The question worth asking about AAuth is not only whether the protocol is good. Kerberos won because of everything around the protocol: SSPI and GSS-API hid the mechanism from application developers, the LSA owned keys and ticket lifecycle, machine accounts existed as a side effect of domain join, Active Directory shipped the KDC by default, and SPNEGO made rollout incremental. Mapping that stack onto agents names the first control point in this series: the provider seam through which a harness or gateway acquires and presents credentials without exposing the mechanism to agent logic. MCP clients, SPIFFE, cloud identity systems, vendor brokers, and HTTP message-signature negotiation supply pieces, but no general seam composes them. That seam still cannot decide whose agent is running, which work is approved, or whether a resource permits one action. Those are separate records and decisions.
Agent runtimes naturally create the first trustworthy evidence about an instance, which gives them the default position in agent identity. Runtime proof and enterprise binding are still separate jobs. In heterogeneous enterprises, a binding layer can map evidence from many runtimes into durable Agent and Agent Deployment records and supply that governed context to credential issuers and resources. It is a real control plane only if the enterprise state survives changing runtimes. In the open world, model-provider harnesses are better positioned to integrate the stack because they hold the user relationship and execution loop. Distribution determines the default. Standard seams determine whether it can be challenged. Even a won binding layer answers whose agent is running, not whether its current work remains approved. That requires the third control point, an approved-task record with its own lifecycle.
Agent task authority is scattered across four de facto records: harness permission prompts, OAuth grants, IAM roles, and change tickets. Each performs a real job, but none is a general, portable system of record for approved work. An action click is not task approval, a grant is not a task lifecycle, and an identity role is not a reason for one undertaking. The missing object is an approved-task record with its own owner, bounds, lifecycle, and evidence relationships. Existing standards provide much of the transport for structured requests, user interaction, decisions, and credential projection. They do not yet supply shared task semantics, lifecycle propagation, trust, or enforcement behavior. Four plays are competing to mint the record, and the contest turns on distribution, durable state, and resource acceptance.
The control-points series argues that distribution determines defaults and standard seams determine whether those defaults remain contestable. MCP adds the clock. It launched with a specification, SDKs, a distributed host, and reference servers, and one developer could run the whole loop before the ecosystem coordinated. Mature authorization and governance followed the adoption pressure. The lesson is not that ratification is obsolete or that protocols can be adopted unilaterally. It is that a seam needs a small first coordination radius, immediate utility, low exposed implementation cost, running code, and a path from one controlled deployment to multilateral interoperability. This essay runs the series’ seam table through that test, uses AAuth as the clean-sheet stress test, and explains what would produce an enterprise ‘SAML moment’ for agents.
Cross App Access is not twenty-five generally available integrations. It is three different things at three different stages: a stable MCP authorization extension, a live Claude and Okta beta, and a partner graph whose broader product rollout is still under way. That distinction makes the strategic result clearer. The launch coalition moves protocol coordination from each buyer to the vendors assembling the loop, giving the layered identity play an adoption wedge. ID-JAG carries both the enterprise user and a required OAuth client identifier, while the resource authorization server retains the final decision. What it does not standardize is the binding from that client to a logical Agent, approved deployment, or runtime instance, nor a record of the task that justifies access. The credential-projection foothold shipped. The Agent and approved-work records remain open.
Long-running agents discover mid-task that they need a destination their egress proxy does not allow, and the block comes back as an opaque connection failure with no machine-actionable way to ask for access and no human standing by. That block is a requestable denial, and the egress proxy is a policy enforcement point. RFC 8908, the Captive Portal API, supplies the recovery state machine for a blocked client on a network: discover captivity, learn the remediation endpoint, and retry after policy changes. A headless agent can use that state machine, with the denial carried by Proxy-Status and Problem Details where an HTTP response exists and by an authenticated side-channel status API where it does not. The recovery can ride the captive portal at two altitudes, destination-level on a proposed AuthZEN Access Request profile or operation-level on AAuth and Mission-bound authority. When the client already speaks AAuth, it needs no captive-portal shim at all, because AAuth carries the refusal and re-authorization in-band at the same request boundary the proxy already enforces.
The Four Questions of Delegated Work, and the Invariants That Compose Their Answers
Delegated work forces four separate continuity questions: request provenance, identity attribution, target-applicable authority, and continuing work justification. Their answers compose through a common boundary contract: authoritative sources, bound and correlated evidence, explicit lifecycle semantics, local decisions, and declared failure behavior. Current proposals fill different parts of that contract; narrow profiles adopted one boundary at a time offer a more credible path than one universal delegation artifact.
