diff --git a/packages/coding-agent/src/eval/py/executor.ts b/packages/coding-agent/src/eval/py/executor.ts
index a33cd5040..42ec13b7f 100644
--- a/packages/coding-agent/src/eval/py/executor.ts
+++ b/packages/coding-agent/src/eval/py/executor.ts
@@ -209,6 +209,15 @@ function formatTimeoutAnnotation(timeoutMs?: number): string | undefined {
 	return `Command timed out after ${secs} seconds`;
 }
 
+function formatKernelTimeoutAnnotation(timeoutMs: number | undefined, kernelKilled: boolean): string {
+	const secs = timeoutMs === undefined ? undefined : Math.max(1, Math.round(timeoutMs / 1000));
+	if (kernelKilled) {
+		return "eval cell timed out and the kernel was unresponsive to interrupt; the kernel has been killed and will be recreated on the next call.";
+	}
+	const duration = secs === undefined ? "the configured timeout" : `${secs}s`;
+	return `eval cell timed out after ${duration}; kernel interrupted but remains running. Reset the kernel via { reset: true } if state appears corrupted.`;
+}
+
 function createCancelledPythonResult(timedOut: boolean, timeoutMs?: number): PythonResult {
 	const output = timedOut ? (formatTimeoutAnnotation(timeoutMs) ?? "Command timed out") : "";
 	const outputBytes = Buffer.byteLength(output, "utf-8");
@@ -434,7 +443,9 @@ async function executeWithKernel(
 		});
 
 		if (result.cancelled) {
-			const annotation = result.timedOut ? formatTimeoutAnnotation(executionTimeoutMs) : undefined;
+			const annotation = result.timedOut
+				? formatKernelTimeoutAnnotation(executionTimeoutMs, result.kernelKilled ?? false)
+				: undefined;
 			return {
 				exitCode: undefined,
 				cancelled: true,
diff --git a/packages/coding-agent/src/eval/py/kernel.ts b/packages/coding-agent/src/eval/py/kernel.ts
index cdeee7722..07d2eb223 100644
--- a/packages/coding-agent/src/eval/py/kernel.ts
+++ b/packages/coding-agent/src/eval/py/kernel.ts
@@ -46,8 +46,10 @@ const STARTUP_TIMEOUT_MS = 10_000;
 // How long to wait after SIGINT for the runner to emit `done`. If the cell is
 // stuck in code that ignores Python signals (e.g. a C extension holding the
 // GIL), we escalate to a full subprocess shutdown so the host queue unblocks
-// instead of hanging the session forever.
-const INTERRUPT_ESCALATION_MS = 2_000;
+// instead of hanging the session forever. The grace window is intentionally
+// generous: a clean interrupt is far preferable to losing the persistent
+// kernel's state, so we only kill as a last-resort recovery path.
+const INTERRUPT_ESCALATION_MS = 5_000;
 
 export interface KernelExecuteOptions {
 	signal?: AbortSignal;
@@ -66,6 +68,12 @@ export interface KernelExecuteResult {
 	cancelled: boolean;
 	timedOut: boolean;
 	stdinRequested: boolean;
+	/**
+	 * True when the kernel subprocess was killed as part of settling this
+	 * execution (e.g. SIGINT was ignored and we escalated to shutdown, or the
+	 * kernel died unexpectedly). When false, the kernel remains reusable.
+	 */
+	kernelKilled?: boolean;
 }
 
 export interface KernelShutdownResult {
@@ -162,6 +170,7 @@ interface PendingExecution {
 	cancelled: boolean;
 	timedOut: boolean;
 	stdinRequested: boolean;
+	kernelKilled: boolean;
 	settled: boolean;
 	escalationTimer?: NodeJS.Timeout;
 }
@@ -222,7 +231,7 @@ export class PythonKernel {
 		kernel.#exitedPromise = proc.exited;
 		void kernel.#exitedPromise.then(code => {
 			kernel.#alive = false;
-			kernel.#abortPendingExecutions(`Python kernel exited with code ${code}`);
+			kernel.#abortPendingExecutions(`Python kernel exited with code ${code}`, { kernelKilled: true });
 		});
 
 		kernel.#startReader(proc.stdout as ReadableStream<Uint8Array>);
@@ -261,6 +270,7 @@ export class PythonKernel {
 			timedOut: false,
 			stdinRequested: false,
 			settled: false,
+			kernelKilled: false,
 		};
 		this.#pending.set(msgId, pending);
 
@@ -276,6 +286,7 @@ export class PythonKernel {
 				cancelled: pending.cancelled,
 				timedOut: pending.timedOut,
 				stdinRequested: pending.stdinRequested,
+				kernelKilled: pending.kernelKilled,
 			});
 		};
 
@@ -287,9 +298,12 @@ export class PythonKernel {
 				logger.warn("Python runner did not respond to SIGINT; terminating subprocess", {
 					kernelId: this.id,
 				});
-				// `shutdown()` aborts pending executions immediately and escalates to
-				// SIGTERM/SIGKILL, so the host queue unblocks even if the runner is
-				// stuck in a non-interruptible state.
+				// SIGINT was ignored; mark the cell as kernel-killed so callers can
+				// surface the harsher recovery message. `shutdown()` aborts pending
+				// executions immediately and escalates to SIGTERM/SIGKILL, so the
+				// host queue unblocks even if the runner is stuck in a
+				// non-interruptible state.
+				pending.kernelKilled = true;
 				void this.shutdown();
 			}, INTERRUPT_ESCALATION_MS);
 			escalation.unref?.();
@@ -363,7 +377,7 @@ export class PythonKernel {
 		if (this.#shutdownConfirmed) return { confirmed: true };
 
 		this.#alive = false;
-		this.#abortPendingExecutions("Python kernel shutdown");
+		this.#abortPendingExecutions("Python kernel shutdown", { kernelKilled: true });
 
 		const timeoutMs = options?.timeoutMs ?? SHUTDOWN_GRACE_MS;
 		const proc = this.#proc;
@@ -410,10 +424,11 @@ export class PythonKernel {
 		return { confirmed };
 	}
 
