Typically, the development team adds requirements as a project moves from the PRD to the detailed design.

Outline (skeleton you can skim)

• Opening: a simple scenario many teams recognize—requirements drift between docs and design.

• Core idea: when a requirement shows up between the product requirements and the detailed design, it’s usually the development team contributing new detail during design.

• Why this happens: design phase reveals architecture, tech constraints, and feasibility issues that the high-level requirements didn’t expose.

• Who does what: roles of BA, dev, QA, and customer; why it’s a collaborative process.

• Signs and implications: how to spot a design-stage addition and what it means for scope, schedule, and traceability.

• How to handle it well: governance, documentation, change control, and healthy communication.

• Quick practical tips: tools, artifacts, and habits that keep everyone aligned.

• Closing thought: a natural part of SDLC when kept transparent and well-managed.

When a new detail slips in between the product requirements and the detailed design, what happened? If you’ve walked through a real software project, you’ve probably seen this scene: a crisp Requirements Document sits on one side; a Technical Design Document sits on the other; and somewhere in between, a new line item appears. The answer most teams settle on is simple in one sense and a bit messy in another: the development team added the requirement during the design phase. It’s not about blame; it’s about how software grows as we understand it deeper.

Let me explain why this happens in practice. The product requirements describe what the system must do from a user’s perspective. They’re high-level, focused on value, user stories, and outcomes. They sketch the goals—“the system should support X,” or “users should be able to do Y.” But as soon as designers and developers start mapping those goals to concrete architecture, data flows, and interfaces, new questions pop up. What data do we actually need to store? What system boundaries are we crossing? Are there performance or security constraints we hadn’t fully considered? In other words, the design phase peels back layers of complexity that aren’t obvious in the initial requirements.

This is a natural part of the software development journey. The design process is where you translate intent into reality, and that translation often reveals gaps, dependencies, or opportunities for improvement. The development team, evaluating feasibility and technical debt, might spot a missing hook, an edge case, or a more efficient approach. If those insights require changes to the requirements or to how the system is described, a new requirement can appear—typically in the transition from the product requirements document to the detailed design document.

Think of it like building a house. The architect starts with what the client wants—bedrooms, a kitchen, a living room. As the blueprints take shape, the team realizes something: the main load-bearing wall needs reinforcing, or the ductwork must pass through a different wall, or the wiring plan would be cleaner if we reconfigure a corridor. You don’t blame the client for the new constraint; you incorporate it into the plan. The same logic applies here. The design phase reveals architectural realities and technological constraints that rewrite a bit of the plan.

Who’s responsible for that addition? In most SDLC realities, the development team plays a central role in turning abstract requirements into concrete design. They’re the ones who translate capability into constructible elements, and they’re the ones who can foresee practical implications—like how a new interface might affect data synchronization, or what latency a certain component could introduce. That doesn’t mean the other roles go quiet. Business analysts, testers, and even customers contribute to requirements, but the act of adding a design-driven requirement is typically the development team’s domain. It’s a signal that the team is refining the map to ensure the destination is reachable, not just imagined.

But this scenario rarely appears in isolation. It carries a few telltale signs and a few downstream effects worth watching:

• Signs you’re seeing a design-driven addition

• You notice a new item that ties directly to a technical constraint (like a data format, an API boundary, or a performance cap) that wasn’t described in the original user-focused requirements.

• The new item appears in the design explanation, traceability matrix, or a design review note rather than in the business-facing requirement list.

• The team flags that “to implement this requirement, we need this other capability” or “this constraint forces us to adjust this part of the workflow.”

• What it means for scope and timing

• It’s a natural moment to revisit scope. If a design constraint pushes back on what was initially considered in-scope, stakeholders may need to renegotiate priorities.

• Schedule pressure can creep in. Adding a design-driven requirement might require additional development effort, testing, or infrastructure work. It’s not a failure; it’s a reality check that keeps the project honest about feasibility.

