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OAuth Transaction Tokens Best Current Practice
draft-oauth-transactiontokens-bcp-00

Document Type Active Internet-Draft (individual)
Author Ashay Raut
Last updated 2026-01-18
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draft-oauth-transactiontokens-bcp-00
WG Working Group                                                 A. RAUT
Internet-Draft                                                    Amazon
Intended status: Informational                           18 January 2026
Expires: 22 July 2026

             OAuth Transaction Tokens Best Current Practice
                  draft-oauth-transactiontokens-bcp-00

Abstract

   This document provides best current practices for implementing and
   deploying OAuth 2.0 Transaction Tokens as specified in draft-ietf-
   oauth-transaction-tokens.  Transaction Tokens (Txn-Tokens) enable
   workloads in a trusted domain to preserve and propagate user identity
   and authorization context across service boundaries during the
   processing of external programmatic requests.  This BCP addresses
   practical deployment considerations including token service
   architecture, size management, propagation patterns, validation
   strategies, and operational monitoring that are essential for secure
   and effective implementation in production environments.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   https://example.com/LATEST.  Status information for this document may
   be found at https://datatracker.ietf.org/doc/draft-oauth-
   transactiontokens-bcp/.

   Source for this draft and an issue tracker can be found at
   https://github.com/ashayraut/oauth-transactiontokens-best-current-
   practice.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on 22 July 2026.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Background  . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Purpose of the BCP  . . . . . . . . . . . . . . . . . . .   4
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  Best Current Practices  . . . . . . . . . . . . . . . . . . .   4
     3.1.  Token Size Management . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Context Relocation  . . . . . . . . . . . . . . . . .   5
     3.2.  Token Lifetime and Expiration . . . . . . . . . . . . . .   6
     3.3.  Schema Governance . . . . . . . . . . . . . . . . . . . .   6
       3.3.1.  Backward Compatibility  . . . . . . . . . . . . . . .   7
     3.4.  Token Propagation . . . . . . . . . . . . . . . . . . . .   7
       3.4.1.  Propagation Libraries . . . . . . . . . . . . . . . .   7
       3.4.2.  Propagation Reliability . . . . . . . . . . . . . . .   8
       3.4.3.  Token Mix-up Prevention . . . . . . . . . . . . . . .   8
       3.4.4.  Trust Boundary Handling . . . . . . . . . . . . . . .   8
       3.4.5.  Cache Considerations  . . . . . . . . . . . . . . . .   9
     3.5.  Token Validation  . . . . . . . . . . . . . . . . . . . .   9
       3.5.1.  Error Handling  . . . . . . . . . . . . . . . . . . .   9
       3.5.2.  Fallback Policies . . . . . . . . . . . . . . . . . .   9
     3.6.  Telemetry and Monitoring  . . . . . . . . . . . . . . . .  10
       3.6.1.  Telemetry Aggregation . . . . . . . . . . . . . . . .  10
       3.6.2.  Key Metrics . . . . . . . . . . . . . . . . . . . . .  10
     3.7.  Key Management  . . . . . . . . . . . . . . . . . . . . .  10
     3.8.  Batch Processing pattern  . . . . . . . . . . . . . . . .  11
       3.8.1.  Initiation (Pausing the Transaction)  . . . . . . . .  11

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       3.8.2.  Rehydration (Resuming the Transaction)  . . . . . . .  11
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
     4.1.  Token Mix-up Prevention . . . . . . . . . . . . . . . . .  12
     4.2.  Trust Boundary Controls . . . . . . . . . . . . . . . . .  12
     4.3.  Cache Security  . . . . . . . . . . . . . . . . . . . . .  12
     4.4.  Fallback Mechanisms . . . . . . . . . . . . . . . . . . .  12
     4.5.  Token Lifetime  . . . . . . . . . . . . . . . . . . . . .  12
     4.6.  External Propagation  . . . . . . . . . . . . . . . . . .  12
     4.7.  Batch processing security consideration . . . . . . . . .  12
       4.7.1.  Token Constraining  . . . . . . . . . . . . . . . . .  13
       4.7.2.  Data Mutability and Consent . . . . . . . . . . . . .  13
       4.7.3.  Infinite Exchange Prevention  . . . . . . . . . . . .  13
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.1.  Informative References  . . . . . . . . . . . . . . . . .  13
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  13
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

