What

ingestSlackMessages derives a container's kind from the id prefix , startsWith('D') ? 'dm' : 'channel' , and Slack now issues C… ids for group DMs, so a C-shaped mpim reaches ensureContainer claiming to be a channel. COALESCE(EXCLUDED.kind, …) took that guess over a stored 'group', because the guess is not NULL.

Measured on the first real DM backfill against Invoicebutler: two mpims admitted as 'group' came back out of ingest as 'channel', carrying Slack's own mpdm-mihir--kristina141--quinnlitherland11-1 in place of the deliberate 'directmessage'.

Why the asymmetry is right

'dm'/'group' is only ever set by a caller that RESOLVED the conversation , the admission rung asked conversations.members. 'channel' is what every prefix guess falls back to. The specific value is evidence, the general one is a default, and a default must not overwrite evidence.

display_name inverts the usual rule on a DM for a sharper reason: a channel's name legitimately changes and the newest sync is right, but a DM's name is the deliberate constant 'directmessage' (design: dm-auto-sync.md §4 Phase 1), chosen because rung 5 tokenises a container name against split_part(company_domain, '.', 1). Letting Slack's mpdm name land there feeds people's names to a rung built for cedar-acme-shaped ones and invites a link to a company that merely shares a token.

A NULL is still filled, so nothing is left nameless, and a real channel still renames.

Verification

• Test confirmed to FAIL against the previous COALESCE before being kept.
• vitest run src/services/channels src/services/integrations/slack , 246 passed, 26 skipped.
• pnpm --filter @zero/server run types , exit 0.
• pnpm deps:check , no violations.

🤖 Generated with Claude Code

Greptile Summary

The PR changes channel-container conflict updates so resolved Slack DM/group metadata survives later prefix-based guesses while ordinary channels remain renameable.

• Preserves stored dm and group kinds when a later upsert supplies a generic channel classification.
• Preserves non-NULL DM/group display names while continuing to fill missing names.
• Adds regression coverage for group-DM preservation, channel renames, and filling a missing DM name.

Confidence Score: 5/5

The PR appears safe to merge, with the intended conflict-update behavior covered by focused regression tests.

The changed upsert preserves resolved DM/group metadata while retaining the existing update behavior for ordinary channels and missing names, and no concrete reachable regression remains.

Important Files Changed

Sequence Diagram

_{Reviews (1): Last reviewed commit: "fix(channels): a resolved DM keeps its k..." | Re-trigger Greptile}