Remove macOS from CI

.github/CONTRIBUTING.md

@@ -2,7 +2,10 @@
 
 This repository contains the libtmux gem suite. Installed-import
 tests establish package boundaries and execute consumer APIs and documentation
-recipes. Compatibility CI records the exact Ruby, tmux and operating-system cells.
+recipes. Compatibility CI records the exact Ruby and tmux cells on Linux.
+macOS is supported on a best-effort basis, and CI coverage for it is highly
+limited: no job runs there, so a macOS-only regression is not caught before
+merge.
 
 Read [AGENTS.md](../AGENTS.md) for change discipline and [WRITING.md](WRITING.md)
 for prose and commit conventions.
@@ -22,7 +25,7 @@ which tmux 3.2 clients cannot start; it also needs
 variable to `refused` or `supported` for the other version check tests, and
 they fail in CI when it is missing.
 The authored-shell tests use zsh's ZLE, `zsh/net/socket` and `zsh/system`
-modules. The Linux CI job installs zsh; the macOS runner supplies it.
+modules. The Linux CI job installs zsh.
 
 Install the pinned tool with mise:
 

.github/workflows/compatibility.yml

@@ -5,15 +5,6 @@ on:
     branches: [master]
   pull_request:
   workflow_dispatch:
-    inputs:
-      debug_enabled:
-        type: boolean
-        description: Open tmate on the macOS Ruby 4.0.7 / tmux 3.7c cell
-        default: false
-      native_only:
-        type: boolean
-        description: Run only the macOS Ruby 4.0.7 / tmux 3.7c cell without tmate
-        default: false
 
