diff --git a/packages/prdy/package.json b/packages/prdy/package.json
index e0c9a7d..7280f81 100644
--- a/packages/prdy/package.json
+++ b/packages/prdy/package.json
@@ -15,7 +15,15 @@
     "typecheck": "tsc --noEmit",
     "test": "vitest run --passWithNoTests"
   },
+  "dependencies": {
+    "@clack/prompts": "^0.9.0",
+    "commander": "^12.0.0",
+    "js-yaml": "^4.1.0",
+    "zod": "^3.22.0"
+  },
   "devDependencies": {
+    "@types/js-yaml": "^4.0.9",
+    "@types/node": "^22.0.0",
     "typescript": "^5.8.0",
     "vitest": "^2.0.0"
   }
diff --git a/packages/prdy/src/cli.ts b/packages/prdy/src/cli.ts
new file mode 100644
index 0000000..1850e39
--- /dev/null
+++ b/packages/prdy/src/cli.ts
@@ -0,0 +1,100 @@
+import { Command } from 'commander';
+
+import { createPrd, listPrds, loadPrd } from './prd.js';
+import { runPrdWizard } from './wizard.js';
+
+interface InitCommandOptions {
+  readonly name: string;
+  readonly project: string;
+  readonly template?: 'software' | 'feature' | 'spike';
+}
+
+interface ListCommandOptions {
+  readonly project: string;
+}
+
+interface ShowCommandOptions {
+  readonly project: string;
+  readonly id?: string;
+}
+
+export function buildPrdyCli(): Command {
+  const program = new Command();
+  program.name('mosaic').description('Mosaic CLI').exitOverride();
+
+  const prdy = program.command('prdy').description('PRD wizard commands');
+
+  prdy
+    .command('init')
+    .description('Create a PRD document')
+    .requiredOption('--name <name>', 'PRD name')
+    .requiredOption('--project <path>', 'Project path')
+    .option('--template <template>', 'Template (software|feature|spike)')
+    .action(async (options: InitCommandOptions) => {
+      const doc = process.stdout.isTTY
+        ? await runPrdWizard({
+            name: options.name,
+            projectPath: options.project,
+            template: options.template,
+            interactive: true,
+          })
+        : await createPrd({
+            name: options.name,
+            projectPath: options.project,
+            template: options.template,
+            interactive: false,
+          });
+
+      console.log(
+        JSON.stringify(
+          {
+            ok: true,
+            id: doc.id,
+            title: doc.title,
+            status: doc.status,
+            projectPath: doc.projectPath,
+          },
+          null,
+          2,
+        ),
+      );
+    });
+
+  prdy
+    .command('list')
+    .description('List PRD documents for a project')
+    .requiredOption('--project <path>', 'Project path')
+    .action(async (options: ListCommandOptions) => {
+      const docs = await listPrds(options.project);
+      console.log(JSON.stringify(docs, null, 2));
+    });
+
+  prdy
+    .command('show')
+    .description('Show a PRD document')
+    .requiredOption('--project <path>', 'Project path')
+    .option('--id <id>', 'PRD document id')
+    .action(async (options: ShowCommandOptions) => {
+      if (options.id !== undefined) {
+        const docs = await listPrds(options.project);
+        const match = docs.find((doc) => doc.id === options.id);
+
+        if (match === undefined) {
+          throw new Error(`PRD id not found: ${options.id}`);
+        }
+
+        console.log(JSON.stringify(match, null, 2));
+        return;
+      }
+
+      const doc = await loadPrd(options.project);
+      console.log(JSON.stringify(doc, null, 2));
+    });
+
+  return program;
+}
+
+export async function runPrdyCli(argv: readonly string[] = process.argv): Promise<void> {
+  const program = buildPrdyCli();
+  await program.parseAsync(argv);
+}
diff --git a/packages/prdy/src/index.ts b/packages/prdy/src/index.ts
index 0c18d5d..5613c9b 100644
--- a/packages/prdy/src/index.ts
+++ b/packages/prdy/src/index.ts
@@ -1 +1,12 @@
-export const VERSION = '0.0.0';
+export { createPrd, loadPrd, savePrd, listPrds } from './prd.js';
+export { runPrdWizard } from './wizard.js';
