回复：draft-helixar-hdp-agentic-delegation-01: chain-of-custody for agentic delegation (revision, seeking review)

Hi Alan,
Thanks for the careful read. Taking your points in order.
On well-known keys: you are right, and our claim needed scoping. delegation-v1 operates inside a single credential system: the chain root is an attestation issued to a KYB-verified operator, and every delegator and delegatee on a chain holds a credential whose key is registered with the issuer at issuance. So "every principal has a resolvable key" holds by construction within that domain — but only there. For delegation across organizations, or to a program nobody else knows a key for, your model — hold your direct delegate responsible for use of the delegation, recursively down the chain — is the more general answer. We see that accountability chain as complementary to the signature chain rather than competing with it; v1 explicitly scopes out cross-issuer chains and does not attempt the case you describe.
On "recorded, not consented": my sentence was ambiguous, sorry. I was describing HDP's single-key design, where one issuer key signs every hop. There the delegating agent signs nothing; the issuer's signature attests that the issuer recorded a delegation claim — recording, not consent. In a per-hop model — the one you describe, and ours — the delegator signs with its own key and you know exactly who consented at each hop. No disagreement there.
On losing offline verification: you caught an over-compression. Per-hop signatures lose nothing offline: given the principals' public keys, chain integrity — signatures, principal alignment, monotonic attenuation — verifies entirely offline. What is online in our design is revocation freshness: we require a fresh status credential (60-second TTL) for each principal on the chain, instead of revocation lists or delivered revocation tokens. That cost comes from wanting bounded revocation, which any revocable system pays in some form; it is not a cost of per-hop signing. The sentence should have read "accepted requiring online status checks for revocation freshness."
Glad the truncation analysis holds up.
Your detailed comments on the design doc arrived separately — thank you. We are working through them and will respond to you directly, and fold the results into the next revision.
Brigitte Qirong LI 
Jiaozi Protocol 
https://www.jiaozi.io <https://www.jiaozi.io >
------------------------------------------------------------------
发件人：Alan Karp <alanhkarp@gmail.com>
发送时间：2026年8月18日(周二) 06:11
收件人：hello<hello@jiaozi.io>
抄 送："public-credentials"<public-credentials@w3.org>
主 题：Re: draft-helixar-hdp-agentic-delegation-01: chain-of-custody for agentic delegation (revision, seeking review)
Sorry for the delay. Life got in the way.
I've put my comments inline below
--------------
Alan Karp
On Wed, Aug 12, 2026 at 9:59 PM Brigitte Qirong LI <hello@jiaozi.io <mailto:hello@jiaozi.io >> wrote:
Hi Siri, all,
We read -01 closely — two comments on the open questions, then a pointer to a complementary design we would like review on.
On question 1 (hop signing keys): this seems to depend on what the token is for. For an offline-verifiable evidence trail, the single-key default is coherent. 
You appear to be making the common assumption that every entity in the system has a well-known public key that is used to identify it. That isn't even always true within a single company. For example, you might delegate to a program you wrote. Such a program does not have a widely known key, and you don't want to give it your own key. The problem is even trickier when working across companies, where you have no direct control over how keys are assigned to parties you may wish to delegate to.
What I'm trying to say is that the single-key default is not as coherent as you may think. What does work is holding your direct delegate responsible for use of the delegation, even if the actual use came from farther down the delegation chain. In that case, your direct delegate will hold its direct delegate responsible, and so on.
For runtime authorization it seems insufficient: with one issuer key, a hop attests that the issuer recorded a delegation, not that the delegating agent cryptographically consented to it. 
I don't understand. The delegating agent signed with a secret key only it knows. Are you saying that you don't know who that agent is with per hop keys? 
We took the other branch of your trade-off — per-hop signatures by each delegator's own key — and accepted losing offline verification.
Why does that choice lose offline verification?
On question 2 (truncation): from the capability side, if the verifier requires the chain to terminate exactly at the authenticated presenter — as UCAN Invocation ("ending at the invoker") and ZCAP's capabilityInvocation proof already require — deleting trailing hops gains an attacker nothing: authority only narrows toward the tail, so a truncated prefix is only usable by the delegatee of its last remaining hop, who legitimately holds that authority anyway. A signed chain-length commitment may therefore be unnecessary for authorization; completeness stays an audit question, where your out-of-band suggestion looks right.
That sounds right. 
We have published a design (design only, no implementation yet) that is roughly the capability-layer complement to HDP's provenance layer: per-hop independent signatures, MUST-level monotonic attenuation (capabilities ⊆ parent, caveats grow-only, expiry shrink-only, unknown caveat rejects the chain), chains rooted in a KYB-verified entity's attested behavior boundary, and revocation via 60-second-TTL status credentials — bounded mid-chain revocation, cf. your §10.6. Deviations from UCAN/ZCAP are declared per clause:
https://github.com/jiaozi-protocol/jiaozi-app/blob/main/standards/delegation-v1/DESIGN.md <https://github.com/jiaozi-protocol/jiaozi-app/blob/main/standards/delegation-v1/DESIGN.md >
Feedback is very welcome, including "use X instead".
I'll respond separately. 
Thanks, 
Brigitte Qirong LI 
Jiaozi Protocol
https://www.jiaozi.io <https://www.jiaozi.io >