init: archlens — architecture diagram generator

Hex arch + DDD, tree-sitter parsing, Mermaid/ASCII output.
Supports Rust + Python. 92 tests. CI, diff, --check for staleness detection.

.gitea/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: CI
+
+on:
+  push:
+    branches: ["**"]
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: 1
+
+jobs:
+  check:
+    name: Check / Test
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: ${{ runner.os }}-cargo-
+
+      - name: fmt
+        run: cargo fmt --all -- --check
+
+      - name: clippy
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: test
+        run: cargo test

.gitignore

@@ -0,0 +1 @@
+target/

CONTEXT.md

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+# Archlens — Domain Glossary
+
+> This file defines the canonical language of the Archlens domain. No implementation details — just terms and their meanings.
+
+## Core Concepts
+
+- **CodeGraph**: The aggregate root. A complete representation of a codebase's architecture — all elements, relationships, and module groupings. Can produce filtered subgraphs of itself by module.
+
+- **CodeElement**: A type-level construct in source code — a class, struct, trait, interface, or enum. Carries a name, kind, location (file + line), visibility, generic parameters, and attributes/decorators.
+
+- **Relationship**: A directed edge between two CodeElements. Has a kind (inheritance or composition) and references source and target elements.
+
+- **Module**: A logical grouping of CodeElements. By default inferred from directory structure, overridable via configuration. Represented as metadata on each CodeElement (`module_path`), not a separate hierarchy.
+
+- **Language**: The programming language of a source file. A closed set: Rust, CSharp, Python. Determines which analysis strategy is used.
+
+- **SourceFile**: A file to be analyzed. Carries a FilePath and its detected Language.
+
+## Analysis
+
+- **AnalysisResult**: The output of analyzing a single file — extracted CodeElements, Relationships, and any AnalysisWarnings.
+
+- **AnalysisWarning**: A non-fatal problem encountered during analysis — unparseable construct, unsupported syntax, etc. Carries file path, line, and message.
+
+- **AnalysisConfig**: Settings that control what gets analyzed — path excludes, granularity level, module-to-directory mappings.
+
+## Output
+
+- **RenderOutput**: The result of rendering a CodeGraph — a collection of RenderedFiles.
+
+- **RenderedFile**: A single output artifact — a named file with content (e.g., `overview.mmd` with Mermaid syntax).
+
+- **OutputConfig**: Settings that control rendering — format, output path, whether to split by module.
+
+## Relationships (kinds)
+
+- **Inheritance**: A type extends or implements another type (class extends class, struct implements trait, class implements interface).
+
+- **Composition**: A type owns or depends on another type via a field, property, or constructor-injected dependency.
+
+## Metadata on CodeElements
+
+- **Visibility**: Whether a type is public, private, internal, or other access level. Used as a filterable property, not shown on diagrams by default.
+
+- **Generics**: Type parameters on a CodeElement. Stored with the element, displayed in simplified form (e.g., `Repository<Order>` not full generic constraints).
+
+- **Attributes**: Decorators, annotations, or attributes on a type (e.g., `[ApiController]`, `#[derive(Clone)]`, `@dataclass`). Stored as metadata, usable for categorization and filtering.
+
+## Diagram Levels
+
+- **Project level**: Dependencies between projects, crates, or packages. Rendered as a flowchart.
+
+- **Module level**: Dependencies between logical modules (directory-based groupings). Rendered as a flowchart with subgraphs.
+
+- **Type level**: Individual types with their inheritance and composition relationships. Rendered as a UML class diagram.

Cargo.toml

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+[workspace]
+resolver = "2"
+members = [
+    "crates/domain",
+    "crates/application",
+    "crates/presentation",
+    "crates/adapters/tree-sitter",
+    "crates/adapters/walkdir",
+    "crates/adapters/mermaid",
+    "crates/adapters/ascii",
+    "crates/adapters/file-writer",
+    "crates/adapters/stdout-writer",
+    "crates/adapters/toml-config",
+    "crates/adapters/cargo-workspace",
+]
+
+[workspace.dependencies]
+# Internal crates
+archlens-domain = { path = "crates/domain" }
+archlens-application = { path = "crates/application" }
+archlens-tree-sitter = { path = "crates/adapters/tree-sitter" }
+archlens-walkdir = { path = "crates/adapters/walkdir" }
+archlens-mermaid = { path = "crates/adapters/mermaid" }
+archlens-ascii = { path = "crates/adapters/ascii" }
+archlens-file-writer = { path = "crates/adapters/file-writer" }
+archlens-stdout-writer = { path = "crates/adapters/stdout-writer" }
+archlens-toml-config = { path = "crates/adapters/toml-config" }
+archlens-cargo-workspace = { path = "crates/adapters/cargo-workspace" }
+
+# Error handling
+thiserror = "2"
+anyhow = "1"
+
+# Parsing
+tree-sitter = "0.24"
+tree-sitter-rust = "0.23"
+tree-sitter-python = "0.23"
+tree-sitter-c-sharp = "0.23"
+
+# File discovery
+walkdir = "2"
+ignore = "0.4"
+
+# Config
+toml = "0.8"
+serde = { version = "1", features = ["derive"] }
+
+# CLI
+clap = { version = "4", features = ["derive"] }
+
+# Observability
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+
+# Parallelism
+rayon = "1"
+
+# Testing
+tempfile = "3"

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Gabriel Kaszewski
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Makefile

@@ -0,0 +1,28 @@
+.DEFAULT_GOAL := check
+
+# Run the full local check suite — same order as CI would.
+check: fmt-check clippy test
+	@echo "✅ All checks passed"
+
+# Apply rustfmt to all files.
+fmt:
+	cargo fmt
+
+# Check formatting without modifying files (CI-safe).
+fmt-check:
+	cargo fmt --check
+
+# Run Clippy and treat warnings as errors.
+clippy:
+	cargo clippy -- -D warnings
+
+# Run the test suite.
+test:
+	cargo test
+
+# Apply fmt + clippy auto-fixes in one shot.
+fix:
+	cargo fmt
+	cargo clippy --fix --allow-dirty --allow-staged
+
+.PHONY: check fmt fmt-check clippy test fix

README.md

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+# archlens
+
+Generate architecture diagrams from source code. Runs on CI to keep docs fresh.
+
+Supports Rust and Python. Produces Mermaid or ASCII output.
+
+## Install
+
+```bash
+cargo install --path crates/presentation
+```
+
+## Usage
+
+```bash
+# Module-level dependency graph (default)
+archlens .
+
+# Project-level (crate/package dependencies from manifests)
+archlens . --level project
+
+# Type-level class diagram
+archlens . --level type
+
+# Write to file
+archlens . --output docs/architecture.mmd
+
+# Split by module (one file per module + overview)
+archlens . --level type --split-by-module --output docs/arch/
+
+# ASCII output to terminal
+archlens . --format ascii
+
+# Scope to a subtree
+archlens . --scope src/domain
+
+# Exclude directories
+archlens . --exclude tests/ --exclude generated/
+
+# Verbose logging
+archlens . -v    # info
+archlens . -vv   # debug
+```
+
+## CI Integration
+
+Check if committed diagrams are up to date:
+
+```bash
+archlens . --level project --check --output docs/architecture.mmd
+```
+
+Exit code 1 if the diagram has changed. Use `--strict` to also fail on parse warnings.
+
+Compare current state against an existing file:
+
+```bash
+archlens diff docs/architecture.mmd --level project
+```
+
+## Config
+
+Generate a config file:
+
+```bash
+archlens init
+```
+
+Creates `archlens.toml`:
+
+```toml
+[analysis]
+exclude = ["tests/", "vendor/", "generated/"]
+level = "module"
+
+[modules]
+# "src/infra" = "Infrastructure"
+
+[output]
+format = "mermaid"
+# path = "docs/architecture.mmd"
+split_by_module = false
+```
+
+## Diagram Levels
+
+| Level | What it shows | Source |
+|-------|--------------|--------|
+| `project` | Crate/package dependencies | `Cargo.toml` |
+| `module` | Module-level dependency graph | Imports + manifest deps |
+| `type` | Class diagram with fields, methods, relationships | Source code (tree-sitter) |
+
+## Supported Languages
+
+| Language | Types | Inheritance | Composition | Imports |
+|----------|-------|-------------|-------------|---------|
+| Rust | struct, enum, trait | `impl Trait for Type` | struct fields | `use`, `mod` |
+| Python | class | `class Foo(Bar)` | `__init__` params, type annotations | `import`, `from ... import` |
+| C# | planned | - | - | - |
+
+## Architecture
+
+Built with hexagonal architecture (ports and adapters) + DDD.
+
+```
+crates/
+  domain/           # Core model, zero external deps
+  application/      # Use cases, orchestration
+  adapters/
+    tree-sitter/    # Source code parsing (Rust, Python)
+    cargo-workspace/ # Cargo.toml dependency extraction
+    walkdir/        # File discovery
+    mermaid/        # Mermaid diagram output
+    ascii/          # Terminal output
+    file-writer/    # Write to disk
+    stdout-writer/  # Write to stdout
+    toml-config/    # Config file parsing
+  presentation/     # CLI (clap), composition root
+```
+
+## License
+
+MIT

crates/adapters/ascii/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "archlens-ascii"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true

crates/adapters/ascii/src/ascii_renderer.rs

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+use std::collections::HashMap;
+
+use archlens_domain::{
+    CodeElement, CodeGraph, DomainError, RelationshipKind, RenderOutput, RenderedFile,
+    ports::DiagramRenderer,
+};
+
+pub struct AsciiRenderer;
+
+impl Default for AsciiRenderer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl AsciiRenderer {
+    pub fn new() -> Self {
+        Self
+    }
+
+    fn format_kind(element: &CodeElement) -> &'static str {
+        match element.kind() {
+            archlens_domain::CodeElementKind::Class => "cls",
+            archlens_domain::CodeElementKind::Struct => "str",
+            archlens_domain::CodeElementKind::Trait => "trt",
+            archlens_domain::CodeElementKind::Interface => "ifc",
+            archlens_domain::CodeElementKind::Enum => "enm",
+            archlens_domain::CodeElementKind::Project => "prj",
+        }
+    }
+}
+
+impl DiagramRenderer for AsciiRenderer {
+    fn render(&self, graph: &CodeGraph) -> Result<RenderOutput, DomainError> {
+        let mut lines = Vec::new();
+
+        let total_elements = graph.elements().len();
+        let total_rels = graph.relationships().len();
+        let total_modules = graph.modules().len();
+
+        lines.push("╔══════════════════════════════════════╗".to_string());
+        lines.push("║         Architecture Overview        ║".to_string());
+        lines.push("╠══════════════════════════════════════╣".to_string());
+        lines.push(format!(
+            "║  Elements: {:<5}  Modules: {:<5}   ║",
+            total_elements, total_modules
+        ));
+        lines.push(format!("║  Relationships: {:<19} ║", total_rels));
+        lines.push("╚══════════════════════════════════════╝".to_string());
+
+        if graph.elements().is_empty() {
+            lines.push("  (no elements found)".to_string());
+            let content = lines.join("\n");
+            let file = RenderedFile::new("diagram.txt", &content)?;
+            return Ok(RenderOutput::single(file));
+        }
+
+        let mut grouped: HashMap<String, Vec<&CodeElement>> = HashMap::new();
+        let mut ungrouped: Vec<&CodeElement> = Vec::new();
+
+        for element in graph.elements() {
+            if let Some(module) = element.module() {
+                grouped
+                    .entry(module.as_str().to_string())
+                    .or_default()
+                    .push(element);
+            } else {
+                ungrouped.push(element);
+            }
+        }
+
+        if !ungrouped.is_empty() {
+            lines.push(String::new());
+            lines.push("┌─ (ungrouped)".to_string());
+            for el in &ungrouped {
+                lines.push(format!("│  [{}] {}", Self::format_kind(el), el.name()));
+            }
+            lines.push("└───".to_string());
+        }
+
+        let mut module_names: Vec<&String> = grouped.keys().collect();
+        module_names.sort();
+
+        for module in module_names {
+            let elements = &grouped[module];
+            lines.push(String::new());
+            lines.push(format!("┌─ {} ({} types)", module, elements.len()));
+            lines.push("│".to_string());
+            for (i, el) in elements.iter().enumerate() {
+                let prefix = if i == elements.len() - 1 {
+                    "└──"
+                } else {
+                    "├──"
+                };
+                let generics = if el.generics().is_empty() {
+                    String::new()
+                } else {
+                    format!("<{}>", el.generics().join(", "))
+                };
+                lines.push(format!(
+                    "│  {} [{}] {}{}",
+                    prefix,
+                    Self::format_kind(el),
+                    el.name(),
+                    generics
+                ));
+            }
+            lines.push("└───".to_string());
+        }
+
+        let non_import_rels: Vec<_> = graph
+            .relationships()
+            .iter()
+            .filter(|r| r.kind() != RelationshipKind::Import)
+            .collect();
+
+        if !non_import_rels.is_empty() {
+            lines.push(String::new());
+            lines.push("── Relationships ──".to_string());
+            for rel in &non_import_rels {
+                let arrow = match rel.kind() {
+                    RelationshipKind::Inheritance => "extends",
+                    RelationshipKind::Composition => "has",
+                    RelationshipKind::Import => "imports",
+                };
+                lines.push(format!(
+                    "  {} ─[{}]─> {}",
+                    rel.source(),
+                    arrow,
+                    rel.target()
+                ));
+            }
+        }
+
+        let import_rels: Vec<_> = graph
+            .relationships()
+            .iter()
+            .filter(|r| r.kind() == RelationshipKind::Import)
+            .collect();
+
+        if !import_rels.is_empty() {
+            lines.push(String::new());
+            lines.push(format!("── Imports ({}) ──", import_rels.len()));
+            for rel in &import_rels {
+                lines.push(format!("  {} ···> {}", rel.source(), rel.target()));
+            }
+        }
+
+        let content = lines.join("\n");
+        let file = RenderedFile::new("diagram.txt", &content)?;
+        Ok(RenderOutput::single(file))
+    }
+}

crates/adapters/ascii/src/lib.rs

@@ -0,0 +1,3 @@
+mod ascii_renderer;
+
+pub use ascii_renderer::AsciiRenderer;

crates/adapters/ascii/tests/ascii_renderer_tests.rs

@@ -0,0 +1,48 @@
+use archlens_ascii::AsciiRenderer;
+use archlens_domain::{
+    CodeElement, CodeElementKind, CodeGraph, FilePath, Relationship, RelationshipKind,
+    ports::DiagramRenderer,
+};
+
+#[test]
+fn renders_elements_and_relationships_as_text() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/service.rs").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "Order",
+            CodeElementKind::Struct,
+            FilePath::new("src/order.rs").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_relationship(
+        Relationship::new("OrderService", "Order", RelationshipKind::Composition).unwrap(),
+    );
+
+    let renderer = AsciiRenderer::new();
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("OrderService"));
+    assert!(content.contains("Order"));
+    assert!(content.contains("has"));
+}
+
+#[test]
+fn empty_graph_produces_header_only() {
+    let renderer = AsciiRenderer::new();
+    let output = renderer.render(&CodeGraph::new()).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("Architecture"));
+}

crates/adapters/cargo-workspace/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "archlens-cargo-workspace"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+toml.workspace = true
+serde.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/adapters/cargo-workspace/src/cargo_workspace_analyzer.rs

