feat(chat): read an OpenCode pane as a conversation

[Ploppy3]

Closes #538

Change

An OpenCode pane had no native chat: herdr already reports its session (agent: "opencode", agent_session: {kind: "id", source: "herdr:opencode", value: "ses_…"}), but the conversation endpoint answered {"source":"scrollback","turns":[]}. This adds a transcript adapter for OpenCode, so the chat reads the session itself.

Where the store is (checked against OpenCode 2.0.24). OpenCode 2 keeps every session in one SQLite database, written by its background service (opencode serve --service), not by the TUI in the pane. Its path follows the rules opencode debug paths prints: $XDG_DATA_HOME/opencode/opencode.db, else ~/.local/share/opencode/opencode.db, and OPENCODE_DB (relative to the data dir, or absolute; :memory: is no store). The service is started with the user's environment, so the server's environment finds it; the pane's process environment would not. A conversation is the session_message rows of the session (seq orders them, type + JSON data); session_v2 holds the session and a staged /undo. OpenCode 1.x wrote session/message/part instead, and 2.0 copies those into session_v2 when it migrates; a store without session_v2 keeps the terminal.

New: server/opencode.ts

• Binding: the pane's agent_session from the snapshot, only when herdr's integration reported it (source: herdr:opencode), of kind id, with an id matching ses_[A-Za-z0-9]+. No cwd guess. At OpenCode's home screen there is no session, so the terminal stays.
• Reading: the database is opened per request with readonly and create: false (a missing path is never created), with a 250 ms busy timeout, and closed again. Every query is parameterized.
• Platforms: nothing here is Linux-only.
  • OpenCode's data dir has no per-platform branch (XDG_DATA_HOME || ~/.local/share, plus /opencode, on macOS and Windows too), and the server resolves it with the same os.homedir() and path rules.
  • On macOS Bun uses Apple's own SQLite, which can predate octet_length (3.43) and need not include JSON1. So a row's size falls back to length(CAST(data AS BLOB)) when octet_length is missing, and the settings are parsed in JS instead of with json_extract.
  • A Windows shell's CRLF is trimmed from a ! command's output.
  • No /proc, process environment or shell is read.
• Rows to turns:
  • Prompts show metadata.displayText when present, plus their pasted images (inline base64 only: an attachment by path is never followed) and a chip for each skill the prompt mentions.
  • A model step is a row of its own, so consecutive steps merge into one assistant turn until OpenCode's idle row or a step that finished with stop. Reasoning becomes thinking; tool calls carry their output, their error, a non-zero shell exit, the skill tool's chip, the query of a web search, and the pictures a tool returned.
  • Outputs are cut like the other agents' and fetched whole through the existing /api/pane/conversation/tool-output route (ref <message id>:<place in its content>). Images go through /api/pane/conversation/image (ref opencode:<message id>:<nth image>).
  • A command run with ! is a notice ($ cmd plus its output). OpenCode echoes that command to the model with the next prompt, and the echo is skipped. A background job's or subagent's result, or a restart notice, is a notice that starts its own turn. A completed compaction is the compaction card. Instructions, agent and model switches stay out.
  • An error is shown as Error: …, except Esc's aborted.
• Metadata: model and reasoning variant (default reads as none) from the latest step or /model switch. The context ring counts input + output + reasoning + cache.read + cache.write of the last step with usage, unless a compaction came after it. That is OpenCode's own footer figure; it matched the TUI exactly in live checks (3.8K, 4.7K, 4.6K after /undo). No window is stated: OpenCode Go's models are not in its models.json cache.
• Paging: cursors name a seq instead of a byte offset. Otherwise the pages follow the JSONL readers' rules: 50 prompts, a 16 MB window measured with octet_length (which does not read the rows), a newest page that may start mid-turn, older pages that reach back up to four windows, and before/since/from with 409 for a foreign cursor.
• History id and caching: the history id changes while an /undo hides rows (session_v2.revert). Once the next prompt deletes them, any cursor naming a deleted row is refused with 409, checked in the store itself, so it holds after a restart. A chat whose pages reach the deleted turns always holds such a cursor, because the deletion runs from the undone message to the end, so it reloads; pages before the undo stay. An unchanged session answers from memory, which keeps the ETag / 304 path working. While a step streams in place, only the rows whose time_updated moved are parsed again.