A Vocabulary, a Rubric, and a Living Map for the Four Questions
Continuity Is Not One Thing argues that delegated work poses four independently governed continuity questions. This companion carries the parts built to be revised rather than to last: a vocabulary that separates facts from evidence, artifacts, authorities, decisions, and state; a twelve-question rubric a working group can apply to any proposal without accepting anyone’s architecture; worked evaluations of Transaction Tokens and Identity Chaining; the sixteen active OAuth working-group documents classified against the framing; and the two-layer standards map with dated versions and statuses.
The handbook’s vocabulary in one lookup table, A to Z: the objects, the artifacts, the mechanisms, the roles, and the named constructs, each defined in one to three sentences with a link to its canonical home. The entries are written to be quoted. The canonical homes carry the argument.
OAuth, WIMSE, and OpenID, Mapped to the Architecture
The Mission is the architecture’s new primitive. The rest should compose. This appendix tests that claim against the ratified OAuth substrate, the complete active OAuth and WIMSE working-group queues, selected individual drafts, and the relevant OpenID Foundation specifications. It separates publication status from architectural relationship and states the important deltas and substitution hazards plainly.
The handbook argues the architecture. This appendix shows the bytes: a Mission Intent submitted through PAR, the approved record’s integrity anchors, a Mission-bound access token, an AuthZEN permit bound to parameters, a parameter_violation denial, the revocation that ends the task, the lifecycle event that announces it, and the status check that fails the 02:00 resume. Every exhibit follows the current editor’s copies, and the two integrity anchors reproduce byte for byte.
Mission-based authorization governs the approved task, not just the credential, session, or request. This page is the field reference: the definition and litmus test for what counts as mission-based, a competitive landscape, the adoption stages, threats and non-goals, the canonical diagram and glossary, and the Q3 board-packet example threaded through the handbook.
The least-privilege MCP series ends on a gap: token-side and resource-side authorization both work per call, and neither names the task the user approved. This essay applies Mission-Bound Authorization at the MCP boundary. The Mission is the durable approved task, tokens and PDP decisions are projections of it, tool discovery and invocation and approval line up against it, expansion routes through a fresh approval, and audit joins on one identifier. A denial is traced end to end to show the whole spine working.
Authorization looks the way it does because each generation solved the question its era made urgent, and deferred one question that someone else was always carrying: what approved work is this, and is it still on? Purpose was not absent. A second stack of tickets, purchase orders, workflows, and approval systems held it locally, and people carried it between systems. UMA decoupled protected-resource access from synchronous resource-owner interaction, and workload identity made software actors attributable without making their credentials task-specific. What never became a standard cross-boundary object was the approved undertaking itself, with authority derived from it and a lifecycle independent of any credential. Usage control identified ongoing authorization two decades ago. Unattended work now removes the human carrier and makes shared task state an operational requirement. This is the history that makes the Mission a legible next step rather than an idea from nowhere.
The handbook closes on judgment. First the strongest outside evidence: AAuth, the proposed clean-slate agent protocol, adopted a first-class mission layer in its 01 revision after this model’s AAuth mapping circulated: not independent replication, adoption by a designer free to say no, which is its own kind of proof. Then the honest bets: admission grain, issuer home, the price of Termination, the necessity of the object itself, the portability of its authority, and the classification line, each stated with the evidence that would falsify it. The laws and the claim gate are the invariants. The bets are the wagers, and deployment experience, not this handbook, will settle them.
Issuance gating and runtime enforcement are two independent chokepoints, strictly stronger together: a gap in PEP coverage is still bounded at the token layer, and an outstanding token is still stopped at the action layer. The Mission Authority Server, the issuance grant, the Mandate, and Cross-Domain Projection extend the pattern space. And the structural reading that platform engineers reach for unprompted: the layer is the control plane for delegated authority, mapped concept by concept from desired state to the fleet API, with the disciplines that keep the framing honest.
OAuth is the flagship binding because it is deployment reality, but the model does not depend on it. This part states the framework the profiles realize: four functions (compilation, projection, containment, continuity), a verb spine of ten verbs from propose to analyze, and the fundamental-versus-accidental test. Which ideas survive if OAuth disappears? Nearly all of them: the layer, the laws, the vocabulary, the approved task with an integrity-anchored record, approval evidence, runtime containment. What is accidental is the realization: PAR, RAR, the claim names, the wire shapes.
