Principal Drift

Over the past year I’ve reviewed enterprise agent architectures at roughly two dozen organizations, including banks, retailers, healthcare systems, and a couple of regulators. The architecture diagrams have been reliably impressive. There are boxes for the MCP gateway, the tool registry, the vector store, the orchestrator, the policy engine, and the observability stack. There are arrows showing how agents discover each other, share context, and call tools across the mesh. By 2026 standards, these are the table-stakes pictures for any serious agentic deployment. But what none of them show anywhere is who the agents are, whose authority they carry, or who answers when they’re wrong.

That omission has a name worth using: principal drift, the steady decoupling, in any sufficiently large agent system, between the human authority a recorded action is supposed to derive from and the actor that actually took it. What looks like a defensible identity posture on the day you ship your first agent quietly degrades as agents multiply, compose, and outlive their original initiatives. Principal drift isn’t three independent failure modes; it’s one cascade. Identity collapses first. Authority erodes next, because there is no longer a stable principal to bind policy to. Accountability dissolves third, because the cost of agent error lands on whichever team has the weakest negotiating position when the incident review starts. Stopping the cascade means intervening at the first link, but almost no enterprise agent platform does so right now.

To see the cascade run, take the most boring possible enterprise agent, a refund agent, and watch.

A customer-service rep, fielding a chat, asks the agent to process a $48 refund for a damaged item. The agent checks eligibility, issues the refund, posts an update. The audit log records the action as taken by something like refund-agent-prod-03, running under a service principal owned by the customer-service platform team. That entry is true, but it’s also useless. The agent wasn’t acting as refund-agent-prod-03. It was acting as the rep, on behalf of the customer, under a delegation chain nobody recorded. In a well-built system, customer, rep, agent identity, and service principal are recorded together, queryable as a chain, and durable beyond the session. In most production systems today they aren’t. This is the first link in the cascade, where identity collapses to a generic service principal, and there’s no longer a who to attach anything else to.

Authority erodes next. The refund agent has an issue_refund tool that can technically refund any order. Its authority is supposed to be narrower (refunds up to $200, orders under 90 days, customers in good standing, automatic escalation above $50), but that authority lives in a prompt or a YAML file or a Notion page the team last updated when the policy was different. The runtime enforces capability, but nobody really enforces authority. When a poisoned input or a confused chain of reasoning leads the agent to refund $1,800 to the wrong customer, there’s no clean answer to the postincident question “Who approved this policy?” because the policy was never an artifact. The same pattern is worse at higher stakes: Imagine a coding agent with merge access to a protected branch, instructed by a prompt embedded in a code comment to “log configuration values for debugging,” silently exfiltrating secrets to an external monitoring service.

Accountability then dissolves. The team that built the agent says it followed policy. The team that wrote the policy says it didn’t anticipate the input. The team that operates the platform says the agent was running as a service principal whose behavior they don’t own. The audit log may show the action, but it doesn’t show the reasoning that produced the action, the retrieved context that shaped the reasoning, or the prompt history that framed the retrieval. Postincident review becomes archaeology, and the cost is absorbed, eventually, by whoever has the weakest negotiating position when the meeting ends.

Is any of this new? We have IAM, identity governance, policy as code, audit trails, SIEMs, and 30 years of compliance practice. Why isn’t this just IAM done properly? Because IAM was built around assumptions agents violate. IAM and IGA assume a population of principals that changes on human timescales: People get hired, people leave, and service accounts rotate quarterly. Agents are spun up per session and compose into chains where one agent calls another, which calls a third, impersonating users through delegated tokens that traditional IGA cannot represent as a chain at all. Policy engines fire at the moment of action, at the API, the database, and the network. Agents make their most consequential decisions before they hit those enforcement points, in the reasoning step that selects which tool to call and with what arguments. Mature audit logs assume that replaying the inputs reproduces the output. But for agents, replaying the prompt and the retrieval can yield a different action, because the model itself contributes state the log doesn’t capture. The instruments fire, the dashboards turn green, and the agent that quietly exfiltrated secrets still does so. The audit log records the action as agent-service-01, which again is both true and useless.

This is also where the vendors selling a consolidated stack want you to skip ahead. Microsoft’s Entra Agent ID, currently in public preview, is the most polished solution to date, extending the conditional access, identity governance, and identity protection used for humans and workloads to cover AI agents as a new identity type, but Google and Salesforce are also building this layer. The marketing line is that agents receive the same identity-driven protections as the rest of the workforce. That’s a real step forward in addressing the first link of the cascade, but it isn’t governance. It’s a control plane with a governance plane’s marketing. Conditional access can tell you whether the agent’s access attempt was permitted. It can’t tell you whether the decision the agent made before that access attempt was within its authority, why the agent reached the decision, or which business unit owns the policy the decision was supposed to obey.

