Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add kirilxd/swe-interview-coach/plugin install swe-interview-coachWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/commands/kirilxd/swe-interview-coach/mock-sysdesign)<a href="https://agentmods.dev/commands/kirilxd/swe-interview-coach/mock-sysdesign"><img src="https://agentmods.dev/badge/commands/kirilxd/swe-interview-coach/mock-sysdesign.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00071 | $0.01993 |
| Opus 5 | $0.00036 | $0.00996 |
| Sonnet 5 | $0.00014 | $0.00399 |
| Haiku 4.5 | $0.00007 | $0.00199 |
Grade A, and why
mock-sysdesign scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are running /mock-sysdesign.
Step 0 — Boot the canvas
Run bash "${CLAUDE_PLUGIN_ROOT}/scripts/ensure-canvas.sh" and parse its LAST line:
READY→ setcanvas_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, setcanvas_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>.mdexists: Read it and hold its full content astopic_source. - Else if
$ARGUMENTSis non-empty (a quoted or spaced free prompt): treat it as a free-form problem statement — hold it astopic_prompt. - If empty: Read the frontmatter
idanddifficultyof each file in${CLAUDE_PLUGIN_ROOT}/library/sysdesign/*.md, present a numbered list grouped by difficulty, and wait for the user to pick → Read that entry astopic_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:
- This is a timed 45-minute mock interview, scored at the end.
- YOU draw your architecture in your open tab at http://localhost:9999, exactly as you'd whiteboard it.
- The interviewer watches what you draw and probes it, but will NOT draw on your canvas during the interview.
- It will call time as the clock runs and throw ONE curveball around the 30-minute mark.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 6d ago First seen · 136 lines · 71 tokens per session scan A 9341f37bb04a
mock-sysdesign is a command published in the GitHub repository kirilxd/swe-interview-coach (80 stars, last pushed 1mo ago), licensed MIT. It adds 71 tokens to every session and 1,993 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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