practice-sysdesign

You are running /practice-sysdesign.

Step 0 — Boot the canvas

Run bash "${CLAUDE_PLUGIN_ROOT}/scripts/ensure-canvas.sh" and parse its LAST line:

• READY → set canvas_mode = true. The script has already opened http://localhost:9999 in the user's browser.
• Starts with ERROR: → print that error line verbatim to the user, set canvas_mode = false, and CONTINUE in text mode. Never abort coaching over canvas trouble.

(The SWE_INTERVIEW_COACH_CONFIG_DIR/_PORT env vars are test-only knobs; this command's contract is the default path ~/.config/swe-interview-coach/canvas.json and port 9999.)

Step 1 — Resolve the topic

Take $ARGUMENTS:

• If ${CLAUDE_PLUGIN_ROOT}/library/sysdesign/<arg>.md exists: Read it and hold its full content as topic_source.
• Else if $ARGUMENTS is non-empty: treat it as a free-form problem statement — hold it as topic_prompt.
• If empty: Read the frontmatter id and difficulty of each file in ${CLAUDE_PLUGIN_ROOT}/library/sysdesign/*.md, present a numbered list grouped by difficulty, and wait for the user to pick → Read that entry as topic_source.

Step 2 — Parallel-session guard (canvas mode only)

Read the scene file, then: if the scene file's elements array is non-empty AND the file was modified within the last 30 minutes (find ~/.config/swe-interview-coach/canvas.json -mmin -30 prints the path), warn the user that another session may be mid-flight on this canvas, present a numbered choice, and wait for the answer:

The canvas has recent content — another session may be mid-flight. (1) proceed (resets the canvas) (2) cancel.

Step 3 — Set expectations + reset

Canvas mode — tell the user:

• Describe your architecture out loud as you think; I'll sketch it live in your tab at http://localhost:9999.
• You can also drag, rename, or add shapes yourself — I'll fold your edits in.
• Ask for hints anytime — this is practice, not a test.

Then Write {"elements":[],"appState":{"viewBackgroundColor":"#ffffff"}} to the scene file to reset it.