diff --git a/frontend/src/lib/components/DdlMigrationGuard.svelte b/frontend/src/lib/components/DdlMigrationGuard.svelte
new file mode 100644
index 0000000000..689f6baf1d
--- /dev/null
+++ b/frontend/src/lib/components/DdlMigrationGuard.svelte
@@ -0,0 +1,118 @@
+<script lang="ts">
+	import { Button } from './common'
+	import Modal2 from './common/modal/Modal2.svelte'
+	import NewDataTableMigrationModal from './workspaceSettings/NewDataTableMigrationModal.svelte'
+	import { splitSqlStatements, isDdlStatement } from './sqlDdl'
+
+	let { workspace, datatable }: { workspace: string; datatable: string } = $props()
+
+	type Choice = 'run' | 'migrate' | 'cancel'
+
+	let promptStatement = $state<string | undefined>(undefined)
+	let promptOpen = $state(false)
+	let resolvePrompt: ((choice: Choice) => void) | undefined = undefined
+	let resolveMigrationClosed: (() => void) | undefined = undefined
+	let newMigrationModal = $state<NewDataTableMigrationModal | undefined>(undefined)
+
+	function finishPrompt(choice: Choice) {
+		const r = resolvePrompt
+		resolvePrompt = undefined
+		promptOpen = false
+		promptStatement = undefined
+		r?.(choice)
+	}
+
+	// Closing the modal (X / escape) while a prompt is pending counts as cancel.
+	$effect(() => {
+		if (!promptOpen && resolvePrompt) {
+			finishPrompt('cancel')
+		}
+	})
+
+	function promptDdl(statement: string): Promise<Choice> {
+		return new Promise((resolve) => {
+			resolvePrompt = resolve
+			promptStatement = statement
+			promptOpen = true
+		})
+	}
+
+	function handleMigrationClosed() {
+		const r = resolveMigrationClosed
+		resolveMigrationClosed = undefined
+		r?.()
+	}
+
+	// Open the prefilled new-migration modal and resolve once it closes (whether
+	// the migration was created or the user cancelled).
+	function openMigrationModal(statement: string): Promise<void> {
+		return new Promise((resolve) => {
+			resolveMigrationClosed = resolve
+			newMigrationModal?.open({ codeUp: statement })
+		})
+	}
+
+	/**
+	 * Inspect `code` for DDL statements. For each one, prompt the user to run it
+	 * anyway or turn it into a migration (prompts shown one at a time). Returns
+	 * whether to proceed and the code to run (with migrated statements stripped).
+	 */
+	export async function guard(code: string): Promise<{ proceed: boolean; code: string }> {
+		const statements = splitSqlStatements(code)
+		if (!statements.some((s) => isDdlStatement(s))) {
+			return { proceed: true, code }
+		}
+
+		const kept: string[] = []
+		for (const statement of statements) {
+			if (!isDdlStatement(statement)) {
+				kept.push(statement)
+				continue
+			}
+			const choice = await promptDdl(statement)
+			if (choice === 'cancel') {
+				return { proceed: false, code }
+			}
+			if (choice === 'run') {
+				kept.push(statement)
+				continue
+			}
+			// migrate: strip from the executed code and open the prefilled modal
+			await openMigrationModal(statement)
+		}
+
+		return { proceed: true, code: kept.join(';\n') }
+	}
+</script>
+
+<Modal2
+	title="Schema change detected"
+	fixedWidth="md"
+	fixedHeight="adaptive"
+	bind:isOpen={promptOpen}
+	closeOnOutsideClick={false}
+>
+	<div class="flex flex-col gap-3 w-full">
+		<p class="text-sm text-secondary">
+			This looks like a schema-changing (DDL) statement. Schema changes are best tracked as
+			migrations rather than run ad-hoc. Create a migration for it instead?
+		</p>
+		<pre
+			class="text-xs whitespace-pre-wrap font-mono bg-surface-secondary rounded p-3 max-h-48 overflow-auto"
+			>{promptStatement ?? ''}</pre
+		>
+		<div class="flex justify-end gap-2 pt-2">
+			<Button variant="default" size="sm" on:click={() => finishPrompt('run')}>Run anyway</Button>
+			<Button variant="accent" size="sm" on:click={() => finishPrompt('migrate')}>
+				Create a migration
+			</Button>
+		</div>
+	</div>
+</Modal2>
+
+<NewDataTableMigrationModal
+	bind:this={newMigrationModal}
+	{workspace}
+	{datatable}
+	onClose={handleMigrationClosed}
+/>
diff --git a/frontend/src/lib/components/Editor.svelte b/frontend/src/lib/components/Editor.svelte
index 476869900d..d0cd91e2fd 100644
--- a/frontend/src/lib/components/Editor.svelte
+++ b/frontend/src/lib/components/Editor.svelte
@@ -43,6 +43,7 @@
 	import { editorFontSize } from '$lib/editorFontSize.svelte'
 	import { createHash as randomHash } from '$lib/editorLangUtils'
 	import { workspaceStore } from '$lib/stores'
+	import DdlMigrationGuard from './DdlMigrationGuard.svelte'
 	import {
 		type Preview,
 		ResourceService,
@@ -213,6 +214,26 @@
 