1.1.  Background

   Modern distributed systems built on microservice architectures face a
   fundamental challenge: maintaining security context as requests
   traverse multiple service boundaries.  When an external actor
   initiates an API request, the user identity and authorization context
   must be preserved and made available to all downstream internal
   microservices involved in processing that request.  Without a
   standardized mechanism, organizations resort to ad-hoc solutions that
   introduce security vulnerabilities, operational complexity, and
   interoperability challenges.

   The OAuth 2.0 Transaction Tokens specification (draft-ietf-oauth-
   transaction-tokens) addresses this challenge by defining a token
   format and exchange protocol that enables secure context propagation
   across internal microservices within trusted domains.  However, the
   specification focuses on protocol mechanics rather than deployment
   practices.  Real-world implementations face additional challenges
   including latency constraints, token size limitations, schema
   evolution, propagation reliability, and operational monitoring.

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1.2.  Purpose of the BCP

   This Best Current Practice document provides implementers with
   guidance derived from production deployments of Txn-Token systems.
   It addresses practical considerations that fall outside the scope of
   the protocol specification but are critical for successful
   deployment.  The recommendations in this document are based on
   operational experience with large-scale microservice environments
   where hundreds of internal microservices must coordinate security
   context propagation across complex call chains.

   This BCP is intended for: - Organizations implementing Transaction
   Token Services - internal microservice developers integrating Txn-
   Token support - Security architects designing authorization systems -
   Operations teams monitoring token propagation

2.  Conventions and Definitions

   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 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119.  This
   document uses terminology from draft-ietf-oauth-transaction-tokens
   including "Transaction Token" (Txn-Token), "Transaction Token
   Service", "trusted domain", and "authorization context".

3.  Best Current Practices

   ## Transaction Token Service Implementation ### Service Architecture
   Organizations SHOULD setup Transaction Token Service (TTS) which
   hosts functionality to issue token, replace token and other Txn-Token
   related functionality.  Organizations SHOULD prefer architectures
   where the authorization service that authenticates and authorizes
   external actors, invokes the TTS for getting Transaction Token as
   part of authentication and authorization requests and pass Txn-token
   as well with it.  This way, it avoids an explicit calls from external
   endpoint to TTS and lesser code changes in external services.
   Additionally, all internal microservices that want to replace tokens
   SHOULD connect directly to TTS.  This architecture strikes balance
   between the options to either have authorization service host all TTS
   functionality or external services needing to connect TTS. ###
   Context Selection Transaction Token Services MUST include all
   mandatory claims defined in draft-ietf-oauth-transaction-tokens.

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   However, services SHOULD NOT include all optional contexts by
   default.  Optional contexts such as transaction context (tctx) or
   custom claims MUST be added only when explicitly requested.

   Organizations SHOULD provide client libraries that offer interfaces
   for requesting Txn-Tokens with specific optional contexts.  This
   approach prevents token bloat while ensuring that services can obtain
   the context they require.  When an optional context cannot be added
   due to parsing errors, format violations, or unavailability, the
   Transaction Token Service MUST NOT fail the token issuance.  Instead,
   it SHOULD issue the token without that specific context and MAY log
   the condition for operational monitoring.

3.1.  Token Size Management

   ### Size Limits Transaction Token Services MUST NOT issue tokens
   larger than 4KB.  While HTTP specifications do not mandate maximum
   header sizes, common web server implementations impose limits to
   prevent Denial of Service attacks.  Apache defaults to 8KB maximum
   header size, but organizations must account for other headers in the
   same request.  A 4KB limit for Txn-Tokens provides reasonable
   headroom while preventing operational issues.

