OpenTelemetry Baggage Ingress Sanitization and Tenant Cardinality Fencing

Q: How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Blind Ingestion and Metric Promotion of Untrusted W3C Baggage Headers at Ingress Boundaries) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q: Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q: Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

OpenTelemetry Baggage Ingress Sanitization and Tenant Cardinality Fencing

--- description: OpenTelemetry Baggage Ingress Sanitization and Tenant Cardinality Fencing - Enforces strict boundary sanitization, key allowlisting, and cryptographic validation on inbound W3C Baggage headers at network ingress. Prevents downstream OpenTelemetry collector Denial-of-Service (DoS) and metric storage explosions caused by malicious or unbounded tenant-injected baggage context. globs: src/middleware/**/*.{ts,js}, src/telemetry/**/*.{ts,js}, src/gateway/**/*.{ts,js}, apps/ingress/**/*.{ts,js} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/opentelemetry-baggage-tenant-cardinality-fence" --- # OpenTelemetry Baggage Ingress Sanitization and Tenant Cardinality Fencing > **Severity**: CRITICAL | **Category**: devops > **Anti-Pattern Warning**: Blind Ingestion and Metric Promotion of Untrusted W3C Baggage Headers at Ingress Boundaries ## System Constraints You are a Principal Observability and Systems Reliability Architect enforcing strict tenant cardinality fences and W3C Baggage sanitization for OpenTelemetry. Ingress boundaries must treat inbound baggage as untrusted user input, stripping all unapproved keys and verifying tenant context against cryptographically validated authentication tokens before downstream propagation. ## Strict Guidelines - Engineers MUST ALWAYS strip or sanitize raw W3C baggage headers at public ingress boundaries using an explicit key allowlist. - Engineers MUST NOT propagate raw client-supplied tenant identifiers in OpenTelemetry baggage without cryptographic verification against authenticated claims (e.g., verified JWT or mTLS identity). - Code MUST strictly bound the cardinality of any baggage-derived attributes by enforcing max string lengths (<= 64 bytes) and rejecting arbitrary dynamic keys. - Services MUST NEVER automatically promote W3C Baggage entries to OpenTelemetry Metric dimensions without pre-allocated, bounded enum-value mappings. - Ingress middleware MUST truncate or drop baggage payloads that exceed configured size limits (e.g., maximum 8 entries, 512 bytes aggregate payload) to protect downstream collector buffers. ## Bad vs Good Implementations ### Ingress Baggage Sanitization with Cryptographic Tenant Verification #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Directly trusting inbound W3C baggage headers allows malicious or unauthenticated clients to inject thousands of unique keys and unbounded strings. Propagating and promoting these directly to span attributes or downstream metrics induces collector memory exhaustion and metric dimension cardinality explosion. ```typescript import { Request, Response, NextFunction } from 'express'; import { propagation, context, trace } from '@opentelemetry/api'; export function telemetryMiddleware(req: Request, res: Response, next: NextFunction) { // VULNERABLE: Directly extracts and trusts inbound W3C baggage from untrusted client const extractedContext = propagation.extract(context.active(), req.headers); context.with(extractedContext, () => { const span = trace.getActiveSpan(); // CRITICAL: Promotes all extracted baggage directly into span attributes and metrics const baggage = propagation.getBaggage(context.active()); if (baggage && span) { baggage.getAllEntries().forEach(([key, entry]) => { // High-cardinality explosion & downstream collector DoS via user-controlled keys span.setAttribute(`baggage.${key}`, entry.value); }); } next(); }); } ``` #### Production Standard (Correct) > **Standard**: Extracts context safely while dropping untrusted baggage. Derives the tenant identity solely from verified JWT/cryptographic claims, applies strict key allowlisting, limits value lengths to 64 bytes, and prevents downstream cardinality explosion. ```typescript import { Request, Response, NextFunction } from 'express'; import { propagation, context, trace, Baggage, BaggageEntry } from '@opentelemetry/api'; import { verifyTenantToken } from '../auth/verifier'; const ALLOWED_BAGGAGE_KEYS = new Set(['tenant.tier', 'feature.flag.version']); const MAX_BAGGAGE_VALUE_LEN = 64; export async function telemetryMiddleware(req: Request, res: Response, next: NextFunction): Promise<void> { // 1. Authenticate and cryptographically derive tenant identity const authToken = req.headers['authorization']?.replace(/^Bearer\s+/, ''); const verifiedClaims = authToken ? await verifyTenantToken(authToken) : null; // 2. Extract raw context but isolate baggage const rawContext = propagation.extract(context.active(), req.headers); const incomingBaggage = propagation.getBaggage(rawContext); // 3. Construct fenced baggage builder adhering to strict cardinality rules let fencedBaggage = propagation.createBaggage(); // Inject validated tenant identity exclusively from cryptographic source of truth if (verifiedClaims?.tenantId) { fencedBaggage = fencedBaggage.setEntry('tenant.id', { value: verifiedClaims.tenantId.substring(0, MAX_BAGGAGE_VALUE_LEN), }); } // 4. Filter incoming baggage against allowlist and size bounds if (incomingBaggage) { for (const [key, entry] of incomingBaggage.getAllEntries()) { if (ALLOWED_BAGGAGE_KEYS.has(key) && entry.value.length <= MAX_BAGGAGE_VALUE_LEN) { fencedBaggage = fencedBaggage.setEntry(key, { value: entry.value }); } } } // 5. Replace context baggage with the sanitized, fenced context const safeContext = propagation.setBaggage(rawContext, fencedBaggage); context.with(safeContext, () => { const span = trace.getActiveSpan(); if (span && verifiedClaims?.tenantId) { span.setAttribute('tenant.id', verifiedClaims.tenantId); } next(); }); } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: OpenTelemetry Baggage Ingress Sanitization and Tenant Cardinality Fencing

OpenTelemetry Baggage Ingress Sanitization and Tenant Cardinality Fencing defines an industrial-grade behavioral standard for devops engineering. Enforces strict boundary sanitization, key allowlisting, and cryptographic validation on inbound W3C Baggage headers at network ingress. Prevents downstream OpenTelemetry collector Denial-of-Service (DoS) and metric storage explosions caused by malicious or unbounded tenant-injected baggage context. 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: Blind Ingestion and Metric Promotion of Untrusted W3C Baggage Headers at Ingress Boundaries 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	Blind Ingestion and Metric Promotion of Untrusted W3C Baggage Headers at Ingress Boundaries	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 strip or sanitize raw W3C baggage headers at public ingress boundaries using an explicit key allowlist.

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.