engco

engco

An async English coach that lives inside Claude Code.
Critiques every prompt with an inline diff. Translates non-English prompts to natural English.

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What it does

You write prompts to Claude in English to practice. engco watches every prompt, runs a Haiku call in parallel with Claude's response, and appends a coach footer at the end of the reply.

English in:

I sended this prompt to test the new sync mode and see if its faster

Footer out (rendered after Claude's actual answer):

- I sended this prompt to test the new sync mode and see if its faster
+ I sent this prompt to test the new sync mode and see if it's faster

Changes:

• sended → sent (irregular past tense)
• its → it's (contraction)

Why: "send" is irregular (send/sent/sent); "it's" = "it is" (not the possessive).

Korean (or any other language) in → translation mode:

- 이건 sync 모드 한국어 테스트야 잘 되는지 보자
+ This is a Korean language test for sync mode—let's see if it works.

Why this design

A coach that interrupts your work fails the second time you use it. engco has to be invisible until you want it.

That means no spinner before Claude starts replying, no critique that lags one prompt behind what you just typed, and no separate panel or notification to check. The hook fires off a background worker (~1.2s API call) and tells the assistant: after answering the user, run this Bash command to fetch the result and paste it. Streaming the answer takes long enough that the worker is already done by the time the assistant calls Bash. The retrieval is instant. The coach footer appears at the end of the same response, matching the prompt that was just typed.

Install

See INSTALL.md. Two paths:

• Plugin (once published): /plugin install engco@<marketplace>
• Manual: git clone … && bash install.sh

Requires ANTHROPIC_AUTH_TOKEN or ANTHROPIC_API_KEY in env or ~/.claude/settings.json.

Slash commands

Command	Effect
/engco <text>	Manual coach on the given text. Works on any input.
/engco-on	Enable the auto coach (default state).
/engco-off	Silence the auto coach. Manual /engco still works.
/engco-show	Pull the latest auto-coach result into chat.

Plugin install namespaces these as /engco:engco, /engco:engco-on, etc.

How it works

[user prompt]
     │
     ├─→ main agent ─▶ streams answer ─▶ runs Bash retrieval ─▶ pastes diff footer
     │
     └─→ engco_suggest.py (UserPromptSubmit, ~50ms)
              │
              └─→ engco_worker.py (detached, urllib API call ~1.2s)
                       │
                       └─→ writes ~/.claude/state/engco-last.md + pending.flag

The Bash one-liner the assistant runs at the end:

for i in $(seq 1 50); do [ -f ~/.claude/state/engco-pending.flag ] && break; sleep 0.1; done
[ -f ~/.claude/state/engco-pending.flag ] && \
  cat ~/.claude/state/engco-last.md && \
  rm -f ~/.claude/state/engco-pending.flag

If the response finishes before the worker (rare), the loop polls for up to 5s. If the worker fails entirely (network error, no credentials), the footer is silently dropped. The user's main flow never breaks.

Configuration

Variable	Where	Default
ANTHROPIC_AUTH_TOKEN	env or settings.json env block	required (or ANTHROPIC_API_KEY)
ANTHROPIC_API_KEY	env or settings.json env block	required (or ANTHROPIC_AUTH_TOKEN)
ANTHROPIC_BASE_URL	env or settings.json env block	https://api.anthropic.com
MIN_WORDS	top of hooks/engco_suggest.py	6
MIN_CHARS	top of hooks/engco_suggest.py	20
MAX_PENDING_AGE_SEC	top of hooks/engco_suggest.py	600 (10 min)
MODEL	top of hooks/engco_worker.py	claude-haiku-4-5-20251001

Skip rules

The hook silently skips on:

• Empty prompt
• Prompt starting with / (slash commands)
• Prompt containing [noeng] (manual opt-out marker)
• Prompt containing triple backticks (code-heavy input; critiquing the framing adds noise)
• Prompt below both MIN_WORDS=6 words AND MIN_CHARS=20 characters
• Toggle off via /engco-off (creates ~/.claude/state/engco.off)

State files

File	Purpose
~/.claude/state/engco-last.md	Most recent worker output. Read by /engco-show.
~/.claude/state/engco-log.md	Append-only history of every critique.
~/.claude/state/engco-pending.flag	Empty marker. Set by worker, consumed by retrieval.
~/.claude/state/engco.off	Toggle marker. Created by /engco-off, removed by /engco-on.

Customization

The system prompt that drives the coach lives at the top of hooks/engco_worker.py. Two modes: