diff --git a/.github/workflows/_build.yml b/.github/workflows/_build.yml
index 47b5b17b5e..43c52b052a 100644
--- a/.github/workflows/_build.yml
+++ b/.github/workflows/_build.yml
@@ -41,7 +41,9 @@ jobs:
             goarch: arm64
             cc: gcc
             cxx: g++
-          - os: macos-14
+          # The macOS minimum (14.0) is pinned in Makefile.cbm, not inherited
+          # from this runner's SDK, so both darwin binaries still start on macOS 14.
+          - os: macos-15
             goos: darwin
             goarch: arm64
             cc: cc
diff --git a/.github/workflows/_memwaste.yml b/.github/workflows/_memwaste.yml
index 174490db6c..09deb0c37e 100644
--- a/.github/workflows/_memwaste.yml
+++ b/.github/workflows/_memwaste.yml
@@ -115,7 +115,7 @@ jobs:
 
   event-macos:
     if: ${{ inputs.mode == 'full' }}
-    runs-on: macos-14
+    runs-on: macos-15
     timeout-minutes: 60
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
diff --git a/.github/workflows/_smoke.yml b/.github/workflows/_smoke.yml
index 1a4d4eb57c..96c47d44f1 100644
--- a/.github/workflows/_smoke.yml
+++ b/.github/workflows/_smoke.yml
@@ -33,7 +33,7 @@ jobs:
           CORE_UNIX='[
             {"os":"ubuntu-latest","goos":"linux","goarch":"amd64"},
             {"os":"ubuntu-24.04-arm","goos":"linux","goarch":"arm64"},
-            {"os":"macos-14","goos":"darwin","goarch":"arm64"},
+            {"os":"macos-15","goos":"darwin","goarch":"arm64"},
             {"os":"macos-15-intel","goos":"darwin","goarch":"amd64"}
           ]'
           # Broad legs reuse existing goos/goarch artifacts on additional OS
@@ -47,9 +47,10 @@ jobs:
           # (ubuntu-22.04 / 22.04-arm). So the dynamic broad legs stay on
           # forward-compatible OSes only (macOS); running the dynamic binary on
           # ubuntu-22.04 would fail Phase 1 (glibc too old), not a real regression.
-          BROAD_UNIX='[
-            {"os":"macos-15","goos":"darwin","goarch":"arm64"}
-          ]'
+          # Empty since the move off macos-14 (retired 2026-11-02): the darwin-arm64
+          # artifact is now built AND smoked on macos-15, the core leg, which was
+          # this broad leg.
+          BROAD_UNIX='[]'
           CORE_WIN='[{"os":"windows-latest","arch":"amd64"}]'
           # windows-11-arm now runs the NATIVE arm64 binary (build-windows-arm64),
           # not the x86_64 binary under emulation — we smoke the artifact we ship.
diff --git a/.github/workflows/_soak.yml b/.github/workflows/_soak.yml
index abf365f541..63c3ec51e7 100644
--- a/.github/workflows/_soak.yml
+++ b/.github/workflows/_soak.yml
@@ -44,7 +44,7 @@ jobs:
             goarch: arm64
             cc: gcc
             cxx: g++
-          - os: macos-14
+          - os: macos-15
             goos: darwin
             goarch: arm64
             cc: cc
@@ -335,7 +335,7 @@ jobs:
             goarch: arm64
             cc: gcc
             cxx: g++
-          - os: macos-14
+          - os: macos-15
             goos: darwin
             goarch: arm64
             cc: cc
diff --git a/.github/workflows/_test.yml b/.github/workflows/_test.yml
index 39baa516c1..55a8bf6085 100644
--- a/.github/workflows/_test.yml
+++ b/.github/workflows/_test.yml
@@ -57,18 +57,21 @@ jobs:
         run: |
           # Every CORE leg is tagged with the lane (scripts/ci/select-lanes.sh)
           # it serves; the tag is what lane selection filters on below.
+          # The lane names unix-macos14 and tsan-mac are kept as lane keys
+          # (select-lanes.sh, ci-ok and the lane contracts key on them); both
+          # run on macos-15 because GitHub retires the macos-14 image on 2026-11-02.
           CORE_UNIX='[
             {"os":"ubuntu-latest","cc":"gcc","cxx":"g++","lane":"unix-x86"},
