fix(backend/copilot): prevent title update from overwriting session messages

[majdyz]

Changes 🏗️

Fixes a race condition in update_session_title() where the background title generation task could overwrite the Redis session cache with a stale snapshot, causing the copilot to "forget" its previous turns.

Root cause: update_session_title() performs a read-modify-write on the Redis cache (read full session → set title → write back). Meanwhile, upsert_chat_session() writes a newer version with more messages during streaming. If the title task reads early (e.g., 34 messages) and writes late (after streaming persisted 101 messages), the stale 34-message version overwrites the 101-message version. When the next message lands on a different pod, it loads the stale session from Redis.

Fix: Replace the read-modify-write with a simple cache invalidation (invalidate_session_cache). The title is already updated in the DB; the next access just reloads from DB with the correct title and messages. No locks, no deserialization of the full session blob, no risk of stale overwrites.

Evidence from prod logs (session 41a3814c):

• Pod tm2jb persisted session with 101 messages
• Pod phflm loaded session from Redis cache with only 35 messages (66 messages lost)
• The title background task ran between these events, overwriting the cache

Checklist 📋

For code changes:

• I have clearly listed my changes in the PR description
• I have made a test plan
• I have tested my changes according to the test plan:
  • poetry run pytest backend/copilot/model_test.py — 15/15 pass
  • All pre-commit hooks pass (ruff, black, isort, pyright)
  • After deploy: verify long sessions no longer lose context on multi-pod setups

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• autogpt_platform/backend/backend/copilot/model.py

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🧰 Additional context used

📓 Path-based instructions (4)

autogpt_platform/backend/**/*.py

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

autogpt_platform/backend/**/*.py: Use Python 3.11 (required; managed by Poetry via pyproject.toml) for backend development
Always run 'poetry run format' (Black + isort) before linting in backend development
Always run 'poetry run lint' (ruff) after formatting in backend development

Files:

• autogpt_platform/backend/backend/copilot/model.py

autogpt_platform/backend/**/*.{py,txt}

📄 CodeRabbit inference engine (autogpt_platform/backend/CLAUDE.md)

Use poetry run prefix for all Python commands, including testing, linting, formatting, and migrations

Files:

• autogpt_platform/backend/backend/copilot/model.py

autogpt_platform/backend/backend/**/*.py

📄 CodeRabbit inference engine (autogpt_platform/backend/CLAUDE.md)

Use Prisma ORM for database operations in PostgreSQL with pgvector for embeddings

Files:

• autogpt_platform/backend/backend/copilot/model.py

autogpt_platform/**/*.py

📄 CodeRabbit inference engine (AGENTS.md)

Format Python code with poetry run format

Files:

• autogpt_platform/backend/backend/copilot/model.py

🧠 Learnings (4)

📓 Common learnings

Learnt from: Pwuts
Repo: Significant-Gravitas/AutoGPT PR: 12284
File: autogpt_platform/frontend/src/app/api/openapi.json:11897-11900
Timestamp: 2026-03-04T23:58:09.319Z
Learning: Repo: Significant-Gravitas/AutoGPT — PR `#12284`
Backend/frontend OpenAPI codegen convention: In backend/api/features/store/model.py, the StoreSubmission and StoreSubmissionAdminView models define submitted_at: datetime | None, changes_summary: str | None, and instructions: str | None with no default. This is intentional to produce “required but nullable” fields in OpenAPI (properties appear in required[] and use anyOf [type, null]). This matches Prisma’s submittedAt DateTime? and changesSummary String?. Do not flag this as a required/nullable mismatch.

📚 Learning: 2026-02-26T17:02:22.448Z

Learnt from: Pwuts
Repo: Significant-Gravitas/AutoGPT PR: 12211
File: .pre-commit-config.yaml:160-179
Timestamp: 2026-02-26T17:02:22.448Z
Learning: Keep the pre-commit hook pattern broad for autogpt_platform/backend to ensure OpenAPI schema changes are captured. Do not narrow to backend/api/ alone, since the generated schema depends on Pydantic models across multiple directories (backend/data/, backend/blocks/, backend/copilot/, backend/integrations/, backend/util/). Narrowing could miss schema changes and cause frontend type desynchronization.

Applied to files:

• autogpt_platform/backend/backend/copilot/model.py

📚 Learning: 2026-03-04T08:04:35.881Z

Learnt from: majdyz
Repo: Significant-Gravitas/AutoGPT PR: 12273
File: autogpt_platform/backend/backend/copilot/tools/workspace_files.py:216-220
Timestamp: 2026-03-04T08:04:35.881Z
Learning: In the AutoGPT Copilot backend, ensure that SVG images are not treated as vision image types by excluding 'image/svg+xml' from INLINEABLE_MIME_TYPES and MULTIMODAL_TYPES in tool_adapter.py; the Claude API supports PNG, JPEG, GIF, and WebP for vision. SVGs (XML text) should be handled via the text path instead, not the vision path.

Applied to files:

• autogpt_platform/backend/backend/copilot/model.py

📚 Learning: 2026-03-05T15:42:08.207Z

Learnt from: ntindle
Repo: Significant-Gravitas/AutoGPT PR: 12297
File: .claude/skills/backend-check/SKILL.md:14-16
Timestamp: 2026-03-05T15:42:08.207Z
Learning: In Python files under autogpt_platform/backend (recursively), rely on poetry run format to perform formatting (Black + isort) and linting (ruff). Do not run poetry run lint as a separate step after poetry run format, since format already includes linting checks.

Applied to files:

• autogpt_platform/backend/backend/copilot/model.py

🔇 Additional comments (1)

autogpt_platform/backend/backend/copilot/model.py (1)

708-711: Good change: cache invalidation avoids stale session overwrite.

Replacing cache read-modify-write with invalidate_session_cache(session_id) removes the overwrite vector while still letting the updated title load from DB on next access.

---

Walkthrough

Replaced an in-place cached-session update in update_session_title with a cache invalidation call (invalidate_session_cache(session_id)), removing the previous read-modify-write cache mutation and its surrounding error handling so the cache will be reloaded from the DB on next access.

Changes

Cohort / File(s)	Summary
Cache invalidation change autogpt_platform/backend/backend/copilot/model.py	Replaced in-place cached session mutation and surrounding error handling in update_session_title with a call to invalidate_session_cache(session_id) after successful DB update; removed read-modify-write cache update logic.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• 0ubbe
• Torantulino
• kcze

Poem

🐰🌿 I nudged the cache and hopped away,
A DB-first bloom will greet the day.
No furtive writes to stale, shared ground,
Now fresh truth springs when next looked round.
🥕✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main fix: preventing title updates from overwriting session messages, which is the core issue resolved in this PR.
Description check	✅ Passed	The description is comprehensive and directly related to the changeset, explaining the race condition, root cause, the fix implemented, and providing production evidence.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

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• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/copilot-session-overwrite-on-empty-result

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[github-actions]

🔍 PR Overlap Detection

This check compares your PR against all other open PRs targeting the same branch to detect potential merge conflicts early.

🔴 Merge Conflicts Detected

The following PRs have been tested and will have merge conflicts if merged after this PR. Consider coordinating with the authors.

• feat(copilot): UX improvements #12258 (kcze · updated 3h ago)
  • 📁 autogpt_platform/backend/backend/copilot/
    • model.py (1 conflict, ~19 lines)

Summary: 1 conflict(s), 0 medium risk, 0 low risk (out of 1 PRs with file overlap)

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Auto-generated on push. Ignores: openapi.json, lock files.