Feature/agent memory kickoff

.agents/skills/README.md

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+# Skills Usage
+
+This repository stores Codex repo-level skills under `.agents/skills`.
+
+- Current working directory (`$CWD`) is the skill root scope for Codex repo-level loading.
+- Put shared repository skills here.
+- Keep skill-specific references under each skill folder (for example: `tidb-test-guidelines/references/`).

.agents/skills/tidb-test-guidelines/SKILL.md

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+---
+name: tidb-test-guidelines
+description: Decide where to place TiDB tests and how to write them (basic structure, naming, testdata usage). Use when asked about test locations, writing conventions, shard_count limits, casetest categorization, or when reviewing test changes in code review.
+---
+
+# TiDB Test Placement and Writing
+
+## Quick workflow
+
+1) Identify the target package and existing coverage using `rg --files -g '*_test.go'` and `rg --files -g '*.json'`.
+2) Check `BUILD.bazel` for `shard_count` in the target directory; keep test count <= 50 per directory.
+3) For optimizer cases, place new tests under `pkg/planner/core/casetest/<type>` (see `references/planner-guide.md`).
+4) Reuse existing fixtures and testdata; add new files only when necessary.
+5) Name tests descriptively; avoid issue-id-only names (e.g., `TestIssue123456`).
+6) Merge same-functionality cases into a single test only if runtime remains reasonable.
+7) When moving tests/benchmarks, update `BUILD.bazel` and `Makefile` (bench-daily) if needed.
+
+## Basic writing rules
+
+- Benchmarks (`func BenchmarkXxx`) are tests too; apply the same placement and naming rules (benchmarks do not count toward shard_count test limits).
+- Prefer table-driven tests for related scenarios in the same behavior area.
+- Reuse existing helper setups and test fixtures; avoid re-creating schemas unless required.
+- Prefer one `store` + one `testkit` per test; when a single test covers multiple scenarios, use distinct table names and restore any session/system variables to their original values.
+- If a test must use multiple sessions or domains (for example, cross-session cache behavior), keep the extra stores/testkits but document why in the test.
+- For follow-up bug fixes, prefer appending cases to existing tests/suites instead of creating new test files or new top-level tests, unless no semantically close suite exists.
+- In existing regression suites that are already sequential, keep sequential scenario blocks; do not introduce `t.Run` unless subtest isolation/parallel behavior is required by semantics.
+- Prefer exact assertions with `.Check(testkit.Rows(...))`; use `MultiCheckContain` only when output is inherently unstable, and add a short comment for why exact match is not practical.
+- Reuse table definitions only across semantically similar scenarios; if partition/index/DDL shape is the behavior under test, keep separate table schemas to avoid false positives.
+- Keep per-test runtime short; consolidate similar checks only if runtime stays reasonable.
+- Use behavior-based test names; never use issue-id-only names.
+- In test code, use the variable name `tk` for `*testkit.TestKit` (avoid `testKit`).
+- When merging multiple tests into one, keep a single `store` and a single `tk` unless multi-session behavior is required; do not create a new store/tk inside the same test body without a documented reason.
+
+## Placement rules
+
+- **Test count limit**: Keep <= 50 tests per directory; align with `shard_count` in the directory `BUILD.bazel` (benchmarks are excluded).
+
+## Reference files
+
+- **Package case maps** (when available): `references/<pkg>-case-map.md`
+- **Planner core placement guide**: `references/planner-guide.md`
+
+## Notes
+
+- Apply the same rules (placement, shard_count, naming) to other packages beyond `pkg/planner`.
+- Use existing testdata patterns (`*_in.json`, `*_out.json`, `*_xut.json`) in the same directory when extending suites. Use `-record -tags=intest,deadlock` only when the Go test suite explicitly supports `-record` and you need to regenerate outputs. For `tests/integrationtest`, use `pushd tests/integrationtest && ./run-tests.sh -r <TestName> && popd` (not `-record`).
+- For `pkg/planner/core/casetest/rule` predicate pushdown cases, keep SQL in `predicate_pushdown_suite_in.json` and record both `EXPLAIN format='brief'` and query results via the test runner (see `rule_predicate_pushdown_test.go`).
+- When moving benchmarks between packages, update any `TestBenchDaily` wrappers that list them and keep `Makefile` `bench-daily` entries aligned with the new package location.
+- When updating tests in any `pkg/*` package, update the corresponding case map under `references/` if it exists; do not block on missing case maps.
+- When updating tests in any other directory and the placement rules are non-obvious or recurring, consider adding/extending a case map under `references/` and updating this `SKILL.md`.
+- When merging issue regression tests into existing behavior tests, keep the issue id in SQL comments (e.g. `/* issue:12345 */`) or nearby comments for traceability.
+- Prefer unit tests over `tests/integrationtest` for end-to-end coverage unless you need to avoid union-storage executor differences or require full workflow validation.
+- When tests read source files under Bazel, use `go/runfiles` and ensure the target file is exported via `exports_files()` in its owning `BUILD.bazel`.
+- For Bazel runfiles, be ready to include the workspace prefix (from `TEST_WORKSPACE`) in the runfile path if needed.
+- Validation (Bazel): run `make bazel_prepare` first; then check the package `BUILD.bazel` for `@com_github_pingcap_failpoint//:failpoint` dependency.
+  - If present, run:
+    - `make bazel-failpoint-enable`
+    - `bazel test --norun_validations --define gotags=deadlock,intest --remote_cache=https://cache.hawkingrei.com/bazelcache --noremote_upload_local_results //path/to/package/...`
+    - `make bazel-failpoint-disable`
+  - If absent, run `bazel test` directly against the package path.

