diff --git a/src/core/assistant-message/__tests__/presentAssistantMessage-environment-filtering.spec.ts b/src/core/assistant-message/__tests__/presentAssistantMessage-environment-filtering.spec.ts
new file mode 100644
index 0000000000..a80a0e3211
--- /dev/null
+++ b/src/core/assistant-message/__tests__/presentAssistantMessage-environment-filtering.spec.ts
@@ -0,0 +1,313 @@
+// npx vitest src/core/assistant-message/__tests__/presentAssistantMessage-environment-filtering.spec.ts
+
+import { describe, it, expect, beforeEach, vi } from "vitest"
+import { presentAssistantMessage } from "../presentAssistantMessage"
+
+// Mock dependencies
+vi.mock("../../task/Task")
+vi.mock("../../tools/validateToolUse", () => ({
+	validateToolUse: vi.fn(),
+}))
+vi.mock("@roo-code/telemetry", () => ({
+	TelemetryService: {
+		instance: {
+			captureToolUsage: vi.fn(),
+			captureConsecutiveMistakeError: vi.fn(),
+		},
+	},
+}))
+
+describe("presentAssistantMessage - Environment Details Filtering", () => {
+	let mockTask: any
+
+	beforeEach(() => {
+		// Create a mock Task with minimal properties needed for testing
+		mockTask = {
+			taskId: "test-task-id",
+			instanceId: "test-instance",
+			abort: false,
+			presentAssistantMessageLocked: false,
+			presentAssistantMessageHasPendingUpdates: false,
+			currentStreamingContentIndex: 0,
+			assistantMessageContent: [],
+			userMessageContent: [],
+			didCompleteReadingStream: false,
+			didRejectTool: false,
+			didAlreadyUseTool: false,
+			diffEnabled: false,
+			consecutiveMistakeCount: 0,
+			api: {
+				getModel: () => ({ id: "xai/grok-code-fast-1", info: {} }),
+			},
+			browserSession: {
+				closeBrowser: vi.fn().mockResolvedValue(undefined),
+			},
+			recordToolUsage: vi.fn(),
+			toolRepetitionDetector: {
+				check: vi.fn().mockReturnValue({ allowExecution: true }),
+			},
+			providerRef: {
+				deref: () => ({
+					getState: vi.fn().mockResolvedValue({
+						mode: "code",
+						customModes: [],
+					}),
+				}),
+			},
+			say: vi.fn().mockResolvedValue(undefined),
+			ask: vi.fn().mockResolvedValue({ response: "yesButtonClicked" }),
+		}
+	})
+
+	it("should filter out complete <environment_details> tags", async () => {
+		const contentWithEnvironmentDetails = `Here is my response.
+<environment_details>
+# VSCode Visible Files
+src/test.ts
+# Current Time
+2025-11-20T03:00:00Z
+</environment_details>
+This is the actual content the user should see.`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: contentWithEnvironmentDetails,
+				partial: false,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		// Check that say was called with filtered content
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("Here is my response."),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("This is the actual content the user should see."),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.not.stringContaining("environment_details"),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.not.stringContaining("VSCode Visible Files"),
+			undefined,
+			false,
+		)
+	})
+
+	it("should filter out partial <environment_details> tag at the end", async () => {
+		const contentWithPartialTag = `Here is my response to your query.
+The task has been completed successfully.
+<environment_det`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: contentWithPartialTag,
+				partial: true,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		// Check that say was called with content that doesn't have the partial tag
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("Here is my response to your query."),
+			undefined,
+			true,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("The task has been completed successfully."),
+			undefined,
+			true,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.not.stringContaining("<environment_det"),
+			undefined,
+			true,
+		)
+	})
+
+	it("should filter out closing </environment_details> tag", async () => {
+		const contentWithClosingTag = `Some content here.
+</environment_details>
+The actual response continues here.`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: contentWithClosingTag,
+				partial: false,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		// Check that say was called without the closing tag
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.not.stringContaining("</environment_details>"),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("The actual response continues here."),
+			undefined,
+			false,
+		)
+	})
+
+	it("should filter out multiple environment_details blocks", async () => {
+		const contentWithMultipleBlocks = `First part of response.
+<environment_details>
+First block of system info
+</environment_details>
+Middle content.
+<environment_details>
+Second block of system info
+</environment_details>
+Final part of response.`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: contentWithMultipleBlocks,
+				partial: false,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		// Check that all environment_details blocks are removed
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("First part of response."),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith("text", expect.stringContaining("Middle content."), undefined, false)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("Final part of response."),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.not.stringContaining("environment_details"),
+			undefined,
+			false,
+		)
+		expect(mockTask.say).toHaveBeenCalledWith("text", expect.not.stringContaining("system info"), undefined, false)
+	})
+
+	it("should handle partial closing tag </environ at the end", async () => {
+		const contentWithPartialClosingTag = `Response text here.
+Some more content.
+</environ`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: contentWithPartialClosingTag,
+				partial: true,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		// Check that the partial closing tag is removed
+		expect(mockTask.say).toHaveBeenCalledWith("text", expect.not.stringContaining("</environ"), undefined, true)
+		expect(mockTask.say).toHaveBeenCalledWith(
+			"text",
+			expect.stringContaining("Response text here."),
+			undefined,
+			true,
+		)
+	})
+
+	it("should preserve normal content while filtering environment_details", async () => {
+		const mixedContent = `Assistant: I'll help you with that task.
+
+<environment_details>
+# System information
+Current directory: /test
+</environment_details>
+
+Let me analyze your code:
+- First point
+- Second point
+
+<environment_details>
+More system info here
+</environment_details>
+
+The solution is straightforward.`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: mixedContent,
+				partial: false,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		const calledContent = mockTask.say.mock.calls[0][1]
+
+		// Check that normal content is preserved
+		expect(calledContent).toContain("I'll help you with that task")
+		expect(calledContent).toContain("Let me analyze your code:")
+		expect(calledContent).toContain("- First point")
+		expect(calledContent).toContain("- Second point")
+		expect(calledContent).toContain("The solution is straightforward")
+
+		// Check that environment_details content is removed
+		expect(calledContent).not.toContain("environment_details")
+		expect(calledContent).not.toContain("System information")
+		expect(calledContent).not.toContain("Current directory")
+		expect(calledContent).not.toContain("More system info")
+	})
+
+	it("should handle environment_details tags with whitespace", async () => {
+		const contentWithWhitespace = `Response start.
+<environment_details>  
+Content to be removed
+</environment_details>  
+Response end.`
+
+		mockTask.assistantMessageContent = [
+			{
+				type: "text",
+				content: contentWithWhitespace,
+				partial: false,
+			},
+		]
+
+		await presentAssistantMessage(mockTask)
+
+		const calledContent = mockTask.say.mock.calls[0][1]
+
+		// Check that tags with whitespace are properly removed
+		expect(calledContent).toContain("Response start")
+		expect(calledContent).toContain("Response end")
+		expect(calledContent).not.toContain("environment_details")
+		expect(calledContent).not.toContain("Content to be removed")
+	})
+})
diff --git a/src/core/assistant-message/presentAssistantMessage.ts b/src/core/assistant-message/presentAssistantMessage.ts
index fcf7d25cc9..4fac6ebe40 100644
--- a/src/core/assistant-message/presentAssistantMessage.ts
+++ b/src/core/assistant-message/presentAssistantMessage.ts
@@ -123,8 +123,15 @@ export async function presentAssistantMessage(cline: Task) {
 				content = content.replace(/<thinking>\s?/g, "")
 				content = content.replace(/\s?<\/thinking>/g, "")
 
