whycode-cli 0.5.2

Tells you what to be afraid of before you touch a file.

WhyCode

Tells you what to be afraid of before touching a file.

git blame answers "who". git log answers "what". WhyCode answers the question your senior engineer asks before any change:

"Should I be careful here?"

It mines what your repository already remembers — reverts, hotfixes, incident-tagged commits, ghost authors, tightly coupled files, long silences, verbatim warnings from past authors — and condenses them into a single Risk Card. Then it hands that card to you, your CI, or the AI that's about to edit the code.

Who is this for?

WhyCode is most valuable in moments when the wrong edit hurts. If you recognise yourself in any of these, it'll pay rent:

• Solo dev returning to a 3-month-old side project — whycode why <file> to remember why the weird bit is weird before the AI "fixes" it.
• Senior engineer joining an unfamiliar codebase — whycode scan to map the load-bearing walls; whycode why before each first edit.
• AI-paired developer — install the MCP server and your editor's assistant can read invariants and incident history before it refactors.
• Tech lead reviewing PRs — whycode diff ranks the PR's files by risk so attention goes to the scary changes first.
• CI / pre-commit gating — whycode diff --fail-on history blocks the build when high-risk files change without explanation.
• SRE doing a 3am hotfix — whycode why <file> --brief for a one-line "what should I be afraid of?" sanity check.
• Junior dev wanting to ship without breaking things — whycode scan shows where to step lightly.

What WhyCode is not for: replacing git blame, telling you what changed, or suggesting fixes. It tells you the why and the risk. You decide what to do.

Install

pip install whycode-cli

The PyPI distribution is whycode-cli (the bare name whycode was already taken by an unrelated project); the installed command is still whycode.

From source, if you want to track main:

pip install git+https://github.com/fangshuor/WhyCode.git

Requires Python 3.11+.

60-second tour

cd /path/to/your/repo

whycode tour                        # the one command to run first
whycode init                        # one-command setup: CI workflow + pre-commit gate
whycode highlights                  # repo-wide treasure map: top decisions + incidents
whycode why src/some/file.py        # the Risk Card for one file
whycode why src/some/file.py -b     # one-line summary (for triage / scripts)
whycode why src/some/file.py --at <sha>     # risk as of a past commit
whycode why src/some/file.py --mute <kind>  # local "this signal is wrong, hide it" feedback
whycode diff                        # rank everything you changed vs origin/main
whycode diff --staged               # ditto, for files staged for commit
whycode diff --fail-on history      # CI gate: exit 1 if any file is ≥ READ HISTORY FIRST
whycode show <sha>                  # classification + per-file risk for one commit
whycode timeline src/some/file.py   # risk score evolution across the file's history
whycode honest src/some/file.py     # every invariant line, verbatim, untruncated
whycode scan --top 10               # the riskiest files in the whole repo
whycode mcp -v                      # MCP server with tool-call logging

That's it. No config file, no daemon, no account, no upload.

What a Risk Card looks like

╭─  READ HISTORY FIRST  score 57/100 ──────────────────────────────╮
│ src/payment/refund.py   (24 commits)                             │
│ Latest: hotfix: idempotency token regression                     │
│         a3f4b2c1   Mei Chen   2025-09-14                         │
╰──────────────────────────────────────────────────────────────────╯
   HIGH    3 reverts touched this file
           9d2e7a1 reverts c5b81fe; bbf441c reverts 4d29ab0; …

   MED     2 incident-flagged changes in history
           2 commits matched incident keywords (latest 12 days ago:
           'hotfix: idempotency token regression').
           evidence: a3f4b2c, 7e22a04

   MED     2 invariants stated by past authors
             > Do not switch to async — v1 clients break.  (4d29ab0)
             > Important: keep the legacy header in place. (c5b81fe)

  → git show 9d2e7a1   to read the most relevant commit in full

Score interpretation:

Score	Band	What to do
75–100	HANDLE WITH CARE	Stop. Read the linked commits first.
50–74	READ HISTORY FIRST	At least skim the top signal.
25–49	WORTH A LOOK	One thing might bite you. Glance.
0–24	NO FLAGS	Quiet history — but read the diff anyway.

