feat: codebase mapper with CODEBASE.md generation (#190)

- Add scan_project Rust command that walks the directory tree and detects project type
- Add CODEBASE as a managed ProjectFile type alongside PROJECT/REQUIREMENTS/ROADMAP/STATE
- Add mapCodebase() store function that scans and sends an analysis prompt to Claude
- Add CODEBASE tab to ProjectContextPanel with Map/Remap buttons and auto-reload on idle
- Update PROJECT_CONTEXT_SYSTEM_ADDENDUM to include CODEBASE.md reference

src-tauri/src/commands.rs

@@ -2337,6 +2337,160 @@ pub async fn get_mcp_server_details(name: String) -> Result<String, String> {
     }
 }
 
+// ==================== Codebase Mapper ====================
+
+/// Directories to skip when scanning (always ignored regardless of .gitignore)
+const SCAN_SKIP_DIRS: &[&str] = &[
+    ".git",
+    "node_modules",
+    "target",
+    ".next",
+    "dist",
+    "build",
+    "out",
+    "__pycache__",
+    ".cache",
+    ".pytest_cache",
+    "vendor",
+    ".idea",
+    ".vscode",
+    "coverage",
+    ".nyc_output",
+    "venv",
+    ".venv",
+    "env",
+    ".tox",
+];
+
+/// Files that indicate the project type
+const PROJECT_MARKERS: &[(&str, &str)] = &[
+    ("Cargo.toml", "Rust"),
+    ("package.json", "Node.js"),
+    ("pyproject.toml", "Python"),
+    ("requirements.txt", "Python"),
+    ("go.mod", "Go"),
+    ("pom.xml", "Java (Maven)"),
+    ("build.gradle", "Java (Gradle)"),
+    ("Gemfile", "Ruby"),
+    ("composer.json", "PHP"),
+    ("*.csproj", "C#/.NET"),
+    ("CMakeLists.txt", "C/C++ (CMake)"),
+    ("Makefile", "C/C++"),
+];
+
+#[derive(Debug, Serialize)]
+pub struct ProjectScan {
+    pub working_dir: String,
+    pub file_tree: String,
+    pub detected_type: String,
+    pub key_files: Vec<String>,
+}
+
+/// Recursively build a file tree string, respecting skip dirs, up to `max_depth` levels.
+fn build_file_tree(
+    dir: &std::path::Path,
+    prefix: &str,
+    depth: usize,
+    max_depth: usize,
+    lines: &mut Vec<String>,
+) {
+    if depth > max_depth {
+        lines.push(format!("{}...", prefix));
+        return;
+    }
+
+    let Ok(entries) = std::fs::read_dir(dir) else {
+        return;
+    };
+
+    let mut items: Vec<std::fs::DirEntry> = entries
+        .filter_map(|e| e.ok())
+        .collect();
+    items.sort_by_key(|e| {
+        let name = e.file_name().to_string_lossy().to_lowercase();
+        // Sort: hidden last, directories first
+        let is_hidden = name.starts_with('.');
+        let is_dir = e.path().is_dir();
+        (is_hidden, !is_dir, name)
+    });
+
+    let count = items.len();
+    for (i, entry) in items.iter().enumerate() {
+        let name = entry.file_name().to_string_lossy().to_string();
+        let is_last = i == count - 1;
+        let connector = if is_last { "└── " } else { "├── " };
+        let child_prefix = if is_last {
+            format!("{}    ", prefix)
+        } else {
+            format!("{}│   ", prefix)
+        };
+
+        let path = entry.path();
+        if path.is_dir() {
+            if SCAN_SKIP_DIRS.contains(&name.as_str()) {
+                lines.push(format!("{}{}{}/ (skipped)", prefix, connector, name));
+                continue;
+            }
+            lines.push(format!("{}{}{}/", prefix, connector, name));
+            build_file_tree(&path, &child_prefix, depth + 1, max_depth, lines);
+        } else {
+            lines.push(format!("{}{}{}", prefix, connector, name));
+        }
+    }
+}
+
+#[tauri::command]
+pub async fn scan_project(working_dir: String) -> Result<ProjectScan, String> {
+    let dir_path = std::path::Path::new(&working_dir);
+
+    if !dir_path.exists() {
+        return Err(format!("Directory does not exist: {}", working_dir));
+    }
+    if !dir_path.is_dir() {
+        return Err(format!("Path is not a directory: {}", working_dir));
+    }
+
+    // Detect project type by checking for marker files
+    let mut detected_type = "Unknown".to_string();
+    let mut key_files: Vec<String> = Vec::new();
+
+    for (marker, project_type) in PROJECT_MARKERS {
+        let marker_path = dir_path.join(marker);
+        if marker_path.exists() {
+            if detected_type == "Unknown" {
+                detected_type = project_type.to_string();
+            }
+            key_files.push(marker.to_string());
+        }
+    }
+
+    // Also collect other notable root-level files
+    let notable_root_files = &[
+        "README.md", "CLAUDE.md", "LICENSE", ".env.example",
+        "docker-compose.yml", "Dockerfile", ".github",
+        "tsconfig.json", "vitest.config.ts", "eslint.config.js",
+        "check-all.sh", "tauri.conf.json",
+    ];
+    for file in notable_root_files {
+        let file_path = dir_path.join(file);
+        if file_path.exists() && !key_files.contains(&file.to_string()) {
+            key_files.push(file.to_string());
+        }
+    }
+
+    // Build file tree (max 4 levels deep)
+    let mut lines: Vec<String> = vec![format!("{}/", working_dir)];
+    build_file_tree(dir_path, "", 0, 4, &mut lines);
+    let file_tree = lines.join("\n");
+
+    Ok(ProjectScan {
+        working_dir,
+        file_tree,
+        detected_type,
+        key_files,
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src-tauri/src/lib.rs