+export { buildPrdyCli, runPrdyCli } from './cli.js';
+export { BUILTIN_PRD_TEMPLATES, resolveTemplate } from './templates.js';
+export type {
+  PrdStatus,
+  PrdTemplate,
+  PrdTemplateSection,
+  PrdSection,
+  PrdDocument,
+  CreatePrdOptions,
+} from './types.js';
diff --git a/packages/prdy/src/prd.ts b/packages/prdy/src/prd.ts
new file mode 100644
index 0000000..e6701d7
--- /dev/null
+++ b/packages/prdy/src/prd.ts
@@ -0,0 +1,199 @@
+import { type Dirent, promises as fs } from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
+import yaml from 'js-yaml';
+import { z } from 'zod';
+
+import { resolveTemplate } from './templates.js';
+import type { CreatePrdOptions, PrdDocument } from './types.js';
+
+const PRD_DIRECTORY = path.join('docs', 'prdy');
+const PRD_FILE_EXTENSIONS = new Set(['.yaml', '.yml']);
+
+const prdSectionSchema = z.object({
+  id: z.string().min(1),
+  title: z.string().min(1),
+  fields: z.record(z.string(), z.string()),
+});
+
+const prdDocumentSchema = z.object({
+  id: z.string().min(1),
+  title: z.string().min(1),
+  status: z.enum(['draft', 'review', 'approved', 'archived']),
+  projectPath: z.string().min(1),
+  template: z.string().min(1),
+  sections: z.array(prdSectionSchema),
+  createdAt: z.string().datetime(),
+  updatedAt: z.string().datetime(),
+});
+
+function expandHome(projectPath: string): string {
+  if (!projectPath.startsWith('~')) {
+    return projectPath;
+  }
+
+  if (projectPath === '~') {
+    return os.homedir();
+  }
+
+  if (projectPath.startsWith('~/')) {
+    return path.join(os.homedir(), projectPath.slice(2));
+  }
+
+  return projectPath;
+}
+
+function resolveProjectPath(projectPath: string): string {
+  return path.resolve(expandHome(projectPath));
+}
+
+function toSlug(value: string): string {
+  return value
+    .toLowerCase()
+    .replace(/[^a-z0-9]+/g, '-')
+    .replace(/^-+|-+$/g, '')
+    .replace(/-{2,}/g, '-');
+}
+
+function buildTimestamp(date: Date): { datePart: string; timePart: string } {
+  const iso = date.toISOString();
+  return {
+    datePart: iso.slice(0, 10).replace(/-/g, ''),
+    timePart: iso.slice(11, 19).replace(/:/g, ''),
+  };
+}
+
+function buildPrdId(name: string): string {
+  const slug = toSlug(name);
+  const { datePart, timePart } = buildTimestamp(new Date());
+  return `${slug || 'prd'}-${datePart}-${timePart}`;
+}
+
+function prdDirectory(projectPath: string): string {
+  return path.join(projectPath, PRD_DIRECTORY);
+}
+
+function prdFilePath(projectPath: string, id: string): string {
+  return path.join(prdDirectory(projectPath), `${id}.yaml`);
+}
+
+function isNodeErrorWithCode(error: unknown, code: string): boolean {
+  return (
+    typeof error === 'object' &&
+    error !== null &&
+    'code' in error &&
+    (error as { code?: string }).code === code
+  );
+}
+
+async function writeFileAtomic(filePath: string, content: string): Promise<void> {
+  const directory = path.dirname(filePath);
+  await fs.mkdir(directory, { recursive: true });
+
+  const tempPath = path.join(
+    directory,
+    `.${path.basename(filePath)}.tmp-${process.pid}-${Date.now()}-${Math.random()
+      .toString(16)
+      .slice(2)}`,
+  );
+
+  await fs.writeFile(tempPath, content, 'utf8');
+  await fs.rename(tempPath, filePath);
+}
+
+export async function createPrd(options: CreatePrdOptions): Promise<PrdDocument> {
+  const resolvedProjectPath = resolveProjectPath(options.projectPath);
+  const template = resolveTemplate(options.template);
+  const now = new Date().toISOString();
+
+  const document: PrdDocument = {
+    id: buildPrdId(options.name),
+    title: options.name.trim(),
+    status: 'draft',
+    projectPath: resolvedProjectPath,
+    template: template.id,
+    sections: template.sections.map((section) => ({
+      id: section.id,
+      title: section.title,
+      fields: Object.fromEntries(section.fields.map((field) => [field, ''])),
+    })),
+    createdAt: now,
+    updatedAt: now,
+  };
+
+  await savePrd(document);