@@ -0,0 +1,123 @@
+use std::collections::{HashMap, HashSet};
+use std::path::Path;
+
+use serde::Deserialize;
+
+use archlens_domain::{
+    CodeElement, CodeElementKind, CodeGraph, DomainError, FilePath, ModuleName, Relationship,
+    RelationshipKind, ports::ProjectAnalyzer,
+};
+
+pub struct CargoWorkspaceAnalyzer;
+
+impl Default for CargoWorkspaceAnalyzer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl CargoWorkspaceAnalyzer {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+#[derive(Deserialize)]
+struct WorkspaceToml {
+    workspace: Option<WorkspaceSection>,
+}
+
+#[derive(Deserialize)]
+struct WorkspaceSection {
+    #[serde(default)]
+    members: Vec<String>,
+}
+
+#[derive(Deserialize)]
+struct MemberToml {
+    package: Option<PackageSection>,
+    #[serde(default)]
+    dependencies: HashMap<String, toml::Value>,
+}
+
+#[derive(Deserialize)]
+struct PackageSection {
+    name: String,
+}
+
+impl ProjectAnalyzer for CargoWorkspaceAnalyzer {
+    fn analyze(&self, root: &Path) -> Result<CodeGraph, DomainError> {
+        let workspace_toml_path = root.join("Cargo.toml");
+        let content = std::fs::read_to_string(&workspace_toml_path)
+            .map_err(|e| DomainError::IoError(e.to_string()))?;
+        let workspace: WorkspaceToml =
+            toml::from_str(&content).map_err(|e| DomainError::ConfigError(e.to_string()))?;
+
+        let members = workspace.workspace.map(|w| w.members).unwrap_or_default();
+
+        let mut graph = CodeGraph::new();
+        let mut name_set: HashSet<String> = HashSet::new();
+        let mut member_names: Vec<(String, String)> = Vec::new(); // (member_path, package_name)
+
+        for member_path in &members {
+            let member_cargo = root.join(member_path).join("Cargo.toml");
+            let member_content = std::fs::read_to_string(&member_cargo)
+                .map_err(|e| DomainError::IoError(e.to_string()))?;
+            let member: MemberToml = toml::from_str(&member_content)
+                .map_err(|e| DomainError::ConfigError(e.to_string()))?;
+
+            let package_name = member
+                .package
+                .map(|p| p.name)
+                .unwrap_or_else(|| member_path.clone());
+
+            name_set.insert(package_name.clone());
+            member_names.push((member_path.clone(), package_name));
+        }
+
+        for (member_path, package_name) in &member_names {
+            let file_path = FilePath::new(&format!("{}/Cargo.toml", member_path))
+                .map_err(|e| DomainError::IoError(e.to_string()))?;
+
+            let mut element =
+                CodeElement::new(package_name, CodeElementKind::Project, file_path, 1)?;
+
+            if let Some(module) = infer_group(member_path) {
+                element = element.with_module(module);
+            }
+
+            graph.add_element(element);
+        }
+
+        for (member_path, package_name) in &member_names {
+            let member_cargo = root.join(member_path).join("Cargo.toml");
+            let member_content = std::fs::read_to_string(&member_cargo)
+                .map_err(|e| DomainError::IoError(e.to_string()))?;
+            let member: MemberToml = toml::from_str(&member_content)
+                .map_err(|e| DomainError::ConfigError(e.to_string()))?;
+
+            for dep_name in member.dependencies.keys() {
+                let normalized = dep_name.replace('_', "-");
+                if name_set.contains(&normalized)
+                    && let Ok(rel) =
+                        Relationship::new(package_name, &normalized, RelationshipKind::Composition)
+                {
+                    graph.add_relationship(rel);
+                }
+            }
+        }
+
+        Ok(graph)
+    }
+}
+
+fn infer_group(member_path: &str) -> Option<ModuleName> {
+    let parts: Vec<&str> = member_path.split('/').collect();
+    if parts.len() < 3 {
+        return None;
+    }
+
+    let group = parts[parts.len() - 2];
+    let capitalized = format!("{}{}", group[..1].to_uppercase(), &group[1..]);
+    ModuleName::new(&capitalized).ok()
+}

crates/adapters/cargo-workspace/src/lib.rs

@@ -0,0 +1,3 @@
+mod cargo_workspace_analyzer;
+
+pub use cargo_workspace_analyzer::CargoWorkspaceAnalyzer;

crates/adapters/cargo-workspace/tests/cargo_workspace_tests.rs

@@ -0,0 +1,132 @@
+use std::fs;
+
+use archlens_cargo_workspace::CargoWorkspaceAnalyzer;
+use archlens_domain::{CodeElementKind, RelationshipKind, ports::ProjectAnalyzer};
+
+fn create_workspace(dir: &std::path::Path) {
+    fs::write(
+        dir.join("Cargo.toml"),
+        r#"
+[workspace]
+members = ["crates/domain", "crates/application", "crates/adapters/sqlite"]
+"#,
+    )
+    .unwrap();
+
+    fs::create_dir_all(dir.join("crates/domain/src")).unwrap();
+    fs::write(
+        dir.join("crates/domain/Cargo.toml"),
+        r#"
+[package]
+name = "myapp-domain"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+"#,
+    )
+    .unwrap();
+    fs::write(dir.join("crates/domain/src/lib.rs"), "").unwrap();
+
+    fs::create_dir_all(dir.join("crates/application/src")).unwrap();
+    fs::write(
+        dir.join("crates/application/Cargo.toml"),
+        r#"
+[package]
+name = "myapp-application"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+myapp-domain = { path = "../domain" }
+"#,
+    )
+    .unwrap();
+    fs::write(dir.join("crates/application/src/lib.rs"), "").unwrap();
+
+    fs::create_dir_all(dir.join("crates/adapters/sqlite/src")).unwrap();
+    fs::write(
+        dir.join("crates/adapters/sqlite/Cargo.toml"),
+        r#"
+[package]
+name = "myapp-sqlite"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+myapp-domain = { path = "../../domain" }
+"#,
+    )
+    .unwrap();
+    fs::write(dir.join("crates/adapters/sqlite/src/lib.rs"), "").unwrap();
+}
+
+#[test]
+fn discovers_workspace_members_as_project_elements() {
+    let dir = tempfile::tempdir().unwrap();
+    create_workspace(dir.path());
+
+    let analyzer = CargoWorkspaceAnalyzer::new();
+    let graph = analyzer.analyze(dir.path()).unwrap();
+
+    assert_eq!(graph.elements().len(), 3);
+    assert!(
+        graph
+            .elements()
+            .iter()
+            .all(|e| e.kind() == CodeElementKind::Project)
+    );
+
+    let names: Vec<&str> = graph.elements().iter().map(|e| e.name()).collect();
+    assert!(names.contains(&"myapp-domain"));
+    assert!(names.contains(&"myapp-application"));
+    assert!(names.contains(&"myapp-sqlite"));
+}
+
+#[test]
+fn extracts_dependencies_between_workspace_members() {
+    let dir = tempfile::tempdir().unwrap();
+    create_workspace(dir.path());
+
+    let analyzer = CargoWorkspaceAnalyzer::new();
+    let graph = analyzer.analyze(dir.path()).unwrap();
+
+    assert_eq!(graph.relationships().len(), 2);
+    assert!(
+        graph
+            .relationships()
+            .iter()
+            .all(|r| r.kind() == RelationshipKind::Composition)
+    );
+
+    let deps: Vec<(&str, &str)> = graph
+        .relationships()
+        .iter()
+        .map(|r| (r.source(), r.target()))
+        .collect();
+    assert!(deps.contains(&("myapp-application", "myapp-domain")));
+    assert!(deps.contains(&("myapp-sqlite", "myapp-domain")));
+}
+
+#[test]
+fn assigns_module_from_directory_grouping() {
+    let dir = tempfile::tempdir().unwrap();
+    create_workspace(dir.path());
+
+    let analyzer = CargoWorkspaceAnalyzer::new();
+    let graph = analyzer.analyze(dir.path()).unwrap();
+
+    let sqlite = graph
+        .elements()
+        .iter()
+        .find(|e| e.name() == "myapp-sqlite")
+        .unwrap();
+    assert_eq!(sqlite.module().unwrap().as_str(), "Adapters");
+
+    let domain = graph
+        .elements()
+        .iter()
+        .find(|e| e.name() == "myapp-domain")
+        .unwrap();
+    assert!(domain.module().is_none() || domain.module().unwrap().as_str() != "Adapters");
+}

crates/adapters/file-writer/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "archlens-file-writer"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/adapters/file-writer/src/file_output_writer.rs

@@ -0,0 +1,52 @@
+use std::fs;
+use std::path::PathBuf;
+
+use archlens_domain::{DomainError, RenderOutput, ports::OutputWriter};
+
+pub struct FileOutputWriter {
+    output_path: OutputPath,
+}
+
+enum OutputPath {
+    Directory(PathBuf),
+    File(PathBuf),
+}
+
+impl FileOutputWriter {
+    pub fn new(output_dir: PathBuf) -> Self {
+        Self {
+            output_path: OutputPath::Directory(output_dir),
+        }
+    }
+
+    pub fn single_file(path: PathBuf) -> Self {
+        Self {
+            output_path: OutputPath::File(path),
+        }
+    }
+}
+
+impl OutputWriter for FileOutputWriter {
+    fn write(&self, output: &RenderOutput) -> Result<(), DomainError> {
+        match &self.output_path {
+            OutputPath::File(path) => {
+                if let Some(parent) = path.parent() {
+                    fs::create_dir_all(parent).map_err(|e| DomainError::IoError(e.to_string()))?;
+                }
+                let content = output.files().first().map(|f| f.content()).unwrap_or("");
+                fs::write(path, content).map_err(|e| DomainError::IoError(e.to_string()))?;
+            }
+            OutputPath::Directory(dir) => {
+                fs::create_dir_all(dir).map_err(|e| DomainError::IoError(e.to_string()))?;
+
+                for file in output.files() {
+                    let path = dir.join(file.name());
+                    fs::write(&path, file.content())
+                        .map_err(|e| DomainError::IoError(e.to_string()))?;
+                }
+            }
+        }
+
+        Ok(())
+    }
+}

crates/adapters/file-writer/src/lib.rs

@@ -0,0 +1,3 @@
+mod file_output_writer;
+
+pub use file_output_writer::FileOutputWriter;

crates/adapters/file-writer/tests/file_writer_tests.rs

@@ -0,0 +1,35 @@
+use std::fs;
+
+use archlens_domain::{RenderOutput, RenderedFile, ports::OutputWriter};
+use archlens_file_writer::FileOutputWriter;
+
+#[test]
+fn writes_single_file_to_directory() {
+    let dir = tempfile::tempdir().unwrap();
+    let writer = FileOutputWriter::new(dir.path().to_path_buf());
+
+    let file = RenderedFile::new("arch.mmd", "classDiagram").unwrap();
+    let output = RenderOutput::single(file);
+
+    writer.write(&output).unwrap();
+
+    let content = fs::read_to_string(dir.path().join("arch.mmd")).unwrap();
+    assert_eq!(content, "classDiagram");
+}
+
+#[test]
+fn writes_multiple_files_to_directory() {
+    let dir = tempfile::tempdir().unwrap();
+    let writer = FileOutputWriter::new(dir.path().to_path_buf());
+
+    let files = vec![
+        RenderedFile::new("overview.mmd", "graph TD").unwrap(),
+        RenderedFile::new("orders.mmd", "classDiagram").unwrap(),
+    ];
+    let output = RenderOutput::new(files);
+
+    writer.write(&output).unwrap();
+
+    assert!(dir.path().join("overview.mmd").exists());
+    assert!(dir.path().join("orders.mmd").exists());
+}

crates/adapters/mermaid/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "archlens-mermaid"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true

crates/adapters/mermaid/src/lib.rs

@@ -0,0 +1,3 @@
+mod mermaid_renderer;
+
+pub use mermaid_renderer::MermaidRenderer;

crates/adapters/mermaid/src/mermaid_renderer.rs

@@ -0,0 +1,266 @@
+use std::collections::{HashMap, HashSet};
+
+use archlens_domain::{
+    CodeElement, CodeGraph, DiagramLevel, DomainError, RelationshipKind, RenderOutput,
+    RenderedFile, Visibility, ports::DiagramRenderer,
+};
+
+pub struct MermaidRenderer {
+    level: DiagramLevel,
+}
+
+impl Default for MermaidRenderer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl MermaidRenderer {
+    pub fn new() -> Self {
+        Self {
+            level: DiagramLevel::Type,
+        }
+    }
+
+    pub fn with_level(level: DiagramLevel) -> Self {
+        Self { level }
+    }
+
+    fn format_element_name(element: &CodeElement) -> String {
+        let name = element.name();
+        if element.generics().is_empty() {
+            name.to_string()
+        } else {
+            format!("{}~{}~", name, element.generics().join(", "))
+        }
+    }
+
+    fn format_visibility(visibility: Visibility) -> &'static str {
+        match visibility {
+            Visibility::Public => "public",
+            Visibility::Private => "private",
+            Visibility::Internal => "internal",
+        }
+    }
+
+    fn render_class_diagram(&self, graph: &CodeGraph) -> String {
+        let mut lines = vec!["classDiagram".to_string()];
+
+        let mut grouped: HashMap<String, Vec<&CodeElement>> = HashMap::new();
+        let mut ungrouped: Vec<&CodeElement> = Vec::new();
+
+        for element in graph.elements() {
+            if let Some(module) = element.module() {
+                grouped
+                    .entry(module.as_str().to_string())
+                    .or_default()
+                    .push(element);
+            } else {
+                ungrouped.push(element);
+            }
+        }
+
+        let has_namespaces = !grouped.is_empty();
+
+        let mut seen: HashSet<String> = HashSet::new();
+        for element in &ungrouped {
+            if seen.insert(element.name().to_string()) {
+                Self::push_class_lines(&mut lines, element, "    ");
+            }
+        }
+
+        if has_namespaces {
+            for (namespace, elements) in &grouped {
+                lines.push(format!("    namespace {namespace} {{"));
+                let mut ns_seen: HashSet<String> = HashSet::new();
+                for element in elements {
+                    if ns_seen.insert(element.name().to_string()) {
+                        Self::push_class_lines(&mut lines, element, "        ");
+                    }
+                }
+                lines.push("    }".to_string());
+            }
+        }
+
+        let mut rel_seen: HashSet<String> = HashSet::new();
+        for rel in graph.relationships() {
+            if rel.kind() == RelationshipKind::Import {
+                continue;
+            }
+            let arrow = match rel.kind() {
+                RelationshipKind::Inheritance => "<|--",
+                RelationshipKind::Composition => "-->",
+                RelationshipKind::Import => "..>",
+            };
+            let key = format!("{} {} {}", rel.source(), arrow, rel.target());
+            if rel_seen.insert(key.clone()) {
+                lines.push(format!("    {key}"));
+            }
+        }
+
+        lines.join("\n")
+    }
+
+    fn push_class_lines(lines: &mut Vec<String>, element: &CodeElement, indent: &str) {
+        lines.push(format!(
+            "{indent}class {}",
+            Self::format_element_name(element)
+        ));
+        if element.visibility() != Visibility::Public {
+            lines.push(format!(
+                "{indent}<<{}>> {}",
+                Self::format_visibility(element.visibility()),
+                element.name()
+            ));
+        }
+        let name = element.name();
+        for field in element.fields() {
+            lines.push(format!("{indent}{name} : {field}"));
+        }
+        for method in element.methods() {
+            lines.push(format!("{indent}{name} : {method}"));
+        }
+    }
+
+    fn render_module_flowchart(&self, graph: &CodeGraph) -> String {
+        let mut lines = vec!["graph TD".to_string()];
+
+        let mut name_to_modules: HashMap<&str, HashSet<&str>> = HashMap::new();
+        let mut file_to_module: HashMap<String, String> = HashMap::new();
+        let mut modules: HashSet<String> = HashSet::new();
+
+        for element in graph.elements() {
+            if let Some(module) = element.module() {
+                name_to_modules
+                    .entry(element.name())
+                    .or_default()
+                    .insert(module.as_str());
+                modules.insert(module.as_str().to_string());
+
+                let file_stem = std::path::Path::new(element.file_path().as_str())
+                    .file_stem()
+                    .and_then(|s| s.to_str())
+                    .unwrap_or("");
+                if !file_stem.is_empty() {
+                    file_to_module.insert(file_stem.to_string(), module.as_str().to_string());
+                }
+            }
+        }
+
+        for module in &modules {
+            lines.push(format!("    {module}[{module}]"));
+        }
+
+        let mut module_edges: HashSet<(String, String)> = HashSet::new();
+        for rel in graph.relationships() {
+            match rel.kind() {
+                RelationshipKind::Import => {
+                    let source_mod = file_to_module.get(rel.source());
+                    let target_top = rel.target().split('.').next().unwrap_or("");
+                    let target_mod = Self::capitalize(target_top);
+
+                    if let Some(src) = source_mod
+                        && modules.contains(&target_mod)
+                        && *src != target_mod
+                    {
+                        module_edges.insert((src.clone(), target_mod));
+                    }
+                }
+                _ => {
+                    if modules.contains(rel.source())
+                        && modules.contains(rel.target())
+                        && rel.source() != rel.target()
+                    {
+                        module_edges.insert((rel.source().to_string(), rel.target().to_string()));
+                        continue;
+                    }
+
+                    let src_mods = name_to_modules.get(rel.source());
+                    let tgt_mods = name_to_modules.get(rel.target());
+
+                    if let (Some(src_set), Some(tgt_set)) = (src_mods, tgt_mods) {
+                        for src_mod in src_set {
+                            if tgt_set.contains(src_mod) {
+                                continue;
+                            }
+                            for tgt_mod in tgt_set {
+                                if src_mod != tgt_mod {
+                                    module_edges.insert((src_mod.to_string(), tgt_mod.to_string()));
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        for (source, target) in &module_edges {
+            lines.push(format!("    {source} --> {target}"));
+        }
+
+        lines.join("\n")
+    }
+
+    fn capitalize(s: &str) -> String {
+        if s.is_empty() {
+            return String::new();
+        }
+        format!("{}{}", s[..1].to_uppercase(), &s[1..])
+    }
+
+    fn render_project_flowchart(&self, graph: &CodeGraph) -> String {
+        let mut lines = vec!["graph TD".to_string()];
+
+        let mut grouped: HashMap<String, Vec<&CodeElement>> = HashMap::new();
+        let mut ungrouped: Vec<&CodeElement> = Vec::new();
+
+        for element in graph.elements() {
+            if let Some(module) = element.module() {
+                grouped
+                    .entry(module.as_str().to_string())
+                    .or_default()
+                    .push(element);
+            } else {
+                ungrouped.push(element);
+            }
+        }
+
+        for element in &ungrouped {
+            let id = Self::sanitize_id(element.name());
+            lines.push(format!("    {id}[{}]", element.name()));
+        }
+
+        for (group, elements) in &grouped {
+            lines.push(format!("    subgraph {group}"));
+            for element in elements {
+                let id = Self::sanitize_id(element.name());
+                lines.push(format!("        {id}[{}]", element.name()));
+            }
+            lines.push("    end".to_string());
+        }
+
+        for rel in graph.relationships() {
+            let source_id = Self::sanitize_id(rel.source());
+            let target_id = Self::sanitize_id(rel.target());
+            lines.push(format!("    {source_id} --> {target_id}"));
+        }
+
+        lines.join("\n")
+    }
+
+    fn sanitize_id(name: &str) -> String {
+        name.replace(['-', '.'], "_")
+    }
+}
+
+impl DiagramRenderer for MermaidRenderer {
+    fn render(&self, graph: &CodeGraph) -> Result<RenderOutput, DomainError> {
+        let content = match self.level {
+            DiagramLevel::Type => self.render_class_diagram(graph),
+            DiagramLevel::Module => self.render_module_flowchart(graph),
+            DiagramLevel::Project => self.render_project_flowchart(graph),
+        };
+        let file = RenderedFile::new("diagram.mmd", &content)?;
+        Ok(RenderOutput::single(file))
+    }
+}

