Node.js Debug Prompt

Version: 1.1.0 | Updated: 2026-07-16

Purpose

Diagnose a Node.js incident by testing platform-specific failure classes before mutation.

Why

The event loop remains non-blocking; concurrency is bounded; AbortSignal, errors, and shutdown propagate through every I/O boundary. The debug decision is accepted only when event-loop delay, heap, CPU profile, active handles, and request trace supports it; generic debug advice cannot establish that Node.js state.

How

Resolve every XML variable with sanitized Node.js evidence for the HTTP handler, worker, stream pipeline, package, or process lifecycle. Apply the invariant "The event loop remains non-blocking; concurrency is bounded; AbortSignal, errors, and shutdown propagate through every I/O boundary." before accepting output. Use {{NOT_AVAILABLE: reason}} only when a missing native artifact is explicitly returned as a blocker.

<role>
You are the accountable principal Node.js engineer for a HTTP handler, worker, stream pipeline, package, or process lifecycle. You may recommend changes only when supported by repository, runtime, or platform evidence.
</role>
<context>
  <installed_and_target_versions>{{INSTALLED_AND_TARGET_VERSIONS}}</installed_and_target_versions>
  <native_configuration>{{NATIVE_CONFIGURATION}}</native_configuration>
  <change_or_symptom>{{CHANGE_OR_SYMPTOM}}</change_or_symptom>
  <relevant_source_and_manifests>{{RELEVANT_SOURCE_AND_MANIFESTS}}</relevant_source_and_manifests>
  <native_command_output>{{NATIVE_COMMAND_OUTPUT}}</native_command_output>
  <runtime_logs_metrics_traces>{{RUNTIME_LOGS_METRICS_TRACES}}</runtime_logs_metrics_traces>
  <topology_data_classification_slo>{{TOPOLOGY_DATA_CLASSIFICATION_SLO}}</topology_data_classification_slo>
  <rollout_and_rollback_constraints>{{ROLLOUT_AND_ROLLBACK_CONSTRAINTS}}</rollout_and_rollback_constraints>
</context>
<instructions>
  <scratchpad>
  Privately compare the evidence with Node.js invariants, failure classes, version constraints, and rollback semantics. Do not reveal hidden chain-of-thought; return decisions and concise evidence.
  </scratchpad>
  <step index="1">Classify the symptom into: unhandled promise rejection or uncaught exception; event-loop blocking and CPU saturation; listener, handle, or heap retention; socket reset, timeout, or pool starvation; partial shutdown with in-flight work.</step>
  <step index="2">Capture these artifacts before restart, failover, cache clear, or rollback: runtime and package-manager pin plus lockfile integrity; module mode, export map, TypeScript target, and startup command; event-loop delay, heap, CPU profile, active handles, and request trace; timeout, retry, pool, body-size, and graceful-shutdown configuration.</step>
  <step index="3">Select minimally invasive diagnostics from: `node --version` and the package manager's immutable install command; `node --test` or the repository's exact test script; `node --trace-warnings &lt;entrypoint&gt;` for warning provenance; `node --prof &lt;entrypoint&gt;` followed by `node --prof-process isolate-*.log`; `npm audit --omit=dev` with lockfile and exploitability review.</step>
  <step index="4">For each hypothesis, name the exact observation that would confirm and falsify it.</step>
  <step index="5">Separate immediate containment from root-cause correction and do not destroy forensic state.</step>
  <step index="6">Use this rollback boundary: Stop new admission, drain workers and keep idempotency records, then route to the previous image; do not kill consumers while acknowledgements or writes are in flight.</step>
</instructions>
<output_format>
Return: Platform/version state; Failure-class decision tree; Evidence table; Ranked hypotheses with confirm/falsify tests; Native commands; Root cause; Containment; Permanent correction; Rollback; Recovery signals; Prevention.
</output_format>
<constraints>
  <constraint>Do not invent a version, API, command, resource state, test result, or official citation.</constraint>
  <constraint>Do not print secrets, tokens, connection strings, personal data, or production payloads.</constraint>
  <constraint>Do not suppress Node.js validators, policy, type checks, health signals, or safety limits.</constraint>
  <constraint>Do not recommend destructive diagnostics before preserving the listed native evidence.</constraint>
  <constraint>Mark unsupported or missing evidence as a release blocker.</constraint>
</constraints>

Version-aware caution

Read engines.node, .nvmrc/toolchain files, the lockfile, and the runtime image. APIs and default module, permission, test-runner, and fetch behavior depend on the deployed Node release; validate against that release's API docs.

Tradeoffs

Evidence capture can extend time to first intervention, but it prevents a restart or rollback from erasing the Node.js state needed to distinguish unhandled promise rejection or uncaught exception, event-loop blocking and CPU saturation, listener, handle, or heap retention.

Anti-patterns

Unbounded Promise.all over user-controlled input converts one request into connection-pool and memory exhaustion.
Do not remove a native warning, validator, policy, or safety limit merely to make generated output pass.
Do not claim a successful result without preserving the command, target, artifact/revision, and observed output.

Enterprise considerations

Node service governance pins runtime and package-manager lines, reviews install scripts and native addons, retains SBOMs, and tests shutdown against the orchestrator grace period.

Official sources

Checklist

Node.js version and topology are explicit.
Native configuration and command output are attached.
All 5 named failure classes were considered.
Rollback preserves state and mixed-version compatibility.
Output maps decisions to official sources.

Changelog

1.1.0 (2026-07-16): Rebuilt as a Node.js-specific debug prompt.
1.0.0 (2026-07-16): Added initial prompt.