# Protocol filing status ledger > Last verified: 2026-08-22 UTC. Website: https://harnlang.com/protocol-contributions/status-ledger.html This page documents Harn, which is pre-1.0. Language, standard library, and CLI APIs may change. If the intended version is unclear, clarify before using this page. --- Last verified: 2026-08-22 UTC. This ledger records direct upstream reads for the protocol-contribution threads that back the RFCs in this directory. It is reference material and intentionally factual: record a state here only after fetching the upstream discussion, PR, or issue directly. **What changed since the 2026-07-25 read.** Two threads moved and the rest sat still. - **A2A `#2028` is the busiest thread and the hardest to read.** Twelve new comments through 2026-08-20 took it from 12 to 24. Two participants posted executable vectors for the well-formedness/authority split and reported no divergences between them, an `originAnchor` slot was reserved and pinned inert, and a review from the ZeroID side supplied a correction to the extension text: per-hop `scopes` are **derived from a validated credential**, never authorization-bearing. Weigh that volume against [who is in the thread](#who-is-in-2028) before treating it as demand. The drafting action was claimed by a third party, not by us. - **oauth-wg `#73` handed the ball back to us.** A draft author replied on 2026-07-25, after our answer the same day, redirecting the actor-chain half to [`draft-mcguinness-oauth-actor-profile`](https://github.com/mcguinness/draft-mcguinness-oauth-actor-profile) and its receipts, proofs, and authority-bounds companions. That repository has no thread from us, so the invitation is unanswered. - Everything else — ACP `#1220`, `#1224`, `#1233`, `#1261`; A2A `#1857`, `#1858`, `#2027`; MCP `#3007`, `#3008` — is unchanged. MCP `#2736` is closed from our side. ## Public follow-up posture Upstream comments and PRs should use neutral ecosystem evidence, peer behavior, and public prior art. Do not lead with Harn or Burin-specific adoption claims. A local implementation can inform our internal confidence, but public posts should stand on protocol semantics and independently checkable examples. One qualification, from reading the MCP SEP process on 2026-07-25: a **prototype offered as feasibility evidence is not an adoption claim**, and the SEP process explicitly requires one before acceptance ("pseudocode alone" and "a design document without code" are called out as insufficient). Offering a runnable proof-of-concept is in-posture; citing internal usage numbers as an argument is not. ## Every filing at a glance | Thread | Filed | Maintainer engaged? | Third-party support | Ball is with | |---|---|---|---|---| | [ACP #1220](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1220) `session/inject` | 2026-05-17 | Yes — invited the RFD | 3 independent | Maintainers (review of `#1261`) | | [ACP #1261](https://github.com/agentclientprotocol/agent-client-protocol/pull/1261) inject RFD | 2026-05-19 | Not since 2026-06-27 rebase | 3 independent | Maintainers | | [ACP #1224](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1224) `session/remind` | 2026-05-17 | Yes — soft-parked 2026-07-06 | none | Maintainers (by their own request) | | [ACP #1233](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1233) `session/suspend` | 2026-05-17 | No | 1 (peer implementer) | Peer + maintainers — replied 2026-07-25 | | [A2A #1857](https://github.com/a2aproject/A2A/discussions/1857) idempotency | 2026-05-17 | No | 1 | **Us** — posture decision | | [A2A #1858](https://github.com/a2aproject/A2A/discussions/1858) `PAUSED` | 2026-05-17 | No | 3 | Maintainers (process question) | | [A2A #2027](https://github.com/a2aproject/A2A/discussions/2027) `InjectTaskReminder` | 2026-07-03 | No | none | Nobody — cold | | [A2A #2028](https://github.com/a2aproject/A2A/issues/2028) actor-chain | 2026-07-03 | No | 5 — [see caveat](#who-is-in-2028) | Nobody upstream — a third party claimed the drafting action | | [MCP #2736](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/2736) budget caps | 2026-05-17 | No | 2 | **Closed by us** — target feature deprecated by SEP-2577 | | [MCP #3007](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/3007) `notifications/reminder` | 2026-07-03 | No | none | **At risk** — adjacent surface (Logging) deprecated | | [MCP #3008](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/3008) `authenticatedIdentity` | 2026-07-03 | No | 1 | **Us** — sponsor outreach | | [oauth-wg #73](https://github.com/oauth-wg/oauth-identity-assertion-authz-grant/issues/73) actor chain | 2026-07-03 | **Yes — direct question to us** | n/a | **Us** — invited to continue in the actor-profile repo | Nothing has been rejected anywhere, and across twelve threads the pattern is consistent: proposals draw third-party comment and no maintainer verdicts. Read the third-party column as a count of commenters, not as a quality signal — track records vary sharply between threads, and `#2028` carries the caveat in [Who is in `#2028`](#who-is-in-2028). One thread, oauth-wg `#73`, is waiting on us, by direct invitation from a draft author. **One correction to that read, found 2026-07-25.