   Organizations SHOULD implement monitoring on token size to detect
   trends toward the limit.  Services that consistently approach size
   limits indicate either excessive context inclusion or the need for
   context relocation strategies.

3.1.1.  Context Relocation

   When authorization context exceeds 4KB, Transaction Token Services
   SHOULD implement a relocation endpoint.  The service stores oversized
   contexts in a separate data store using the Txn-Token identifier as
   the primary key.  The Txn-Token itself contains only a reference to
   the relocated context.

   Client libraries for token validation SHOULD transparently handle
   context relocation.  When an internal microservice requests a context
   that has been relocated, the library fetches it from the relocation
   endpoint.  This pattern mirrors Policy Information Points in
   Attribute-Based Access Control (ABAC) systems where additional
   attributes are retrieved at runtime.

   Context relocation introduces additional latency and failure modes.
   Organizations SHOULD treat relocation as an exception rather than the
   normal case.  Monitoring SHOULD track relocation frequency to
   identify services that consistently require excessive context.

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3.2.  Token Lifetime and Expiration

   Transaction tokens SHOULD have a time-to-live of less than 5 minutes.
   Organizations SHOULD determine appropriate lifetimes by working
   backward from latency Service Level Agreements (SLAs) defined for
   external endpoints.

   Short token lifetimes reduce the window for token compromise and
   limit the impact of token mix-up scenarios.  However, lifetimes must
   accommodate the longest expected call chains in the SOA.
   Organizations SHOULD measure actual request processing times and set
   token lifetimes to exceed the 99th percentile by a reasonable margin.

   When tokens expire during request processing, services MUST NOT
   automatically request new tokens.  Expired tokens indicate either
   excessively long call chains or performance problems that require
   investigation.  Services SHOULD fail requests with expired tokens and
   emit telemetry for operational monitoring.

3.3.  Schema Governance

   ### Context Visibility Organizations MUST govern the contexts added
   to Txn-Tokens.  Once a context appears in a Txn-Token, it becomes
   visible to all services in the call chain.  Services may develop
   dependencies on these contexts in ways not anticipated by the context
   provider.  This phenomenon follows Hyrum's Law: with sufficient
   consumers, all observable behaviors of a system will be depended upon
   by somebody.

   Before adding a new context to Txn-Tokens, organizations MUST
   consider the implications of making that context universally visible.
   If a context represents an identifier or concept known only to
   services early in the call chain, adding it to the Txn-Token exposes
   it to all downstream services.  Those services may develop business
   logic dependencies on the context, not just security dependencies.

   When the format or semantics of a widely-visible context must change,
   the organization faces a painful migration process.  All services
   that depend on the context must be identified, updated, and deployed.
   Organizations SHOULD prefer adding new contexts with different names
   rather than changing existing contexts when semantic changes are
   required.

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3.3.1.  Backward Compatibility

   Organizations MUST implement backward compatibility tests for Txn-
   Token contexts.  Automated tests SHOULD verify that changes to
   context format or structure do not break existing consumers.  These
   tests SHOULD run as part of the continuous integration pipeline for
   the Transaction Token Service.

   Backward compatibility testing becomes increasingly important as the
   number of services consuming Txn-Tokens grows.  Without automated
   verification, format changes risk cascading failures across the SOA.

3.4.  Token Propagation

   ### Propagation Control Organizations MUST prevent Txn-Tokens from
   propagating outside the trusted domain.  While tokens contain
   encrypted sensitive data, organizations SHOULD implement explicit
   controls to block external propagation.  Propagation libraries MUST
   detect when an internal microservice attempts to include a Txn-Token
   in a request to an external endpoint and MUST remove the token from
   that request.

   This defense-in-depth approach protects against misconfiguration and
   implementation errors.  Even if token encryption remains secure,
   preventing external propagation eliminates entire classes of
   potential vulnerabilities.

