diff --git a/src/ui/form-modal.ts b/src/ui/form-modal.ts
new file mode 100644
index 0000000..75dffa3
--- /dev/null
+++ b/src/ui/form-modal.ts
@@ -0,0 +1,188 @@
+import { App, Modal, TFile, Notice, FuzzySuggestModal } from 'obsidian';
+import { FormDefinition } from '../types';
+import { renderField, RenderedField, FieldValue } from './field-renderers';
+import { validateForm, ValidationError } from '../utils/validators';
+import { FormProcessor } from '../core/form-processor';
+
+// ---------------------------------------------------------------------------
+// FilePickerModal — FuzzySuggestModal for choosing a target file
+// ---------------------------------------------------------------------------
+
+export class FilePickerModal extends FuzzySuggestModal<TFile> {
+  private onChoose: (file: TFile) => void;
+
+  constructor(app: App, onChoose: (file: TFile) => void) {
+    super(app);
+    this.onChoose = onChoose;
+    this.setPlaceholder('Pick a file...');
+  }
+
+  getItems(): TFile[] {
+    return this.app.vault.getMarkdownFiles();
+  }
+
+  getItemText(item: TFile): string {
+    return item.path;
+  }
+
+  onChooseItem(item: TFile): void {
+    this.onChoose(item);
+  }
+}
+
+// ---------------------------------------------------------------------------
+// FormModal — renders a form and processes submission
+// ---------------------------------------------------------------------------
+
+export class FormModal extends Modal {
+  private form: FormDefinition;
+  private renderedFields: Map<string, RenderedField> = new Map();
+  private targetFile: TFile | undefined;
+
+  constructor(app: App, form: FormDefinition, targetFile?: TFile) {
+    super(app);
+    this.form = form;
+    this.targetFile = targetFile;
+  }
+
+  onOpen(): void {
+    const { contentEl } = this;
+    contentEl.addClass('ff-form-modal');
+    contentEl.empty();
+
+    // If update mode with prompt and no target file yet, open file picker first
+    if (
+      this.form.mode === 'update' &&
+      this.form.targetFile === 'prompt' &&
+      !this.targetFile
+    ) {
+      this.close();
+      new FilePickerModal(this.app, (file: TFile) => {
+        new FormModal(this.app, this.form, file).open();
+      }).open();
+      return;
+    }
+
+    // If update mode with active file, grab active file
+    if (
+      this.form.mode === 'update' &&
+      this.form.targetFile === 'active' &&
+      !this.targetFile
+    ) {
+      const active = this.app.workspace.getActiveFile();
+      if (!active) {
+        new Notice('No active file to update.');
+        this.close();
+        return;
+      }
+      this.targetFile = active;
+    }
+
+    this.renderForm();
+  }
+
+  private renderForm(): void {
+    const { contentEl } = this;
+
+    // Header
+    contentEl.createEl('h2', { text: this.form.name, cls: 'ff-form-title' });
+
+    // If updating a specific file, show which one
+    if (this.form.mode === 'update' && this.targetFile) {
+      contentEl.createDiv({
+        cls: 'ff-form-target',
+        text: `Updating: ${this.targetFile.path}`,
+      });
+    }
+
+    // Fields container
+    const fieldsEl = contentEl.createDiv({ cls: 'ff-fields' });
+
+    // Get existing frontmatter for pre-fill (update mode)
+    let existingFrontmatter: Record<string, unknown> = {};
+    if (this.form.mode === 'update' && this.targetFile) {
+      const cache = this.app.metadataCache.getFileCache(this.targetFile);
+      if (cache?.frontmatter) {
+        existingFrontmatter = { ...cache.frontmatter };
+      }
+    }
+
+    // Render each field
+    for (const field of this.form.fields) {
+      const initial = existingFrontmatter[field.id] as FieldValue | undefined;
+      const defaultVal = field.defaultValue as FieldValue | undefined;
+      const rendered = renderField(
+        this.app,
+        fieldsEl,
+        field,
+        initial ?? defaultVal,
+      );
+      this.renderedFields.set(field.id, rendered);
+    }
+
+    // Footer
+    const footerEl = contentEl.createDiv({ cls: 'ff-form-footer' });
+    const submitText =
+      this.form.mode === 'create' ? 'Create Note' : 'Update Frontmatter';
+    const submitBtn = footerEl.createEl('button', {
+      text: submitText,
+      cls: 'mod-cta ff-submit-btn',
+    });
+
+    submitBtn.addEventListener('click', () => {
+      this.handleSubmit();
+    });
+  }
+
+  private async handleSubmit(): Promise<void> {
+    // Collect values
+    const values: Record<string, unknown> = {};
+    for (const field of this.form.fields) {
+      const rendered = this.renderedFields.get(field.id);
+      if (rendered) {
+        values[field.id] = rendered.getValue();
+      }
+    }
+
+    // Clear previous errors
+    for (const rendered of this.renderedFields.values()) {
+      rendered.setError(null);
+    }
+
+    // Validate
+    const errors: ValidationError[] = validateForm(this.form.fields, values);
+    if (errors.length > 0) {
+      for (const err of errors) {
+        const rendered = this.renderedFields.get(err.fieldId);
+        if (rendered) {
+          rendered.setError(err.message);
+        }
+      }
+      // Shake the modal to indicate validation failure
+      this.contentEl.addClass('ff-shake');
+      setTimeout(() => this.contentEl.removeClass('ff-shake'), 400);
+      return;
+    }
+
+    // Process
+    try {
+      const processor = new FormProcessor(this.app);
+      const file = await processor.process(this.form, values, this.targetFile);
+      this.close();
+
+      // Open the created/updated file
+      if (this.form.mode === 'create') {
+        await this.app.workspace.getLeaf(false).openFile(file);
+      }
+    } catch (err) {
+      new Notice(
+        `Formfire error: ${err instanceof Error ? err.message : String(err)}`,
+      );
+    }
+  }
+
+  onClose(): void {
+    this.contentEl.empty();
+    this.renderedFields.clear();
+  }
+}