server/conversation.ts:

• Routes agent === "opencode" to the adapter.
• Adds opencode-transcript to RecognizedConversation["source"]. The byte-stream helpers are typed with StreamSource (the union without it), so a database is never handed to a file reader.
• Wires the image and tool-output routes, and adds forgetOpencodeState() to forgetTranscriptState().

shared/protocol.ts: ConversationResponse.source gains "opencode-transcript". The client already treats every source but scrollback as a conversation, so src/ needs no change.

Docs: the supported-agents table in docs/guide.md, the agent lists in the four READMEs and site/index.html, server/AGENTS.md's chat-lens row, and a CHANGELOG line under Unreleased.

Not in this PR (left for later, as the issue says): prompt cards for OpenCode's permission and question prompts, and OpenCode's slash commands in the palette.

Validation

• bun run generate:types --check, bun run typecheck, bun run build: pass.
• bun run test:unit: 1530 pass, 0 fail. New server/opencode.test.ts (23 tests): store paths, binding, every row type above, paging (pages meet exactly, since, from, foreign cursors), /undo staged and committed (including a cursor into deleted turns on a cold read), the in-place streaming cache, a 1.x store / a missing file (not created) / a non-SQLite file, page starts with a small window, tool output and images by ref, including another session's message and one an /undo hid, and the byte-size fallback. Paths are built with the platform's path module and every database is closed before the temp dir is removed, so the file also runs on macOS and Windows. The fallback was also run end to end against the real store by forcing the octet_length probe to fail: pages, stitching and metadata were identical.
• bun run test:integration: 235 pass, 0 fail across 22 files. New server/opencode.contract.test.ts (4 tests) on a real herdr: a stand-in opencode process holds the pane, the session is reported the way herdr's OpenCode integration reports it, and the server is handed a store of the test's own through createServer({ opencodeDb }). It covers the conversation over HTTP with 304, paging and 409, tool output and image over their routes, and a session the store does not hold falling back to scrollback.
• bun run test:ui: 78 pass, 0 fail.
• bun run build:site: builds.
• Live, OpenCode 2.0.24 with DeepSeek V4.1 Flash (OpenCode Go) in an isolated herdr session (herdr-web-ui-test-oc, herdr 0.9.3), with a server of its own and a temporary state dir:
  • Prompts sent from the chat composer reached the TUI and came back as folded turns ("Worked for 4s · 1 edit · 1 command", "Ran …", "Read …"). A slow sleep 8 showed "Working…" live, a tool's PNG loaded through the image route, a ! command showed as a notice with no duplicate echo, and a background subagent's result showed as its own notice, with the answer after it as a new turn.
  • /undo hid the turn and changed the history id. The next prompt committed it, and the client reloaded the history.
  • Read-only against the real store (1.7 GB, about 2,000 sessions): a 133 MB session's newest page took 44 ms cold and about 1 ms when unchanged. Walking every older page of a 158-prompt session gave exactly the turns of a whole-session parse. On the byte-bound sessions the parts matched exactly, with turns split only where a page starts mid-turn, as with the JSONL readers. In the browser that session paged back through three before pages to "beginning of conversation".

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📝 Summary

Summary by CodeRabbit

• New Features
  • OpenCode 2 conversation history is available in the chat pane, including prompts, replies, images, skills, tool activity, commands, subagent and background results, and compactions. Turns reverted with /undo are omitted.
  • Context usage appears in the message box. OpenCode’s home screen and version 1.x sessions continue to display as terminal text.
• Documentation
  • Updated supported-agent listings and guides to include OpenCode.

