fix: address code review feedback on streaming PR

- Deduplicate Streamer interface: alias channels.Streamer to bus.Streamer
  to prevent type drift across packages
- Increase SSE scanner buffer to 10MB max to handle large single-line
  responses that exceed bufio.Scanner's 64KB default
- Switch draftID generation from math/rand to crypto/rand for
  collision-resistant random IDs
- Add context cancellation check in SSE parsing loop so cancelled
  streams stop processing immediately
- Log Finalize failures with chat_id and content length for debugging
  silent message delivery failures

pkg/channels/interfaces.go

@@ -1,6 +1,10 @@
 package channels
 
-import "context"
+import (
+	"context"
+
+	"github.com/sipeed/picoclaw/pkg/bus"
+)
 
 // TypingCapable — channels that can show a typing/thinking indicator.
 // StartTyping begins the indicator and returns a stop function.
@@ -44,15 +48,9 @@ type StreamingCapable interface {
 	BeginStream(ctx context.Context, chatID string) (Streamer, error)
 }
 
-// Streamer pushes incremental content to a streaming-capable channel.
-type Streamer interface {
-	// Update sends accumulated partial content to the user.
-	Update(ctx context.Context, content string) error
-	// Finalize commits the final message. After this, the Streamer is done.
-	Finalize(ctx context.Context, content string) error
-	// Cancel aborts the stream (e.g. when tool calls are detected mid-stream).
-	Cancel(ctx context.Context)
-}
+// Streamer is defined in pkg/bus to avoid circular imports.
+// This alias keeps channel implementations using channels.Streamer unchanged.
+type Streamer = bus.Streamer
 
 // PlaceholderRecorder is injected into channels by Manager.
 // Channels call these methods on inbound to register typing/placeholder state.

pkg/channels/telegram/telegram.go

@@ -3,7 +3,8 @@ package telegram
 import (
 	"context"
 	"fmt"
-	"math/rand"
+	"crypto/rand"
+	"encoding/binary"
 	"net/http"
 	"net/url"
 	"os"
@@ -800,7 +801,7 @@ func (c *TelegramChannel) BeginStream(ctx context.Context, chatID string) (chann
 	return &telegramStreamer{
 		bot:     c.bot,
 		chatID:  cid,
-		draftID: rand.Intn(1<<31-1) + 1, // non-zero random draft ID
+		draftID: cryptoRandInt(), // non-zero random draft ID
 	}, nil
 }
 
@@ -868,6 +869,11 @@ func (s *telegramStreamer) Finalize(ctx context.Context, content string) error {
 		// Fallback to plain text
 		tgMsg.ParseMode = ""
 		if _, err = s.bot.SendMessage(ctx, tgMsg); err != nil {
+			logger.ErrorCF("telegram", "Finalize failed after HTML and plain-text attempts", map[string]any{
+				"chat_id": s.chatID,
+				"error":   err.Error(),
+				"len":     len(content),
+			})
 			return fmt.Errorf("telegram finalize: %w", err)
 		}
 	}
@@ -877,3 +883,10 @@ func (s *telegramStreamer) Finalize(ctx context.Context, content string) error {
 func (s *telegramStreamer) Cancel(ctx context.Context) {
 	// Draft auto-expires on Telegram's side; nothing to clean up.
 }
+
+// cryptoRandInt returns a non-zero random int using crypto/rand.
+func cryptoRandInt() int {
+	var b [4]byte
+	_, _ = rand.Read(b[:])
+	return int(binary.BigEndian.Uint32(b[:])) | 1 // ensure non-zero
+}

pkg/providers/openai_compat/provider.go

@@ -244,11 +244,11 @@ func (p *Provider) ChatStream(
 		return nil, fmt.Errorf("API request failed:\n  Status: %d\n  Body:   %s", resp.StatusCode, string(body))
 	}
 
-	return parseStreamResponse(resp.Body, onChunk)
+	return parseStreamResponse(ctx, resp.Body, onChunk)
 }
 
 // parseStreamResponse parses an OpenAI-compatible SSE stream.
-func parseStreamResponse(reader io.Reader, onChunk func(accumulated string)) (*LLMResponse, error) {
+func parseStreamResponse(ctx context.Context, reader io.Reader, onChunk func(accumulated string)) (*LLMResponse, error) {
 	var textContent strings.Builder
 	var finishReason string
 	var usage *UsageInfo
@@ -262,7 +262,13 @@ func parseStreamResponse(reader io.Reader, onChunk func(accumulated string)) (*L
 	activeTools := map[int]*toolAccum{}
 
 	scanner := bufio.NewScanner(reader)
+	scanner.Buffer(make([]byte, 0, 1024*1024), 10*1024*1024) // 1MB initial, 10MB max
 	for scanner.Scan() {
+		// Check for context cancellation between chunks
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+
 		line := scanner.Text()
 
 		if !strings.HasPrefix(line, "data: ") {