feat(fabric): coalesce a split agent turn into ONE message (deterministic)

OpenClaw delivers an agent turn whose blocks are text -> thinking/tool
-> text via multiple inbound deliver() calls (a non-text block is a
delivery boundary), so one turn became N Fabric messages.

Fix: buffer deliver() segments per channel (src/coalesce.ts) and flush
them as ONE postMessage at a deterministic boundary — the finally after
dispatchInboundReplyWithBase() resolves, which provably runs only after
every deliver() of the turn (verified: deliver,deliver -> dispatch
returned -> flush). No hooks, no timers, no idle guessing. The
agent_end hook was rejected: it fires BEFORE deliver(). gateway_stop
flushes any leftover; a long safety timeout is a leak-guard only.
channels.fabric.coalesce=false restores raw per-segment posting.

Verified on local openclaw + Fabric with a fake text/thinking/text
model: single trigger -> exactly one merged message.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/accounts.ts

@@ -18,6 +18,11 @@ export type FabricChannelConfig = {
   // (Guild C-2). Required by the channel config schema; sourced from config
   // only — never from the environment.
   commandsSyncKey?: string;
+  // Coalesce an agent turn that OpenClaw split into multiple deliveries
+  // (text → thinking/tool → text => N sendText calls) into ONE Fabric
+  // message. The flush boundary is the deterministic `agent_end` hook (not
+  // a timer). Default true; set false for raw per-segment posting.
+  coalesce?: boolean;
   accounts?: Record<string, FabricAccountConfig>;
   defaultAccount?: string;
 } & FabricAccountConfig;
@@ -46,6 +51,12 @@ export function resolveCommandsSyncKey(cfg: Cfg): string {
   return (section(cfg).commandsSyncKey ?? '').trim();
 }
 
+// Whether to coalesce a split agent turn into one Fabric message
+// (channel-level). Default true.
+export function resolveCoalesce(cfg: Cfg): boolean {
+  return (cfg.channels?.fabric ?? {}).coalesce !== false;
+}
+
 export function listFabricAccountIds(cfg: Cfg): string[] {
   const accts = section(cfg).accounts ?? {};
   const ids = Object.keys(accts);

src/channel.ts

@@ -159,7 +159,10 @@ export const fabricChannelPlugin = createChatChannelPlugin<ResolvedFabricAccount
         cfg?: unknown;
         config?: unknown;
       }) => {
-        // openclaw passes config under cfg or config depending on path
+        // openclaw passes config under cfg or config depending on path.
+        // Note: inbound agent replies go through inbound.ts `deliver`
+        // (where turn coalescing happens). This path is for any direct
+        // outbound sends and posts immediately.
         const cfg = (ctx.cfg ?? ctx.config ?? {}) as AnyCfg;
         try {
           const r = await sendToFabric(cfg, ctx.accountId ?? null, ctx.to, ctx.text);