Walkthrough

OpenCode 2 sessions can now provide pane conversation transcripts through a read-only SQLite reader. The server supports paging and tool-output and image references. Feature descriptions and documentation now list OpenCode.

Changes

OpenCode transcript support

Layer / File(s)	Summary
Resolve sessions and convert records server/opencode.ts, server/opencode.test.ts	The reader resolves the OpenCode database path and pane session ID. It converts supported rows, including prompts, assistant content, tools, images, skills, notices, and compaction summaries, into conversation turns. Tests cover path resolution and record conversion.
Read and page session history server/opencode.ts, server/opencode.test.ts	The reader opens SQLite stores read-only, applies staged undo boundaries, tracks history and cache state, and returns paginated turns with metadata and cursor information. Tests cover pagination, history changes, cache updates, and unavailable stores.
Route conversations and references server/conversation.ts, server/index.ts, server/opencode.contract.test.ts, shared/protocol.ts, server/AGENTS.md, CHANGELOG.md, README*.md, docs/guide.md, site/index.html	The server routes OpenCode sessions to the database reader and serves validated tool-output and image references. Contract tests cover endpoint responses, paging, references, and scrollback fallback. Documentation and feature descriptions now list OpenCode support.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Feature · Severity of issue fixed: Medium

Suggested reviewers: devswha

Merge Risk: 🟡 Moderate · up to 63f57

Chat can miss OpenCode streaming updates until another message row changes. Fix cache invalidation before merging native transcript support.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 63f57

The integration is read-only and preserves existing access controls. No access-control bypass was established. Remaining uncertainty concerns whether cached conversations consistently reflect live edits and undo, especially during concurrent updates.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The demonstrated exposure is OpenCode history and referenced content for sessions bound to selectable panes on the server. Existing authorized drive and watch clients can read these routes; the boundary is server-level pane access, not a new per-session tenant authorization model.

Trust Boundaries and Controls

• observed — The existing central access gate remains before conversation route dispatch. The base-to-head route changes only pass server-configured opencodeDb; they do not expose database paths or session IDs as HTTP parameters or change watcher restrictions.
• observed — Session and message IDs are validated, and referenced tool or image rows are queried using both message ID and the resolved session ID. Images accept only inline data with an allowed raster media type; attachment paths and remote URLs are not followed.

Resilience and Maintainability Implications

• observed — Connections are closed in finally, lock waiting uses a 250 ms busy timeout, and caches have entry limits. The page byte window is not a strict allocation ceiling: an oversized whole row can be selected, and referenced content is parsed before tool-output truncation or image decoding.

Hardening Proposals

• proposed — Establish a versioned producer/consumer freshness contract, including data-only rewrites. Consider a coherent read snapshot and an explicit stale-response policy during lock recovery so undo and streaming behavior are predictable.
• proposed — Consider explicit row and decoded-image size limits before materializing stored content, to strengthen failure containment beyond nominal page windows and response truncation.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 45 functions across 6 files. (4 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Issue #538 requires native OpenCode transcripts bound to herdr's reported session ID, read-only store access, transcript mapping, and terminal fallback when no session resolves. The PR adds the OpenCo…
Out of Scope Changes check	✅ Passed	The adapter, routing, protocol update, tests, documentation, and changelog directly support the OpenCode chat objective in #538. No unrelated change is established by the supplied scope evidence.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding OpenCode pane conversation support.
Description check	✅ Passed	The description includes the required Change and Validation sections. It explains the problem, resulting behavior, implementation scope, limitations, test results, contract-test coverage, and live val…

Full details: Docstring Coverage

Explanation

Docstring coverage is 75.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 45 functions across 6 files. (4 skipped: 4 unsupported.)

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Actionable comments posted: 1

🔇 Additional comments (1)

server/opencode.ts (1)

413-418: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

⚠️ Unverified finding
Verification ran but could not confirm this finding. It is shown for review, not as a verified issue.

