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Agent sandbox assurance

Network-egress control review

Define and validate where a sandbox may send network traffic

Generated code or browser actions can reach the public network. The decision is how to define and validate where a sandbox may send network traffic. The work begins with your actual workflow and looks for the evidence that separates intended behaviour from a consequential exception. It is particularly relevant to network security and runtime platform teams. A useful outcome is an explicit account of what was examined, what remains uncertain, and which decision the evidence can support.

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The runtime isolation relationship

  1. Starting evidenceDestination policies

    Establish the basis for destination rule.

  2. Decision boundaryResolution path

    Inspect DNS and proxy-mediated routing.

  3. Decision artefactEgress control map

    Retain the scoped finding and its unresolved dependencies.

Proposed working model. Untested surfaces remain outside the conclusion.

Decision

Frame the decision around destination rule

Questions and the evidence they need

Criterion / evidenceDestination rule
Inspect destination policies for the relevant constraint or observation.
Criterion / evidenceResolution path
Inspect DNS behaviour for the relevant constraint or observation.
Criterion / evidenceConnection evidence
Inspect proxy routes for the relevant constraint or observation.
Read each criterion against the available evidence before deciding that additional work is needed.

The decision is how to define and validate where a sandbox may send network traffic. This is relevant to network security and runtime platform teams when generated code or browser actions can reach the public network. Name the affected workflow, the consequence of a wrong decision, and the owner who can act on the result. The initial discussion should establish which evidence is already available and which uncertainty is material enough to investigate.

The specific failure hypothesis is that an allowlisted destination redirects or resolves to a resource outside the intended boundary. It remains a hypothesis until examined in the deployment. Existing internal tests or operating records may already resolve it; identify the uncovered question before commissioning additional work.

Mechanism

Egress policy must cover every outbound route

Relationships within runtime isolation

Source or conditionDestination rule
State which endpoints the task may reach.
Crossing or choiceResolution path
Inspect DNS and proxy-mediated routing.
Consequence or decisionConnection evidence
Compare intended deny rules with observed destinations.
Compare effective controls with harmless test observations. Each relationship needs evidence in the actual scope.

What this specialty examines

Egress review maps how a destination is selected and how connections are routed. Include name resolution, redirects, proxies and internal services where they fall within scope. A policy expressed as domain names still needs a clear account of what the runtime can reach.

The review should compare policy intent with observed outbound paths using controlled destinations and denied cases. Identify the normal route, relevant exceptions and the authoritative record of the outcome. Inspect the relevant business-system record, enforcement event or process evidence alongside any reported status. Keep incomplete cases visible, with an explanation of what their absence prevents the owner from concluding.

The tradeoff to make explicit

For this decision, tight egress reduces reachable destinations while dynamic services complicate allowlist maintenance. Compare the available design or operating choices against the same intended outcome. If one option removes a required control or changes the task boundary, describe that difference before treating its apparent simplicity, speed or lower effort as an improvement. The decision should expose the tradeoff instead of burying it in an aggregate score.

Preparation

Connect the working inputs to the boundary being examined

Evidence packet for destination rule

Illustrative working format

BasisDestination policies
Trace destination resolution and the control that permits or denies the connection.
ContextDNS behaviour
Trace destination resolution and the control that permits or denies the connection.
ObservationProxy routes
Trace destination resolution and the control that permits or denies the connection.
DependencyConnection logs
Retain the observed conditions and distinguish gaps from contrary evidence.
Illustrative preparation record. Availability, revision, and handling need confirmation.

Start with destination policies, DNS behaviour, proxy routes and connection logs. Identify the owner, revision and operating context of each source. Sanitised examples may support initial design, but differences from actual conditions should remain explicit. Where direct access is unsuitable, a customer-controlled evidence or execution route may be considered, with agreed handling and retention.

The scope also needs the runtime owner, agreed expectations for a representative boundary test, and the authority to inspect the relevant boundary. Specify what evidence would distinguish the failure in which an allowlisted destination redirects or resolves to a resource outside the intended boundary from acceptable behaviour. If stakeholders disagree about intended behaviour, resolve the interpretation before classifying the observed difference as a defect.

How the work proceeds

Carry destination rule through to an accountable finding

From the scoped material to a decision record

  1. Establish conditionsDestination policies

    Declare the permitted environment and resources.

  2. Examine the relationshipResolution path

    Apply the scoped check to connection evidence.

  3. Retain the findingEgress control map

    Record the evidence, open dependencies, and the owner’s next decision.

Proposed sequence; resolve interpretation or access gaps before relying on the next step.

Prepare the runtime boundary and fixtures

Use destination policies, DNS behaviour, proxy routes and connection logs to identify the exact runtime and boundary claimed by network security and runtime platform teams. Mark permitted resources and protected resources in a controlled fixture, including shared services where they are relevant. Define observable success, denial and incomplete setup before execution. The preparation output is a boundary map and fixture manifest that lets reviewers distinguish effective isolation from a test that never reached its target.

Exercise and inspect the boundary

Use controlled destinations and inspect connection evidence. Test allowed and denied cases without sending sensitive payloads. Confirm whether policy is enforced at the application, proxy, network or multiple layers, and document routes that bypass the expected point.

