From 3bbdcaf87f8ceffd633fda7c2316a6f1314f43d1 Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Sat, 3 Jan 2026 17:10:47 +0100
Subject: [PATCH] fix: avoid duplicate block streaming

---
 CHANGELOG.md            |  1 +
 docs/agent.md           |  2 +-
 docs/configuration.md   |  2 +-
 src/auto-reply/reply.ts | 14 ++++++++++++--
 4 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index efd2e6011..0df9cad07 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
 
 ### Fixes
 - Telegram: chunk block-stream replies to avoid “message is too long” errors (#124) — thanks @mukhtharcm.
+- Block streaming: default to text_end and suppress duplicate block sends while in-flight.
 - Gmail hooks: resolve gcloud Python to a real executable when PATH uses mise shims — thanks @joargp.
 - Control UI: generate UUIDs when `crypto.randomUUID()` is unavailable over HTTP — thanks @ratulsarna.
 - Agent: add soft block-stream chunking (800–1200 chars default) with paragraph/newline preference.
diff --git a/docs/agent.md b/docs/agent.md
index f464fc32e..32a1a7733 100644
--- a/docs/agent.md
+++ b/docs/agent.md
@@ -82,7 +82,7 @@ current turn ends, then a new agent turn starts with the queued payloads. See
 
 Block streaming sends completed assistant blocks as soon as they finish; disable
 via `agent.blockStreamingDefault: "off"` if you only want the final response.
-Tune the boundary via `agent.blockStreamingBreak` (`text_end` vs `message_end`).
+Tune the boundary via `agent.blockStreamingBreak` (`text_end` vs `message_end`; defaults to text_end).
 Control soft block chunking with `agent.blockStreamingChunk` (defaults to
 800–1200 chars; prefers paragraph breaks, then newlines; sentences last).
 
diff --git a/docs/configuration.md b/docs/configuration.md
index 427fe6dc0..ada50170f 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -393,7 +393,7 @@ Controls the embedded agent runtime (model/thinking/verbose/timeouts).
 
 Block streaming:
 - `agent.blockStreamingDefault`: `"on"`/`"off"` (default on).
-- `agent.blockStreamingBreak`: `"text_end"` or `"message_end"`.
+- `agent.blockStreamingBreak`: `"text_end"` or `"message_end"` (default: text_end).
 - `agent.blockStreamingChunk`: soft chunking for streamed blocks. Defaults to
   800–1200 chars, prefers paragraph breaks (`\n\n`), then newlines, then sentences.
   Example:
diff --git a/src/auto-reply/reply.ts b/src/auto-reply/reply.ts
index 36e4b0d5c..af07632de 100644
--- a/src/auto-reply/reply.ts
+++ b/src/auto-reply/reply.ts
@@ -1124,14 +1124,14 @@ export async function getReplyFromConfig(
     (agentCfg?.verboseDefault as VerboseLevel | undefined);
   const resolvedBlockStreaming =
     agentCfg?.blockStreamingDefault === "off" ? "off" : "on";
-  // TODO(steipete): Default to message_end for now; figure out why text_end breaks and whether we can revert.
   const resolvedBlockStreamingBreak =
-    agentCfg?.blockStreamingBreak === "text_end" ? "text_end" : "message_end";
+    agentCfg?.blockStreamingBreak === "message_end" ? "message_end" : "text_end";
   const blockStreamingEnabled = resolvedBlockStreaming === "on";
   const blockReplyChunking = blockStreamingEnabled
     ? resolveBlockStreamingChunking(cfg, sessionCtx.Surface)
     : undefined;
   const streamedPayloadKeys = new Set<string>();
+  const pendingStreamedPayloadKeys = new Set<string>();
   const pendingBlockTasks = new Set<Promise<void>>();
   const buildPayloadKey = (payload: ReplyPayload) => {
     const text = payload.text?.trim() ?? "";
@@ -2232,6 +2232,13 @@ export async function getReplyFromConfig(
                   replyToId: tagResult.replyToId,
                 };
                 const payloadKey = buildPayloadKey(blockPayload);
+                if (
+                  streamedPayloadKeys.has(payloadKey) ||
+                  pendingStreamedPayloadKeys.has(payloadKey)
+                ) {
+                  return;
+                }
+                pendingStreamedPayloadKeys.add(payloadKey);
                 const task = (async () => {
                   await startTypingOnText(cleaned);
                   await opts.onBlockReply?.(blockPayload);
@@ -2241,6 +2248,9 @@ export async function getReplyFromConfig(
                   })
                   .catch((err) => {
                     logVerbose(`block reply delivery failed: ${String(err)}`);
+                  })
+                  .finally(() => {
+                    pendingStreamedPayloadKeys.delete(payloadKey);
                   });
                 pendingBlockTasks.add(task);
                 void task.finally(() => pendingBlockTasks.delete(task));