Fix unbounded chat history leading to OOM (fixes #447)

[atul-upadhyay-7]

Closes #447

This PR adds a MAX_CHAT_HISTORY_SIZE configurable limit to prevent out-of-memory crashes due to unbounded chat histories. The limit is enforced across the active session memory, background persistence, and on-startup loads to ensure robust and bounded memory usage.

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📥 Commits

Reviewing files that changed from the base of the PR and between 42ae762 and 6ef0f87.

📒 Files selected for processing (3)

• .env.example
• rag-service/main.py
• rag-service/test_main.py

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a configurable cap on per-session chat history and enforces that cap when loading, appending, and persisting sessions to prevent unbounded growth.

Changes:

• Introduce MAX_CHAT_HISTORY_SIZE env var and document it in .env.example
• Truncate chat history to MAX_CHAT_HISTORY_SIZE exchanges during session load/save/snapshot and on append_chat_exchange
• Add a unit test for truncation behavior; disable an existing PDF worker test

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
rag-service/main.py	Enforces chat history truncation across load/save/snapshot and when appending new exchanges; adds MAX_CHAT_HISTORY_SIZE config
rag-service/test_main.py	Adds truncation test; comments out PDF worker test and removes worker import
.env.example	Documents MAX_CHAT_HISTORY_SIZE env var

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