.agents/skills/tidb-test-guidelines/references/autoid_service-case-map.md

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+# TiDB autoid_service Test Case Map (pkg/autoid_service)
+
+## Overview
+
+- Grouped by package directory.
+- Each test file has a one-line description based on its primary test/benchmark name.
+- Testdata lists files under `testdata/` mapped to their owning package directory.
+
+## pkg/autoid_service
+
+### Tests
+- `pkg/autoid_service/autoid_test.go` - Tests concurrency.

.agents/skills/tidb-test-guidelines/references/bindinfo-case-map.md

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+# TiDB bindinfo Test Case Map (pkg/bindinfo)
+
+## Overview
+
+- Grouped by package directory.
+- Each test file has a one-line description based on its primary test/benchmark name.
+- Testdata lists files under `testdata/` mapped to their owning package directory.
+
+## pkg/bindinfo
+
+### Tests
+- `pkg/bindinfo/binding_auto_test.go` - Tests plan generation with stmt ctx.
+- `pkg/bindinfo/binding_cache_test.go` - Tests cross-DB binding cache.
+- `pkg/bindinfo/binding_operator_test.go` - Tests binding cache.
+- `pkg/bindinfo/binding_plan_evolution_test.go` - Tests rule-based plan performance predictor.
+- `pkg/bindinfo/binding_plan_generation_test.go` - Tests fix control adjustments.
+- `pkg/bindinfo/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/bindinfo/session_handle_test.go` - Tests global and session binding both exist.
+
+### Testdata
+- `pkg/bindinfo/testdata/binding_auto_suite_in.json`
+- `pkg/bindinfo/testdata/binding_auto_suite_out.json`
+
+## pkg/bindinfo/tests
+
+### Tests
+- `pkg/bindinfo/tests/bind_test.go` - Tests prepare cache with binding.
+- `pkg/bindinfo/tests/bind_usage_info_test.go` - Tests bind usage info.
+- `pkg/bindinfo/tests/cross_db_binding_test.go` - Tests cross-DB binding basics.
+- `pkg/bindinfo/tests/main_test.go` - Configures default goleak settings and registers testdata.

.agents/skills/tidb-test-guidelines/references/config-case-map.md

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+# TiDB config Test Case Map (pkg/config)
+
+## Overview
+
+- Grouped by package directory.
+- Each test file has a one-line description based on its primary test/benchmark name.
+- Testdata lists files under `testdata/` mapped to their owning package directory.
+
+## pkg/config
+
+### Tests
+- `pkg/config/config_test.go` - Tests atomic bool unmarshal.
+- `pkg/config/config_util_test.go` - Tests clone config.
+- `pkg/config/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/config/store_test.go` - Tests store type.
+
+## pkg/config/kerneltype
+
+### Tests
+- `pkg/config/kerneltype/type_test.go` - Tests kernel type.