Scope the newest-page data lookup to the session.

The prepared statement on Line 413 selects by id only. Every other row read in this file also binds session_id. The current loop only passes ids that META returned for sessionId, so the statement cannot return a foreign row today. A shared opencode.db holds every user session, so keep the session scope explicit. Binding session_id here also matches sessionRow.

Proposed fix

-        const data = db.query<{ data: string }, [string]>("SELECT data FROM session_message WHERE id = ?");
+        const data = db.query<{ data: string }, [string, string]>("SELECT data FROM session_message WHERE id = ? AND session_id = ?");
 ...
-            const found = data.get(row.id);
+            const found = data.get(row.id, sessionId);

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Inline comments:
Review comments at @CHANGELOG.md:
- Around line 11-17: Update the OpenCode changelog entry to end with the PR link
for #543; if the contributor is not @devswha, add their GitHub login after the
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⚠️ Outside diff range comments (1)

🟡 Minor · Rotate the history ID on a cold read of a non-empty session. · opencode.ts:322-331

server/opencode.ts:322-331
🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Rotate the history ID on a cold read of a non-empty session.

If a committed /undo is first read after restart or LRU eviction, previous is absent and the code can reuse the pre-undo ID. A page boundary can split an assistant turn, leaving its undone rows in ChatView’s retained older turns. Since ChatView keeps those turns when the ID matches, the deleted content can remain visible. Assign a fresh generation when previous is absent and stats.last is non-null.

Suggested fix

--- a/server/opencode.ts
+++ b/server/opencode.ts
@@
-  let generation = previous?.generation ?? "";
+  let generation = previous?.generation ?? (stats.last === null ? "" : `-${randomUUID().slice(0, 8)}`);

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Review comment at @server/opencode.ts around lines 322 - 331:
Update the generation fallback in the history ID construction so a cold read of
a non-empty session gets a fresh generation when `previous` is absent, while an
empty session keeps an empty generation. Preserve the existing generation when
history is present.

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Outside diff comments:
Review comments at @server/opencode.ts:
- Around line 322-331: Update the generation fallback in the history ID
construction so a cold read of a non-empty session gets a fresh generation when
`previous` is absent, while an empty session keeps an empty generation. Preserve
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[devswha]

Thanks for this. I read the whole diff and ran it locally at 146903e. I found no failing scenario that blocks the merge. There is one correctness assumption I could not confirm, one rule point, and a few small notes.

Correctness

1. server/opencode.ts:385-391 (cursorOf), with server/opencode.ts:318 (the history id). After a committed /undo the history id returns to opencode-<session>, the same as before the undo. The only thing that makes a chat drop its stale older pages is the "does the cursor's row still exist" check. That is sound only if OpenCode never hands out a deleted seq again, as the file header says.

   • I reproduced the dependency. With a writer that reuses seq (delete from an undone prompt below the held start, then append rows at the freed numbers until the held cursor's seq exists again), a cold from=<held cursor> returns a page instead of 409. The client keeps older pages whose last prompts were deleted.
   • Whether OpenCode 2 can reuse a seq is unverified on my side: I only have 1.17.15 installed and did not read the 2.x writer.
   • Could you point to where 2.0.24 assigns seq? If it is max(seq) + 1 per session, the id needs something the deletion changes. If it is monotonic, a one-line note of where that is guaranteed is enough.

2. server/opencode.ts:291-293 (unusable) and :478-479, :508-509. Any SQLite error other than "no such table/column" or SQLITE_NOTADB is rethrown, and the route answers it as a 500.

   • Repro: a store in rollback-journal mode with a writer holding BEGIN EXCLUSIVE makes opencodeConversation throw database is locked (SQLITE_BUSY) after 252 ms.
   • A WAL store with an open write transaction reads fine, so this does not happen if OpenCode 2 always runs its store in WAL. Whether it does is unverified.
   • If a busy store can occur, keeping the last answer or falling back to the terminal would be kinder than an error in the chat. Not blocking.