src/coalesce.ts

@@ -0,0 +1,93 @@
+// Deterministic turn coalescer.
+//
+// OpenClaw calls the Fabric `deliver` callback once per assistant text
+// segment; a thinking/tool block between two text blocks is a delivery
+// boundary, so one agent turn of `text → thinking/tool → text` arrives as
+// multiple deliver() calls. There is no turn id on the delivery, so we
+// BUFFER segments by Fabric channelId and post the merged message when the
+// turn truly ends. The flush is driven by inbound.ts right after
+// `dispatchInboundReplyWithBase` resolves — that only happens AFTER every
+// deliver() of the turn, a deterministic boundary (NOT a timer, NOT the
+// agent_end hook, which fires before deliver()). `coalesce=false` posts
+// each segment immediately.
+
+const SAFETY_FLUSH_MS = 120_000; // leak-guard only; not the flush mechanism
+
+export function normChannelId(x: string | null | undefined): string {
+  const s = String(x ?? '');
+  return s.startsWith('fabric:') ? s.slice('fabric:'.length) : s;
+}
+
+type Pending = {
+  parts: string[];
+  post: (text: string) => Promise<void>;
+  log?: (m: string) => void;
+  safety: ReturnType<typeof setTimeout>;
+};
+const pendingByChannel = new Map<string, Pending>();
+
+async function flushChannel(channelId: string, reason: string): Promise<void> {
+  const p = pendingByChannel.get(channelId);
+  if (!p) return;
+  pendingByChannel.delete(channelId);
+  clearTimeout(p.safety);
+  const text = p.parts.join('\n\n').trim();
+  if (!text) return;
+  try {
+    await p.post(text);
+    p.log?.(`fabric: flushed ${p.parts.length} segment(s) channel=${channelId} (${reason})`);
+  } catch (e) {
+    p.log?.(`fabric: flush FAILED channel=${channelId} (${reason}): ${String(e)}`);
+  }
+}
+
+// Buffer one delivered segment (or send immediately when coalesce=false).
+// `post` performs the real Fabric postMessage with the caller's already
+// resolved guild/token; on flush it is called once with the merged text.
+export async function enqueueDelivery(params: {
+  channelId: string;
+  text: string;
+  coalesce: boolean;
+  post: (text: string) => Promise<void>;
+  log?: (m: string) => void;
+}): Promise<void> {
+  const cid = normChannelId(params.channelId);
+  const text = (params.text ?? '').trim();
+  if (!text) return;
+  if (!params.coalesce) {
+    await params.post(text);
+    return;
+  }
+  const existing = pendingByChannel.get(cid);
+  if (existing) {
+    existing.parts.push(text);
+    existing.post = params.post; // freshest guild/token closure
+    existing.log = params.log;
+  } else {
+    pendingByChannel.set(cid, {
+      parts: [text],
+      post: params.post,
+      log: params.log,
+      safety: setTimeout(
+        () => void flushChannel(cid, 'safety-timeout'),
+        SAFETY_FLUSH_MS,
+      ),
+    });
+  }
+}
+
+// Called by the agent_end hook with the hook ctx's channelId (bare or
+// fabric:-prefixed). Deterministic per-turn boundary.
+export async function flushFabricForChannel(
+  rawChannelId: string | null | undefined,
+): Promise<void> {
+  const cid = normChannelId(rawChannelId);
+  if (cid) await flushChannel(cid, 'dispatch-end');
+}
+
+// gateway_stop: flush anything still buffered.
+export async function flushAllFabric(): Promise<void> {
+  for (const cid of [...pendingByChannel.keys()]) {
+    await flushChannel(cid, 'gateway_stop');
+  }
+}

src/inbound.ts

@@ -5,6 +5,8 @@ import { io, type Socket } from 'socket.io-client';
 import { dispatchInboundReplyWithBase } from 'openclaw/plugin-sdk/inbound-reply-dispatch';
 import type { FabricClient, FabricSession } from './fabric-client.js';
 import type { IdentityRegistry } from './identity.js';
+import { resolveCoalesce } from './accounts.js';
+import { enqueueDelivery, flushFabricForChannel } from './coalesce.js';
 
 // COMPAT NOTE (openclaw v2026.5.7): the inbound path mirrors how bundled
 // channels (nextcloud-talk) drive the kernel:
@@ -301,8 +303,17 @@ export class FabricInbound {
           const text = (payload?.text ?? '').trim();
           this.log.info(`fabric: deliver agent=${agentId} channel=${channelId} len=${text.length}`);
           if (!text || !gt) return;
-          await this.client.postMessage(guild.endpoint, gt, channelId, text, session.user.id);
-          this.log.info(`fabric: posted reply agent=${agentId} channel=${channelId}`);
+          // Buffer segments; the merged message is posted right after
+          // dispatch returns (the deterministic turn boundary, see the
+          // finally below). Disable per channel: channels.fabric.coalesce.
+          await enqueueDelivery({
+            channelId,
+            text,
+            coalesce: resolveCoalesce(this.cfg as never),
+            post: (t) =>
+              this.client.postMessage(guild.endpoint, gt, channelId, t, session.user.id) as Promise<void>,
+            log: (m) => this.log.info(m),
+          });
         },
         onRecordError: (err: unknown) =>
           this.log.warn(`fabric: session record failed agent=${agentId}: ${String(err)}`),
@@ -327,6 +338,12 @@ export class FabricInbound {
       this.log.info(`fabric: dispatch returned agent=${agentId} channel=${channelId}`);
     } catch (err) {
       this.log.warn(`fabric: dispatch failed agent=${agentId} channel=${channelId}: ${String(err)}`);
+    } finally {
+      // Deterministic per-turn boundary: dispatchInboundReplyWithBase only
+      // resolves AFTER every deliver() call of this turn has run, so the
+      // buffer now holds all segments — flush them as ONE Fabric message.
+      // No hooks, no timers, no idle guessing.
+      await flushFabricForChannel(channelId);
     }
   }
 }