** "Maintainer attention is the binding constraint" is not the diagnosis everywhere. MCP `#2736` was silent because the feature it extends was **deprecated** by [SEP-2577](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577) on 2026-05-15, which no amount of maintainer attention would have changed. Before attributing silence to bandwidth, confirm the target surface still has a future. See [lifecycle status of target surfaces](#lifecycle-status-of-target-surfaces). ## ACP Context as of 2026-07-25: unchanged from the 2026-07-03 read. The v2 RFD collection is the most active area of the repo, but every v2 RFD PR merged since 2026-06-01 was maintainer-authored. Externally-authored RFD PRs (including `#1261`) sit in review while their content gets absorbed into `unstable-v2` commits. Plan for discussions to be the unit of influence, not PR merges. Two v2 docs matter for our filings: the merged session-resume-replay RFD (unified `session/load` + `session/resume`, optional `replayFrom` cursor) is the substrate any `session/suspend` follow-up must sit on, and open PR [`#1237`](https://github.com/agentclientprotocol/agent-client-protocol/pull/1237) (client-provided system prompt) overlaps the `session/remind` territory and should be differentiated against, not ignored. | Item | Verified state | Notes | |---|---|---| | [`agentclientprotocol/agent-client-protocol#1220`](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1220) | Open discussion, 4 comments. | A maintainer invited an RFD; the follow-up RFD is PR [`#1261`](https://github.com/agentclientprotocol/agent-client-protocol/pull/1261). Two third-party comments since: `point-source` (Kandev, an ACP client running multiple agents, 2026-07-10) endorses the `queue`/`steer` split and specifically wants agents to advertise `session.inject.modes` so clients can gate UI per agent instead of hardcoding assumptions; `ofekron` (2026-07-20) argues acceptance, delivery, and application are three distinct states — for `queue`, acceptance should mean durably recorded, not model-visible; for `steer`, delivery means the input crossed a declared safe breakpoint and application means the continuation turn incorporated it. | | [`agentclientprotocol/agent-client-protocol#1261`](https://github.com/agentclientprotocol/agent-client-protocol/pull/1261) | Open PR, mergeable, `REVIEW_REQUIRED`, +357/-0. No maintainer review at any point; none since the 2026-06-27 rebase. | The only review is `SteffenDE` (2026-05-21), self-described as non-authoritative, who also closed their overlapping `promptQueueing` PR in favor of waiting for v2. Two production adoption reports arrived unprompted: `xxchan` (repo CONTRIBUTOR, [Raft](https://raft.build), 2026-07-10) states the absence of steering "is currently an adoption blocker for ACP" for a multi-agent platform where users send corrections from another client mid-execution; `ChrisAkre` (2026-07-19) implemented a Copilot-SDK→ACP bridge with `session/inject` for multi-client fanout and reports it "an utterly massive quality of life improvement." | | [`agentclientprotocol/agent-client-protocol#484`](https://github.com/agentclientprotocol/agent-client-protocol/pull/484) | Closed in favor of `#1261`. | Relevant predecessor for prompt queueing / steer-via-yield framing. | | [`agentclientprotocol/agent-client-protocol#1224`](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1224) | Open discussion. **Maintainer replied 2026-07-06** — supersedes the previous "no maintainer response" state. | `benbrandt` (MEMBER) answered the 2026-06-27 ping: "let me revisit in a bit. We also had a lot of drafts and so I have been trying to churn through those so we could actually make progress on some more." Soft-parked behind v2 draft triage, explicitly not declined. Do not re-ping; the maintainer has asked for time. | | [`agentclientprotocol/agent-client-protocol#1233`](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1233) | Open discussion, no maintainer reply. **New third-party feedback 2026-07-20.