+  return document;
+}
+
+export async function loadPrd(projectPath: string): Promise<PrdDocument> {
+  const documents = await listPrds(projectPath);
+  if (documents.length === 0) {
+    const resolvedProjectPath = resolveProjectPath(projectPath);
+    throw new Error(`No PRD documents found in ${prdDirectory(resolvedProjectPath)}`);
+  }
+
+  return documents[0]!;
+}
+
+export async function savePrd(doc: PrdDocument): Promise<void> {
+  const normalized = prdDocumentSchema.parse({
+    ...doc,
+    projectPath: resolveProjectPath(doc.projectPath),
+  });
+
+  const filePath = prdFilePath(normalized.projectPath, normalized.id);
+  const serialized = yaml.dump(normalized, {
+    noRefs: true,
+    sortKeys: false,
+    lineWidth: 120,
+  });
+
+  const content = serialized.endsWith('\n') ? serialized : `${serialized}\n`;
+  await writeFileAtomic(filePath, content);
+}
+
+export async function listPrds(projectPath: string): Promise<PrdDocument[]> {
+  const resolvedProjectPath = resolveProjectPath(projectPath);
+  const directory = prdDirectory(resolvedProjectPath);
+
+  let entries: Dirent[];
+  try {
+    entries = await fs.readdir(directory, { withFileTypes: true, encoding: 'utf8' });
+  } catch (error) {
+    if (isNodeErrorWithCode(error, 'ENOENT')) {
+      return [];
+    }
+
+    throw error;
+  }
+
+  const documents: PrdDocument[] = [];
+
+  for (const entry of entries) {
+    if (!entry.isFile()) {
+      continue;
+    }
+
+    const ext = path.extname(entry.name);
+    if (!PRD_FILE_EXTENSIONS.has(ext)) {
+      continue;
+    }
+
+    const filePath = path.join(directory, entry.name);
+    const raw = await fs.readFile(filePath, 'utf8');
+
+    let parsed: unknown;
+    try {
+      parsed = yaml.load(raw);
+    } catch (error) {
+      throw new Error(`Failed to parse PRD file ${filePath}: ${String(error)}`);
+    }
+
+    const document = prdDocumentSchema.parse(parsed);
+    documents.push(document);
+  }
+
+  documents.sort((left, right) => right.updatedAt.localeCompare(left.updatedAt));
+  return documents;
+}
diff --git a/packages/prdy/src/templates.ts b/packages/prdy/src/templates.ts
new file mode 100644
index 0000000..b3e733c
--- /dev/null
+++ b/packages/prdy/src/templates.ts
@@ -0,0 +1,93 @@
+import type { PrdTemplate } from './types.js';
+
+export const BUILTIN_PRD_TEMPLATES: Record<string, PrdTemplate> = {
+  software: {
+    id: 'software',
+    name: 'Software Project',
+    fields: ['owner', 'status', 'scopeVersion', 'successMetrics'],
+    sections: [
+      { id: 'introduction', title: 'Introduction', fields: ['context', 'objective'] },
+      { id: 'problem-statement', title: 'Problem Statement', fields: ['painPoints'] },
+      { id: 'scope-non-goals', title: 'Scope / Non-Goals', fields: ['inScope', 'outOfScope'] },
+      { id: 'user-stories', title: 'User Stories / Requirements', fields: ['stories'] },
+      { id: 'functional-requirements', title: 'Functional Requirements', fields: ['requirements'] },
+      {
+        id: 'non-functional-requirements',
+        title: 'Non-Functional Requirements',
+        fields: ['performance', 'reliability', 'security'],
+      },
+      { id: 'acceptance-criteria', title: 'Acceptance Criteria', fields: ['criteria'] },
+      {
+        id: 'technical-considerations',
+        title: 'Technical Considerations',
+        fields: ['constraints', 'dependencies'],
+      },
+      {
+        id: 'risks-open-questions',
+        title: 'Risks / Open Questions',
+        fields: ['risks', 'openQuestions'],
+      },
+      {
+        id: 'milestones-delivery',
+        title: 'Milestones / Delivery',
+        fields: ['milestones', 'timeline'],
+      },
+    ],
+  },
+  feature: {
+    id: 'feature',
+    name: 'Feature PRD',
+    fields: ['owner', 'status', 'releaseTarget'],
+    sections: [
+      { id: 'problem-statement', title: 'Problem Statement', fields: ['problem'] },
+      { id: 'goals', title: 'Goals', fields: ['goals'] },