crates/adapters/mermaid/tests/mermaid_renderer_tests.rs

@@ -0,0 +1,328 @@
+use archlens_domain::{
+    CodeElement, CodeElementKind, CodeGraph, DiagramLevel, FilePath, ModuleName, Relationship,
+    RelationshipKind, Visibility, ports::DiagramRenderer,
+};
+use archlens_mermaid::MermaidRenderer;
+
+fn build_type_level_graph() -> CodeGraph {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/service.rs").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "Order",
+            CodeElementKind::Struct,
+            FilePath::new("src/order.rs").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_relationship(
+        Relationship::new("OrderService", "Order", RelationshipKind::Composition).unwrap(),
+    );
+    graph
+}
+
+#[test]
+fn renders_class_diagram_with_elements_and_composition() {
+    let renderer = MermaidRenderer::new();
+    let output = renderer.render(&build_type_level_graph()).unwrap();
+
+    let content = output.files()[0].content();
+    assert!(content.contains("classDiagram"));
+    assert!(content.contains("class OrderService"));
+    assert!(content.contains("class Order"));
+    assert!(content.contains("OrderService --> Order"));
+}
+
+#[test]
+fn inheritance_uses_different_arrow() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "Animal",
+            CodeElementKind::Class,
+            FilePath::new("src/animal.rs").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "Dog",
+            CodeElementKind::Class,
+            FilePath::new("src/dog.rs").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_relationship(
+        Relationship::new("Dog", "Animal", RelationshipKind::Inheritance).unwrap(),
+    );
+
+    let renderer = MermaidRenderer::new();
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("Dog <|-- Animal"));
+}
+
+#[test]
+fn elements_show_kind_and_generics() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "Repository",
+            CodeElementKind::Trait,
+            FilePath::new("src/repo.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_generics(vec!["T".to_string()]),
+    );
+
+    let renderer = MermaidRenderer::new();
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("class Repository~T~"));
+}
+
+#[test]
+fn private_elements_show_visibility_annotation() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "InternalHelper",
+            CodeElementKind::Class,
+            FilePath::new("src/helper.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_visibility(Visibility::Private),
+    );
+
+    let renderer = MermaidRenderer::new();
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("class InternalHelper"));
+    assert!(content.contains("<<private>>"));
+}
+
+#[test]
+fn renders_module_level_flowchart() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/orders/service.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "BillingService",
+            CodeElementKind::Class,
+            FilePath::new("src/billing/service.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Billing").unwrap()),
+    );
+    graph.add_relationship(
+        Relationship::new(
+            "OrderService",
+            "BillingService",
+            RelationshipKind::Composition,
+        )
+        .unwrap(),
+    );
+
+    let renderer = MermaidRenderer::with_level(DiagramLevel::Module);
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("graph TD"));
+    assert!(content.contains("Orders"));
+    assert!(content.contains("Billing"));
+    assert!(content.contains("Orders --> Billing"));
+}
+
+#[test]
+fn empty_graph_produces_valid_diagram() {
+    let renderer = MermaidRenderer::new();
+    let output = renderer.render(&CodeGraph::new()).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("classDiagram"));
+}
+
+#[test]
+fn project_level_renders_subgraphs_for_grouped_projects() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "myapp-domain",
+            CodeElementKind::Project,
+            FilePath::new("crates/domain/Cargo.toml").unwrap(),
+            1,
+        )
+        .unwrap(),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "myapp-sqlite",
+            CodeElementKind::Project,
+            FilePath::new("crates/adapters/sqlite/Cargo.toml").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Adapters").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "myapp-nats",
+            CodeElementKind::Project,
+            FilePath::new("crates/adapters/nats/Cargo.toml").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Adapters").unwrap()),
+    );
+    graph.add_relationship(
+        Relationship::new(
+            "myapp-sqlite",
+            "myapp-domain",
+            RelationshipKind::Composition,
+        )
+        .unwrap(),
+    );
+
+    let renderer = MermaidRenderer::with_level(DiagramLevel::Project);
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("graph TD"));
+    assert!(content.contains("subgraph Adapters"));
+    assert!(content.contains("myapp-sqlite"));
+    assert!(content.contains("myapp-nats"));
+    assert!(content.contains("myapp-domain"));
+    assert!(content.contains("-->"));
+}
+
+#[test]
+fn type_level_groups_elements_by_module() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/orders/service.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "Order",
+            CodeElementKind::Struct,
+            FilePath::new("src/orders/order.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "Invoice",
+            CodeElementKind::Struct,
+            FilePath::new("src/billing/invoice.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Billing").unwrap()),
+    );
+
+    let renderer = MermaidRenderer::new();
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    assert!(content.contains("namespace Orders"));
+    assert!(content.contains("namespace Billing"));
+    assert!(content.contains("OrderService"));
+    assert!(content.contains("Invoice"));
+}
+
+#[test]
+fn module_level_aggregates_cross_module_deps_into_single_arrow() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/orders/service.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "OrderRepo",
+            CodeElementKind::Trait,
+            FilePath::new("src/orders/repo.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "DbPool",
+            CodeElementKind::Struct,
+            FilePath::new("src/infra/db.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Infra").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "SqliteRepo",
+            CodeElementKind::Struct,
+            FilePath::new("src/infra/sqlite.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Infra").unwrap()),
+    );
+    // Two types in Orders depend on two types in Infra
+    graph.add_relationship(
+        Relationship::new("OrderService", "DbPool", RelationshipKind::Composition).unwrap(),
+    );
+    graph.add_relationship(
+        Relationship::new("OrderRepo", "SqliteRepo", RelationshipKind::Composition).unwrap(),
+    );
+
+    let renderer = MermaidRenderer::with_level(DiagramLevel::Module);
+    let output = renderer.render(&graph).unwrap();
+    let content = output.files()[0].content();
+
+    let arrow_count = content.matches("Orders --> Infra").count();
+    assert_eq!(
+        arrow_count, 1,
+        "should have exactly one aggregated arrow, got:\n{content}"
+    );
+}

crates/adapters/stdout-writer/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "archlens-stdout-writer"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true

crates/adapters/stdout-writer/src/lib.rs

@@ -0,0 +1,3 @@
+mod stdout_output_writer;
+
+pub use stdout_output_writer::StdoutOutputWriter;

crates/adapters/stdout-writer/src/stdout_output_writer.rs

@@ -0,0 +1,24 @@
+use archlens_domain::{DomainError, RenderOutput, ports::OutputWriter};
+
+pub struct StdoutOutputWriter;
+
+impl Default for StdoutOutputWriter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl StdoutOutputWriter {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl OutputWriter for StdoutOutputWriter {
+    fn write(&self, output: &RenderOutput) -> Result<(), DomainError> {
+        for file in output.files() {
+            println!("{}", file.content());
+        }
+        Ok(())
+    }
+}

crates/adapters/stdout-writer/tests/stdout_writer_tests.rs

@@ -0,0 +1,12 @@
+use archlens_domain::{RenderOutput, RenderedFile, ports::OutputWriter};
+use archlens_stdout_writer::StdoutOutputWriter;
+
+#[test]
+fn writes_without_error() {
+    let writer = StdoutOutputWriter::new();
+    let file = RenderedFile::new("arch.mmd", "classDiagram").unwrap();
+    let output = RenderOutput::single(file);
+
+    let result = writer.write(&output);
+    assert!(result.is_ok());
+}

crates/adapters/toml-config/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "archlens-toml-config"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+toml.workspace = true
+serde.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/adapters/toml-config/src/lib.rs

@@ -0,0 +1,3 @@
+mod toml_config_loader;
+
+pub use toml_config_loader::TomlConfigLoader;

crates/adapters/toml-config/src/toml_config_loader.rs

@@ -0,0 +1,81 @@
+use std::collections::HashMap;
+use std::path::Path;
+
+use serde::Deserialize;
+
+use archlens_domain::{
+    AnalysisConfig, DiagramLevel, DomainError, OutputConfig, ports::ConfigLoader,
+};
+
+#[derive(Debug, Deserialize, Default)]
+struct RawConfig {
+    #[serde(default)]
+    analysis: RawAnalysis,
+    #[serde(default)]
+    output: RawOutput,
+    #[serde(default)]
+    modules: HashMap<String, String>,
+}
+
+#[derive(Debug, Deserialize, Default)]
+struct RawAnalysis {
+    #[serde(default)]
+    exclude: Vec<String>,
+    #[serde(default)]
+    level: Option<String>,
+}
+
+#[derive(Debug, Deserialize, Default)]
+struct RawOutput {
+    #[serde(default)]
+    #[allow(dead_code)]
+    format: Option<String>,
+    #[serde(default)]
+    path: Option<String>,
+    #[serde(default)]
+    split_by_module: bool,
+}
+
+#[derive(Default)]
+pub struct TomlConfigLoader {
+    raw: RawConfig,
+}
+
+impl TomlConfigLoader {
+    pub fn from_path(path: &Path) -> Result<Self, DomainError> {
+        let content =
+            std::fs::read_to_string(path).map_err(|e| DomainError::IoError(e.to_string()))?;
+        let raw: RawConfig =
+            toml::from_str(&content).map_err(|e| DomainError::ConfigError(e.to_string()))?;
+        Ok(Self { raw })
+    }
+
+    fn parse_level(level: &Option<String>) -> DiagramLevel {
+        match level.as_deref() {
+            Some("type") => DiagramLevel::Type,
+            Some("project") => DiagramLevel::Project,
+            _ => DiagramLevel::Module,
+        }
+    }
+}
+
+impl ConfigLoader for TomlConfigLoader {
+    fn load_analysis_config(&self) -> Result<AnalysisConfig, DomainError> {
+        let config = AnalysisConfig::default()
+            .with_excludes(self.raw.analysis.exclude.clone())
+            .with_level(Self::parse_level(&self.raw.analysis.level))
+            .with_module_mappings(self.raw.modules.clone());
+        Ok(config)
+    }
+
+    fn load_output_config(&self) -> Result<OutputConfig, DomainError> {
+        let mut config =
+            OutputConfig::default().with_split_by_module(self.raw.output.split_by_module);
+
+        if let Some(path) = &self.raw.output.path {
+            config = config.with_output_path(path.clone());
+        }
+
+        Ok(config)
+    }
+}

crates/adapters/toml-config/tests/toml_config_tests.rs

@@ -0,0 +1,68 @@
+use std::fs;
+
+use archlens_domain::{DiagramLevel, ports::ConfigLoader};
+use archlens_toml_config::TomlConfigLoader;
+
+#[test]
+fn loads_analysis_config_from_toml_file() {
+    let dir = tempfile::tempdir().unwrap();
+    let config_path = dir.path().join("archlens.toml");
+    fs::write(
+        &config_path,
+        r#"
+[analysis]
+exclude = ["tests/", "vendor/"]
+level = "type"
+
+[modules]
+"src/orders" = "Orders"
+"src/billing" = "Billing"
+"#,
+    )
+    .unwrap();
+
+    let loader = TomlConfigLoader::from_path(&config_path).unwrap();
+    let config = loader.load_analysis_config().unwrap();
+
+    assert_eq!(config.excludes(), &["tests/", "vendor/"]);
+    assert_eq!(config.level(), DiagramLevel::Type);
+    assert_eq!(
+        config.module_mappings().get("src/orders").unwrap(),
+        "Orders"
+    );
+}
+
+#[test]
+fn loads_output_config_from_toml_file() {
+    let dir = tempfile::tempdir().unwrap();
+    let config_path = dir.path().join("archlens.toml");
+    fs::write(
+        &config_path,
+        r#"
+[output]
+format = "mermaid"
+path = "docs/arch.mmd"
+split_by_module = true
+"#,
+    )
+    .unwrap();
+
+    let loader = TomlConfigLoader::from_path(&config_path).unwrap();
+    let config = loader.load_output_config().unwrap();
+
+    assert!(config.split_by_module());
+    assert_eq!(config.output_path(), Some("docs/arch.mmd"));
+}
+
+#[test]
+fn missing_file_returns_defaults() {
+    let loader = TomlConfigLoader::default();
+
+    let analysis = loader.load_analysis_config().unwrap();
+    assert!(analysis.excludes().is_empty());
+    assert_eq!(analysis.level(), DiagramLevel::Module);
+
+    let output = loader.load_output_config().unwrap();
+    assert!(!output.split_by_module());
+    assert!(output.output_path().is_none());
+}

crates/adapters/tree-sitter/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "archlens-tree-sitter"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+tree-sitter.workspace = true
+tree-sitter-rust.workspace = true
+tree-sitter-python.workspace = true
+tree-sitter-c-sharp.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/adapters/tree-sitter/src/lib.rs

@@ -0,0 +1,5 @@
+mod python;
+mod rust;
+mod tree_sitter_analyzer;
+
+pub use tree_sitter_analyzer::TreeSitterAnalyzer;

crates/adapters/tree-sitter/src/python/mod.rs

@@ -0,0 +1,337 @@
+use std::collections::HashSet;
+
+use tree_sitter::{Node, Parser};
+
+use archlens_domain::{
+    AnalysisResult, AnalysisWarning, CodeElement, CodeElementKind, DomainError, FilePath,
+    Relationship, RelationshipKind,
+};
+
+pub fn analyze(source: &str, file_path: &FilePath) -> Result<AnalysisResult, DomainError> {
+    let mut parser = Parser::new();
+    parser
+        .set_language(&tree_sitter_python::LANGUAGE.into())
+        .map_err(|e| DomainError::AnalysisError(e.to_string()))?;
+
+    let tree = parser
+        .parse(source, None)
+        .ok_or_else(|| DomainError::AnalysisError("failed to parse".to_string()))?;
+
+    let mut elements = Vec::new();
+    let mut relationships = Vec::new();
+    let mut warnings = Vec::new();
+    let mut type_names: HashSet<String> = HashSet::new();
+
+    let root = tree.root_node();
+    collect_classes(
+        &root,
+        source,
+        file_path,
+        &mut elements,
+        &mut type_names,
+        &mut relationships,
+        &mut warnings,
+    );
+    collect_imports(&root, source, file_path, &mut relationships);
+
+    let relationships = relationships
+        .into_iter()
+        .map(|r| r.with_source_file(file_path.clone()))
+        .collect();
+
+    Ok(AnalysisResult::new(elements, relationships, warnings))
+}
+
+fn collect_classes(
+    node: &Node,
+    source: &str,
+    file_path: &FilePath,
+    elements: &mut Vec<CodeElement>,
+    type_names: &mut HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+    warnings: &mut Vec<AnalysisWarning>,
+) {
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        if child.kind() != "class_definition" {
+            continue;
+        }
+
+        let Some(name_node) = child.child_by_field_name("name") else {
+            continue;
+        };
+
+        let name = &source[name_node.byte_range()];
+        let line = child.start_position().row + 1;
+
+        match CodeElement::new(name, CodeElementKind::Class, file_path.clone(), line) {
+            Ok(element) => {
+                type_names.insert(name.to_string());
+                elements.push(element);
+            }
+            Err(e) => {
+                if let Ok(w) = AnalysisWarning::new(file_path.clone(), line, &e.to_string()) {
+                    warnings.push(w);
+                }
+                continue;
+            }
+        }
+
+        if let Some(superclasses) = child.child_by_field_name("superclasses") {
+            collect_inheritance(&superclasses, source, name, type_names, relationships);
+        }
+
+        if let Some(body) = child.child_by_field_name("body") {
+            collect_typed_fields(&body, source, name, type_names, relationships);
+            collect_constructor_params(&body, source, name, type_names, relationships);
+        }
+    }
+}
+
+fn collect_inheritance(
+    superclasses: &Node,
+    source: &str,
+    class_name: &str,
+    _type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+) {
+    let mut cursor = superclasses.walk();
+    for child in superclasses.children(&mut cursor) {
+        if child.kind() == "identifier" {
+            let base_name = &source[child.byte_range()];
+            if !is_python_builtin(base_name)
+                && let Ok(rel) =
+                    Relationship::new(class_name, base_name, RelationshipKind::Inheritance)
+            {
+                relationships.push(rel);
+            }
+        }
+    }
+}
+
+const PYTHON_BUILTINS: &[&str] = &[
+    "str",
+    "int",
+    "float",
+    "bool",
+    "bytes",
+    "list",
+    "dict",
+    "set",
+    "tuple",
+    "None",
+    "type",
+    "object",
+    "Exception",
+    "BaseException",
+    "Optional",
+    "Any",
+    "Union",
+    "List",
+    "Dict",
+    "Set",
+    "Tuple",
+    "Callable",
+    "Sequence",
+    "Mapping",
+    "Iterable",
+    "Iterator",
+    "Generator",
+    "Coroutine",
+    "AsyncGenerator",
+    "ClassVar",
+    "Final",
+    "Literal",
+    "TypeVar",
+    "Generic",
+    "Protocol",
+    "runtime_checkable",
+    "Self",
+];
+
+fn is_python_builtin(name: &str) -> bool {
+    PYTHON_BUILTINS.contains(&name)
+}
+
+const STDLIB_MODULES: &[&str] = &[
+    "os",
+    "sys",
+    "typing",
+    "logging",
+    "json",
+    "re",
+    "io",
+    "abc",
+    "collections",
+    "datetime",
+    "enum",
+    "functools",
+    "hashlib",
+    "http",
+    "importlib",
+    "inspect",
+    "itertools",
+    "math",
+    "pathlib",
+    "pickle",
+    "random",
+    "shutil",
+    "signal",
+    "socket",
+    "string",
+    "subprocess",
+    "tempfile",
+    "threading",
+    "time",
+    "traceback",
+    "unittest",
+    "urllib",
+    "uuid",
+    "warnings",
+    "contextlib",
+    "dataclasses",
+    "copy",
+    "struct",
+    "base64",
+    "csv",
+    "glob",
+    "operator",
+    "textwrap",
+    "asyncio",
+    "concurrent",
+    "multiprocessing",
+];
+
+fn is_external_import(module: &str) -> bool {
+    let top = module.split('.').next().unwrap_or(module);
+    if STDLIB_MODULES.contains(&top) {
+        return true;
+    }
+    if top.starts_with('_') {
+        return true;
+    }
+    false
+}
+
+fn collect_imports(
+    node: &Node,
+    source: &str,
+    file_path: &FilePath,
+    relationships: &mut Vec<Relationship>,
+) {
+    let file_name = std::path::Path::new(file_path.as_str())
+        .file_stem()
+        .and_then(|s| s.to_str())
+        .unwrap_or("unknown");
+
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        match child.kind() {
+            "import_statement" => {
+                let mut name_cursor = child.walk();
+                for name_child in child.children(&mut name_cursor) {
+                    if name_child.kind() == "dotted_name" {
+                        let module = &source[name_child.byte_range()];
+                        if !is_external_import(module)
+                            && let Ok(rel) =
+                                Relationship::new(file_name, module, RelationshipKind::Import)
+                        {
+                            relationships.push(rel);
+                        }
+                    }
+                }
+            }
+            "import_from_statement" => {
+                if let Some(module_node) = child.child_by_field_name("module_name") {
+                    let module = &source[module_node.byte_range()];
+                    if !is_external_import(module)
+                        && let Ok(rel) =
+                            Relationship::new(file_name, module, RelationshipKind::Import)
+                    {
+                        relationships.push(rel);
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+}
+
+fn collect_constructor_params(
+    body: &Node,
+    source: &str,
+    class_name: &str,
+    _type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+) {
+    let mut cursor = body.walk();
+    for child in body.children(&mut cursor) {
+        if child.kind() != "function_definition" {
+            continue;
+        }
+        let Some(fn_name) = child.child_by_field_name("name") else {
+            continue;
+        };
+        if &source[fn_name.byte_range()] != "__init__" {
+            continue;
+        }
+        let Some(params) = child.child_by_field_name("parameters") else {
+            continue;
+        };
+        let mut param_cursor = params.walk();
+        for param in params.children(&mut param_cursor) {
+            if param.kind() == "typed_parameter"
+                && let Some(type_node) = param.child_by_field_name("type")
+            {
+                let type_text = &source[type_node.byte_range()];
+                let base_type = type_text.split('[').next().unwrap_or(type_text).trim();
+                if base_type != class_name
+                    && !base_type.is_empty()
+                    && !is_python_builtin(base_type)
+                    && let Ok(rel) =
+                        Relationship::new(class_name, base_type, RelationshipKind::Composition)
+                {
+                    relationships.push(rel);
+                }
+            }
+        }
+    }
+}
+
+fn collect_typed_fields(
+    body: &Node,
+    source: &str,
+    class_name: &str,
+    type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+) {
+    collect_typed_fields_recursive(body, source, class_name, type_names, relationships);
+}
+
+fn collect_typed_fields_recursive(
+    node: &Node,
+    source: &str,
+    class_name: &str,
+    _type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+) {
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        if (child.kind() == "assignment" || child.kind() == "typed_assignment")
+            && let Some(type_node) = child.child_by_field_name("type")
+        {
+            let type_text = &source[type_node.byte_range()];
+            let base_type = type_text.split('[').next().unwrap_or(type_text).trim();
+            if base_type != class_name
+                && !base_type.is_empty()
+                && !is_python_builtin(base_type)
+                && let Ok(rel) =
+                    Relationship::new(class_name, base_type, RelationshipKind::Composition)
+            {
+                relationships.push(rel);
+            }
+        }
+
+        collect_typed_fields_recursive(&child, source, class_name, _type_names, relationships);
+    }
+}

