/linkedin-reply-handler

LinkedIn Comment Threading Rules

Two-level flattening

LinkedIn's UI shows replies two levels deep. Every reply, no matter how many logical turns into a conversation, is stored with parentComment pointing to the TOP-level comment.

Post (urn:li:activity:P)
│
├─ Comment A (id: 111)             ← top-level
│    parentComment: none
│    URN: urn:li:comment:(urn:li:activity:P, 111)
│
│  ├─ Reply B (id: 222)             ← 2nd-level
│  │    parentComment: urn:li:comment:(urn:li:activity:P, 111)
│  │
│  └─ Reply C (id: 333)             ← STILL 2nd-level (under Comment A)
│       parentComment: urn:li:comment:(urn:li:activity:P, 111)
│       (NOT under Reply B, even if logically C replies to B)
│
└─ Comment D (id: 444)             ← top-level
     parentComment: none

Posting rule

When calling POST /linkedin-comments with parentComment:

• If you're replying to a top-level comment → parentComment = that comment's URN
• If you're replying to a 2nd-level reply → parentComment = the TOP-level comment's URN (walk up the tree)
• If parentComment is omitted, the comment posts as top-level

Why this matters

Wrong parentComment URN causes one of these:

• 400 Bad Request (some posts reject it outright)
• Comment silently posted under the wrong parent (user sees it in the wrong place)
• Comment gets orphaned if the 2nd-level URN is rejected

Deriving the TOP-level comment URN

When given a 2nd-level reply's URN, fetch the post's comment tree and walk up:

def find_top_comment_urn(post_urn: str, comment_id: str, post_comments: list) -> str:
    for top in post_comments:  # each element is a top-level comment dict
        if top["id"] == comment_id:
            return f"urn:li:comment:({post_urn},{comment_id})"
        for reply in top.get("replies", []):
            if reply["id"] == comment_id:
                return f"urn:li:comment:({post_urn},{top['id']})"
    raise ValueError("Comment not found in tree")

URL formats the skill accepts

Direct top-level comment permalink:

https://www.linkedin.com/feed/update/urn:li:activity:P?commentUrn=urn%3Ali%3Acomment%3A%28activity%3AP%2C111%29

Reply permalink (notice replyUrn query):

https://www.linkedin.com/feed/update/urn:li:activity:P?commentUrn=urn%3Ali%3Acomment%3A%28activity%3AP%2C111%29&replyUrn=urn%3Ali%3Acomment%3A%28activity%3AP%2C222%29

When replyUrn is present, that's the specific comment being replied to (for reactions). The commentUrn is already the top-level parent.

Reaction targets

Reactions can be placed on:

• The post itself (post_urn passed to create_reaction)
• Any comment or reply (pass the comment's URN as post_urn — yes, confusingly named)

Default flow: react on the specific comment being replied to. Never skip the reaction — a pure reply with no reaction reads as transactional.