 	let lang = $state(scriptLangToEditorLang(untrack(() => scriptLang)))
 
+	// On a postgres script targeting a datatable, DDL statements are intercepted
+	// on run (cmd+enter) and offered as migrations instead.
+	let datatableForMigrations = $derived(
+		scriptLang === 'postgresql' &&
+			typeof args?.database === 'string' &&
+			args.database.startsWith('datatable://')
+			? args.database.slice('datatable://'.length).split('/')[0]
+			: undefined
+	)
+	let ddlGuard = $state<DdlMigrationGuard | undefined>(undefined)
+
+	async function runCmdEnterWithDdlGuard() {
+		if (datatableForMigrations && ddlGuard) {
+			const res = await ddlGuard.guard(getCode())
+			if (!res.proceed) return
+			if (res.code !== getCode()) setCode(res.code)
+		}
+		cmdEnterAction?.()
+	}
+
 	let filePath = $state(computePath(untrack(() => path)))
 
 	let initialPath: string | undefined = $state(untrack(() => path))
@@ -1539,7 +1560,8 @@
 
 			editor?.addCommand(KeyMod.CtrlCmd | KeyCode.Enter, function () {
 				updateCode()
-				shouldBindKey && cmdEnterAction && cmdEnterAction()
+				if (!shouldBindKey || !cmdEnterAction) return
+				void runCmdEnterWithDdlGuard()
 			})
 
 			editor?.addCommand(KeyMod.CtrlCmd | KeyMod.Shift | KeyCode.Digit7, function () {
@@ -2067,6 +2089,13 @@
 
