Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add instructions/spuentesp/lain/copilot-instructionsgit clone --depth 1 https://github.com/spuentesp/lainWhat 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 | $0.00960 | $0.00960 |
| Opus 5 | $0.00480 | $0.00480 |
| Sonnet 5 | $0.00192 | $0.00192 |
| Haiku 4.5 | $0.00096 | $0.00096 |
Grade A, and why
lain copilot-instructions.md 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 2d 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 — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.
LAIN — Codebase Intelligence
You have access to the Lain MCP server (tool prefix mcp__lain__). Lain indexes
the current workspace and exposes tools for structural queries, semantic
search, and code navigation.
When to use lain
Reach for lain when the question is about structure, not single lines:
- "Where should I start reading this codebase?"
- "What does X depend on?" / "Who calls X?"
- "If I change X, what else breaks?"
- "Where do we do X?" (semantic search by meaning)
- "What is this function/class doing?"
- "Is there unused code?"
- "What files change together?"
- "Which test covers X?" / "What's untested?"
Skip lain for simple file reads, single-line grep, or trivial edits.
The most useful tools
| Tool | When to use it |
|---|---|
get_health |
First call in any session. Returns the resolved workspace, node counts, and status. |
find_anchors |
"Where should I start reading?" — most-called, most-stable symbols. |
list_entry_points |
Find main()s and entry points. |
explore_architecture |
High-level module/file tree. |
get_blast_radius |
"If I change X, what breaks?" — transitive callers. |
trace_dependency |
"What does X depend on?" — callees + imports. |
get_call_chain |
Specific call path between two symbols. |
semantic_search |
Find code by meaning (e.g. "rate limiting", "retry logic"). Body excerpts included. |
explain_symbol |
"What is this symbol?" — source + callers + callees + anchor. |
get_code_snippet |
Read the exact source of a symbol by id. |
find_dead_code |
Unused definitions (filters false positives). |
get_coupling_radar |
"What files change with X?" (co-change history). |
get_cross_runtime_callers |
Cross-language callers (e.g. Python → Rust FFI). |
find_test_file / find_untested_functions / get_coverage_summary |
Test discovery and coverage. |
get_file_diff / get_commit_history |
Git operations on the workspace. |
Workflows
"I'm new here, where do I start?"
get_health— confirm the workspace resolved correctly.find_anchors limit=5— top entry points.explain_symbol <top anchor>— understand it.get_blast_radius <top anchor>— see what depends on it.
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.
- 2d ago First seen · 77 lines · 960 tokens per session scan A 81466c81c20e
lain copilot-instructions.md is an instructions file published in the GitHub repository spuentesp/lain (6 stars, last pushed 3d ago), licensed MIT. It adds 960 tokens to every session, about $0.0048 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 2026-08-31.
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skillspec CLAUDE.md
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