Skip to content

Fix stale cmux ssh pane resize: reconcile remote PTY size after arming SIGWINCH #5989

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
austinywang merged 9 commits into from
Jun 19, 2026
+49 −41
Merged

Fix stale cmux ssh pane resize: reconcile remote PTY size after arming SIGWINCH #5989

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
9 commits
Select commit Hold shift + click to select a range
b586e9c
Reconcile remote PTY size after arming SIGWINCH (fix stale cmux ssh r…
kylejcaron Jun 12, 2026
0cfeda6
Sample terminal size inside socketLock in sendSSHPTYResize
kylejcaron Jun 12, 2026
079c2fe
Merge remote-tracking branch 'origin/main' into fix-ssh-pty-resize-at…
austinywang Jun 19, 2026
dca0743
chore: split SSH PTY resize helper
austinywang Jun 19, 2026
f5fef7d
test: expect initial SSH PTY resize
austinywang Jun 19, 2026
6346d67
Merge remote-tracking branch 'origin/main' into fix-ssh-pty-resize-at…
austinywang Jun 19, 2026
7097d8a
chore: keep SSH PTY resize sender local
austinywang Jun 19, 2026
c0a2ee5
Merge remote-tracking branch 'origin/main' into fix-ssh-pty-resize-at…
austinywang Jun 19, 2026
b84a0ee
Merge remote-tracking branch 'origin/main' into fix-ssh-pty-resize-at…
austinywang Jun 19, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions CLI/SSHPTYResizeMonitor.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,11 @@ actor SSHPTYResizeMonitor {
}
}

nonisolated func requestCurrentResize() {
let size = CMUXCLI.currentCLITerminalSize()
eventContinuation.yield((size: size, force: true))
}

nonisolated func cancel() {
source.cancel()
eventContinuation.finish()
Expand Down
7 changes: 7 additions & 0 deletions CLI/cmux.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -11336,6 +11336,13 @@ struct CMUXCLI {
)
defer { resizeMonitor.cancel() }

// Reconcile the remote PTY size once now that the SIGWINCH source is
// armed. The handshake captured the terminal size before the source
// existed; any SIGWINCH that arrived in that window was delivered with
// SIGWINCH's default disposition (ignore) and lost, with no later
// correction.
resizeMonitor.requestCurrentResize()

Task.detached(priority: .userInitiated) { [resizeMonitor, fd] in
var buffer = [UInt8](repeating: 0, count: 8192)
while true {
Expand Down
76 changes: 36 additions & 40 deletions cmuxTests/CLINotifyProcessIntegrationRegressionTests.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -3683,10 +3683,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
XCTAssertTrue(result.stdout.isEmpty, result.stdout)
XCTAssertTrue(result.stderr.contains("ssh-pty-attach: remote PTY start failed"), result.stderr)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_attach_end",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_attach_end"])
}

func testSSHPTYAttachBridgeEOFWhileSessionRunsExitsWithoutSSHRetryStatus() throws {
Expand Down Expand Up @@ -3727,6 +3724,10 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
"attachment_id": surfaceId,
]
)
case "workspace.remote.pty_resize":
XCTAssertEqual(params["attachment_token"] as? String, "attach-token")
XCTAssertEqual(params["surface_id"] as? String, surfaceId)
return self.v2Response(id: id, ok: true, result: ["resized": true])
case "workspace.remote.pty_sessions":
return self.v2Response(
id: id,
Expand Down Expand Up @@ -3791,11 +3792,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
result.stderr
)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_sessions",
"workspace.remote.pty_detach",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_resize", "workspace.remote.pty_sessions", "workspace.remote.pty_detach"])
}

func testSSHPTYAttachBridgeEOFWhenSessionGoneClearsLocalState() throws {
Expand Down Expand Up @@ -3834,6 +3831,11 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
"attachment_id": surfaceId,
]
)
case "workspace.remote.pty_resize":
let params = payload["params"] as? [String: Any] ?? [:]
XCTAssertEqual(params["attachment_token"] as? String, "attach-token")
XCTAssertEqual(params["surface_id"] as? String, surfaceId)
return self.v2Response(id: id, ok: true, result: ["resized": true])
case "workspace.remote.pty_sessions":
return self.v2Response(
id: id,
Expand Down Expand Up @@ -3889,11 +3891,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
XCTAssertTrue(result.stdout.isEmpty, result.stdout)
XCTAssertTrue(result.stderr.isEmpty, result.stderr)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_sessions",
"workspace.remote.pty_attach_end",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_resize", "workspace.remote.pty_sessions", "workspace.remote.pty_attach_end"])
}

