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kieran@kierans.net

sec WIMSE AI agents delegation OAuth WIMSE capability Autonomous AI agents increasingly require access to protected resources across multiple service providers on behalf of human users. Existing OAuth 2.0 extensions address individual aspects of this problem (token exchange, proof-of-possession, and structured authorization) but no current specification defines how these mechanisms compose into a coherent credential delegation framework for AI agents. This document specifies the Credential Delegation Protocol: a profile of OAuth 2.0 Token Exchange (RFC 8693), Demonstrating Proof-of-Possession (RFC 9449), Rich Authorization Requests (RFC 9396), and Client-Initiated Backchannel Authentication (OpenID Connect CIBA) that enables human users to delegate scoped, attenuated credentials to AI agents operating across heterogeneous service providers. The protocol defines: agent identity lifecycle management using ephemeral key pairs; capability-shaped delegation tokens bound to specific operations and resources; credential wrapping semantics that prevent exposure of underlying OAuth tokens to agents; consent-gated delegation flows for asynchronous agents; real-time cascading revocation; and tamper-evident audit chains. This document does not define new token formats, new OAuth grant types, or modifications to existing authorization server behavior. It specifies how existing mechanisms are combined to achieve secure, auditable credential delegation for AI agents. Status information for this document may be found at . Discussion of this document takes place on the Workload Identity in Multi System Environments (WIMSE) Working Group mailing list (), which is archived at . Subscribe at . Source for this draft and an issue tracker can be found at .

Introduction

Problem Statement OAuth 2.0 solved human-to-service authorization. When a user authorizes an application to act on their behalf, the application receives an access token representing that delegation. This model assumes a human present at a browser for the consent ceremony. AI agents operate autonomously. They are ephemeral (spawned on demand), numerous (many agents per user per service), and adversarially promptable: a compromised prompt can direct an agent to misuse any credential it holds. Existing standards fail the agent delegation use case in seven specific ways: No agent identity primitive. OAuth clients require pre-registration. Agents are ephemeral and cannot register at instantiation time. SPIFFE requires admin provisioning. No standard defines bootstrapping an agent identity from nothing. No delegation chain attenuation. When Agent A sub-delegates to Agent B, existing standards do not enforce that authority can only narrow. RFC 8693 records delegation chains via nested act claims but treats them as "informational only": no enforcement, no structural guarantee. The delegation chain splicing vulnerability (disclosed to the OAuth WG mailing list, February 26, 2026 ) demonstrates that Sections 2.1-2.2 of permit a compromised intermediary to present mismatched subject_token and actor_token from different delegation contexts, producing a properly-signed token asserting a delegation chain that never occurred. No credential wrapping. Agents need to use credentials at resource servers that do not understand delegation. No standard defines how a delegation token authorizes credential exercise without exposing the raw credential to the agent. No granular authorization. OAuth scopes are coarse string identifiers. Agents need resource- and operation-level capability binding: not "can access Google Drive" but "can read file X in folder Y until time T." RFC 9396 provides the structural mechanism but no agent-specific vocabulary or attenuation rules. No synchronous revocation cascade. Revoking a root delegation must immediately invalidate all derived delegations. UCAN revocation is gossip-based. RFC 8693 explicitly defers revocation to implementations. No existing standard provides sub-second cascading revocation for a delegation tree. No asynchronous consent. Agent-initiated flows require user approval without a redirect URI. CIBA provides the mechanism but is not profiled for agent delegation scenarios, and CIBA + DPoP interaction is underspecified. No delegation audit chain. No standard defines an immutable, portable audit trail for "Agent A used User B's credential C to perform operation D at time T via delegation chain E." This document profiles existing standards to address all seven gaps.

Relationship to Existing Work The IETF landscape for agent authorization moved quickly during 2026. The OAuth Working Group was rechartered in June 2026 with agents acting on behalf of users explicitly in scope. The WIMSE Working Group held an interim meeting on June 3, 2026 dedicated to AI agent authentication and authorization and has since adopted that work as AIMS. Several dozen individual drafts now address some slice of agent identity or delegation. This section positions this protocol against the working group documents and the individual drafts closest to its mechanics. It is not a survey.

Frameworks and Working Group Documents draft-ietf-wimse-aims (): AI Identity Management System, a framework for AI agent authentication and authorization, adopted by WIMSE and published as draft-ietf-wimse-aims-00. The framework identifies the need for concrete delegation mechanics and defers them to OAuth flows. This document supplies those mechanics and is designed as a companion, not a replacement. draft-ietf-wimse-arch (): Defines the trust domain model and terminology assumed here for WIMSE deployments. The Delegation Server is a service within a trust domain, and Agent identities established per are compatible with WIMSE workload identifiers. draft-ietf-wimse-wpt (): Defines the Workload Proof Token (WPT), a proof-of-possession mechanism for workloads. This protocol binds Delegation Tokens with DPoP instead: DTs are exercised over plain HTTP by ephemeral agents that may sit outside any WIMSE trust domain, the deployment shape DPoP already serves. A future revision may profile WPT for DS-to-resource-server hops inside WIMSE trust domains. draft-ni-wimse-ai-agent-identity (): Addresses agent identity within WIMSE. The did:key model used here is compatible. This document adds credential wrapping, revocation, consent gating, and chain verification. draft-reece-wimse-cross-org-delegation (): A problem statement and requirements catalogue for cross-organizational delegation, used on the WIMSE list as a common frame for evaluating delegation proposals. A future revision of this document will map the protocol against those requirements.

Delegation Chain Mechanics draft-ietf-oauth-identity-chaining (): In the RFC Editor queue at -17. Chains identity and authorization across trust domains by exchanging a token in one domain for a JWT assertion accepted in another. It preserves identity across hops but does not constrain what each hop may do. This protocol adds structural attenuation and receipt-based chain verification on the same RFC 8693 substrate. The two compose. draft-niyikiza-oauth-attenuating-agent-tokens (): Defines tokens a holder can attenuate offline. Same goal as , different trust model: AAT verification relies on the root issuer key and offline derivation, while this protocol keeps the Delegation Server in the loop at every hop in exchange for synchronous revocation () and server-checked strict-subset validation. draft-asor-wimse-agent-delegation-chain (): Defines an offline-verifiable Delegation Chain of RFC 9068 JWTs, each committing to its parent's signing input by hash, carrying authority as exactly one RFC 9396 agent_delegation detail with a three-form scope grammar (literal, wildcard, and opaque provider-issued scopes, Section 4.1 of that draft) and a typed constraint vocabulary (Section 4.2), naming the principal in sub and the acting agent in client_id at every hop, and verified by a deterministic algorithm with no call to an authorization server. This protocol is the server-side counterpart: the Delegation Server is in the loop at every hop and holds the credentials, so revocation is synchronous and aggregate budgets have a single writer, while a receipt chain verified offline still proves scope narrowing, depth, linkage, expiry ordering, and, with , ceiling narrowing. That draft describes the two as halves of one design separated by whether a server is in the path, and points deployments that need synchronous cascading revocation or shared aggregate accounting to the Delegation Server defined here (Sections 8 and 9.4 of that draft). The two share the scope grammar, the constraint vocabulary, the subsumption rules, and the sub/client_id split, so one subsumption implementation serves both. The tokens the DS verifies itself use a different wire format: carries scopes and constraints inside a single closed agent_delegation detail and rejects any other detail type, while this document's Delegation Tokens carry cred_delegation capabilities and a separate delegation_constraints claim. For tokens meant to be verified away from the DS, including tokens a user mints with no DS involved, adopts the format unchanged, so a custody server and an offline verifier read the authority those tokens carry in one vocabulary. Cred's reference implementation is run against the Asor interop vectors; gives the results, the commits they were taken at, what each vector set covers, and the failures and gaps. This document cites -03 (27 October 2026). -03 leaves the -02 token format unchanged, keeps all thirty-five -02 vectors and adds one (reject_child_adds_detail_type), and requires now < exp at step 5 of its verification algorithm, as the JWT exp claim does; -02 admitted now = exp. It also stops requesting registration of del_depth, del_max_depth, and par_hash, which requests with a different definition of del_max_depth; a token under carries those claims as defines them. draft-gco-oauth-delegate-sd-jwt (; the OAuth WG adopted it on 16 October 2026, and the WG -00 had not been posted at the time of writing): Delegates SD-JWT credentials holder-to-holder by allowing a Key Binding JWT to act as an SD-JWT. It operates at the credential format layer; this protocol operates at the delegation service layer. A DS could issue capability attestations as Delegate SD-JWTs without changing the mechanics defined here. Comments in the adoption call identified what the format layer leaves open: a delegate payload may add claims with no rule against widening a predecessor's, a delegation's lifetime is not bounded by its predecessor's, and depth and no-further-delegation limits are undefined. Those are the chain rules of , which a holder-signed profile would need to state in its own terms. draft-zhu-oauth-async-delegation (): Defines delegated refresh tokens so agents can act while the user is offline. This protocol answers the same need by keeping refresh tokens in the Credential Vault and giving agents only short-lived DTs. The two are alternative positions on whether agents may hold long-lived credentials at all. draft-oauth-ai-agents-on-behalf-of-user (; expired February 2026): Introduced requested_actor and actor_token parameters binding the acting agent into the authorization code exchange. That closes the same actor-binding weakness this protocol closes with prf receipts, but only for the first hop and only at the authorization server. See .