crates/adapters/tree-sitter/src/rust/mod.rs

@@ -0,0 +1,349 @@
+use std::collections::HashSet;
+
+use tree_sitter::{Node, Parser};
+
+const RUST_PRIMITIVES: &[&str] = &[
+    "bool",
+    "char",
+    "str",
+    "String",
+    "u8",
+    "u16",
+    "u32",
+    "u64",
+    "u128",
+    "usize",
+    "i8",
+    "i16",
+    "i32",
+    "i64",
+    "i128",
+    "isize",
+    "f32",
+    "f64",
+    "Vec",
+    "Option",
+    "Result",
+    "Box",
+    "Rc",
+    "Arc",
+    "HashMap",
+    "HashSet",
+    "BTreeMap",
+    "BTreeSet",
+    "PhantomData",
+    "Pin",
+    "Cow",
+    "Self",
+];
+
+use archlens_domain::{
+    AnalysisResult, AnalysisWarning, CodeElement, CodeElementKind, DomainError, FilePath,
+    Relationship, RelationshipKind, Visibility,
+};
+
+pub fn analyze(source: &str, file_path: &FilePath) -> Result<AnalysisResult, DomainError> {
+    let mut parser = Parser::new();
+    parser
+        .set_language(&tree_sitter_rust::LANGUAGE.into())
+        .map_err(|e| DomainError::AnalysisError(e.to_string()))?;
+
+    let tree = parser
+        .parse(source, None)
+        .ok_or_else(|| DomainError::AnalysisError("failed to parse".to_string()))?;
+
+    let mut elements = Vec::new();
+    let mut relationships = Vec::new();
+    let mut warnings = Vec::new();
+    let mut type_names: HashSet<String> = HashSet::new();
+
+    let root = tree.root_node();
+    collect_types(
+        &root,
+        source,
+        file_path,
+        &mut elements,
+        &mut type_names,
+        &mut warnings,
+    );
+    collect_relationships(
+        &root,
+        source,
+        &type_names,
+        &mut relationships,
+        &mut warnings,
+    );
+    collect_mod_declarations(&root, source, file_path, &mut relationships);
+    collect_use_imports(&root, source, file_path, &mut relationships);
+
+    let relationships = relationships
+        .into_iter()
+        .map(|r| r.with_source_file(file_path.clone()))
+        .collect();
+
+    Ok(AnalysisResult::new(elements, relationships, warnings))
+}
+
+fn collect_types(
+    node: &Node,
+    source: &str,
+    file_path: &FilePath,
+    elements: &mut Vec<CodeElement>,
+    type_names: &mut HashSet<String>,
+    warnings: &mut Vec<AnalysisWarning>,
+) {
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        let (kind, name_field) = match child.kind() {
+            "struct_item" => (CodeElementKind::Struct, "name"),
+            "enum_item" => (CodeElementKind::Enum, "name"),
+            "trait_item" => (CodeElementKind::Trait, "name"),
+            _ => continue,
+        };
+
+        if let Some(name_node) = child.child_by_field_name(name_field) {
+            let name = &source[name_node.byte_range()];
+            let line = child.start_position().row + 1;
+            let visibility = detect_visibility(&child, source);
+
+            match CodeElement::new(name, kind, file_path.clone(), line) {
+                Ok(element) => {
+                    let fields = extract_fields(&child, source);
+                    let methods = extract_methods(node, source, name);
+                    let element = element
+                        .with_visibility(visibility)
+                        .with_fields(fields)
+                        .with_methods(methods);
+                    type_names.insert(name.to_string());
+                    elements.push(element);
+                }
+                Err(e) => {
+                    if let Ok(w) = AnalysisWarning::new(file_path.clone(), line, &e.to_string()) {
+                        warnings.push(w);
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn collect_relationships(
+    node: &Node,
+    source: &str,
+    type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+    warnings: &mut Vec<AnalysisWarning>,
+) {
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        match child.kind() {
+            "struct_item" => {
+                if let Some(name_node) = child.child_by_field_name("name") {
+                    let struct_name = source[name_node.byte_range()].to_string();
+                    collect_field_compositions(
+                        &child,
+                        source,
+                        &struct_name,
+                        type_names,
+                        relationships,
+                    );
+                }
+            }
+            "impl_item" => {
+                collect_trait_impl(&child, source, type_names, relationships, warnings);
+            }
+            _ => {}
+        }
+    }
+}
+
+fn collect_field_compositions(
+    struct_node: &Node,
+    source: &str,
+    struct_name: &str,
+    _type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+) {
+    if let Some(body) = struct_node.child_by_field_name("body") {
+        let mut cursor = body.walk();
+        for field in body.children(&mut cursor) {
+            if field.kind() == "field_declaration"
+                && let Some(type_node) = field.child_by_field_name("type")
+            {
+                let type_text = extract_base_type(&type_node, source);
+                if type_text != struct_name
+                    && !type_text.is_empty()
+                    && !RUST_PRIMITIVES.contains(&type_text.as_str())
+                    && let Ok(rel) =
+                        Relationship::new(struct_name, &type_text, RelationshipKind::Composition)
+                {
+                    relationships.push(rel);
+                }
+            }
+        }
+    }
+}
+
+fn collect_trait_impl(
+    impl_node: &Node,
+    source: &str,
+    _type_names: &HashSet<String>,
+    relationships: &mut Vec<Relationship>,
+    _warnings: &mut Vec<AnalysisWarning>,
+) {
+    let trait_node = impl_node.child_by_field_name("trait");
+    let type_node = impl_node.child_by_field_name("type");
+
+    if let (Some(trait_n), Some(type_n)) = (trait_node, type_node) {
+        let trait_name = extract_base_type(&trait_n, source);
+        let type_name = extract_base_type(&type_n, source);
+
+        if !trait_name.is_empty()
+            && !type_name.is_empty()
+            && !RUST_PRIMITIVES.contains(&trait_name.as_str())
+            && !RUST_PRIMITIVES.contains(&type_name.as_str())
+            && let Ok(rel) =
+                Relationship::new(&type_name, &trait_name, RelationshipKind::Inheritance)
+        {
+            relationships.push(rel);
+        }
+    }
+}
+
+fn extract_fields(node: &Node, source: &str) -> Vec<String> {
+    let mut fields = Vec::new();
+    if let Some(body) = node.child_by_field_name("body") {
+        let mut cursor = body.walk();
+        for child in body.children(&mut cursor) {
+            if child.kind() == "field_declaration" {
+                let name = child
+                    .child_by_field_name("name")
+                    .map(|n| &source[n.byte_range()]);
+                let ty = child
+                    .child_by_field_name("type")
+                    .map(|n| extract_base_type(&n, source));
+                if let (Some(name), Some(ty)) = (name, ty) {
+                    fields.push(format!("{name}: {ty}"));
+                }
+            }
+        }
+    }
+    fields
+}
+
+fn extract_methods(root: &Node, source: &str, type_name: &str) -> Vec<String> {
+    let mut methods = Vec::new();
+    let mut cursor = root.walk();
+    for child in root.children(&mut cursor) {
+        if child.kind() != "impl_item" {
+            continue;
+        }
+        if child.child_by_field_name("trait").is_some() {
+            continue;
+        }
+        let type_node = child.child_by_field_name("type");
+        if let Some(tn) = type_node {
+            let impl_name = extract_base_type(&tn, source);
+            if impl_name != type_name {
+                continue;
+            }
+        }
+        if let Some(body) = child.child_by_field_name("body") {
+            let mut body_cursor = body.walk();
+            for item in body.children(&mut body_cursor) {
+                if item.kind() == "function_item"
+                    && let Some(name_node) = item.child_by_field_name("name")
+                {
+                    let fn_name = &source[name_node.byte_range()];
+                    let vis = if detect_visibility(&item, source) == Visibility::Public {
+                        "+"
+                    } else {
+                        "-"
+                    };
+                    methods.push(format!("{vis}{fn_name}()"));
+                }
+            }
+        }
+    }
+    methods
+}
+
+fn collect_mod_declarations(
+    node: &Node,
+    source: &str,
+    file_path: &FilePath,
+    relationships: &mut Vec<Relationship>,
+) {
+    let file_name = std::path::Path::new(file_path.as_str())
+        .file_stem()
+        .and_then(|s| s.to_str())
+        .unwrap_or("unknown");
+
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        if child.kind() != "mod_item" {
+            continue;
+        }
+        if child.child_by_field_name("body").is_some() {
+            continue;
+        }
+        if let Some(name_node) = child.child_by_field_name("name") {
+            let mod_name = &source[name_node.byte_range()];
+            let target = format!("crate::{mod_name}");
+            if let Ok(rel) = Relationship::new(file_name, &target, RelationshipKind::Import) {
+                relationships.push(rel);
+            }
+        }
+    }
+}
+
+fn collect_use_imports(
+    node: &Node,
+    source: &str,
+    file_path: &FilePath,
+    relationships: &mut Vec<Relationship>,
+) {
+    let file_name = std::path::Path::new(file_path.as_str())
+        .file_stem()
+        .and_then(|s| s.to_str())
+        .unwrap_or("unknown");
+
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        if child.kind() != "use_declaration" {
+            continue;
+        }
+        if let Some(arg) = child.child_by_field_name("argument") {
+            let text = &source[arg.byte_range()];
+            let path = text
+                .split('{')
+                .next()
+                .unwrap_or(text)
+                .trim_end_matches("::");
+
+            if (path.starts_with("crate::") || path.starts_with("super::"))
+                && let Ok(rel) = Relationship::new(file_name, path, RelationshipKind::Import)
+            {
+                relationships.push(rel);
+            }
+        }
+    }
+}
+
+fn extract_base_type(node: &Node, source: &str) -> String {
+    let text = &source[node.byte_range()];
+    text.split('<').next().unwrap_or(text).trim().to_string()
+}
+
+fn detect_visibility(node: &Node, source: &str) -> Visibility {
+    let mut cursor = node.walk();
+    for child in node.children(&mut cursor) {
+        if child.kind() == "visibility_modifier" {
+            let text = &source[child.byte_range()];
+            if text.contains("pub") {
+                return Visibility::Public;
+            }
+        }
+    }
+    Visibility::Private
+}

crates/adapters/tree-sitter/src/tree_sitter_analyzer.rs

@@ -0,0 +1,30 @@
+use archlens_domain::{AnalysisResult, DomainError, Language, SourceFile, ports::SourceAnalyzer};
+
+use crate::{python, rust};
+
+pub struct TreeSitterAnalyzer;
+
+impl Default for TreeSitterAnalyzer {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl TreeSitterAnalyzer {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl SourceAnalyzer for TreeSitterAnalyzer {
+    fn analyze_file(&self, file: &SourceFile) -> Result<AnalysisResult, DomainError> {
+        let source = std::fs::read_to_string(file.path().as_str())
+            .map_err(|e| DomainError::IoError(e.to_string()))?;
+
+        match file.language() {
+            Language::Rust => rust::analyze(&source, file.path()),
+            Language::Python => python::analyze(&source, file.path()),
+            Language::CSharp => Ok(AnalysisResult::empty()),
+        }
+    }
+}

crates/adapters/tree-sitter/tests/python_analyzer_tests.rs

@@ -0,0 +1,138 @@
+use archlens_domain::{
+    CodeElementKind, FilePath, Language, RelationshipKind, SourceFile, ports::SourceAnalyzer,
+};
+use archlens_tree_sitter::TreeSitterAnalyzer;
+
+fn analyze_python(source: &str, filename: &str) -> archlens_domain::AnalysisResult {
+    let dir = tempfile::tempdir().unwrap();
+    let file_path = dir.path().join(filename);
+    std::fs::write(&file_path, source).unwrap();
+
+    let analyzer = TreeSitterAnalyzer::new();
+    let source_file = SourceFile::new(
+        FilePath::new(file_path.to_str().unwrap()).unwrap(),
+        Language::Python,
+    );
+    analyzer.analyze_file(&source_file).unwrap()
+}
+
+#[test]
+fn extracts_python_class() {
+    let result = analyze_python("class Order:\n    pass\n", "order.py");
+
+    assert_eq!(result.elements().len(), 1);
+    assert_eq!(result.elements()[0].name(), "Order");
+    assert_eq!(result.elements()[0].kind(), CodeElementKind::Class);
+}
+
+#[test]
+fn extracts_python_inheritance() {
+    let source = "class Animal:\n    pass\n\nclass Dog(Animal):\n    pass\n";
+    let result = analyze_python(source, "animals.py");
+
+    assert_eq!(result.elements().len(), 2);
+
+    let inheritance: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Inheritance)
+        .collect();
+
+    assert_eq!(inheritance.len(), 1);
+    assert_eq!(inheritance[0].source(), "Dog");
+    assert_eq!(inheritance[0].target(), "Animal");
+}
+
+#[test]
+fn extracts_composition_from_type_annotated_fields() {
+    let source = "class Address:\n    pass\n\nclass User:\n    def __init__(self):\n        self.address: Address = Address()\n";
+    let result = analyze_python(source, "user.py");
+
+    let composition: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Composition)
+        .collect();
+
+    assert_eq!(composition.len(), 1);
+    assert_eq!(composition[0].source(), "User");
+    assert_eq!(composition[0].target(), "Address");
+}
+
+#[test]
+fn extracts_import_from_import_statement() {
+    let source = "import os\nfrom commons.src.schema import BaseModel\n";
+    let result = analyze_python(source, "service.py");
+
+    let imports: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Import)
+        .collect();
+
+    assert!(imports.iter().any(|r| r.target() == "commons.src.schema"));
+    assert!(
+        !imports.iter().any(|r| r.target() == "os"),
+        "stdlib should be filtered"
+    );
+}
+
+#[test]
+fn extracts_relative_imports_from_init() {
+    let source = "from .schema import BaseModel\nfrom .client import ApiClient\n";
+    let result = analyze_python(source, "__init__.py");
+
+    let imports: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Import)
+        .collect();
+
+    assert_eq!(imports.len(), 2);
+}
+
+#[test]
+fn extracts_import_from_plain_import() {
+    let source = "import commons.utils\n";
+    let result = analyze_python(source, "service.py");
+
+    let imports: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Import)
+        .collect();
+
+    assert!(imports.iter().any(|r| r.target() == "commons.utils"));
+}
+
+#[test]
+fn extracts_composition_from_constructor_params() {
+    let source = "class Config:\n    pass\n\nclass Service:\n    def __init__(self, config: Config):\n        pass\n";
+    let result = analyze_python(source, "service.py");
+
+    let composition: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Composition)
+        .collect();
+
+    assert_eq!(composition.len(), 1);
+    assert_eq!(composition[0].source(), "Service");
+    assert_eq!(composition[0].target(), "Config");
+}
+
+#[test]
+fn extracts_composition_from_class_level_annotations() {
+    let source = "class Gad:\n    pass\n\nclass Definition:\n    gad: Gad\n    name: str\n";
+    let result = analyze_python(source, "models.py");
+
+    let composition: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Composition)
+        .collect();
+
+    assert_eq!(composition.len(), 1);
+    assert_eq!(composition[0].source(), "Definition");
+    assert_eq!(composition[0].target(), "Gad");
+}