The standards community is converging on a problem statement: agents break OAuth’s pre-approval paradigm, tokens cannot represent delegation chains, revocation cannot reach a task, and consent screens cannot survive a thousand scopes. The agent authorization use-case catalog names nine scenarios and rolls its analysis up to five major gaps, and this part answers the catalog line by line at both grains with machinery that existed before it was published: task-level revocation is the Mission kill switch, bulk revocation is Mission Management, multi-hop chains are act chains and Child Missions, scope explosion dies at Mission-grain consent, and the paradigm mismatch is the discovery loop. One answer is partial and one is delegated, and the tally is stated rather than smoothed.
The first five layers make the Mission approvable, enforceable, governable, and delegable. This operational close makes them hold up against a real agent: a harness that treats session continuity as recoverable state and not as authority, an orchestrator that unwinds work already in flight when a Mission stops, and a transparency profile that makes the suite’s evidence independently verifiable across trust domains. It closes with a synthesis of the six operational layers and the Mission Assurance Levels, the practice-side view of the adoption path the architecture chapter stages.
The issuance core gives a Mission three states and gates derivation on active. This part adds the surfaces that make state actionable over time: Status for canonical pull freshness with Signals as its push complement, Expansion for governed growth, and Completion for monotonic narrowing. One rule threads through all four. Only active permits reliance, so every state a newer profile adds fails safe for a consumer that predates it.
OAuth issuance bounds what authority may exist. It does not check the action at the point of use, so an active Mission becomes ambient authority within a token’s lifetime. The runtime layer closes that gap. A PEP at each consequential execution boundary obtains a permit from a PDP that evaluates the action, its parameters, the actor, and the current Mission state before any consequential effect occurs. The runtime profile fixes the invariants. The AuthZEN profile is its concrete wire binding.
The AI agent auth best practices give an agent workload identity, credentials, and delegated user authority. This part binds Mission authority to that identity. The mission claim projects the approved task into every derived token, attested instance identifiers and actor chains keep every actor attributable, and delegated work gets explicit, narrower, separately revocable authority. A sub-agent that acts because it descends from a parent session is inheriting ambient authority, not delegated authority. Child Missions give durable sub-agents their own revocable handles with strict-subset authority and cascade revocation. Offline attenuation, the experimental roadmap for fan-out at scale, keeps the Authorization Server off the hot path with the runtime state check as the surviving kill switch.
A user request is untrusted input. This part covers the integrity of the approval event, the layer before any token exists: the client-side shaper that proposes a candidate Mission Intent, the Consent Evidence that commits the structured consent disclosure the Authorization Server recorded as rendered (not the pixels or the Approver’s comprehension), and the deferred and revisable approval that lets a human reviewer narrow a proposal in place. Authority is created only when the Authorization Server validates, narrows, and approves.
A definitive architecture that ends without a build order is a tour, not a blueprint. Most estates start at the read-only ceiling: agents capped at read access, humans approving or executing the writes, and pilots that never graduate. This closer names what that posture costs and stages the way off it: crawl by shipping the issuance core (approved, integrity-anchored Missions and a possession-independent kill switch, honestly labeled governance rather than safety), walk by adding the Runtime-Enforced level (per-action enforcement, the AuthZEN binding, and Status freshness, all on substrate that already shipped), and run by climbing to the Governed and High-Assurance Agent levels, each of which makes a broader class of write authority defensible. Plus the ecosystem to compose with, the five operational surfaces you will own, and the pieces the community still has to standardize.
The AI agent auth best-practices draft names the Mission and declares its translation into authorization out of scope. This is the core argument on the other side of that line: why the approved task is the missing object above authentication and instance identity, how the argument converged, the Mission-versus-Intent boundary, and where to start. The definitions, object model, lifecycle, and glossary live in the Reference.
What the Corporate Card Already Solved walked a working delegated-authority architecture one control at a time and never mentioned a protocol. This part is the joint between that mental model and this chapter’s architecture. The five rules the card world taught become the five laws of delegated authority, stated for any substrate. The corporate-card test becomes the claim gate a vendor claim must pass. And the build lists that closed each card post, the things the agent stack cannot borrow from the expense world, turn out to enumerate the draft family: disclosure integrity, field-speed narrowing, checkpoints per boundary, endings that propagate, and a record that earns trust without a bank.