@@ -220,6 +220,7 @@ pub fn run() {
             save_draft,
             delete_draft,
             delete_all_drafts,
+            scan_project,
         ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");

src/lib/components/ProjectContextPanel.svelte

@@ -1,10 +1,13 @@
 <script lang="ts">
   import { onMount } from "svelte";
+  import { get } from "svelte/store";
   import {
     projectContextStore,
     PROJECT_FILE_NAMES,
     type ProjectFile,
   } from "$lib/stores/projectContext";
+  import { characterState } from "$lib/stores/character";
+  import { claudeStore } from "$lib/stores/claude";
 
   interface Props {
     onClose: () => void;
@@ -14,15 +17,17 @@
 
   const { onClose, onInject, workingDirectory }: Props = $props();
 
-  const PROJECT_FILES: ProjectFile[] = ["PROJECT", "REQUIREMENTS", "ROADMAP", "STATE"];
+  const ALL_FILES: ProjectFile[] = ["PROJECT", "REQUIREMENTS", "ROADMAP", "STATE", "CODEBASE"];
 
   const contents = $derived(projectContextStore.contents);
   const isLoading = $derived(projectContextStore.isLoading);
   const isSaving = $derived(projectContextStore.isSaving);
   const activeFile = $derived(projectContextStore.activeFile);
+  const isMappingCodebase = $derived(projectContextStore.isMappingCodebase);
 
   let editContent = $state("");
   let hasUnsavedChanges = $state(false);
+  let previousCharacterState = $state<string>("idle");
 
   onMount(() => {
     projectContextStore.loadAll(workingDirectory);
@@ -31,10 +36,24 @@
   $effect(() => {
     const file = $activeFile;
     const fileContent = $contents[file];
-    editContent = fileContent ?? projectContextStore.getTemplate(file);
+    if (file === "CODEBASE") {
+      editContent = fileContent ?? "";
+    } else {
+      editContent = fileContent ?? projectContextStore.getTemplate(file);
+    }
     hasUnsavedChanges = false;
   });
 
+  // Auto-reload CODEBASE.md when Claude finishes generating it
+  $effect(() => {
+    const currentState = $characterState;
+    if ($isMappingCodebase && previousCharacterState !== "idle" && currentState === "idle") {
+      projectContextStore.loadFile("CODEBASE", workingDirectory);
+      projectContextStore.finishMapping();
+    }
+    previousCharacterState = currentState;
+  });
+
   function handleTabSwitch(file: ProjectFile): void {
     projectContextStore.setActiveFile(file);
   }
@@ -63,6 +82,12 @@
   function fileExists(file: ProjectFile): boolean {
     return $contents[file] !== null;
   }
+
+  async function handleMapCodebase(): Promise<void> {
+    const conversationId = get(claudeStore.activeConversationId);
+    if (!conversationId) return;
+    await projectContextStore.mapCodebase(workingDirectory, conversationId);
+  }
 </script>
 