 permissions:
   contents: read
@@ -55,9 +46,9 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        platform: ${{ fromJSON(github.event_name == 'workflow_dispatch' && (inputs.debug_enabled || inputs.native_only) && '[{"system":"macos","runner":"macos-15"}]' || '[{"system":"linux","runner":"ubuntu-24.04"},{"system":"macos","runner":"macos-15"}]') }}
-        ruby: ${{ fromJSON(github.event_name == 'workflow_dispatch' && (inputs.debug_enabled || inputs.native_only) && '["4.0.7"]' || '["3.3.12","3.4.10","4.0.7"]') }}
-        tmux: ${{ fromJSON(github.event_name == 'workflow_dispatch' && (inputs.debug_enabled || inputs.native_only) && '["3.7c"]' || '["3.3a","3.4","3.5a","3.6","3.7c","3.8"]') }}
+        platform: [{system: linux, runner: ubuntu-24.04}]
+        ruby: ['3.3.12', '3.4.10', '4.0.7']
+        tmux: ['3.3a', '3.4', '3.5a', '3.6', '3.7c', '3.8']
     env:
       BUNDLE_FROZEN: 'true'
       LIBTMUX_VERSION_CHECK_EXPECT: supported
@@ -78,9 +69,6 @@ jobs:
         run: |
           sudo apt-get update
           sudo apt-get install --yes libevent-dev libncurses-dev bison pkg-config zsh
-      - name: Install macOS build dependencies
-        if: runner.os == 'macOS'
-        run: brew install libevent ncurses bison pkg-config jemalloc
       - name: Build the exact tmux release
         shell: bash
         run: |
@@ -92,47 +80,11 @@ jobs:
           ruby -rjson -rdigest -e 'expected = JSON.parse(File.read("scripts/tmux-releases.json")).fetch(ENV.fetch("TMUX_VERSION")); abort "tmux archive checksum mismatch" unless Digest::SHA256.file(ARGV.fetch(0)).hexdigest == expected' "$archive"
           tar -xzf "$archive" -C "$RUNNER_TEMP"
           configure_options=(--disable-utf8proc)
-          if [ "$RUNNER_OS" = macOS ]; then
-            PATH="$(brew --prefix bison)/bin:$PATH"
-            PKG_CONFIG_PATH="$(brew --prefix libevent)/lib/pkgconfig:$(brew --prefix ncurses)/lib/pkgconfig"
-            CPPFLAGS="-I$(brew --prefix libevent)/include -I$(brew --prefix ncurses)/include"
-            LDFLAGS="-L$(brew --prefix libevent)/lib -L$(brew --prefix ncurses)/lib"
-            if [ "$TMUX_VERSION" = 3.7c ]; then
-              PKG_CONFIG_PATH="$(brew --prefix jemalloc)/lib/pkgconfig:$PKG_CONFIG_PATH"
-              CPPFLAGS="-I$(brew --prefix jemalloc)/include $CPPFLAGS"
-              LDFLAGS="-L$(brew --prefix jemalloc)/lib $LDFLAGS"
-              configure_options+=(--enable-jemalloc)
-            fi
-            export PATH PKG_CONFIG_PATH CPPFLAGS LDFLAGS
-          fi
           cd "$RUNNER_TEMP/tmux-$TMUX_VERSION"
           ./configure --prefix="$RUNNER_TEMP/tmux-install" "${configure_options[@]}"
           make -j2
           make install
           test "$("$RUNNER_TEMP/tmux-install/bin/tmux" -V)" = "tmux $TMUX_VERSION"
-      - name: Trace native child retirement samples
-        if: ${{ always() && github.event_name == 'workflow_dispatch' && inputs.debug_enabled }}
-        continue-on-error: true
-        timeout-minutes: 2
-        shell: bash
-        run: |
-          mkdir -p build/native-process-trace
-          bundle exec ruby .github/scripts/trace-process.rb --compare-waits \
-            > build/native-process-trace/wait-comparison.json
-          # Keep every sample and failure; these diagnostics are not a test retry gate.
-          for sample in 1 2 3 4 5 6; do
-            if CHILD_TRACE="build/native-process-trace/sample-$sample.json" \
-              bundle exec ruby -Igems/libtmux/lib -r./.github/scripts/trace-process.rb \
-              -Itest test/unit/process_test.rb \
-              --name '/test_cancellation_escalates_and_reaps_a_child_ignoring_term|test_repeated_thread_cancellation_does_not_replace_the_first_failure/' \
-              > "build/native-process-trace/sample-$sample.log" 2>&1; then
-              status=0
-            else
-              status=$?
-            fi
-            printf '{"sample":%d,"exit_status":%d}\n' "$sample" "$status" \
-              >> build/native-process-trace/samples.jsonl
-          done
       - name: Run the complete cell
         timeout-minutes: 5
         run: >-
@@ -148,36 +100,6 @@ jobs:
           name: matrix-${{ matrix.platform.system }}-${{ matrix.ruby }}-${{ matrix.tmux }}
           path: build/matrix/
           if-no-files-found: warn
-      - name: Retain every native child retirement sample
-        if: ${{ always() && github.event_name == 'workflow_dispatch' && inputs.debug_enabled }}
-        continue-on-error: true
-        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
-        with:
-          name: native-process-trace
-          path: build/native-process-trace/
-          retention-days: 7
-          if-no-files-found: error
-      - name: Debug the selected macOS cell
-        id: debug
-        if: ${{ always() && github.event_name == 'workflow_dispatch' && inputs.debug_enabled && matrix.platform.system == 'macos' && matrix.ruby == '4.0.7' && matrix.tmux == '3.7c' }}
-        uses: mxschmitt/action-tmate@35b54afac29c97fb54faba5b513f8fbd1882f113 # v3
-        timeout-minutes: 10
-        with:
-          detached: true
-          limit-access-to-actor: true
-      - name: Save the restricted debug SSH address
-        if: ${{ always() && github.event_name == 'workflow_dispatch' && inputs.debug_enabled && steps.debug.outputs.ssh-address != '' }}
-        env:
-          TMATE_SSH_ADDRESS: ${{ steps.debug.outputs.ssh-address }}
-        run: printf '%s\n' "$TMATE_SSH_ADDRESS" > "$RUNNER_TEMP/tmate-ssh-address.txt"
-      - name: Retain the restricted debug connection
-        if: ${{ always() && github.event_name == 'workflow_dispatch' && inputs.debug_enabled && steps.debug.outputs.ssh-address != '' }}
-        uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
-        with:
-          name: tmate-connection
-          path: ${{ runner.temp }}/tmate-ssh-address.txt
-          retention-days: 1
-          if-no-files-found: error
 
   unsupported:
     name: Refuse tmux ${{ matrix.tmux }} before effects
@@ -276,7 +198,7 @@ jobs:
 
   report:
     name: All required cells
-    if: ${{ always() && !(github.event_name == 'workflow_dispatch' && (inputs.debug_enabled || inputs.native_only)) }}
+    if: ${{ always() }}
     needs: [cell, unsupported, development]
     runs-on: ubuntu-24.04
     timeout-minutes: 5