crates/adapters/tree-sitter/tests/rust_analyzer_tests.rs

@@ -0,0 +1,130 @@
+use archlens_domain::{
+    CodeElementKind, FilePath, Language, RelationshipKind, SourceFile, ports::SourceAnalyzer,
+};
+use archlens_tree_sitter::TreeSitterAnalyzer;
+
+fn analyze_rust(source: &str, filename: &str) -> archlens_domain::AnalysisResult {
+    let dir = tempfile::tempdir().unwrap();
+    let file_path = dir.path().join(filename);
+    std::fs::write(&file_path, source).unwrap();
+
+    let analyzer = TreeSitterAnalyzer::new();
+    let source_file = SourceFile::new(
+        FilePath::new(file_path.to_str().unwrap()).unwrap(),
+        Language::Rust,
+    );
+    analyzer.analyze_file(&source_file).unwrap()
+}
+
+#[test]
+fn extracts_rust_struct() {
+    let result = analyze_rust("pub struct Order {\n    id: u64,\n}", "order.rs");
+
+    assert_eq!(result.elements().len(), 1);
+    assert_eq!(result.elements()[0].name(), "Order");
+    assert_eq!(result.elements()[0].kind(), CodeElementKind::Struct);
+}
+
+#[test]
+fn extracts_rust_enum() {
+    let result = analyze_rust(
+        "pub enum Status {\n    Active,\n    Inactive,\n}",
+        "status.rs",
+    );
+
+    assert_eq!(result.elements().len(), 1);
+    assert_eq!(result.elements()[0].name(), "Status");
+    assert_eq!(result.elements()[0].kind(), CodeElementKind::Enum);
+}
+
+#[test]
+fn extracts_rust_trait() {
+    let result = analyze_rust("pub trait Repository {\n    fn find(&self);\n}", "repo.rs");
+
+    assert_eq!(result.elements().len(), 1);
+    assert_eq!(result.elements()[0].name(), "Repository");
+    assert_eq!(result.elements()[0].kind(), CodeElementKind::Trait);
+}
+
+#[test]
+fn extracts_composition_from_struct_fields() {
+    let source =
+        "pub struct Order {\n    id: u64,\n}\npub struct OrderService {\n    order: Order,\n}";
+    let result = analyze_rust(source, "service.rs");
+
+    assert_eq!(result.elements().len(), 2);
+    assert_eq!(result.relationships().len(), 1);
+    assert_eq!(result.relationships()[0].source(), "OrderService");
+    assert_eq!(result.relationships()[0].target(), "Order");
+    assert_eq!(
+        result.relationships()[0].kind(),
+        RelationshipKind::Composition
+    );
+}
+
+#[test]
+fn extracts_inheritance_from_trait_impl() {
+    let source = "pub trait Printable {}\npub struct Order {}\nimpl Printable for Order {}";
+    let result = analyze_rust(source, "order.rs");
+
+    let inheritance: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Inheritance)
+        .collect();
+
+    assert_eq!(inheritance.len(), 1);
+    assert_eq!(inheritance[0].source(), "Order");
+    assert_eq!(inheritance[0].target(), "Printable");
+}
+
+#[test]
+fn extracts_use_imports() {
+    let source =
+        "use crate::domain::Order;\nuse crate::ports::Repository;\n\npub struct Service {}";
+    let result = analyze_rust(source, "service.rs");
+
+    let imports: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Import)
+        .collect();
+
+    assert!(imports.iter().any(|r| r.target() == "crate::domain::Order"));
+    assert!(
+        imports
+            .iter()
+            .any(|r| r.target() == "crate::ports::Repository")
+    );
+}
+
+#[test]
+fn filters_std_and_external_crate_imports() {
+    let source =
+        "use std::collections::HashMap;\nuse serde::Serialize;\nuse crate::models::Order;\n";
+    let result = analyze_rust(source, "lib.rs");
+
+    let imports: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Import)
+        .collect();
+
+    assert_eq!(imports.len(), 1);
+    assert_eq!(imports[0].target(), "crate::models::Order");
+}
+
+#[test]
+fn extracts_mod_declarations() {
+    let source = "mod models;\nmod services;\npub struct App {}";
+    let result = analyze_rust(source, "lib.rs");
+
+    let imports: Vec<_> = result
+        .relationships()
+        .iter()
+        .filter(|r| r.kind() == RelationshipKind::Import)
+        .collect();
+
+    assert!(imports.iter().any(|r| r.target() == "crate::models"));
+    assert!(imports.iter().any(|r| r.target() == "crate::services"));
+}

crates/adapters/walkdir/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "archlens-walkdir"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+walkdir.workspace = true
+ignore.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

crates/adapters/walkdir/src/lib.rs

@@ -0,0 +1,3 @@
+mod walkdir_discovery;
+
+pub use walkdir_discovery::WalkdirDiscovery;

crates/adapters/walkdir/src/walkdir_discovery.rs

@@ -0,0 +1,100 @@
+use std::path::Path;
+
+use ignore::WalkBuilder;
+
+use archlens_domain::{
+    AnalysisConfig, DomainError, FilePath, Language, SourceFile, ports::FileDiscovery,
+};
+
+const DEFAULT_EXCLUDES: &[&str] = &[
+    ".venv",
+    "venv",
+    "node_modules",
+    "__pycache__",
+    ".git",
+    "target",
+    "bin",
+    "obj",
+    "dist",
+    ".tox",
+    ".eggs",
+];
+
+pub struct WalkdirDiscovery;
+
+impl Default for WalkdirDiscovery {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl WalkdirDiscovery {
+    pub fn new() -> Self {
+        Self
+    }
+
+    fn detect_language(path: &Path) -> Option<Language> {
+        match path.extension()?.to_str()? {
+            "rs" => Some(Language::Rust),
+            "py" => Some(Language::Python),
+            "cs" => Some(Language::CSharp),
+            _ => None,
+        }
+    }
+
+    fn is_excluded(path: &Path, root: &Path, excludes: &[String]) -> bool {
+        let relative = path.strip_prefix(root).unwrap_or(path);
+        let relative_str = relative.to_string_lossy();
+
+        for component in relative.components() {
+            let name = component.as_os_str().to_string_lossy();
+            if DEFAULT_EXCLUDES.iter().any(|e| name == *e) {
+                return true;
+            }
+        }
+
+        excludes
+            .iter()
+            .any(|exclude| relative_str.contains(exclude.trim_end_matches('/')))
+    }
+}
+
+impl FileDiscovery for WalkdirDiscovery {
+    fn discover(
+        &self,
+        root: &Path,
+        config: &AnalysisConfig,
+    ) -> Result<Vec<SourceFile>, DomainError> {
+        let mut files = Vec::new();
+
+        let walker = WalkBuilder::new(root).hidden(true).git_ignore(true).build();
+
+        for entry in walker.filter_map(|e| e.ok()) {
+            let path = entry.path();
+
+            if !path.is_file() {
+                continue;
+            }
+
+            if Self::is_excluded(path, root, config.excludes()) {
+                continue;
+            }
+
+            if let Some(scope) = config.scope() {
+                let relative = path.strip_prefix(root).unwrap_or(path);
+                if !relative.starts_with(scope) {
+                    continue;
+                }
+            }
+
+            if let Some(language) = Self::detect_language(path) {
+                let absolute = path.canonicalize().unwrap_or_else(|_| path.to_path_buf());
+                let file_path = FilePath::new(&absolute.to_string_lossy())
+                    .map_err(|e| DomainError::IoError(e.to_string()))?;
+                files.push(SourceFile::new(file_path, language));
+            }
+        }
+
+        Ok(files)
+    }
+}

crates/adapters/walkdir/tests/walkdir_discovery_tests.rs

@@ -0,0 +1,71 @@
+use std::fs;
+
+use archlens_domain::{AnalysisConfig, Language, ports::FileDiscovery};
+use archlens_walkdir::WalkdirDiscovery;
+
+fn create_test_tree(dir: &std::path::Path) {
+    fs::create_dir_all(dir.join("src/orders")).unwrap();
+    fs::create_dir_all(dir.join("src/billing")).unwrap();
+    fs::write(dir.join("src/orders/service.rs"), "struct OrderService;").unwrap();
+    fs::write(dir.join("src/orders/model.py"), "class Order: pass").unwrap();
+    fs::write(dir.join("src/billing/invoice.cs"), "class Invoice {}").unwrap();
+    fs::write(dir.join("src/readme.txt"), "not source code").unwrap();
+}
+
+#[test]
+fn discovers_rust_python_and_csharp_files() {
+    let dir = tempfile::tempdir().unwrap();
+    create_test_tree(dir.path());
+
+    let discovery = WalkdirDiscovery::new();
+    let files = discovery
+        .discover(dir.path(), &AnalysisConfig::default())
+        .unwrap();
+
+    assert_eq!(files.len(), 3);
+
+    let languages: Vec<Language> = files.iter().map(|f| f.language()).collect();
+    assert!(languages.contains(&Language::Rust));
+    assert!(languages.contains(&Language::Python));
+    assert!(languages.contains(&Language::CSharp));
+}
+
+#[test]
+fn ignores_non_source_files() {
+    let dir = tempfile::tempdir().unwrap();
+    create_test_tree(dir.path());
+
+    let discovery = WalkdirDiscovery::new();
+    let files = discovery
+        .discover(dir.path(), &AnalysisConfig::default())
+        .unwrap();
+
+    let paths: Vec<&str> = files.iter().map(|f| f.path().as_str()).collect();
+    assert!(!paths.iter().any(|p| p.ends_with(".txt")));
+}
+
+#[test]
+fn respects_exclude_patterns() {
+    let dir = tempfile::tempdir().unwrap();
+    create_test_tree(dir.path());
+
+    let config = AnalysisConfig::default().with_excludes(vec!["billing".to_string()]);
+
+    let discovery = WalkdirDiscovery::new();
+    let files = discovery.discover(dir.path(), &config).unwrap();
+
+    assert_eq!(files.len(), 2);
+    assert!(!files.iter().any(|f| f.path().as_str().contains("billing")));
+}
+
+#[test]
+fn empty_directory_returns_no_files() {
+    let dir = tempfile::tempdir().unwrap();
+
+    let discovery = WalkdirDiscovery::new();
+    let files = discovery
+        .discover(dir.path(), &AnalysisConfig::default())
+        .unwrap();
+
+    assert!(files.is_empty());
+}

crates/application/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "archlens-application"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+archlens-domain.workspace = true
+thiserror.workspace = true
+tracing.workspace = true
+rayon.workspace = true

crates/application/src/lib.rs

@@ -0,0 +1 @@
+pub mod queries;

crates/application/src/queries/analyze_codebase.rs

@@ -0,0 +1,244 @@
+use std::collections::HashSet;
+use std::path::Path;
+
+use rayon::prelude::*;
+
+use archlens_domain::{
+    AnalysisConfig, AnalysisWarning, CodeElement, CodeGraph, DomainError, ModuleName, Relationship,
+    RelationshipKind,
+    ports::{FileDiscovery, SourceAnalyzer},
+};
+
+pub struct AnalyzeCodebase<F, S>
+where
+    F: FileDiscovery + Send + Sync,
+    S: SourceAnalyzer,
+{
+    file_discovery: F,
+    source_analyzer: S,
+}
+
+impl<F, S> AnalyzeCodebase<F, S>
+where
+    F: FileDiscovery + Send + Sync,
+    S: SourceAnalyzer,
+{
+    pub fn new(file_discovery: F, source_analyzer: S) -> Self {
+        Self {
+            file_discovery,
+            source_analyzer,
+        }
+    }
+
+    pub fn execute(
+        &self,
+        root: &Path,
+        config: &AnalysisConfig,
+    ) -> Result<AnalyzeCodebaseResult, DomainError> {
+        let files = self.file_discovery.discover(root, config)?;
+
+        let file_results: Vec<(Vec<CodeElement>, Vec<Relationship>, Vec<AnalysisWarning>)> = files
+            .par_iter()
+            .map(|file| match self.source_analyzer.analyze_file(file) {
+                Ok(result) => {
+                    let module = infer_module(file.path().as_str(), root, config);
+                    let elements: Vec<CodeElement> = result
+                        .elements()
+                        .iter()
+                        .map(|el| {
+                            let mut el = el.clone();
+                            if el.module().is_none()
+                                && let Some(ref m) = module
+                            {
+                                el = el.with_module(m.clone());
+                            }
+                            el
+                        })
+                        .collect();
+                    (
+                        elements,
+                        result.relationships().to_vec(),
+                        result.warnings().to_vec(),
+                    )
+                }
+                Err(err) => {
+                    let mut warnings = Vec::new();
+                    if let Ok(warning) =
+                        AnalysisWarning::new(file.path().clone(), 0, &err.to_string())
+                    {
+                        warnings.push(warning);
+                    }
+                    (Vec::new(), Vec::new(), warnings)
+                }
+            })
+            .collect();
+
+        let mut graph = CodeGraph::new();
+        let mut warnings = Vec::new();
+        for (elements, relationships, warns) in file_results {
+            for el in elements {
+                graph.add_element(el);
+            }
+            for rel in relationships {
+                graph.add_relationship(rel);
+            }
+            warnings.extend(warns);
+        }
+
+        let graph = resolve_cross_file_relationships(graph);
+        let graph = filter_external_imports(graph, root);
+
+        Ok(AnalyzeCodebaseResult { graph, warnings })
+    }
+}
+
+fn resolve_cross_file_relationships(graph: CodeGraph) -> CodeGraph {
+    use std::collections::HashMap;
+
+    let mut file_types: HashMap<String, HashSet<String>> = HashMap::new();
+    let mut name_modules: HashMap<&str, HashSet<Option<&str>>> = HashMap::new();
+    let all_type_names: HashSet<&str> = graph.elements().iter().map(|e| e.name()).collect();
+
+    for element in graph.elements() {
+        file_types
+            .entry(element.file_path().as_str().to_string())
+            .or_default()
+            .insert(element.name().to_string());
+        name_modules
+            .entry(element.name())
+            .or_default()
+            .insert(element.module().map(|m| m.as_str()));
+    }
+
+    let mut resolved = CodeGraph::new();
+    for element in graph.elements() {
+        resolved.add_element(element.clone());
+    }
+    for rel in graph.relationships() {
+        match rel.kind() {
+            RelationshipKind::Import => {
+                resolved.add_relationship(rel.clone());
+            }
+            _ => {
+                if !all_type_names.contains(rel.source()) || !all_type_names.contains(rel.target())
+                {
+                    continue;
+                }
+
+                if let Some(src_file) = rel.source_file() {
+                    let file_key = src_file.as_str().to_string();
+                    if let Some(types_in_file) = file_types.get(&file_key)
+                        && types_in_file.contains(rel.target())
+                    {
+                        resolved.add_relationship(rel.clone());
+                        continue;
+                    }
+                }
+
+                let tgt_modules = &name_modules[rel.target()];
+                if tgt_modules.len() == 1 {
+                    resolved.add_relationship(rel.clone());
+                }
+            }
+        }
+    }
+    resolved
+}
+
+fn filter_external_imports(graph: CodeGraph, root: &Path) -> CodeGraph {
+    let known_dirs: HashSet<String> = std::fs::read_dir(root)
+        .into_iter()
+        .flatten()
+        .filter_map(|e| e.ok())
+        .filter(|e| e.path().is_dir())
+        .filter_map(|e| e.file_name().into_string().ok())
+        .map(|s| s.to_lowercase())
+        .collect();
+
+    let module_names: HashSet<String> = graph
+        .modules()
+        .iter()
+        .map(|m| m.as_str().to_lowercase())
+        .collect();
+
+    let all_known: HashSet<&str> = known_dirs
+        .iter()
+        .map(|s| s.as_str())
+        .chain(module_names.iter().map(|s| s.as_str()))
+        .collect();
+
+    let mut filtered = CodeGraph::new();
+    for element in graph.elements() {
+        filtered.add_element(element.clone());
+    }
+    for rel in graph.relationships() {
+        if rel.kind() == RelationshipKind::Import {
+            let target_top = rel.target().split('.').next().unwrap_or("").to_lowercase();
+            if !all_known.contains(target_top.as_str()) {
+                continue;
+            }
+        }
+        filtered.add_relationship(rel.clone());
+    }
+    filtered
+}
+
+fn infer_module(file_path: &str, root: &Path, config: &AnalysisConfig) -> Option<ModuleName> {
+    let relative = if let Some(stripped) = file_path.strip_prefix(root.to_str().unwrap_or("")) {
+        stripped.trim_start_matches('/')
+    } else {
+        file_path
+    };
+
+    for (pattern, module_name) in config.module_mappings() {
+        if relative.starts_with(pattern) {
+            return ModuleName::new(module_name).ok();
+        }
+    }
+
+    let parts: Vec<&str> = relative.split('/').collect();
+    if parts.len() <= 1 {
+        return None;
+    }
+
+    let module_dir = if parts[0] == "crates" && parts.len() > 2 {
+        // workspace: crates/<crate-name>/src/...
+        parts[1]
+    } else if parts[0] == "src" && parts.len() > 2 {
+        // single project: src/<module>/...
+        parts[1]
+    } else if parts[0] != "src" && parts.len() > 1 {
+        parts[0]
+    } else {
+        return None;
+    };
+
+    let capitalized = module_dir
+        .split('-')
+        .map(|seg| {
+            if seg.is_empty() {
+                String::new()
+            } else {
+                format!("{}{}", seg[..1].to_uppercase(), &seg[1..])
+            }
+        })
+        .collect::<Vec<_>>()
+        .join("-");
+
+    ModuleName::new(&capitalized).ok()
+}
+
+pub struct AnalyzeCodebaseResult {
+    graph: CodeGraph,
+    warnings: Vec<AnalysisWarning>,
+}
+
+impl AnalyzeCodebaseResult {
+    pub fn graph(&self) -> &CodeGraph {
+        &self.graph
+    }
+
+    pub fn warnings(&self) -> &[AnalysisWarning] {
+        &self.warnings
+    }
+}

