One email made my inbox agent forward a card number and an SSN to a stranger. The email had hidden instructions. The agent read them as orders. A 19-line outbound guard stopped it.
That demo, tiny-poisoned-inbox, is now one of 36 tiny agents I just put on one shelf: bhjr.dev/marketplace.
One repo, one failure, one fix
Every agent is small on purpose. Each repo shows a single guardrail you can read in one sitting. Clone it, run it, watch the naive version fail, then watch the guard catch it. No framework, no signup, all free.
Sorted by how agents fail
| Category | Agents |
|---|---|
| Permissions | 11 |
| Loops & state | 8 |
| Evals | 5 |
| Secrets & egress | 4 |
| Injection | 3 |
| Budgets | 3 |
| Schemas | 2 |
Each agent page has the guardrail in one sentence, the run command and a copy button for the clone. You can search and filter by category.
Where I'd start
- Poisoned Inbox: one poisoned email, one leak, a 19-line guard that blocks card numbers and SSNs before anything is sent. It's plain pattern matching, not Anthropic's classifier.
- Credential Gateway: the sandbox only holds a short-lived token. The gateway strips any auth header the agent set and injects the real credential from outside. Nothing worth stealing inside.
- Harness Decision Boundary: the model proposes, the harness decides, the log remembers. 16 tests.
- Schema Gate and Agent Evals if your agent already works and you want to prove it keeps working.
Why a shelf of tiny agents
"Make the agent safe" means nothing until you can point at the line of code that says no. These are 36 of those lines.
The system behind them
The tiny agents show one pattern each. Ship a Safe Agent shows how they fit together in one harness, starting with who decides: the model or your code.
Module 1 is free. The founding price is $149 until Nov 8, then $199. Get the course.
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