diff --git a/packages/coding-agent/src/tui/tool-execution.ts b/packages/coding-agent/src/tui/tool-execution.ts
index 21fdf51b..1ddf349b 100644
--- a/packages/coding-agent/src/tui/tool-execution.ts
+++ b/packages/coding-agent/src/tui/tool-execution.ts
@@ -13,6 +13,13 @@ function shortenPath(path: string): string {
 	return path;
 }
 
+/**
+ * Replace tabs with spaces for consistent rendering
+ */
+function replaceTabs(text: string): string {
+	return text.replace(/\t/g, "   ");
+}
+
 /**
  * Generate a unified diff between old and new strings with line numbers
  */
@@ -120,7 +127,7 @@ export class ToolExecutionComponent extends Container {
 				const displayLines = lines.slice(0, maxLines);
 				const remaining = lines.length - maxLines;
 
-				text += "\n\n" + displayLines.map((line: string) => chalk.dim(line)).join("\n");
+				text += "\n\n" + displayLines.map((line: string) => chalk.dim(replaceTabs(line))).join("\n");
 				if (remaining > 0) {
 					text += chalk.dim(`\n... (${remaining} more lines)`);
 				}
@@ -142,7 +149,7 @@ export class ToolExecutionComponent extends Container {
 				const displayLines = lines.slice(0, maxLines);
 				const remaining = lines.length - maxLines;
 
-				text += "\n\n" + displayLines.map((line: string) => chalk.dim(line)).join("\n");
+				text += "\n\n" + displayLines.map((line: string) => chalk.dim(replaceTabs(line))).join("\n");
 				if (remaining > 0) {
 					text += chalk.dim(`\n... (${remaining} more lines)`);
 				}
diff --git a/packages/coding-agent/test.json b/packages/coding-agent/test.json
new file mode 100644
index 00000000..f8001741
--- /dev/null
+++ b/packages/coding-agent/test.json
@@ -0,0 +1,28 @@
+{
+	"name": "test-file",
+	"version": "1.0.0",
+	"description": "A test JSON file with tab indentation",
+	"author": "coding-agent",
+	"data": {
+		"items": [
+			{
+				"id": 1,
+				"name": "First item",
+				"active": true
+			},
+			{
+				"id": 2,
+				"name": "Second item",
+				"active": false
+			}
+		],
+		"metadata": {
+			"created": "2024-11-11",
+			"tags": [
+				"test",
+				"example",
+				"json"
+			]
+		}
+	}
+}
diff --git a/packages/tui/src/components/markdown.ts b/packages/tui/src/components/markdown.ts
index 50045a34..803ce409 100644
--- a/packages/tui/src/components/markdown.ts
+++ b/packages/tui/src/components/markdown.ts
@@ -103,8 +103,11 @@ export class Markdown implements Component {
 			return result;
 		}
 
+		// Replace tabs with 3 spaces for consistent rendering
+		const normalizedText = this.text.replace(/\t/g, "   ");
+
 		// Parse markdown to HTML-like tokens
-		const tokens = marked.lexer(this.text);
+		const tokens = marked.lexer(normalizedText);
 
 		// Convert tokens to styled terminal output
 		const renderedLines: string[] = [];
diff --git a/packages/tui/src/components/text.ts b/packages/tui/src/components/text.ts
index b1b6946a..6e6598da 100644
--- a/packages/tui/src/components/text.ts
+++ b/packages/tui/src/components/text.ts
@@ -63,8 +63,11 @@ export class Text implements Component {
 			return result;
 		}
 
+		// Replace tabs with 3 spaces for consistent rendering
+		const normalizedText = this.text.replace(/\t/g, "   ");
+
 		const lines: string[] = [];
-		const textLines = this.text.split("\n");
+		const textLines = normalizedText.split("\n");
 
 		for (const line of textLines) {
 			// Measure visible length (strip ANSI codes)
diff --git a/packages/tui/src/utils.ts b/packages/tui/src/utils.ts
index 64b8d778..59ba5ac9 100644
--- a/packages/tui/src/utils.ts
+++ b/packages/tui/src/utils.ts
@@ -6,7 +6,10 @@ import stringWidth from "string-width";
  * - ANSI escape codes (ignored)
  * - Emojis and wide characters (counted as 2 columns)
  * - Combining characters (counted correctly)
+ * - Tabs (replaced with 3 spaces for consistent width)
  */
 export function visibleWidth(str: string): number {
-	return stringWidth(str);
+	// Replace tabs with 3 spaces before measuring
+	const normalized = str.replace(/\t/g, "   ");
+	return stringWidth(normalized);
 }