crates/application/src/queries/mod.rs

@@ -0,0 +1,5 @@
+mod analyze_codebase;
+mod render_diagrams;
+
+pub use analyze_codebase::{AnalyzeCodebase, AnalyzeCodebaseResult};
+pub use render_diagrams::RenderDiagrams;

crates/application/src/queries/render_diagrams.rs

@@ -0,0 +1,45 @@
+use archlens_domain::{
+    CodeGraph, DomainError, OutputConfig,
+    ports::{DiagramRenderer, OutputWriter},
+};
+
+pub struct RenderDiagrams<R, W>
+where
+    R: DiagramRenderer,
+    W: OutputWriter,
+{
+    renderer: R,
+    writer: W,
+}
+
+impl<R, W> RenderDiagrams<R, W>
+where
+    R: DiagramRenderer,
+    W: OutputWriter,
+{
+    pub fn new(renderer: R, writer: W) -> Self {
+        Self { renderer, writer }
+    }
+
+    pub fn execute(&self, graph: &CodeGraph, config: &OutputConfig) -> Result<(), DomainError> {
+        if config.split_by_module() {
+            let overview = self.renderer.render(graph)?;
+            self.writer.write(&overview)?;
+
+            for module in graph.modules() {
+                let subgraph = graph.subgraph_by_module(&module);
+                let output = self.renderer.render(&subgraph)?;
+                self.writer.write(&output)?;
+            }
+        } else {
+            let output = self.renderer.render(graph)?;
+            self.writer.write(&output)?;
+        }
+
+        Ok(())
+    }
+
+    pub fn writer(&self) -> &W {
+        &self.writer
+    }
+}

crates/application/tests/analyze_codebase_tests.rs

@@ -0,0 +1,344 @@
+mod fakes;
+
+use std::path::Path;
+
+use archlens_application::queries::AnalyzeCodebase;
+use archlens_domain::{
+    AnalysisConfig, AnalysisResult, AnalysisWarning, CodeElement, CodeElementKind, DomainError,
+    FilePath, Language, Relationship, RelationshipKind, SourceFile,
+};
+
+use fakes::{FakeFileDiscovery, FakeSourceAnalyzer};
+
+#[test]
+fn analyzes_discovered_files_and_builds_code_graph() {
+    let files = vec![
+        SourceFile::new(FilePath::new("src/order.rs").unwrap(), Language::Rust),
+        SourceFile::new(FilePath::new("src/service.rs").unwrap(), Language::Rust),
+    ];
+
+    let discovery = FakeFileDiscovery::new(files);
+
+    let analyzer = FakeSourceAnalyzer::new()
+        .with_result(
+            "src/order.rs",
+            AnalysisResult::new(
+                vec![
+                    CodeElement::new(
+                        "Order",
+                        CodeElementKind::Struct,
+                        FilePath::new("src/order.rs").unwrap(),
+                        1,
+                    )
+                    .unwrap(),
+                ],
+                vec![],
+                vec![],
+            ),
+        )
+        .with_result(
+            "src/service.rs",
+            AnalysisResult::new(
+                vec![
+                    CodeElement::new(
+                        "OrderService",
+                        CodeElementKind::Class,
+                        FilePath::new("src/service.rs").unwrap(),
+                        1,
+                    )
+                    .unwrap(),
+                ],
+                vec![
+                    Relationship::new("OrderService", "Order", RelationshipKind::Composition)
+                        .unwrap(),
+                ],
+                vec![],
+            ),
+        );
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case
+        .execute(Path::new("."), &AnalysisConfig::default())
+        .unwrap();
+
+    assert_eq!(result.graph().elements().len(), 2);
+    assert_eq!(result.graph().relationships().len(), 1);
+    assert!(result.warnings().is_empty());
+}
+
+#[test]
+fn empty_file_list_returns_empty_graph() {
+    let discovery = FakeFileDiscovery::empty();
+    let analyzer = FakeSourceAnalyzer::new();
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case
+        .execute(Path::new("."), &AnalysisConfig::default())
+        .unwrap();
+
+    assert!(result.graph().elements().is_empty());
+    assert!(result.graph().relationships().is_empty());
+    assert!(result.warnings().is_empty());
+}
+
+#[test]
+fn aggregates_warnings_from_multiple_files() {
+    let files = vec![
+        SourceFile::new(FilePath::new("src/a.rs").unwrap(), Language::Rust),
+        SourceFile::new(FilePath::new("src/b.rs").unwrap(), Language::Rust),
+    ];
+
+    let discovery = FakeFileDiscovery::new(files);
+    let analyzer = FakeSourceAnalyzer::new()
+        .with_result(
+            "src/a.rs",
+            AnalysisResult::new(
+                vec![],
+                vec![],
+                vec![
+                    AnalysisWarning::new(FilePath::new("src/a.rs").unwrap(), 10, "unknown macro")
+                        .unwrap(),
+                ],
+            ),
+        )
+        .with_result(
+            "src/b.rs",
+            AnalysisResult::new(
+                vec![],
+                vec![],
+                vec![
+                    AnalysisWarning::new(
+                        FilePath::new("src/b.rs").unwrap(),
+                        5,
+                        "unparseable block",
+                    )
+                    .unwrap(),
+                ],
+            ),
+        );
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case
+        .execute(Path::new("."), &AnalysisConfig::default())
+        .unwrap();
+
+    assert_eq!(result.warnings().len(), 2);
+}
+
+#[test]
+fn analysis_error_on_file_collects_warning_and_continues() {
+    let files = vec![
+        SourceFile::new(FilePath::new("src/good.rs").unwrap(), Language::Rust),
+        SourceFile::new(FilePath::new("src/broken.rs").unwrap(), Language::Rust),
+    ];
+
+    let discovery = FakeFileDiscovery::new(files);
+    let analyzer = FakeSourceAnalyzer::new()
+        .with_result(
+            "src/good.rs",
+            AnalysisResult::new(
+                vec![
+                    CodeElement::new(
+                        "Good",
+                        CodeElementKind::Struct,
+                        FilePath::new("src/good.rs").unwrap(),
+                        1,
+                    )
+                    .unwrap(),
+                ],
+                vec![],
+                vec![],
+            ),
+        )
+        .with_error(
+            "src/broken.rs",
+            DomainError::AnalysisError("parse failed".to_string()),
+        );
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case
+        .execute(Path::new("."), &AnalysisConfig::default())
+        .unwrap();
+
+    assert_eq!(result.graph().elements().len(), 1);
+    assert_eq!(result.graph().elements()[0].name(), "Good");
+    assert_eq!(result.warnings().len(), 1);
+}
+
+#[test]
+fn infers_module_from_directory_structure() {
+    let files = vec![
+        SourceFile::new(
+            FilePath::new("/project/src/orders/service.rs").unwrap(),
+            Language::Rust,
+        ),
+        SourceFile::new(
+            FilePath::new("/project/src/billing/invoice.rs").unwrap(),
+            Language::Rust,
+        ),
+        SourceFile::new(
+            FilePath::new("/project/src/lib.rs").unwrap(),
+            Language::Rust,
+        ),
+    ];
+
+    let discovery = FakeFileDiscovery::new(files);
+    let analyzer = FakeSourceAnalyzer::new()
+        .with_result(
+            "/project/src/orders/service.rs",
+            AnalysisResult::new(
+                vec![
+                    CodeElement::new(
+                        "OrderService",
+                        CodeElementKind::Class,
+                        FilePath::new("/project/src/orders/service.rs").unwrap(),
+                        1,
+                    )
+                    .unwrap(),
+                ],
+                vec![],
+                vec![],
+            ),
+        )
+        .with_result(
+            "/project/src/billing/invoice.rs",
+            AnalysisResult::new(
+                vec![
+                    CodeElement::new(
+                        "Invoice",
+                        CodeElementKind::Struct,
+                        FilePath::new("/project/src/billing/invoice.rs").unwrap(),
+                        1,
+                    )
+                    .unwrap(),
+                ],
+                vec![],
+                vec![],
+            ),
+        )
+        .with_result(
+            "/project/src/lib.rs",
+            AnalysisResult::new(
+                vec![
+                    CodeElement::new(
+                        "App",
+                        CodeElementKind::Struct,
+                        FilePath::new("/project/src/lib.rs").unwrap(),
+                        1,
+                    )
+                    .unwrap(),
+                ],
+                vec![],
+                vec![],
+            ),
+        );
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case
+        .execute(Path::new("/project"), &AnalysisConfig::default())
+        .unwrap();
+
+    let order_svc = result
+        .graph()
+        .elements()
+        .iter()
+        .find(|e| e.name() == "OrderService")
+        .unwrap();
+    assert_eq!(order_svc.module().unwrap().as_str(), "Orders");
+
+    let invoice = result
+        .graph()
+        .elements()
+        .iter()
+        .find(|e| e.name() == "Invoice")
+        .unwrap();
+    assert_eq!(invoice.module().unwrap().as_str(), "Billing");
+
+    let app = result
+        .graph()
+        .elements()
+        .iter()
+        .find(|e| e.name() == "App")
+        .unwrap();
+    assert!(app.module().is_none());
+}
+
+#[test]
+fn infers_nested_module_from_deep_directories() {
+    let files = vec![SourceFile::new(
+        FilePath::new("/project/src/orders/models/order.rs").unwrap(),
+        Language::Rust,
+    )];
+
+    let discovery = FakeFileDiscovery::new(files);
+    let analyzer = FakeSourceAnalyzer::new().with_result(
+        "/project/src/orders/models/order.rs",
+        AnalysisResult::new(
+            vec![
+                CodeElement::new(
+                    "Order",
+                    CodeElementKind::Struct,
+                    FilePath::new("/project/src/orders/models/order.rs").unwrap(),
+                    1,
+                )
+                .unwrap(),
+            ],
+            vec![],
+            vec![],
+        ),
+    );
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case
+        .execute(Path::new("/project"), &AnalysisConfig::default())
+        .unwrap();
+
+    let order = result
+        .graph()
+        .elements()
+        .iter()
+        .find(|e| e.name() == "Order")
+        .unwrap();
+    assert_eq!(order.module().unwrap().as_str(), "Orders");
+}
+
+#[test]
+fn respects_config_module_mappings() {
+    let files = vec![SourceFile::new(
+        FilePath::new("/project/src/infra/db.rs").unwrap(),
+        Language::Rust,
+    )];
+
+    let discovery = FakeFileDiscovery::new(files);
+    let analyzer = FakeSourceAnalyzer::new().with_result(
+        "/project/src/infra/db.rs",
+        AnalysisResult::new(
+            vec![
+                CodeElement::new(
+                    "DbPool",
+                    CodeElementKind::Struct,
+                    FilePath::new("/project/src/infra/db.rs").unwrap(),
+                    1,
+                )
+                .unwrap(),
+            ],
+            vec![],
+            vec![],
+        ),
+    );
+
+    let mut mappings = std::collections::HashMap::new();
+    mappings.insert("src/infra".to_string(), "Infrastructure".to_string());
+    let config = AnalysisConfig::default().with_module_mappings(mappings);
+
+    let use_case = AnalyzeCodebase::new(discovery, analyzer);
+    let result = use_case.execute(Path::new("/project"), &config).unwrap();
+
+    let db = result
+        .graph()
+        .elements()
+        .iter()
+        .find(|e| e.name() == "DbPool")
+        .unwrap();
+    assert_eq!(db.module().unwrap().as_str(), "Infrastructure");
+}

crates/application/tests/fakes/diagram_renderer.rs

@@ -0,0 +1,17 @@
+use archlens_domain::{CodeGraph, DomainError, RenderOutput, RenderedFile, ports::DiagramRenderer};
+
+pub struct FakeDiagramRenderer;
+
+impl FakeDiagramRenderer {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl DiagramRenderer for FakeDiagramRenderer {
+    fn render(&self, graph: &CodeGraph) -> Result<RenderOutput, DomainError> {
+        let content = format!("graph with {} elements", graph.elements().len());
+        let file = RenderedFile::new("output.mmd", &content)?;
+        Ok(RenderOutput::single(file))
+    }
+}

crates/application/tests/fakes/file_discovery.rs

@@ -0,0 +1,27 @@
+use std::path::Path;
+
+use archlens_domain::{AnalysisConfig, DomainError, SourceFile, ports::FileDiscovery};
+
+pub struct FakeFileDiscovery {
+    files: Vec<SourceFile>,
+}
+
+impl FakeFileDiscovery {
+    pub fn new(files: Vec<SourceFile>) -> Self {
+        Self { files }
+    }
+
+    pub fn empty() -> Self {
+        Self { files: Vec::new() }
+    }
+}
+
+impl FileDiscovery for FakeFileDiscovery {
+    fn discover(
+        &self,
+        _root: &Path,
+        _config: &AnalysisConfig,
+    ) -> Result<Vec<SourceFile>, DomainError> {
+        Ok(self.files.clone())
+    }
+}

crates/application/tests/fakes/mod.rs

@@ -0,0 +1,9 @@
+mod diagram_renderer;
+mod file_discovery;
+mod output_writer;
+mod source_analyzer;
+
+pub use diagram_renderer::FakeDiagramRenderer;
+pub use file_discovery::FakeFileDiscovery;
+pub use output_writer::FakeOutputWriter;
+pub use source_analyzer::FakeSourceAnalyzer;

crates/application/tests/fakes/output_writer.rs

@@ -0,0 +1,26 @@
+use std::cell::RefCell;
+
+use archlens_domain::{DomainError, RenderOutput, ports::OutputWriter};
+
+pub struct FakeOutputWriter {
+    written: RefCell<Vec<RenderOutput>>,
+}
+
+impl FakeOutputWriter {
+    pub fn new() -> Self {
+        Self {
+            written: RefCell::new(Vec::new()),
+        }
+    }
+
+    pub fn written_outputs(&self) -> Vec<RenderOutput> {
+        self.written.borrow().clone()
+    }
+}
+
+impl OutputWriter for FakeOutputWriter {
+    fn write(&self, output: &RenderOutput) -> Result<(), DomainError> {
+        self.written.borrow_mut().push(output.clone());
+        Ok(())
+    }
+}

crates/application/tests/fakes/source_analyzer.rs

@@ -0,0 +1,43 @@
+use std::collections::HashMap;
+
+use archlens_domain::{AnalysisResult, DomainError, SourceFile, ports::SourceAnalyzer};
+
+enum FakeResponse {
+    Success(AnalysisResult),
+    Failure(DomainError),
+}
+
+pub struct FakeSourceAnalyzer {
+    results: HashMap<String, FakeResponse>,
+}
+
+impl FakeSourceAnalyzer {
+    pub fn new() -> Self {
+        Self {
+            results: HashMap::new(),
+        }
+    }
+
+    pub fn with_result(mut self, file_path: &str, result: AnalysisResult) -> Self {
+        self.results
+            .insert(file_path.to_string(), FakeResponse::Success(result));
+        self
+    }
+
+    pub fn with_error(mut self, file_path: &str, error: DomainError) -> Self {
+        self.results
+            .insert(file_path.to_string(), FakeResponse::Failure(error));
+        self
+    }
+}
+
+impl SourceAnalyzer for FakeSourceAnalyzer {
+    fn analyze_file(&self, file: &SourceFile) -> Result<AnalysisResult, DomainError> {
+        let key = file.path().as_str().to_string();
+        match self.results.get(&key) {
+            Some(FakeResponse::Success(result)) => Ok(result.clone()),
+            Some(FakeResponse::Failure(_)) => Err(DomainError::AnalysisError(key)),
+            None => Ok(AnalysisResult::empty()),
+        }
+    }
+}

crates/application/tests/render_diagrams_tests.rs

@@ -0,0 +1,78 @@
+mod fakes;
+
+use archlens_application::queries::RenderDiagrams;
+use archlens_domain::{
+    CodeElement, CodeElementKind, CodeGraph, FilePath, ModuleName, OutputConfig,
+};
+
+use fakes::{FakeDiagramRenderer, FakeOutputWriter};
+
+fn build_graph() -> CodeGraph {
+    let mut graph = CodeGraph::new();
+    graph.add_element(
+        CodeElement::new(
+            "OrderService",
+            CodeElementKind::Class,
+            FilePath::new("src/service.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Orders").unwrap()),
+    );
+    graph.add_element(
+        CodeElement::new(
+            "BillingService",
+            CodeElementKind::Class,
+            FilePath::new("src/billing.rs").unwrap(),
+            1,
+        )
+        .unwrap()
+        .with_module(ModuleName::new("Billing").unwrap()),
+    );
+    graph
+}
+
+#[test]
+fn renders_single_diagram_and_writes_output() {
+    let renderer = FakeDiagramRenderer::new();
+    let writer = FakeOutputWriter::new();
+    let config = OutputConfig::default();
+
+    let use_case = RenderDiagrams::new(renderer, writer);
+    use_case.execute(&build_graph(), &config).unwrap();
+
+    let outputs = use_case.writer().written_outputs();
+    assert_eq!(outputs.len(), 1);
+    assert_eq!(outputs[0].files().len(), 1);
+}
+
+#[test]
+fn split_mode_renders_overview_plus_per_module_diagrams() {
+    let renderer = FakeDiagramRenderer::new();
+    let writer = FakeOutputWriter::new();
+    let config = OutputConfig::default().with_split_by_module(true);
+
+    let graph = build_graph(); // has 2 modules: Orders, Billing
+
+    let use_case = RenderDiagrams::new(renderer, writer);
+    use_case.execute(&graph, &config).unwrap();
+
+    let outputs = use_case.writer().written_outputs();
+    // 1 overview + 2 module diagrams = 3 writes
+    assert_eq!(outputs.len(), 3);
+}
+
+#[test]
+fn empty_graph_still_produces_output() {
+    let renderer = FakeDiagramRenderer::new();
+    let writer = FakeOutputWriter::new();
+    let config = OutputConfig::default();
+
+    let graph = CodeGraph::new();
+
+    let use_case = RenderDiagrams::new(renderer, writer);
+    use_case.execute(&graph, &config).unwrap();
+
+    let outputs = use_case.writer().written_outputs();
+    assert_eq!(outputs.len(), 1);
+}