 <svelte:window onkeydown={onKeyDown} />
 <EditorTheme />
+{#if datatableForMigrations && $workspaceStore}
+	<DdlMigrationGuard
+		bind:this={ddlGuard}
+		workspace={$workspaceStore}
+		datatable={datatableForMigrations}
+	/>
+{/if}
 {#if !editor}
 	<div class="inset-0 absolute overflow-clip">
 		<FakeMonacoPlaceHolder {code} lineNumbersWidth={51} />
diff --git a/frontend/src/lib/components/SqlRepl.svelte b/frontend/src/lib/components/SqlRepl.svelte
index 661b0ccd2c..60b5ec253a 100644
--- a/frontend/src/lib/components/SqlRepl.svelte
+++ b/frontend/src/lib/components/SqlRepl.svelte
@@ -1,49 +1,3 @@
-<script module lang="ts">
-	// code may be composed of many sql statements separated by ';'
-	// this function splits them while taking into account that ';' may not
-	// be the end of a statement (string or escaped)
-	function splitSqlStatements(code: string) {
-		const statements: string[] = []
-		let currentStatement = ''
-		let inSingleQuote = false
-		let inDoubleQuote = false
-		let inBacktick = false
-
-		for (let i = 0; i < code.length; i++) {
-			const char = code[i]
-			const prevChar = i > 0 ? code[i - 1] : null
-
-			if (char === "'" && !inDoubleQuote && !inBacktick && prevChar !== '\\') {
-				inSingleQuote = !inSingleQuote
-			} else if (char === '"' && !inSingleQuote && !inBacktick && prevChar !== '\\') {
-				inDoubleQuote = !inDoubleQuote
-			} else if (char === '`' && !inSingleQuote && !inDoubleQuote && prevChar !== '\\') {
-				inBacktick = !inBacktick
-			}
-
-			if (char === ';' && !inSingleQuote && !inDoubleQuote && !inBacktick) {
-				statements.push(currentStatement.trim())
-				currentStatement = ''
-			} else {
-				currentStatement += char
-			}
-		}
-
-		if (currentStatement.trim()) {
-			statements.push(currentStatement.trim())
-		}
-
-		return statements
-	}
-
-	function pruneComments(code: string) {
-		return code
-			.replace(/--.*?(\r?\n|$)/g, '')
-			.replace(/\/\*[\s\S]*?\*\//g, '')
-			.trim()
-	}
-</script>
-
 <script lang="ts">
 	import { CornerDownLeft, Loader2 } from 'lucide-svelte'
 	import Button from './common/button/Button.svelte'
@@ -57,6 +11,8 @@
 	import { getDatabaseArg, getDbType } from './dbOps'
 	import type { DbInput } from './dbTypes'
 	import { wrapDucklakeQuery } from './ducklake'
+	import { splitSqlStatements, pruneComments } from './sqlDdl'
+	import DdlMigrationGuard from './DdlMigrationGuard.svelte'
 
 	type Props = {
 		input: DbInput
@@ -66,6 +22,15 @@
 	let { input, onData, placeholderTableName }: Props = $props()
 	let dbType = $derived(getDbType(input))
 
