feat(discord): periodic thread retitle on top of upstream semantic titles

[TheoLong]

Problem

Discord threads default to the originating message's first line — rarely a good title for a multi-turn agent session.

Change

Rename the thread to the auto-generated session title after the first exchange, and again periodically as the conversation evolves. New periodic retitle helper added to agent/title_generator.py; wired in via gateway/run.py.

Trade-off / opt-out

I noticed #28… feat(telegram): add disable_topic_auto_rename gateway flag just landed for the Telegram side — users want to opt out of unsolicited renames when they've named topics by hand.

This Discord change is the mirror image and the same opt-out concern applies. Happy to add gateway.platforms.discord.extra.disable_thread_auto_rename (default False, preserving the behaviour in this PR) as a follow-up commit on this branch if maintainers want it baked in before merge.

Risk

Medium. Behaviour change visible to every Discord user. Opt-out flag recommended before merge.

[alt-glitch]

Note: competing open PR #15757 implements Discord thread name syncing. Prior closed attempts: #13915, #16059. Consider adding opt-out flag (gateway.platforms.discord.extra.disable_thread_auto_rename) mirroring the Telegram disable_topic_auto_rename from #28986.

[TheoLong]

Rebased on current main (1,824 commits absorbed). Added the opt-out flag requested in the triage comment — gateway.platforms.discord.extra.disable_thread_auto_rename, mirroring the Telegram disable_topic_auto_rename pattern from #28986. Default False preserves prior behaviour; operators who manage thread names manually can opt out without disabling the feature globally.

Re competing PR #15757 and prior closes (#13915, #16059): also happy to defer. Bumping for review.

[TheoLong]

Rebased on current main (630 commits since the last bump). Clean one-commit replay; agent/title_generator.py + gateway/run.py parse clean.

The opt-out flag the triage bot asked for is already in this branch — gateway.platforms.discord.extra.disable_thread_auto_rename, mirroring the Telegram disable_topic_auto_rename pattern from #28986. Default False preserves prior behaviour.

On overlap with what's on main: current main names the CLI→Discord handoff thread at creation (thread_name = f"Hermes — {cli_title}" in gateway/run.py), and #3f3d8a7b2 cleaned up mention-stripping in _auto_create_thread names. Neither covers what this PR does — renaming an existing conversation thread from the evolving session title, plus the periodic retitle as the session's topic drifts. Those two pieces have no equivalent on main, so this stays a real gap rather than a duplicate.

Re competing #15757 and prior closes (#13915, #16059): happy to defer if a maintainer prefers one of those. Bumping for review.

[TheoLong]

Rebased on current main (1,575 commits absorbed since the last bump). Clean one-commit replay; agent/title_generator.py + gateway/run.py parse clean, 40/40 in tests/agent/test_title_generator.py.

The opt-out flag the triage bot asked for is already in this branch — gateway.platforms.discord.extra.disable_thread_auto_rename, mirroring the Telegram disable_topic_auto_rename pattern from #28986. Default False preserves prior behaviour.

No overlap with 3b739b990 (strip <think> blocks from title output) which also touches title_generator.py — that scrubs generate_title's raw output, whereas this carry adds the periodic-retitle path (maybe_retitle_session → whole-conversation reassessment via _condense_history, no-op when the durable topic hasn't drifted). Different functions, clean replay.

Re competing PR #15757 (thread name syncing) that automation flagged: happy to defer if a maintainer prefers it; this version additionally handles periodic drift (re-evaluates every N turns), not just the first-turn rename.

[teknium1]

Thanks for carrying the periodic-retitle portion forward. Current main already landed the first-title Discord rename in 0d9ed9214 / v2026.7.7, but the periodic behavior remains distinct.

Problems

• gateway/run.py:3498-3511 accepts every Discord thread, and gateway/run.py:13433-13445 then directly edits any differing name. This regresses main's intentional human-name protection: gateway/session.py:185-191 records auto-thread provenance, and tests/gateway/test_discord_slash_commands.py:714-729 verifies a human rename is not overwritten.
• gateway/run.py:13398 truncates by Python code points. Discord's limit is UTF-16 units; current main fixed this in 1deeaf71a, using UTF-16-aware truncation at gateway/run.py:13657-13669.
• agent/title_generator.py:288-301 omits strip_think_blocks, unlike the existing title path at agent/title_generator.py:90-106; periodic retitles can therefore persist reasoning markup.