crates/domain/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "archlens-domain"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+thiserror.workspace = true

crates/domain/src/aggregates/code_graph.rs

@@ -0,0 +1,78 @@
+use std::collections::HashSet;
+
+use crate::{CodeElement, ModuleName, Relationship};
+
+#[derive(Debug, Clone)]
+pub struct CodeGraph {
+    elements: Vec<CodeElement>,
+    relationships: Vec<Relationship>,
+}
+
+impl Default for CodeGraph {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl CodeGraph {
+    pub fn new() -> Self {
+        Self {
+            elements: Vec::new(),
+            relationships: Vec::new(),
+        }
+    }
+
+    pub fn add_element(&mut self, element: CodeElement) {
+        self.elements.push(element);
+    }
+
+    pub fn add_relationship(&mut self, relationship: Relationship) {
+        self.relationships.push(relationship);
+    }
+
+    pub fn elements(&self) -> &[CodeElement] {
+        &self.elements
+    }
+
+    pub fn relationships(&self) -> &[Relationship] {
+        &self.relationships
+    }
+
+    pub fn modules(&self) -> Vec<ModuleName> {
+        let mut seen = HashSet::new();
+        let mut modules = Vec::new();
+
+        for element in &self.elements {
+            if let Some(module) = element.module()
+                && seen.insert(module.as_str().to_string())
+            {
+                modules.push(module.clone());
+            }
+        }
+
+        modules
+    }
+
+    pub fn subgraph_by_module(&self, module: &ModuleName) -> CodeGraph {
+        let filtered_elements: Vec<CodeElement> = self
+            .elements
+            .iter()
+            .filter(|e| e.module().is_some_and(|m| m == module))
+            .cloned()
+            .collect();
+
+        let element_names: HashSet<&str> = filtered_elements.iter().map(|e| e.name()).collect();
+
+        let filtered_relationships: Vec<Relationship> = self
+            .relationships
+            .iter()
+            .filter(|r| element_names.contains(r.source()) && element_names.contains(r.target()))
+            .cloned()
+            .collect();
+
+        CodeGraph {
+            elements: filtered_elements,
+            relationships: filtered_relationships,
+        }
+    }
+}

crates/domain/src/aggregates/mod.rs

@@ -0,0 +1,3 @@
+mod code_graph;
+
+pub use code_graph::CodeGraph;

crates/domain/src/entities/code_element.rs

@@ -0,0 +1,111 @@
+use crate::{CodeElementKind, DomainError, FilePath, ModuleName, Visibility};
+
+#[derive(Debug, Clone)]
+pub struct CodeElement {
+    name: String,
+    kind: CodeElementKind,
+    file_path: FilePath,
+    line: usize,
+    visibility: Visibility,
+    module: Option<ModuleName>,
+    generics: Vec<String>,
+    attributes: Vec<String>,
+    fields: Vec<String>,
+    methods: Vec<String>,
+}
+
+impl CodeElement {
+    pub fn new(
+        name: &str,
+        kind: CodeElementKind,
+        file_path: FilePath,
+        line: usize,
+    ) -> Result<Self, DomainError> {
+        let trimmed = name.trim();
+        if trimmed.is_empty() {
+            return Err(DomainError::EmptyValue("CodeElement name"));
+        }
+        Ok(Self {
+            name: trimmed.to_string(),
+            kind,
+            file_path,
+            line,
+            visibility: Visibility::Public,
+            module: None,
+            generics: Vec::new(),
+            attributes: Vec::new(),
+            fields: Vec::new(),
+            methods: Vec::new(),
+        })
+    }
+
+    pub fn with_visibility(mut self, visibility: Visibility) -> Self {
+        self.visibility = visibility;
+        self
+    }
+
+    pub fn with_module(mut self, module: ModuleName) -> Self {
+        self.module = Some(module);
+        self
+    }
+
+    pub fn with_generics(mut self, generics: Vec<String>) -> Self {
+        self.generics = generics;
+        self
+    }
+
+    pub fn with_attributes(mut self, attributes: Vec<String>) -> Self {
+        self.attributes = attributes;
+        self
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn kind(&self) -> CodeElementKind {
+        self.kind
+    }
+
+    pub fn file_path(&self) -> &FilePath {
+        &self.file_path
+    }
+
+    pub fn line(&self) -> usize {
+        self.line
+    }
+
+    pub fn visibility(&self) -> Visibility {
+        self.visibility
+    }
+
+    pub fn module(&self) -> Option<&ModuleName> {
+        self.module.as_ref()
+    }
+
+    pub fn generics(&self) -> &[String] {
+        &self.generics
+    }
+
+    pub fn attributes(&self) -> &[String] {
+        &self.attributes
+    }
+
+    pub fn with_fields(mut self, fields: Vec<String>) -> Self {
+        self.fields = fields;
+        self
+    }
+
+    pub fn with_methods(mut self, methods: Vec<String>) -> Self {
+        self.methods = methods;
+        self
+    }
+
+    pub fn fields(&self) -> &[String] {
+        &self.fields
+    }
+
+    pub fn methods(&self) -> &[String] {
+        &self.methods
+    }
+}

crates/domain/src/entities/mod.rs

@@ -0,0 +1,5 @@
+mod code_element;
+mod relationship;
+
+pub use code_element::CodeElement;
+pub use relationship::Relationship;

crates/domain/src/entities/relationship.rs

@@ -0,0 +1,49 @@
+use crate::{DomainError, FilePath, RelationshipKind};
+
+#[derive(Debug, Clone)]
+pub struct Relationship {
+    source: String,
+    target: String,
+    kind: RelationshipKind,
+    source_file: Option<FilePath>,
+}
+
+impl Relationship {
+    pub fn new(source: &str, target: &str, kind: RelationshipKind) -> Result<Self, DomainError> {
+        let source = source.trim();
+        let target = target.trim();
+        if source.is_empty() {
+            return Err(DomainError::EmptyValue("Relationship source"));
+        }
+        if target.is_empty() {
+            return Err(DomainError::EmptyValue("Relationship target"));
+        }
+        Ok(Self {
+            source: source.to_string(),
+            target: target.to_string(),
+            kind,
+            source_file: None,
+        })
+    }
+
+    pub fn with_source_file(mut self, file: FilePath) -> Self {
+        self.source_file = Some(file);
+        self
+    }
+
+    pub fn source(&self) -> &str {
+        &self.source
+    }
+
+    pub fn target(&self) -> &str {
+        &self.target
+    }
+
+    pub fn kind(&self) -> RelationshipKind {
+        self.kind
+    }
+
+    pub fn source_file(&self) -> Option<&FilePath> {
+        self.source_file.as_ref()
+    }
+}

crates/domain/src/error.rs

@@ -0,0 +1,14 @@
+#[derive(Debug, thiserror::Error)]
+pub enum DomainError {
+    #[error("{0} cannot be empty")]
+    EmptyValue(&'static str),
+
+    #[error("failed to analyze: {0}")]
+    AnalysisError(String),
+
+    #[error("IO error: {0}")]
+    IoError(String),
+
+    #[error("config error: {0}")]
+    ConfigError(String),
+}

crates/domain/src/lib.rs

@@ -0,0 +1,14 @@
+mod error;
+
+pub mod aggregates;
+pub mod entities;
+pub mod ports;
+pub mod value_objects;
+
+pub use aggregates::CodeGraph;
+pub use entities::{CodeElement, Relationship};
+pub use error::DomainError;
+pub use value_objects::analysis::{AnalysisConfig, AnalysisResult, AnalysisWarning};
+pub use value_objects::graph::{CodeElementKind, RelationshipKind, Visibility};
+pub use value_objects::output::{DiagramLevel, OutputConfig, RenderOutput, RenderedFile};
+pub use value_objects::source::{FilePath, Language, ModuleName, SourceFile};

crates/domain/src/ports/config_loader.rs

@@ -0,0 +1,6 @@
+use crate::{AnalysisConfig, DomainError, OutputConfig};
+
+pub trait ConfigLoader {
+    fn load_analysis_config(&self) -> Result<AnalysisConfig, DomainError>;
+    fn load_output_config(&self) -> Result<OutputConfig, DomainError>;
+}

crates/domain/src/ports/diagram_renderer.rs

@@ -0,0 +1,5 @@
+use crate::{CodeGraph, DomainError, RenderOutput};
+
+pub trait DiagramRenderer {
+    fn render(&self, graph: &CodeGraph) -> Result<RenderOutput, DomainError>;
+}

crates/domain/src/ports/file_discovery.rs

@@ -0,0 +1,9 @@
+use crate::{AnalysisConfig, DomainError, SourceFile};
+
+pub trait FileDiscovery {
+    fn discover(
+        &self,
+        root: &std::path::Path,
+        config: &AnalysisConfig,
+    ) -> Result<Vec<SourceFile>, DomainError>;
+}

crates/domain/src/ports/mod.rs

@@ -0,0 +1,13 @@
+mod config_loader;
+mod diagram_renderer;
+mod file_discovery;
+mod output_writer;
+mod project_analyzer;
+mod source_analyzer;
+
+pub use config_loader::ConfigLoader;
+pub use diagram_renderer::DiagramRenderer;
+pub use file_discovery::FileDiscovery;
+pub use output_writer::OutputWriter;
+pub use project_analyzer::ProjectAnalyzer;
+pub use source_analyzer::SourceAnalyzer;

crates/domain/src/ports/output_writer.rs

@@ -0,0 +1,5 @@
+use crate::{DomainError, RenderOutput};
+
+pub trait OutputWriter {
+    fn write(&self, output: &RenderOutput) -> Result<(), DomainError>;
+}

crates/domain/src/ports/project_analyzer.rs

@@ -0,0 +1,7 @@
+use std::path::Path;
+
+use crate::{CodeGraph, DomainError};
+
+pub trait ProjectAnalyzer {
+    fn analyze(&self, root: &Path) -> Result<CodeGraph, DomainError>;
+}

crates/domain/src/ports/source_analyzer.rs

@@ -0,0 +1,5 @@
+use crate::{AnalysisResult, DomainError, SourceFile};
+
+pub trait SourceAnalyzer: Send + Sync {
+    fn analyze_file(&self, file: &SourceFile) -> Result<AnalysisResult, DomainError>;
+}

crates/domain/src/value_objects/analysis/analysis_config.rs

@@ -0,0 +1,60 @@
+use std::collections::HashMap;
+
+use crate::DiagramLevel;
+
+#[derive(Debug, Clone)]
+pub struct AnalysisConfig {
+    excludes: Vec<String>,
+    level: DiagramLevel,
+    module_mappings: HashMap<String, String>,
+    scope: Option<String>,
+}
+
+impl AnalysisConfig {
+    pub fn with_excludes(mut self, excludes: Vec<String>) -> Self {
+        self.excludes = excludes;
+        self
+    }
+
+    pub fn with_level(mut self, level: DiagramLevel) -> Self {
+        self.level = level;
+        self
+    }
+
+    pub fn with_module_mappings(mut self, mappings: HashMap<String, String>) -> Self {
+        self.module_mappings = mappings;
+        self
+    }
+
+    pub fn excludes(&self) -> &[String] {
+        &self.excludes
+    }
+
+    pub fn level(&self) -> DiagramLevel {
+        self.level
+    }
+
+    pub fn with_scope(mut self, scope: String) -> Self {
+        self.scope = Some(scope);
+        self
+    }
+
+    pub fn module_mappings(&self) -> &HashMap<String, String> {
+        &self.module_mappings
+    }
+
+    pub fn scope(&self) -> Option<&str> {
+        self.scope.as_deref()
+    }
+}
+
+impl Default for AnalysisConfig {
+    fn default() -> Self {
+        Self {
+            excludes: Vec::new(),
+            level: DiagramLevel::Module,
+            module_mappings: HashMap::new(),
+            scope: None,
+        }
+    }
+}

crates/domain/src/value_objects/analysis/analysis_result.rs

@@ -0,0 +1,42 @@
+use crate::{AnalysisWarning, CodeElement, Relationship};
+
+#[derive(Debug, Clone)]
+pub struct AnalysisResult {
+    elements: Vec<CodeElement>,
+    relationships: Vec<Relationship>,
+    warnings: Vec<AnalysisWarning>,
+}
+
+impl AnalysisResult {
+    pub fn new(
+        elements: Vec<CodeElement>,
+        relationships: Vec<Relationship>,
+        warnings: Vec<AnalysisWarning>,
+    ) -> Self {
+        Self {
+            elements,
+            relationships,
+            warnings,
+        }
+    }
+
+    pub fn empty() -> Self {
+        Self {
+            elements: Vec::new(),
+            relationships: Vec::new(),
+            warnings: Vec::new(),
+        }
+    }
+
+    pub fn elements(&self) -> &[CodeElement] {
+        &self.elements
+    }
+
+    pub fn relationships(&self) -> &[Relationship] {
+        &self.relationships
+    }
+
+    pub fn warnings(&self) -> &[AnalysisWarning] {
+        &self.warnings
+    }
+}

crates/domain/src/value_objects/analysis/analysis_warning.rs

@@ -0,0 +1,34 @@
+use crate::{DomainError, FilePath};
+
+#[derive(Debug, Clone)]
+pub struct AnalysisWarning {
+    file_path: FilePath,
+    line: usize,
+    message: String,
+}
+
+impl AnalysisWarning {
+    pub fn new(file_path: FilePath, line: usize, message: &str) -> Result<Self, DomainError> {
+        let message = message.trim();
+        if message.is_empty() {
+            return Err(DomainError::EmptyValue("AnalysisWarning message"));
+        }
+        Ok(Self {
+            file_path,
+            line,
+            message: message.to_string(),
+        })
+    }
+
+    pub fn file_path(&self) -> &FilePath {
+        &self.file_path
+    }
+
+    pub fn line(&self) -> usize {
+        self.line
+    }
+
+    pub fn message(&self) -> &str {
+        &self.message
+    }
+}

crates/domain/src/value_objects/analysis/mod.rs

@@ -0,0 +1,7 @@
+mod analysis_config;
+mod analysis_result;
+mod analysis_warning;
+
+pub use analysis_config::AnalysisConfig;
+pub use analysis_result::AnalysisResult;
+pub use analysis_warning::AnalysisWarning;

crates/domain/src/value_objects/graph/code_element_kind.rs

@@ -0,0 +1,9 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum CodeElementKind {
+    Class,
+    Struct,
+    Trait,
+    Interface,
+    Enum,
+    Project,
+}

crates/domain/src/value_objects/graph/mod.rs

@@ -0,0 +1,7 @@
+mod code_element_kind;
+mod relationship_kind;
+mod visibility;
+
+pub use code_element_kind::CodeElementKind;
+pub use relationship_kind::RelationshipKind;
+pub use visibility::Visibility;

crates/domain/src/value_objects/graph/relationship_kind.rs

@@ -0,0 +1,6 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum RelationshipKind {
+    Inheritance,
+    Composition,
+    Import,
+}

crates/domain/src/value_objects/graph/visibility.rs

@@ -0,0 +1,6 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Visibility {
+    Public,
+    Private,
+    Internal,
+}

crates/domain/src/value_objects/mod.rs

@@ -0,0 +1,4 @@
+pub mod analysis;
+pub mod graph;
+pub mod output;
+pub mod source;

crates/domain/src/value_objects/output/diagram_level.rs

@@ -0,0 +1,6 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum DiagramLevel {
+    Project,
+    Module,
+    Type,
+}

crates/domain/src/value_objects/output/mod.rs

@@ -0,0 +1,9 @@
+mod diagram_level;
+mod output_config;
+mod render_output;
+mod rendered_file;
+
+pub use diagram_level::DiagramLevel;
+pub use output_config::OutputConfig;
+pub use render_output::RenderOutput;
+pub use rendered_file::RenderedFile;

crates/domain/src/value_objects/output/output_config.rs

@@ -0,0 +1,25 @@
+#[derive(Debug, Clone, Default)]
+pub struct OutputConfig {
+    split_by_module: bool,
+    output_path: Option<String>,
+}
+
+impl OutputConfig {
+    pub fn with_split_by_module(mut self, split: bool) -> Self {
+        self.split_by_module = split;
+        self
+    }
+
+    pub fn with_output_path(mut self, path: String) -> Self {
+        self.output_path = Some(path);
+        self
+    }
+
+    pub fn split_by_module(&self) -> bool {
+        self.split_by_module
+    }
+
+    pub fn output_path(&self) -> Option<&str> {
+        self.output_path.as_deref()
+    }
+}

crates/domain/src/value_objects/output/render_output.rs

@@ -0,0 +1,20 @@
+use crate::RenderedFile;
+
+#[derive(Debug, Clone)]
+pub struct RenderOutput {
+    files: Vec<RenderedFile>,
+}
+
+impl RenderOutput {
+    pub fn new(files: Vec<RenderedFile>) -> Self {
+        Self { files }
+    }
+
+    pub fn single(file: RenderedFile) -> Self {
+        Self { files: vec![file] }
+    }
+
+    pub fn files(&self) -> &[RenderedFile] {
+        &self.files
+    }
+}

