diff --git a/packages/coding-agent/src/core/tools/bash.ts b/packages/coding-agent/src/core/tools/bash.ts
index 4620e24648b6..0d28a7cba97e 100644
--- a/packages/coding-agent/src/core/tools/bash.ts
+++ b/packages/coding-agent/src/core/tools/bash.ts
@@ -235,6 +235,8 @@ export interface ShellToolConfig {
 	label: string;
 	shellName: string;
 	prompt: string;
+	/** Highlight heredoc bodies and inline scripts, which requires POSIX shell syntax. */
+	embeddedCode: boolean;
 	promptSnippet: string;
 	promptGuidelines?: readonly string[];
 	tempFilePrefix: string;
@@ -410,7 +412,7 @@ export function createShellToolDefinition(
 				clearUpdateTimer();
 			}
 		},
-		...createShellRenderers(config.prompt),
+		...createShellRenderers(config.prompt, { embeddedCode: config.embeddedCode }),
 	};
 }
 
@@ -419,6 +421,7 @@ const bashToolConfig: ShellToolConfig = {
 	label: "bash",
 	shellName: "bash",
 	prompt: "$",
+	embeddedCode: true,
 	promptSnippet: bashToolSystemPromptContribution.snippet,
 	promptGuidelines: bashToolSystemPromptContribution.guidelines,
 	tempFilePrefix: "pi-bash",
diff --git a/packages/coding-agent/src/core/tools/powershell.ts b/packages/coding-agent/src/core/tools/powershell.ts
index ac8a491170ee..140025bdb025 100644
--- a/packages/coding-agent/src/core/tools/powershell.ts
+++ b/packages/coding-agent/src/core/tools/powershell.ts
@@ -41,6 +41,7 @@ const powershellToolConfig: ShellToolConfig = {
 	label: "powershell",
 	shellName: "PowerShell",
 	prompt: "PS>",
+	embeddedCode: false,
 	promptSnippet: powershellToolSystemPromptContribution.snippet,
 	promptGuidelines: powershellToolSystemPromptContribution.guidelines,
 	tempFilePrefix: "pi-powershell",
diff --git a/packages/coding-agent/src/core/tools/render-utils.ts b/packages/coding-agent/src/core/tools/render-utils.ts
index c0fca375d3bd..c0074f8525db 100644
--- a/packages/coding-agent/src/core/tools/render-utils.ts
+++ b/packages/coding-agent/src/core/tools/render-utils.ts
@@ -55,6 +55,66 @@ export function normalizeDisplayText(text: string): string {
 	return text.replace(/\r/g, "");
 }
 
+/** Leading lines of a streaming highlight that are re-highlighted with full context on each update. */
+const STREAMING_FULL_HIGHLIGHT_PREFIX_LINES = 50;
+
+/** Highlighted display lines of streamed source text, for {@link updateStreamingHighlight}. */
+export interface StreamingHighlight {
+	source: string;
+	language: string | undefined;
+	theme: Theme;
+	/** Display lines of `source` after normalizeDisplayText and replaceTabs. */
+	lines: string[];
+	/** Styled version of each entry in `lines`. */
+	highlighted: string[];
+	/** False when some lines were highlighted one at a time, without multi-line context. */
+	exact: boolean;
+}
+
+/**
+ * Highlight source text that arrives in growing chunks, such as streamed tool arguments.
+ *
+ * Renderers run on every argument delta, so highlighting the full text each time costs O(n^2) while
+ * a long body streams in. When the new source extends the previous one, only the changed last line
+ * and new lines are highlighted, one line at a time. The first lines, which collapsed previews show,
+ * are re-highlighted with full context. Once `complete` is set, the text is highlighted in full once
+ * and then reused until the source, language, or theme changes.
+ */
+export function updateStreamingHighlight(
+	previous: StreamingHighlight | undefined,
+	source: string,
+	options: {
+		language: string | undefined;
+		theme: Theme;
+		complete: boolean;
+		highlight: (code: string) => string[];
+	},
+): StreamingHighlight {
+	const { language, theme, complete, highlight } = options;
+	const reusable = previous !== undefined && previous.language === language && previous.theme === theme;
+	if (reusable && previous.source === source && (previous.exact || !complete)) return previous;
+	if (reusable && !complete && source.startsWith(previous.source)) {
+		const highlightLine = (line: string) => highlight(line)[0] ?? "";
+		const { lines, highlighted } = previous;
+		const added = replaceTabs(normalizeDisplayText(source.slice(previous.source.length))).split("\n");
+		const last = lines.length - 1;
+		lines[last] += added[0];
+		highlighted[last] = highlightLine(lines[last]);
+		for (let i = 1; i < added.length; i++) {
+			lines.push(added[i]);
+			highlighted.push(highlightLine(added[i]));
+		}
+		const prefixCount = Math.min(STREAMING_FULL_HIGHLIGHT_PREFIX_LINES, lines.length);
+		const prefix = highlight(lines.slice(0, prefixCount).join("\n"));
+		for (let i = 0; i < prefixCount; i++) highlighted[i] = prefix[i] ?? highlighted[i];
+		previous.source = source;
+		previous.exact = prefixCount === lines.length;
+		return previous;
+	}
+	const lines = replaceTabs(normalizeDisplayText(source)).split("\n");
+	return { source, language, theme, lines, highlighted: highlight(lines.join("\n")), exact: true };
+}
+
 export function getTextOutput(
 	result: { content: Array<{ type: string; text?: string; data?: string; mimeType?: string }> } | undefined,
 	showImages: boolean,
diff --git a/packages/coding-agent/src/core/tools/renderers/bash.ts b/packages/coding-agent/src/core/tools/renderers/bash.ts
index 4631b6b2cb3c..d11f9b054e17 100644
--- a/packages/coding-agent/src/core/tools/renderers/bash.ts
+++ b/packages/coding-agent/src/core/tools/renderers/bash.ts
@@ -9,20 +9,127 @@
 import { Container, Spacer, Text } from "@earendil-works/pi-tui";
 import { keyHint } from "../../../modes/interactive/components/keybinding-hints.ts";
 import { VisualLinePreview } from "../../../modes/interactive/components/visual-truncate.ts";
-import { theme } from "../../../modes/interactive/theme/theme.ts";
+import {
+	getLanguageFromPath,
+	getThemeInstance,
+	highlightCode,
+	type Theme,
+	theme,
+} from "../../../modes/interactive/theme/theme.ts";
+import { splitShellCommand } from "../../../utils/shell-embedded-code.ts";
 import type { ToolDefinition, ToolRenderResultOptions } from "../../extensions/types.ts";
 import type { BashToolDetails } from "../bash.ts";
-import { getTextOutput, invalidArgText, startToolTimer, str, toolTimerText } from "../render-utils.ts";
+import {
+	getTextOutput,
+	invalidArgText,
+	type StreamingHighlight,
+	startToolTimer,
+	str,
+	toolTimerText,
+	updateStreamingHighlight,
+} from "../render-utils.ts";
 import { DEFAULT_MAX_BYTES, formatSize } from "../truncate.ts";
 
 const BASH_PREVIEW_LINES = 5;
+/** Lines of each heredoc body or inline script shown before the call is expanded. */
+const EMBEDDED_CODE_PREVIEW_LINES = 10;
 export const BASH_UPDATE_THROTTLE_MS = 100;
-function formatShellCall(args: { command?: string; timeout?: number } | undefined, prompt: string): string {
+function styleShellLines(text: string): string[] {
+	return text.split("\n").map((line) => (line ? theme.fg("toolTitle", theme.bold(line)) : ""));
+}
+/** Style normalized embedded code. Data with no known language keeps the plain output color. */
+function styleEmbeddedLines(code: string, language: string | undefined): string[] {
+	if (!language) return code.split("\n").map((line) => theme.fg("toolOutput", line));
+	return highlightCode(code, language);
+}
+
+/**
+ * Lines to show for one embedded segment. The first line continues the preceding shell line and the
+ * last line continues into the following shell text, so collapsed previews keep both and elide the
+ * middle.
+ */
+function formatEmbeddedCode(lines: string[], expanded: boolean): string[] {
+	const hidden = lines.length - 1 - EMBEDDED_CODE_PREVIEW_LINES;
+	if (expanded || hidden <= 0) return lines;
+	const hint = `${theme.fg("muted", `... (${hidden} more lines,`)} ${keyHint("app.tools.expand", "to expand")}${theme.fg("muted", ")")}`;
+	return [...lines.slice(0, EMBEDDED_CODE_PREVIEW_LINES), hint, lines[lines.length - 1]];
+}
+
+class ShellCallRenderComponent extends Text {
+	theme: Theme | undefined;
+	command: string | undefined;
+	expanded = false;
+	timeout: number | undefined;
+	/** Formatted call text for the fields above. */
+	rendered: string | undefined;
+	/** Highlights of the embedded segments of `command`, in order. */
+	embedded: StreamingHighlight[] = [];
+
+	constructor() {
+		super("", 0, 0);
+	}
+}
+
+function formatShellCall(
+	component: ShellCallRenderComponent,
+	args: { command?: string; timeout?: number } | undefined,
+	prompt: string,
+	options: { expanded: boolean; embeddedCode: boolean; argsComplete: boolean },
+): string {
 	const command = str(args?.command);
 	const timeout = args?.timeout as number | undefined;
 	const timeoutSuffix = timeout ? theme.fg("muted", ` (timeout ${timeout}s)`) : "";
-	const commandDisplay = command === null ? invalidArgText(theme) : command ? command : theme.fg("toolOutput", "...");
-	return theme.fg("toolTitle", theme.bold(`${prompt} ${commandDisplay}`)) + timeoutSuffix;
+	if (!command || !options.embeddedCode) {
+		component.rendered = undefined;
+		const commandDisplay =
+			command === null ? invalidArgText(theme) : command ? command : theme.fg("toolOutput", "...");
+		return theme.fg("toolTitle", theme.bold(`${prompt} ${commandDisplay}`)) + timeoutSuffix;
+	}
+
+	const currentTheme = getThemeInstance();
+	// renderCall also runs for every throttled output update with unchanged arguments. Reuse the text
+	// unless the theme changed or the final arguments still need a full highlight.
+	if (
+		component.rendered !== undefined &&
+		component.theme === currentTheme &&
+		component.command === command &&
+		component.expanded === options.expanded &&
+		component.timeout === timeout &&
+		(!options.argsComplete || component.embedded.every((entry) => entry.exact))
+	) {
+		return component.rendered;
+	}
+
+	const lines = [""];
+	const append = (styled: string[]) => {
+		lines[lines.length - 1] += styled[0] ?? "";
+		for (let i = 1; i < styled.length; i++) lines.push(styled[i]);
+	};
+	append(styleShellLines(`${prompt} `));
+	const embedded: StreamingHighlight[] = [];
+	for (const segment of splitShellCommand(command, { languageFromPath: getLanguageFromPath })) {
+		if (!segment.embedded) {
+			append(styleShellLines(segment.text));
+			continue;
+		}
+		const language = segment.language;
+		const highlight = updateStreamingHighlight(component.embedded[embedded.length], segment.text, {
+			language,
+			theme: currentTheme,
+			complete: options.argsComplete,
+			highlight: (code) => styleEmbeddedLines(code, language),
+		});
+		embedded.push(highlight);
+		append(formatEmbeddedCode(highlight.highlighted, options.expanded));
+	}
+
+	component.theme = currentTheme;
+	component.command = command;
+	component.expanded = options.expanded;
+	component.timeout = timeout;
+	component.embedded = embedded;
+	component.rendered = lines.join("\n") + timeoutSuffix;
+	return component.rendered;
 }
 function rebuildBashResultRenderComponent(
 	component: Container,
@@ -89,14 +196,28 @@ function rebuildBashResultRenderComponent(
 	if (timerText) component.addChild(new Text(`\n${theme.fg("muted", timerText)}`, 0, 0));
 }
 
-/** Shell renderers are shared by bash and powershell, which differ only in the prompt they display. */
-export function createShellRenderers(prompt: string): Pick<ToolDefinition<any, any>, "renderCall" | "renderResult"> {
+/**
+ * Shell renderers are shared by bash and powershell. `embeddedCode` highlights heredoc bodies and
+ * inline scripts, which is only implemented for POSIX shell syntax.
+ */
+export function createShellRenderers(
+	prompt: string,
+	options: { embeddedCode: boolean },
+): Pick<ToolDefinition<any, any>, "renderCall" | "renderResult"> {
 	return {
 		renderCall(args, _theme, context) {
 			startToolTimer(context);
-			const text = (context.lastComponent as Text | undefined) ?? new Text("", 0, 0);
-			text.setText(formatShellCall(args as { command?: string; timeout?: number } | undefined, prompt));
-			return text;
+			const component =
+				(context.lastComponent as ShellCallRenderComponent | undefined) ?? new ShellCallRenderComponent();
+			const previous = component.rendered;
+			const text = formatShellCall(component, args as { command?: string; timeout?: number } | undefined, prompt, {
+				expanded: context.expanded,
+				embeddedCode: options.embeddedCode,
+				argsComplete: context.argsComplete,
+			});
+			// setText drops the wrapped-line cache, so skip it when output updates leave the call unchanged.