Rules

3. server/conversation.ts:857 calls opencodeDatabasePath() with no argument, so the store is found from process.env only. server/opencode.contract.test.ts:58 therefore sets process.env["OPENCODE_DB"] for the whole test process and restores it at :82.
   • AGENTS.md says createServer(options) is the only injection seam, with the environment as the fallback for an unset option. codexHome is the precedent here: it is passed through paneConversation, conversationImage and toolOutput.
   • Please add an option (for example opencodeDb) and pass it the same way, so the contract test does not mutate the environment. The contract lane runs files in parallel shards, and a process-wide variable is the kind of thing that leaks between them. I have not seen it leak; this is unverified as a failure and is a rule point only.

Smaller notes

4. server/opencode.test.ts:386 ("measures a row in bytes without octet_length too") checks that SQLite's length(CAST(data AS BLOB)) equals the UTF-8 byte length. It never runs the fallback branch at server/opencode.ts:397-403: rowSize is module state that is set once and that forgetOpencodeState() does not reset. So the macOS path is covered only by the manual run described in the PR body. A small seam, such as passing the size expression into the query builder, would let the test page a store through the fallback. I confirmed this by reading the test.

5. server/opencode.ts:68-72 (opencodeSessionId) checks agent and kind but not source. The file header and the PR body say the pane is bound by herdr's herdr:opencode report. I confirmed that { agent: "opencode", kind: "id", source: "something-else", value: "ses_abc" } is accepted. Either check source === "herdr:opencode" or drop the claim from the comment.

6. docs/guide.md:139 says the path is ~/.local/share/opencode/opencode.db "on Linux, macOS and Windows alike". Unverified on my side: I could only check Linux.

7. I did not run server/opencode.contract.test.ts locally, because it needs a live herdr. CI's integration lane has to cover it.

The two CodeRabbit comments

• "Scope the newest-page data lookup to the session": no longer applies. Since fe95cbf, every row read by id binds session_id (server/opencode.ts:331, :448 and :487).
• "Rotate the history id on a cold read of a non-empty session": does not hold at the head commit. The generation code it refers to is gone. I ran the scenario it describes:
  • 80 prompts, with the chat holding the newest page's cursor and one older page.
  • A committed /undo of a prompt inside the older page, then a new prompt.
  • All in-memory state forgotten, then from=<held cursor>.
  • The history id is unchanged (opencode-ses_x), but the answer is history_changed, because the cursor's row was deleted. ChatView drops its older pages on the 409.
  • An undo that starts after the held cursor leaves the older pages untouched, which is correct: they hold only rows before the cursor.
  • The one way this breaks is note 1 above.

What is good

• The store is opened read-only with create: false, per request, and every query is parameterized and scoped to the session. A missing path is not created (covered by a test).
• A real OpenCode 1.17.15 store on my machine answers transcript_missing, so the pane keeps the terminal as the PR says.
• A WAL store whose -wal and -shm files are gone (the service stopped cleanly) still opens read-only and pages correctly.
• StreamSource keeps the database out of the byte-stream readers at the type level, and forgetTranscriptState() clears the new caches.
• No new endpoint or WS frame, so site/demo/transport.ts needs no answer. src/ is untouched, so there are no new i18n strings or CSS.
• The changelog entry has the PR link and by @Ploppy3 in the required form.
• The contract test creates its own workspace (with focus: false, through workspaceCreate), uses a temp stateDir and port: 0, and waits with a bounded poll.