• The impact on traceability and governance

• Change control becomes important. A new requirement—the result of deeper design thinking—should be captured, approved, and linked back to both the business need and the technical rationale.

• Documentation quality matters more than ever. If you can’t trace why a change was made, you risk misalignment later on, especially when QA or regulatory reviews come into play.

How to manage this well, without killing momentum

First, embrace a light but sturdy governance rhythm. When the design reveals new needs, record them cleanly:

• Update the design artifacts with the rationale: why is this added, what problem does it solve, what are the trade-offs?

• Link the new item to the high-level requirement it supports. That helps everyone see the connection from user value to technical delivery.

• Create or revise a change request or a lightweight ticket in your issue-tracking tool (whether it’s Jira, Azure DevOps, or a similar platform). Include acceptance criteria, dependencies, and a rough impact estimate.

Second, keep communication crystal clear. A change that begins in the design room can feel like a zig in the project path. Here’s the trick: narrate the why, not just the what. Say things like, “We’re adding this requirement because X constraint makes the original approach brittle in Y scenario,” or, “This interface change will reduce future maintenance cost by Z.” People respond to why, not just what.

A small digression that’s worth tying back: you’ll often hear people talk about “traceability” and “alignment.” In practice, that means every requirement has a purpose, and every design decision has a traceable reason. It’s not about policing creativity; it’s about ensuring the product remains coherent as both business goals and technical realities evolve. When done well, you create a trail you can follow later—whether for audits, onboarding new teammates, or simply explaining why a particular feature behaves differently than it initially appeared in the plan.

Tactically, here are a few habits that help a healthy transition from requirements to design—and beyond:

• Maintain a lightweight requirements backlog that’s visible to all stakeholders. You don’t need a moon-shot process; you just need a place where changes can be proposed, discussed, and rated for impact.

• Use design reviews as a formal but friendly checkpoint. Bring in the right folks—architects, developers, testers, and a BA or product owner—to critique the proposed changes with the same rigor you’d apply to any critical decision.

• Keep acceptance criteria crisp and connected to user value. When a new requirement lands, define what “done” looks like in both a technical and a user-facing sense.

• Reward collaboration over silos. If a change is born in design, invite the business side to weigh in on whether this added capability shifts user value or priorities.

A few practical talking points to keep in mind, especially when you’re leading or participating in these conversations:

• Don’t treat the design-driven addition as a problem to be solved at the end. It’s a design evolution that helps the team stay true to the user’s needs while respecting technical realities.

• If the change seems big, consider staged implementation. You can phase in the new capability, test it in a controlled way, and then broaden its reach.

• Remember the testers in the room. They’re not after roadblocks; they’re after clarity. Their feedback on how to validate the new requirement early can save a lot of friction later.

• For teams using modern tooling, leverage linked artifacts. A change request should connect to the affected user story, the design rationale, the affected components, and the test cases. In Jira terms, you want a clear web of links that makes the decision easy to audit later.

To bring this back to the heart of what was asked: when a requirement shows up between the product requirement document and the detailed design document, the most likely explanation is that the development team contributed that requirement during the design work. This isn’t a misstep; it’s a natural byproduct of turning broad goals into buildable reality. The key is how you handle it—how you document it, how you communicate it, and how you keep the project aligned as you move from concept to concrete implementation.

One last thought to ground the idea: there’s a real value in teams that can turn back from the drawing board with fresh, actionable insights that improve the product for users. Instead of seeing this as drift or driftwood, view it as a refinement process. The best products emerge when design and development collaborate with a shared purpose—to deliver something that not only works but also feels right to the people who will use it.

If you’re navigating a project right now and notice a new requirement popping up during design, take a breath, map it to the underlying business need, and loop in the right voices early. A well-managed change is less a detour and more a smarter route to a robust solution. And in the end, that’s what good requirements engineering is really all about: guiding teams toward outcomes that matter, without letting surprises derail the journey.