** | `ofekron`, disclosing that they maintain [Better Agent](https://github.com/ofekron/better-agent) (durable provider sessions, operator approvals, restart recovery), endorses the reduced v2 shape and asks that `session/suspend` be an acknowledged request rather than a notification, with an observable `requested → quiescing → suspended` state machine. **Replied 2026-07-25** ([`discussioncomment-17781001`](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1233#discussioncomment-17781001)): accepted the acknowledged-request framing and pinned each state to a wire guarantee — `requested` starts no new work but in-flight work may still emit, `quiescing` drains, `suspended` is the only state where a client may assume the transcript is stable. Scope unchanged. Our 2026-07-03 v2 alignment comment ([`discussioncomment-17525582`](https://github.com/agentclientprotocol/agent-client-protocol/discussions/1233#discussioncomment-17525582)) stands. | | [`agentclientprotocol/registry#397`](https://github.com/agentclientprotocol/registry/pull/397) | **Merged.** Harn is listed in the ACP registry. | Supersedes the previous "open, no review decision" state. Entry refreshed to Harn v0.9.15 before merge, with `build_registry.py --dry-run` and `verify_agents.py --auth-check` validation posted. | | [`agentclientprotocol/registry#460`](https://github.com/agentclientprotocol/registry/pull/460) | Closed by us, 2026-07-25. | A fork-local documentation convention (`CLAUDE.md` → `AGENTS.md` symlink) opened against upstream by mistake. No upstream signal; recorded only so the closure is not re-investigated. | ## A2A Context as of 2026-07-25: unchanged from the 2026-07-03 read. A2A v1.0.0 shipped 2026-03-12 (v1.0.1 on 2026-05-28), which predates our 2026-05-17 filings. v1.0 renamed operations to PascalCase across all bindings (`message/send` → `SendMessage`, subscription → `SubscribeToTask`), moved enums to `SCREAMING_SNAKE_CASE` per ProtoJSON, removed `kind` discriminators, and made `a2a.proto` the normative source of truth. Both filed discussions and the RFCs in this directory originally used pre-1.0 naming; the RFCs were revised to v1.0 conventions on 2026-07-03, and any follow-up upstream post should use v1.0 names. Extension mechanics, read 2026-07-25: extensions are declared as `AgentExtension` entries under `AgentCapabilities` (URI, description, required flag, params) and activated by `A2A-Extensions` header negotiation, with the agent echoing back what it activated. Four categories exist — data-only, profile, method, and state-machine extensions. Only the canonical `https://a2a-protocol.org/extensions/` prefix is reserved for official extensions under `a2aproject` governance; **community extensions may be self-published under their own URI**, with permanent-identifier services such as w3id.org recommended. A new URI MUST be used for any breaking change to an extension's logic, data structures, or required params. This matters for `#1858` and `#2028`: both have a path that does not depend on a TSC answer. | Item | Verified state | Notes | |---|---|---| | [`a2aproject/A2A#1857`](https://github.com/a2aproject/A2A/discussions/1857) | Open discussion, 1 comment, **no activity since 2026-05-18** — the coldest of our filings. | Idempotency keys + post-cancel state semantics. `chopmob-cloud` endorsed from production and recommended accepting the key in both the request body and a Stripe-style `Idempotency-Key` HTTP header, key opaque to A2A with a server-chosen window. Still titled with pre-v1.0 `tasks/send`, and the only filing with **no RFC source doc in this directory**. Posture decision tracked in [harn#5540](https://github.com/burin-labs/harn/issues/5540). | | [`a2aproject/A2A#1858`](https://github.com/a2aproject/A2A/discussions/1858) | Open discussion, 12 comments, no maintainer/TSC reply. Unchanged since 2026-06-27. | Community feedback converged on one `PAUSED` state plus a structured `pause` object (`initiatedBy`, `pausedUntil` lease, `resumeToken`) rather than separate enum values, plus an opaque `lastSideEffectRef` whose absence must not be read as proof that no side effect occurred. The draft-PR-vs-extension ping ([`discussioncomment-17455657`](https://github.com/a2aproject/A2A/discussions/1858#discussioncomment-17455657)) is still unanswered. Given the extension mechanics above, self-publishing is an option if the thread stays cold. | | [`a2aproject/A2A#1937`](https://github.com/a2aproject/A2A/issues/1937) | Open issue, 5 