+	// A datatable REPL targets `datatable://<name>`; surface DDL statements as
+	// migration prompts instead of running them ad-hoc.
+	let datatableName = $derived(
+		input.type === 'database' && input.resourcePath.startsWith('datatable://')
+			? input.resourcePath.slice('datatable://'.length).split('/')[0]
+			: undefined
+	)
+	let ddlGuard = $state<DdlMigrationGuard | undefined>(undefined)
+
 	const DEFAULT_SQL = 'SELECT * FROM _'
 	let code = $state(DEFAULT_SQL)
 	$effect(() => {
@@ -81,6 +46,16 @@
 	async function run({ doPostgresRowToJsonFix }: { doPostgresRowToJsonFix?: boolean } = {}) {
 		if (isRunning || !$workspaceStore) return
 		const READ_OPS = ['SELECT', 'WITH', 'SHOW', 'EXPLAIN', 'DESCRIBE']
+
+		// On a datatable, intercept DDL statements and offer to make them
+		// migrations; the user may strip some, leaving the rest to run.
+		if (datatableName && ddlGuard && !doPostgresRowToJsonFix) {
+			const res = await ddlGuard.guard(code)
+			if (!res.proceed) return
+			if (res.code !== code) code = res.code
+			if (pruneComments(code).trim() === '') return
+		}
+
 		isRunning = true
 		try {
 			const statements = splitSqlStatements(pruneComments(code))
@@ -197,3 +172,7 @@
 		/>
 	</Pane>
 </Splitpanes>
+
+{#if datatableName && $workspaceStore}
+	<DdlMigrationGuard bind:this={ddlGuard} workspace={$workspaceStore} datatable={datatableName} />
+{/if}
diff --git a/frontend/src/lib/components/sqlDdl.ts b/frontend/src/lib/components/sqlDdl.ts
new file mode 100644
index 0000000000..46a5aa131e
--- /dev/null
+++ b/frontend/src/lib/components/sqlDdl.ts
@@ -0,0 +1,57 @@
+// Heuristics for splitting a SQL script into individual statements and
+// detecting Data Definition Language (DDL) statements. Shared by the datatable
+// SQL REPL and the postgres editor to steer schema changes into migrations.
+
+// code may be composed of many sql statements separated by ';'
+// this splits them while taking into account that ';' may appear inside a
+// string or quoted identifier and is then not the end of a statement.
+export function splitSqlStatements(code: string): string[] {
+	const statements: string[] = []
+	let currentStatement = ''
+	let inSingleQuote = false
+	let inDoubleQuote = false
+	let inBacktick = false
+
+	for (let i = 0; i < code.length; i++) {
+		const char = code[i]
+		const prevChar = i > 0 ? code[i - 1] : null
+
+		if (char === "'" && !inDoubleQuote && !inBacktick && prevChar !== '\\') {
+			inSingleQuote = !inSingleQuote
+		} else if (char === '"' && !inSingleQuote && !inBacktick && prevChar !== '\\') {
+			inDoubleQuote = !inDoubleQuote
+		} else if (char === '`' && !inSingleQuote && !inDoubleQuote && prevChar !== '\\') {
+			inBacktick = !inBacktick
+		}
+
+		if (char === ';' && !inSingleQuote && !inDoubleQuote && !inBacktick) {
+			statements.push(currentStatement.trim())
+			currentStatement = ''
+		} else {
+			currentStatement += char
+		}
+	}
+
+	if (currentStatement.trim()) {
+		statements.push(currentStatement.trim())
+	}
+
+	return statements.filter((s) => s.length > 0)
+}
+
+export function pruneComments(code: string): string {
+	return code
+		.replace(/--.*?(\r?\n|$)/g, '')
+		.replace(/\/\*[\s\S]*?\*\//g, '')
+		.trim()
+}
+
+// Schema-changing keywords. GRANT/REVOKE are included since permission changes
+// also belong in migrations rather than ad-hoc execution.
+const DDL_KEYWORDS = ['CREATE', 'ALTER', 'DROP', 'TRUNCATE', 'RENAME', 'COMMENT', 'GRANT', 'REVOKE']
+
+/** Heuristic: a statement is DDL if its first keyword is schema-changing. */
+export function isDdlStatement(statement: string): boolean {
+	const firstWord = pruneComments(statement).trim().split(/\s+/)[0]?.toUpperCase()
+	return !!firstWord && DDL_KEYWORDS.includes(firstWord)
+}
diff --git a/frontend/src/lib/components/workspaceSettings/DataTableMigrationsButton.svelte b/frontend/src/lib/components/workspaceSettings/DataTableMigrationsButton.svelte
index 5a68d43336..c2bfefb66c 100644
--- a/frontend/src/lib/components/workspaceSettings/DataTableMigrationsButton.svelte
+++ b/frontend/src/lib/components/workspaceSettings/DataTableMigrationsButton.svelte
@@ -1,17 +1,12 @@
 <script lang="ts">
 	import { Button } from '../common'
 	import Modal2 from '../common/modal/Modal2.svelte'
-	import Tabs from '../common/tabs/Tabs.svelte'
-	import Tab from '../common/tabs/Tab.svelte'
-	import TabContent from '../common/tabs/TabContent.svelte'
-	import Toggle from '../Toggle.svelte'
-	import TextInput from '../text_input/TextInput.svelte'
-	import SimpleEditor from '../SimpleEditor.svelte'
 	import ConfirmationModal from '../common/confirmationModal/ConfirmationModal.svelte'
 	import { createAsyncConfirmationModal } from '../common/confirmationModal/asyncConfirmationModal.svelte'
 	import { ChevronDown, Play, Trash2, Plus, Undo2, Loader2 } from 'lucide-svelte'
 	import { WorkspaceService, type DatatableMigrationWithStatus } from '$lib/gen'
 	import { sendUserToast } from '$lib/toast'
+	import NewDataTableMigrationModal from './NewDataTableMigrationModal.svelte'
 
 	let {
 		workspace,
@@ -25,13 +20,7 @@
 	let loading = $state(false)
 	let busy = $state(false)
 
-	let newOpen = $state(false)
-	let newTab = $state('up')
-	let newName = $state('')
-	let newCodeUp = $state('')
-	let enableDown = $state(false)
-	let newCodeDown = $state('')
-	let creating = $state(false)
+	let newMigrationModal = $state<NewDataTableMigrationModal | undefined>(undefined)
 
 	const confirmationModal = createAsyncConfirmationModal()
 