-	#abortPendingExecutions(reason: string): void {
+	#abortPendingExecutions(reason: string, options?: { kernelKilled?: boolean }): void {
 		if (this.#pending.size === 0) return;
 		const pending = Array.from(this.#pending.values());
 		this.#pending.clear();
+		const kernelKilledDefault = options?.kernelKilled ?? false;
 		for (const entry of pending) {
 			if (entry.settled) continue;
 			entry.settled = true;
@@ -425,6 +440,7 @@ export class PythonKernel {
 				stdinRequested: entry.stdinRequested,
 				executionCount: entry.executionCount,
 				error: entry.error,
+				kernelKilled: entry.kernelKilled || kernelKilledDefault,
 			});
 		}
 	}
diff --git a/packages/coding-agent/test/core/python-executor-mapping.test.ts b/packages/coding-agent/test/core/python-executor-mapping.test.ts
index cc04c4f26..941baab99 100644
--- a/packages/coding-agent/test/core/python-executor-mapping.test.ts
+++ b/packages/coding-agent/test/core/python-executor-mapping.test.ts
@@ -21,7 +21,7 @@ describe("executePythonWithKernel mapping", () => {
 
 		expect(result.cancelled).toBe(true);
 		expect(result.exitCode).toBeUndefined();
-		expect(result.output).toContain("Command timed out after 5 seconds");
+		expect(result.output).toContain("eval cell timed out after 5s");
 	});
 
 	it("maps error status to non-zero exit code", async () => {
diff --git a/packages/coding-agent/test/core/python-executor-per-call.test.ts b/packages/coding-agent/test/core/python-executor-per-call.test.ts
index 1ea3ee5cc..14fb234d9 100644
--- a/packages/coding-agent/test/core/python-executor-per-call.test.ts
+++ b/packages/coding-agent/test/core/python-executor-per-call.test.ts
@@ -144,7 +144,7 @@ describe("executePython (per-call)", () => {
 
 		expect(result.cancelled).toBe(true);
 		expect(result.exitCode).toBeUndefined();
-		expect(result.output).toContain("Command timed out after 2 seconds");
+		expect(result.output).toContain("eval cell timed out after 2s");
 		expect(shutdownCalls).toBe(1);
 	});
 });
diff --git a/packages/coding-agent/test/core/python-executor-streaming.test.ts b/packages/coding-agent/test/core/python-executor-streaming.test.ts
index 2a64c3e19..c31695500 100644
--- a/packages/coding-agent/test/core/python-executor-streaming.test.ts
+++ b/packages/coding-agent/test/core/python-executor-streaming.test.ts
@@ -25,7 +25,7 @@ describe("executePythonWithKernel streaming", () => {
 
 		expect(result.cancelled).toBe(true);
 		expect(result.exitCode).toBeUndefined();
-		expect(result.output).toContain("Command timed out after 2 seconds");
+		expect(result.output).toContain("eval cell timed out after 2s");
 	});
 
 	it("sanitizes ANSI and carriage returns", async () => {
diff --git a/packages/coding-agent/test/core/python-executor-timeout.test.ts b/packages/coding-agent/test/core/python-executor-timeout.test.ts
index 358d2f8cc..de8603969 100644
--- a/packages/coding-agent/test/core/python-executor-timeout.test.ts
+++ b/packages/coding-agent/test/core/python-executor-timeout.test.ts
@@ -30,6 +30,6 @@ describe("executePythonWithKernel cancellation", () => {
 
 		expect(result.cancelled).toBe(true);
 		expect(result.exitCode).toBeUndefined();
-		expect(result.output).toContain("Command timed out after 5 seconds");
+		expect(result.output).toContain("eval cell timed out after 5s");
 	});
 });
diff --git a/packages/coding-agent/test/core/python-executor.result.test.ts b/packages/coding-agent/test/core/python-executor.result.test.ts
index c8d263315..fbaf54b32 100644
--- a/packages/coding-agent/test/core/python-executor.result.test.ts
+++ b/packages/coding-agent/test/core/python-executor.result.test.ts
@@ -30,7 +30,7 @@ describe("executePythonWithKernel result mapping", () => {
 
 		expect(result.exitCode).toBeUndefined();
 		expect(result.cancelled).toBe(true);
-		expect(result.output).toContain("Command timed out after 5 seconds");
+		expect(result.output).toContain("eval cell timed out after 5s");
 	});
 
 	it("maps kernel error status to exit code 1", async () => {
diff --git a/packages/coding-agent/test/core/python-executor.test.ts b/packages/coding-agent/test/core/python-executor.test.ts
index 76d4463a8..8f3a81c86 100644
--- a/packages/coding-agent/test/core/python-executor.test.ts
+++ b/packages/coding-agent/test/core/python-executor.test.ts
@@ -75,7 +75,7 @@ describe("executePythonWithKernel", () => {
 
 		expect(result.exitCode).toBeUndefined();
 		expect(result.cancelled).toBe(true);
-		expect(result.output).toContain("Command timed out after 4 seconds");
+		expect(result.output).toContain("eval cell timed out after 4s");
 	});
 
 	it("returns cancelled result without timeout annotation", async () => {