.agents/skills/tidb-test-guidelines/references/ddl-case-map.md

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+# TiDB ddl Test Case Map (pkg/ddl)
+
+## Overview
+
+- Grouped by package directory.
+- Each test file has a one-line description based on its primary test/benchmark name.
+- Testdata lists files under `testdata/` mapped to their owning package directory.
+
+## pkg/ddl
+
+### Tests
+- `pkg/ddl/affinity_test.go` - ddl: Tests affinity build group definitions table.
+- `pkg/ddl/attributes_sql_test.go` - ddl: Tests alter table partition attributes.
+- `pkg/ddl/backfilling_dist_scheduler_test.go` - ddl: Tests backfilling scheduler local mode.
+- `pkg/ddl/backfilling_test.go` - ddl: Tests done task keeper.
+- `pkg/ddl/backfilling_txn_executor_test.go` - ddl: Tests expected ingest worker count.
+- `pkg/ddl/bdr_test.go` - ddl: Tests denied by BDR when add column.
+- `pkg/ddl/bench_test.go` - ddl: Tests extract datum by offsets.
+- `pkg/ddl/cancel_test.go` - ddl: Tests cancel various jobs.
+- `pkg/ddl/cluster_test.go` - ddl: Tests flashback close and reset PD schedule.
+- `pkg/ddl/column_change_test.go` - ddl: Tests column add.
+- `pkg/ddl/column_modify_test.go` - ddl: Tests add and drop column.
+- `pkg/ddl/column_test.go` - ddl: Tests column basic.
+- `pkg/ddl/column_type_change_test.go` - ddl: Tests column type change state between integer.
+- `pkg/ddl/constraint_test.go` - ddl: Tests alter constraint add drop.
+- `pkg/ddl/db_cache_test.go` - ddl: Tests alter table cache.
+- `pkg/ddl/db_change_failpoints_test.go` - ddl: Tests modify column type args.
+- `pkg/ddl/db_change_test.go` - ddl: Tests show create table.
+- `pkg/ddl/db_integration_test.go` - ddl: Tests create table if not exists like.
+- `pkg/ddl/db_rename_test.go` - ddl: Tests rename table with locked.
+- `pkg/ddl/db_table_test.go` - ddl: Tests add not null column.
+- `pkg/ddl/db_test.go` - ddl: Tests get time zone.
+- `pkg/ddl/ddl_algorithm_test.go` - ddl: Tests find alter algorithm.
+- `pkg/ddl/ddl_error_test.go` - ddl: Tests table error.
+- `pkg/ddl/ddl_history_test.go` - ddl: Tests DDL history basic.
+- `pkg/ddl/ddl_running_jobs_test.go` - ddl: Tests running jobs.
+- `pkg/ddl/ddl_test.go` - ddl: Tests get interval from policy.
+- `pkg/ddl/ddl_workerpool_test.go` - ddl: Tests DDL worker pool.
+- `pkg/ddl/executor_nokit_test.go` - ddl: Tests build query string from jobs.
+- `pkg/ddl/executor_test.go` - ddl: Tests get DDL jobs.
+- `pkg/ddl/export_test.go` - ddl: Tests export.
+- `pkg/ddl/fail_test.go` - ddl: Tests fail before decode args.
+- `pkg/ddl/foreign_key_test.go` - ddl: Tests foreign key.
+- `pkg/ddl/index_change_test.go` - ddl: Tests index change.
+- `pkg/ddl/index_cop_test.go` - ddl: Tests add index fetch rows from coprocessor.
+- `pkg/ddl/index_modify_test.go` - ddl: Tests add primary key1.
+- `pkg/ddl/index_nokit_test.go` - ddl: Tests modify task param loop.
+- `pkg/ddl/integration_test.go` - ddl: Tests DDL statements back fill.
+- `pkg/ddl/job_scheduler_test.go` - ddl: Tests must reload schemas.
+- `pkg/ddl/job_scheduler_testkit_test.go` - ddl: Tests DDL scheduling.
+- `pkg/ddl/job_submitter_test.go` - ddl: Tests gen ID and insert jobs with retry.
+- `pkg/ddl/job_worker_test.go` - ddl: Tests check owner.
+- `pkg/ddl/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/metabuild_test.go` - ddl: Tests new meta build context with session ctx.
+- `pkg/ddl/modify_column_test.go` - ddl: Tests modify column reorg info.
+- `pkg/ddl/multi_schema_change_test.go` - ddl: Tests multi schema change add columns cancelled.
+- `pkg/ddl/mv_index_test.go` - ddl: Tests multi valued index online DDL.
+- `pkg/ddl/options_test.go` - ddl: Tests options.
+- `pkg/ddl/owner_mgr_test.go` - ddl: Tests owner manager.
+- `pkg/ddl/partition_test.go` - ddl: Tests drop and truncate partition.
+- `pkg/ddl/placement_policy_ddl_test.go` - ddl: Tests placement policy in use.
