@hongminhee Yes, it should be able to verify proofs with injected @context. But it is not injected. Here' the Announce activity, for example:
{ "@context": [ "https://www.w3.org/ns/activitystreams", "https://w3id.org/security/data-integrity/v1", { "Emoji": "toot:Emoji", "Hashtag": "as:Hashtag", "sensitive": "as:sensitive", "toot": "http://joinmastodon.org/ns#" } ], "actor": "https://hollo.social/@fedify", "cc": [ "https://fosstodon.org/users/hongminhee", "https://hollo.social/@fedify/followers", "https://fosstodon.org/users/hongminhee" ], "id": "https://hollo.social/@fedify/01905d94-a20b-7722-94d1-576817dd3b00#activity", "object": "https://fosstodon.org/users/hongminhee/statuses/112692842178962546", "proof": { "created": "2024-06-28T06:58:47.16192715Z", "cryptosuite": "eddsa-jcs-2022", "proofPurpose": "assertionMethod", "proofValue": "z4xV1JV4JFuoPcLBNBTDbkceyPdd3YGWdFU4oawZDX5qSxiKeJgjFMf3uwf71QCfNUmJay66g9556K6NjUUUxZu1g", "type": "DataIntegrityProof", "verificationMethod": "https://hollo.social/@fedify#key-2" }, "published": "2024-06-28T06:42:20.3Z", "to": "as:Public", "type": "Announce" }