Credential Intermediation draft-hartman-credential-broker-4-agents (; expired): Specifies a credential vaulting broker that mediates agent API access through short-lived, narrowly scoped proxy credentials. Architecturally the closest work to the Delegation Server and Credential Vault defined here. CB4A defines the broker; this document additionally defines the delegation chain (attenuation, receipts, sub-delegation), the consent flow, and the revocation cascade such a broker must enforce. draft-araut-oauth-transaction-tokens-for-agents (): Extends transaction tokens to carry agent context in the act claim for intra-domain call chains. Complementary: transaction tokens propagate context within a domain after authorization exists; this protocol governs how the authorization comes to exist. draft-schwenkschuster-wimse-credential-exchange (; expired): Despite the similar name, addresses a workload exchanging its own credential for a different format or trust domain. This document addresses human-to-agent delegation over stored credentials that are never issued to the requesting party.

Consent, Mandates, and Audit Evidence draft-yossif-agent-mandate-problem (): A problem statement on verifiable human mandates: intent authorized at one time, executed autonomously later. The consent records () and capability constraints defined here are a concrete answer to part of that problem space. draft-nelson-agent-delegation-receipts (): Defines a delegation receipt recording what an agent may do, for how long, and under what instructions, with scope attenuation rules for multi-agent chains and a revocation registry with cascade semantics. The root receipt is signed by the authorizing human principal's key. A sub-receipt is signed by the parent's delegatee: the parent's optional delegateeKey must match the sub-receipt's signing key, compared as JWK thumbprints , and a receipt without delegateeKey is terminal. The prf receipts in are DS-signed and bind hops within a chain; Nelson's root receipt is principal-signed and binds the principal's instruction to the agent's run. They answer different trust questions and can coexist. Section 4.6 of that draft states that custody of the signing key is attested by the deployment out of band and cannot be shown from the receipt bytes. Consistent with that, a principal-signed root receipt adds assurance beyond a server-signed one where the deployment attests that the principal's key is held by the user and the user verifies what it signs; a key the operator holds or can export proves no more than the operator's own signature. A sub-receipt carries the assurance of the delegatee key that signed it, not the principal's. draft-nennemann-wimse-ect (; expired): Execution Context Tokens define an audit record format. This protocol's audit chain is designed to be ECT-compatible. draft-goswami-agentic-jwt (): Describes agent checksums and workflow-aware intent binding. This document does not define an agent checksum or intent-binding claim.

Design Principles Compose, don't invent. Every mechanism reuses an existing standard. New concepts appear only where the gaps identified in are confirmed. Attenuation is structural. Agents cannot widen authority at any delegation hop. This is enforced by the Delegation Server, not by trusting agents. Inspired by UCAN attenuation semantics and the object-capability model . Credentials are never possessed. Agents receive and exercise delegated authority through the Delegation Server. Raw credentials never cross the boundary to the agent host: the underlying credential is never delivered to the Agent, so an Agent turned into a confused deputy cannot leak it. This does not protect the credential at the DS itself (). Revocation is synchronous. A user revoking delegation takes effect within the SLA defined in . Eventual consistency is not acceptable for credential revocation in adversarially-promptable systems. Capability-shaped, not identity-scoped. Delegation tokens authorize specific operations on specific resources with specific constraints, not "Agent X can access Service Y." Follows the NORA (designation = authority) principle from capability security. Chain integrity is cryptographic. Each delegation hop produces a signed receipt. The chain is verifiable end-to-end without trusting intermediate agents, addressing the RFC 8693 delegation chain splicing vulnerability.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Delegation Server (DS):

A service that issues, manages, and revokes Delegation Tokens on behalf of Subjects. The DS maintains the Credential Vault and enforces delegation policies. It acts as an intermediary between Agents and upstream OAuth authorization servers.

Agent:

An autonomous software entity that performs actions on behalf of a Subject across one or more service providers. An Agent authenticates to the DS using an ephemeral key pair and receives Delegation Tokens authorizing specific operations. An Agent MUST NOT possess or have access to the underlying credentials stored in the Credential Vault.

Subject:

The human user who authorizes credential delegation. The Subject authenticates to the DS, deposits credentials into the Credential Vault, defines delegation policies, and approves or denies consent-gated delegation requests.

Delegation Token (DT):

A signed JWT issued by the DS that authorizes an Agent to perform specified operations on specified resources via the DS. A DT contains capability claims structured per , a DPoP key binding for proof-of-possession verification, and an opaque credential handle. Delegation Tokens MUST NOT contain raw OAuth tokens or credentials.

Credential Vault:

Server-side secure storage maintained by the DS that holds OAuth tokens and credentials deposited by Subjects. Credentials are referenced by opaque handles and exercised exclusively by the DS on behalf of Agents presenting valid Delegation Tokens.

Capability:

A structured authorization grant specifying a permitted operation, a target resource, and optional constraints (time bounds, rate limits, argument restrictions). Expressed using the authorization_details object defined in and bound to a specific Delegation Token.

Attenuation:

The process by which a Capability is further constrained when delegated from one entity to another. An attenuated Capability MUST be a strict subset of its parent. Authority can only narrow at each delegation hop; it can never widen.

Delegation Chain:

An ordered sequence of Delegation Tokens from Subject to Agent_1 to Agent_2 ... to Agent_N, where each link attenuates the authority of the previous. The chain is verifiable from any link back to the root consent event via signed delegation receipts.

Credential Exercise:

The act of the DS using a stored credential on behalf of an Agent. The Agent presents a valid DT and DPoP proof to the DS, which validates the DT, retrieves the credential from the Vault, calls the resource server, and returns only the API response.

