Add /tldr: a private overview of what you missed in a channel

/tldr [since] summarizes the messages in the channel it is run in that the
caller has not been summarized yet, using a small local model on Ollama, and
replies ephemerally. The answer streams into the reply as it is written.

- Per-user, per-channel cursor (tldr_cursors) so each run picks up where the
  last left off; `since:` (e.g. 6h, 2d, max 7d) peeks without moving it.
  First use covers the last 24h, and a stale cursor never reaches back more
  than 7 days.
- Only summarizes channels both the caller and the bot can read.
- The transcript drops bots, system messages, reactions and filler, turns
  links, GIFs, images and files into short tags ([link: site], [image],
  [file: name], preview titles), marks replies, and writes a date marker
  where the chat paused for 3h or more so the model can keep topics apart.
- The prompt asks for one bullet per conversation, oldest first, with a
  worked example; it was tuned against a synthetic chat and a real export
  with qwen3:4b-instruct-2507 (the default model).
- One model call at a time across the bot, one /tldr per user.
- docker-compose: Ollama service (CPU only, 8g memory cap: 6g killed the
  runner mid-request), model pull on startup.

Needs the tldr_cursors migration (velox-dashboard-api 000016).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/commands/tldr/public/tldr.go

@@ -0,0 +1,160 @@
+package public
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log"
+	"strings"
+	"time"
+
+	"velox-bot/internal/db/services"
+	"velox-bot/internal/tldr"
+
+	"github.com/bwmarrin/discordgo"
+)
+
+var dmPermission = false
+
+var Tldr = &discordgo.ApplicationCommand{
+	Name:         "tldr",
+	Description:  "Privately summarize what you missed in this channel",
+	DMPermission: &dmPermission,
+	Options: []*discordgo.ApplicationCommandOption{
+		{
+			Type:        discordgo.ApplicationCommandOptionString,
+			Name:        "since",
+			Description: "Look back this far instead of since your last /tldr (e.g. 30m, 6h, 2d; max 7d)",
+			Required:    false,
+		},
+	},
+}
+
+const embedColor = 0xFFA500
+
+func TldrHandler(s *discordgo.Session, i *discordgo.InteractionCreate) {
+	if i.GuildID == "" || i.Member == nil || i.Member.User == nil {
+		_ = s.InteractionRespond(i.Interaction, &discordgo.InteractionResponse{
+			Type: discordgo.InteractionResponseChannelMessageWithSource,
+			Data: &discordgo.InteractionResponseData{
+				Content: "`/tldr` only works in a server.",
+				Flags:   discordgo.MessageFlagsEphemeral,
+			},
+		})
+		return
+	}
+
+	var since time.Duration
+	var sinceText string
+	for _, opt := range i.ApplicationCommandData().Options {
+		if opt.Name != "since" {
+			continue
+		}
+		d, err := tldr.ParseSince(opt.StringValue())
+		if err != nil {
+			_ = s.InteractionRespond(i.Interaction, &discordgo.InteractionResponse{
+				Type: discordgo.InteractionResponseChannelMessageWithSource,
+				Data: &discordgo.InteractionResponseData{
+					Content: err.Error(),
+					Flags:   discordgo.MessageFlagsEphemeral,
+				},
+			})
+			return
+		}
+		since, sinceText = d, strings.ToLower(strings.TrimSpace(opt.StringValue()))
+	}
+
+	_ = s.InteractionRespond(i.Interaction, &discordgo.InteractionResponse{
+		Type: discordgo.InteractionResponseDeferredChannelMessageWithSource,
+		Data: &discordgo.InteractionResponseData{
+			Content: "Reading what you missed…",
+			Flags:   discordgo.MessageFlagsEphemeral,
+		},
+	})
+
+	edit := func(content string) {
+		_, _ = s.InteractionResponseEdit(i.Interaction, &discordgo.WebhookEdit{Content: &content})
+	}
+
+	userID := i.Member.User.ID
+	if !tldr.TryStart(userID) {
+		edit("You already have a summary running, give it a moment.")
+		return
+	}
+	defer tldr.Done(userID)
+
+	ctx, cancel := context.WithTimeout(context.Background(), tldr.RunTimeout())
+	defer cancel()
+
+	// While the model writes, show the overview growing instead of leaving the
+	// "Summarizing…" text up for the whole wait. The final edit below replaces it.
+	showPartial := func(text string) {
+		content := ""
+		embeds := []*discordgo.MessageEmbed{{
+			Title:       "TL;DR",
+			Description: clip(text, 4000),
+			Color:       embedColor,
+			Footer:      &discordgo.MessageEmbedFooter{Text: "still writing…"},
+		}}
+		_, _ = s.InteractionResponseEdit(i.Interaction, &discordgo.WebhookEdit{Content: &content, Embeds: &embeds})
+	}
+
+	res, err := tldr.Run(ctx, s, services.Global.TLDR, tldr.Default(), tldr.Request{
+		GuildID:   i.GuildID,
+		ChannelID: i.ChannelID,
+		UserID:    userID,
+		BotID:     s.State.User.ID,
+		UserPerms: i.Member.Permissions,
+		Since:     since,
+	}, edit, showPartial)
+	if errors.Is(err, tldr.ErrUserCannotRead) {
+		edit("You need to be able to read this channel's message history to summarize it.")
+		return
+	}
+	if errors.Is(err, tldr.ErrBotCannotRead) {
+		edit("I can't read this channel's history. I need View Channel and Read Message History here.")
+		return
+	}
+	if err != nil {
+		log.Printf("tldr: guild %s user %s: %v", i.GuildID, userID, err)
+		edit("I couldn't put a summary together right now. The summarizer may be down or busy, try again in a bit.")
+		return
+	}
+	if res.Empty {
+		edit("Nothing new to summarize.")
+		return
+	}
+
+	scope := "since your last /tldr here"
+	if since > 0 {
+		scope = "last " + sinceText
+	}
+	footer := fmt.Sprintf("%d messages · %s", res.Messages, scope)
+	if res.Truncated {
+		if since > 0 {
+			footer += " · more than fit, the most recent were left out, try a shorter window"
+		} else {
+			footer += " · more than fit, run /tldr again for the rest"
+		}
+	}
+
+	empty := ""
+	embeds := []*discordgo.MessageEmbed{{
+		Title:       "TL;DR",
+		Description: clip(res.Summary, 4000),
+		Color:       embedColor,
+		Footer:      &discordgo.MessageEmbedFooter{Text: footer},
+	}}
+	_, _ = s.InteractionResponseEdit(i.Interaction, &discordgo.WebhookEdit{
+		Content: &empty,
+		Embeds:  &embeds,
+	})
+}
+
+func clip(s string, n int) string {
+	r := []rune(s)
+	if len(r) <= n {
+		return s
+	}
+	return string(r[:n-1]) + "…"
+}