Nobody hands a new hire the company checkbook. In a mature spend program, they get an instrument bound to an approved purpose, checked at each transaction, metered against a budget, and frozen when the reason for the spend goes away. Agent credentials today are blank checks with expiry dates. This part walks the expense-governance loop end to end, maps each control onto agent authority, and is honest about the five places the analogy breaks. Each break is something the agent stack still has to build.
Re-subjecting across a SaaS boundary is a mint, not an attenuation, so the IdP must issue each onward grant. ID-JAG covers the first hop, where an application holds the user’s ID Token or SAML assertion to exchange. Subsequent hops hold no end-user credential, which leaves a gap: the intermediate has nothing to present to the IdP to continue the chain. The Identity Continuation Assertion fills it. It is a short-lived, sender-constrained JWT, issued by a Chain Authority the IdP trusts, that carries opaque evidence of the in-flight delegation and is presented as the Token Exchange subject token to request an onward ID-JAG. It is evidence, not authority: it carries no subject and grants no access, the IdP resolves the target audience’s subject and re-decides at every hop, and the continuation handle never reaches a Resource Server.
Identity Assertion Trust Framework and Domain-Authorized Issuer Trust Method
Self-service agent sign-up exposes a first-contact trust problem: a Resource Authorization Server can verify a perfectly valid JWT and still not know whether the issuer is allowed to assert identities for the user’s domain. That is two questions, not one. Federation proves the issuer is authentic, but not that the namespace owner authorized it, and static allowlists do not scale to onboarding unknown domains at runtime. The Identity Assertion Trust Framework lets a Resource AS publish the evidence it requires. The Domain-Authorized Issuer Trust Method lets a domain owner publish which issuers may assert identities in its namespace, fail-closed, the way mail and the web already pushed authority into DNS. Both compose with ID-JAG and the JWT-bearer grant without changing the grant surface.
Part one laid out two ways to lock down a single tool call an agent makes through the Model Context Protocol: carry a narrow token, or let the resource decide each call. This part walks the standards that close the gaps. AuthZEN gives a standard way to ask the policy question, the Access Request and Approval Profile turns a denial into a governed request for approval, and a set of proposals carries that approval over the wire. Each makes one call’s authorization more interoperable, and none gives a multi-step task a shared identity. So a string of individually correct calls can still drift from what the user approved. The missing piece is a durable, governed record of the approved task, the object I call a Mission.
There are two natural ways to lock an agent’s Model Context Protocol (MCP) tool calls down to least privilege. The agent can carry a narrow token scoped to the action, or the server can decide each call as it happens. Carrying a token gives portable proof of what the agent may do, but pushes domain knowledge onto the authorization server and token management onto the client. Deciding at the resource keeps the meaning where it lives, but the decision is not portable. MCP makes the tool boundary first-class for both. This part compares the two models and how to choose. Part two covers the standards that close the per-call gaps and the task object neither names.
In Cross-App Access, a single signed-in user’s identity has to cross applications that each name them under a different subject. Workload identity proves which service is calling, not which user delegated the work, and offline attenuation can narrow authority it already holds but cannot create a binding to a name it was never given. So crossing a subject namespace is a mint, not an attenuation: only the IdP or broker that owns the mapping can issue new audience-scoped identity evidence, while the destination Authorization Server still applies its own policy and mints the access token. The same shape holds on the authorization axis, where a different scope or policy model forces a non-amplifying re-mint rather than a narrowing. The open question is not whether that mapping authority is in the loop but how it is invoked: caller-pushed continuation, resource-pulled resolution, or another profile that preserves the trust invariant.
Closed-world authorization treated denial as the end of the interaction. Agents, runtime discovery, delegation, and mission expansion turn denial into the beginning of governance escalation. The draft AuthZEN access request and approval profile standardizes that handoff without standardizing the workflow engines behind it. Client-Initiated Backchannel Authentication (CIBA) is not the answer because the problem is not authentication freshness. It is whether authority should continue under newly discovered runtime conditions.
OpenID Connect is mature, standardized, and widely deployed, but SAML remains the enterprise SSO default because it is familiar, explicit, and deeply embedded in procurement and operations. That familiarity now hides a harder problem: XML Signature complexity, aging implementation stacks, limited post-login integration, and post-quantum migration pressure make SAML difficult to defend as the long-term enterprise baseline. The industry needs a secure enterprise OIDC profile and a credible migration path that preserves identity contract continuity for existing SAML federations.