Architecture Overview

Retrieves cred -> Calls RS | | | | Returns API response (never raw credential) | | | +----------------------------------------------+ | | | | +----------------------------------------------+ | | | Revocation & Audit | | | | Synchronous cascade | Tamper-evident log | | | +----------------------------------------------+ | +--------------------------+---------------------------+ | v +------------------------------------------------------+ | AGENT | | | | 1. Generates ephemeral did:key | | 2. Authenticates via JWT Bearer (RFC 7523) | | 3. Requests delegation (capabilities + constraints) | | 4. Receives DT (DPoP-bound, capability-shaped) | | 5. Exercises credentials via DS /exercise endpoint | | 6. Sub-delegates via attenuation (optional) | | | | TRUST BOUNDARY: Agent sees DT + API responses only | | Agent NEVER sees: raw tokens, refresh tokens, keys | +------------------------------------------------------+ ]]>

Critical architectural property: The Agent's trust boundary extends only to the network interface of the Delegation Server. The Agent never crosses into the Vault. The underlying credential is never delivered to the Agent, so a compromised Agent cannot exfiltrate it. That property does not cover the DS itself (), upstream responses that reflect a credential or mint a new one, logs, or redirects, and least privilege at the upstream provider remains necessary.

Protocol Version Negotiation The canonical protocol version for this draft is 0.1.0. HTTP protocol clients MUST advertise the highest Cred Protocol version they support for a request using the Cred-Protocol-Version request header. The header value MUST be a single semantic-version string in MAJOR.MINOR.PATCH form. Delegation Servers MUST set Cred-Protocol-Version on every protocol response, including error responses, to the version selected by the server for that response. Each implementation MUST maintain: a supported-version set, ordered from newest to oldest a configured version floor, below which requests are rejected For this draft, the supported-version set is ["0.1.0"] and the default version floor is 0.1.0. A Delegation Server MUST reject a request that advertises a version lower than the configured floor or a version outside the supported-version set. The server MUST return HTTP 426 with a JSON body containing:

The response MUST also include Cred-Protocol-Version set to the server's current version so clients can distinguish protocol drift from authentication, authorization, or policy failures. During the 0.1.0 compatibility window, a missing Cred-Protocol-Version request header MAY be treated as 0.1.0. This allowance exists only because there is no earlier wire version to downgrade to. Implementations that raise the version floor above 0.1.0 MUST reject missing protocol-version headers with protocol_version_unsupported.

Agent Identity

Ephemeral Key Pairs An Agent MUST generate a key pair at instantiation for a signature algorithm the DS accepts. A DS MUST accept Ed25519 and P-256 and MAY accept ML-DSA where a did:key encoding for it is available to both parties. The DID is derived deterministically from the public key using the did:key method , a DID method conforming to . No pre-registration is required. The DS MUST NOT reject a DID it has not seen before. Every verifier in this protocol, including the DS when it re-verifies a parent chain (), MUST hold a local list of accepted signature algorithms and MUST reject an assertion, Delegation Token, or receipt signed with an algorithm not on that list, as in step 1 of Section 6 of . The alg header of the object under verification never selects the algorithm by itself.

Agent Authentication The Agent authenticates to the DS using a JWT Bearer assertion signed with the private key corresponding to its did:key. Required claims: Claim Value Notes iss Agent DID did:key:z... sub Agent DID Same as iss aud DS endpoint URL   iat Current time   exp iat + max 300s 5-minute maximum jti Unique nonce Prevents replay Optional claims: Claim Value Notes agent_model Model identifier Vendor-prefixed, e.g., "vendor:model-id" agent_operator Operator DID or URL Organization running the agent

Agent Lifecycle Agents SHOULD generate a new key pair per session. The DS MAY require Subject pre-authorization of specific agent DIDs or agent operators before issuing Delegation Tokens. When an agent terminates, the DS SHOULD invalidate any active Delegation Tokens bound to that agent's DPoP key within the revocation SLA.

Workload Authorization Grant Composition Workload Authorization Grant supplies the provisioning layer: a platform-signed RFC 7523 grant identifies a workload to an authorization server that trusts the platform. Its on-behalf-of delegation composition slot is addressed by this document's subject consent, capability attenuation, and signed delegation receipts; WAG does not supply those properties itself. A WAG assertion is presented to an authorization server's token endpoint, not to the DS. A WAG-provisioned workload therefore authenticates to the DS as any other Agent, per , and act.sub in its Delegation Tokens remains the Agent DID. The WAG Agent Identifier is source identity evidence about that Agent, not a replacement for its DID. When a deployment links the two, the DS records in the delegation receipt () the WAG assertion's issuer, the Agent Identifier, and, where several Platforms share one issuer identifier, the registration-distinguishing claim name and value described in Section 6.3 of draft-carleton-workload-authz-grant-01. Section 6.1 of that draft requires sub and jti to be interpreted only within the matched Platform registration, so the DS MUST NOT equate bare Agent Identifiers from different registrations, and a downstream verifier MUST have a trusted mapping from the recorded issuer and registration context to the actor identity; a platform-local identifier is not globally resolvable. The WAG identity travels only as this receipt evidence. It MUST NOT be carried inside act: act.sub names the Agent DID, and a platform-scoped identifier there would contradict client_id () and depend on a mapping the verifier may not hold. The WAG assertion is a bearer credential, and WAG leaves proof of possession open (Section 8 of that draft). The DS MUST NOT treat WAG-asserted identity as proof that the presenting party controls the workload's key; sender constraint comes from the Delegation Token's DPoP binding (). WAG actor identity MUST NOT be treated as user consent or as permission to re-delegate.

Delegation Token Format A Delegation Token is a DPoP-bound JWT issued by the Delegation Server.

Required Claims Claim Value Specification iss DS identifier   sub Subject identifier User on whose behalf delegation occurs client_id Agent DID Acting agent, per Section 2.2 and Section 10.3 act {"sub": "<Agent DID>"} Current actor plus prior-actor history, per RFC 8693, Section 4.1 authorization_details Capability array Per RFC 9396 delegation_constraints Ceiling array Per-key ceilings in the Section 4.2 shape; see . OPTIONAL on a root token; REQUIRED on a child whose parent carries any cnf {"jkt": "<DPoP thumbprint>"} Per RFC 9449 iat Issuance time   exp Expiry time Max 1 hour; 15 minutes RECOMMENDED jti Unique identifier   consent_id Consent record ID Traceable to root consent event credential_handle Opaque string References Vault entry; MUST NOT be the credential itself client_id and act.sub name the same current actor. client_id follows the adopted AIMS Section 10.3 convention (acting agent in client_id, delegating principal in sub); act adds the RFC 8693 history trail so a verifier can tell the current actor from prior actors without a second claim set. The two MUST agree; a token in which they differ is malformed. client_id keeps the meaning Section 2.2 takes from Section 4.3: the client that requested the token. The DS therefore issues a Delegation Token only to the agent it names. For a child token the receiving agent is the requester (), so the authenticated requester, client_id, and act.sub are one party at every hop.

Capability Structure Capabilities are expressed as RFC 9396 authorization_details objects:

The DS MUST validate that capabilities in a sub-delegation request are a subset of the parent DT's capabilities, equal or narrower, never wider. Validation is the DS's responsibility, not the requesting agent's. Numeric and enumerated bounds on how a capability may be exercised are not part of the capability object. They are carried in the token's delegation_constraints claim () so that a verifier holding only the chain can check that they narrow hop by hop.

