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backendcritical PriorityID: temporal-workflow-determinism-patching-invariant

Temporal Workflow Determinism & Dynamic Patch Invariant Guardrail

Temporal workflows must maintain absolute event-history replay determinism across deployments. Any modification to existing workflow definitions—including reordering activities, mutating control-flow branches, or removing timers—must use deterministic versioning primitives (patched/deprecatePatch) to prevent non-deterministic execution exceptions and workflow corruption during rolling deployments.

Prohibited Anti-Pattern: Mutating Workflow Control Flow or Schedule Commands Without Version Patching

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---
description: Temporal Workflow Determinism & Dynamic Patch Invariant Guardrail - Temporal workflows must maintain absolute event-history replay determinism across deployments. Any modification to existing workflow definitions—including reordering activities, mutating control-flow branches, or removing timers—must use deterministic versioning primitives (patched/deprecatePatch) to prevent non-deterministic execution exceptions and workflow corruption during rolling deployments.
globs: src/workflows/**/*.{ts,js,go,java,py}, workflows/**/*.{ts,js,go,java,py}, lib/workflows/**/*.{ts,js}
alwaysApply: true
verified_by: "agentrules.org"
license: "CC-BY-4.0"
source: "https://agentrules.org/rules/temporal-workflow-determinism-patching-invariant"
---

# Temporal Workflow Determinism & Dynamic Patch Invariant Guardrail

> **Severity**: CRITICAL | **Category**: backend
> **Anti-Pattern Warning**: Mutating Workflow Control Flow or Schedule Commands Without Version Patching

## System Constraints
You are a Principal Engineer enforcing Temporal Workflow Determinism & Dynamic Patch Invariant. Mandate that workflow execution history replay remains completely deterministic across rolling deployments. Reject any direct mutations of existing workflow execution topologies that fail to utilize Temporal's explicit patching APIs (patched, deprecatePatch). Enforce strict separation between non-deterministic side-effects (which belong strictly in activities) and deterministic workflow orchestration logic.

## Strict Guidelines
- Engineers MUST ALWAYS wrap new or modified command-producing workflow branches in `workflow.patched(patchId)` to safeguard in-flight replays.
- Engineers MUST NOT introduce non-deterministic operations (e.g., `Math.random()`, `Date.now()`, standard `setTimeout`, raw UUID generation, direct network I/O, or mutable global state) into workflow logic.
- Code SHOULD transition from `workflow.patched(patchId)` to `workflow.deprecatePatch(patchId)` only after verifying that zero running executions reference the pre-patch history.
- Services MUST execute non-deterministic I/O operations and database queries exclusively within Temporal Activities, passing results back to workflows via serializable payloads.
- Components NEVER remove a patch identifier from workflow code until all closed workflow runs containing the unpatched path have passed their retention period or migration verification.

## Bad vs Good Implementations
### Modifying Workflow Execution Flow With Temporal Patching

#### Bad Antipattern (AI Common Hallucination)
> **Why it fails**: Directly injecting `sendSmsNotification` before `sendEmail` alters the sequence of generated workflow history commands. When worker nodes running the updated code replay event histories from workflows started on the previous version, the event types diverge, throwing a fatal NonDeterminismError and stalling all active workflows.
```typescript
import { proxyActivities, sleep } from '@temporalio/workflow';
import type * as activities from './activities';

const { chargeCustomer, sendEmail, sendSmsNotification } = proxyActivities<typeof activities>({
  startToCloseTimeout: '1 minute',
});

export async function subscriptionOrderWorkflow(userId: string, amount: number): Promise<void> {
  await chargeCustomer(userId, amount);
  // ANTI-PATTERN: Direct modification of command topology breaks in-flight replay.
  // An in-flight workflow that previously ran sendEmail will now encounter sendSmsNotification
  // during history replay, throwing a NonDeterministicWorkflowPolicy / NonDeterminismError.
  await sendSmsNotification(userId, 'Payment received');
  await sendEmail(userId, 'Invoice ready');
  await sleep('30 days');
}
```

#### Production Standard (Correct)
> **Standard**: Using `patched('send-sms-notification-v1')` informs the Temporal replay engine that an explicit divergence point exists. Historical replays observe the absence of the marker in their history and cleanly bypass the new command, while new executions record the marker and execute the branch deterministically.
```typescript
import { proxyActivities, sleep, patched } from '@temporalio/workflow';
import type * as activities from './activities';

const { chargeCustomer, sendEmail, sendSmsNotification } = proxyActivities<typeof activities>({
  startToCloseTimeout: '1 minute',
});

export async function subscriptionOrderWorkflow(userId: string, amount: number): Promise<void> {
  await chargeCustomer(userId, amount);
  
  // PRODUCTION FIX: Guard newly introduced command topologies with patched().
  // Replaying executions generated prior to this change will evaluate to false,
  // executing the legacy path and preserving history determinism.
  if (patched('send-sms-notification-v1')) {
    await sendSmsNotification(userId, 'Payment received');
  }
  
  await sendEmail(userId, 'Invoice ready');
  await sleep('30 days');
}
```
Recommended MCP Servers (mcp-serverlist.com)

Equip agent with system tools to verify code for this stack.