WorkOS auth.md is an agent-readable registration document for one-click setup, with Agent Verified, user-claimed, and anonymous paths. In the Agent Verified path, most pieces already exist across OAuth and OpenID standards: ID-JAG, OAuth metadata, dynamic client registration, standard token endpoints, and SSF/CAEP/OPC. The standards gap is a profile for runtime agent onboarding and trust establishment, not a new grant protocol.
Modern agent harnesses make work durable across restarts, devices, background jobs, and sub-agents. That durability is a runtime property, not a governance property. A session answers where the agent can continue working. A mission answers why the agent is allowed to keep working. Conflating them is a central failure mode of long-running autonomous agent systems.
Client instances are not new clients. They are actors. With the Actor Profile and the act chain already in place, and an instance_issuers field that fits any client registration channel (static, Dynamic Client Registration, or CIMD), treating instances as first-class actors needs no new grant type, no new client type, and no new claim. It needs a profile that ties them together.
Enterprise SaaS still defaults to app-by-app OAuth islands with their own clients, long-lived artifacts, and revocation paths. The architectural shift is OAuth federation: adopt issuer-mediated federation now for services and workloads, and adopt Cross-App Access (XAA) as the standards direction for user-delegated cross-app access.
The new version of AAuth (draft-hardt-aauth-protocol-01, since resubmitted as draft-hardt-oauth-aauth-protocol) materially changes the earlier comparison. Mission is now first-class in the protocol, with PS-mediated approval, mission-aware token choreography, and governance endpoints. The remaining gap is no longer whether Mission exists, but whether the published model is strong enough to support portable containment rather than just mission correlation and governance hooks.
ID-JAG, also often called Cross-App Access (XAA), is centered in the current draft on Enterprise IdP trust, but the issuer that matters is the immediate IdP the downstream authorization server already trusts for SSO and subject resolution, not necessarily the top-level workforce IdP. The same trust pattern can also extend architecturally to CIAM and platform identity layers that federate upstream workforce login while remaining authoritative for downstream product trust, tenant context, and subject resolution.
Open-world OAuth can improve discovery, resource binding, and first-contact trust. That still leaves the harder agent problem: how approved intent becomes bounded authority that stays governed across delegation chains, unfamiliar tools, consent expansion, revocation, and task termination.
OAuth was built for closed worlds, and that constraint is why it became mature. Agents expose the limits of that deployment model. This post traces what the newer OAuth standards get right and which substrate gaps still need to close.
The current split between token exchange semantics and JWT access token practice creates avoidable interoperability failures. A common profile for act, grounded in entity profiles, can align JWT assertion grant and JWT access token processing.
Mission-Bound OAuth is a serious attempt to govern delegated agent authority using existing OAuth infrastructure. This post takes the pessimistic view: it may be the wrong answer because it asks the authorization server to become a governance engine, a lifecycle controller, and a mission ledger all at once. A cleaner alternative is to treat Mission as a separate authority service and let OAuth be one projection of that model rather than its home.
Mission-Bound OAuth argues for a durable Mission object that governs delegated authority across approval, lifecycle, delegation, and termination. This follow-up asks whether Dick Hardt’s AAuth draft is a better protocol substrate for the same model, and where AAuth still appears to need an explicit Mission-like authority object.
Rich Authorization Requests are the natural first instinct for agent missions, but audience-bound access tokens and uneven cross-domain interoperability limit how far they can carry a governed task. Mission-Bound OAuth solves that by making the Mission a durable authority object at the authorization server. This post explores the authentication-layer companion profile: OpenID Connect Client Context carries purpose and approval input when the user is present, and ID-JAG carries reduced Mission projections across same-IdP trust domains.
OAuth answers whether a request is permitted right now. Mission-Bound OAuth asks whether a delegated mission should still be running at all. This RFC proposes a durable Mission object at the Authorization Server that governs token derivation, lifecycle, delegation, and termination across agent execution.
Enterprise IAM was designed for human-paced execution. Agents remove the presence, pacing, and natural scope-limiting that made those controls work. The result is a structural gap that stronger credentials, tighter scopes, and faster JIT provisioning cannot close.
Tokens, credentials, and scopes tell a system what an agent may do. They say nothing about why execution was authorized or when it should end. The Execution Mandate is the primitive that closes that gap: a signed, inspectable authority record that runtime systems can evaluate and revoke throughout the execution lifecycle.