comments, last updated 2026-08-14. | Context-binding profile for delegated authority — binds an already-valid delegation to a task/session/target/scope. Complement of (not substitute for) the [actor-chain extension RFC](./a2a-actor-chain-extension.md); best anchor thread for that filing. Two third-party comments arrived since the last read, both pushing on lifetime rather than shape: a delegated-commerce case for nested spend limits (2026-08-09), and the observation that a cryptographically valid delegation can become operationally invalid when policy or risk state changes after issuance (2026-08-14). | | [`a2aproject/A2A#153`](https://github.com/a2aproject/A2A/issues/153) | Open issue (since 2025-06). | Confused-deputy framing for A2A; canonical motivation citation for payload-visible principals. | | [`a2aproject/A2A#2027`](https://github.com/a2aproject/A2A/discussions/2027) | Filed 2026-07-03 (Ideas category). **Zero comments after 22 days.** | `InjectTaskReminder` ambient-context discussion, from the [reminder RFC](./a2a-message-kind-reminder.md) with A2A v1.0 naming. Dupe-checked before filing. Cold-start with no venue warming; see [harn#1829](https://github.com/burin-labs/harn/issues/1829). | | [`a2aproject/A2A#2028`](https://github.com/a2aproject/A2A/issues/2028) | Filed 2026-07-03. Open issue, **24 comments**, active through 2026-08-20, still no maintainer. | Actor-chain extension, anchored to `#1937` / `#153`. Through 2026-07-25 the thread converged on two properties that must be stated separately: **well-formedness** (each hop's `scopes` a subset of its predecessor's, checkable from the payload alone, making `#153`'s confused deputy detectable without a cross-hop log join) and **authority** (unprovable from a caller-supplied payload, so it needs a per-hop `proof_ref` an outside verifier resolves). Our consolidating restatement is [`issuecomment-5079449815`](https://github.com/a2aproject/A2A/issues/2028#issuecomment-5079449815). Since then: `navigatorbuilds` published executable vectors for both properties including negatives, `giskard09` reported running an implementation against them with zero divergences (and reproduced the same documented limit — a hop that rewrites its predecessor's scopes upward narrows perfectly in the forwarded chain, so it is only catchable receiver-side), and an `originAnchor` slot was reserved and pinned inert by forward-compat and no-privilege-via-anchor vectors. On 2026-08-20 `rsharath` ([ZeroID](https://github.com/highflame-ai/zeroid)) mapped OAuth token exchange onto the shape and supplied the correction now owed to the extension text: per-hop `scopes` are **derived from the validated credential**, not literal RFC 8693 `act` contents and never authorization-bearing. `navigatorbuilds` said in the same thread that *they* would fold that correction into the extension text, so the drafting action is not ours. Before spending further effort here, read [Who is in `#2028`](#who-is-in-2028). | ### Who is in `#2028` Recorded because the comment count on this thread is the strongest-looking number in the ledger and it does not mean what a reader would assume. Verified 2026-08-23 against the GitHub API. - **All 24 comments carry `author_association: NONE`.** No maintainer, member, owner, or collaborator of `a2aproject` has ever replied. The "No" in the maintainer column is not "not yet" — it is fourteen months of silence on a thread the ledger elsewhere calls the busiest. - **Two accounts wrote 15 of the 24 comments**: `navigatorbuilds` (8) and `giskard09` (7). They are also the "two implementations" whose agreement the ledger cited. Two parties who have been in continuous conversation since 2026-07 corroborating each other is weaker evidence than the phrase "independent implementations" suggests, and this ledger should not have used it. We authored exactly one comment (2026-07-25). - **Several participants have very new accounts**: `navigatorbuilds` created 2026-01-26 (1 follower), `0xbrainkid` 2026-01-27, `giskard09` 2026-03-23. Their comments are long, uniformly formatted, and some carry AI-assistance disclosures. That is not proof of anything, and none of it makes the technical content wrong — the well-formedness/authority split stands on its own reasoning. It does mean the thread is not evidence of ecosystem demand. - **The one participant with a long track record and a real project**, `rsharath` (account 2013, [ZeroID](https://github.com/highflame-ai/zeroid)), commented once, on 2026-08-20, and supplied the most useful correction in the thread. Practical consequence: treat `#2028` as a design conversation that produced one good correction, not as upstream traction. Volume of agreement in a thread with no maintainer in it is not a signal to invest against. ## MCP and OAuth Identity ### MCP process facts (read 2026-07-25) Recorded here because both open MCP items are process-blocked rather than substance-blocked, per the [SEP guidelines](https://modelcontextprotocol.io/community/sep-guidelines): - A SEP is a **PR** adding `seps/0000-title.md`, renamed to the PR number once opened — not an issue and not a discussion. - Required sections: Preamble, Abstract (~200 words), Motivation, Specification, Rationale, Backward Compatibility, Reference Implementation, Security Implications. Insufficient motivation is called out as grounds for outright rejection. - **A sponsor is mandatory** to move `Awaiting Sponsor` → `draft`: a Core Maintainer or Maintainer from `MAINTAINERS.md`. Tag 1–2 relevant maintainers, not everyone; if no response in two weeks, ask in `#general` on Discord. - No sponsor within **6 months** means `dormant`, which the process states explicitly is *not* rejection and is revivable. - Discussing with the relevant working/interest group on Discord first is described as "the single best way to refine your proposal and build early support," and a cold PR submission is the weakest entry point. - A **prototype is required before acceptance** (not before submission); pseudocode or a design document alone is insufficient. - Standards Track SEPs with observable protocol behavior additionally need a merged conformance scenario plus a `sep-NNNN.yaml` traceability file mapping every MUST/SHOULD before `Final` — not before acceptance. ### IETF draft facts (read 2026-07-25) The actor-chain gap has **partly resolved upstream in our favour.** The representation half is being standardized; the semantic half is explicitly out of scope, and that is the half we have implementation experience in. - **ID-JAG** (`draft-ietf-oauth-identity-assertion-authz-grant`) is at **revision 04, 2026-05-21**, an active OAuth WG draft with no intended RFC status set. `actor_token` is now `OPTIONAL` and permitted, but the draft deliberately stops there: "This specification does not define normative processing requirements for actor_token or whether an act claim is included in the issued ID-JAG." It defers to profiles. This supersedes our original premise that ID-JAG "explicitly disables `actor_token`," which was true of an earlier revision. - **The Actor Profile** (`draft-mcguinness-oauth-actor-profile`, **2026-04-30**, expires 2026-11-01) is that profile, and covers more than we assumed. Multi-hop chains are specified: "Delegation chains MUST be represented by nesting `act` objects... the outermost `act` object identifies the immediate actor; inner `act` objects represent prior actors." Implementations "SHOULD support a local maximum of at least depth 4." Preservation is mandated more strongly than we asked for: "The AS MUST NOT silently drop an inbound `act` claim; if it cannot preserve or extend the chain, it MUST reject the request." The canonical actor identifier is the (`act.iss`, `act.sub`) **pair**, not `act.sub` alone. - **What the profile explicitly declines to standardize**, and therefore remains open: (1) per-hop scope narrowing — "This document does not standardize the policies by which systems determine whether a given actor is permitted to act for a subject," scope reduction is deployment-specific; (2) per-hop proof-of-possession — "Other members carried inside an `act` object... do not have standardized proof-of-possession semantics," only the top-level `cnf` conveys the current presenter's key. | Item | Verified state | Notes | |---|---|---| | [`modelcontextprotocol/modelcontextprotocol#2736`](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/2736) | Open discussion, 6 comments, **closed out from our side 2026-07-25**. No maintainer response at any point. | Per-call sampling budget caps. `ralftpaw` separated host policy limits from server-declared budget intent; `HarperZ9` endorsed a deliberately small first SEP and argued the load-bearing field is the decision basis (estimated cost, policy limit applied, meter basis) rather than `max_cost_usd`. We were drafting that SEP when we found [SEP-2577](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577) had deprecated Sampling on 2026-05-15, and posted the reasoning rather than filing. `ralftpaw` agreed the same day: if per-call ceilings reappear on the direct-provider path they should stay host-owned rather than server-negotiated. Design record kept at [the RFC source doc](./mcp-sampling-budget-caps.md) with a runnable prototype at `experiments/mcp-sampling-budget-caps/`. Tracked in [harn#5539](https://github.com/burin-labs/harn/issues/5539). | | [`modelcontextprotocol/modelcontextprotocol#3007`](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/3007) | Filed 2026-07-03 (Ideas - General). **Zero comments after 22 days.