diff --git a/Sources/Container-Compose/Commands/ComposeUp.swift b/Sources/Container-Compose/Commands/ComposeUp.swift
index d42efd7..b158212 100644
--- a/Sources/Container-Compose/Commands/ComposeUp.swift
+++ b/Sources/Container-Compose/Commands/ComposeUp.swift
@@ -1253,24 +1253,38 @@ public struct ComposeUp: AsyncParsableCommand, @unchecked Sendable {
         let retries = max(healthcheck.retries ?? 3, 1)
         let interval = Healthcheck.parseDuration(healthcheck.interval, default: 30)
         let startPeriod = Healthcheck.parseDuration(healthcheck.start_period, default: 0)
+        let timeout = Healthcheck.parseDuration(healthcheck.timeout, default: 30)
 
-        if startPeriod > 0 {
-            try await Task.sleep(nanoseconds: UInt64(startPeriod * 1_000_000_000))
-        }
-
-        for attempt in 1...retries {
-            let exitCode = try await streamCommand(
+        @Sendable func probeSucceeded() async throws -> Bool {
+            try await streamCommand(
                 "container",
                 args: ["exec", containerName] + execArguments,
+                timeout: timeout,
                 onStdout: { _ in },
                 onStderr: { _ in }
-            )
-            if exitCode == 0 {
+            ) == 0
+        }
+
+        // Compose `start_period` is a grace window, not a delay: probes run
+        // during it and their failures do not consume the retry budget, and the
+        // first success ends the wait immediately.
+        if startPeriod > 0 {
+            let deadline = ContinuousClock.now.advanced(by: .seconds(startPeriod))
+            while ContinuousClock.now < deadline {
+                if try await probeSucceeded() {
+                    return
+                }
+                try await Task.sleep(for: .seconds(interval))
+            }
+        }
+
+        for attempt in 1...retries {
+            if try await probeSucceeded() {
                 return
             }
 
             if attempt < retries {
-                try await Task.sleep(nanoseconds: UInt64(interval * 1_000_000_000))
+                try await Task.sleep(for: .seconds(interval))
             }
         }
 
@@ -1481,6 +1495,7 @@ extension ComposeUp {
     func streamCommand(
         _ command: String,
         args: [String] = [],
+        timeout: TimeInterval? = nil,
         onStdout: @escaping (@Sendable (String) -> Void),
         onStderr: @escaping (@Sendable (String) -> Void)
     ) async throws -> Int32 {
@@ -1526,6 +1541,16 @@ extension ComposeUp {
 
             do {
                 try process.run()
+                if let timeout, timeout > 0 {
+                    // Docker treats a check that overruns `timeout` as one failed
+                    // attempt, not as a hang. Terminating the child makes the
+                    // termination handler fire with a non-zero status, so the
+                    // caller sees a normal failure.
+                    DispatchQueue.global().asyncAfter(deadline: .now() + timeout) { [weak process] in
+                        guard let process, process.isRunning else { return }
+                        process.terminate()
+                    }
+                }
             } catch {
                 continuation.resume(throwing: error)
             }
diff --git a/Tests/Container-Compose-StaticTests/HealthcheckTimeoutTests.swift b/Tests/Container-Compose-StaticTests/HealthcheckTimeoutTests.swift
new file mode 100644
index 0000000..5b6c462
--- /dev/null
+++ b/Tests/Container-Compose-StaticTests/HealthcheckTimeoutTests.swift
@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2025 Morris Richman and the Container-Compose project authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Testing
+import Foundation
+@testable import ContainerComposeCore
+
+@Suite("Healthcheck Timeout Tests")
+struct HealthcheckTimeoutTests {
+
+    /// `healthcheck.timeout` is only useful if an overrunning probe is actually
+    /// killed. Without the timeout the child below runs for its full 30s and
+    /// exits 0, so this test fails on both counts.
+    @Test("streamCommand terminates a child that overruns its timeout")
+    func streamCommandHonoursTimeout() async throws {
+        let composeUp = try ComposeUp.parse(["-d", "--cwd", NSTemporaryDirectory()])
+
+        let start = ContinuousClock.now
+        let exitCode = try await composeUp.streamCommand(
+            "sleep",
+            args: ["30"],
+            timeout: 1,
+            onStdout: { _ in },
+            onStderr: { _ in }
+        )
+        let elapsed = ContinuousClock.now - start
+
+        // Generous window: the point is "well under 30s", not millisecond accuracy.
+        #expect(elapsed < .seconds(15))
+        #expect(exitCode != 0)
+    }
+
+    /// A probe that finishes inside its timeout must be reported verbatim.
+    @Test("streamCommand leaves a fast child alone")
+    func streamCommandDoesNotKillFastChild() async throws {
+        let composeUp = try ComposeUp.parse(["-d", "--cwd", NSTemporaryDirectory()])
+
+        let exitCode = try await composeUp.streamCommand(
+            "true",
+            args: [],
+            timeout: 10,
+            onStdout: { _ in },
+            onStderr: { _ in }
+        )
+
+        #expect(exitCode == 0)
+    }
+
+    /// `timeout` has a Compose default of 30s; an omitted value must not be
+    /// read as "no timeout".
+    @Test("Omitted healthcheck timeout falls back to the Compose default")
+    func omittedTimeoutUsesDefault() throws {
+        let healthcheck = Healthcheck(test: ["CMD", "true"])
+        #expect(Healthcheck.parseDuration(healthcheck.timeout, default: 30) == 30)
+    }
+}