3.4.1.  Propagation Libraries

   Organizations SHOULD provide standardized propagation libraries that
   handle token lifecycle within an internal microservice workload
   processing.  These libraries MUST extract the Txn-Token from the
   incoming HTTP header, store it in request-scoped memory, add the
   token to outgoing request headers, and clear it from memory when
   request processing completes.

   Standardized libraries provide several benefits.  First, they enforce
   propagation controls including external blocking to avoid the token
   flowing outside your trust boundary.  Second, they can be used to
   consistently emit telemetry about token initiation, propagation, and
   validation.  Third, they provide a centralized point for implementing
   fallback behaviors when tokens are missing.

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3.4.2.  Propagation Reliability

   Organizations SHOULD monitor propagation success rates across the
   SOA.  Unless propagation success reaches 100% for a given call chain,
   services cannot reliably enforce authorization policies based on Txn-
   Token contents.  Services MUST implement reasonable fallback
   behaviors when tokens are absent.

   Propagation libraries MAY implement automatic token initiation when
   an incoming request lacks a Txn-Token.  The library requests a
   placeholder token from the Transaction Token Service indicating that
   no context was received at the current service.  This placeholder
   enables downstream services to identify where propagation broke in
   the call chain, facilitating operational debugging.

3.4.3.  Token Mix-up Prevention

   Token mix-up represents the most severe propagation risk.  Mix-up
   occurs when a token intended for one request is incorrectly attached
   to a different request.  If token T1 is meant for request R1 and
   token T2 for request R2, but T2 is sent with R1 due to a propagation
   bug, actors may access data they are not authorized to see.

   Token mix-up scenarios are difficult to detect because they may not
   cause obvious failures.  The request succeeds but with incorrect
   authorization context.  Organizations MUST implement request-scoped
   token storage in propagation libraries to prevent mix-up.  Tokens
   MUST be associated with specific request contexts and MUST NOT be
   stored in shared or global state.

   Organizations SHOULD implement testing strategies that deliberately
   attempt to cause token mix-up under concurrent load.  These tests
   verify that propagation libraries correctly isolate tokens across
   concurrent requests.

3.4.4.  Trust Boundary Handling

   When requests cross trust boundaries within the organization,
   propagation libraries MUST either block token propagation or replace
   token contents with appropriately scoped contexts.  Organizations
   SHOULD define trust boundaries explicitly and configure propagation
   libraries with boundary detection logic.

   At trust boundaries, services MAY request new Txn-Tokens from the
   Transaction Token Service with contexts appropriate for the target
   trust domain.  This approach maintains context propagation while
   respecting security boundaries.

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3.4.5.  Cache Considerations

   The introduction of Txn-token provides more information now to the
   entire microservice architecture graph.  There are Services in the
   graph that cache data to avoid calling dependent services multiple
   times.  Now, they SHOULD consider Txn-Token contexts to be included
   in the cache keys.  If not included, there is a risk that incorrect
   data is vended out or cache hit is impacted because the dependent
   services might be using the Txn-Token contexts for computing the
   results which might get cached.

   Organizations SHOULD provide guidance to workload developers on cache
   key construction when Txn-Tokens are involved.  Cache invalidation
   strategies MUST account for context changes that affect cached data.

3.5.  Token Validation

   ### Validation Libraries Organizations SHOULD provide standardized
   validation libraries that handle signature verification, decryption,
   and token parsing.  These libraries SHOULD synchronize cryptographic
   keys in the background, ensuring that services always have current
   keys for verification and decryption.

   Validation libraries SHOULD decode Txn-Tokens into strongly-typed
   objects appropriate for the implementation language.  This approach
   prevents parsing errors and provides compile-time verification of
   context access patterns.

3.5.1.  Error Handling

   Validation libraries SHOULD emit standardized error codes for common
   failure conditions including expired tokens, malformed tokens, and
   signature verification failures.  These error codes enable consistent
   operational monitoring across the SOA.

