Best way to use codanna in a Rust workspace with dependent libraries?

[xD0135]

What's the best way to use codanna in a Rust workspace with dependent libraries? Let's use the following directory structure for example:

└── workspace
    ├── libA
    ├── libB
    └── binC

When working on binC I would like to have answers to both libA and libB without having to have the entire workspace loaded into my IDE or agent coding tool, but instead work directly on binC.

Both libA and libB have been index with codanna by executing codanna init and codanna index respectively, and I can get answers when interacting with each library individually in their directories:

libA % codanna mcp semantic_search_docs query:"how to ..." limit:3 
Found 3 semantically similar result(s) for 'how to ...':

1. with_... (Method) - Similarity: 0.449
   File: src/.../mod.rs:202
   Doc: Set the ...
   Signature: pub fn with_...(&mut self, key: Vec<u8>) -> &mut Self

2. with_message (Method) - Similarity: 0.353
   File: src/.../mod.rs:196
   Doc: Set the message...
   Signature: pub fn with_message(&mut self, message: Vec<u8>) -> &mut Self

3. ... (Function) - Similarity: 0.334
   File: src/.../mod.rs:430
   Doc: Arguments...
   Signature: pub fn function(...)

There seems to be a bug/issue when invoking codanna on a base directory that doesn't have an index while using a configuration file for a project that does (I'll file a separate issue for this):

binC % codanna -c ../libA/.codanna/settings.toml mcp semantic_search_docs query:"how to ..." limit:3
Warning: No configuration file found
Using default configuration for now.
Semantic search enabled (model: AllMiniLML6V2, threshold: 0.6)
Semantic search failed: Semantic search failed: No embeddings available for search

Any guidance on how to achieve this would be greatly appreciated. Thanks for this great project!

[bartolli]

Thanks for the great question! The best approach is to maintain a single codanna index at the workspace root rather than separate indexes for each library. Here are two ways to achieve what you want:

Option 1: Selective Indexing with .codannaignore

Create the codanna index at your workspace root and use .codannaignore to exclude folders you don't want indexed:

cd workspace
codanna init
# Edit .codannaignore to exclude any folders you don't need

# This will show you what is going to be indexed
codanna index . --dry-run

codanna index . --progress

Then you can query the single index from the project root:

codanna mcp semantic_search_docs query:"how to use libA" limit:3

Option 2: Index Specific Folders

Currently, codanna doesn't support indexing multiple directories in one run, it's on the roadmap, though. You can index only the libraries you need from the workspace root:

cd workspace
codanna init
codanna index libA --progress
codanna index libB --progress
# Don't index binC if you don't need it in the search results

This maintains a single index at workspace/.codanna/ containing both libA and libB.

The issue you encountered with -c ../libA/.codanna/settings.toml happens because codanna expects the index to be relative to where the settings file is located. By maintaining a single index at the workspace root, you avoid this complexity entirely.

[xD0135]

Thanks for the reply! Based on your recommendation of indexing the workspace, how would I configure the MCP when working only on binC then? Something like this I guess?

{
  "mcpServers": {
    "codanna": {
      "command": "cd /path/to/workspace && codanna",
      "args": ["serve", "--watch"]
    }
  }
}

[bartolli]

I have shipped a new version today (v0.5.14) that provides more flexibility to work with the MCP from anywhere outside your workspace.

Make sure you install the new version:

cargo install codanna --all-features --force

This will install and replace your current version. Then check the version with codanna --version to verify the upgrade.

Here's the best way to set up your workspace:

1. Delete the old .codanna folders in libA and libB (if they exist)
2. Remove the local .fastembed_cache folder (we moved the model to a new location that allows sharing the same model across projects)
3. From your workspace root, run codanna init to create a new config file and .fastembed_cache symlink
4. Index the libraries you need while working on binC. Either index them one by one:

codanna index libA --progress
codanna index libB --progress

Or index everything at once with codanna index . --progress (you can use .codannaignore to exclude folders you don't need indexed - this may take a few minutes depending on the size of your codebase)

Your structure will look like:

└── workspace
    ├── .codanna/              # Single index for entire workspace
    ├── .fastembed_cache       # Symlink to ~/.codanna/models/
    ├── libA
    ├── libB
    └── binC

Now you can spawn the server from anywhere in your system using the --config flag:

{
  "mcpServers": {
    "codanna": {
      "command": "codanna",
      "args": ["--config", "/absolute/path/to/your/workspace/.codanna/settings.toml", "serve", "--watch"]
    }
  }
}

Replace /absolute/path/to/your/workspace/ with your actual workspace path. The key improvement in v0.5.14 is that the --config flag now properly resolves all paths relative to the config file location, so you can work in binC from anywhere while having access to the entire workspace index.

Let me know if that works for you.

[xD0135]

This is awesome! Thank you so much for this amazing improvement! ❤️