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## 0.1.0.alpha.3 (unreleased)
 
+- CI no longer runs macOS. macOS stays supported on a best-effort basis, and CI
+  coverage for it is highly limited, so a macOS-only regression is not caught
+  before merge. (#49)
+
 ## 0.1.0.alpha.2 (2026-10-18)
 
 Requires tmux 3.3a or newer, checked against the running daemon, and runs on

README.md

@@ -354,8 +354,9 @@ isolated installation and runs the recipes outside the checkout.
   minimum. A [server handle][server] checks the connected daemon's release, not
   the client's, and refuses an older daemon before any requested command runs.
 - **Linux, including WSL, and macOS.** The [compatibility workflow][compat]
-  runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a through 3.8 on Ubuntu 24.04 and
-  macOS 15.
+  runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a through 3.8 on Ubuntu 24.04.
+  macOS is supported on a best-effort basis, and CI coverage for it is highly
+  limited.
 - **tmux master and old daemons.** On Ubuntu the workflow also runs the suite
   against a pinned tmux master, and checks that tmux 3.0a, 3.1c, 3.2a and 3.3
   daemons are refused.

gems/libtmux-async/README.md

@@ -241,8 +241,9 @@ The contract is in [Control connections][behavior-control].
 - **Async 2.46.** The gem depends on `async` ~> 2.46.0 and the same version of
   `libtmux`.
 - **Linux, including WSL, and macOS.** The [compatibility workflow][compat]
-  runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a through 3.8 on Ubuntu 24.04 and
-  macOS 15, and retains per-revision results.
+  runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a through 3.8 on Ubuntu 24.04 and retains
+  per-revision results. macOS is supported on a best-effort basis, and CI
+  coverage for it is highly limited.
 
 ## Documentation
 

gems/libtmux-mcp/README.md

@@ -335,7 +335,8 @@ pass the invitation to [`accept_shell`][mcp-application-accept_shell].
   and says to upgrade tmux and restart the server.
 - **Linux, including WSL, and macOS.** The core
   [compatibility workflow][compat] runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a
-  through 3.8 on Ubuntu 24.04 and macOS 15.
+  through 3.8 on Ubuntu 24.04. macOS is supported on a best-effort basis, and
+  CI coverage for it is highly limited.
 
 ## Documentation
 

gems/libtmux-workspace/README.md

@@ -380,7 +380,8 @@ values by design.
   `error.kind` is `tmux_unsupported`.
 - **Linux, including WSL, and macOS.** The library and the command share the
   core [compatibility workflow][compat]: Ruby 3.3, 3.4 and 4.0 with tmux 3.3a
-  through 3.8 on Ubuntu 24.04 and macOS 15, with per-revision results.
+  through 3.8 on Ubuntu 24.04, with per-revision results. macOS is supported on
+  a best-effort basis, and CI coverage for it is highly limited.
 - **History limit.** On tmux 3.3a to 3.6 the reused initial pane keeps the
   global `history-limit`. Set the server's global value before you apply to
   get one history size.

gems/libtmux/README.md

@@ -732,8 +732,9 @@ server and lists every option.
   [server handle][server] checks the connected daemon's release before it sends
   a command, and refuses an older daemon even when its client is newer.
 - **Linux, including WSL, and macOS.** The [compatibility workflow][compat]
-  runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a through 3.8 on Ubuntu 24.04 and
-  macOS 15.
+  runs Ruby 3.3, 3.4 and 4.0 with tmux 3.3a through 3.8 on Ubuntu 24.04.
+  macOS is supported on a best-effort basis, and CI coverage for it is highly
+  limited.
 - **tmux master and old daemons.** On Ubuntu the workflow also runs the suite
   against a pinned tmux master, and checks that tmux 3.0a, 3.1c, 3.2a and 3.3
   daemons are refused.