@@ -128,52 +117,6 @@
 		}
 	}
 
-	function resetNew() {
-		newName = ''
-		newCodeUp = ''
-		newCodeDown = ''
-		enableDown = false
-		newTab = 'up'
-	}
-
-	function openNew() {
-		resetNew()
-		newOpen = true
-	}
-
-	async function create(run: boolean) {
-		if (newName.trim() === '') {
-			sendUserToast('Migration name is required', true)
-			return
-		}
-		creating = true
-		try {
-			const created = await WorkspaceService.createDatatableMigration({
-				workspace,
-				datatableName: datatable,
-				requestBody: {
-					name: newName.trim(),
-					code_up: newCodeUp,
-					code_down: enableDown ? newCodeDown : undefined
-				}
-			})
-			if (run) {
-				await WorkspaceService.runDatatableMigrations({
-					workspace,
-					datatableName: datatable,
-					upTo: created.timestamp
-				})
-			}
-			newOpen = false
-			sendUserToast(run ? 'Migration created and run' : 'Migration created')
-			await loadMigrations()
-		} catch (e) {
-			sendUserToast(`Failed to create migration: ${e}`, true)
-		} finally {
-			creating = false
-		}
-	}
-
 	const statusColor = {
 		ran: 'bg-green-500',
 		not_run: 'bg-orange-500',
@@ -245,7 +188,12 @@
 			{/if}
 		</div>
 		<div class="flex justify-between gap-2 pt-2">
-			<Button variant="default" size="sm" startIcon={{ icon: Plus }} on:click={openNew}>New</Button>
+			<Button
+				variant="default"
+				size="sm"
+				startIcon={{ icon: Plus }}
+				on:click={() => newMigrationModal?.open()}>New</Button
+			>
 			<div class="flex gap-2">
 				<Button
 					variant="default"
@@ -270,52 +218,11 @@
 	</div>
 </Modal2>
 
-<Modal2 bind:isOpen={newOpen} title="New migration" fixedWidth="md" fixedHeight="lg">
-	<div class="flex flex-col gap-3 w-full grow min-h-0">
-		<TextInput
-			bind:value={newName}
-			inputProps={{ placeholder: 'Migration name (e.g. add_index_to_customers)' }}
-		/>
-		<Tabs bind:selected={newTab} class="grow min-h-0">
-			<Tab value="up" label="Up" />
-			<Tab value="down" label="Down" />
-			{#snippet content()}
-				<TabContent value="up" class="h-80">
-					<SimpleEditor class="h-full" lang="sql" bind:code={newCodeUp} />
-				</TabContent>
-				<TabContent value="down" class="h-80">
-					<div class="flex flex-col gap-2 h-full">
-						<Toggle
-							bind:checked={enableDown}
-							options={{ right: 'Enable down migration' }}
-							size="sm"
-						/>
-						{#if enableDown}
-							<div class="grow min-h-0">
-								<SimpleEditor class="h-full" lang="sql" bind:code={newCodeDown} />
-							</div>
-						{/if}
-					</div>
-				</TabContent>
-			{/snippet}
-		</Tabs>
-		<div class="flex justify-end pt-2">
-			<Button
-				variant="accent"
-				size="sm"
-				disabled={creating}
-				on:click={() => create(true)}
-				dropdownItems={[
-					{
-						label: 'Create without running',
-						onClick: () => create(false)
-					}
-				]}
-			>
-				Create and run
-			</Button>
-		</div>
-	</div>
-</Modal2>
+<NewDataTableMigrationModal
+	bind:this={newMigrationModal}
+	{workspace}
+	{datatable}
+	onCreated={loadMigrations}
+/>
 
