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 skills/plamentsv/plamen/bit-shift-safetynpx skills add PlamenTSV/plamen --skill bit-shift-safetygit clone --depth 1 https://github.com/PlamenTSV/plamenWrote 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/skills/plamentsv/plamen/bit-shift-safety)<a href="https://agentmods.dev/skills/plamentsv/plamen/bit-shift-safety"><img src="https://agentmods.dev/badge/skills/plamentsv/plamen/bit-shift-safety.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 | $0.00035 | $0.02488 |
| Opus 5 | $0.00017 | $0.01244 |
| Sonnet 5 | $0.00007 | $0.00498 |
| Haiku 4.5 | $0.00003 | $0.00249 |
Grade A, and why
bit-shift-safety 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 — 195 lines — stays where its author put it; the contents beside it link to each section on GitHub.
BIT_SHIFT_SAFETY Skill
Trigger Pattern: Always (Aptos Move) --- Move VM aborts on shift >= bit width Inject Into: Breadth agents, depth-edge-case
The Move VM performs a runtime check on every bit shift operation: if the shift amount is greater than or equal to the bit width of the operand type, the transaction aborts. This is not a silent wraparound --- it is a hard abort that reverts the entire transaction. Any user-controllable or computed shift amount that can reach the bit width threshold is a denial-of-service vector.
1. Shift Operation Inventory
MANDATORY GREP: Search all .move files for << and >> operators.
For each shift operation found:
| Location (file:line) | Operand Type | Bit Width | Shift Amount Source | User-Controllable? | Bounded? |
|---|---|---|---|---|---|
| {file}:{line} | u8/u16/u32/u64/u128/u256 | 8/16/32/64/128/256 | constant / parameter / computed | YES/NO | YES/NO --- {how} |
Classification of shift amount sources:
- Constant: Hardcoded literal (e.g.,
1 << 64). Safe if < bit width, abort if >= bit width. Check constants that equal or exceed the bit width --- this is a compile-time-detectable bug but Move does not always catch it. - Parameter: Passed into the function from a caller. Trace the call chain to determine if externally controllable.
- Computed: Result of arithmetic (e.g.,
1 << (decimals - offset)). Requires boundary analysis.
2. Shift Amount Bound Verification
For each shift operation where the shift amount is NOT a safe constant:
2a. Bit Width Threshold Table
| Type | Bit Width | Max Safe Shift | Abort Condition |
|---|---|---|---|
| u8 | 8 | 7 | shift >= 8 |
| u16 | 16 | 15 | shift >= 16 |
| u32 | 32 | 31 | shift >= 32 |
| u64 | 64 | 63 | shift >= 64 |
| u128 | 128 | 127 | shift >= 128 |
| u256 | 256 | 255 | shift >= 256 |
2b. Bound Verification Per Shift
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 · 195 lines · 35 tokens per session scan A 875377c6b44a
bit-shift-safety is a skill published in the GitHub repository PlamenTSV/plamen (281 stars, last pushed 1mo ago), licensed MIT. It adds 35 tokens to every session and 2,488 once invoked, about $0.0002 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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