[delete-cloud]

Summary

• add a real LanceDB semantic memory backend alongside the existing fake backend
• wire [memory.semantic] backend = "lancedb" with db_path, table_name, and embedding_base_url
• persist semantic schema metadata and fail closed on schema drift or unversioned existing vector tables unless explicit rebuild is requested
• extend backend contract tests for LanceDB search/upsert/delete, scoped deletes, schema mismatch, schema rebuild, and app config wiring

Verification

• uv run pytest tests/coding_agent/test_memory_index_backend_contract.py tests/coding_agent/test_semantic_tape_index.py tests/coding_agent/test_semantic_sync.py tests/coding_agent/test_semantic_recall.py tests/coding_agent/test_memory_switch.py -q -> 96 passed
• uv run ruff format --check src/coding_agent/core/app.py src/coding_agent/topics/semantic_backends tests/coding_agent/test_memory_index_backend_contract.py tests/coding_agent/test_memory_switch.py && uv run ruff check src/coding_agent/core/app.py src/coding_agent/topics/semantic_backends tests/coding_agent/test_memory_index_backend_contract.py tests/coding_agent/test_memory_switch.py -> passed
• uv run pytest -q -> 3877 passed, 8 skipped, 20 xfailed
• local subagent review loop: initial P1 schema drift fixed, unversioned-table P1 fixed, blank-query guard P1 fixed, final P0/P1 review clean

Notes

AGENTS.md references RTK.md and prompts/codex-delegatee.md, but those files are absent in this worktree; I followed the visible repository instructions and kept the change scoped to backend integration.

Summary by CodeRabbit

• New Features
  • Added support for a new local semantic memory backend with persistent storage and scoped data management.
  • Expanded semantic memory configuration to include storage path, table name, and embedding endpoint settings.
  • Enabled selection of different semantic memory backends through configuration.
• Bug Fixes
  • Improved schema handling so existing memory stores are validated, rebuilt, or rejected more reliably when configurations change.
• Tests
  • Added coverage for backend creation, search, updates, deletion, schema mismatch behavior, rebuilds, and scoped deletes.

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

Semantic memory configuration now carries LanceDB storage and embedding settings, the registry builds backends from expanded factory config, and a new LanceDB-backed semantic memory implementation is added with contract coverage and integration tests.

Changes

Semantic memory LanceDB backend

Layer / File(s)	Summary
Config surface and app wiring coding-agent/src/coding_agent/core/app.py, coding-agent/src/coding_agent/topics/semantic_backends/base.py, coding-agent/src/coding_agent/topics/semantic_backends/__init__.py	SemanticMemoryConfig adds db_path, table_name, and embedding_base_url; backend types are re-exported, config parsing selects a backend-specific schema, and app startup passes the new fields into backend creation.
LanceDB backend implementation coding-agent/src/coding_agent/topics/semantic_backends/lancedb.py, coding-agent/tests/coding_agent/test_memory_index_backend_contract.py	A LanceDB semantic backend adds schema metadata storage, embeddings, vector search, scoped deletes, and contract tests for schema mismatch, rebuild, search, and delete behavior.
Registry factory and integration tests coding-agent/src/coding_agent/topics/semantic_backends/registry.py, coding-agent/tests/coding_agent/test_memory_switch.py	The backend registry now builds from SemanticBackendFactoryConfig, resolves local paths, registers fake and lancedb, and app wiring tests cover the updated initialization inputs.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• delete-cloud/Coding-Agent-Loop#618: Extends the semantic memory config and registry flow introduced here with LanceDB-specific fields and backend support.
• delete-cloud/Coding-Agent-Loop#627: Updates the same semantic backend creation path and app wiring; this PR adds the lancedb factory and expanded backend config.

Poem

I hopped through schemas by moonlit light,
and tucked new vectors out of sight.
With LanceDB my burrow feels neat,
a memory garden soft and sweet. 🐰

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the main change: adding a LanceDB semantic backend for memory.
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 feat/lancedb-semantic-memory-backend

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