"But why exactly did this fire?" — --explain

When a signal looks wrong (or you just want to understand the reasoning before trusting the tool), pass --explain. Each fired signal grows a small block naming the precise rule that produced it, the literal evidence the rule looked at, and the source location of the ladder branch:

$ whycode why src/payment/refund.py --explain

   MED     1 incident-flagged change in history
           1 commit matched incident keywords (latest 12 days ago:
           'hotfix: idempotency token regression').
           evidence: a3f4b2c
           ─ rule: incident_subject_keyword  src/whycode/git_facts.py:find_incidents
             fired because: subject 'hotfix: idempotency token regression'
                            matched the literal token 'hotfix'
             evidence: hotfix

Without --explain, output is exactly as before — this is purely an opt-in transparency surface. --explain --json adds an explanation key per signal in the JSON output, with the same fields. The flag covers L1+L2 detectors only; if you also pass --llm, the L3 decision block is unaffected.

The killer use case: hand it to your AI editor

WhyCode is also an MCP server. Configure it in any MCP-aware editor or assistant, and the host LLM can pull a Risk Card before it edits any file.

{
  "mcpServers": {
    "whycode": { "command": "whycode", "args": ["mcp"] }
  }
}

Drop that snippet into your editor's MCP configuration file (location varies by editor — check your editor's MCP docs). Then in any chat:

"Refactor the refund flow."

A well-configured assistant will call get_risk_profile("src/payment/refund.py") first and read the warnings before it changes a line. Run whycode mcp -v during development to log every tool call to stderr so you can verify the integration is actually live.

Tools exposed:

• get_risk_profile(path) — full Risk Card.
• get_file_decisions(path, limit=5) — only the decision-flavoured signals (reverts, incidents, ghost keepers, invariant quotes).

Wire it into git, CI, and your editor

WhyCode is most useful when it shows up automatically in the moments you'd otherwise forget to look. The fast path:

whycode init

That installs two things:

• .git/hooks/pre-commit — runs whycode diff --staged --fail-on handle before every commit. HANDLE WITH CARE files can't be touched without an explicit git commit --no-verify.
• .github/workflows/whycode.yml — a GitHub Action that prints a risk-ranked table for every PR. Advisory by default (never blocks merging); append --fail-on history (or handle / look) to the diff line to turn it into a hard gate.

Tune the thresholds inside those two files for your repo. Re-run with whycode init --force to overwrite.

MCP server — see the next section.

Architecture (three layers, by design)

Layer	What	Network?	API key?
1	Deterministic git facts (log, diffstat, revert pairs, author activity)	no	no
2	Heuristic signals (reverts, incidents, silence, ghost keeper, coupling, invariants, churn, newborn)	no	no
3	LLM-extracted structured decisions (optional, opt-in, never on by default)	yes	yes

Layer 1 + Layer 2 produce the Risk Card by default. No model calls, no data leaving your machine. Layer 3 lifts the keyword fragments L1 + L2 extract ("do not switch to async") into structured decisions with the why drawn from the surrounding commit body — but only when you ask for it with --llm.

Optional L3 — LLM-enriched decisions

Install the optional extras and configure the env vars:

pip install 'whycode-cli[llm]'
export WHYCODE_LLM_API_KEY="…"
export WHYCODE_LLM_MODEL="<your-provider's-model-identifier>"

whycode why src/some/file.py --llm        # full card + structured decisions
whycode why src/some/file.py --llm-dry-run  # see exactly what would be sent

Privacy contract: configuration is entirely environment-driven (no hardcoded provider in the source tree); the SDK is lazy-imported (no import cost unless you opt in); only L2-filtered high-signal commits are sent (capped at 10 per call); a malformed model response degrades to "no decisions" rather than crashing.

What this is NOT

• ❌ Not a SaaS. No accounts, no cloud, no telemetry.
• ❌ Not a code review bot. WhyCode reports — never prescribes.
• ❌ Not a "what changed" tool. Plenty of those exist already.
• ❌ Not language-specific. We read git history, not your AST.
• ❌ Not a replacement for git blame. It's the briefing your senior would give you before you opened blame.

Developing

git clone https://github.com/fangshuor/WhyCode.git
cd WhyCode
pip install -e '.[dev,mcp]'
ruff check . && mypy src/whycode/ && pytest -q

See ENGINEERING.md for the engineering charter — the durable rules this repo is built under.

License

MIT. © 2026 Kevin.