Choose containment or configuration changes

Translate the observations into an egress control map and test evidence for approved and blocked destinations. Locate each issue in the worker, shared service, policy rollout or cleanup path rather than attributing every symptom to the sandbox as a whole. Decide which configuration change, narrower resource exposure or specialist investigation is warranted. Retest the affected boundary and inspect residual state before treating the changed environment as equivalent to the intended design.

Indicative artefact

Make the egress control map usable by its owner

Egress control map

Illustrative working format

Annotated fieldEgress control map
Identify the assessed workflow, revision, and decision boundary.
Annotated fieldTest evidence for approved
Link observations and counterevidence to the case, configuration, and conclusion limit.
Annotated fieldBlocked destinations
Name the unresolved condition, next action, and accountable owner.
Illustrative artefact structure, not a completed engagement or an observed result.

A useful decision artefact is an egress control map and test evidence for approved and blocked destinations. Supporting material may include selected cases, configuration or process records, evidence references, a disagreement log and prioritised actions. Retain the case selection rationale and material disagreements alongside the result; otherwise the result may be mistaken for complete coverage.

Illustrative scenario

Examine connection evidence through a constructed exception

A constructed case and its decision paths

Illustrative scenario

  1. SituationDestination rule

    A denied destination remains reachable through an alternate proxy path.

  2. Question to examineResolution path

    Exercise controlled destinations through direct and proxy routes.

  3. Conditional next actionConnection evidence

    Address alternate outbound paths before describing the intended deny coverage.

Fictional example. No executed test, customer engagement, or measured outcome is implied.

Consider a fictional situation: a research agent needs a document source but its runtime also reaches an unrelated internal administration service. The scenario is illustrative, with no client engagement, executed test or measured improvement implied.

For the internal administration service, establish whether any workflow need justifies reachability. If not, a narrower network boundary may be appropriate. The permitted document source can remain available without assuming all internal destinations should be reachable.

Scope and next action

Keep the conclusion within the authorised runtime boundary

Confirm fit before the next commitment

Included boundaryDestination rule
This review is limited to the authorised runtime boundary.
PrerequisiteDestination policies
The relevant owner must confirm access and the intended operating conditions.
Claim limitEgress control map
Untested surfaces remain outside the conclusion.
Bring the triggering change and existing evidence; resolve the dependency that could alter the decision.

Testing is confined to explicitly authorised environments and non-destructive cases. A bounded assessment cannot establish that escape or cross-boundary access is impossible. Any engagement depends on an agreed scope, qualified team, authorised access and confirmed availability. Bring the affected workflow, its current configuration or process, the triggering change and the evidence already available. The immediate scope question is prompted by the situation in which generated code or browser actions can reach the public network; confirm which missing observation would change the owner’s next action.

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A little more clarity

Questions to consider.

Start with the questions that shape a better decision.

Is a domain allowlist enough to describe permitted egress?

Not always. Resolution, redirects, proxies and alternate routes can affect the reached destination. Describe where policy is enforced and test the actual connection path with controlled endpoints rather than inferring it solely from a domain list.

Which records explain outbound network routes?

Start with destination policies, DNS behaviour, proxy routes and connection logs. Record their revision, owner and relationship to the intended workflow. Missing context should be identified before interpreting outcomes; a sanitised fixture is useful only when its relevant differences from the operating case are understood.

How should redirects and alternate egress paths be checked?

Compare policy intent with observed outbound paths using controlled destinations and denied cases. Retain effective runtime configuration and observations from the relevant boundary. Distinguish an enforced denial from failed setup or an operation that never reached the resource. Use controlled markers and preserve residual-state evidence.

What should an egress control map contain?

The proposed output is an egress control map and test evidence for approved and blocked destinations. Include the selected conditions, supporting observations, unresolved differences and next decision. A reviewer should be able to follow each important conclusion back to its evidence and understand the limits without depending on an undocumented explanation from the author.

When is a destination allowlist too broad?

An allowlist is too broad when permitted destinations exceed the workflow's purpose or indirect routes reach unintended resources. Examine actual resolution and connections before deciding which access to retain.

What if existing evidence already answers the question?

Review its scope, provenance and configuration before proposing new work. Existing work from network security and runtime platform teams may already be sufficient. In that case, capture the decision, unresolved limitations and the change that would require another review. Additional assessment should address a real gap.

What would make the findings inconclusive?

Missing destination policies, DNS behaviour, proxy routes and connection logs can prevent a reliable interpretation, depending on the case. Record the specific missing observation and its implication. The owner can supply evidence, narrow the claim or defer the dependent decision; an incomplete case should not silently be counted as a pass.

Start with the decision you need to make.

Tell us about the agent workflow you want reviewed, and where you need greater clarity. Scope and availability are confirmed together.

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Connected disciplines

Secret-exposure testing

Check whether sandboxed work can expose credentials or other secret material. The review connects secret-injection design, redaction rules, access paths and synthetic canary values to a bounded review of execution boundaries, giving the runtime owner a clearer basis for the next action.

Resource-exhaustion testing

Establish what happens when agent execution consumes excessive resources. The review connects resource quotas, scheduler settings, workload limits and telemetry to a bounded review of execution boundaries, giving the runtime owner a clearer basis for the next action.

Malicious-code execution testing

Validate controls around potentially harmful generated code. The review connects execution policies, allowed interpreters, network limits and harmless test payloads to a bounded review of execution boundaries, giving the runtime owner a clearer basis for the next action.