 <div
@@ -86,7 +111,25 @@
         <h2 id="project-context-title" class="text-xl font-semibold text-[var(--text-primary)]">
           Project Context
         </h2>
-        {#if $isLoading[$activeFile]}
+        {#if $activeFile === "CODEBASE"}
+          {#if $isMappingCodebase}
+            <span class="text-xs text-[var(--text-tertiary)]">Mapping codebase...</span>
+          {:else if $isLoading[$activeFile]}
+            <span class="text-xs text-[var(--text-tertiary)]">Loading...</span>
+          {:else if fileExists($activeFile)}
+            <span
+              class="text-xs px-2 py-0.5 rounded-full bg-green-500/20 text-green-400 border border-green-500/30"
+            >
+              ✓ File exists
+            </span>
+          {:else}
+            <span
+              class="text-xs px-2 py-0.5 rounded-full bg-amber-500/20 text-amber-400 border border-amber-500/30"
+            >
+              ✗ Not generated
+            </span>
+          {/if}
+        {:else if $isLoading[$activeFile]}
           <span class="text-xs text-[var(--text-tertiary)]">Loading...</span>
         {:else if fileExists($activeFile)}
           <span
@@ -123,7 +166,7 @@
 
     <!-- Tab bar -->
     <div class="flex border-b border-[var(--border-color)] px-4">
-      {#each PROJECT_FILES as file (file)}
+      {#each ALL_FILES as file (file)}
         <button
           onclick={() => handleTabSwitch(file)}
           class="px-4 py-2 text-sm font-medium transition-colors relative {$activeFile === file
@@ -140,13 +183,47 @@
 
     <!-- Editor area -->
     <div class="flex-1 overflow-hidden p-4 min-h-0">
-      <textarea
-        value={editContent}
-        oninput={handleTextChange}
-        class="w-full h-full min-h-[400px] bg-[var(--bg-secondary)] border border-[var(--border-color)] rounded-lg p-4 font-mono text-sm text-[var(--text-primary)] resize-none focus:outline-none focus:border-[var(--accent-primary)] leading-relaxed"
-        placeholder="File content will appear here..."
-        spellcheck="false"
-      ></textarea>
+      {#if $activeFile === "CODEBASE" && !fileExists("CODEBASE") && !$isMappingCodebase}
+        <!-- CODEBASE not generated yet — show prompt to map -->
+        <div class="flex flex-col items-center justify-center h-full gap-4 text-center">
+          <div class="text-4xl">🗺️</div>
+          <h3 class="text-lg font-semibold text-[var(--text-primary)]">No Codebase Map Yet</h3>
+          <p class="text-sm text-[var(--text-secondary)] max-w-md">
+            Generate a <span class="font-mono text-xs">CODEBASE.md</span> file by asking Claude to analyse
+            this project. Claude will scan the directory structure and create a comprehensive overview
+            of the architecture and key components.
+          </p>
+          <button
+            onclick={handleMapCodebase}
+            class="px-5 py-2 text-sm btn-trans-gradient rounded-lg transition-colors"
+          >
+            Map Codebase
+          </button>
+        </div>
+      {:else if $activeFile === "CODEBASE" && $isMappingCodebase}
+        <!-- Mapping in progress -->
+        <div class="flex flex-col items-center justify-center h-full gap-4 text-center">
+          <div class="text-4xl animate-spin">⚙️</div>
+          <h3 class="text-lg font-semibold text-[var(--text-primary)]">Mapping Codebase...</h3>
+          <p class="text-sm text-[var(--text-secondary)]">
+            Claude is analysing the project and writing <span class="font-mono text-xs"
+              >CODEBASE.md</span
+            >. This will auto-reload when complete.
+          </p>
+        </div>
+      {:else}
+        <textarea
+          value={editContent}
+          oninput={handleTextChange}
+          readonly={$activeFile === "CODEBASE"}
+          class="w-full h-full min-h-[400px] bg-[var(--bg-secondary)] border border-[var(--border-color)] rounded-lg p-4 font-mono text-sm text-[var(--text-primary)] resize-none focus:outline-none focus:border-[var(--accent-primary)] leading-relaxed {$activeFile ===
+          'CODEBASE'
+            ? 'opacity-80 cursor-default'
+            : ''}"
+          placeholder="File content will appear here..."
+          spellcheck="false"
+        ></textarea>
+      {/if}
     </div>
 