+- `pkg/ddl/placement_policy_test.go` - ddl: Tests placement policy.
+- `pkg/ddl/placement_sql_test.go` - ddl: Tests create schema with placement.
+- `pkg/ddl/primary_key_handle_test.go` - ddl: Tests multi-region get table end handle.
+- `pkg/ddl/reorg_test.go` - ddl: Tests reorg ctx set max progress.
+- `pkg/ddl/repair_table_test.go` - ddl: Tests repair table.
+- `pkg/ddl/restart_test.go` - ddl: Tests schema resume.
+- `pkg/ddl/rollingback_test.go` - ddl: Tests cancel add index job error.
+- `pkg/ddl/schema_test.go` - ddl: Tests schema.
+- `pkg/ddl/schema_version_test.go` - ddl: Tests should check assumed server.
+- `pkg/ddl/sequence_test.go` - ddl: Tests create sequence.
+- `pkg/ddl/stat_test.go` - ddl: Tests get DDL info.
+- `pkg/ddl/table_mode_test.go` - ddl: Tests table mode basic.
+- `pkg/ddl/table_modify_test.go` - ddl: Tests lock table read only.
+- `pkg/ddl/table_split_test.go` - ddl: Tests table split.
+- `pkg/ddl/table_test.go` - ddl: Tests table.
+- `pkg/ddl/tiflash_replica_test.go` - ddl: Tests set table flash replica.
+- `pkg/ddl/ttl_test.go` - ddl: Tests get TTL info in options.
+
+## pkg/ddl/copr
+
+### Tests
+- `pkg/ddl/copr/copr_ctx_test.go` - ddl/copr: Tests new cop context single index.
+
+## pkg/ddl/ingest
+
+### Tests
+- `pkg/ddl/ingest/checkpoint_test.go` - ddl/ingest: Tests checkpoint manager.
+- `pkg/ddl/ingest/env_test.go` - ddl/ingest: Tests gen lightning data dir.
+- `pkg/ddl/ingest/integration_test.go` - ddl/ingest: Tests add index ingest generated columns.
+- `pkg/ddl/ingest/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/ingest/mem_root_test.go` - ddl/ingest: Tests memory root.
+
+## pkg/ddl/label
+
+### Tests
+- `pkg/ddl/label/attributes_test.go` - ddl/label: Tests new label.
+- `pkg/ddl/label/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/label/rule_test.go` - ddl/label: Tests apply attributes spec.
+
+## pkg/ddl/notifier
+
+### Tests
+- `pkg/ddl/notifier/events_test.go` - ddl/notifier: Tests event string.
+- `pkg/ddl/notifier/store_test.go` - ddl/notifier: Tests leftover when unmarshal.
+- `pkg/ddl/notifier/testkit_test.go` - ddl/notifier: Tests publish to table store.
+
+## pkg/ddl/placement
+
+### Tests
+- `pkg/ddl/placement/bundle_test.go` - ddl/placement: Tests empty.
+- `pkg/ddl/placement/common_test.go` - ddl/placement: Tests group.
+- `pkg/ddl/placement/constraint_test.go` - ddl/placement: Tests new from yaml.
+- `pkg/ddl/placement/constraints_test.go` - ddl/placement: Tests new constraints.
+- `pkg/ddl/placement/meta_bundle_test.go` - ddl/placement: Tests new table bundle.
+- `pkg/ddl/placement/rule_test.go` - ddl/placement: Tests clone.
+
+## pkg/ddl/schematracker
+
+### Tests
+- `pkg/ddl/schematracker/dm_tracker_test.go` - ddl/schematracker: Tests no num limit.
+- `pkg/ddl/schematracker/info_store_test.go` - ddl/schematracker: Tests info store lower case table names.
+
+## pkg/ddl/schemaver
+
+### Tests
+- `pkg/ddl/schemaver/syncer_nokit_test.go` - ddl/schemaver: Tests node versions.
+- `pkg/ddl/schemaver/syncer_test.go` - ddl/schemaver: Tests syncer simple.
+
+## pkg/ddl/serverstate
+
+### Tests
+- `pkg/ddl/serverstate/syncer_test.go` - ddl/serverstate: Tests state syncer simple.
+
+## pkg/ddl/session
+
+### Tests
+- `pkg/ddl/session/session_pool_test.go` - ddl/session: Tests session pool.
+
+## pkg/ddl/systable
+
+### Tests
+- `pkg/ddl/systable/manager_test.go` - ddl/systable: Tests manager.
+- `pkg/ddl/systable/min_job_id_test.go` - ddl/systable: Tests refresh min job ID.
+
+## pkg/ddl/tests/adminpause
+
+### Tests
+- `pkg/ddl/tests/adminpause/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/tests/adminpause/pause_cancel_test.go` - ddl/tests/adminpause: Tests pause cancel and rerun schema stmt.
+- `pkg/ddl/tests/adminpause/pause_negative_test.go` - ddl/tests/adminpause: Tests pause on write conflict.
