Decision

The output of policy evaluation. What the runtime enforces.

Definition

A Decision is what a policy returns. The runtime enforces it. There is no ambiguity: the Decision is the contract between policy and runtime. Start with two types. That is enough to build the first control loop:

from brane import Decision

Decision(type="allow")
Decision(type="deny", reason="Only SELECT queries are allowed")

Decision Types

Type	Status	Effect
`allow`	Implemented	Execute the capability. The function runs normally.
`deny`	Implemented	Block the capability. Raises `CapabilityDeniedError`.
`approval_required`	Planned	Pause the action until a human approves.
`redact`	Planned	Allow execution but remove fields from output before returning it.
`transform_input`	Planned	Mutate the input before executing.
`transform_output`	Planned	Mutate the output after executing.
`route`	Planned	Redirect the action to a different capability, model, or provider.
`sandbox`	Planned	Execute with constrained access.
`log_only`	Planned	Allow execution and record the action for review.

Fields

Field	Type	Description
`type`	`str`	The decision type.
`reason`	`str	None`	Human-readable reason. Included in `CapabilityDeniedError.reason`.
`decision_id`	`str`	Unique ID for this decision. Auto-generated.
`action_id`	`str	None`	The action this decision applies to.
`policy_name`	`str	None`	Name of the policy that produced this decision.
`policy_version`	`str	None`	Version of the policy that produced this decision.
`mutations`	`dict	None`	Mutation payload for transform/redact decisions. Planned.
`approval`	`dict	None`	Approval request payload. Planned.
`audit`	`dict	None`	Audit metadata to attach to the action record. Planned.
`metadata`	`dict`	Arbitrary metadata.

Computed Properties

allowed: True if type == "allow"
denied: True if type == "deny"
requires_approval: True if type == "approval_required"

Composition Rules

When multiple policies match a capability, the engine composes their decisions:

No policies match: allow by default
Any matching policy denies: return that deny decision immediately
All matching policies allow: return the last allow decision by priority order

Only allow and deny participate in composition today.

Examples

Decision(type="allow")

Decision(
    type="deny",
    reason="Refund amount exceeds tenant limit of $100",
)

Decision(
    type="deny",
    reason="High-risk tool blocked in prod",
    policy_name="block_high_risk_prod",
    policy_version="1.2",
)

When using the @runtime.before_capability decorator, policy name and version are annotated onto the Decision automatically.

Future Decision Space

The Decision type space is intentionally structured for expansion:

approval_required: pause the action, send an ApprovalRequest, resume when a human approves, or deny when they reject
redact: strip or mask sensitive fields from the output before returning it
transform_input: mutate the input before execution
transform_output: mutate the output after execution
route: redirect to a different model, tool, or capability
sandbox: execute with constrained network, filesystem, or time access
log_only: allow but record for later review

The important property is that the decision is structured. A structured decision can be audited, composed, explained, and eventually served from a central policy system.

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Core Model

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Reference

Definition

Decision Types

Fields

Computed Properties

Composition Rules

Examples

Future Decision Space

​Definition

​Decision Types

​Fields

​Computed Properties

​Composition Rules

​Examples

​Future Decision Space

Definition

Decision Types

Fields

Computed Properties

Composition Rules

Examples

Future Decision Space