     <!-- Footer -->
@@ -157,29 +234,50 @@
         <span class="font-mono">{workingDirectory}/{PROJECT_FILE_NAMES[$activeFile]}</span>
       </div>
       <div class="flex items-center gap-2">
-        <button
-          onclick={handleUseTemplate}
-          class="px-3 py-1.5 text-sm text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded-lg transition-colors"
-        >
-          Use Template
-        </button>
-        <button
-          onclick={handleInject}
-          class="px-3 py-1.5 text-sm text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded-lg transition-colors"
-        >
-          Inject into Prompt
-        </button>
-        <button
-          onclick={handleSave}
-          disabled={$isSaving[$activeFile]}
-          class="px-4 py-1.5 text-sm btn-trans-gradient rounded-lg transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
-        >
-          {#if $isSaving[$activeFile]}
-            Saving...
-          {:else}
-            Save
-          {/if}
-        </button>
+        {#if $activeFile === "CODEBASE"}
+          <button
+            onclick={() => projectContextStore.loadFile("CODEBASE", workingDirectory)}
+            disabled={$isLoading.CODEBASE || $isMappingCodebase}
+            class="px-3 py-1.5 text-sm text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded-lg transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+          >
+            Refresh
+          </button>
+          <button
+            onclick={handleMapCodebase}
+            disabled={$isMappingCodebase}
+            class="px-4 py-1.5 text-sm btn-trans-gradient rounded-lg transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+          >
+            {#if $isMappingCodebase}
+              Mapping...
+            {:else}
+              {fileExists("CODEBASE") ? "Remap Codebase" : "Map Codebase"}
+            {/if}
+          </button>
+        {:else}
+          <button
+            onclick={handleUseTemplate}
+            class="px-3 py-1.5 text-sm text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded-lg transition-colors"
+          >
+            Use Template
+          </button>
+          <button
+            onclick={handleInject}
+            class="px-3 py-1.5 text-sm text-[var(--text-secondary)] hover:text-[var(--text-primary)] bg-[var(--bg-secondary)] hover:bg-[var(--bg-tertiary)] border border-[var(--border-color)] rounded-lg transition-colors"
+          >
+            Inject into Prompt
+          </button>
+          <button
+            onclick={handleSave}
+            disabled={$isSaving[$activeFile]}
+            class="px-4 py-1.5 text-sm btn-trans-gradient rounded-lg transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
+          >
+            {#if $isSaving[$activeFile]}
+              Saving...
+            {:else}
+              Save
+            {/if}
+          </button>
+        {/if}
       </div>
     </div>
   </div>

src/lib/stores/projectContext.test.ts

@@ -9,24 +9,30 @@ import {
   PROJECT_CONTEXT_SYSTEM_ADDENDUM,
   injectTextStore,
   type ProjectFile,
+  type ProjectScan,
 } from "./projectContext";
 
 describe("PROJECT_FILE_NAMES", () => {
-  it("maps all four project file types", () => {
+  it("maps all five project file types", () => {
     expect(PROJECT_FILE_NAMES.PROJECT).toBe("PROJECT.md");
     expect(PROJECT_FILE_NAMES.REQUIREMENTS).toBe("REQUIREMENTS.md");
     expect(PROJECT_FILE_NAMES.ROADMAP).toBe("ROADMAP.md");
     expect(PROJECT_FILE_NAMES.STATE).toBe("STATE.md");
+    expect(PROJECT_FILE_NAMES.CODEBASE).toBe("CODEBASE.md");
   });
 });
 
 describe("PROJECT_TEMPLATES", () => {
-  const files: ProjectFile[] = ["PROJECT", "REQUIREMENTS", "ROADMAP", "STATE"];
+  const editableFiles: ProjectFile[] = ["PROJECT", "REQUIREMENTS", "ROADMAP", "STATE"];
 
