84a6bae1c7
The branch control on user and consumed-steering bubbles could enable only when a completed turn ended with no node after the message at all, so readers saw a permanently unavailable control whose tooltip promised a state it could not reach. An enabled one would mislead anyway: a fork at a message seq cuts at the containing turn/end and takes the answer along, the opposite of the branch-to-re-ask reading a control on one's own bubble suggests. MessageItem loses its fork props, PendingSteeringBubble loses the showBranch special case, and messageBranchSeqs narrows to assistantBranchSeqs: only a completed turn's transcript tail that is the turn's own content-text assistant may fork. A steered turn keeps its fork point under the settled answer, because fork is a log-prefix cut and the steer is model-visible history the child inherits. Web aria goldens drop the user-bubble disabled-branch row and its hidden explanation text; the nested-subagent golden also loses the one enabled user-tail fork handle, a loss the decision note accepts.
3.3 KiB
Agent Note: User and steering bubbles drop the branch action
Status: implemented
English | 中文
Problem
Every user and consumed-steering bubble rendered the branch control under the completed-turn-tail gate of the completed-turn-tail decision. On those bubbles the gate is effectively permanent: a turn-opening user message is followed by its own turn's nodes, and a consumed steering message is mid-turn by construction, so the control could enable only when the turn ended with no node after the message at all — a cancel before the first model event. Readers therefore saw a control that never enables, with a tooltip promising a state the button cannot reach. The affordance also misled when read at all: a fork at a message seq cuts at the containing turn/end, so "branch at my message" includes the answer below it — the opposite of the branch-to-re-ask reading a control on one's own bubble suggests.
Decision
User and steering bubbles render no branch action. MessageItem loses its fork props, PendingSteeringBubble loses its showBranch special case, and messageBranchSeqs narrows to assistantBranchSeqs: only a completed turn's transcript tail that is the turn's own content-text assistant may fork. The branch affordance lives solely under the settled answer.
A turn containing a steer keeps its fork point unchanged: fork is a log-prefix cut at turn/end, and the steer is model-visible history the child must inherit, so the settled answer of a steered turn forks like any other. The assistant-side gate and its visible-but-unavailable presentation are also unchanged — under an answer, unavailable is a transient, reachable state (a trailing tool or error row currently owns the tail), which is exactly what the tooltip is for.
Alternatives considered
Hide the control on message bubbles only while ineligible. Rejected: it preserves the near-unreachable enabled case at the cost of an icon that appears on one's own bubble only when a turn died before producing anything, an inconsistency not worth the case it serves.
Keep the visible-but-unavailable control (status quo). Rejected: the completed-turn-tail decision chose visibility so the tooltip could explain a boundary the reader can reach; on user and steering bubbles the boundary is unreachable in practice, so the explanation props up a control that should not exist there.
Branch-before-the-message semantics on user bubbles. Out of scope: re-asking from one's own prompt needs a cut before the message plus composer prefill, a different Host operation. Removing the current control keeps that seat free for such a feature instead of squatting on it with opposite semantics.
Consequences
The only fork handles are the enabled branch controls under settled answers. A turn cancelled before any node followed its message loses its only handle and has no fork point, matching turns whose tail is a content-free interrupted node. Web aria goldens across apps/web drop the user-bubble disabled-branch row and its hidden explanation text. Package tests pin that user and steering bubbles render no branch control and that a steering-tail turn leaves the narration's control unavailable.