+      { id: 'scope', title: 'Scope', fields: ['inScope', 'outOfScope'] },
+      { id: 'user-stories', title: 'User Stories', fields: ['stories'] },
+      { id: 'requirements', title: 'Requirements', fields: ['functional', 'nonFunctional'] },
+      { id: 'acceptance-criteria', title: 'Acceptance Criteria', fields: ['criteria'] },
+      {
+        id: 'technical-considerations',
+        title: 'Technical Considerations',
+        fields: ['constraints'],
+      },
+      {
+        id: 'risks-open-questions',
+        title: 'Risks / Open Questions',
+        fields: ['risks', 'questions'],
+      },
+      { id: 'milestones', title: 'Milestones', fields: ['milestones'] },
+      { id: 'success-metrics', title: 'Success Metrics / Testing', fields: ['metrics', 'testing'] },
+    ],
+  },
+  spike: {
+    id: 'spike',
+    name: 'Research Spike',
+    fields: ['owner', 'status', 'decisionDeadline'],
+    sections: [
+      { id: 'background', title: 'Background', fields: ['context'] },
+      { id: 'research-questions', title: 'Research Questions', fields: ['questions'] },
+      { id: 'constraints', title: 'Constraints', fields: ['constraints'] },
+      { id: 'options', title: 'Options Considered', fields: ['options'] },
+      { id: 'evaluation', title: 'Evaluation Criteria', fields: ['criteria'] },
+      { id: 'findings', title: 'Findings', fields: ['findings'] },
+      { id: 'recommendation', title: 'Recommendation', fields: ['recommendation'] },
+      { id: 'risks', title: 'Risks / Unknowns', fields: ['risks', 'unknowns'] },
+      { id: 'next-steps', title: 'Next Steps', fields: ['nextSteps'] },
+      { id: 'milestones', title: 'Milestones / Delivery', fields: ['milestones'] },
+    ],
+  },
+};
+
+export function resolveTemplate(templateName?: string): PrdTemplate {
+  const name =
+    templateName === undefined || templateName.trim().length === 0 ? 'software' : templateName;
+
+  const template = BUILTIN_PRD_TEMPLATES[name];
+  if (template === undefined) {
+    throw new Error(
+      `Unknown PRD template: ${name}. Expected one of: ${Object.keys(BUILTIN_PRD_TEMPLATES).join(', ')}`,
+    );
+  }
+
+  return template;
+}
diff --git a/packages/prdy/src/types.ts b/packages/prdy/src/types.ts
new file mode 100644
index 0000000..55c3b1a
--- /dev/null
+++ b/packages/prdy/src/types.ts
@@ -0,0 +1,38 @@
+export type PrdStatus = 'draft' | 'review' | 'approved' | 'archived';
+
+export interface PrdTemplateSection {
+  id: string;
+  title: string;
+  fields: string[];
+}
+
+export interface PrdTemplate {
+  id: string;
+  name: string;
+  sections: PrdTemplateSection[];
+  fields: string[];
+}
+
+export interface PrdSection {
+  id: string;
+  title: string;
+  fields: Record<string, string>;
+}
+
+export interface PrdDocument {
+  id: string;
+  title: string;
+  status: PrdStatus;
+  projectPath: string;
+  template: string;
+  sections: PrdSection[];
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface CreatePrdOptions {
+  name: string;
+  projectPath: string;
+  template?: string;
+  interactive?: boolean;
+}
diff --git a/packages/prdy/src/wizard.ts b/packages/prdy/src/wizard.ts
new file mode 100644
index 0000000..3016747
--- /dev/null
+++ b/packages/prdy/src/wizard.ts
@@ -0,0 +1,103 @@
+import path from 'node:path';
+
+import { cancel, intro, isCancel, outro, select, text } from '@clack/prompts';
+
+import { createPrd, savePrd } from './prd.js';
+import type { CreatePrdOptions, PrdDocument } from './types.js';
+
+interface WizardAnswers {
+  goals: string;
+  constraints: string;
+  milestones: string;
+}
+
+function updateSectionField(doc: PrdDocument, sectionKeyword: string, value: string): void {
+  const section = doc.sections.find((candidate) => candidate.id.includes(sectionKeyword));
+
+  if (section === undefined) {
+    return;
+  }
+
+  const fieldName =
+    Object.keys(section.fields).find((field) => field.toLowerCase().includes(sectionKeyword)) ??