** | `notifications/reminder` server→host ambient-context discussion, from the [reminder RFC](./mcp-notifications-reminder.md). Dupe-checked before filing. Same cold-start pattern as A2A `#2027`; the reminder primitive has no natural WG home, which is the likely cause. | | [`modelcontextprotocol/modelcontextprotocol#3008`](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/3008) | Filed 2026-07-03 (Ideas - General). One supportive third-party reply 2026-07-12; no maintainer. | `authenticatedIdentity` pre-SEP discussion, from the [identity RFC](./mcp-authenticated-identity.md). `tamish560` confirms the gap from experience: the "connected as" question is unanswerable today without per-server knowledge of which tool returns user info, and `InitializeResult` is the right slot because the server already knows who authorized the session. Progression is sponsor-gated; that outreach is unstarted. | | [`modelcontextprotocol/modelcontextprotocol#214`](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/214) | Closed. | Maintainer guidance on 2026-01-16 pointed custom auth pieces toward [`modelcontextprotocol/ext-auth`](https://github.com/modelcontextprotocol/ext-auth). | | [`modelcontextprotocol/ext-auth#13`](https://github.com/modelcontextprotocol/ext-auth/issues/13) | Open, still no activity since 2026-01-31. | Maintainer response says Enterprise-Managed Authorization does not currently support distinguishing agent vs user identity and points to ID-JAG issue `#73`. | | [`oauth-wg/oauth-identity-assertion-authz-grant#73`](https://github.com/oauth-wg/oauth-identity-assertion-authz-grant/issues/73) | Open, 7 comments. **The ball is with us since 2026-07-25.** | The live venue for actor-chain work. Our implementer feedback was posted 2026-07-03 ([`issuecomment-4878092226`](https://github.com/oauth-wg/oauth-identity-assertion-authz-grant/issues/73#issuecomment-4878092226)) per the [positioning note](./oauth-actor-chain-positioning.md), and we answered the draft author's question on 2026-07-25 ([`issuecomment-5079449594`](https://github.com/oauth-wg/oauth-identity-assertion-authz-grant/issues/73#issuecomment-5079449594)): nested `act` is the representation we wanted, fail-closed on unpreservable chains is the right default, `(act.iss, act.sub)` being canonical is a migration hazard worth naming in security considerations, and we offered to draft a companion profile pinning the well-formedness half. `mcguinness` replied the same day that this belongs in [`draft-mcguinness-oauth-actor-profile`](https://github.com/mcguinness/draft-mcguinness-oauth-actor-profile) rather than in ID-JAG scope, naming the actor-receipts, actor-proofs, and (experimental) authority-bounds drafts. That repository has no thread from us. | | [`oauth-wg/oauth-identity-assertion-authz-grant#80`](https://github.com/oauth-wg/oauth-identity-assertion-authz-grant/issues/80) | Closed as completed and milestoned 2026-04-22. | Optional `actor_token` proposal split out from `#73`; folded into the `#73` direction rather than rejected, and now carried by the Actor Profile draft. | | [`modelcontextprotocol/modelcontextprotocol#1299`](https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1299) | Closed as completed 2025-09-02. | SEP-1299 is server-side OAuth flow management, unrelated to a server→client identity surface; it does not claim the `authenticatedIdentity` slot. | | [`modelcontextprotocol/modelcontextprotocol` discussion `#1827`](https://github.com/modelcontextprotocol/modelcontextprotocol/discussions/1827) | Open discussion, unanswered (opened 2025-11-17). | `upstream_identity` propagation, client→server — the opposite direction from the [`authenticatedIdentity` RFC](./mcp-authenticated-identity.md); the two compose. | ## Lifecycle status of target surfaces Verified 2026-07-25 against the [MCP deprecated-features registry](https://modelcontextprotocol.io/specification/draft/deprecated). Check this before any further work on a filing: a proposal that extends a deprecated surface cannot land, regardless of its merits or its support. MCP deprecated three features in [SEP-2577](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2577) as of protocol version `2026-07-28`, each with earliest removal in the first revision released on or after 2027-07-28: | Deprecated feature | Migration path | Touches our filings | |---|---|---| | Sampling | Integrate directly with LLM provider APIs | **Kills MCP `#2736`** | | Logging | `stderr` for stdio; OpenTelemetry for observability | **Risk to MCP `#3007`** | | Roots | Tool parameters, resource URIs, or server config | None | | Dynamic Client Registration ([PR #2858](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/2858)) | Client ID Metadata Documents | None here; see note below | **MCP `#2736` is dead.