func testSSHPTYAttachWithoutSurfaceDoesNotSendLocalAttachEnd() throws {
Expand Down Expand Up @@ -3937,6 +3935,10 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
"attachment_id": attachmentID ?? "attachment",
]
)
case "workspace.remote.pty_resize":
XCTAssertEqual(params["attachment_token"] as? String, "attach-token")
XCTAssertNil(params["surface_id"])
return self.v2Response(id: id, ok: true, result: ["resized": true])
case "workspace.remote.pty_sessions":
XCTAssertNil(params["surface_id"])
return self.v2Response(
Expand Down Expand Up @@ -3978,10 +3980,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
XCTAssertTrue(result.stdout.isEmpty, result.stdout)
XCTAssertTrue(result.stderr.isEmpty, result.stderr)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_sessions",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_resize", "workspace.remote.pty_sessions"])
}

func testSSHPTYAttachBridgeResetWhenSessionGoneClearsLocalState() throws {
Expand Down Expand Up @@ -4020,6 +4019,11 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
"attachment_id": surfaceId,
]
)
case "workspace.remote.pty_resize":
let params = payload["params"] as? [String: Any] ?? [:]
XCTAssertEqual(params["attachment_token"] as? String, "attach-token")
XCTAssertEqual(params["surface_id"] as? String, surfaceId)
return self.v2Response(id: id, ok: true, result: ["resized": true])
case "workspace.remote.pty_sessions":
return self.v2Response(
id: id,
Expand Down Expand Up @@ -4075,11 +4079,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
XCTAssertTrue(result.stdout.isEmpty, result.stdout)
XCTAssertTrue(result.stderr.isEmpty, result.stderr)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_sessions",
"workspace.remote.pty_attach_end",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_resize", "workspace.remote.pty_sessions", "workspace.remote.pty_attach_end"])
}

func testSSHPTYAttachWaitUsesCurrentTerminalSizeForBridgeHandshake() throws {
Expand Down Expand Up @@ -4151,6 +4151,12 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
"attachment_id": surfaceId,
]
)
case "workspace.remote.pty_resize":
let params = payload["params"] as? [String: Any] ?? [:]
XCTAssertEqual(params["attachment_token"] as? String, "attach-token")
XCTAssertEqual(params["cols"] as? Int, 132)
XCTAssertEqual(params["rows"] as? Int, 43)
return self.v2Response(id: id, ok: true, result: ["resized": true])
case "workspace.remote.pty_sessions":
return self.v2Response(id: id, ok: true, result: ["sessions": []])
case "workspace.remote.pty_attach_end":
Expand Down Expand Up @@ -4395,15 +4401,11 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
}
XCTAssertEqual(bridgeReady.wait(timeout: .now() + 5), .success)

var sawResize = false
for _ in 0..<10 {
Darwin.kill(process.processIdentifier, SIGWINCH)
if resizeRequestReceived.wait(timeout: .now() + 0.2) == .success {
sawResize = true
break
}
}
XCTAssertTrue(sawResize, "Expected ssh-pty-attach to issue a resize RPC after SIGWINCH")
XCTAssertEqual(
resizeRequestReceived.wait(timeout: .now() + 5),
.success,
"Expected ssh-pty-attach to issue its initial resize RPC after bridge ready"
)

closeBridge.signal()
wait(for: [bridgeHandled], timeout: 5)
Expand Down Expand Up @@ -4587,10 +4589,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
XCTAssertEqual(result.status, 1, result.stderr)
XCTAssertTrue(result.stderr.contains("ssh-pty-attach: missing session"), result.stderr)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_attach_end",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_attach_end"])
}

func testSSHPTYAttachRequireExistingSessionNotFoundFailsWithoutWaitRetry() throws {
Expand Down Expand Up @@ -4674,10 +4673,7 @@ final class CLINotifyProcessIntegrationRegressionTests: XCTestCase {
XCTAssertEqual(result.status, 1, result.stderr)
XCTAssertTrue(result.stderr.contains("persistent SSH PTY session is no longer running"), result.stderr)
let methods = state.snapshot().compactMap { self.jsonObject($0)?["method"] as? String }
XCTAssertEqual(methods, [
"workspace.remote.pty_bridge",
"workspace.remote.pty_attach_end",
])
XCTAssertEqual(methods, ["workspace.remote.pty_bridge", "workspace.remote.pty_attach_end"])
}

func testSSHSessionListAllWorkspacesReportsQueryErrors() throws {
Expand Down
2 changes: 1 addition & 1 deletion cmuxTests/CLINotifyProcessTestSupport.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -262,7 +262,7 @@ extension CLINotifyProcessIntegrationRegressionTests {
pending.append(buffer, count: count)
}

let payload: [String: Any] = ["type": "ready"]
let payload: [String: Any] = ["type": "ready", "attachment_token": "attach-token"]
guard var data = try? JSONSerialization.data(withJSONObject: payload, options: []) else { return }
data.append(0x0A)
data.withUnsafeBytes { rawBuffer in
Expand Down
Loading