feat: **1. `src/main/db/schema.ts`** — add `settings` table … (+10 more)

- ✅ **1. `src/main/db/schema.ts`** — add `settings` table to `initSchema`
- ✅ **2. `src/main/db/settings.ts`** — create file with `getSetting`, `getSettings`, `setSetting`, `deleteSetting`
- ✅ **3. `src/main/claude/phases.ts`** — add `customSystemPrompt?` param to `getPhaseConfig`; add `getDefaultSystemPromptTemplate` export
- ✅ **4. `src/main/claude/index.ts`** — import `getSetting`; load custom prompt in `sendMessage`; pass to `getPhaseConfig`
- ✅ **5. `src/main/ipc/handlers.ts`** — import `settingsDb` + `getDefaultSystemPromptTemplate`; register `settings:get`, `settings:set`, `settings:delete`, `settings:getDefaultPrompts`
- ✅ **6. `src/main/preload.ts`** — add `getSettings`, `setSetting`, `deleteSetting`, `getDefaultSystemPrompts` to interface + api object
- ✅ **7. `renderer/src/styles/globals.css`** — append all new CSS rules
- ✅ **8. `renderer/src/components/settings/SystemPromptsSettings.tsx`** — create file (new directory)
- ✅ **9. `renderer/src/components/SettingsPage.tsx`** — create file
- ✅ **10. `renderer/src/components/Header.tsx`** — add `onOpenSettings` prop + ⚙ button
- ✅ **11. `renderer/src/App.tsx`** — add `showSettings` state; import + render `<SettingsPage>`; pass `onOpenSettings` to Header

2 files changed, 26 insertions, 3 deletions

diff --git a/src/main/claude/index.ts b/src/main/claude/index.ts
index 8971844..30a0f57 100644
--- a/src/main/claude/index.ts
+++ b/src/main/claude/index.ts
@@ -4,6 +4,7 @@ import { getPhaseConfig, getNextPhase, getArtifactFilename } from "./phases";
 import type { Phase, UserPermissionMode } from "./phases";
 import { getProject } from "../db/projects";
 import { updateSession } from "../db/sessions";
+import { getSetting } from "../db/settings";
 import { autoCommitTurn } from "../git";
 import fs from "node:fs";
 import path from "node:path";
@@ -44,10 +45,14 @@ export async function sendMessage({
   const sessionDir = getSessionDir(project.path, session.id);
   ensureDir(sessionDir);
 
+  // Load any custom system prompt for this phase (null → use default)
+  const customSystemPrompt = getSetting(`systemPrompt.${session.phase}`) ?? undefined;
+
   const phaseConfig = getPhaseConfig(
     session.phase as Phase,
     sessionDir,
-    session.permission_mode as UserPermissionMode
+    session.permission_mode as UserPermissionMode,
+    customSystemPrompt
   );
 
   const q = query({
diff --git a/src/main/claude/phases.ts b/src/main/claude/phases.ts
index 89e7c22..a1cbba1 100644
--- a/src/main/claude/phases.ts
+++ b/src/main/claude/phases.ts
@@ -160,11 +160,20 @@ When complete, summarize what was done and any follow-up tasks.`,
 export function getPhaseConfig(
   phase: Phase,
   artifactDir: string,
-  userPermissionMode?: UserPermissionMode
+  userPermissionMode?: UserPermissionMode,
+  customSystemPrompt?: string
 ): PhaseConfig {
   const template = phaseConfigTemplates[phase];
+
+  // If a custom prompt is provided, substitute the {{artifactDir}} placeholder.
+  // Otherwise use the default template function (existing behaviour).
+  const systemPrompt =
+    customSystemPrompt !== undefined
+      ? customSystemPrompt.replace(/\{\{artifactDir\}\}/g, artifactDir)
+      : template.systemPrompt(artifactDir);
+
   const config: PhaseConfig = {
-    systemPrompt: template.systemPrompt(artifactDir),
+    systemPrompt,
     tools: template.tools,
     permissionMode: template.permissionMode,
     initialMessage: template.initialMessage,
@@ -175,6 +184,15 @@ export function getPhaseConfig(
   return config;
 }
 
+/**
+ * Returns the default system prompt for a phase with "{{artifactDir}}" as a
+ * literal placeholder — the same format used when storing a custom prompt in
+ * the settings DB. Used by the Settings UI to display the default text.
+ */
+export function getDefaultSystemPromptTemplate(phase: Phase): string {
+  return phaseConfigTemplates[phase].systemPrompt("{{artifactDir}}");
+}
+
 export function getPhaseInitialMessage(phase: Phase): string {
   return phaseConfigTemplates[phase].initialMessage;
 }