Merging on v0.4.0

• The branch conflicts with v0.4.0 in CHANGELOG.md only. docs/guide.md auto-merges.
• The conflict is real work, not just a marker cleanup: the PR's entry sits in what is now the released ## [0.4.0] section (CHANGELOG.md:17 at the head). It has to move under ## [Unreleased] / ### Added, and the 0.4.0 wording of the "Sidebar rows" entry has to be kept.
• On the merged tree (with the changelog conflict left as is), tsc --noEmit passes and the two unit files pass, 71 tests.
• At the PR head, bun run check fast passes here: all five steps ok, unit suite 1670 pass, 4 skip, 0 fail.

[Ploppy3]

Thanks for the thorough review. All addressed in 63f57a1:

1. seq is never reused. In 2.0.24 a row's seq is its event's durable.seq (appendMessage inserts seq: event.durable.seq). Bus.publish takes event_sequence.seq + 1 under a per-session lock in a transaction, and Bus.reserveSequence only raises it (max(seq, i)). The revert commit deletes session_message/session_inbox rows without touching event_sequence. Live check: rows from seq 112 were undone, and the next prompt got 127. The file header now says where this is guaranteed.
2. OpenCode's storage layer sets PRAGMA journal_mode = WAL itself, so this should only occur during recovery. It's handled anyway: a busy store keeps that page's last answer, else falls back to the terminal for one poll (store_busy). A test reproduces your rollback-journal case.
3. Added createServer({ opencodeDb }), threaded through paneConversation/conversationImage/toolOutput like codexHome. The contract test no longer touches process.env.
4. The size expression is now a parameter (OPENCODE_ROW_SIZE). A test pages an 18 MB session through both and gets identical cursors and turns.
5. opencodeSessionId now requires source === "herdr:opencode".
6. OpenCode's v2 docs give ~/.local/share/opencode/opencode.db for macOS/Linux, and its v1 docs give %USERPROFILE%\.local\share\opencode for Windows. 2.0.24's path code has no platform branch. The guide now names the Windows path instead of "alike".
7. Passes locally on an isolated herdr (bun run check full: all steps ok, the OpenCode contract test included).

Also merged v0.4.0: the entry moved under [Unreleased], and OpenCode's caches now join forgetPaneTranscriptState, as the refreshed server/AGENTS.md requires.

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Review comments at @server/opencode.ts:
- Around line 432-510: Update opencodeConversation’s cache validation to
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• docs/guide.md

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[devswha]

Reviewed and updated against latest main 90b01f8 (#610). Current reviewed head: 3883e21.

Changes pushed to this PR:

• 1a6ec38: merged main, resolved the README/site conflicts without dropping the new domain/copy, and kept the newly added Chinese site in sync with OpenCode 2 support.
• 3883e21: fixed immutable caching of mutable OpenCode image refs. Parallel tool completions can change the bytes behind an ordinal image ref; these responses now use private, no-store, with an HTTP regression covering the reorder.

Verification on the combined branch:

• bun run check fast: passed; 1,918 unit tests passed, 6 skipped. Existing Vite large-chunk warning remains.
• bun run build:site: passed.
• Isolated OpenCode + Codex + API contracts: 106 passed, including the new image-cache regression.
• Codex binding contracts also passed in the preceding adjacent-route run.

No remaining merge-blocking code findings. Existing review threads are resolved. Both latest-head fork workflow runs were approved after reviewing their execution safety. Required remote CI, including Integration and browser, is still running: this approval is not a claim that CI has passed. Leaving the actual squash merge to the merge session; do not bypass required checks.

[devswha]

Maintainer pass on c9b3952 (merge lane). Nothing is asked of you here; this records what was checked and what I pushed on top.

