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platform/docs/opencode-serve-migration-plan.md
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pastilhasandClaude Opus 5 38ebe168f0 retire two phantom gaps, and plan the migration
Crash-recovery state is not a gap: state:sync goes to the proxy capability and carries
proxySecret, and syncState/getCachedState have no callers at all. The row compared opencode
against a mechanism officer never consults. The real recovery story now exists and is better
— a sidecar restart stops in-flight turns and writes the reason to chat_session_events.

Identity is deferred, not forgotten: TODO.md already records it, and chat is kind execution,
which the grants API refuses to share at any level, so no member can reach it.

Also adds the serve migration plan, written while the facts are fresh and nothing is on
fire. It leads with the five things that will bite whoever implements it — per-request
location, the data wrapper, delivery defaulting to steer, silent failure on an unconnected
credential, and the session.next event names — because none of them are in the API docs and
each cost time to find today.

Phased so the old path stays one config flip away, and so warm-session lifetime (idle GC,
orphan adoption, the supersede race) is imported deliberately rather than discovered.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-10 18:27:23 +01:00

5.3 KiB

Moving OpenCode turns onto the serve — the plan

Written 2026-08-10, after the fork was unblocked (docs/opencode-fork-decision.md). Nothing here is implemented. It exists so the work can start from verified facts rather than from the API docs, which have been wrong or misleading three times on this path.

Andre should read "What changes for the user" and "The risk I would not take blind" before this starts.


What we are moving from and to

Today every turn is opencode run --dir <cwd> --format json, a subprocess with stdin: 'ignore'. It works, it is verified end to end, and its limits are all consequences of that one closed pipe.

The serve's /api/session/* surface offers, and I have run each of these against 1.18.16:

Capability How Verified
Mid-turn injection POST /prompt {delivery: "steer"} yes — steered a running turn
Queue behind a turn POST /prompt {delivery: "queue"} yes — "ONE" then "TWO", no errors
Token streaming GET /eventtext/event-stream yes — text.started/text.ended observed
Reconnect + replay same, ?after=<seq> yes — replayed a finished session
Interrupt, session lives POST /interrupt → 204 endpoint only, not exercised
Model selection POST /model → 204 yes — runs on the chosen model
Images prompt.files not exercised (we have images via --file already)

Facts that will bite whoever implements this

Each of these cost time to find. None is in the API docs.

  1. The location is per REQUEST, not per session. x-opencode-directory: <cwd> header, or ?location[directory]= as a deepObject query. A session created with location in the body and then prompted without the header does not behave.
  2. Responses wrap in {"data": …} on this surface; the legacy /session/* returns bare objects. Reading body.id instead of body.data.id yields undefined silently.
  3. delivery defaults to "steer". Omitting it injects into a running turn, which is NOT the safe default for an ordinary "send" — it must be set explicitly per intent.
  4. A model with no connected credential fails silently. Prompt admitted, prompt.admitted and prompted emitted, then nothing, forever. The sidecar now connects the credential at boot (connect-credential.ts), and this failure mode is why that exists.
  5. The event names are session.next.*step.started, text.started, text.ended, tool.called, tool.success, step.ended, step.failed. Not the shapes mapRunLine handles.

Shape of the work

Phase A — read the stream without depending on it. Add a serve-based reader alongside the existing runner: subscribe to /api/session/{id}/event, map session.next.*ChatEvent, and prove the mapping against real turns. Do not route any user traffic through it. This is where mapRunLine's successor gets written and tested, and it is the only phase with no user-visible risk.

Phase B — turns through the serve, behind a switch. POST /prompt for the turn, events from Phase A, POST /interrupt for stop. Keep opencode run reachable by config so a bad day is one restart from the known-good path. The switch is the deliverable, not a detail.

Phase C — the capabilities that motivated it. delivery: "steer" wired to the existing "send now" button, delivery: "queue" to the queue, streaming deltas to the composer. These are the visible wins and they are cheap once B holds.

Phase D — retire the subprocess, only after B has run for a while. Deleting it early converts every future problem into an emergency.

What changes for the user

Better: text appears as it is generated instead of in blocks; the queue and "send now" work on OpenCode exactly as they do on Claude; stop interrupts without destroying the session.

Worse, potentially: the serve becomes load-bearing. Today a serve crash costs session listing and nothing else, because turns are subprocesses. After this it costs every turn in flight. That trade is the whole decision.

The risk I would not take blind

Warm sessions bring a lifetime problem OpenCode does not currently have. A subprocess ends when the turn ends; there is nothing to garbage-collect, adopt after a restart, or leak. A serve session persists, so this migration imports the entire class of problems the Claude path spent months getting right — idle GC, orphan adoption, releasing versus killing, the supersede race I fixed this morning.

That is not an argument against doing it. It is an argument for Phase B keeping the old path one config flip away, and for not doing Phase D on the same day as Phase B.

Where to start

Phase A, runner.ts's sibling, with the session.next.* fixtures captured from a real turn rather than hand-written — docs/opencode-fork-decision.md records how to drive one with plain curl, and runner.test.ts is the pattern for pinning a mapping without spawning anything.