[lunelson]

🌟 What is the purpose of this PR?

Brunch's turns get shorter. Each change removes work the model did on every exchange without it changing the answer: a closing model call, a reread of the net, a long Ledger commit, and reflections that repeated the net. The turn-time figures below come from local persona runs measured with the run packets from #10066. This PR does not report their combined effect.

🔗 Related links

• FE-1943 (internal): shorten turn times
• Top of a stack. It sits on FE-1850, FE-1336: Explain a net element from the Ledger, on the canvas and to Brunch #10067 (FE-1850, FE-1336), which sits on FE-1943: Show where each Brunch exchange's time goes in persona runs #10066 (FE-1943); review those first.

🚫 Blocked by

• FE-1850, FE-1336: Explain a net element from the Ledger, on the canvas and to Brunch #10067, which this branch is based on.

🔍 What does this change?

• The turn ends on the closing commit. The exchange's last response carries the reply and a ledger_commit with endTurn set. Once that commit is recorded, the turn ends without another model call. A refused closing commit leaves the turn open so the model can repair it. Persona runs: the closing step, about 5.5 s per turn, is gone, and the reply streams before the commit's arguments.
• No net read at the start of an exchange. Brunch reread the net at the start of most build turns in case the user had edited it. A change against an edited net is already refused without starting, and the refusal says to read again, so the guidance now relies on that. Persona runs: build turns with a read fell from 14 of 19 to 3 of 18, about 10 s per build turn. A hand edit mid-run was refused, reread and retried.
• Moving a node no longer makes Brunch's view stale. The document revision now hashes the net without layout. Before, a hand-moved node made Brunch's next changes fail as stale, although no net read shows positions.
• Shorter claims. The claim guidance, spread over eight paragraphs, is now one Claims section in the system prompt: a claim is one fact as a short active statement, and each message decomposes into several. Persona runs: commits about 22% smaller, with the share of unconfirmed claims unchanged.
• origin and status default for what the user said. origin defaults to stated. Only a stated entry may omit status, which becomes confirmed. Any other origin without a status is refused. entity/update replaces every field, so it takes neither default: an update restates origin and status. Parsing still yields the full shape, so history, receipts and the fold are unchanged.
• Reflections give reasons. Reflections restated changes the net's names and descriptions already carry. They now say why a change was made and what its elements represent, skip tool outcomes and turns that changed nothing, use the IDs the model wrote, and name only entities their claims do not already reach.

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

• Changes only @hashintel/brunch-agent, which is private, and @apps/brunch-agent. No changeset.

📜 Does this require a change to the docs?

• apps/brunch-agent/docs/petrinaut/ARCHITECTURE.md and the system prompt and skills describe the new turn end and read guidance.

🕸️ Does this require a change to the Turbo Graph?

• Does not affect the execution graph.

⚠️ Known issues

• The time savings are measured in local persona runs of a few exchanges each. They show the direction, not a benchmark.
• Two changes rest on model behaviour, not on code: skipping the opening read, and reflections that give reasons. Tests cover the code paths; only persona runs show the model following the guidance.
• A model that sets endTurn before it has replied would end the turn with no reply. The guidance asks for the reply first; nothing enforces it.

🛡 What tests cover this?

• A commit ends the turn only when it sets endTurn and is recorded.
• Only a stated entry defaults to confirmed; other origins without a status are refused.
• Moving an element by hand leaves the model's document revision unchanged.
• CI results are on this PR.

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