hippo_fact_supersede_chain
Cycle #81 (2026-05-16). Declare a multi-hop
This record as markdown: /tools/verimem/hippo-fact-supersede-chain.md
What hippo_fact_supersede_chain does on Verimem
AI agents use hippo_fact_supersede_chain to create or update resources in Verimem, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Verimem environment.
Why hippo_fact_supersede_chain is rated Medium
The tool appears to declare a supersession chain across multiple memory facts (multi-hop), which modifies existing records by marking them as superseded. This is a Write operation (reversible in a bi-temporal system where old states are preserved via time-travel), but carries high severity because misuse could corrupt a chain of established facts across the memory engine.
From the tool's definition 'Declare a multi-hop' and 'supersede chain' in the tool name — superseding facts implies overwriting/replacing existing memory entries in a chain
Attacks that exploit this kind of access
The rule that runs hippo_fact_supersede_chain safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Verimem, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For hippo_fact_supersede_chain, this is the rule to start with:
hippo_fact_supersede_chain stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Verimem, apply this rule, and every hippo_fact_supersede_chain call is checked against it from then on.
Questions about hippo_fact_supersede_chain
Cycle #81 (2026-05-16). Declare a multi-hop. It is categorised as a Write tool in the Verimem MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Verimem MCP server in PolicyLayer and add a rule for hippo_fact_supersede_chain: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Verimem. Nothing to install.
hippo_fact_supersede_chain is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the hippo_fact_supersede_chain rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for hippo_fact_supersede_chain. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
hippo_fact_supersede_chain is provided by the Verimem MCP server (aureliocpr-ctrl/verimem). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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