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chore(docs): require migrations to survive a code rollback - #21420
Per team discussions, production migrations will move to being applied before the code that needs them, and won't be reverted if that code is rolled back. That isn't how it works today; this sets up development and review for it now.
This pull request
Adds .claude/rules/db-migrations.md: migrations in their own PR, safe single-release changes, expand → contract splits, data compatibility, and a train-tag check for contract steps
Adds a CLAUDE.md non-negotiable pointing to the rule
Flags rollback-unsafe migrations (HIGH), migrations bundled with code (MEDIUM), and premature contract steps in /fxa-review and /fxa-review-quick
Requires the backward-compatibility call in /fxa-ai-fixme-create-issue, /fxa-jira-feature-description, and /fxa-pr-open
If applicable, I have modified or added tests which pass locally.
I have added necessary documentation (if appropriate).
I have verified that my changes render correctly in RTL (if appropriate).
I have manually reviewed all AI generated code.
How to review (Optional)
Key files/areas to focus on: .claude/rules/db-migrations.md, especially the expand → contract table and the contract-step check
Suggested review order: the rule, then CLAUDE.md, then the skills
Risky or complex parts:
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Please attach the screenshots of the changes made in case of change in user interface.
Other information (Optional)
Follow-ups: FXA-14867 (drop reverse patches), FXA-14868 (test previous train against new schema), FXA-14869 (performance guidance).
No pre-merge review skill run; Claude config and markdown only.
Summary by CodeRabbit
Documentation
Updated database migration guidance to clarify compatibility expectations across production and upcoming releases, including rollback considerations and expand-and-contract steps for breaking changes.
Added migration planning and review requirements, including guidance on separating migrations from dependent code and documenting recovery plans when rollback could cause issues.
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It might also be useful to create a skill that the agents can call that does the rollback to verify that there are no breaking changes. This skill would start stack with your db changes, then attempt to start stack with previous migration. Something the agents can do to verify on the db level that it is not breaking.
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Filed FXA-14868. I framed it as applying the new migrations and then running the previous train's DB tests against them, since that checks N-1 code against the N schema.
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Maybe out of scope for this, but should we also consider adding guidance/scope for our migrations. I'm thinking specifically around making sure queries, columns, tables etc are performant at large(ish) scale. Obviously we don't want to expose exact numbers of our infra... but maybe scope creep too!
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Walkthrough
The PR adds database migration guidance for production compatibility, rollback behavior, and release sequencing. It also updates issue, PR, and review instructions to apply these requirements.
The migration rule and CLAUDE.md describe production-release compatibility, rollback considerations, separate migration changes, and expand-and-contract steps.
Apply policy to migration workflows .claude/skills/fxa-ai-fixme-create-issue/SKILL.md, .claude/skills/fxa-jira-feature-description/SKILL.md, .claude/skills/fxa-pr-open/SKILL.md, .claude/skills/fxa-review-quick/SKILL.md, .claude/skills/fxa-review/SKILL.md
Issue and feature-description guidance covers migration ticket scope and compatibility. PR-opening guidance requests migration notes. Review guidance checks compatibility, release sequencing, and bundled migrations.
This is guidance only, with no runtime change. Following it as written for column renames, unique constraints, or contract steps could still cause stale reads, failed constraint migrations, or approval of a contract step before its expand step is in production. Correct these three rules before merging.
Architecture risk: Low · up to b6992
The change affects 1 system.
Changed systems:CLAUDE.md
Architecture concerns
No architecture-level concerns identified.
Review details
Systems and components
observed — CLAUDE.md (service) was modified; 1 changed file maps to changed impact.
Before / after behavior
observed — Modified behavior in CLAUDE.md: Adds requirements that migrations remain compatible with the production release and survive code rollback, preferably ship separately from dependent code, and split breaking changes across releases using expand-and-contract; otherwise, the change must be flagged in the PR.
observed — Modified behavior in .claude/rules/db-migrations.md: Adds migration guidance covering applicable paths, release compatibility, separation of migration and code PRs, changes safe in one release, expand-and-contract sequences, train-tag checks for contract steps, row compatibility across releases, and required documentation when backward compatibility is not possible.
observed — Modified behavior in .claude/skills/fxa-ai-fixme-create-issue/SKILL.md: The migration guidance now requires the ticket to state backward compatibility with the production release and to scope a migration separately from code that uses it. For expand–contract migrations, it requires one step per ticket and, for a contract step, the release that shipped the expand step. The prohibition on editing a published migration remains unchanged.
observed — Modified behavior in .claude/skills/fxa-jira-feature-description/SKILL.md: The Constraints prompt now asks whether a migration is backward-compatible with the production release or needs an expand → contract split across tickets, references .claude/rules/db-migrations.md, and prefers a separate migration ticket.
Pre-merge checks: 5
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The title clearly and concisely describes the main change: documenting migration requirements for code rollback safety.
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Resolve merge conflict in branch skill-updates-db
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Actionable comments posted: 3
🪄 Fix comments: Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @.claude/rules/db-migrations.md:
- Line 38: Update the “Add a unique constraint” migration guidance to state that
deduplication happens only after release N-1 writers are drained, and require
that condition before adding the constraint.
- Around line 43-48: Update the contract-step verification guidance to check the
production database’s dbMetadata.schema-patch-level and require the expand patch
to be complete before applying the contract patch. Do not use the latest train
tag or /__version__ as a proxy for installed schema state.
- Line 35: Update the rename/type-change guidance in the data-compatibility
section to keep the old column authoritative while release N-1 may still write
only it; require backfill and synchronization verification before release N
switches reads to the new column.
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Because:
* Production migrations are moving to being applied before the code that needs them, and won't be reverted if that code is rolled back
This commit:
* Adds a db-migrations rule covering separate migration PRs, expand → contract splits, and data compatibility
* Adds a CLAUDE.md non-negotiable pointing to it
* Flags rollback-unsafe migrations, bundled migrations, and premature contract steps in fxa-review and fxa-review-quick
* Requires the compatibility call in ai-fixme tickets, feature tickets, and PR bodies
Because:
- Migrations may deploy ahead of their train, when prod can still be on an older release than the latest tag
This commit:
- Says to check against the production tag (`/__version__`) when a migration deploys ahead of its train
Closes: FXA-14866
Because:
- Release N-1 writing only the old column leaves a stale new column that release N reads
- Release N-1 can write duplicates after an expand-step dedupe
This commit:
- Keeps reads on the old column until the contract step for renames and type changes
- Moves the dedupe into the same patch as the unique constraint
Closes: FXA-14866
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Because
This pull request
.claude/rules/db-migrations.md: migrations in their own PR, safe single-release changes, expand → contract splits, data compatibility, and a train-tag check for contract stepsCLAUDE.mdnon-negotiable pointing to the rule/fxa-reviewand/fxa-review-quick/fxa-ai-fixme-create-issue,/fxa-jira-feature-description, and/fxa-pr-openIssue that this pull request solves
Closes: FXA-14866
Checklist
Put an
xin the boxes that applyHow to review (Optional)
.claude/rules/db-migrations.md, especially the expand → contract table and the contract-step checkCLAUDE.md, then the skillsScreenshots (Optional)
Please attach the screenshots of the changes made in case of change in user interface.
Other information (Optional)
Summary by CodeRabbit