** It proposed budget caps on `sampling/createMessage`. The feature is deprecated and the migration path is to stop using it. Recorded in full in the [budget-caps RFC](./mcp-sampling-budget-caps.md), retained as a design record rather than deleted. **MCP `#3007` needs to differentiate or be dropped.** It proposes `notifications/reminder`, a new server-to-client notification. Logging — the existing server-to-client notification channel — was deprecated in the same SEP, with observability pushed to OpenTelemetry. The proposals are not the same thing: ambient context injection into an agent's turn is not observability, and OpenTelemetry is not a substitute for it. But the directional signal is real, and a thread proposing a new push channel in the revision that removed the old one plausibly reads as swimming upstream. That is a better explanation of its zero comments than cold-start alone. Any revival must answer "why is this not OpenTelemetry, and why is this not a tool result?" in the first paragraph. **MCP `#3008` is unaffected.** `InitializeResult` is not deprecated. One adjacent change worth tracking: client capabilities now ride in `_meta.io.modelcontextprotocol/clientCapabilities` on each request rather than solely in the handshake, so the handshake payload is under active restructuring even though the surface survives. **Adjacent finding, not a filing.** Dynamic Client Registration is now deprecated in favour of Client ID Metadata Documents. That shifts the premise of [harn#4432](https://github.com/burin-labs/harn/issues/4432) (MCP OAuth loopback robustness, which includes DCR redirect-URI and ephemeral-port drift): hardening a deprecated registration path is worth less than it was when that issue was written. ### A2A: no deprecation risk, two corrections Checked 2026-07-25 against the current A2A specification. A2A has a formal deprecation lifecycle in Appendix A: a renamed message or field keeps its old name, marked deprecated, until the next major release. Two breaking changes are recorded there, both already known to us — the `kind` discriminator removal and the extended-agent-card field relocation. **Nothing we target is deprecated.** **`TASK_STATE_PAUSED` still does not exist.** The current enum is `UNSPECIFIED`, `SUBMITTED`, `WORKING`, `COMPLETED`, `FAILED`, `CANCELED`, `INPUT_REQUIRED`, `REJECTED`, `AUTH_REQUIRED`. There is no caller-initiated pause and no mechanism for one, so the gap `#1858` describes is intact and unclaimed after two months. **Correction to `#1857`'s premise.** The filing implies no idempotency handle exists. The spec actually says Send Message operations MAY be idempotent and that agents may use `messageId` to detect duplicates. So a handle exists; what is missing is any obligation to honour it or any specification of the dedupe window and collision behaviour. That makes the right ask considerably smaller than the filing's: **specify dedupe semantics for the existing `messageId`, rather than add a new `Idempotency-Key`.** Recorded on [harn#5540](https://github.com/burin-labs/harn/issues/5540) — it partially reopens the option A versus B decision, since "tighten what already exists" is a much easier sell than "add a field." **Watch item for `#2028`.** The actor-chain extension is declared through `AgentExtension` entries under `AgentCapabilities`. One of A2A's two recorded breaking changes relocated an extended-agent-card field, so confirm the declaration location against the current schema before any follow-up post cites it. ### ACP: no deprecation risk, and an open invitation Checked 2026-07-25 against the v2 overview RFD. `session/load` is removed in v2, with `session/resume` subsuming it via an optional `replayFrom` cursor. We already accounted for that in the 2026-07-03 realignment on `#1233`, so no rework is needed. **`session/prompt` and `session/cancel` continue unchanged in v2**, which are the surfaces the inject and suspend proposals sit beside. The v2 baseline session method set is `session/new`, `session/list`, `session/resume`, `session/close`, `session/prompt`, `session/cancel`, and `session/update`. Every one of our ACP proposals is an *addition* to a live surface rather than an extension of a deprecated one. Nothing is deprecated. **The v2 "RFDs to be Written" list now reads "MCP: tool timeouts, more lifecycle methods."