+    Object.keys(section.fields)[0];
+
+  if (fieldName !== undefined) {
+    section.fields[fieldName] = value;
+  }
+}
+
+async function promptText(message: string, initialValue = ''): Promise<string> {
+  const response = await text({
+    message,
+    initialValue,
+  });
+
+  if (isCancel(response)) {
+    cancel('PRD wizard cancelled.');
+    throw new Error('PRD wizard cancelled');
+  }
+
+  return response.trim();
+}
+
+async function promptTemplate(template?: string): Promise<string> {
+  if (template !== undefined && template.trim().length > 0) {
+    return template;
+  }
+
+  const choice = await select({
+    message: 'PRD type',
+    options: [
+      { value: 'software', label: 'Software project' },
+      { value: 'feature', label: 'Feature' },
+      { value: 'spike', label: 'Research spike' },
+    ],
+  });
+
+  if (isCancel(choice)) {
+    cancel('PRD wizard cancelled.');
+    throw new Error('PRD wizard cancelled');
+  }
+
+  return choice;
+}
+
+function applyWizardAnswers(doc: PrdDocument, answers: WizardAnswers): PrdDocument {
+  updateSectionField(doc, 'goal', answers.goals);
+  updateSectionField(doc, 'constraint', answers.constraints);
+  updateSectionField(doc, 'milestone', answers.milestones);
+
+  doc.updatedAt = new Date().toISOString();
+  return doc;
+}
+
+export async function runPrdWizard(options: CreatePrdOptions): Promise<PrdDocument> {
+  intro('Mosaic PRD wizard');
+
+  const name =
+    options.name.trim().length > 0 ? options.name.trim() : await promptText('Project name');
+  const template = await promptTemplate(options.template);
+  const goals = await promptText('Primary goals');
+  const constraints = await promptText('Key constraints');
+  const milestones = await promptText('Planned milestones');
+
+  const doc = await createPrd({
+    ...options,
+    name,
+    template,
+    interactive: true,
+  });
+
+  const updated = applyWizardAnswers(doc, {
+    goals,
+    constraints,
+    milestones,
+  });
+
+  await savePrd(updated);
+
+  outro(`PRD created: ${path.join(updated.projectPath, 'docs', 'prdy', `${updated.id}.yaml`)}`);
+
+  return updated;
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 1dc3b20..690710c 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -46,10 +46,10 @@ importers:
         version: 13.0.2
       '@mariozechner/pi-ai':
         specifier: ~0.57.1
-        version: 0.57.1(ws@8.19.0)(zod@3.25.76)
+        version: 0.57.1(ws@8.19.0)(zod@4.3.6)
       '@mariozechner/pi-coding-agent':
         specifier: ~0.57.1
-        version: 0.57.1(ws@8.19.0)(zod@3.25.76)
+        version: 0.57.1(ws@8.19.0)(zod@4.3.6)
       '@mosaic/auth':
         specifier: workspace:^
         version: link:../../packages/auth