crates/domain/src/value_objects/output/rendered_file.rs

@@ -0,0 +1,32 @@
+use crate::DomainError;
+
+#[derive(Debug, Clone)]
+pub struct RenderedFile {
+    name: String,
+    content: String,
+}
+
+impl RenderedFile {
+    pub fn new(name: &str, content: &str) -> Result<Self, DomainError> {
+        let name = name.trim();
+        let content = content.trim();
+        if name.is_empty() {
+            return Err(DomainError::EmptyValue("RenderedFile name"));
+        }
+        if content.is_empty() {
+            return Err(DomainError::EmptyValue("RenderedFile content"));
+        }
+        Ok(Self {
+            name: name.to_string(),
+            content: content.to_string(),
+        })
+    }
+
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    pub fn content(&self) -> &str {
+        &self.content
+    }
+}

crates/domain/src/value_objects/source/file_path.rs

@@ -0,0 +1,18 @@
+use crate::DomainError;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct FilePath(String);
+
+impl FilePath {
+    pub fn new(value: &str) -> Result<Self, DomainError> {
+        let trimmed = value.trim();
+        if trimmed.is_empty() {
+            return Err(DomainError::EmptyValue("FilePath"));
+        }
+        Ok(Self(trimmed.to_string()))
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}

crates/domain/src/value_objects/source/language.rs

@@ -0,0 +1,16 @@
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum Language {
+    Rust,
+    CSharp,
+    Python,
+}
+
+impl Language {
+    pub fn name(&self) -> &'static str {
+        match self {
+            Self::Rust => "Rust",
+            Self::CSharp => "CSharp",
+            Self::Python => "Python",
+        }
+    }
+}

crates/domain/src/value_objects/source/mod.rs

@@ -0,0 +1,9 @@
+mod file_path;
+mod language;
+mod module_name;
+mod source_file;
+
+pub use file_path::FilePath;
+pub use language::Language;
+pub use module_name::ModuleName;
+pub use source_file::SourceFile;

crates/domain/src/value_objects/source/module_name.rs

@@ -0,0 +1,18 @@
+use crate::DomainError;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct ModuleName(String);
+
+impl ModuleName {
+    pub fn new(value: &str) -> Result<Self, DomainError> {
+        let trimmed = value.trim();
+        if trimmed.is_empty() {
+            return Err(DomainError::EmptyValue("ModuleName"));
+        }
+        Ok(Self(trimmed.to_string()))
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.0
+    }
+}

crates/domain/src/value_objects/source/source_file.rs

@@ -0,0 +1,21 @@
+use crate::{FilePath, Language};
+
+#[derive(Debug, Clone)]
+pub struct SourceFile {
+    path: FilePath,
+    language: Language,
+}
+
+impl SourceFile {
+    pub fn new(path: FilePath, language: Language) -> Self {
+        Self { path, language }
+    }
+
+    pub fn path(&self) -> &FilePath {
+        &self.path
+    }
+
+    pub fn language(&self) -> Language {
+        self.language
+    }
+}

crates/domain/tests/analysis_result_tests.rs

@@ -0,0 +1,39 @@
+use archlens_domain::{
+    AnalysisResult, AnalysisWarning, CodeElement, CodeElementKind, FilePath, Relationship,
+    RelationshipKind,
+};
+
+#[test]
+fn analysis_result_collects_elements_relationships_and_warnings() {
+    let element = CodeElement::new(
+        "Order",
+        CodeElementKind::Struct,
+        FilePath::new("src/order.rs").unwrap(),
+        1,
+    )
+    .unwrap();
+
+    let relationship =
+        Relationship::new("OrderService", "Order", RelationshipKind::Composition).unwrap();
+
+    let warning = AnalysisWarning::new(
+        FilePath::new("src/broken.rs").unwrap(),
+        10,
+        "unparseable macro",
+    )
+    .unwrap();
+
+    let result = AnalysisResult::new(vec![element], vec![relationship], vec![warning]);
+
+    assert_eq!(result.elements().len(), 1);
+    assert_eq!(result.relationships().len(), 1);
+    assert_eq!(result.warnings().len(), 1);
+}
+
+#[test]
+fn empty_analysis_result() {
+    let result = AnalysisResult::empty();
+    assert!(result.elements().is_empty());
+    assert!(result.relationships().is_empty());
+    assert!(result.warnings().is_empty());
+}

crates/domain/tests/analysis_warning_tests.rs

@@ -0,0 +1,21 @@
+use archlens_domain::{AnalysisWarning, FilePath};
+
+#[test]
+fn warning_carries_location_and_message() {
+    let warning = AnalysisWarning::new(
+        FilePath::new("src/broken.rs").unwrap(),
+        42,
+        "could not parse struct definition",
+    )
+    .unwrap();
+
+    assert_eq!(warning.file_path().as_str(), "src/broken.rs");
+    assert_eq!(warning.line(), 42);
+    assert_eq!(warning.message(), "could not parse struct definition");
+}
+
+#[test]
+fn warning_rejects_empty_message() {
+    let result = AnalysisWarning::new(FilePath::new("src/broken.rs").unwrap(), 1, "");
+    assert!(result.is_err());
+}

crates/domain/tests/code_element_tests.rs

@@ -0,0 +1,107 @@
+use archlens_domain::{CodeElement, CodeElementKind, FilePath, ModuleName, Visibility};
+
+#[test]
+fn code_element_is_created_with_required_fields() {
+    let element = CodeElement::new(
+        "OrderService",
+        CodeElementKind::Class,
+        FilePath::new("src/orders/service.rs").unwrap(),
+        42,
+    )
+    .unwrap();
+
+    assert_eq!(element.name(), "OrderService");
+    assert_eq!(element.kind(), CodeElementKind::Class);
+    assert_eq!(element.file_path().as_str(), "src/orders/service.rs");
+    assert_eq!(element.line(), 42);
+}
+
+#[test]
+fn code_element_with_empty_name_is_rejected() {
+    let result = CodeElement::new(
+        "",
+        CodeElementKind::Class,
+        FilePath::new("src/main.rs").unwrap(),
+        1,
+    );
+    assert!(result.is_err());
+}
+
+#[test]
+fn code_element_defaults_to_public_visibility() {
+    let element = CodeElement::new(
+        "Order",
+        CodeElementKind::Struct,
+        FilePath::new("src/order.rs").unwrap(),
+        1,
+    )
+    .unwrap();
+
+    assert_eq!(element.visibility(), Visibility::Public);
+}
+
+#[test]
+fn code_element_with_visibility() {
+    let element = CodeElement::new(
+        "Order",
+        CodeElementKind::Struct,
+        FilePath::new("src/order.rs").unwrap(),
+        1,
+    )
+    .unwrap()
+    .with_visibility(Visibility::Private);
+
+    assert_eq!(element.visibility(), Visibility::Private);
+}
+
+#[test]
+fn code_element_with_module_path() {
+    let module = ModuleName::new("Orders").unwrap();
+    let element = CodeElement::new(
+        "Order",
+        CodeElementKind::Struct,
+        FilePath::new("src/orders/order.rs").unwrap(),
+        1,
+    )
+    .unwrap()
+    .with_module(module.clone());
+
+    assert_eq!(element.module(), Some(&module));
+}
+
+#[test]
+fn code_element_with_generics() {
+    let element = CodeElement::new(
+        "Repository",
+        CodeElementKind::Trait,
+        FilePath::new("src/repo.rs").unwrap(),
+        1,
+    )
+    .unwrap()
+    .with_generics(vec!["T".to_string()]);
+
+    assert_eq!(element.generics(), &["T"]);
+}
+
+#[test]
+fn code_element_with_attributes() {
+    let element = CodeElement::new(
+        "OrderController",
+        CodeElementKind::Class,
+        FilePath::new("src/controller.cs").unwrap(),
+        1,
+    )
+    .unwrap()
+    .with_attributes(vec!["ApiController".to_string()]);
+
+    assert_eq!(element.attributes(), &["ApiController"]);
+}
+
+#[test]
+fn all_element_kinds_exist() {
+    let _class = CodeElementKind::Class;
+    let _struct = CodeElementKind::Struct;
+    let _trait = CodeElementKind::Trait;
+    let _interface = CodeElementKind::Interface;
+    let _enum = CodeElementKind::Enum;
+}

crates/domain/tests/code_graph_tests.rs

@@ -0,0 +1,130 @@
+use archlens_domain::{
+    CodeElement, CodeElementKind, CodeGraph, FilePath, ModuleName, Relationship, RelationshipKind,
+};
+
+fn make_element(name: &str, module: Option<&str>) -> CodeElement {
+    let mut element = CodeElement::new(
+        name,
+        CodeElementKind::Class,
+        FilePath::new(&format!("src/{name}.rs")).unwrap(),
+        1,
+    )
+    .unwrap();
+
+    if let Some(m) = module {
+        element = element.with_module(ModuleName::new(m).unwrap());
+    }
+
+    element
+}
+
+#[test]
+fn empty_graph_has_no_elements() {
+    let graph = CodeGraph::new();
+    assert!(graph.elements().is_empty());
+    assert!(graph.relationships().is_empty());
+}
+
+#[test]
+fn graph_stores_added_elements() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(make_element("OrderService", None));
+    graph.add_element(make_element("Order", None));
+
+    assert_eq!(graph.elements().len(), 2);
+}
+
+#[test]
+fn graph_stores_relationships() {
+    let mut graph = CodeGraph::new();
+    let service = make_element("OrderService", None);
+    let repo = make_element("OrderRepository", None);
+
+    graph.add_element(service);
+    graph.add_element(repo);
+    graph.add_relationship(
+        Relationship::new(
+            "OrderService",
+            "OrderRepository",
+            RelationshipKind::Composition,
+        )
+        .unwrap(),
+    );
+
+    assert_eq!(graph.relationships().len(), 1);
+    let rel = &graph.relationships()[0];
+    assert_eq!(rel.source(), "OrderService");
+    assert_eq!(rel.target(), "OrderRepository");
+    assert_eq!(rel.kind(), RelationshipKind::Composition);
+}
+
+#[test]
+fn subgraph_by_module_filters_elements() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(make_element("OrderService", Some("Orders")));
+    graph.add_element(make_element("Order", Some("Orders")));
+    graph.add_element(make_element("BillingService", Some("Billing")));
+
+    let module = ModuleName::new("Orders").unwrap();
+    let subgraph = graph.subgraph_by_module(&module);
+
+    assert_eq!(subgraph.elements().len(), 2);
+    assert!(
+        subgraph
+            .elements()
+            .iter()
+            .all(|e| e.module().unwrap().as_str() == "Orders")
+    );
+}
+
+#[test]
+fn subgraph_includes_relationships_within_module() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(make_element("OrderService", Some("Orders")));
+    graph.add_element(make_element("Order", Some("Orders")));
+    graph.add_element(make_element("BillingService", Some("Billing")));
+
+    graph.add_relationship(
+        Relationship::new("OrderService", "Order", RelationshipKind::Composition).unwrap(),
+    );
+    graph.add_relationship(
+        Relationship::new(
+            "OrderService",
+            "BillingService",
+            RelationshipKind::Composition,
+        )
+        .unwrap(),
+    );
+
+    let module = ModuleName::new("Orders").unwrap();
+    let subgraph = graph.subgraph_by_module(&module);
+
+    assert_eq!(subgraph.relationships().len(), 1);
+    assert_eq!(subgraph.relationships()[0].target(), "Order");
+}
+
+#[test]
+fn subgraph_of_nonexistent_module_is_empty() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(make_element("OrderService", Some("Orders")));
+
+    let module = ModuleName::new("Unknown").unwrap();
+    let subgraph = graph.subgraph_by_module(&module);
+
+    assert!(subgraph.elements().is_empty());
+    assert!(subgraph.relationships().is_empty());
+}
+
+#[test]
+fn graph_lists_unique_modules() {
+    let mut graph = CodeGraph::new();
+    graph.add_element(make_element("OrderService", Some("Orders")));
+    graph.add_element(make_element("Order", Some("Orders")));
+    graph.add_element(make_element("BillingService", Some("Billing")));
+    graph.add_element(make_element("Orphan", None));
+
+    let modules = graph.modules();
+    assert_eq!(modules.len(), 2);
+    assert!(modules.iter().any(|m| m.as_str() == "Orders"));
+    assert!(modules.iter().any(|m| m.as_str() == "Billing"));
+}

crates/domain/tests/config_tests.rs

@@ -0,0 +1,37 @@
+use archlens_domain::{AnalysisConfig, DiagramLevel, OutputConfig};
+
+#[test]
+fn analysis_config_has_sensible_defaults() {
+    let config = AnalysisConfig::default();
+    assert!(config.excludes().is_empty());
+    assert_eq!(config.level(), DiagramLevel::Module);
+    assert!(config.module_mappings().is_empty());
+}
+
+#[test]
+fn analysis_config_with_excludes() {
+    let config =
+        AnalysisConfig::default().with_excludes(vec!["tests/".to_string(), "vendor/".to_string()]);
+
+    assert_eq!(config.excludes().len(), 2);
+}
+
+#[test]
+fn output_config_has_sensible_defaults() {
+    let config = OutputConfig::default();
+    assert!(!config.split_by_module());
+    assert!(config.output_path().is_none());
+}
+
+#[test]
+fn output_config_with_split() {
+    let config = OutputConfig::default().with_split_by_module(true);
+    assert!(config.split_by_module());
+}
+
+#[test]
+fn all_diagram_levels_exist() {
+    let _project = DiagramLevel::Project;
+    let _module = DiagramLevel::Module;
+    let _type_level = DiagramLevel::Type;
+}

crates/domain/tests/file_path_tests.rs

@@ -0,0 +1,29 @@
+use archlens_domain::FilePath;
+
+#[test]
+fn valid_file_path_is_created() {
+    let path = FilePath::new("src/main.rs").unwrap();
+    assert_eq!(path.as_str(), "src/main.rs");
+}
+
+#[test]
+fn empty_file_path_is_rejected() {
+    let result = FilePath::new("");
+    assert!(result.is_err());
+}
+
+#[test]
+fn whitespace_only_file_path_is_rejected() {
+    let result = FilePath::new("   ");
+    assert!(result.is_err());
+}
+
+#[test]
+fn file_paths_are_comparable() {
+    let a = FilePath::new("src/main.rs").unwrap();
+    let b = FilePath::new("src/main.rs").unwrap();
+    let c = FilePath::new("src/lib.rs").unwrap();
+
+    assert_eq!(a, b);
+    assert_ne!(a, c);
+}

crates/domain/tests/language_tests.rs

@@ -0,0 +1,18 @@
+use archlens_domain::Language;
+
+#[test]
+fn known_languages_are_available() {
+    let rust = Language::Rust;
+    let csharp = Language::CSharp;
+    let python = Language::Python;
+
+    assert_eq!(rust.name(), "Rust");
+    assert_eq!(csharp.name(), "CSharp");
+    assert_eq!(python.name(), "Python");
+}
+
+#[test]
+fn languages_are_comparable() {
+    assert_eq!(Language::Rust, Language::Rust);
+    assert_ne!(Language::Rust, Language::Python);
+}

crates/domain/tests/module_name_tests.rs

@@ -0,0 +1,23 @@
+use archlens_domain::ModuleName;
+
+#[test]
+fn valid_module_name_is_created() {
+    let name = ModuleName::new("Orders").unwrap();
+    assert_eq!(name.as_str(), "Orders");
+}
+
+#[test]
+fn empty_module_name_is_rejected() {
+    let result = ModuleName::new("");
+    assert!(result.is_err());
+}
+
+#[test]
+fn module_names_are_comparable() {
+    let a = ModuleName::new("Orders").unwrap();
+    let b = ModuleName::new("Orders").unwrap();
+    let c = ModuleName::new("Billing").unwrap();
+
+    assert_eq!(a, b);
+    assert_ne!(a, c);
+}

crates/domain/tests/render_output_tests.rs

@@ -0,0 +1,37 @@
+use archlens_domain::{RenderOutput, RenderedFile};
+
+#[test]
+fn rendered_file_carries_name_and_content() {
+    let file = RenderedFile::new("overview.mmd", "graph TD;").unwrap();
+    assert_eq!(file.name(), "overview.mmd");
+    assert_eq!(file.content(), "graph TD;");
+}
+
+#[test]
+fn rendered_file_rejects_empty_name() {
+    let result = RenderedFile::new("", "content");
+    assert!(result.is_err());
+}
+
+#[test]
+fn rendered_file_rejects_empty_content() {
+    let result = RenderedFile::new("file.mmd", "");
+    assert!(result.is_err());
+}
+
+#[test]
+fn render_output_holds_multiple_files() {
+    let files = vec![
+        RenderedFile::new("overview.mmd", "graph TD;").unwrap(),
+        RenderedFile::new("orders.mmd", "classDiagram").unwrap(),
+    ];
+    let output = RenderOutput::new(files);
+    assert_eq!(output.files().len(), 2);
+}
+
+#[test]
+fn render_output_can_be_single_file() {
+    let file = RenderedFile::new("arch.mmd", "graph TD;").unwrap();
+    let output = RenderOutput::single(file);
+    assert_eq!(output.files().len(), 1);
+}

crates/domain/tests/source_file_tests.rs

@@ -0,0 +1,10 @@
+use archlens_domain::{FilePath, Language, SourceFile};
+
+#[test]
+fn source_file_carries_path_and_language() {
+    let path = FilePath::new("src/main.rs").unwrap();
+    let file = SourceFile::new(path.clone(), Language::Rust);
+
+    assert_eq!(file.path(), &path);
+    assert_eq!(file.language(), Language::Rust);
+}

crates/presentation/Cargo.toml

@@ -0,0 +1,28 @@
+[package]
+name = "archlens"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[[bin]]
+name = "archlens"
+path = "src/main.rs"
+
+[dependencies]
+archlens-domain.workspace = true
+archlens-application.workspace = true
+archlens-tree-sitter.workspace = true
+archlens-walkdir.workspace = true
+archlens-mermaid.workspace = true
+archlens-ascii.workspace = true
+archlens-file-writer.workspace = true
+archlens-stdout-writer.workspace = true
+archlens-toml-config.workspace = true
+archlens-cargo-workspace.workspace = true
+anyhow.workspace = true
+clap.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true