+			if (text !== previous) component.setText(text);
+			return component;
 		},
 		renderResult(result, options, _theme, context) {
 			const timerText = toolTimerText(context, options.isPartial);
diff --git a/packages/coding-agent/src/core/tools/renderers/index.ts b/packages/coding-agent/src/core/tools/renderers/index.ts
index bd15d01de698..d6794b8f79d5 100644
--- a/packages/coding-agent/src/core/tools/renderers/index.ts
+++ b/packages/coding-agent/src/core/tools/renderers/index.ts
@@ -32,8 +32,8 @@ export {
 export function createAllToolRenderers(): Record<ToolName, ToolRenderers> {
 	return {
 		read: readRenderers,
-		bash: createShellRenderers("$"),
-		powershell: createShellRenderers("PS>"),
+		bash: createShellRenderers("$", { embeddedCode: true }),
+		powershell: createShellRenderers("PS>", { embeddedCode: false }),
 		edit: editRenderers,
 		write: writeRenderers,
 		grep: grepRenderers,
diff --git a/packages/coding-agent/src/core/tools/renderers/write.ts b/packages/coding-agent/src/core/tools/renderers/write.ts
index 7c8f32636ce3..b23b853b14f2 100644
--- a/packages/coding-agent/src/core/tools/renderers/write.ts
+++ b/packages/coding-agent/src/core/tools/renderers/write.ts
@@ -8,84 +8,29 @@
 
 import { Container, Text } from "@earendil-works/pi-tui";
 import { keyHint } from "../../../modes/interactive/components/keybinding-hints.ts";
-import { getLanguageFromPath, highlightCode, type Theme } from "../../../modes/interactive/theme/theme.ts";
+import {
+	getLanguageFromPath,
+	getThemeInstance,
+	highlightCode,
+	type Theme,
+} from "../../../modes/interactive/theme/theme.ts";
 import type { ToolDefinition, ToolRenderResultOptions } from "../../extensions/types.ts";
-import { normalizeDisplayText, renderToolPath, replaceTabs, str } from "../render-utils.ts";
+import {
+	normalizeDisplayText,
+	renderToolPath,
+	replaceTabs,
+	type StreamingHighlight,
+	str,
+	updateStreamingHighlight,
+} from "../render-utils.ts";
 
-type WriteHighlightCache = {
-	rawPath: string | null;
-	lang: string;
-	rawContent: string;
-	normalizedLines: string[];
-	highlightedLines: string[];
-};
 class WriteCallRenderComponent extends Text {
-	cache?: WriteHighlightCache;
+	cache?: StreamingHighlight;
 
 	constructor() {
 		super("", 0, 0);
 	}
 }
-const WRITE_PARTIAL_FULL_HIGHLIGHT_LINES = 50;
-function highlightSingleLine(line: string, lang: string): string {
-	const highlighted = highlightCode(line, lang);
-	return highlighted[0] ?? "";
-}
-function refreshWriteHighlightPrefix(cache: WriteHighlightCache): void {
-	const prefixCount = Math.min(WRITE_PARTIAL_FULL_HIGHLIGHT_LINES, cache.normalizedLines.length);
-	if (prefixCount === 0) return;
-	const prefixSource = cache.normalizedLines.slice(0, prefixCount).join("\n");
-	const prefixHighlighted = highlightCode(prefixSource, cache.lang);
-	for (let i = 0; i < prefixCount; i++) {
-		cache.highlightedLines[i] =
-			prefixHighlighted[i] ?? highlightSingleLine(cache.normalizedLines[i] ?? "", cache.lang);
-	}
-}
-function rebuildWriteHighlightCacheFull(rawPath: string | null, fileContent: string): WriteHighlightCache | undefined {
-	const lang = rawPath ? getLanguageFromPath(rawPath) : undefined;
-	if (!lang) return undefined;
-	const displayContent = normalizeDisplayText(fileContent);
-	const normalized = replaceTabs(displayContent);
-	return {
-		rawPath,
-		lang,
-		rawContent: fileContent,
-		normalizedLines: normalized.split("\n"),
-		highlightedLines: highlightCode(normalized, lang),
-	};
-}
-function updateWriteHighlightCacheIncremental(
-	cache: WriteHighlightCache | undefined,
-	rawPath: string | null,
-	fileContent: string,
-): WriteHighlightCache | undefined {
-	const lang = rawPath ? getLanguageFromPath(rawPath) : undefined;
-	if (!lang) return undefined;
-	if (!cache) return rebuildWriteHighlightCacheFull(rawPath, fileContent);
-	if (cache.lang !== lang || cache.rawPath !== rawPath) return rebuildWriteHighlightCacheFull(rawPath, fileContent);
-	if (!fileContent.startsWith(cache.rawContent)) return rebuildWriteHighlightCacheFull(rawPath, fileContent);
-	if (fileContent.length === cache.rawContent.length) return cache;
-
-	const deltaRaw = fileContent.slice(cache.rawContent.length);
-	const deltaDisplay = normalizeDisplayText(deltaRaw);
-	const deltaNormalized = replaceTabs(deltaDisplay);
-	cache.rawContent = fileContent;
-	if (cache.normalizedLines.length === 0) {
-		cache.normalizedLines.push("");
-		cache.highlightedLines.push("");
-	}
-
-	const segments = deltaNormalized.split("\n");
-	const lastIndex = cache.normalizedLines.length - 1;
-	cache.normalizedLines[lastIndex] += segments[0];
-	cache.highlightedLines[lastIndex] = highlightSingleLine(cache.normalizedLines[lastIndex], cache.lang);
-	for (let i = 1; i < segments.length; i++) {
-		cache.normalizedLines.push(segments[i]);
-		cache.highlightedLines.push(highlightSingleLine(segments[i], cache.lang));
-	}
-	refreshWriteHighlightPrefix(cache);
-	return cache;
-}
 function trimTrailingEmptyLines(lines: string[]): string[] {
 	let end = lines.length;
 	while (end > 0 && lines[end - 1] === "") {
@@ -97,7 +42,7 @@ function formatWriteCall(
 	args: { path?: string; file_path?: string; content?: string } | undefined,
 	options: ToolRenderResultOptions,
 	theme: Theme,
-	cache: WriteHighlightCache | undefined,
+	cache: StreamingHighlight | undefined,
 	cwd: string,
 ): string {
 	const rawPath = str(args?.file_path ?? args?.path);
@@ -110,7 +55,7 @@ function formatWriteCall(
 	} else if (fileContent) {
 		const lang = rawPath ? getLanguageFromPath(rawPath) : undefined;
 		const renderedLines = lang
-			? (cache?.highlightedLines ?? highlightCode(replaceTabs(normalizeDisplayText(fileContent)), lang))
+			? (cache?.highlighted ?? highlightCode(replaceTabs(normalizeDisplayText(fileContent)), lang))
 			: normalizeDisplayText(fileContent).split("\n");
 		const lines = trimTrailingEmptyLines(renderedLines);
 		const totalLines = lines.length;
@@ -149,13 +94,16 @@ export const writeRenderers: Pick<ToolDefinition<any, any>, "renderCall" | "rend
 		const fileContent = str(renderArgs?.content);
 		const component =
 			(context.lastComponent as WriteCallRenderComponent | undefined) ?? new WriteCallRenderComponent();
-		if (fileContent !== null) {
-			component.cache = context.argsComplete
-				? rebuildWriteHighlightCacheFull(rawPath, fileContent)
-				: updateWriteHighlightCacheIncremental(component.cache, rawPath, fileContent);
-		} else {
-			component.cache = undefined;
-		}
+		const lang = rawPath ? getLanguageFromPath(rawPath) : undefined;
+		component.cache =
+			fileContent !== null && lang
+				? updateStreamingHighlight(component.cache, fileContent, {
+						language: lang,
+						theme: getThemeInstance(),
+						complete: context.argsComplete,
+						highlight: (code) => highlightCode(code, lang),
+					})
+				: undefined;
 		component.setText(
 			formatWriteCall(
 				renderArgs,
diff --git a/packages/coding-agent/src/modes/interactive/theme/theme.ts b/packages/coding-agent/src/modes/interactive/theme/theme.ts
index 876ba9e8638e..cd45bec5c3ba 100644
--- a/packages/coding-agent/src/modes/interactive/theme/theme.ts
+++ b/packages/coding-agent/src/modes/interactive/theme/theme.ts
@@ -658,6 +658,16 @@ export const theme: Theme = new Proxy({} as Theme, {
 	},
 });
 
+/**
+ * The active theme instance. Switching or reloading a theme installs a new instance, so renderers can
+ * compare identities to invalidate cached styled output.
+ */
+export function getThemeInstance(): Theme {
+	const t = (globalThis as Record<symbol, Theme>)[THEME_KEY];
+	if (!t) throw new Error("Theme not initialized. Call initTheme() first.");
+	return t;
+}
+
 function setGlobalTheme(t: Theme): void {
 	(globalThis as Record<symbol, Theme>)[THEME_KEY] = t;
 	(globalThis as Record<symbol, Theme>)[THEME_KEY_OLD] = t;
diff --git a/packages/coding-agent/src/utils/shell-embedded-code.ts b/packages/coding-agent/src/utils/shell-embedded-code.ts
new file mode 100644
index 000000000000..912ac83e6988
--- /dev/null
+++ b/packages/coding-agent/src/utils/shell-embedded-code.ts
@@ -0,0 +1,631 @@
+/**
+ * Split a POSIX shell command into shell text and embedded code for display.
+ *
+ * Models often run scripts through the shell tool instead of writing files first:
+ *
+ *   cd repo && python3 - <<'EOF'
+ *   print("hi")
+ *   EOF
+ *   node -e 'console.log(1)'
+ *
+ * Highlighting the whole command as shell renders the heredoc body and inline scripts as shell,
+ * where a lone quote in the embedded code colors the rest of the command. This module finds
+ * heredoc bodies and interpreter inline scripts (`-c`, `-e`, ...) and infers their language from
+ * the command that consumes them, so each part can be highlighted on its own.
+ *
+ * The scanner is approximate and only used for display. It tracks quotes, command boundaries,
+ * redirects, and `$(...)` nesting well enough for the commands models write, and never throws.
+ */
+
+export interface ShellSegment {
+	/** Exact source text. Concatenating all segment texts yields the original command. */
+	text: string;
+	/** False for shell syntax, true for a heredoc body or inline script. */
+	embedded: boolean;
+	/** Highlight language for embedded code. Undefined for plain data such as a commit message. */
+	language?: string;
+}
+
+export interface SplitShellCommandOptions {
+	/** Resolve a highlight language from a file path, used for `cat > file <<'EOF'`. */
+	languageFromPath?: (path: string) => string | undefined;
+}
+
+interface ShellCommand {
+	words: string[];
+	/** Word being built, or undefined between words. */
+	word: string | undefined;
+	/** Set while the next word is a redirect target. */
+	pendingRedirect: { fd: string; dup: boolean } | undefined;
+	/** Target of the last stdout redirect (`> file`, `>> file`, `&> file`). */
+	stdoutTarget: string | undefined;
+}
+
+interface ShellFrame {
+	kind: "shell";
+	command: ShellCommand;
+	/** Open parentheses inside this `$(...)` frame. */
+	parenDepth: number;
+	/** True for `$(...)`, `<(...)`, and `>(...)`, which end at the matching `)`. */
+	substitution: boolean;
+}
+
+interface DoubleQuoteFrame {
+	kind: "double";
+}
+
+type Frame = ShellFrame | DoubleQuoteFrame;
+
+interface PendingHeredoc {
+	delimiter: string;
+	stripTabs: boolean;
+	command: ShellCommand;
+}
+
+interface InterpreterSpec {
+	language: string;
+	/** Flag that introduces an inline script, e.g. `-c` or `-e`. */
+	inlineFlag?: RegExp;
+	/** The first positional argument is the script, as in `awk '{ print $1 }'`. */
+	inlineFirstPositional?: boolean;
+	/** Options whose value is the next word, e.g. `-r json` for ruby. */
+	valueOptions?: ReadonlySet<string>;
+	/** Stdin is code even when positional arguments are present, e.g. `psql mydb <<'SQL'`. */
+	stdinAlwaysCode?: boolean;
+}
+
+const SHELL_INLINE_FLAG = /^-[A-Za-z]*c$/;
+const NODE_INLINE_FLAG = /^(?:-[A-Za-z]*[ep]|--eval|--print)$/;
+
+const PYTHON_SPEC: InterpreterSpec = {
+	language: "python",
+	inlineFlag: /^-[A-Za-z]*c$/,
+	valueOptions: new Set(["-W", "-X", "-m"]),
+};
+const NODE_SPEC: InterpreterSpec = {
+	language: "javascript",
+	inlineFlag: NODE_INLINE_FLAG,
+	valueOptions: new Set(["-r", "--require", "--import", "--loader", "--input-type", "--conditions", "-C"]),
+};
+const TYPESCRIPT_SPEC: InterpreterSpec = {
+	language: "typescript",
+	inlineFlag: NODE_INLINE_FLAG,
+	valueOptions: NODE_SPEC.valueOptions,
+};
+const SHELL_SPEC: InterpreterSpec = {
+	language: "bash",
+	inlineFlag: SHELL_INLINE_FLAG,
+	valueOptions: new Set(["-o", "+o", "-O", "+O"]),
+};
+const AWK_SPEC: InterpreterSpec = {
+	language: "awk",
+	inlineFirstPositional: true,
+	valueOptions: new Set(["-F", "-v", "-f"]),
+};
+
+const INTERPRETERS: Record<string, InterpreterSpec> = {
+	python: PYTHON_SPEC,
+	pypy: PYTHON_SPEC,
+	node: NODE_SPEC,
+	bun: NODE_SPEC,
+	tsx: TYPESCRIPT_SPEC,
+	"ts-node": TYPESCRIPT_SPEC,
+	ruby: { language: "ruby", inlineFlag: /^-[A-Za-z]*e$/, valueOptions: new Set(["-r", "-I"]) },
+	perl: { language: "perl", inlineFlag: /^-[A-Za-z0-9]*[eE]$/, valueOptions: new Set(["-I", "-M", "-m"]) },
+	php: { language: "php", inlineFlag: /^-r$/ },
+	lua: { language: "lua", inlineFlag: /^-e$/ },
+	swift: { language: "swift", inlineFlag: /^-e$/ },
+	osascript: { language: "applescript", inlineFlag: /^-e$/, valueOptions: new Set(["-l"]) },
+	sh: SHELL_SPEC,
+	bash: SHELL_SPEC,
+	zsh: SHELL_SPEC,
+	dash: SHELL_SPEC,
+	ksh: SHELL_SPEC,
+	awk: AWK_SPEC,
+	gawk: AWK_SPEC,
+	mawk: AWK_SPEC,
+	psql: {
+		language: "sql",
+		inlineFlag: /^(?:-c|--command)$/,
+		valueOptions: new Set(["-d", "-h", "-p", "-U", "-f"]),
+		stdinAlwaysCode: true,
+	},
+	mysql: {
+		language: "sql",
+		inlineFlag: /^(?:-e|--execute)$/,
+		valueOptions: new Set(["-u", "-h", "-P", "-D"]),
+		stdinAlwaysCode: true,
+	},
+	duckdb: { language: "sql", inlineFlag: /^-c$/, stdinAlwaysCode: true },
+	sqlite3: { language: "sql", stdinAlwaysCode: true },
+};
+
+/** Heredoc delimiter names that state the body language, e.g. `node tool.js <<'JS'`. */
+const DELIMITER_LANGUAGES: Record<string, string> = {
+	PY: "python",
+	PYTHON: "python",
+	JS: "javascript",
+	JAVASCRIPT: "javascript",
+	NODE: "javascript",
+	MJS: "javascript",
+	TS: "typescript",
+	TYPESCRIPT: "typescript",
+	RB: "ruby",
+	RUBY: "ruby",
+	PL: "perl",
+	PERL: "perl",
+	PHP: "php",
+	LUA: "lua",
+	SWIFT: "swift",
+	SQL: "sql",
+	SH: "bash",
+	BASH: "bash",
+	ZSH: "bash",
+	SHELL: "bash",
+	JSON: "json",
+	YAML: "yaml",
+	YML: "yaml",
+	TOML: "ini",
+	HTML: "xml",
+	XML: "xml",
+	CSS: "css",
+	RS: "rust",
+	RUST: "rust",