-  it.each(files)("returns a non-empty template for %s", (file) => {
+  it.each(editableFiles)("returns a non-empty template for %s", (file) => {
     expect(PROJECT_TEMPLATES[file]).toBeTruthy();
     expect(PROJECT_TEMPLATES[file].length).toBeGreaterThan(0);
   });
+
+  it("has an empty string template for CODEBASE (auto-generated)", () => {
+    expect(PROJECT_TEMPLATES.CODEBASE).toBe("");
+  });
 });
 
 describe("projectContextStore", () => {
@@ -41,6 +47,7 @@ describe("projectContextStore", () => {
       expect(state.REQUIREMENTS).toBeNull();
       expect(state.ROADMAP).toBeNull();
       expect(state.STATE).toBeNull();
+      expect(state.CODEBASE).toBeNull();
     });
 
     it("has false isLoading for all files", () => {
@@ -49,6 +56,7 @@ describe("projectContextStore", () => {
       expect(state.REQUIREMENTS).toBe(false);
       expect(state.ROADMAP).toBe(false);
       expect(state.STATE).toBe(false);
+      expect(state.CODEBASE).toBe(false);
     });
 
     it("has false isSaving for all files", () => {
@@ -57,18 +65,25 @@ describe("projectContextStore", () => {
       expect(state.REQUIREMENTS).toBe(false);
       expect(state.ROADMAP).toBe(false);
       expect(state.STATE).toBe(false);
+      expect(state.CODEBASE).toBe(false);
     });
 
     it("has PROJECT as the default activeFile", () => {
       expect(get(projectContextStore.activeFile)).toBe("PROJECT");
     });
 
+    it("has false isMappingCodebase initially", () => {
+      expect(get(projectContextStore.isMappingCodebase)).toBe(false);
+    });
+
     it("exposes all expected methods", () => {
       expect(typeof projectContextStore.loadFile).toBe("function");
       expect(typeof projectContextStore.saveFile).toBe("function");
       expect(typeof projectContextStore.loadAll).toBe("function");
       expect(typeof projectContextStore.setActiveFile).toBe("function");
       expect(typeof projectContextStore.getTemplate).toBe("function");
+      expect(typeof projectContextStore.mapCodebase).toBe("function");
+      expect(typeof projectContextStore.finishMapping).toBe("function");
     });
   });
 
@@ -203,7 +218,7 @@ describe("projectContextStore", () => {
   });
 
   describe("loadAll", () => {
-    it("loads all four files in parallel", async () => {
+    it("loads all five files in parallel", async () => {
       setMockInvokeResult("read_file_content", "file content");
 
       await projectContextStore.loadAll("/home/naomi/myproject");
@@ -215,6 +230,7 @@ describe("projectContextStore", () => {
       expect(paths).toContain("/home/naomi/myproject/REQUIREMENTS.md");
       expect(paths).toContain("/home/naomi/myproject/ROADMAP.md");
       expect(paths).toContain("/home/naomi/myproject/STATE.md");
+      expect(paths).toContain("/home/naomi/myproject/CODEBASE.md");
     });
 
     it("sets all files isLoading to false after completion", async () => {
@@ -227,6 +243,7 @@ describe("projectContextStore", () => {
       expect(loadingState.REQUIREMENTS).toBe(false);
       expect(loadingState.ROADMAP).toBe(false);
       expect(loadingState.STATE).toBe(false);
+      expect(loadingState.CODEBASE).toBe(false);
     });
   });
 
