fix(schema): drop agents_organization_id_id_key — broke ON CONFLICT (id) callers

[buremba]

Why

PR #734 added a parallel `UNIQUE (organization_id, id)` on `agents` as schema-prep for the eventual per-org PK swap. It actively broke any `ON CONFLICT (id) DO NOTHING/UPDATE` callers.

Postgres semantics: `ON CONFLICT (X)` only suppresses violations of the unique constraint matching column set X. Adding a second unique constraint that overlaps with the PK means inserts can fail on the new constraint before reaching the PK conflict — and `ON CONFLICT (id)` doesn't catch the violation of the wider one.

Surfaced in the `tests/integration/.../race-mcp` test where parallel inserts of `(org-a, race-mcp-0)` started throwing `agents_organization_id_id_key` duplicates instead of being silently de-duped:

```
PostgresError: duplicate key value violates unique constraint
"agents_organization_id_id_key"
detail: Key (organization_id, id)=(org-a, race-mcp-0) already exists.
```

CI's `integration` job has been red on `main` since #734 merged for this reason.

Fix

Drop the constraint. The PK on `(id)` already enforces global uniqueness, which strictly subsumes `(organization_id, id)` uniqueness — the new constraint was logically redundant. Phase C of the per-org PK migration will swap the PK directly without needing a parallel constraint as a stepping stone.

Mirrored in `embedded-schema-patches.ts` (idempotent `DROP CONSTRAINT IF EXISTS`).

Test plan

• `bun run typecheck` clean.
• `dbmate up` applies cleanly against a fresh pgvector PG; `db/schema.sql` regenerated to match.
• CI `integration` job goes from red to green on this PR (the race-mcp test should stop throwing).

Summary by CodeRabbit

• Chores
  • Updated database schema to remove a constraint that was preventing certain database operations from functioning correctly. This change enables improved conflict resolution handling at the database level without affecting end-user functionality.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR removes the agents_organization_id_id_key unique constraint on (organization_id, id) from the agents table. The change includes a new migration that drops the constraint on upgrade and restores it on downgrade, updates the schema definition to reflect the removal, and aligns the embedded schema patches with the migration.

Changes

Remove conflicting agents constraint

Layer / File(s)	Summary
Migration to drop agents constraint db/migrations/20260515160000_drop_agents_org_id_unique.sql	New migration file provides up and down operations: migrate:up drops agents_organization_id_id_key, and migrate:down restores it with UNIQUE (organization_id, id). Comments explain the constraint interference with ON CONFLICT (id) usage.
Schema definition and migration registry db/schema.sql	Removes the agents_organization_id_id_key UNIQUE constraint from public.agents table definition and registers the new migration version 20260515160000 in the schema_migrations seed.
Embedded schema patch updates packages/server/src/db/embedded-schema-patches.ts	Modifies agents-per-org-pk-phase-a patch to remove the constraint-addition logic and add a note documenting that the earlier revision was reverted due to incompatibility with ON CONFLICT (id) call sites.

Possibly related PRs

• lobu-ai/lobu#734: The main PR that reversed the agents_organization_id_id_key (UNIQUE (organization_id, id)) constraint addition and updates the embedded patch accordingly.

Poem

🐰 A constraint that clashed with conflict handling,
Now dropped with care and thoughtful planning,
The agents table hops more free,
On conflicts of ID, it will agree,
With down-and-up to dance the dance! 🎭

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix(schema): drop agents_organization_id_id_key — broke ON CONFLICT (id) callers' is specific and directly describes the main change—removing a redundant database constraint that was breaking callers.
Description check	✅ Passed	The description comprehensively covers all required template sections: Why (clear motivation referencing PR #734 and Postgres semantics), Fix (explanation of the solution), and Test plan (typecheck, dbmate apply, and CI integration test expectations documented).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/drop-agents-redundant-unique

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