Suggested changes

• Build periodic retitling on main's guarded DiscordAdapter.rename_thread path, preserving manual renames and auto-thread provenance.
• Reuse the UTF-16 sanitizer and canonical think-block scrubber.
• Add gateway coverage for periodic scheduling, human/pre-existing thread preservation, and UTF-16 titles.

This is an automated hermes-sweeper review.

[teknium1]

Discord applies its thread-name limit in UTF-16 code units, so this code-point slice can still exceed the API limit for emoji/non-BMP titles. Please reuse main's UTF-16-aware sanitizer (_prefix_within_utf16_limit); this was fixed in 1deeaf71a.

[teknium1]

This edits any thread whose name differs from the generated title, including a human-renamed or pre-existing thread. Main deliberately preserves the initial auto-thread name in SessionSource and uses DiscordAdapter.rename_thread(..., only_if_current_name=...); please retain equivalent ownership protection here.

[teknium1]

Please sanitize reasoning output with the same strip_think_blocks helper used by generate_title before validating the title. Otherwise a periodic retitle from a think-enabled model can persist `` content into the session and Discord thread name.

[TheoLong]

Rebased on current main (c48d534; 955 commits absorbed). One additive conflict this cycle: main reworked agent/title_generator.py (atomic auto-title write, manual-title-race guard, disabled-config honoring, #50535–50537). This PR's _condense_history / _looks_like_title / regenerate_title are independent symbols — concatenated cleanly, 74 title tests pass with no cascade. The prose-rejection guard (_looks_like_title) remains the distinctive delta.

[TheoLong]

Rebased onto current main (~3,938 commits absorbed since the last refresh; Jul 23 → Sep 2). One additive conflict in gateway/run.py, resolved by taking upstream's side wholesale (the new _TELEGRAM_LOBBY_REMINDER_COOLDOWN_S / _telegram_topic_cooldown_key block landed in the same region; this patch's side of that hunk was empty).

Scope note — this PR is now only the periodic half. Upstream has since landed semantic thread titles (_schedule_discord_semantic_thread_rename), which supersedes the original first-turn auto-rename. Rather than keep a stale fork of that, this branch drops it and rebuilds the surviving half on top of upstream's infrastructure: a thread whose topic drifts mid-conversation gets retitled to match, reusing upstream's own rename lane rather than adding parallel plumbing.

I re-verified the integration against 808a22ea00d ("gate relay-only thread rename kwargs"), which changed this exact callback. _on_session_title is still 2-arg (title, title_source) and now fires only when title_source == "llm". A periodic retitle is a genuine model-derived title, so the call site passes it explicitly:

title_callback=(lambda t: _retitle_cb(t, "llm")) if _retitle_cb else None

Worth stating plainly because a silent arity/gate mismatch here would make the feature a no-op in production while unit tests — which pass their own callback — stayed green.

A guard worth reviewing on its own merits: _looks_like_title() rejects model output that isn't a title (>10 words, >80 chars, mid-sentence lowercase break, internal newline) and returns None to keep the existing title. This came from a real production failure — the retitle model answered the "should this change?" prompt conversationally and a len>80 → truncate fallback wrote "The title remains accurate. The conversation is still about triaging and exec…" as a literal Discord thread title. Truncation is the wrong default for over-long model output: a real 3-7 word title is never >80 chars, so anything hitting that branch is junk to reject, not salvage. The regression test feeds that exact prose string and asserts None.

tests/agent/test_title_generator.py — 68 tests green on the rebased branch; 155 passed / 0 failed across the full 8-file slice, including tests/gateway/test_session_title_rename_lane.py.

Rate limiting is respected throughout (Discord's channel-rename budget is ~2/10min); the retitle is fire-and-forget on a daemon thread and never blocks a turn.