+	GO: "go",
+	C: "c",
+	CPP: "cpp",
+	MD: "markdown",
+	MARKDOWN: "markdown",
+	DIFF: "diff",
+	PATCH: "diff",
+};
+
+/** Words that precede the real command without changing what consumes stdin. */
+const TRANSPARENT_WORDS = new Set([
+	"sudo",
+	"time",
+	"nohup",
+	"exec",
+	"command",
+	"builtin",
+	"do",
+	"then",
+	"else",
+	"elif",
+	"if",
+	"while",
+	"until",
+	"!",
+	"{",
+]);
+
+const UV_VALUE_OPTIONS = new Set([
+	"--with",
+	"--with-editable",
+	"--with-requirements",
+	"--python",
+	"-p",
+	"--project",
+	"--directory",
+	"--extra",
+	"--group",
+	"--env-file",
+	"--package",
+	"--index",
+	"--from",
+]);
+
+const ENV_VALUE_OPTIONS = new Set(["-u", "-C", "-S"]);
+const TIMEOUT_VALUE_OPTIONS = new Set(["-s", "-k", "-n", "--signal", "--kill-after"]);
+
+const ASSIGNMENT = /^[A-Za-z_][A-Za-z0-9_]*=/;
+
+function newCommand(): ShellCommand {
+	return { words: [], word: undefined, pendingRedirect: undefined, stdoutTarget: undefined };
+}
+
+function skipOptions(words: string[], index: number, valueOptions?: ReadonlySet<string>): number {
+	let i = index;
+	while (i < words.length && words[i].startsWith("-") && words[i] !== "-") {
+		if (words[i] === "--") return i + 1;
+		if (valueOptions?.has(words[i])) i++;
+		i++;
+	}
+	return i;
+}
+
+/** Strip assignments and wrappers such as `sudo` or `uv run --with x`, returning the program index. */
+function findProgramIndex(words: string[]): number {
+	let i = 0;
+	while (i < words.length) {
+		const word = words[i];
+		if (ASSIGNMENT.test(word) || TRANSPARENT_WORDS.has(word)) {
+			i++;
+		} else if (word === "env") {
+			i = skipOptions(words, i + 1, ENV_VALUE_OPTIONS);
+			while (i < words.length && ASSIGNMENT.test(words[i])) i++;
+		} else if (word === "timeout" || word === "nice") {
+			i = skipOptions(words, i + 1, TIMEOUT_VALUE_OPTIONS);
+			if (word === "timeout") i++;
+		} else if (word === "uv" && words[i + 1] === "run") {
+			i = skipOptions(words, i + 2, UV_VALUE_OPTIONS);
+		} else if (word === "uv" && words[i + 1] === "tool" && words[i + 2] === "run") {
+			i = skipOptions(words, i + 3, UV_VALUE_OPTIONS);
+		} else if (word === "npx" || word === "bunx" || (word === "pnpm" && words[i + 1] === "exec")) {
+			i = skipOptions(words, word === "pnpm" ? i + 2 : i + 1);
+		} else {
+			return i;
+		}
+	}
+	return i;
+}
+
+function programName(word: string): string {
+	const base = word.slice(word.lastIndexOf("/") + 1).replace(/\.exe$/i, "");
+	if (/^python\d*(?:\.\d+)?$/.test(base) || /^pypy\d*$/.test(base)) return "python";
+	return base;
+}
+
+/** `python -m pkg` hands all later arguments to the module, so `-c` is no longer Python's flag. */
+function runsPythonModule(spec: InterpreterSpec, args: string[]): boolean {
+	return spec === PYTHON_SPEC && args.some((arg) => arg.startsWith("-m"));
+}
+
+function substituteVariables(value: string, variables: ReadonlyMap<string, string>): string {
+	return value.replace(
+		/\$(?:\{([A-Za-z_][A-Za-z0-9_]*)\}|([A-Za-z_][A-Za-z0-9_]*))/g,
+		(match, braced: string | undefined, bare: string | undefined) => variables.get(braced ?? bare ?? "") ?? match,
+	);
+}
+
+/** Language of a heredoc body, from the command that reads it or the delimiter name. */
+function heredocLanguage(
+	heredoc: PendingHeredoc,
+	variables: ReadonlyMap<string, string>,
+	options: SplitShellCommandOptions,
+): string | undefined {
+	const words = heredoc.command.words;
+	const programIndex = findProgramIndex(words);
+	const program = programIndex < words.length ? programName(words[programIndex]) : undefined;
+	const pathLanguage = (path: string | undefined) =>
+		path ? options.languageFromPath?.(substituteVariables(path, variables)) : undefined;
+
+	let language: string | undefined;
+	if (program === "cat") {
+		language = pathLanguage(heredoc.command.stdoutTarget);
+	} else if (program === "tee") {
+		const argsStart = skipOptions(words, programIndex + 1);
+		language = pathLanguage(words[argsStart]) ?? pathLanguage(heredoc.command.stdoutTarget);
+	} else if (program !== undefined) {
+		const spec = INTERPRETERS[program];
+		if (spec) {
+			const positionalIndex = skipOptions(words, programIndex + 1, spec.valueOptions);
+			const positional = words[positionalIndex];
+			const readsScriptFromStdin = positional === undefined || positional === "-";
+			const hasInlineScript = spec.inlineFlag
+				? words.slice(programIndex + 1).some((word) => spec.inlineFlag?.test(word))
+				: false;
+			const runsModule = runsPythonModule(spec, words.slice(programIndex + 1));
+			if (spec.stdinAlwaysCode || (readsScriptFromStdin && !hasInlineScript && !runsModule)) {
+				language = spec.language;
+			}
+		}
+	}
+	return language ?? DELIMITER_LANGUAGES[heredoc.delimiter.toUpperCase()];
+}
+
+/**
+ * Language of a quoted word that starts at the current position, if it is an interpreter's inline
+ * script such as the argument of `python3 -c` or `node -e`. Returns undefined for regular words.
+ */
+function inlineScriptLanguage(command: ShellCommand): string | undefined {
+	const words = command.words;
+	const programIndex = findProgramIndex(words);
+	if (programIndex >= words.length) return undefined;
+	const spec = INTERPRETERS[programName(words[programIndex])];
+	if (!spec) return undefined;
+	const args = words.slice(programIndex + 1);
+	// Options after a positional argument belong to a script, as in `python3 tool.py -c x`.