Constraint Ceilings A Delegation Token MAY carry a delegation_constraints claim: an array of objects, each with a REQUIRED key naming the constrained dimension and exactly one typed constraint value. The shape and the type vocabulary are those of Section 4.2 of , so that a Cred receipt chain and an Asor Delegation Chain can be checked by the same subsumption code: max (number): the quantity MUST NOT exceed it. min (number): the quantity MUST NOT be less than it. one_of (array): the value MUST be a member. not_one_of (array): the value MUST NOT be a member. prefix (string): the value MUST have it as a prefix. rank (number or label): position in an ordered enumeration; the value's rank MUST NOT exceed the constraint's. A label-valued rank carries its enumeration in an order member, least to most permissive, as in Section 4.2. max_lifetime (number): the sum of the quantity over every exercise under the token MUST NOT exceed it. max_subtree (number): the sum of the quantity over every exercise under the token and its descendants MUST NOT exceed it.

Parsing is fail-closed. A constraint object is closed: its members are key, one type member, and any member that type defines (order for rank). An entry with no type member, more than one, any other member, a malformed value, or a (key, type) pair repeated within the array makes the whole claim malformed, and a token with a malformed delegation_constraints claim is invalid before any subsumption is evaluated. A constraint of a type the DS does not implement is not malformed for that reason alone; it is carried, and it is never treated as absent. A verifier that encounters an unknown constraint type MUST treat the action as denied (fail closed), never as unconstrained, as in Section 4.2 of . Subsumption follows Section 4.3 of : for every constraint in the parent, the child MUST carry a constraint under the same key and the same type whose admissible set is a subset of the parent's (max no greater, min no smaller, one_of a subset, not_one_of a superset, prefix extending the parent's prefix, rank no higher). A constraint present in the parent and absent from the child means the child is unbounded on that dimension, which is wider, and the DS MUST refuse to issue the child. The child MAY add constraints the parent does not carry. When a sub-delegation request omits delegation_constraints, the DS inherits the parent's ceilings into the child unchanged. A DS or verifier that does not implement the type of a constraint present in the parent cannot evaluate subsumption for it. It MUST treat the child as not subsumed unless the child carries a constraint with the same key and type whose JCS serialization is byte-identical to the parent's, and even then any exercise under that constraint is denied, as at step 8 of Section 6 of (outcome unknown_constraint in Table 2 of that draft). Two constraints with the same key and different types, such as a min and a max forming a range, are evaluated independently. A label-valued rank without order, or whose label is not a member of order, is malformed. A child's order MUST be identical to its parent's for the same key; a verifier reads the ordering from the token and needs no registry entry per key. max, min, one_of, not_one_of, prefix, and rank bound each exercise and are checked offline by any holder of the chain. max is per exercise only; a producer MUST NOT express a cumulative bound with it. The type, not the key, states whether a bound is per exercise or cumulative: a verifier gives a key name no meaning, so it cannot detect a max that its producer meant as a running total. A max on a quantity that exists only as a running count, such as a count of calls, bounds nothing, since each exercise contributes one; such a count is bounded with max_lifetime or max_subtree (Section 4.2 of ). The DS defines what quantity each key it issues measures, so it is the party that can enforce this: a DS MUST NOT issue a token, including a child requested in a sub-delegation, that carries a max on a key it meters as a running count. max_lifetime and max_subtree name cumulative bounds: a verifier holding only the chain checks that a child's cumulative bound is no wider than its parent's, but two holders of the same chain cannot both decrement a running total correctly without a shared writer. The DS is that writer (): it checks and debits the running total atomically when it authorizes an exercise, and it alone holds the total for every token it issued. The delegation_constraints claim carries the bound; the DS does the debit.

Delegation Chain Integrity To address the delegation chain splicing vulnerability in Sections 2.1-2.2 of , each delegation hop MUST produce a signed delegation receipt containing: the parent DT's jti, the child DT's jti, the delegating agent's DID, the receiving agent's DID, the root delegated subject (the outer sub), the attenuated capability set, and any source identity evidence recorded for the receiving agent (see ). The receipt is signed by the DS and included in the child DT as the prf claim (an array of receipt content identifiers). Chain verification traces prf links back to the root consent event. At every hop, the DS MUST re-verify the parent token and its signed receipt chain, including issuer trust, signatures, expiry, DPoP binding, and revocation state, before issuing a child. It MUST establish that the delegator currently holds the authority being delegated and is allowed to delegate it. Signed provenance alone does not establish either condition. If a required authority or freshness check cannot be completed, the DS MUST NOT issue or exercise the child on the basis of that unresolved input. Authority MUST narrow monotonically: the child's operations and resources MUST be contained in the parent's effective authority, and its constraint ceilings MUST subsume per . Containment is the per-hop admission check. Where independent policies constrain the same action, their intersection MUST be order-independent; an unrecognized or unevaluable constraint MUST NOT be silently discarded. A child's lifetime MUST NOT exceed the remaining lifetime of the parent or the applicable consent grant. For this on-behalf-of delegation profile, each child MUST preserve the root delegated subject in outer sub and name the receiving, current actor in act.sub. Prior actors MAY be represented using nested act as defined in RFC 8693 Section 4.1. Nested actors provide historical attribution only and MUST NOT be used independently to authorize an action. The DS's signed receipts MUST bind the subject and current actor attribution to the parent and child token identifiers and the effective capability set. Actor attribution is attested per hop, not re-derived downstream: each hop's receipt records the act value the DS verified at that hop together with the time it was verified, and a verifier reconstructing the chain composes those attestations rather than inferring a prior hop's actor from a later token. The act claim is the attribution carrier, not proof of authority or a replacement for signed receipts. The DS SHOULD keep, for each hop, an audit record distinct from the receipt that identifies the receipt links, the grant and policy inputs evaluated, their as-of times and validity horizons, the decision, and any failed or unresolved check with a reason. The shape of that record is deployment-defined; verifier-side companion work may standardize it. A verifier MUST have authenticated evidence sufficient to reconstruct the chain to root consent, including the per-hop authority narrowing and subject/actor bindings; raw upstream credentials need not be forwarded. A valid receipt chain does not establish that issuer standing or consent remains current. Required freshness and revocation checks remain separate from chain reconstruction.

Sub-Delegation Exchange A hop has two steps, so that the token is requested by the agent it names: Authorization. The delegating agent presents its Delegation Token with a DPoP proof, the receiving agent's DID, and the narrowed capabilities and constraints. The DS runs the checks of , assigns the child's jti, signs the delegation receipt naming both agents and that jti, and returns a single-use delegation grant bound to the receiving agent's DID, the receipt, and a short expiry. Issuance. The receiving agent authenticates as itself () and sends an token exchange request with the delegation grant as subject_token, its own assertion as actor_token, and a DPoP proof under its own key. The DS verifies that the authenticated client is the DID the grant names and that the grant is unused and unexpired, re-checks that the parent and its ancestors are unexpired and unrevoked, since issuance happens at this step (), then issues the child with the jti the receipt names and the capabilities and constraints authorized in step 1: sub the root subject, client_id and act.sub the receiving agent, the delegating agent in nested act, cnf bound to the receiving agent's key, and prf extended with the new receipt. A delegation grant is useless without the receiving agent's key. The DS MUST reject a second redemption of the same grant and MUST reject a token exchange whose authenticated client differs from the DID the grant names.