@@ -257,6 +274,91 @@ describe("projectContextStore", () => {
       const uniqueTemplates = new Set(templates);
       expect(uniqueTemplates.size).toBe(files.length);
     });
+
+    it("returns empty string for CODEBASE", () => {
+      expect(projectContextStore.getTemplate("CODEBASE")).toBe("");
+    });
+  });
+
+  describe("mapCodebase", () => {
+    const mockScan: ProjectScan = {
+      working_dir: "/home/naomi/myproject",
+      file_tree: "/home/naomi/myproject/\n├── src/\n└── package.json",
+      detected_type: "Node.js",
+      key_files: ["package.json"],
+    };
+
+    it("calls scan_project with the working directory", async () => {
+      setMockInvokeResult("scan_project", mockScan);
+      setMockInvokeResult("send_prompt", undefined);
+
+      await projectContextStore.mapCodebase("/home/naomi/myproject", "conv-123");
+
+      expect(invoke).toHaveBeenCalledWith("scan_project", {
+        workingDir: "/home/naomi/myproject",
+      });
+    });
+
+    it("calls send_prompt with the conversation id and a non-empty prompt", async () => {
+      setMockInvokeResult("scan_project", mockScan);
+      setMockInvokeResult("send_prompt", undefined);
+
+      await projectContextStore.mapCodebase("/home/naomi/myproject", "conv-123");
+
+      expect(invoke).toHaveBeenCalledWith("send_prompt", {
+        conversationId: "conv-123",
+        message: expect.stringContaining("CODEBASE.md"),
+      });
+    });
+
+    it("prompt includes detected project type", async () => {
+      setMockInvokeResult("scan_project", mockScan);
+      setMockInvokeResult("send_prompt", undefined);
+
+      await projectContextStore.mapCodebase("/home/naomi/myproject", "conv-123");
+
+      const sendCall = vi.mocked(invoke).mock.calls.find(([cmd]) => cmd === "send_prompt");
+      const message = (sendCall?.[1] as { message: string } | undefined)?.message ?? "";
+      expect(message).toContain("Node.js");
+    });
+
+    it("prompt includes file tree", async () => {
+      setMockInvokeResult("scan_project", mockScan);
+      setMockInvokeResult("send_prompt", undefined);
+
+      await projectContextStore.mapCodebase("/home/naomi/myproject", "conv-123");
+
+      const sendCall = vi.mocked(invoke).mock.calls.find(([cmd]) => cmd === "send_prompt");
+      const message = (sendCall?.[1] as { message: string } | undefined)?.message ?? "";
+      expect(message).toContain("package.json");
+    });
+
+    it("resets isMappingCodebase to false on error", async () => {
+      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+      setMockInvokeResult("scan_project", new Error("Scan failed"));
+
+      await projectContextStore.mapCodebase("/home/naomi/myproject", "conv-123");
+
+      expect(get(projectContextStore.isMappingCodebase)).toBe(false);
+      consoleSpy.mockRestore();
+    });
+
+    it("logs error when scan_project fails", async () => {
+      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+      setMockInvokeResult("scan_project", new Error("Scan failed"));
+
+      await projectContextStore.mapCodebase("/home/naomi/myproject", "conv-123");
+
+      expect(consoleSpy).toHaveBeenCalledWith("Failed to map codebase:", expect.any(Error));
+      consoleSpy.mockRestore();
+    });
+  });
+
+  describe("finishMapping", () => {
+    it("sets isMappingCodebase to false", () => {
+      projectContextStore.finishMapping();
+      expect(get(projectContextStore.isMappingCodebase)).toBe(false);
+    });
   });
 });
 
@@ -266,11 +368,12 @@ describe("PROJECT_CONTEXT_SYSTEM_ADDENDUM", () => {
     expect(PROJECT_CONTEXT_SYSTEM_ADDENDUM.length).toBeGreaterThan(0);
   });
 
-  it("mentions all four context file names", () => {
+  it("mentions all five context file names", () => {
     expect(PROJECT_CONTEXT_SYSTEM_ADDENDUM).toContain("PROJECT.md");
     expect(PROJECT_CONTEXT_SYSTEM_ADDENDUM).toContain("REQUIREMENTS.md");
     expect(PROJECT_CONTEXT_SYSTEM_ADDENDUM).toContain("ROADMAP.md");
     expect(PROJECT_CONTEXT_SYSTEM_ADDENDUM).toContain("STATE.md");
+    expect(PROJECT_CONTEXT_SYSTEM_ADDENDUM).toContain("CODEBASE.md");
   });
 });
 

src/lib/stores/projectContext.ts

@@ -1,13 +1,14 @@
 import { writable } from "svelte/store";
 import { invoke } from "@tauri-apps/api/core";
 
-export type ProjectFile = "PROJECT" | "REQUIREMENTS" | "ROADMAP" | "STATE";
+export type ProjectFile = "PROJECT" | "REQUIREMENTS" | "ROADMAP" | "STATE" | "CODEBASE";
 
 export const PROJECT_FILE_NAMES: Record<ProjectFile, string> = {
   PROJECT: "PROJECT.md",
   REQUIREMENTS: "REQUIREMENTS.md",
   ROADMAP: "ROADMAP.md",
   STATE: "STATE.md",
+  CODEBASE: "CODEBASE.md",
 };
 
 export const PROJECT_TEMPLATES: Record<ProjectFile, string> = {
@@ -51,16 +52,25 @@ export const PROJECT_TEMPLATES: Record<ProjectFile, string> = {
 
