source in the announcement below. A conversational override
("give me a large overview") is equivalent.

**Announce the chosen mode and size in one line before dispatching any exploration** — for example,
`Code mode, size medium: directory \`src/auth/\` spanning the session and token
subsystems.` State tool degradation in the same line when it applies (`git unavailable — code mode only`). Proceed
without a blocking confirmation; this skill is read-only and re-runnable, so a gate here would gate a reversible
operation. Honor any adjustment the user makes.

## Step 3: Gather the Input

**Code mode.** Read the target file, directory, or symbol and enough of its immediate neighbors to know its boundary —
what it imports and what imports it.

**PR mode.** Gather the change set:

- **Current branch's changes** (no target given): determine the default branch
  (`git symbolic-ref refs/remotes/origin/HEAD` or fall back to `main`/`master`), then capture
  `git diff {default-branch}...HEAD` for committed work and `git diff` plus `git diff --cached` for uncommitted work.
  Run each diff as its own Bash command so large diffs stream incrementally. Also capture
  `git log {default-branch}..HEAD --pretty=format:%B` for the change's intent. When `gh` is available, also run
  `gh pr view --json title,body,comments` (no ref — resolves the PR for the current branch) so the change's stated
  intent and any screenshots are in scope; if no PR exists for the branch, skip this without failing.
- **A named pull request** (explicit reference): run `gh pr view {ref} --json title,body,comments` for intent and
  screenshots, and `gh pr diff {ref}` for the change set. If the pull request cannot be reached (it does not exist, or
  access is unavailable), say so and offer code mode against a local target instead.

**Capture screenshots.** When a PR body or a comment contains embedded images — Markdown `![alt](url)` or
`<img src="url">`, typically GitHub-hosted (`user-attachments`, `githubusercontent.com`) — record each image's URL
together with the nearby caption or heading that says what it shows. These let the overview show a visual next to the
text that describes it, so the reader does not have to switch back to the PR. If the PR has no images, capture nothing
here.

Identify the set of files the change touches; that set scopes the exploration in Step 4.

**Start the context ledger.** From this step on, record every context source consulted — the files and directories read,
the PR reference and its URL, the commit range and log, CLAUDE.md or project-discovery.md, and any material the user
supplied in conversation — noting for each whether it has a direct address (a repository file path, a PR / issue /
commit URL) or not (an uncommitted diff, the branch's commit messages, conversational context). Step 5 renders this
ledger into the overview's `Context used` section, so an unrecorded source here is a missing citation there.

## Step 4: Dispatch Exploration Scaled to Size

Dispatch `han-core:codebase-explorer` agents to discover the surrounding code and context — **the evidence of why the
code exists** (the problem it solves or goal it serves), plus entry points, directly-related context, uses, and the main
process flow — that the synthesis draws on. **Scale the count to size, and launch every agent in a single message** so
they run concurrently:

- **Small** — one explorer over the target (or the changed files).
- **Medium** — two or three explorers, each over a coherent slice of the target (or the change), so coverage is
  parallelized rather than serialized.
- **Large** — three to five explorers, each scoped to one subsystem or one area of the change.

Each brief must contain: the resolved target (and, in PR mode, the changed-file set and the captured intent from Step
3); the project-context conventions from Step 1, or a note that surrounding-code inference applies; and the instruction
to report **the evidence of why the code exists** — the problem it solves or goal it serves, drawn from commit messages,
PR/issue intent, code comments, naming, and tests — alongside entry points, directly-related context, uses, and the main
flow, as concrete, file-grounded findings. Instruct each explorer to **list the files and sources its findings rest
on** (paths, commits, PR or issue references) so the skill can fold them into the context ledger from Step 3. Instruct
each explorer to **report what it found, not to assess quality** — this skill raises no findings — and, where the why is
not stated anywhere in the evidence, to say so rather than infer one.

When the wave returns, merge each explorer's reported sources into the context ledger, deduplicated.

Wait for the whole wave to return before synthesizing. If the target proves too large to cover fully at the chosen size,
the explorers cover the highest-signal areas; carry that into the coverage note in Step 5.

## Step 5: Synthesize the Overview

Invoke `han-communication:readability-guidance` to surface the shared readability standard into your context before you
write. Then invoke `han-communication:explanation-guidance`, which surfaces Han's standard for explaining technical work
to a reader who will not implement it: that standard governs the closing restatement this step writes and the closing
message Step 8 prints, BECAUSE both go to someone who will not open the code. Both run inline and hand control straight
back; continue with this step as soon as they return. Then draft the overview against both. Read [references/overview-template.md](./references/overview-template.md) and
render the structure for the resolved mode, drawing on the explorers' findings and the input from Step 3. The skill
writes the overview; the explorers' raw findings are not pasted in.

Open the document with a title and a short **intro paragraph naming what is being examined** — the file, directory,
symbol, pull request, or branch, and the part of the system it belongs to. Do NOT emit a `Mode:`, `Generated:`, or bare
`Target:` metadata block; that metadata does not help the reader. **Never state PR statistics** — lines changed, files
changed, additions/deletions, or commit counts — anywhere in the document; they go stale the moment the PR changes and
add no understanding. Fold anything worth keeping into the intro sentence.

**Lead with the why, and let everything else flow from it.** The first section after the intro answers _why this code
(or this change) exists_ — the real problem it solves or the goal it accomplishes for the business or a user, then why
it works the way it does and why it is the current solution to that need. Tell the why as a solution to a need, not as
technical mechanics. Then frame every section that follows as serving that why: the flow shows how the code delivers on
it, the context shows what it depends on to meet the need, the handoff shows where to start working on it. When the why
is not recoverable from the code and its intent (commit messages, PR/issue text, comments, naming, tests), state what
the code demonstrably does toward a goal and mark the inferred why as inferred — never invent a business rationale the
evidence does not support.

**Say when the code does not support the stated reason (PR mode).** You already read the code to ground the why. When
that reading shows the code already satisfies the stated motivation, or shows the change is not needed for the reason
given, say so in the why section itself, in one or two sentences, as a fact about the stated reason. Raise no finding,
assign no severity, recommend no change; the rest of the overview proceeds as normal. Three states, and only the first
gets the sentence:

1. You checked and the code contradicts the stated reason. Say so.
2. You checked and the code supports it. Say nothing extra.
3. The code says nothing either way. That is the inferred-why case above: mark the reason as inferred and claim no
   discrepancy.

NEVER report a contradiction you did not check and find, BECAUSE that is a stronger claim than the evidence carries and
the honest weaker claim already has a home in state 3. This is the highest-value sentence a change overview can carry,
and it is also the easiest one to get wrong by reaching.

**Code mode** renders, in order: the title and intro paragraph; a coverage note **only if** coverage was partial; **Why
it exists** (the problem the code solves or goal it serves, then briefly what it is and why it works the way it does —
all flowing from the why); **Context used** (the context ledger, rendered per the rules below); **Main flow** (a Mermaid
chart with a one-line scope label, read as how the code delivers on th