Description

If the user provides a root-level llm config (e.g. Anthropic), the graph store ignores it and uses the hardcoded default OpenAI config instead. The user-provided LLM config only works for the graph store if it is redundantly specified under graphStore.llm.

Root cause (two problems in graph_memory.ts):

1. Default config override — defaults.ts hardcoded graphStore.llm to openai/gpt-4-turbo-preview. Since ConfigManager.mergeConfig shallow-spreads defaults first, this always overrode the user's root llm.provider.

2. Provider/config mismatch — The constructor resolved the LLM provider with correct precedence (graphStore.llm → root llm → "openai"), but always passed this.config.llm.config (root config) to LLMFactory.create, ignoring graphStore.llm.config entirely.

Fix:

• Remove the hardcoded default graphStore.llm from defaults.ts so the root llm naturally becomes the fallback.
• Make the config resolution in graph_memory.ts follow the same precedence as the provider resolution: use graphStore.llm.config when present, fall back to root llm.config.

Fixes #3425

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Added 7 new tests across two test files:

graph-memory-parsing.test.ts — 4 unit tests for MemoryGraph constructor (mocked LLMFactory):

• Root llm config propagates when no graphStore.llm is set
• graphStore.llm overrides root llm (both provider and config)
• Defensive fallback to root config when graphStore.llm.config is undefined
• Defaults to "openai" when no provider is set anywhere

config-manager.test.ts — 3 end-to-end tests through ConfigManager.mergeConfig:

• No default graphStore.llm exists after merge (root llm is the fallback)
• Explicit graphStore.llm is preserved when user provides it
• No graphStore.llm when user doesn't provide one

Full test suite results (511 tests across 33 suites — all pass):

• graph-memory-parsing.test.ts — 31 passed
• config-manager.test.ts — 26 passed
• graph-prompts.test.ts — 21 passed
• memory.init.test.ts — 5 passed
• memory.add.test.ts — 10 passed
• memory.crud.test.ts — 22 passed
• 15 other unit test files — 301 passed
• 7 client test files — 95 passed
• Build (with prettier check) passes

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes Nodejs SDK: Default llm config is used for graph store instead of user's root llm config #3425
• Made sure Checks passed

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