+	if (skipOptions(args, 0, spec.valueOptions) !== args.length || runsPythonModule(spec, args)) return undefined;
+	const previous = args[args.length - 1];
+	if (spec.inlineFlag && previous !== undefined && spec.inlineFlag.test(previous)) return spec.language;
+	if (spec.inlineFirstPositional) return spec.language;
+	return undefined;
+}
+
+/** Split a shell command into shell text, heredoc bodies, and inline scripts. */
+export function splitShellCommand(command: string, options: SplitShellCommandOptions = {}): ShellSegment[] {
+	const segments: ShellSegment[] = [];
+	const variables = new Map<string, string>();
+	const frames: Frame[] = [{ kind: "shell", command: newCommand(), parenDepth: 0, substitution: false }];
+	let pendingHeredocs: PendingHeredoc[] = [];
+	let segmentStart = 0;
+	let i = 0;
+
+	const pushSegment = (end: number, embedded: boolean, language?: string) => {
+		if (end <= segmentStart) return;
+		const text = command.slice(segmentStart, end);
+		const previous = segments[segments.length - 1];
+		if (!embedded && previous && !previous.embedded) {
+			previous.text += text;
+		} else {
+			segments.push(embedded ? { text, embedded, language } : { text, embedded });
+		}
+		segmentStart = end;
+	};
+
+	const shellFrame = (): ShellFrame => {
+		for (let index = frames.length - 1; index >= 0; index--) {
+			const frame = frames[index];
+			if (frame.kind === "shell") return frame;
+		}
+		return frames[0] as ShellFrame;
+	};
+
+	const appendToWord = (text: string) => {
+		const current = shellFrame().command;
+		current.word = (current.word ?? "") + text;
+	};
+
+	const finishWord = (current: ShellCommand) => {
+		if (current.word === undefined) return;
+		const word = current.word;
+		current.word = undefined;
+		if (current.pendingRedirect) {
+			const { fd, dup } = current.pendingRedirect;
+			current.pendingRedirect = undefined;
+			if (!dup && (fd === "1" || fd === "&")) current.stdoutTarget = word;
+			return;
+		}
+		current.words.push(word);
+	};
+
+	const endCommand = (frame: ShellFrame) => {
+		finishWord(frame.command);
+		const words = frame.command.words;
+		const assignments = words[0] === "export" ? words.slice(1) : words;
+		if (assignments.length > 0 && assignments.every((word) => ASSIGNMENT.test(word))) {
+			for (const word of assignments) {
+				const eq = word.indexOf("=");
+				variables.set(word.slice(0, eq), substituteVariables(word.slice(eq + 1), variables));
+			}
+		}
+		frame.command = newCommand();
+	};
+
+	/** Consume heredoc bodies that start at `bodyStart`, returning the index after the last delimiter line. */
+	const consumeHeredocs = (bodyStart: number): number => {
+		let position = bodyStart;
+		for (const heredoc of pendingHeredocs) {
+			const language = heredocLanguage(heredoc, variables, options);
+			pushSegment(position, false);
+			let lineStart = position;
+			let delimiterStart = -1;
+			let delimiterEnd = command.length;
+			while (lineStart < command.length) {
+				const newline = command.indexOf("\n", lineStart);
+				const lineEnd = newline === -1 ? command.length : newline;
+				let line = command.slice(lineStart, lineEnd);
+				if (heredoc.stripTabs) line = line.replace(/^\t+/, "");
+				// A delimiter on the last line of a streaming command may still be growing, but an
+				// exact match is also how a complete command ends, so both cases are treated as closed.
+				if (line === heredoc.delimiter) {
+					delimiterStart = lineStart;
+					delimiterEnd = newline === -1 ? command.length : newline + 1;
+					break;
+				}
+				if (newline === -1) break;
+				lineStart = newline + 1;
+			}
+			if (delimiterStart === -1) {
+				pushSegment(command.length, true, language);
+				pendingHeredocs = [];
+				return command.length;
+			}
+			pushSegment(delimiterStart, true, language);
+			position = delimiterEnd;
+		}
+		pendingHeredocs = [];
+		return position;
+	};
+
+	/** Emit an inline script inside quotes that open at `quoteIndex` and close at `closeIndex`. */
+	const emitInlineScript = (quoteIndex: number, closeIndex: number, language: string) => {
+		pushSegment(quoteIndex + 1, false);
+		pushSegment(closeIndex, true, language);
+	};
+
+	const findDoubleQuoteEnd = (start: number): number => {
+		for (let index = start; index < command.length; index++) {
+			const char = command[index];
+			if (char === "\\") index++;
+			else if (char === '"') return index;
+		}
+		return command.length;
+	};
+
+	while (i < command.length) {
+		const frame = frames[frames.length - 1];
+		const char = command[i];
+		const next = command[i + 1];
+
+		if (frame.kind === "double") {
+			if (char === "\\") {
+				appendToWord(next ?? "");
+				i += 2;
+			} else if (char === '"') {
+				frames.pop();
+				i++;
+			} else if (char === "$" && next === "(" && command[i + 2] !== "(") {
+				appendToWord("$()");
+				frames.push({ kind: "shell", command: newCommand(), parenDepth: 0, substitution: true });
+				i += 2;
+			} else {
+				appendToWord(char);
+				i++;
+			}
+			continue;
+		}
+
+		const current = frame.command;
+		switch (char) {
+			case "\\": {
+				if (next !== "\n") appendToWord(next ?? "");
+				i += 2;
+				break;
+			}
+			case "'": {
+				const close = command.indexOf("'", i + 1);
+				const end = close === -1 ? command.length : close;
+				const language = current.word === undefined ? inlineScriptLanguage(current) : undefined;
+				if (language) emitInlineScript(i, end, language);
+				appendToWord(command.slice(i + 1, end));
+				i = end + 1;
+				break;
+			}
+			case '"': {
+				const language = current.word === undefined ? inlineScriptLanguage(current) : undefined;
+				if (language) {
+					const end = findDoubleQuoteEnd(i + 1);
+					emitInlineScript(i, end, language);
+					appendToWord(command.slice(i + 1, end));
+					i = end + 1;
+				} else {
+					appendToWord("");
+					frames.push({ kind: "double" });
+					i++;
+				}
+				break;
+			}
+			case "$": {
+				if (next === "(" && command[i + 2] === "(") {
+					// Arithmetic expansion: `<<` inside is a shift, not a heredoc.
+					const close = command.indexOf("))", i + 3);
+					const end = close === -1 ? command.length : close + 2;
+					appendToWord(command.slice(i, end));
+					i = end;
+				} else if (next === "(") {
+					appendToWord("$()");
+					frames.push({ kind: "shell", command: newCommand(), parenDepth: 0, substitution: true });
+					i += 2;
+				} else {
+					appendToWord(char);
+					i++;
+				}
+				break;
+			}
+			case "#": {
+				if (current.word !== undefined) {
+					appendToWord(char);
+					i++;
+					break;
+				}
+				const newline = command.indexOf("\n", i);
+				i = newline === -1 ? command.length : newline;
+				break;
+			}
+			case " ":
+			case "\t": {
+				finishWord(current);
+				i++;
+				break;
+			}
+			case "\n": {
+				endCommand(frame);
+				i = pendingHeredocs.length > 0 ? consumeHeredocs(i + 1) : i + 1;
+				break;
+			}
+			case ";":
+			case "|": {
+				endCommand(frame);
+				i++;
+				break;
+			}
+			case "&": {
+				if (next === ">") {
+					finishWord(current);
+					current.pendingRedirect = { fd: "&", dup: false };
+					i += command[i + 2] === ">" ? 3 : 2;
+				} else {
+					endCommand(frame);
+					i++;
+				}
+				break;
+			}
+			case "(": {
+				endCommand(frame);
+				frame.parenDepth++;
+				i++;
+				break;
+			}
+			case ")": {
+				endCommand(frame);
+				if (frame.substitution && frame.parenDepth === 0) frames.pop();
+				else frame.parenDepth = Math.max(0, frame.parenDepth - 1);
+				i++;
+				break;
+			}
+			case "<": {
+				if (next === "(") {
+					appendToWord("<()");
+					frames.push({ kind: "shell", command: newCommand(), parenDepth: 0, substitution: true });
+					i += 2;
+					break;
+				}
+				finishWord(current);
+				if (next !== "<") {
+					current.pendingRedirect = { fd: "0", dup: false };
+					i++;
+					break;
+				}
+				if (command[i + 2] === "<") {
+					// Here-string: the next word is data, not an argument.
+					current.pendingRedirect = { fd: "0", dup: false };
+					i += 3;
+					break;
+				}
+				const match = /^<<(-?)[ \t]*(?:'([^'\n]*)'|"([^"\n]*)"|\\?([^\s;&|<>()'"]+))/.exec(command.slice(i));
+				if (!match) {
+					i += 2;
+					break;
+				}
+				const delimiter = match[2] ?? match[3] ?? match[4] ?? "";
+				// While streaming, the operator line may end before the delimiter is complete.