@@ -5203,11 +5203,11 @@ snapshots:
 
   '@alloc/quick-lru@5.2.0': {}
 
-  '@anthropic-ai/sdk@0.73.0(zod@3.25.76)':
+  '@anthropic-ai/sdk@0.73.0(zod@4.3.6)':
     dependencies:
       json-schema-to-ts: 3.1.1
     optionalDependencies:
-      zod: 3.25.76
+      zod: 4.3.6
 
   '@aws-crypto/crc32@5.2.0':
     dependencies:
@@ -6305,9 +6305,9 @@ snapshots:
       std-env: 3.10.0
       yoctocolors: 2.1.2
 
-  '@mariozechner/pi-agent-core@0.57.1(ws@8.19.0)(zod@3.25.76)':
+  '@mariozechner/pi-agent-core@0.57.1(ws@8.19.0)(zod@4.3.6)':
     dependencies:
-      '@mariozechner/pi-ai': 0.57.1(ws@8.19.0)(zod@3.25.76)
+      '@mariozechner/pi-ai': 0.57.1(ws@8.19.0)(zod@4.3.6)
     transitivePeerDependencies:
       - '@modelcontextprotocol/sdk'
       - aws-crt
@@ -6317,9 +6317,9 @@ snapshots:
       - ws
       - zod
 
-  '@mariozechner/pi-ai@0.57.1(ws@8.19.0)(zod@3.25.76)':
+  '@mariozechner/pi-ai@0.57.1(ws@8.19.0)(zod@4.3.6)':
     dependencies:
-      '@anthropic-ai/sdk': 0.73.0(zod@3.25.76)
+      '@anthropic-ai/sdk': 0.73.0(zod@4.3.6)
       '@aws-sdk/client-bedrock-runtime': 3.1008.0
       '@google/genai': 1.45.0
       '@mistralai/mistralai': 1.14.1
@@ -6327,11 +6327,11 @@ snapshots:
       ajv: 8.18.0
       ajv-formats: 3.0.1(ajv@8.18.0)
       chalk: 5.6.2
-      openai: 6.26.0(ws@8.19.0)(zod@3.25.76)
+      openai: 6.26.0(ws@8.19.0)(zod@4.3.6)
       partial-json: 0.1.7
       proxy-agent: 6.5.0
       undici: 7.24.0
-      zod-to-json-schema: 3.25.1(zod@3.25.76)
+      zod-to-json-schema: 3.25.1(zod@4.3.6)
     transitivePeerDependencies:
       - '@modelcontextprotocol/sdk'
       - aws-crt
@@ -6341,11 +6341,11 @@ snapshots:
       - ws
       - zod
 
-  '@mariozechner/pi-coding-agent@0.57.1(ws@8.19.0)(zod@3.25.76)':
+  '@mariozechner/pi-coding-agent@0.57.1(ws@8.19.0)(zod@4.3.6)':
     dependencies:
       '@mariozechner/jiti': 2.6.5
-      '@mariozechner/pi-agent-core': 0.57.1(ws@8.19.0)(zod@3.25.76)
-      '@mariozechner/pi-ai': 0.57.1(ws@8.19.0)(zod@3.25.76)
+      '@mariozechner/pi-agent-core': 0.57.1(ws@8.19.0)(zod@4.3.6)
+      '@mariozechner/pi-ai': 0.57.1(ws@8.19.0)(zod@4.3.6)
       '@mariozechner/pi-tui': 0.57.1
       '@silvia-odwyer/photon-node': 0.3.4
       chalk: 5.6.2
@@ -9245,10 +9245,10 @@ snapshots:
     dependencies:
       mimic-function: 5.0.1
 
-  openai@6.26.0(ws@8.19.0)(zod@3.25.76):
+  openai@6.26.0(ws@8.19.0)(zod@4.3.6):
     optionalDependencies:
       ws: 8.19.0
-      zod: 3.25.76
+      zod: 4.3.6
 
   optionator@0.9.4:
     dependencies:
@@ -10087,6 +10087,10 @@ snapshots:
     dependencies:
       zod: 3.25.76
 
+  zod-to-json-schema@3.25.1(zod@4.3.6):
+    dependencies:
+      zod: 4.3.6
+
   zod@3.25.76: {}
 
   zod@4.3.6: {}