 <ConfirmationModal {...confirmationModal.props} />
diff --git a/frontend/src/lib/components/workspaceSettings/NewDataTableMigrationModal.svelte b/frontend/src/lib/components/workspaceSettings/NewDataTableMigrationModal.svelte
new file mode 100644
index 0000000000..193d1a0e0d
--- /dev/null
+++ b/frontend/src/lib/components/workspaceSettings/NewDataTableMigrationModal.svelte
@@ -0,0 +1,129 @@
+<script lang="ts">
+	import { Button } from '../common'
+	import Modal2 from '../common/modal/Modal2.svelte'
+	import Tabs from '../common/tabs/Tabs.svelte'
+	import Tab from '../common/tabs/Tab.svelte'
+	import TabContent from '../common/tabs/TabContent.svelte'
+	import Toggle from '../Toggle.svelte'
+	import TextInput from '../text_input/TextInput.svelte'
+	import SimpleEditor from '../SimpleEditor.svelte'
+	import { WorkspaceService } from '$lib/gen'
+	import { sendUserToast } from '$lib/toast'
+
+	let {
+		workspace,
+		datatable,
+		onCreated,
+		onClose
+	}: {
+		workspace: string
+		datatable: string
+		onCreated?: () => void
+		onClose?: () => void
+	} = $props()
+
+	let isOpen = $state(false)
+	// Notify the parent whenever the modal closes (after a create or a cancel),
+	// so callers that sequence modals (e.g. the DDL guard) can advance.
+	let prevOpen = false
+	$effect(() => {
+		if (prevOpen && !isOpen) onClose?.()
+		prevOpen = isOpen
+	})
+	let tab = $state('up')
+	let name = $state('')
+	let codeUp = $state('')
+	let enableDown = $state(false)
+	let codeDown = $state('')
+	let creating = $state(false)
+
+	export function open(prefill?: { name?: string; codeUp?: string; codeDown?: string }) {
+		name = prefill?.name ?? ''
+		codeUp = prefill?.codeUp ?? ''
+		codeDown = prefill?.codeDown ?? ''
+		enableDown = (prefill?.codeDown ?? '') !== ''
+		tab = 'up'
+		isOpen = true
+	}
+
+	async function create(run: boolean) {
+		if (name.trim() === '') {
+			sendUserToast('Migration name is required', true)
+			return
+		}
+		creating = true
+		try {
+			const created = await WorkspaceService.createDatatableMigration({
+				workspace,
+				datatableName: datatable,
+				requestBody: {
+					name: name.trim(),
+					code_up: codeUp,
+					code_down: enableDown ? codeDown : undefined
+				}
+			})
+			if (run) {
+				await WorkspaceService.runDatatableMigrations({
+					workspace,
+					datatableName: datatable,
+					upTo: created.timestamp
+				})
+			}
+			isOpen = false
+			sendUserToast(run ? 'Migration created and run' : 'Migration created')
+			onCreated?.()
+		} catch (e) {
+			sendUserToast(`Failed to create migration: ${e}`, true)
+		} finally {
+			creating = false
+		}
+	}
+</script>
+
+<Modal2 bind:isOpen title="New migration — {datatable}" fixedWidth="md" fixedHeight="lg">
+	<div class="flex flex-col gap-3 w-full grow min-h-0">
+		<TextInput
+			bind:value={name}
+			inputProps={{ placeholder: 'Migration name (e.g. add_index_to_customers)' }}
+		/>
+		<Tabs bind:selected={tab} class="grow min-h-0">
+			<Tab value="up" label="Up" />
+			<Tab value="down" label="Down" />
+			{#snippet content()}
+				<TabContent value="up" class="h-80">
+					<SimpleEditor class="h-full" lang="sql" bind:code={codeUp} />
+				</TabContent>
+				<TabContent value="down" class="h-80">
+					<div class="flex flex-col gap-2 h-full">
+						<Toggle
+							bind:checked={enableDown}
+							options={{ right: 'Enable down migration' }}
+							size="sm"
+						/>
+						{#if enableDown}
+							<div class="grow min-h-0">
+								<SimpleEditor class="h-full" lang="sql" bind:code={codeDown} />
+							</div>
+						{/if}
+					</div>
+				</TabContent>
+			{/snippet}
+		</Tabs>
+		<div class="flex justify-end pt-2">
+			<Button
+				variant="accent"
+				size="sm"
+				disabled={creating}
+				on:click={() => create(true)}
+				dropdownItems={[
+					{
+						label: 'Create without running',
+						onClick: () => create(false)
+					}
+				]}
+			>
+				Create and run
+			</Button>
+		</div>
+	</div>
+</Modal2>