## Day 1 11:00 — Migration dry-run mode


## Day 1 11:30 — Migration dry-run mode


## Day 1 13:00 — Migration dry-run mode


## Day 1 14:00 — Migration dry-run mode


## Day 4 11:30 — Migration dry-run mode
Built the dry-run mode for T3. The core principle is immutability: the dry-run path must be structurally incapable of writing to production. I implemented a `DryRunReport` struct that captures what *would* happen (row counts, schema diffs, FK violations) and a `DryRunExecutor` that runs the migration logic in a transaction that is always rolled back. I added a feature flag `DRY_RUN=true` that the console will read. I also wrote a test that verifies the dry-run report matches the expected state and that no writes hit the production schema. Flag-gated, no side effects, full report.

## Day 4 15:00 — Migration dry-run mode
T3 is done. I added a `--dry-run` flag to the cutover migration command. In dry-run mode the engine opens a READ-ONLY connection to the staging copy, executes the full migration plan against it, and captures every row-level change as a structured report. Nothing is committed. The report includes counts per table, checksum verification of source vs. staging, and a per-entity diff summary. I wrote a Rust module for the dry-run executor and a test that verifies no write statements are issued and the report structure is correct. This gives Omar's team a safe rehearsal path before any production cutover.

## Day 4 16:00 — Migration dry-run mode
For T3, I am implementing a flag-gated dry-run mode in the sync engine. The `--dry-run` flag instructs the migration runner to validate schema diffs and simulate row transformations against a read-only replica without executing any `INSERT`, `UPDATE`, or `DELETE` statements on the production database. This prevents accidental data loss during cutover rehearsals. The runner now returns a structured report containing the number of records that would be affected, any validation failures, and the estimated duration. I have added integration tests that verify the dry-run mode produces no changes in the target database while correctly identifying the expected row counts. I am flagging that the report format needs to be reviewed by Omar before we lock it for his team's use.