Chain-Verifiable Profile The Delegation Tokens defined above are verified by the DS that issued them, with its receipt chain. Some tokens must instead be verified by a party that is not that DS and holds only the chain: a resource server or another server checking authority offline, or any verifier handed a token a user minted directly with no DS involved. Such tokens use the Delegation Chain format of unchanged: exactly one authorization_details entry, of type agent_delegation, carrying scopes and constraints inside it, with sub naming the principal at every hop, client_id naming the acting agent, cnf, par_hash, del_depth, and del_max_depth as that draft defines them. This document does not redefine that format, and a token under this profile is checked with the algorithm of Section 6 of . Cumulative ceilings (max_lifetime, max_subtree, and any running spend total) are enforced only where a single writer holds the total, as the DS does in . A verifier away from the DS enforces the per-exercise ceilings and checks that a child's cumulative bounds are no wider than its parent's. It permits an action under a cumulative constraint only if it holds the running total that constraint is measured over, or a component that holds that total, such as the issuing DS, authorizes the action; otherwise it denies, as step 8 of Section 6 of requires. Separate verifiers that each see only some of the exercises do not between them hold the total. When a DS issues a token under this profile: The token MUST conform to . It MUST NOT carry a cred_delegation detail or a top-level delegation_constraints claim, since rejects any second detail. Its lifetime MUST NOT exceed 1 hour, the cap on a Delegation Token (). Each permitted operation on a resource is expressed as a scope string. Section 4.1 of classifies a scope as literal, wildcard, or opaque by its bytes, not by who issued it, so a provider-issued string such as crm.read is a literal scope that a parent's crm.* covers. The DS MUST choose each scope string so that, under that classification, it admits no more than the capability it maps. The mapping from the capability the DS holds to those scope strings is deployment-defined, and the DS MUST record it in the receipt for the hop. The DS signs a delegation receipt for the hop as in and records the token's jti in it. It does not add prf, consent_id, or credential_handle to the token, which does not define; the receipt chain held by the DS remains the evidence that ties the token to consent. The DS MAY accept at its exercise endpoint () a token it issued under this profile, resolving the credential and consent from the receipt recorded under the token's jti. When a DS is presented with a token under this profile that it did not issue, it MAY verify the token per Section 6 of and evaluate the authority it carries with the scope grammar and subsumption rules of . Verifying such a token does not make it the parent of a Delegation Token. This revision does not define how a DS accepts a token it did not issue as the root of its own chain, or how a chain continues from a DS-issued token into hops minted without a DS; that composition is left to a later revision.

Credential Wrapping

Exercise Flow The Agent presents a valid DT and DPoP proof to the DS's /exercise endpoint. The DS: Validates the DT signature and expiry, and checks that the DT is not revoked () Verifies the DPoP binding (htm, htu, nonce) Checks that the requested operation is within the DT's authorization_details and within its delegation_constraints, denying an exercise under a constraint of a type it does not implement, and checking and debiting any cumulative total atomically () Retrieves the credential from the Vault using the opaque credential_handle Performs the authorized API call against the resource server using the stored credential Returns only the API response The raw credential MUST NOT appear in any agent-facing response.

Proxy Semantics For resource servers that accept standard OAuth Bearer tokens: the DS acts as a reverse proxy, performing the actual API call with the stored credential. The Agent's HTTP request to /exercise specifies the operation and parameters; the DS maps these to the upstream API call.

Native Resource Server Support (Future) For resource servers that natively support this protocol: the DS performs RFC 8693 token exchange, issuing a scoped access token containing the DT's act claim and authorization_details for direct presentation at the resource server. This eliminates the proxy step for participating services. The lifetime of the exchanged access token MUST NOT exceed 1 hour () or the remaining lifetime of the DT it was exchanged for.

Revocation When a Subject revokes a delegation (root or any subtree node), the DS MUST: Invalidate the specified DT within 1 second Cascade revocation to all descendant DTs within 5 seconds Return HTTP 401 with error: delegation_revoked for any /exercise request using a revoked DT whose authority check () runs after the revocation takes effect; a call already dispatched when the revocation takes effect is not recalled (see below) Write an immutable revocation event to the audit log with a revocation_time claim Revocation endpoint: DELETE /delegation/{jti} The response MUST include a revoked_count field indicating the number of tokens invalidated in the cascade. revoked_count reports invalidation, not closure. It counts the Delegation Tokens the DS has marked revoked; it does not claim that no effect authorized under them can still commit. For calls the DS mediates (), the authority check and the upstream dispatch happen at the DS, so a revoked token starts no new call. An effect the resource server accepted before revocation and commits later is outside what the DS observes. Where the DS has exchanged a delegation for a token presented directly to a resource server (), the DS is off the call path: revocation of that path is partial until the exchanged token expires, unless the resource server checks authority when it commits. Tokens issued under are in the same position as exchanged tokens. A verifier that checks one offline learns of a revocation only through whatever status mechanism it consults, so the DS's bounds cover its own records and the calls it mediates, not an offline enforcement point that keeps honoring a revoked token, or a cached status, until the token expires. The DS re-checks revocation from its own records before issuing any token (), and a token it issues for use away from it lives at most 1 hour (); a child minted from such a token expires no later than its parent. An enforcement point off the DS's call path therefore admits no new action under a revoked delegation after the expiry of the token presented, at most 1 hour after the DS issued it; one that checks status at admission stops sooner. This bounds the admission of new actions, not the completion of actions already admitted. Synchronous cascading revocation holds within one Delegation Server. It covers the DS's own record of the tokens it issued and the calls it mediates. Enforcing a revoked delegation across Delegation Servers or across administrative domains is out of scope for this document.

Consent Flow

CIBA-Derived Agent Consent When an Agent requests a delegation that exceeds pre-authorized policies, the DS initiates a CIBA backchannel authentication request to the Subject. The Subject approves or denies on their registered device. On approval, the DS issues the Delegation Token. The Agent polls or receives a push notification when the token is available.

Consent Records The DS MUST store an immutable record of each consent event, including: Subject identifier, Agent DID, capabilities granted, grant time, expiry, and the full delegation chain context at time of consent. Records MUST be retained for at least 90 days.

Re-Consent Triggers Consent MUST be re-requested when: an Agent requests broader capabilities than previously granted the grant has expired the agent_operator claim changes a security event triggers policy re-evaluation

Implementation Status Note to the RFC Editor: please remove this section and the reference to before publication. This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in . The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to , "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".

Cred SDK

Implementer:

Kieran Sweeney (author of this document)

Location:

https://github.com/cred-ninja/sdk, branch main, described here as of commit 42b39f4 (2026-10-30), after integration of cred-ninja/sdk#89 to #93 through #96.

License:

Apache-2.0

Language:

TypeScript (Node.js)

Maturity:

Experimental. The implementation follows the architecture of this document (a Delegation Server holding deposited credentials, sub-delegation with attenuation, exercise by proxy), its receipt claim layout, and its Delegation Token, but not its agent authentication or exercise request formats. It is not wire-compatible with this document.