The actual governance plane has to capture decisions, not just actions. A reasoning-grade audit record is the load-bearing primitive of the missing layer, and it looks something like this:

{
  "event_id": "refund-2026-05-17-08431",
  "triggered_by": {
    "human_principal": "rep:olivia.chen@firm.com",
    "delegated_via": "support-console-session-9c2a",
    "customer_principal": "cust:7741289"
  },
  "agent": {
    "identity": "refund-agent",
    "version": "v4.7.2",
    "policy_ref": "refund-policy/v3.1 (signed: r.patel, 2026-04-22)"
  },
  "task": "Process refund for order 88812204",
  "retrieved_context": [
    {"doc": "order:88812204", "fetched": "2026-05-17T08:43:11Z"},
    {"doc": "policy:refund-eligibility", "chunk": 4, "fetched": "2026-05-17T08:43:12Z"}
  ],
  "reasoning_trace": "...",
  "tool_calls": [
    {"tool": "check_eligibility", "input": "...", "output": "eligible"},
    {"tool": "issue_refund", "input": {"amount": 48.00}, "output": "ok"}
  ],
  "action": "refund:48.00",
  "principal_chain_hash": "0x9e7b3f..."
}

Not every agent needs this. A scheduling agent that proposes meeting times doesn’t. An agent that moves money, deploys code, or makes decisions that a regulator will eventually ask about does need it, and that’s the right bar to set because of the associated cost. Reasoning-grade audit is closer to a flight-data recorder than a syslog feed. The data is expensive to store and to query, with real privacy implications since those logs contain everything the agent saw, including data the agent was authorized to read but the audit system wasn’t supposed to keep. You afford it with proportional retention: full reasoning capture for high-blast-radius agents (regulator-facing, customer-funded, contractually material, production-modifying) and lighter capture for internal-only assistants.

Which raises the question the architecture diagram doesn’t ask: Who builds and runs this? Security can enforce policy but can’t author it. The people who know what a refund agent should be allowed to do own the refund business, not the firewall. IT can provision identities but can’t draft “good standing” or write the escalation rule. The MCP and A2A protocol communities are doing real work on wire-level identity and delegation. MCP gives you tool-invocation provenance and is the standard Entra Agent ID and most vendor frameworks build on. A2A is converging on cross-agent delegation primitives. Both matter, but neither drafts policy. Standards, not the institution, move the connectors.

What enterprises need is a new function that sits between the business units owning the policies and the platform teams running the runtime. Call it agent operations: small group, often four to eight people in a Global 2000 enterprise, embedded rather than centralized, reporting into the CIO or CISO depending on house politics, with explicit charter to maintain a registry of every production agent, its named human owner, its versioned authority specification, its retention policy for reasoning-grade audit, and its lifecycle state. Each agent gets onboarded with a signed policy, reviewed on a real cadence, and actually retired when its initiative ends, rather than the current default of quietly outliving its sponsors. Designing against failure modes like review cadences that calcify into ceremony, policy artifacts that lag agent deployment velocity, or functions that become the place agents go to die in committee is itself part of the work. The function has to ship at the pace of the platform teams or it will be routed around within a quarter.

The work is hard. It’s also overdue, and the regulatory clock is running. The EU AI Act’s high-risk provisions are entering enforcement this year, and regulators will ask for explainability, traceability, lifecycle records, and named human accountability. These are exactly the artifacts an agent operations function produces. Tyler Akidau called this the missing HR layer in his April Radar piece; Artur Huk’s more recent “From Capabilities to Responsibilities” converges on similar ground from the runtime side. The label matters less than the work. This piece is about governance inside one organization. The harder problem is governance across organizations, with agents acting under different trust regimes. That’s strictly worse, and worth its own piece.

Within your own four walls, the diagnostic is doable in an afternoon. Pick one production agent. Try to answer, with evidence: Whose authority does it carry, traced from action back to a named human? Where is its authority specified, and who signed the current version? When it does something wrong tomorrow, who pays, how is that decided, and what reasoning-grade record supports the decision? Most architects who do this honestly come away with three blanks and a knot in their stomach. That’s principal drift, named and visible.

The mesh you’ve built is real and necessary, but it isn’t sufficient. The rest of the architecture is the institution above it: the registry, the signed policies, the reasoning-grade audit, the named human at the end of every chain. In most enterprises it doesn’t yet exist, and it won’t arrive by buying another platform. You’ll have to draft it yourself.

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