Growth Frameworks

Reasoning Models vs. Agentic AI: Choosing the Right Capability for 2025

Artificial intelligence is becoming deeply embedded in all aspects of companies’ operations, from strategic planning to customer support. As adoption grows, leaders face a new question: what kind of AI capability does your business actually need? Summit’s Sharon Lin examines the differences between reasoning models and agentic AI and offers a practical framework for when to use, combine and govern these capabilities to drive performance and scale responsibly.

Two terms seem to dominate the conversation today: reasoning models and agentic AI. They’re often mentioned together, but they serve distinct purposes and carry very different operational implications. Understanding what each does best and when to combine them can help organizations apply AI in ways that are both practical and defensible.

Reasoning vs. Agentic: Thinking and Doing

Reasoning models are optimized to think through multi-step problems and produce high-quality answers or plans. Give them a set of inputs — contracts, support tickets, a board deck — and they can synthesize, compare and recommend next steps. They follow instructions, decompose complex requests and generate structured outputs that humans can review and refine.

Agentic AI, by contrast, is designed for execution. It plans steps, calls APIs, updates CRM fields, sends drafts for approval, schedules follow-ups and monitors for change, all while pursuing a defined goal across tools and systems.

In short: reasoning models elevate analysis; agents deliver coordinated action.

Why This Matters Now

Three developments are making both types of AI more viable in 2025.

1. Reliability and control have improved. Reasoning systems are now better at step-by-step thinking and at adhering more closely to instructions when grounded in data. Agent frameworks have matured with role-based permissions, audit logs and human-in-the-loop checkpoints that support safer, revocable actions.

2. Tool use is now more standard. Rather than “guessing,” models routinely consult calculators, retrieval layers and business applications as part of their process, reducing hallucinations and improving accuracy.

3. Observability is catching up. Teams can now measure reasoning quality (accuracy, completeness, grounding) and agent performance (task success rate, handoff frequency, latency and cost), making AI deployments feel more like running a product than a one-off experiment.

Together, we believe these shifts make it possible to apply reasoning and agentic systems deliberately, using each where it adds the most value.

Different Strengths, Shared Potential

Reasoning models, in our view, are most effective when the desired output is analysis or judgment — executive memos, plans, risk reviews or QBR narratives. They’re relatively simple to pilot since they draw on existing documents or curated data sources and they allow for predictable cost and human review before decisions are finalized. Their limits are just as important to understand. Without strong grounding in company data and policies, reasoning models can produce confident but inaccurate conclusions. They also can lack persistence across interactions unless you design a memory layer, and while they can use tools, they don’t act autonomously without orchestration.

Agentic AI tends to excel when the outcome requires consistent, cross-system execution. Agents are typically well-suited to operational workflows such as lead enrichment and follow-ups, financial reconciliation, entitlement checks or support triage. With proper instrumentation, agents can run continuously, escalate low-confidence cases and deliver measurable throughput. But they come with trade-offs: increased security and maintenance overhead, dependency on clean data and clear rules, and potential latency or cost as action chains grow more complex. Importantly, agents need explicit product ownership to ensure playbooks stay current as processes and policies evolve.

In practice, many companies benefit from pairing the two. If the goal is a document, plan or recommendation that benefits from human review, start with a reasoning model. If the goal is measurable progress in a defined workflow, such as closing renewals on time, resolving tickets within an SLA, or reconciling financials daily, an agent is the better fit. Combining both models can be powerful as they bring together structured reasoning and coordinated action: the reasoning model generates a transparent plan — who to contact, what to say, which fields to update — and the agent executes it, escalating to a human when confidence is low or when actions are high risk.

Building, Buying and Partnering Wisely

In our view, the default posture for most growth companies should be to buy the platform foundations and build the differentiating layers. We believe this approach balances efficiency, value and control, allowing teams to move quickly while retaining ownership over what truly sets the company apart.

Here are our recommendations:

  • Build when the workflow is core to differentiation and your proprietary data, nuanced playbooks or decision logic help define your competitive advantage. Building can also make sense when the workflow is subject to strict regulatory or data-storage requirements, when deployment must happen in your own environment for policy control, or when sustained volume justifies owning unit economics and roadmap. These are the layers that we believe warrant continued investment over time.
  • Buy the elements that are standard within the industry (e.g. grounding, redaction, observability, orchestration, agent policy), especially when the vendor already integrates with your core systems. Buying a ready-made product provides security, admin controls and cost transparency out of the box, reducing the need for internal support and maintenance. Start with the built-in settings and then extend them only where your business requires customization.

Vendor diligence, when buying, should center on four areas:

  1. Data policy: retention, training use, residency and isolation
  2. Security and deployment: SSO, SCIM, audit depth and private or tenant options
  3. Observability and control: metrics for cost, latency and errors plus approval gating
  4. Portability and pricing: bring-your-own-model options, log exports and transparent billing

Striking the balance between buying for stability and building for differentiation can help companies accelerate adoption while maintaining flexibility and control.

The Bottom Line

As companies consider where and how to apply these capabilities, our guidance is to focus less on which model to choose and more on how to approach implementation, governance and measurement.

Complement, don’t choose. Reasoning models elevate analysis and planning and agents turn those plans into execution. Durable systems pair them: reason to a plan, execute under guardrails and escalate when confidence is low.

Govern for scale. Treat high-impact workflows like products: assign ownership, publish SLAs, define “do-not-cross” policies and review performance regularly. Strong governance converts early wins into repeatable, auditable operations.

Measure what matters. For reasoning: track accuracy, grounding rate, time-to-draft and rework frequency. For agents: monitor task success, approvals per 100 actions, handling time and unit cost. Expand your scope only where metrics beat baseline and stay within budget.

Adopt established platforms, develop what sets you apart. Accelerate with vendor platforms, then invest in the proprietary layers that increase differentiation. Negotiate zero-retention and model-swap rights up front, and keep an exit path so your strategy, not a contract, defines your roadmap.

Reasoning models and agentic AI aren’t competing approaches; we believe they’re complementary tools for different kinds of problems. Knowing when to deploy each and how to govern both effectively will define how AI drives business performance in the years ahead.

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Related Experience

The content herein reflects the views and opinions of Summit Partners and is intended for executives and operators considering partnering with Summit Partners. The information herein has not been independently verified. In recent years, technological advances have fueled the rapid growth of artificial intelligence (“AI”), and accordingly, the use of AI is becoming increasingly prevalent in a number of sectors. Due to the rapid pace of AI innovation, the broadening scope of potential applications, and any current and forthcoming AI-related regulations, the depth and breadth of AI’s impact - including potential opportunities – remains unclear at this time.  

Direct references or inferences made herein to “expertise” or any party being an “expert” or other particular skillsets are based solely on the belief of Summit Partners and are provided only to indicate proficiency as compared to an average person. Such references or inferences should not be construed or relied upon as an indication of future performance or other future outcomes.

Information herein is as of November 2025.

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