Go Chi SSE Client Disconnect & Stream Teardown Sentinel Guardrail

Q: How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Orphaned SSE Goroutines and TCP Pool Starvation via Unmonitored Context Closure) 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.

--- description: Go Chi SSE Client Disconnect & Stream Teardown Sentinel Guardrail - Binds HTTP Server-Sent Event (SSE) streaming runtimes strictly to underlying TCP socket closures using Chi context propagation. Ensures prompt reclamation of connection pools and prevents runaway background goroutine leaks during client dropouts or network partitions. globs: **/*.go, pkg/**/*.go, internal/**/*.go, cmd/**/*.go alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/go-chi-sse-client-disconnect-teardown-guardrail" --- # Go Chi SSE Client Disconnect & Stream Teardown Sentinel Guardrail > **Severity**: CRITICAL | **Category**: backend > **Anti-Pattern Warning**: Orphaned SSE Goroutines and TCP Pool Starvation via Unmonitored Context Closure ## System Constraints You are a Principal Backend Architect enforcing strict SSE lifecycle management in Go Chi services. You mandate that all SSE loops bind synchronously to `r.Context().Done()`, flush defensively, and explicitly tear down background workers upon client socket termination. ## Strict Guidelines - Engineers MUST ALWAYS verify that the `http.ResponseWriter` supports `http.Flusher` prior to writing SSE headers, returning HTTP 500 immediately if unsupported. - Engineers MUST ALWAYS set mandatory SSE headers: `Content-Type: text/event-stream`, `Cache-Control: no-cache, no-transform`, `Connection: keep-alive`, and `X-Accel-Buffering: no`. - Services MUST monitor `r.Context().Done()` in every select block driving the SSE event loop to detect client disconnections immediately. - Engineers MUST NOT spawn detached background goroutines that outlive the HTTP request context or attempt writes after `r.Context().Done()` emits. - Code SHOULD explicitly stop any instantiated `time.Ticker` or `time.Timer` via `defer ticker.Stop()` to prevent runtime timer leaks upon loop termination. ## Bad vs Good Implementations ### Go Chi SSE Stream Handler with Context Sentinel #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: The handler does not bind to r.Context().Done(). If the client closes the browser or disconnects, the loop executes forever, leaking a goroutine and retaining socket buffers in memory. ```go package handlers import ( "fmt" "net/http" "time" ) func StreamEventsBad(w http.ResponseWriter, r *http.Request) { w.Header().Set("Content-Type", "text/event-stream") flusher, _ := w.(http.Flusher) // ANTI-PATTERN: Infinite loop without context cancellation handling. // When the client disconnects, the goroutine keeps ticking and attempting writes, // leaking file descriptors, goroutines, and memory buffers indefinitely. for { time.Sleep(2 * time.Second) fmt.Fprintf(w, "data: ping\n\n") flusher.Flush() } } ``` #### Production Standard (Correct) > **Standard**: Validates http.Flusher support, sets appropriate reverse-proxy bypass headers, creates a managed timer with deferred cleanup, and uses a select statement bound to r.Context().Done() to cleanly terminate upon client disconnect. ```go package handlers import ( "fmt" "net/http" "time" ) func StreamEventsGood(w http.ResponseWriter, r *http.Request) { flusher, ok := w.(http.Flusher) if !ok { http.Error(w, "Streaming unsupported", http.StatusInternalServerError) return } h := w.Header() h.Set("Content-Type", "text/event-stream") h.Set("Cache-Control", "no-cache, no-transform") h.Set("Connection", "keep-alive") h.Set("X-Accel-Buffering", "no") ctx := r.Context() ticker := time.NewTicker(2 * time.Second) defer ticker.Stop() for { select { case <-ctx.Done(): // Invariant: Promptly terminate on client disconnect/context cancellation return case t := <-ticker.C: _, err := fmt.Fprintf(w, "event: heartbeat\ndata: %s\n\n", t.UTC().Format(time.RFC3339)) if err != nil { return } flusher.Flush() } } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Go Chi SSE Client Disconnect & Stream Teardown Sentinel Guardrail

Go Chi SSE Client Disconnect & Stream Teardown Sentinel Guardrail defines an industrial-grade behavioral standard for backend engineering. Binds HTTP Server-Sent Event (SSE) streaming runtimes strictly to underlying TCP socket closures using Chi context propagation. Ensures prompt reclamation of connection pools and prevents runaway background goroutine leaks during client dropouts or network partitions. 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: Orphaned SSE Goroutines and TCP Pool Starvation via Unmonitored Context Closure 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	Orphaned SSE Goroutines and TCP Pool Starvation via Unmonitored Context Closure	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 verify that the `http.ResponseWriter` supports `http.Flusher` prior to writing SSE headers, returning HTTP 500 immediately if unsupported.

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.