Contact:

kieran@kierans.net

Implemented as specified, or nearly: Agent identity (): did:key identifiers; the server accepts Ed25519 and P-256 keys, and the SDK client generates Ed25519 keys only. Receipt, assertion, and token verifiers hold a local accepted-algorithm list (EdDSA and ES256 by default). Protocol version negotiation (): the Cred-Protocol-Version header, version 0.1.0, and HTTP 426 with protocol_version_unsupported. Delegation Token (): a JWT of type dt+jwt carrying every required claim: iss naming the DS, the principal in sub, the acting agent in client_id and act.sub with prior agents in nested act, authorization_details of type cred_delegation, delegation_constraints when there are ceilings, cnf with the thumbprint of the agent's key, iat, exp, jti, consent_id, and an opaque credential_handle, plus prf with content identifiers of the receipts behind it. It lives 15 minutes by default and never more than 1 hour, and never past its parent or the stored credential. The DS records each token's state and re-reads it after a restart. Signed receipts (): a compact JWS at each hop, EdDSA or ES256 with kid, with iss naming the DS, the principal in sub, the acting agent in client_id and act.sub, prior agents in nested act, the delegation identifier as jti, cnf bound to the agent's key, a commitment to the parent (SHA-256 over the full compact parent receipt), and a signed lineage of ancestor agents. Before minting a child, the server re-verifies the parent receipt and checks the revocation of the parent delegation and the status of every ancestor agent. Sub-Delegation Exchange (): an authorization step that assigns the child's identifier, signs the receipt, and returns a single-use grant bound to the receiving agent's DID that expires within 60 seconds and never after the parent; and an token exchange in which the receiving agent presents the grant as subject_token and an assertion as actor_token, receiving a Delegation Token bound to its own key, with the parent's revocation re-checked at issuance. The grant's token type is a provisional urn:credninja: URN, since this document defines none. The older single-step sub-delegation remains available. Capabilities: catalogue operations with resources for GitHub repositories and Google Drive files, checked against the granted provider scopes at issuance, as a subset at every hop, and against the actual method and URL at exercise. Scope-shaped operations remain available; a token cannot mix them with catalogue operations. Unknown operations or resources are refused. Constraint ceilings (): all eight types, fail-closed parsing of closed constraint objects, uniqueness per (key, type), subsumption per hop with no inference across types, inherit-on-omit, rank read with its order, and a constraint of an unrecognized type carried and never treated as absent. Issuance refuses a max on max_calls, the key the server meters as a running count. The Delegation Token carries the ceilings in delegation_constraints; the receipt carries them in a claim named constraints, the name earlier revisions of this document used. Per-exercise ceilings: max, min, one_of, not_one_of, prefix, and rank are decided from quantities the DS measures, never ones the agent reports. Request-side checks precede dispatch; response-side checks withhold an over-limit response and audit the denial. A catalogue listing is capped before dispatch where its page-size parameter permits it. Unimplemented types and unmetered keys deny exercise. Withholding a response does not undo an upstream effect. Chain-verifiable profile (): the server mints tokens in the agent_delegation format on request, verifies a presented parent chain before minting a child, and records the token's jti and the scope mapping in the receipt. It does not accept such tokens at its exercise endpoint. Proof of possession (): a Delegation Token is issued only to a did:key agent that proves its key with a DPoP proof , and is bound to that key. Every exercise presents the token as a DPoP-bound access token with a fresh proof by the key whose ath is the hash of the token and which, through a SHA-256 hash of the JCS form of the exercise request, is bound to that one request: its upstream URL, method, body, and headers. Replayed, stale, and mismatched proofs are refused before any upstream call. A sub-delegated token is bound to the receiving agent's key, so the delegating agent that relays it cannot use it. Exercise (): provider credentials stay in the server's vault and the server makes the upstream call; by default the server hands no provider token to an agent. Revocation is checked when the request arrives and again just before the upstream call, with HTTP 401 delegation_revoked. An exercise under a constraint of an unrecognized type is denied, and max_lifetime and max_subtree totals are checked and debited atomically by a single-writer ledger. Consent records (): every root Delegation Token names, in consent_id, a record of the consent behind it (subject, agent DID, capabilities granted, how consent was given and by whom, grant time, expiry, and the chain context), which storage refuses to update. Records are retained for at least 90 days after the later of grant and expiry, then purged with an audited count. Consent approval (): a CIBA-derived poll flow for permissions requiring approval, with the Subject, an administrator, or both as approver. An approval is reused only for requests it covers. Broader capabilities, expired consent, looser ceilings, a different app client or approver requirement, and security events require approval again; revoked consent is checked at exercise. Cred Link: delegations use DPoP-bound Delegation Tokens, with the connection, client, grant and agent re-checked at exercise. Revocation (): DELETE /delegation/{jti} (also served as DELETE /api/v1/delegations/{id}) revokes a delegation and cascades to its descendants in one transaction, reporting revoked_count; tests measure the cascade under 5 seconds for up to 1,111 descendants. Audit: delegation, exercise, and revocation events in a log whose rows are chained by a keyed hash, with an endpoint that verifies the chain. Remaining differences and limitations: Agent authentication and exercise interface: root delegation uses a deployment credential and DPoP, not an assertion. Sub-delegation and token exchange use an actor_token. Exercise uses the Delegation Token and DPoP at POST /api/v1/use, naming an upstream URL, method and body rather than an operation at /exercise. Capabilities: no capability-level expires; catalogue resource kinds are repositories and files, not the folder resource illustrated in Section 5.2. Cred Link delegation does not accept requested constraint ceilings. Consent: no re-consent on agent_operator change. The CIBA-derived request and error formats differ from CIBA Core; approval state is in process memory, the built-in approval link is a bearer credential, and an external provider's id_token is not verified. A non-expiring consent can be purged after 90 days while dependent delegations remain live. Revocation: the 1-second single-token bound is not measured by tests, and revocation of one Cred Link token by identifier is not implemented. DPoP: the DS issues no nonce. Conformance results. At SDK commit 42b39f4, the native verifier, verifyAgentDelegationChain(), passes all 35 vectors from draft-asor-wimse-agent-delegation-chain-02 (attenu-guard v0.20.0) and all 36 from (attenu-guard v0.22.0). It reads each token without claim mapping. Every rejection is checked for the declared outcome, the hop, and the isolated rule; the added -03 vector, reject_child_adds_detail_type, is rejected at hop 2 for carrying a second detail. The SDK's own -02 test and the protocol repository's native runner provide repeatable checks. A separate, older runner maps the vectors' claims onto the SDK's receipt hop model and supplies signature and parent-hash checks itself. At the same SDK commit it passes all 20 -01 vectors; for -02 it reports 21 passes, 4 failures and 10 gaps; for -03, 21 passes, 4 failures and 11 gaps, unchanged from 4c61b88. These are different code paths and measurements. The failures are different rejection reasons; the gaps are claim rules the mapped model cannot represent, including audience, confirmation, the closed and single detail, and per-hop maximum depth. No vector is skipped. The native results above are the result for the token format. These are library-level results over fixed test vectors, not full protocol conformance. Neither runner covers holder binding or status (steps 6 and 7 of Section 6 of ), or the HTTP interface and wire formats defined in this document. The runners, vectors, and revision-pinned results are at https://github.com/cred-ninja/protocol/tree/main/conformance/asor-delegation-chain.

Security Considerations

Confused Deputy Mitigation Capability-shaped tokens eliminate ambient authority. An adversarially-prompted agent cannot widen its own capabilities since attenuation is DS-enforced. OAuth access tokens are ambient authority: any code holding the token exercises its full scope. For adversarially-promptable agents, this is a structural exploit vector. Cred delegation tokens are operation-bound, resource-specific, and constraint-bearing, following the principle that designation should equal authority .

Delegation Chain Splicing The mandatory prf chain with DS-signed receipts addresses the vulnerability in Sections 2.1-2.2 of disclosed to the OAuth WG on February 26, 2026 . Each receipt cross-references parent and child DT jti values along with both agent DIDs, preventing presentation of tokens from mismatched delegation contexts. The requested_actor/actor_token binding proposed in mitigates the same class of attack at the authorization server for the first delegation hop; the prf chain extends equivalent protection across every subsequent hop (see ). The two can compose: a DS can accept an actor-bound access token issued under as the credential it wraps, then produce prf receipts for every sub-delegation beyond that first hop.