3.5.2.  Fallback Policies

   Services SHOULD NOT automatically fail requests when Txn-Tokens are
   missing or invalid.  Organizations MUST define fallback policies that
   balance security with user experience.  Fallback policies MAY include
   serving redacted data, limiting functionality, or requesting step-up
   authentication.

   The appropriate fallback depends on the sensitivity of the requested
   operation.  Services accessing highly sensitive data MAY require
   valid Txn-Tokens and fail requests when tokens are absent.  Services
   providing less sensitive functionality SHOULD implement graceful
   degradation.

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3.6.  Telemetry and Monitoring

   ### Adoption Monitoring Transaction token adoption in large SOA
   environments takes time.  Organizations SHOULD implement
   comprehensive telemetry to monitor adoption progress, propagation
   reliability, and validation patterns.

   When organizations provide standardized libraries for token
   initiation, propagation, and validation, telemetry logic SHOULD be
   embedded in those libraries.  This approach ensures consistent
   telemetry across all services without requiring individual workload
   implementations.

3.6.1.  Telemetry Aggregation

   Services SHOULD aggregate telemetry locally before transmitting to
   centralized monitoring systems.  Local aggregation reduces network
   overhead and enables higher-frequency sampling without overwhelming
   monitoring infrastructure.

   Centralized monitoring systems SHOULD store telemetry in data
   warehouses that support analytical queries.  Organizations SHOULD
   implement automated monitors that alert on significant changes in
   propagation rates, validation failures, or token expiration rates.

3.6.2.  Key Metrics

   Organizations SHOULD monitor the following key metrics: - Token
   initiation rate by service - Propagation success rate by call chain -
   Token expiration rate during request processing - Validation failure
   rate by error type - Token size distribution - Context relocation
   frequency

   These metrics provide visibility into Txn-Token health across the SOA
   and enable rapid identification of deployment issues.

3.7.  Key Management

   Organizations MUST implement secure key management practices for Txn-
   Token cryptographic operations.  Key management SHOULD follow the
   guidelines in RFC 4107 "Guidelines for Cryptographic Key Management".

   Transaction Token Services MUST support key rotation without service
   disruption.  Validation libraries MUST support multiple concurrent
   keys to enable zero-downtime rotation.  Organizations SHOULD automate
   key rotation on a regular schedule.

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3.8.  Batch Processing pattern

   OAuth Transaction Tokens are designed to propagate security context
   through a call chain within a trust domain.  To maintain a high
   security posture without the overhead of a global revocation
   infrastructure, these tokens are short-lived (typically minutes).  In
   many modern architectures, a transaction may be asynchronous.  For
   example, a request may be placed on a message queue (e.g., Kafka,
   RabbitMQ) and processed by a worker service hours or days later.  By
   the time the worker resumes the transaction, the original Transaction
   Token has expired.

   Batch Token (Voucher): A long-lived, opaque, or encrypted token
   representing the transaction context during a period of rest.
   Initiator: The internal microservice that receives a Transaction
   Token and requests a Batch Token before an asynchronous pause.
   Rehydrator: The internal microservice that takes a Batch Token and
   exchanges it for a fresh, short-lived Transaction Token to resume
   processing.

3.8.1.  Initiation (Pausing the Transaction)

   When a internal microservice determines that a transaction will
   exceed the TTL of the current Transaction Token (TraT), it SHOULD
   request a Batch Token from the Transaction Token Service (TTS).  The
   request to the TTS SHOULD include: * The current valid TraT.  * The
   intended "use case ID" or "namespace" to constrain the token.

   The TTS returns a Batch Token with a TTL suitable for the
   asynchronous delay (e.g., 24 hours to 7 days).