Checked against real OpenCode

• OpenCode 1.17.15 (stable channel; 1.18.35, today's opencode-ai@latest, has the same tables): a pane in an isolated herdr session, one prompt that used the read tool and one follow-up. herdr 0.9.3 reported agent: "opencode" and agent_session { source: "herdr:opencode", kind: "id" } once the first prompt was sent. GET /api/pane/conversation answered 200 {"source":"scrollback","turns":[]} at the home screen, after the turns and with a before cursor, so the pane keeps the terminal exactly as before this PR. The image and tool-output routes answered 404. A 1.x store has no session_v2; it does have a session_message table, holding only agent-switched / model-switched rows.
• Cost on a 1.x store: one read against a real 131 MB store takes about 0.6 ms (median of 20; open, pragma, one failed prepare).
• OpenCode 2.0.25 (@opencode/cli, separate copy with its own data, config and state directories): the same two prompts. The endpoint answered opencode-transcript with the prompt, the read call with its output, both answers, the model, and a context figure of 6,984 against the footer's 7.0K. /undo moved the history id to …-r11, dropped the undone turn, and a cursor from the old history answered 409.
• Cost on a 2.x store (synthetic, 124 MB): an unchanged poll of a 12,000-row session takes 5.8 ms and 0.23 ms for a 120-row one; a poll after one row changed 9.5 ms.

Pushed

• 82db033: the tool-output and image routes answered 500 while the store was held past the busy timeout, where the conversation already kept its page. They answer 404 for that request now; a test holds the store and fails without the change.
• c9b3952: the tool-output route answered an OpenCode ref as immutable for a day, although the ref names a place in a row OpenCode rewrites in place. OpenCode refs get private, no-store, like the images; the contract test asserts the header.

Adversarial review (Codex) findings left as they are

• A single row larger than the 16 MB window is still the page (by design, pageStart): a 20 MiB row costs 23 to 55 ms once and 0.1 ms on later polls.
• Two writes to a row inside one millisecond, with a read between them, can leave the cached answer one write behind until the session's next write. A same-size rewrite in the same millisecond is not told apart at all.
• Every poll runs the count / max(seq) / max(time_updated) aggregate over the session (the 5.8 ms above).
• An image ref is an ordinal within the message, so a parallel tool finishing later shifts it. The page is re-read with the new refs on the next poll and the route is already no-store.

Local: bun run check fast green (1,919 pass, 6 skipped), opencode.contract and api.contract green (102 pass).

[devswha]

Independent review of 4e54229 (lead session). The contributor's work was updated by an earlier maintainer session (1a6ec38, 3883e21); lane rev-543 then ran a Codex gpt-6-astra adversarial pass and real OpenCode runs, wrote 82db033 and c9b3952, and merged main 9024fed (4e54229).

Verdict: approve and merge. Thanks, @Ploppy3.

What I ran, in a scratch copy of c9b3952 (4e54229 adds only the merge of main):

Check	Result
bun test ./server/opencode.test.ts ./server/conversation.test.ts	94 pass, 0 fail
the same with server/opencode.ts from 3883e21 (before the lane's commits)	1 fail: the tool-output and image routes failing instead of answering nothing while the store is held
a read-only look at a real OpenCode 1.17.15 store (131 MB)	it has session, message and part (95 sessions) and no session_v2, so this reader does not apply to it

Read:

• OpenCode 1.x is safe, and unchanged. A store without session_v2 answers transcript_missing, so the pane keeps the terminal text exactly as before this PR; the lane saw 200 {"source":"scrollback"} on a real 1.17.15 pane and measured about 0.6 ms per read on the 131 MB store. Today's stable OpenCode (1.18.35) stores turns the same way, so the chat appears for OpenCode 2.x (@opencode/cli) only. A 1.x reader would be a separate change.
• Binding is only the session herdr's integration reports for that pane (source: herdr:opencode, kind id, a ses_… id). No guess from the directory.
• 82db033: a store held past the busy timeout makes the tool-output and image routes answer 404 for that request instead of 500.
• c9b3952: an OpenCode tool-output ref names a place in a row OpenCode rewrites in place, so it is served private, no-store; other agents' tool outputs keep their immutable cache. The contract test asserts the header; I did not run that test myself (it needs a live herdr), CI did.

The Lows in the lane's comment are fine as they are. Both required checks and CodeRabbit are green on 4e54229, every thread is resolved, and the branch contains main.