DPoP Binding DPoP prevents Delegation Token theft and replay by requiring cryptographic proof of private key possession on every /exercise request. The proof is bound to the htm (HTTP method) and htu (URI) of the request, not to its body. Every exercise goes to the same /exercise endpoint and carries its operation and parameters in the body (), so the DPoP proof does not bind or distinguish them. The DS validates the actual operation and parameters against the Delegation Token (). Signed evidence of the request body would need a separate commitment to it, which this document does not define.

Prompt Injection Containment Because the underlying credential is never delivered to the Agent, a successful prompt injection attack on the Agent cannot exfiltrate it. That does not cover the DS itself () or a credential that an upstream response reflects or mints. The agent can only exercise capabilities already granted in its DT, and only via the DS /exercise endpoint. The blast radius of a compromised agent is bounded by its current DT's authorization_details.

Chain Depth Limits Implementations SHOULD enforce a maximum delegation chain depth of 5. Unbounded sub-delegation creates exponential revocation cascades and audit complexity.

Token Lifetime The default DT lifetime of 15 minutes limits the blast radius of any single token compromise. Implementations MUST NOT issue DTs with a lifetime exceeding 1 hour. The same cap applies to a token a DS issues under and to an access token it issues by exchange (), so that a token used away from the DS outlives a revocation by at most 1 hour ().

Model Identity and Substitution The agent_model claim is self-asserted. A credential valid for an agent remains valid if the operator substitutes the underlying model, a threat class raised against the AIMS predecessor framework in March 2026. Verifying model identity requires attestation of the agent runtime and is out of scope for this document. Deployments that need it should treat these claims as advisory policy input, not proof, and look to remote attestation work in the RATS WG.

Long-Term Evidence Delegation receipts are signed by the DS, with Ed25519 or P-256 unless a deployment uses ML-DSA; a deployment may sign its consent and audit records the same way. A signed record retained as dispute evidence beyond the period in which its signature can be trusted against a cryptographically relevant quantum computer loses its value as evidence unless it was anchored while still trustworthy, for example by periodic time-stamping under a post-quantum signature or by inclusion in an append-only log whose head is so signed. Deployments that retain signed records for that long SHOULD anchor them. Consent and audit records that are immutable but unsigned carry evidence only as strong as the integrity controls of their store; a deployment that relies on them as dispute evidence SHOULD commit their digests to such a log.

Trusted Delegation Server The DS holds the credentials Subjects deposit and is trusted with them. Compromise of the DS, of its operator, or of the path by which it releases the keys that protect stored credentials exposes those credentials and lets an attacker exercise them, with no Delegation Token and within whatever the upstream provider granted. Keeping credentials away from Agents does not remove this exposure; it concentrates it at the DS. Delegation receipts are signed by the DS. A DS-signed receipt proves that the DS authorized an action under its own records; it does not prove that the Subject, rather than the operator, approved the grant those records describe. Deployments that need stronger guarantees can isolate credential custody per tenant or run the DS in hardware-protected execution environments. Root approval that can be verified independently of the DS, signed with a key the user holds, is left to a later revision.

IANA Considerations This document requests registration of the following claims in the "JSON Web Token Claims" registry, using the template of Section 10.1.1 of . For each, the Change Controller is the IETF. Claim Name Claim Description Specification Document(s) agent_model Agent model identifier of this document agent_operator Agent operator of this document consent_id Consent record identifier of this document credential_handle Opaque Credential Vault handle of this document delegation_constraints Constraint ceilings of a Delegation Token of this document prf Delegation receipt references of this document The ceiling claim is named delegation_constraints because constraints is already registered in the "JSON Web Token Claims" registry, by Section 13.3 of , with a different value. This document requests registration of Cred-Protocol-Version () in the "Hypertext Transfer Protocol (HTTP) Field Name Registry" defined in Section 16.3.1 of , with status "provisional". The following are open for a later revision: defines no registry for authorization_details type values. Section 2 of recommends a collision-resistant namespace for types used across servers; this revision keeps the bare cred_delegation type and requests no registration for it. The delegation grant of is redeemed with the token exchange grant type. The token type identifier that names the grant in subject_token_type is not yet defined. Earlier revisions requested urn:ietf:params:oauth:grant-type:cred-delegation, which no part of the protocol uses; this revision withdraws that request.

The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf. This specification replaces and obsoletes the OAuth 1.0 protocol described in RFC 5849. [STANDARDS-TRACK] This specification defines a protocol for an HTTP- and JSON-based Security Token Service (STS) by defining how to request and obtain security tokens from OAuth 2.0 authorization servers, including security tokens employing impersonation and delegation. This specification defines a profile for issuing OAuth 2.0 access tokens in JSON Web Token (JWT) format. Authorization servers and resource servers from different vendors can leverage this profile to issue and consume access tokens in an interoperable manner. This document describes a mechanism for sender-constraining OAuth 2.0 tokens via a proof-of-possession mechanism on the application level. This mechanism allows for the detection of replay attacks with access and refresh tokens. This document specifies a new parameter authorization_details that is used to carry fine-grained authorization data in OAuth messages. This specification defines the use of a JSON Web Token (JWT) Bearer Token as a means for requesting an OAuth 2.0 access token as well as for client authentication. JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted. OpenID Foundation Work in Progress, draft-asor-wimse-agent-delegation-chain-03 In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This specification defines a method for computing a hash value over a JSON Web Key (JWK). It defines which fields in a JWK are used in the hash computation, the method of creating a canonical form for those fields, and how to convert the resulting Unicode string into a byte sequence to be hashed. The resulting hash value can be used for identifying or selecting the key represented by the JWK that is the subject of the thumbprint. Cryptographic operations like hashing and signing need the data to be expressed in an invariant format so that the operations are reliably repeatable. One way to address this is to create a canonical representation of the data. Canonicalization also permits data to be exchanged in its original form on the "wire" while cryptographic operations performed on the canonicalized counterpart of the data in the producer and consumer endpoints generate consistent results. This document describes the JSON Canonicalization Scheme (JCS). This specification defines how to create a canonical representation of JSON data by building on the strict serialization methods for JSON primitives defined by ECMAScript, constraining JSON data to the Internet JSON (I-JSON) subset, and by using deterministic property sorting. This document describes a simple process that allows authors of Internet-Drafts to record the status of known implementations by including an Implementation Status section. This will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. This process is not mandatory. Authors of Internet-Drafts are encouraged to consider using the process for their documents, and working groups are invited to think about applying the process to all of their protocol specifications. This document obsoletes RFC 6982, advancing it to a Best Current Practice. This document describes a mechanism for creating, encoding, and verifying digital signatures or message authentication codes over components of an HTTP message. This mechanism supports use cases where the full HTTP message may not be known to the signer and where the message may be transformed (e.g., by intermediaries) before reaching the verifier. This document also describes a means for requesting that a signature be applied to a subsequent HTTP message in an ongoing HTTP exchange. The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document describes the overall architecture of HTTP, establishes common terminology, and defines aspects of the protocol that are shared by all versions. In this definition are core protocol elements, extensibility mechanisms, and the "http" and "https" Uniform Resource Identifier (URI) schemes. This document updates RFC 3864 and obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230. RC v1.0 ACM SIGOPS Operating Systems Review PhD thesis, Johns Hopkins University Work in Progress, draft-carleton-workload-authz-grant-01 Work in Progress, draft-ietf-wimse-aims-00 IETF OAuth Working Group Work in Progress, draft-ietf-oauth-identity-chaining-17, in the RFC Editor queue National Institute of Standards and Technology OpenID Foundation Work in Progress, draft-niyikiza-oauth-attenuating-agent-tokens-02 Work in Progress (expired), draft-gco-oauth-delegate-sd-jwt-00 Work in Progress, draft-zhu-oauth-async-delegation-05 Work in Progress (expired), draft-hartman-credential-broker-4-agents-00 Work in Progress, draft-araut-oauth-transaction-tokens-for-agents-02 Work in Progress, draft-nelson-agent-delegation-receipts-15 Work in Progress, draft-reece-wimse-cross-org-delegation-02 Work in Progress, draft-yossif-agent-mandate-problem-00 OAuth Working Group mailing list Work in Progress (expired), draft-oauth-ai-agents-on-behalf-of-user-02 IETF WIMSE Working Group Work in Progress, draft-ietf-wimse-arch-08 IETF WIMSE Working Group Work in Progress, draft-ietf-wimse-wpt-02 Work in Progress, draft-ni-wimse-ai-agent-identity-04 Work in Progress (expired), draft-schwenkschuster-wimse-credential-exchange-03 Work in Progress, draft-goswami-agentic-jwt-01 Work in Progress (expired), draft-nennemann-wimse-ect-00 OWASP NIST NCCoE