+				// Remove all instances of <environment_details>...</environment_details> blocks
+				// This prevents internal system messages from being exposed in model responses
+				// Use regex to match the entire block including content between tags
+				content = content.replace(/<environment_details>[\s\S]*?<\/environment_details>/g, "")
+				// Also remove orphaned closing tags that might appear without opening tags
+				content = content.replace(/\s?<\/environment_details>/g, "")
+
 				// Remove partial XML tag at the very end of the content (for
-				// tool use and thinking tags), Prevents scrollview from
+				// tool use, thinking tags, and environment_details tags), Prevents scrollview from
 				// jumping when tags are automatically removed.
 				const lastOpenBracketIndex = content.lastIndexOf("<")
 
@@ -132,7 +139,7 @@ export async function presentAssistantMessage(cline: Task) {
 					const possibleTag = content.slice(lastOpenBracketIndex)
 
 					// Check if there's a '>' after the last '<' (i.e., if the
-					// tag is complete) (complete thinking and tool tags will
+					// tag is complete) (complete thinking, environment_details, and tool tags will
 					// have been removed by now.)
 					const hasCloseBracket = possibleTag.includes(">")
 
@@ -150,14 +157,20 @@ export async function presentAssistantMessage(cline: Task) {
 						// (letters and underscores only).
 						const isLikelyTagName = /^[a-zA-Z_]+$/.test(tagContent)
 
+						// Check if it's a partial environment_details tag
+						const isPartialEnvironmentDetails =
+							"environment_details".startsWith(tagContent.toLowerCase()) ||
+							(tagContent.toLowerCase().startsWith("e") &&
+								"environment_details".includes(tagContent.toLowerCase()))
+
 						// Preemptively remove < or </ to keep from these
 						// artifacts showing up in chat (also handles closing
-						// thinking tags).
+						// thinking and environment_details tags).
 						const isOpeningOrClosing = possibleTag === "<" || possibleTag === "</"
 
 						// If the tag is incomplete and at the end, remove it
 						// from the content.
-						if (isOpeningOrClosing || isLikelyTagName) {
+						if (isOpeningOrClosing || isLikelyTagName || isPartialEnvironmentDetails) {
 							content = content.slice(0, lastOpenBracketIndex).trim()
 						}
 					}