When a value may be null or undefined, don't silently coalesce it to a generic default without considering the semantic consequences. A careless `?? 0` or `?? "default"` can mask real errors (e.g., returning 0 for a queue size that failed to load, hiding an alert that should stay active) or produce incorrect behavior (e.g., treating a missing `organizationId` as a shared "default" bucket instead of logging and skipping the operation). Before adding a fallback, ask whether the caller should instead explicitly handle the nullable case, log the anomaly, or propagate the absence of a value rather than papering over it. When a fallback is genuinely appropriate, make the intent explicit and resolve ambiguity up front rather than relying on implicit undefined propagation through chained conditionals: ```ts // Bad: undefined tier falls through to the wrong branch if (authParams?.tier === "free") { return 100; } return 10_000; // Good: explicitly normalize the nullable value first const tier = authParams?.tier ?? "free"; if (tier === "free") { return 100; } return 10_000; ``` Likewise, guard against nullable/empty collections before indexing into them, rather than assuming a value exists: ```ts if ( responseBody?.item?.content && Array.isArray(responseBody.item.content) && responseBody.item.content.length ) { const first = responseBody.item.content[0]; // ... } ``` In short: treat every `?.` and `??` as a decision point—decide deliberately whether to default, skip, log, or surface the missing value, rather than letting an implicit fallback hide bugs or alerting gaps.