[TheFabFab]

Two fork changes for DocuMentor's first prompt in a new chat (design: docs/superpowers/specs/2026-10-11-first-prompt-stable-ids-design.md in TheFabFab/KPG, F4 and F5).

F4: create a session under the id the client names

• ACP newSession passes _meta.opencode.sessionId (prefix ses) to session.create as id. Session.CreateInput and Session.create take an optional id.
• An id that names an existing session is refused, and that session is left as it was. The projector already refused a duplicate row (onConflictDoNothing then SessionAlreadyProjected); create checks first so the error names the id.
• ACP clients that send no _meta, or an id without the prefix, keep opencode-minted ids.
• The generated v2 SDK gains id on session.create (packages/sdk/js/script/build.ts, no hand edits).

Why: DocuMentor shows a new chat as a temporary new-… thread until session/new answers (~3.5 s on a cold spawn), then switches to ses_…. With the id chosen up front the chat has its final id from the first keystroke.

F5: store a user message and its parts in one transaction

• Session.saveMessage publishes a message and its parts inside one db.transaction, the same pattern Session.patch uses. createUserMessage uses it.

Why: each part was its own commit. On Postgres, DocuMentor's catch-up read a user message between the commits and saw only its <system-message> context part; the user's text disappeared from the live chat until a reload (production bug report 2026-10-11-19-31-37-831-snapshot).

Tests (documentor: …)

• test/acp/service-session.test.ts: the _meta id is used; no _meta or a UUID gets a minted id.
• test/session/session.test.ts: create under a chosen id; an existing id is refused and the session keeps its title; saveMessage stores every part; a part that cannot be stored leaves no message row. That last test fails without the transaction (checked by removing it).

Run locally against Postgres 18: service-session 47/47, session 12/12, httpapi-session 21/21, httpapi-instance 7/7. prompt.test.ts 61/62: cancel finalizes interrupted bash tool output through normal truncation fails in a full-file run with and without this change, and passes alone. Typecheck shows the same 14 errors before and after (they come from installing with --ignore-scripts here).

Release after merge: tag v1.18.34-documentor-pg.4, then bump the digest pin in DocuMentor's Dockerfile and Dockerfile.dev.

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[github-actions]

Hey! Your PR title A client-named session id, and a user message stored in one transaction doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

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