OpenFGA Monotonic Read Fence and Consistency Token Propagation

--- description: OpenFGA Monotonic Read Fence and Consistency Token Propagation - Enforces strict monotonic read consistency fences on OpenFGA authorization checks following relationship tuple mutations. Prevents transient authorization bypasses, permission leakage, and stale evaluation states across distributed database read replicas by mandating write-to-read consistency token propagation or HIGHER_CONSISTENCY read policies. globs: src/**/*.ts, src/**/*.service.ts, src/**/*.guard.ts, src/**/*.middleware.ts, lib/**/*.ts alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/openfga-consistency-token-monotonic-read-fence" --- # OpenFGA Monotonic Read Fence and Consistency Token Propagation > **Severity**: CRITICAL | **Category**: security > **Anti-Pattern Warning**: Executing un-fenced authorization checks or default MINIMIZE_LATENCY reads immediately after relationship tuple mutations ## System Constraints You are a Principal Software Architect enforcing distributed authorization correctness for OpenFGA/Zanzibar ReBAC systems. Mandate strict causal consistency and monotonic read fences: all authorization checks executed within write workflows, critical privilege escalations, or permission revocations MUST explicitly bypass stale read replicas using HIGHER_CONSISTENCY or transactional fence tokens. ## Strict Guidelines - Engineers MUST ALWAYS configure `consistency: ConsistencyPreference.HIGHER_CONSISTENCY` on OpenFGA `check`, `expand`, and `listObjects` calls whenever the operation immediately follows a tuple write or revocation within the same logical workflow. - Engineers MUST NOT rely on OpenFGA's default `MINIMIZE_LATENCY` consistency mode in post-mutation validation guards or access revocation flows. - Services MUST propagate write transaction fences or consistency tokens across service boundaries via HTTP headers (e.g., `x-rebac-fence-token`) when client requests trigger dependent authorization queries. - Components NEVER assume read-after-write consistency in distributed datastores (PostgreSQL, CockroachDB, MySQL) without explicitly signaling consistency requirements to the OpenFGA query engine. - Security guards MUST fail closed with a transient 503 or retry with exponential backoff if a `HIGHER_CONSISTENCY` check fails to contact the primary database node or master replica. ## Bad vs Good Implementations ### OpenFGA Authorization Check Post-Mutation Fence #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Calling check() without an explicit consistency preference uses OpenFGA's default MINIMIZE_LATENCY, routing the query to read replicas that may still retain the deleted tuple due to replication lag. This causes false positives and transient authorization bypasses. ```typescript import { OpenFgaClient } from '@openfga/sdk'; export class AccessManager { constructor(private readonly fgaClient: OpenFgaClient) {} async revokeAndVerify(userId: string, orgId: string): Promise<boolean> { // Mutate relation (delete admin tuple) await this.fgaClient.write({ deletes: [{ user: `user:${userId}`, relation: 'admin', object: `organization:${orgId}` }], }); // VULNERABILITY: Stale read replica evaluation under default MINIMIZE_LATENCY. // Revoked user still evaluates to allowed: true due to replication lag. const { allowed } = await this.fgaClient.check({ user: `user:${userId}`, relation: 'admin', object: `organization:${orgId}`, }); return allowed; } } ``` #### Production Standard (Correct) > **Standard**: Specifying ConsistencyPreference.HIGHER_CONSISTENCY guarantees that the check request reads directly from the primary database node or blocks until replica state satisfies causal monotonic read order, preventing stale-replica authorization bypass. ```typescript import { OpenFgaClient, ConsistencyPreference } from '@openfga/sdk'; export class AccessManager { constructor(private readonly fgaClient: OpenFgaClient) {} async revokeAndVerify(userId: string, orgId: string): Promise<boolean> { // Mutate relation (delete admin tuple) await this.fgaClient.write({ deletes: [{ user: `user:${userId}`, relation: 'admin', object: `organization:${orgId}` }], }); // SECURE: Monotonic read fence forcing primary DB evaluation or causal fence const { allowed } = await this.fgaClient.check({ user: `user:${userId}`, relation: 'admin', object: `organization:${orgId}`, consistency: ConsistencyPreference.HIGHER_CONSISTENCY, }); return allowed; } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: OpenFGA Monotonic Read Fence and Consistency Token Propagation

OpenFGA Monotonic Read Fence and Consistency Token Propagation defines an industrial-grade behavioral standard for security engineering. Enforces strict monotonic read consistency fences on OpenFGA authorization checks following relationship tuple mutations. Prevents transient authorization bypasses, permission leakage, and stale evaluation states across distributed database read replicas by mandating write-to-read consistency token propagation or HIGHER_CONSISTENCY read policies. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Executing un-fenced authorization checks or default MINIMIZE_LATENCY reads immediately after relationship tuple mutations Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Executing un-fenced authorization checks or default MINIMIZE_LATENCY reads immediately after relationship tuple mutations	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Engineers MUST ALWAYS configure `consistency

Engineers MUST ALWAYS configure `consistency: ConsistencyPreference.HIGHER_CONSISTENCY` on OpenFGA `check`, `expand`, and `listObjects` calls whenever the operation immediately follows a tuple write or revocation within the same logical workflow.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.