Temporal MCP Server
Enables workflow replay validation and inspection of Temporal execution histories directly inside AI coding tools.
Recommended Agent Skills (askills.dev)

Ready-to-use executable skill functions tailored to this stack.

Temporal Replay CLI
CLI utility to download historical workflow executions and run SDK replay tests against updated workflow definitions prior to deployment.
Architectural Specification & Invariant Rationale

Architectural Invariant Design: Temporal Workflow Determinism & Dynamic Patch Invariant Guardrail

Temporal Workflow Determinism & Dynamic Patch Invariant Guardrail defines an industrial-grade behavioral standard for backend engineering. Temporal workflows must maintain absolute event-history replay determinism across deployments. Any modification to existing workflow definitions—including reordering activities, mutating control-flow branches, or removing timers—must use deterministic versioning primitives (patched/deprecatePatch) to prevent non-deterministic execution exceptions and workflow corruption during rolling deployments. 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: Mutating Workflow Control Flow or Schedule Commands Without Version Patching 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 ModeAI Symptom (The Anti-Pattern)SeverityProduction Impact & Remedy
AI Hallucination & Deprecation DriftMutating Workflow Control Flow or Schedule Commands Without Version PatchingCritical
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 InconsistencyAI 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:

1

Engineers MUST ALWAYS wrap new or modified command-producing workflow branches in `workflow.patched(patchId)` to safeguard in-flight replays.

Engineers MUST ALWAYS wrap new or modified command-producing workflow branches in `workflow.patched(patchId)` to safeguard in-flight replays.

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.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
2

Engineers MUST NOT introduce non-deterministic operations (e.g., `Math.random()`, `Date.now()`, standard `setTimeout`, raw UUID generation, direct network I/O, or mutable global state) into workflow logic.

Engineers MUST NOT introduce non-deterministic operations (e.g., `Math.random()`, `Date.now()`, standard `setTimeout`, raw UUID generation, direct network I/O, or mutable global state) into workflow logic.

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.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
3

Code SHOULD transition from `workflow.patched(patchId)` to `workflow.deprecatePatch(patchId)` only after verifying that zero running executions reference the pre-patch history.

Code SHOULD transition from `workflow.patched(patchId)` to `workflow.deprecatePatch(patchId)` only after verifying that zero running executions reference the pre-patch history.

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.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
4

Services MUST execute non-deterministic I/O operations and database queries exclusively within Temporal Activities, passing results back to workflows via serializable payloads.

Services MUST execute non-deterministic I/O operations and database queries exclusively within Temporal Activities, passing results back to workflows via serializable payloads.

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.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
5

Components NEVER remove a patch identifier from workflow code until all closed workflow runs containing the unpatched path have passed their retention period or migration verification.

Components NEVER remove a patch identifier from workflow code until all closed workflow runs containing the unpatched path have passed their retention period or migration verification.

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.
Enforcement:Integrated into the Agent Pack rule file. When Cursor, Claude Code, or Codex processes this prompt, it applies this constraint before emitting syntax.
Technical Questions & Answers

Frequently Asked Technical Questions

Common questions developers face when configuring AI coding assistants for this stack:

Q:Why is Temporal Workflow Determinism & Dynamic Patch Invariant Guardrail critical for AI coding assistants?

Temporal workflows must maintain absolute event-history replay determinism across deployments. Any modification to existing workflow definitions—including reordering activities, mutating control-flow branches, or removing timers—must use deterministic versioning primitives (patched/deprecatePatch) to prevent non-deterministic execution exceptions and workflow corruption during rolling deployments. Without explicit behavioral boundaries, AI coding assistants (Cursor, Claude Code, Windsurf, Codex) rely on training data averages, which frequently produce deprecated, inefficient, or vulnerable code patterns.

Q:How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Mutating Workflow Control Flow or Schedule Commands Without Version Patching) 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.

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