** That second item is an open slot that `session/suspend` fits directly, and it is a stronger position than the thread has had. It also indicates the truncate/edit item previously on that list has been claimed, consistent with `htahaozlu` re-basing the rewind proposal onto the v2 lifecycle in the `#1261` thread. ### Net result of the lifecycle sweep One filing died (MCP `#2736`), one is at risk and needs to differentiate (MCP `#3007`), one gained a stronger framing (ACP `#1233`, which fits a named open slot), and one had its premise corrected in a way that shrinks the ask (A2A `#1857`). The remaining seven are unaffected. ## Local follow-up candidates Ordered by whether they depend on someone else moving first. **Unblocked — no maintainer required:** - **MCP `#2736`**: closed out, not filed. The target feature is deprecated. A close-out note on the thread asks whether budget semantics matter for whatever replaces Sampling; no further work otherwise. Tracked in [harn#5539](https://github.com/burin-labs/harn/issues/5539). - **MCP `#3007`**: decide whether to differentiate against the Logging deprecation or drop it. Do not revive it without answering the OpenTelemetry question. - **A2A `#2028`**: fold "per-hop `scopes` are derived from the validated credential, never authorization-bearing" into the extension text, with RFC 8693 `act` cited for the identity half only. Offered upstream on 2026-08-20; the thread is waiting on the revision, not on a maintainer. - **oauth-wg `#73`**: the draft author invited the actor-chain conversation into [`draft-mcguinness-oauth-actor-profile`](https://github.com/mcguinness/draft-mcguinness-oauth-actor-profile) on 2026-07-25. Nothing from us is there yet. Accepting that invitation is the next step, and it also decides whether the companion-profile draft we offered belongs in that repo. - **ACP `#1233`**: replied 2026-07-25 adopting the acknowledged-request shape. No follow-up until someone answers. - **MCP `#3008`**: begin auth-area sponsor outreach via the relevant WG/IG rather than waiting for the discussion to attract one. - **`#3347`**: write the IETF draft-watch note; three of five tracked drafts are still unpinned (WIMSE WIT/WPT, transaction-tokens-for-agents, `draft-klrc-aiagent-auth`). - **Audit item from the Actor Profile read**: the canonical actor identifier is the (`act.iss`, `act.sub`) pair. Anywhere our internal chain keys an actor by subject alone is a latent interop bug; check against Epic A / C under [harn#3326](https://github.com/burin-labs/harn/issues/3326). **Blocked on maintainers — hold:** - **ACP `#1261`**: keep conflict-free against upstream `main`, keep the public framing anchored in existing editor/agent behavior. Three unprompted third-party adoption reports now sit in the thread; that is the argument, and it does not need restating by us. - **ACP `#1224`**: the maintainer asked for time on 2026-07-06. Do not re-ping. - **A2A `#1858`**: draft PR stays ready-to-cut but uncut until the draft-PR-vs-extension question is answered — or until we decide to self-publish under our own extension URI. - **A2A `#2027`, MCP `#3007`**: cold with no venue warming. Leave parked or warm the venue first; no re-pings without new substance. **Standing rule:** no re-pings without new substance. Third-party feedback arriving in a thread *is* new substance; the passage of time is not. ## Not yet filed - **`session/inject_host_event`** — documented in [typed host-event injection](./acp-session-inject-host-event.md) as a shipped Harn extension, the only doc in this directory with no upstream filing and no tracking issue. It is the host-originated sibling of `session/inject`: same delivery seams, opposite initiator. Natural follow-on RFD if `#1261` lands; premature while `#1261` is unreviewed. - **MCP suspend/resume** — deliberately not filed. MCP tools are request/response with no agent-lifecycle surface to extend. Recorded so the absence is not mistaken for an oversight. --- ## Read next - [Protocol contribution RFCs](https://harnlang.com/protocol-contributions/README.md) - [ACP: `session/inject_reminder`](https://harnlang.com/protocol-contributions/acp-session-inject-reminder.md)