chat: send cwd on every message instead of reading it back from session metadata

Simpler + more efficient than the previous per-turn GET /session: the client already
has the selected cwd, so it now sends it on every message (it's constant for a session).
The server uses msg.cwd directly for OpenCode's per-turn working-directory system prompt,
and still tags the cwd at creation for listing. Drops the getSession round-trip.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/api/chat/opencode/client.ts

@@ -146,12 +146,6 @@ class ServerConnection {
     return (await res.json()) as OpenCodeSessionInfo[];
   }
 
-  async getSession(sessionId: string): Promise<OpenCodeSessionInfo | null> {
-    const res = await fetch(`${this.baseUrl}/session/${sessionId}`);
-    if (!res.ok) return null;
-    return (await res.json()) as OpenCodeSessionInfo;
-  }
-
   async getMessages(sessionId: string): Promise<OpenCodeStoredMessage[]> {
     const res = await fetch(`${this.baseUrl}/session/${sessionId}/message`);
     if (!res.ok) throw new Error(`opencode GET /session/${sessionId}/message → ${res.status}`);

src/servers/channels/send-opencode.ts

@@ -1,7 +1,7 @@
 import type { ChatEvent } from '@@/api/chat/types';
 import { logger } from '@@/api/chat/logger';
 import { ensureServer } from '@@/api/chat/opencode/server-manager';
-import { getConnection, officerMeta } from '@@/api/chat/opencode/client';
+import { getConnection } from '@@/api/chat/opencode/client';
 import { createEventMapper } from '@@/api/chat/opencode/event-mapper';
 import { getOpenCodeSession, setOpenCodeSession } from '@@/api/chat/opencode/state';
 
@@ -51,25 +51,17 @@ export async function sendOpenCodeStreaming(params: OpenCodeStreamingParams): Pr
   const conn = getConnection(baseUrl);
 
   // Resolve the OpenCode session: a known mapping, or — when resuming from history — the sessionKey is
-  // itself the OpenCode session id (`ses_…`); otherwise create a new one.
-  const existingId =
+  // itself the OpenCode session id (`ses_…`); otherwise create a new one, tagged with its cwd (for
+  // listing). The cwd rides every message from the client, so the system prompt below stays consistent.
+  let opencodeSessionId =
     getOpenCodeSession(params.sessionKey) ??
     (params.sessionKey.startsWith('ses_') ? params.sessionKey : undefined) ??
     params.resumeSessionId;
-
-  // The session's working directory is bound at creation (metadata.officer.cwd). msg.cwd only rides
-  // the first message, so for an existing/resumed session read the bound cwd back and reuse it — this
-  // keeps the system prompt (and session tagging) consistent across every turn.
-  let sessionId: string;
-  let cwd = params.cwd;
-  if (existingId) {
-    sessionId = existingId;
-    const bound = officerMeta((await conn.getSession(existingId))?.metadata).cwd;
-    if (bound) cwd = bound;
-  } else {
-    sessionId = await conn.createSession(cwd ? { officer: { cwd } } : undefined);
+  if (!opencodeSessionId) {
+    opencodeSessionId = await conn.createSession(params.cwd ? { officer: { cwd: params.cwd } } : undefined);
   }
-  setOpenCodeSession(params.sessionKey, sessionId);
+  setOpenCodeSession(params.sessionKey, opencodeSessionId);
+  const sessionId = opencodeSessionId;
 
   let unsub = () => {};
   const mapper = createEventMapper((event: ChatEvent) => {
@@ -79,7 +71,7 @@ export async function sendOpenCodeStreaming(params: OpenCodeStreamingParams): Pr
   unsub = conn.subscribe(sessionId, mapper);
 
   const { providerID, modelID } = splitModel(params.model ?? '');
-  const system = cwd ? officerSystemPrompt(cwd) : undefined;
+  const system = params.cwd ? officerSystemPrompt(params.cwd) : undefined;
 
   // Fire the turn; assistant tokens + tool calls stream back over the SSE subscription above.
   conn.postMessage(sessionId, providerID, modelID, params.prompt, system).catch((err) => {