scripts/matrix

@@ -10,7 +10,7 @@ require "open3"
 module CompatibilityMatrix
   RUBIES = %w[3.3.12 3.4.10 4.0.7].freeze
   TMUXES = %w[3.3a 3.4 3.5a 3.6 3.7c 3.8].freeze
-  SYSTEMS = %w[linux macos].freeze
+  SYSTEMS = %w[linux].freeze
   ROOT = File.expand_path("..", __dir__)
 
   def self.cells
@@ -34,7 +34,7 @@ module CompatibilityMatrix
   end
 
   def self.execute(cell, rubies, tmuxes, directory)
-    host = RUBY_PLATFORM.include?("linux") ? "linux" : RUBY_PLATFORM.include?("darwin") ? "macos" : "unsupported"
+    host = RUBY_PLATFORM.include?("linux") ? "linux" : "unsupported"
     return cell.merge("status" => "MISSING_RUNNER") unless host == cell.fetch("os")
 
     ruby, tmux = rubies[cell.fetch("ruby")], tmuxes[cell.fetch("tmux")]

test/unit/compatibility_workflow_test.rb

@@ -22,4 +22,17 @@ def test_supported_cells_and_the_development_build_name_their_lane
       assert_equal "supported", WORKFLOW.fetch("jobs").fetch(name).fetch("env").fetch("LIBTMUX_VERSION_CHECK_EXPECT"), name
     end
   end
+
+  def test_no_job_runs_on_macos
+    runners = WORKFLOW.fetch("jobs").flat_map do |_name, job|
+      [job.fetch("runs-on"), *job.dig("strategy", "matrix", "platform")&.map { |platform| platform.fetch("runner") }]
+    end
+    refute_empty runners
+    runners.each { |runner| refute_match(/macos/i, runner.to_s) }
+    assert_equal ["linux"], CompatibilityWorkflowTest.platform_systems
+  end
+
+  def self.platform_systems
+    WORKFLOW.dig("jobs", "cell", "strategy", "matrix", "platform").map { |platform| platform.fetch("system") }
+  end
 end

test/unit/matrix_test.rb

@@ -20,6 +20,7 @@ def test_plan_preserves_all_required_cells_and_cannot_claim_missing_cells_pass
     assert_equal "PARTIAL", report.fetch("status")
     assert report.fetch("cells").all? { |cell| cell.fetch("status") == "UNVERIFIED" }
     assert_equal %w[3.3a 3.4 3.5a 3.6 3.7c 3.8], report.fetch("cells").map { |cell| cell.fetch("tmux") }.uniq
+    assert_equal ["linux"], report.fetch("cells").map { |cell| cell.fetch("os") }.uniq
     assert_equal ["positive_native_identity"], report.fetch("cells").map { |cell| cell["process_bound_mcp"] }.uniq
     output, _, status = Open3.capture3(Gem.ruby, path, "--require-all")
     refute status.success?
@@ -83,8 +84,8 @@ def test_failed_identity_probe_cannot_dispatch_the_suite
       File.write(ruby, "#!/bin/sh\nif [ \"$1\" = --disable=gems ]; then printf 4.0.7; else touch '#{marker}'; exit 7; fi\n")
       File.write(tmux, "#!/bin/sh\nprintf 'tmux 3.7c\\n'\nexit 1\n")
       [ruby, tmux].each { |path| File.chmod(0o700, path) }
-      os = RUBY_PLATFORM.include?("darwin") ? "macos" : "linux"
-      cell = CompatibilityMatrix.cells.find { |item| item.fetch("id") == "#{os}/4.0.7/3.7c" }
+      skip "the matrix runs on Linux only" unless RUBY_PLATFORM.include?("linux")
+      cell = CompatibilityMatrix.cells.find { |item| item.fetch("id") == "linux/4.0.7/3.7c" }
       result = CompatibilityMatrix.execute(cell, {"4.0.7" => ruby}, {"3.7c" => tmux}, directory)
       assert_equal "WRONG_TOOLCHAIN", result.fetch("status")
       refute File.exist?(marker)