Changes from -01 : the WAG identity travels only as receipt evidence and MUST NOT be carried in act; the -01 allowance for act iss and sub contradicted the client_id/act.sub agreement rule (Songbo Bu). : client_id keeps its RFC 8693 Section 4.3 meaning, the requesting client; the DS issues a token only to the agent it names. New : a hop is an authorization step by the delegating agent, which yields a single-use grant bound to the receiving agent, and an issuance step in which the receiving agent performs the token exchange under its own key (Songbo Bu). The DS assigns the child's jti at authorization, so the receipt can name it, and re-checks the parent's expiry and revocation at issuance. aligned with draft-asor-wimse-agent-delegation-chain-02: label-valued rank carries its order on the wire, replacing the registered-ordering rule; constraint objects are closed; uniqueness is per (key, type), so ranges are allowed; max is per exercise only; max_lifetime and max_subtree added, with the DS as the single writer of their running totals. A constraint of an unrecognized type no longer makes the claim malformed: it is carried, a child covers it only with a JCS byte-identical constraint , and any exercise under it is denied, as in Sections 4.2 and 4.3 of . The type, not the key, states whether a bound is per exercise or cumulative. A DS refuses a max on a key it meters as a running count. : the steps include the revocation check and the constraint check, with the atomic debit of cumulative totals, that and already required. ties the 401 for a revoked token to the authority check. Related Work: the paragraph updated to -02 and corrected. The two drafts share grammar, vocabulary, and subsumption but not a wire format; the -01 statement that either verifier checks the other's chains was wrong. New : tokens meant to be verified away from the issuing DS, including user-minted tokens, use the agent_delegation format unchanged. A DS may issue them and may read and check ones it did not issue; using such a token as the root of a DS chain is left to a later revision (Caleb Dyer). Cumulative ceilings under the profile are enforced only where a single writer holds the total; a verifier away from the DS enforces per-exercise ceilings and denies an action under a cumulative constraint unless it, or a component that authorizes the action for it, holds the running total. : revoked_count reports invalidation, not closure; a delegation exchanged for direct presentation to a resource server is only partially revoked until that token expires unless the resource server checks authority at commit; cascading revocation holds within one DS, and enforcement across administrative domains is out of scope (Deonte O'dell Watts). A call already dispatched upstream when a revocation takes effect is not recalled. : the 1-hour cap also covers a token a DS issues under and an access token it issues by exchange (); states the resulting bound: an enforcement point away from the DS admits no new action under a revoked delegation after the presented token expires, at most 1 hour after issuance. : ML-DSA permitted alongside Ed25519 and P-256; every verifier holds a local list of accepted algorithms, as in Section 6 step 1. Related Work, Nelson paragraph: updated to -15, which binds the delegatee by key thumbprint and states that key custody is attested out of band; a principal-signed root receipt adds assurance where that attestation shows a user-held, user-verified key. New in Security Considerations. : SDK described at main commit 42b39f4 after integration of the catalogue capabilities, server-measured per-exercise ceilings, CIBA-derived consent with retention, and Cred Link Delegation Tokens. Remaining authentication, exercise-interface, capability, consent, revocation and nonce differences are stated separately. Native results lead: 35 of 35 -02 vectors and 36 of 36 -03 vectors, with rejection outcome, hop and rule checked. The older hop-model measurement and the limits of library-level testing remain explicit. Related Work records the changes from -02 to -03. Limits stated: after , in , and in , the claim that credential theft is eliminated is bounded to the Agent; states that a DPoP proof covers method and URI, not the operation and parameters in the request body; new in Security Considerations states that the DS is trusted with the deposited credentials and what its signed receipts do and do not prove. : the optional agent_checksum claim is removed. IANA Considerations: JWT claim registrations completed with their template fields; Cred-Protocol-Version requested as a provisional HTTP field. The authorization_details type request is withdrawn, since defines no registry for type values, and so is the grant type URI, which no part of the protocol uses. The ceiling claim is renamed from constraints to delegation_constraints and registered, since constraints is already registered by OpenID Federation 1.0 with a different value. The undefined token type for the delegation grant is recorded as open. References: -01 to -03 and moved to normative, since depends on its format and verification algorithm; Nelson -13 to -15; -01 to -02; -03 to -04; -00 marked expired; normative; , , , and informative.

Changes from -00 Workload Authorization Grant composition (): WAG-provisioned workloads authenticate per ; act.sub stays the Agent DID; WAG identity travels as receipt identity evidence or as act iss and sub; WAG bearer status noted, proof of possession comes from the Delegation Token's DPoP binding. Delegation Token adds client_id naming the acting agent per and Section 10.3, which MUST agree with act.sub. New : the constraints claim adopts the Section 4.2 vocabulary (max, min, one_of, not_one_of, prefix, rank) and Section 4.3 subsumption, fail-closed parsing, inherit-on-omit, and the rank-label ordering rule. Numeric ceilings leave the capability object. Lifetime aggregates stay DS-debited. : per-hop re-verification of authority and freshness; monotonic narrowing stated as containment plus order-independent intersection; root subject preserved in sub, current actor in act.sub, prior actors as nested act for attribution only; actor attribution attested per hop with its as-of time; receipt content adds the root subject and identity evidence; a SHOULD-level per-hop audit record distinct from the receipt; sub-delegation subset rule reads equal or narrower. Related Work: added; AIMS and WAG references refreshed; Delegate SD-JWT paragraph notes the adoption call and the chain rules it leaves to this layer. New per : what the open source SDK implements and does not, and what the interop vector results do and do not cover. Related Work and references refreshed against Datatracker on 2026-10-13: identity chaining is in the RFC Editor queue at -17; the Delegate SD-JWT adoption call has closed, result pending; newer revisions of the Nelson, Reece, Zhu, Raut, Ni, Goswami, and WPT drafts; CB4A and ECT noted as expired. References: normative; , , and informative.

Acknowledgments The design of this protocol draws on UCAN attenuation semantics , the object-capability literature, and ongoing work in the IETF WIMSE and OAuth working groups. Threat modeling was informed by and . Rafael Asor's delegation chain draft supplied the constraint vocabulary adopted in -01; Iman Schrock found the defect in the first scope-class proposal; Wes Jackson supplied the per-hop attestation framing in ; Songbo Bu found the act/client_id contradiction in the WAG composition text and the requester gap behind ; Caleb Dyer argued for carrying rank order in the token and raised the user-minted deployment shape behind ; Deonte O'dell Watts asked for the revocation limits now stated in .