Cancel server response body streams on client disconnects

Many web and backend teams face a subtle but growing failure mode: server response body streams (SSE, long-polling, audio/video, chunked HTTP) continue to consume CPU, memory, and file descriptors after a client has disconnected, creating leaks and tail-costs that are hard to observe and expensive to fix. This problem is especially acute for streaming-first services and in serverless/edge environments where runtimes are ephemeral and every leaked connection directly translates to extra billed time or throttled capacity. A practical product would be a small, cross-runtime library plus optional runtime agent and observability layer that reliably detects client TCP/HTTP disconnects and cancels in-progress response body streams, ships SDKs for Node/Rust/Go/Deno, provides serverless/edge shims, and emits actionable metrics and policies (timeouts, grace periods, fallback cancellation). The market is sizable and timely: we estimate a TAM of $8.4B (700k web and backend teams × $12k ARR tooling spend), the opportunity scores 92/100 with revenue potential 88/100, and platform trends (streaming-first apps, serverless/edge, frameworks exposing streaming primitives) materially increase demand right now. This idea can stand out by combining deterministic cancellation semantics, low-latency detection that works despite proxies/CDNs, easy framework integrations (e.g., Next.js, popular HTTP servers), and observability that proves ROI in reduced wasted compute and incident count. Real challenges are nontrivial: achieving cross-runtime compatibility, handling network intermediaries that mask disconnects, and persuading engineering teams to add new instrumentation; competition is medium and early partnerships or an open-source reference will likely be necessary to build credibility. If you can deliver compact, low-overhead instrumentation and clear cost/incident reduction metrics, this is a focused niche with measurable business value and a credible path to adoption.