+				const complete = i + match[0].length < command.length;
+				if (delimiter && complete) {
+					pendingHeredocs.push({ delimiter, stripTabs: match[1] === "-", command: current });
+				}
+				i += match[0].length;
+				break;
+			}
+			case ">": {
+				let fd = "1";
+				if (current.word !== undefined && /^\d+$/.test(current.word)) {
+					fd = current.word;
+					current.word = undefined;
+				} else {
+					finishWord(current);
+				}
+				if (next === "(") {
+					appendToWord(">()");
+					frames.push({ kind: "shell", command: newCommand(), parenDepth: 0, substitution: true });
+					i += 2;
+					break;
+				}
+				i++;
+				if (command[i] === ">" || command[i] === "|") i++;
+				const dup = command[i] === "&";
+				if (dup) i++;
+				current.pendingRedirect = { fd, dup };
+				break;
+			}
+			default: {
+				appendToWord(char);
+				i++;
+			}
+		}
+	}
+
+	pushSegment(command.length, false);
+	return segments;
+}
diff --git a/packages/coding-agent/test/shell-embedded-code.test.ts b/packages/coding-agent/test/shell-embedded-code.test.ts
new file mode 100644
index 000000000000..9d08c7e2156e
--- /dev/null
+++ b/packages/coding-agent/test/shell-embedded-code.test.ts
@@ -0,0 +1,119 @@
+import { describe, expect, test } from "vitest";
+import { type ShellSegment, splitShellCommand } from "../src/utils/shell-embedded-code.ts";
+
+const EXTENSIONS: Record<string, string> = { rs: "rust", ts: "typescript", py: "python", json: "json" };
+
+function split(command: string): ShellSegment[] {
+	const segments = splitShellCommand(command, {
+		languageFromPath: (path) => EXTENSIONS[path.slice(path.lastIndexOf(".") + 1)],
+	});
+	expect(segments.map((segment) => segment.text).join("")).toBe(command);
+	return segments;
+}
+
+function embedded(command: string): Array<{ text: string; language: string | undefined }> {
+	return split(command)
+		.filter((segment) => segment.embedded)
+		.map((segment) => ({ text: segment.text, language: segment.language }));
+}
+
+describe("splitShellCommand", () => {
+	test("leaves plain commands as a single shell segment", () => {
+		expect(split("cd repo && cargo test 2>&1 | grep -E 'a|b'")).toEqual([
+			{ text: "cd repo && cargo test 2>&1 | grep -E 'a|b'", embedded: false },
+		]);
+	});
+
+	test("splits a python heredoc and keeps following commands as shell", () => {
+		const command = "cd repo && python3 - <<'EOF'\ns = open('a').read()\nprint(\"it's\")\nEOF\ncargo test";
+		expect(split(command)).toEqual([
+			{ text: "cd repo && python3 - <<'EOF'\n", embedded: false },
+			{ text: "s = open('a').read()\nprint(\"it's\")\n", embedded: true, language: "python" },
+			{ text: "EOF\ncargo test", embedded: false },
+		]);
+	});
+
+	test("infers interpreters behind wrappers and redirects", () => {
+		expect(embedded("uv run --no-project --with httpx --with bs4 python - <<'PY'\nx = 1\nPY")).toEqual([
+			{ text: "x = 1\n", language: "python" },
+		]);
+		expect(embedded("./python.exe - <<'PY' > /tmp/log 2>&1\nx = 1\nPY")).toEqual([
+			{ text: "x = 1\n", language: "python" },
+		]);
+		expect(embedded("node --input-type=module <<'JS'\nconsole.log(1)\nJS")).toEqual([
+			{ text: "console.log(1)\n", language: "javascript" },
+		]);
+		expect(embedded("for d in a b; do timeout 20 bash <<'EOF'\necho $d\nEOF\ndone")).toEqual([
+			{ text: "echo $d\n", language: "bash" },
+		]);
+	});
+
+	test("uses the file extension for cat and tee targets", () => {
+		expect(embedded("cat >> deser-json/tests/test_de.rs <<'EOF'\n#[test]\nfn x() {}\nEOF")).toEqual([
+			{ text: "#[test]\nfn x() {}\n", language: "rust" },
+		]);
+		expect(embedded("cat <<'EOF' > out.json\n{}\nEOF")).toEqual([{ text: "{}\n", language: "json" }]);
+		expect(embedded("tee -a notes.py <<'EOF'\nx = 1\nEOF")).toEqual([{ text: "x = 1\n", language: "python" }]);
+		expect(embedded("F=test/zz-tmp-$$.test.ts && cat > $F <<'EOF'\nconst x = 1;\nEOF")).toEqual([
+			{ text: "const x = 1;\n", language: "typescript" },
+		]);
+	});
+
+	test("falls back to the delimiter name when stdin is data for a script", () => {
+		expect(embedded("node tools/workspace.js exec --email a@b.c <<'JS' >out.json &\nreturn 1;\nJS")).toEqual([
+			{ text: "return 1;\n", language: "javascript" },
+		]);
+		expect(embedded("python3 script.py <<'EOF'\ndata\nEOF")).toEqual([{ text: "data\n", language: undefined }]);
+		expect(embedded("git commit -F - <<'EOF'\nfix: thing\nEOF")).toEqual([
+			{ text: "fix: thing\n", language: undefined },
+		]);
+	});
+
+	test("handles <<- and consecutive heredocs", () => {
+		expect(embedded("python3 - <<-PY\n\tx = 1\n\tPY\nnode <<'JS'\ny()\nJS\n")).toEqual([
+			{ text: "\tx = 1\n", language: "python" },
+			{ text: "y()\n", language: "javascript" },
+		]);
+	});
+
+	test("treats an unterminated heredoc as running to the end while streaming", () => {
+		expect(split("python3 - <<'EOF'\nprint(1)\nEO")).toEqual([
+			{ text: "python3 - <<'EOF'\n", embedded: false },
+			{ text: "print(1)\nEO", embedded: true, language: "python" },
+		]);
+		expect(split("python3 - <<'EO")).toEqual([{ text: "python3 - <<'EO", embedded: false }]);
+	});
+
+	test("ignores << inside quotes, arithmetic, and here-strings", () => {
+		expect(embedded("rg -n 'a <<EOF b' && echo $((1 << 3)) && cat <<< \"x\"\nfoo")).toEqual([]);
+	});
+
+	test("extracts inline interpreter scripts", () => {
+		expect(split('cd x && python3 -c "\nimport sys\nprint(sys.argv)\n" 2>&1 | tail')).toEqual([
+			{ text: 'cd x && python3 -c "', embedded: false },
+			{ text: "\nimport sys\nprint(sys.argv)\n", embedded: true, language: "python" },
+			{ text: '" 2>&1 | tail', embedded: false },
+		]);
+		expect(embedded("node -e 'console.log(1)'")).toEqual([{ text: "console.log(1)", language: "javascript" }]);
+		expect(embedded("ruby -rjson -e 'puts 1'")).toEqual([{ text: "puts 1", language: "ruby" }]);
+		expect(embedded("perl -0pi -e 's/a/b/' file")).toEqual([{ text: "s/a/b/", language: "perl" }]);
+		expect(embedded("zsh -i -c 'echo hi'")).toEqual([{ text: "echo hi", language: "bash" }]);
+		expect(embedded("awk -F: '{ print $1 }' /etc/passwd")).toEqual([{ text: "{ print $1 }", language: "awk" }]);
+		expect(embedded("osascript -e 'tell app \"Finder\" to quit'")).toEqual([
+			{ text: 'tell app "Finder" to quit', language: "applescript" },
+		]);
+	});
+
+	test("does not treat flags of other tools as inline scripts", () => {
+		expect(embedded("grep -e 'foo' x && rg -n 'bar' && git commit -m \"feat: x\n\nbody\"")).toEqual([]);
+		expect(embedded("sed -e 's/a/b/' x && python3 script.py -c 'x'")).toEqual([]);
+		expect(embedded("python3 -m pytest -c 'conf.ini' && python -mpytest -c 'conf.ini'")).toEqual([]);