3.8.2.  Rehydration (Resuming the Transaction)

   When a worker service (the Rehydrator) picks up the task, it MUST NOT
   use the Batch Token directly to call downstream services.  Instead,
   it MUST exchange the Batch Token at the TTS for a fresh TraT.  The
   TTS SHALL: 1.  Verify the Batch Token's signature and expiration.  2.
   Validate that the Rehydrator is authorized for the specific "use case
   ID" or "namespace" embedded in the Batch Token.  3.  Issue a new,
   short-lived TraT containing the original claims (e.g., subject,
   original requester IP).

4.  Security Considerations

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4.1.  Token Mix-up Prevention

   Token mix-up represents a critical security risk.  Organizations MUST
   implement request-scoped token storage and MUST test for mix-up
   scenarios under concurrent load.  Token mix-up can result in
   unauthorized data access without obvious system failures, making it
   particularly dangerous.

4.2.  Trust Boundary Controls

   Organizations MUST define trust boundaries explicitly and MUST
   implement controls that prevent inappropriate token propagation
   across those boundaries.  Failure to control propagation at trust
   boundaries can expose sensitive contexts to unauthorized services.

4.3.  Cache Security

   Services that cache data based on Txn-Token contexts face security
   risks if cache keys do not incorporate all relevant contexts.
   Organizations MUST provide guidance on secure cache key construction
   and MUST audit caching services for correct context handling.

4.4.  Fallback Mechanisms

   While fallback mechanisms improve availability, they can introduce
   security vulnerabilities if not carefully designed.  Organizations
   MUST ensure that fallback policies do not inadvertently grant
   excessive access when Txn-Tokens are absent.  Fallback policies
   SHOULD be explicitly documented and reviewed by security teams.

4.5.  Token Lifetime

   Short token lifetimes reduce the window for token compromise but may
   cause operational issues if set too aggressively.  Organizations MUST
   balance security considerations with operational requirements when
   setting token lifetimes.

4.6.  External Propagation

   Preventing Txn-Tokens from leaving the trusted domain is critical.
   Organizations MUST implement multiple layers of defense including
   library-level controls, network-level filtering, and monitoring for
   external propagation attempts.

4.7.  Batch processing security consideration

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4.7.1.  Token Constraining

   Batch Tokens MUST be sender-constrained or scoped to specific
   namespaces.  This prevents a compromised service from "stealing" a
   Batch Token from a queue and successfully minting a Transaction Token
   for an unrelated flow.

4.7.2.  Data Mutability and Consent

   Asynchronous delays increase the risk that the underlying
   authorization context has changed (e.g., a user has revoked consent).
   The TTS SHOULD perform a "freshness check" during rehydration for
   claims marked as mutable or sensitive.

4.7.3.  Infinite Exchange Prevention

   To prevent a transaction from living indefinitely through repeated
   rehydrations, the TTS SHOULD implement a maximum chain depth or total
   transaction lifetime counter within the token metadata.

5.  IANA Considerations

   This document has no IANA actions.

6.  References

   ## Normative References RFC2119
   (https://datatracker.ietf.org/doc/html/rfc2119) Bradner, S., "Key
   words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC
   2119, DOI 10.17487/RFC2119, March 1997.

   TXNTOKENS (https://www.ietf.org/archive/id/draft-ietf-oauth-
   transaction-tokens-06.html) Tulshibagwale, A., Hardt, D., and G.
   Fletcher, "OAuth 2.0 Transaction Tokens", draft-ietf-oauth-
   transaction-tokens-06 (work in progress).

6.1.  Informative References

   RFC4107 (https://datatracker.ietf.org/doc/html/rfc4107) Bellovin, S.
   and R.  Housley, "Guidelines for Cryptographic Key Management", BCP
   107, RFC 4107, DOI 10.17487/RFC4107, June 2005.

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

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Internet-Draft  OAuth Transaction Tokens Best Current Pr    January 2026

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

Acknowledgments

   TODO acknowledge.

Author's Address

   ASHAY RAUT
   Amazon
   Email: asharaut@amazon.com

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