 ## Next Steps
 `,
+  CODEBASE: "",
 };
 
 const PROJECT_FILES = Object.keys(PROJECT_FILE_NAMES) as ProjectFile[];
 
+export interface ProjectScan {
+  working_dir: string;
+  file_tree: string;
+  detected_type: string;
+  key_files: string[];
+}
+
 function createProjectContextStore() {
   const contents = writable<Record<ProjectFile, string | null>>({
     PROJECT: null,
     REQUIREMENTS: null,
     ROADMAP: null,
     STATE: null,
+    CODEBASE: null,
   });
 
   const isLoading = writable<Record<ProjectFile, boolean>>({
@@ -68,6 +78,7 @@ function createProjectContextStore() {
     REQUIREMENTS: false,
     ROADMAP: false,
     STATE: false,
+    CODEBASE: false,
   });
 
   const isSaving = writable<Record<ProjectFile, boolean>>({
@@ -75,9 +86,11 @@ function createProjectContextStore() {
     REQUIREMENTS: false,
     ROADMAP: false,
     STATE: false,
+    CODEBASE: false,
   });
 
   const activeFile = writable<ProjectFile>("PROJECT");
+  const isMappingCodebase = writable<boolean>(false);
 
   async function loadFile(file: ProjectFile, workingDirectory: string): Promise<void> {
     isLoading.update((state) => ({ ...state, [file]: true }));
@@ -123,19 +136,67 @@ function createProjectContextStore() {
     return PROJECT_TEMPLATES[file];
   }
 
+  async function mapCodebase(workingDirectory: string, conversationId: string): Promise<void> {
+    isMappingCodebase.set(true);
+    try {
+      const scan = await invoke<ProjectScan>("scan_project", {
+        workingDir: workingDirectory,
+      });
+
+      const prompt = buildCodebaseMapPrompt(scan);
+      await invoke("send_prompt", { conversationId, message: prompt });
+    } catch (error) {
+      console.error("Failed to map codebase:", error);
+      isMappingCodebase.set(false);
+    }
+  }
+
+  function finishMapping(): void {
+    isMappingCodebase.set(false);
+  }
+
   return {
     contents: { subscribe: contents.subscribe },
     isLoading: { subscribe: isLoading.subscribe },
     isSaving: { subscribe: isSaving.subscribe },
     activeFile: { subscribe: activeFile.subscribe },
+    isMappingCodebase: { subscribe: isMappingCodebase.subscribe },
     loadFile,
     saveFile,
     loadAll,
     setActiveFile,
     getTemplate,
+    mapCodebase,
+    finishMapping,
   };
 }
 
+function buildCodebaseMapPrompt(scan: ProjectScan): string {
+  const keyFilesSection =
+    scan.key_files.length > 0
+      ? `\n\nKey files detected:\n${scan.key_files.map((f) => `- ${f}`).join("\n")}`
+      : "";
+
+  return `Please analyse this codebase and generate a comprehensive \`CODEBASE.md\` file in the working directory (${scan.working_dir}).
+
+Project type detected: **${scan.detected_type}**${keyFilesSection}
+
+Directory structure:
+\`\`\`
+${scan.file_tree}
+\`\`\`
+
+The CODEBASE.md file should include:
+1. **Overview** — what the project does and its purpose
+2. **Architecture** — key directories, how the code is organised, and the overall structure
+3. **Key Components** — the most important files and modules, what they do, and how they interact
+4. **Data Flow** — how data moves through the system (if applicable)
+5. **Dependencies** — notable external dependencies and why they are used
+6. **Development Notes** — anything helpful for a developer new to the codebase
+
+Write the file concisely but thoroughly. Focus on information that helps a developer understand the codebase quickly. Use the actual file structure above to inform your analysis — read the key files as needed before writing.`;
+}
+
 export const projectContextStore = createProjectContextStore();
 
 // Signal store for injecting context into the active InputBar.
@@ -152,4 +213,5 @@ The following project context files may exist in your working directory. If they
 - PROJECT.md — project overview, goals, and architecture
 - REQUIREMENTS.md — functional and non-functional requirements
 - ROADMAP.md — current sprint, backlog, and completed work
-- STATE.md — current state, known issues, and next steps`;
+- STATE.md — current state, known issues, and next steps
+- CODEBASE.md — auto-generated codebase map and architecture overview`;