+- `pkg/ddl/tests/adminpause/pause_resume_test.go` - ddl/tests/adminpause: Tests pause and resume schema stmt.
+
+## pkg/ddl/tests/fail
+
+### Tests
+- `pkg/ddl/tests/fail/fail_db_test.go` - ddl/tests/fail: Tests halfway cancel operations.
+- `pkg/ddl/tests/fail/main_test.go` - Configures default goleak settings and registers testdata.
+
+## pkg/ddl/tests/fastcreatetable
+
+### Tests
+- `pkg/ddl/tests/fastcreatetable/fastcreatetable_test.go` - ddl/tests/fastcreatetable: Tests switch fast create table.
+- `pkg/ddl/tests/fastcreatetable/main_test.go` - Configures default goleak settings and registers testdata.
+
+## pkg/ddl/tests/fk
+
+### Tests
+- `pkg/ddl/tests/fk/foreign_key_test.go` - ddl/tests/fk: Tests create table with foreign key meta info.
+- `pkg/ddl/tests/fk/main_test.go` - Configures default goleak settings and registers testdata.
+
+## pkg/ddl/tests/indexmerge
+
+### Tests
+- `pkg/ddl/tests/indexmerge/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/tests/indexmerge/merge_test.go` - ddl/tests/indexmerge: Tests add index merge process.
+
+## pkg/ddl/tests/metadatalock
+
+### Tests
+- `pkg/ddl/tests/metadatalock/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/tests/metadatalock/mdl_test.go` - ddl/tests/metadatalock: Tests MDL basic select.
+
+## pkg/ddl/tests/multivaluedindex
+
+### Tests
+- `pkg/ddl/tests/multivaluedindex/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/tests/multivaluedindex/multi_valued_index_test.go` - ddl/tests/multivaluedindex: Tests create multi-valued index has binary collation.
+
+## pkg/ddl/tests/partition
+
+### Tests
+- `pkg/ddl/tests/partition/db_partition_test.go` - ddl/tests/partition: Tests create table with partition.
+- `pkg/ddl/tests/partition/error_injection_test.go` - ddl/tests/partition: Tests truncate partition list failures with global index.
+- `pkg/ddl/tests/partition/exchange_partition_test.go` - ddl/tests/partition: Tests exchange range columns partition.
+- `pkg/ddl/tests/partition/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/tests/partition/multi_domain_test.go` - ddl/tests/partition: Tests multi schema reorganize partition issue56819.
+- `pkg/ddl/tests/partition/placement_test.go` - ddl/tests/partition: Tests partition by with placement.
+- `pkg/ddl/tests/partition/reorg_partition_test.go` - ddl/tests/partition: Tests reorg partition failures.
+
+## pkg/ddl/tests/serial
+
+### Tests
+- `pkg/ddl/tests/serial/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/tests/serial/serial_test.go` - ddl/tests/serial: Tests issue23872.
+
+## pkg/ddl/tests/tiflash
+
+### Tests
+- `pkg/ddl/tests/tiflash/ddl_tiflash_test.go` - ddl/tests/tiflash: Tests TiFlash no redundant PD rules.
+- `pkg/ddl/tests/tiflash/main_test.go` - Configures default goleak settings and registers testdata.
+
+## pkg/ddl/util
+
+### Tests
+- `pkg/ddl/util/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/ddl/util/util_test.go` - ddl/util: Tests folder not empty.

.agents/skills/tidb-test-guidelines/references/distsql-case-map.md

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+# TiDB DistSQL Test Case Map (pkg/distsql)
+
+## Overview
+
+- Grouped by package directory.
+- Each test file has a one-line description based on its primary test/benchmark name.
+- Testdata lists files under `testdata/` mapped to their owning package directory.
+
+## pkg/distsql
+
+### Tests
+- `pkg/distsql/bench_test.go` - Tests large chunk responses for select.
+- `pkg/distsql/context_test.go` - Tests context.
+- `pkg/distsql/distsql_test.go` - Tests normal select.
+- `pkg/distsql/main_test.go` - Configures default goleak settings and registers testdata.
+- `pkg/distsql/request_builder_test.go` - Tests table handles to KV ranges.
+- `pkg/distsql/select_result_test.go` - Tests update coprocessor runtime stats.
+
+## pkg/distsql/context
+
+### Tests
+- `pkg/distsql/context/context_test.go` - Tests context detach.