+		expect(embedded("python3 -m tool <<'EOF'\ndata\nEOF")).toEqual([{ text: "data\n", language: undefined }]);
+	});
+
+	test("finds heredocs inside command substitution", () => {
+		expect(embedded("git commit -m \"$(cat <<'EOF'\nfix: x\nEOF\n)\"")).toEqual([
+			{ text: "fix: x\n", language: undefined },
+		]);
+	});
+});
diff --git a/packages/coding-agent/test/streaming-highlight.test.ts b/packages/coding-agent/test/streaming-highlight.test.ts
new file mode 100644
index 000000000000..55ed86a19775
--- /dev/null
+++ b/packages/coding-agent/test/streaming-highlight.test.ts
@@ -0,0 +1,109 @@
+import type { TUI } from "@earendil-works/pi-tui";
+import { beforeAll, describe, expect, test, vi } from "vitest";
+import type * as SyntaxHighlight from "../src/utils/syntax-highlight.ts";
+
+const highlightedLines = vi.hoisted(() => ({ count: 0 }));
+
+vi.mock("../src/utils/syntax-highlight.ts", async (importOriginal) => {
+	const original = await importOriginal<typeof SyntaxHighlight>();
+	return {
+		...original,
+		highlight: (code: string, options: Parameters<typeof original.highlight>[1]) => {
+			highlightedLines.count += code.split("\n").length;
+			return original.highlight(code, options);
+		},
+	};
+});
+
+import { createBashToolDefinition } from "../src/core/tools/bash.ts";
+import { createWriteToolDefinition } from "../src/core/tools/write.ts";
+import { ToolExecutionComponent } from "../src/modes/interactive/components/tool-execution.ts";
+import { initTheme } from "../src/modes/interactive/theme/theme.ts";
+
+function createToolComponent(
+	name: string,
+	args: Record<string, unknown>,
+	definition: ConstructorParameters<typeof ToolExecutionComponent>[4],
+): ToolExecutionComponent {
+	return new ToolExecutionComponent(
+		name,
+		`tool-${name}-cache`,
+		args,
+		{},
+		definition,
+		{ requestRender: () => {} } as unknown as TUI,
+		process.cwd(),
+	);
+}
+
+function createComponent(command: string): ToolExecutionComponent {
+	return createToolComponent(
+		"bash",
+		{ command },
+		createBashToolDefinition(process.cwd(), { exposeSessionEnvironment: false }),
+	);
+}
+
+describe("streaming call highlighting", () => {
+	beforeAll(() => {
+		initTheme("dark");
+	});
+
+	test("highlights streamed heredocs incrementally and reuses the result for output updates", () => {
+		const header = "cat > src/lib.rs <<'EOF'\n";
+		const bodyLines = Array.from({ length: 400 }, (_, i) => `fn f${i}() -> u32 { ${i} }`);
+		const command = `${header}${bodyLines.join("\n")}\nEOF`;
+
+		const component = createComponent(header);
+		component.setExpanded(true);
+		highlightedLines.count = 0;
+		for (let i = 1; i <= bodyLines.length; i++) {
+			component.updateArgs({ command: `${header}${bodyLines.slice(0, i).join("\n")}\n` });
+		}
+		component.updateArgs({ command });
+		// Each update highlights its new line plus a bounded prefix; a full rehighlight per update
+		// would cost 400 * 401 / 2 = 80,200 lines.
+		expect(highlightedLines.count).toBeLessThan(bodyLines.length * 60);
+
+		component.setArgsComplete();
+		component.markExecutionStarted();
+		const final = component.render(200);
+		const fresh = createComponent(command);
+		fresh.setExpanded(true);
+		fresh.setArgsComplete();
+		fresh.markExecutionStarted();
+		expect(final).toEqual(fresh.render(200));
+
+		highlightedLines.count = 0;
+		for (let i = 0; i < 10; i++) {
+			component.updateResult({ content: [{ type: "text", text: `line ${i}` }], isError: false }, true);
+		}
+		component.updateResult({ content: [{ type: "text", text: "done" }], isError: false }, false);
+		expect(highlightedLines.count).toBe(0);
+	});
+
+	test("highlights streamed write content incrementally and fully once complete", () => {
+		const definition = createWriteToolDefinition(process.cwd());
+		const contentLines = Array.from({ length: 400 }, (_, i) => `const s${i} = \`multi`);
+		const content = `${contentLines.join("\n")}\n`;
+
+		const component = createToolComponent("write", { path: "src/a.ts", content: "" }, definition);
+		component.setExpanded(true);
+		highlightedLines.count = 0;
+		for (let i = 1; i <= contentLines.length; i++) {
+			component.updateArgs({ path: "src/a.ts", content: `${contentLines.slice(0, i).join("\n")}\n` });
+		}
+		expect(highlightedLines.count).toBeLessThan(contentLines.length * 60);
+
+		// The unterminated template literal spans lines, so only a full highlight matches a fresh render.
+		component.setArgsComplete();
+		const fresh = createToolComponent("write", { path: "src/a.ts", content }, definition);
+		fresh.setExpanded(true);
+		fresh.setArgsComplete();
+		expect(component.render(200)).toEqual(fresh.render(200));
+
+		highlightedLines.count = 0;
+		component.updateResult({ content: [{ type: "text", text: "ok" }], isError: false }, false);
+		expect(highlightedLines.count).toBe(0);
+	});
+});
diff --git a/packages/coding-agent/test/tool-execution-component.test.ts b/packages/coding-agent/test/tool-execution-component.test.ts
index f334f7d6b2f6..8b37c53ca081 100644
--- a/packages/coding-agent/test/tool-execution-component.test.ts
+++ b/packages/coding-agent/test/tool-execution-component.test.ts
@@ -289,6 +289,36 @@ describe("ToolExecutionComponent parity", () => {
 		expect(render(false)).toContain("Took 4.2s");
 	});
 
+	test("bash renderer highlights heredoc bodies and collapses long ones", () => {
+		const body = Array.from({ length: 15 }, (_, i) => `import mod${i + 1}`).join("\n");
+		const command = `cd repo && python3 - <<'EOF'\n${body}\nEOF\ncargo test`;
+		const component = new ToolExecutionComponent(
+			"bash",
+			"tool-bash-heredoc",
+			{ command },
+			{},
+			createBashToolDefinition(process.cwd(), { exposeSessionEnvironment: false }),
+			createFakeTui(),
+			process.cwd(),
+		);
+
+		const collapsed = component.render(120);
+		const plain = collapsed.map((line) => stripAnsi(line).trimEnd());
+		expect(plain).toContain(" $ cd repo && python3 - <<'EOF'");
+		expect(plain).toContain(" import mod10");
+		expect(plain).not.toContain(" import mod11");
+		expect(plain.some((line) => line.startsWith(" ... (5 more lines,"))).toBe(true);
+		expect(plain).toContain(" EOF");
+		expect(plain).toContain(" cargo test");
+		const bodyLine = collapsed[plain.indexOf(" import mod1")];
+		expect(bodyLine).toContain(theme.fg("syntaxKeyword", "import"));
+
+		component.setExpanded(true);
+		const expanded = component.render(120).map((line) => stripAnsi(line).trimEnd());
+		expect(expanded).toContain(" import mod15");
+		expect(expanded.some((line) => line.includes("more lines"))).toBe(false);
+	});
+
 	test("does not duplicate built-in headers when passed the active built-in definition", () => {
 		const component = new ToolExecutionComponent(
 			"read",