Problem

Sessions start as untitled (/name shows a suggestion only on demand). Users must manually run /name to set a title. Multi-topic sessions keep their original title even after shifting topics entirely. Meanwhile, an LLM slug generator already exists in the codebase (llm-slug-generator) for memory filenames — it just isnt wired into session titling.

Related: #77165 (basic auto-title request), #94529 (auto-derive in sidebar), #81781 (improve derived titles beyond first message)

Proposal: Three-Phase Auto-Titling

Phase 1 — Lazy Initial Title (after N messages, not immediately)

Dont title on session creation or first message. Wait until N messages have passed (configurable, default 4-6). This avoids titles like "hi" or "help" from one-word openers, and gives enough context for a meaningful slug.

sessions:
  autoTitle:
    enabled: true
    triggerAfterMessages: 5       # wait for 5th message before first title gen
    model: "openai/gpt-4.1-mini"  # cheap model override, falls back to default

Phase 2 — Cheap Model for Title Generation

Title generation does NOT need a frontier model. A cheap, fast model works perfectly:

Config should allow a dedicated titleModel override separate from the session model, defaulting to the cheapest available provider model. Title prompts are tiny (~200 tokens input, ~10 tokens output) so cost is negligible even with frontier models, but the principle of using cheap models for cheap tasks matters.

Phase 3 — Periodic Topic-Aware Re-Titling

Sessions drift. A conversation that starts as "skill audit" might shift to "LinkedIn content strategy" after 30 messages. The title should track the active topic.

sessions:
  autoTitle:
    reTitleInterval: 20           # re-evaluate title every N messages
    reTitleWindow: 15             # use last N messages for context (sliding window)
    reTitleMinChange: true        # only rename if topic meaningfully changed

Implementation:

• Every reTitleInterval messages, feed the last reTitleWindow messages to the title model
• Compare generated title against current title (simple string similarity or LLM-based "did the topic change?")
• Only apply rename if the new title is meaningfully different (avoid flickering)
• Titles should be 2-4 word lowercase slugs: "skill-audit-cleanup", "linkedin-automation", "session-naming-proposal"

Reuse Existing Infrastructure

The llm-slug-generator already exists in dist/ and handles:

• Short 1-2 word lowercase hyphenated slugs
• LLM-based generation from conversation content
• Memory filename integration

Wire this same generator (or a configurable variant) into session title mutation on the trigger conditions above.

UX Behavior

• Title appears in sidebar, /sessions list, Control UI tabs, and session history
• /name with no args shows current title + when it was last auto-generated
• Manual /name <title> overrides and locks the title (no more auto-renames for that session)
• /name --auto re-enables auto-titling for a manually-named session

Configuration Surface

sessions:
  autoTitle:
    enabled: false                # default off, opt-in
    triggerAfterMessages: 5       # messages before first title gen (min 3)
    model: null                   # null = cheapest available provider model
    reTitle:
      enabled: true               # periodic re-titling
      interval: 20                # messages between re-evaluations
      window: 15                  # last N messages used as context
      minDistance: 0.4            # string similarity threshold (0-1) to skip no-op renames

Edge Cases

• Single-message sessions: never titled (below triggerAfterMessages)
• Very short sessions: titled at message N, then session ends — perfectly fine
• Rapid-fire messages: debounce title generation; dont fire on every message in a burst
• Subagent sessions: auto-title based on task description (available immediately, no N-message wait needed)
• Channel-bound sessions: may want different auto-title behavior (group chats vs DMs)

Precedents

• ChatGPT: auto-titles after ~2-3 exchanges
• Claude: auto-titles immediately from first prompt
• Cursor: auto-titles chat sessions
• All of them occasionally produce dumb titles from insufficient context — the triggerAfterMessages approach directly addresses this known failure mode

Scope

This is a gateway-side feature: the model call, title storage, and trigger logic all live in the gateway. The Control UI and TUI already consume and display session labels — no UI changes required beyond the existing #94529 and #89922 work.

Migration

Backward-compatible. Default is enabled: false. Existing /name behavior unchanged. Sessions with manually-set titles are not auto-renamed.