             {"os":"ubuntu-24.04-arm","cc":"gcc","cxx":"g++","lane":"unix-arm64"},
-            {"os":"macos-14","cc":"cc","cxx":"c++","lane":"unix-macos14"},
+            {"os":"macos-15","cc":"cc","cxx":"c++","lane":"unix-macos14"},
             {"os":"macos-15-intel","cc":"cc","cxx":"c++","lane":"unix-macos-intel"}
           ]'
           # Broad matrix legs are REQUIRED gates (no optional/continue-on-error
           # escape hatches): the release dry run must be all-green, every platform.
+          # macos-15 is the CORE macOS arm64 leg now, so it is not repeated here.
           BROAD_UNIX='[
             {"os":"ubuntu-22.04","cc":"gcc","cxx":"g++"},
-            {"os":"ubuntu-22.04-arm","cc":"gcc","cxx":"g++"},
-            {"os":"macos-15","cc":"cc","cxx":"c++"}
+            {"os":"ubuntu-22.04-arm","cc":"gcc","cxx":"g++"}
           ]'
           # Each Windows leg pins the msys2 environment + package arch to the
           # RUNNER architecture so the build is native, never emulated:
@@ -92,7 +95,7 @@ jobs:
           TSAN='[
             {"os":"ubuntu-latest","cc":"clang","cxx":"clang++","lane":"tsan-x86"},
             {"os":"ubuntu-24.04-arm","cc":"clang","cxx":"clang++","lane":"tsan-arm"},
-            {"os":"macos-14","cc":"cc","cxx":"c++","lane":"tsan-mac"}
+            {"os":"macos-15","cc":"cc","cxx":"c++","lane":"tsan-mac"}
           ]'
           # Lane selection. "all" (dry run, release) keeps every leg and drops
           # the tags, so those matrices -- and their job names -- stay exactly
diff --git a/.github/workflows/bug-repro.yml b/.github/workflows/bug-repro.yml
index 2910606d03..e3e1a647a6 100644
--- a/.github/workflows/bug-repro.yml
+++ b/.github/workflows/bug-repro.yml
@@ -40,7 +40,7 @@ jobs:
             group: linux
             cc: gcc
             cxx: g++
-          - os: macos-14
+          - os: macos-15
             group: macos
             cc: cc
             cxx: c++
diff --git a/.github/workflows/cache-warm.yml b/.github/workflows/cache-warm.yml
index ff15fbb1a7..bca57b23b7 100644
--- a/.github/workflows/cache-warm.yml
+++ b/.github/workflows/cache-warm.yml
@@ -27,7 +27,7 @@ jobs:
         include:
           - { os: ubuntu-latest, cc: gcc, cxx: g++ }
           - { os: ubuntu-24.04-arm, cc: gcc, cxx: g++ }
-          - { os: macos-14, cc: cc, cxx: c++ }
+          - { os: macos-15, cc: cc, cxx: c++ }
           - { os: macos-15-intel, cc: cc, cxx: c++ }
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index 81a838e804..aade2b93da 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -175,7 +175,7 @@ jobs:
           cat "$RUNNER_TEMP/selection.txt" >> "$GITHUB_OUTPUT"
           # pr-smoke's legs, each tagged with its lane (kept in the job name,
           # where ci-ok reads it back); the job gets the selected ones.
-          SMOKE='[{"os":"ubuntu-latest","lane":"smoke-ubuntu"},{"os":"macos-14","lane":"smoke-mac"},{"os":"windows-latest","lane":"smoke-win"}]'
+          SMOKE='[{"os":"ubuntu-latest","lane":"smoke-ubuntu"},{"os":"macos-15","lane":"smoke-mac"},{"os":"windows-latest","lane":"smoke-win"}]'
           LANES=$(sed -n 's/^lanes=//p' "$RUNNER_TEMP/selection.txt")
           echo "smoke={\"include\":$(jq -c --argjson sel "$LANES" 'map(select(.lane | IN($sel[])))' <<< "$SMOKE")}" >> "$GITHUB_OUTPUT"
           # The CodeQL legs, tagged the same way (codeql.yml's full matrix has
@@ -214,7 +214,7 @@ jobs:
         run: sudo apt-get update && sudo apt-get install -y zlib1g-dev ccache
 
       - name: Install ccache (macOS)
-        if: matrix.os == 'macos-14'
+        if: matrix.os == 'macos-15'
         run: command -v ccache >/dev/null 2>&1 || brew install ccache
 
       - uses: msys2/setup-msys2@66cd2cce69caa17b53920067426061ca1de3a884 # v2
@@ -254,7 +254,7 @@ jobs:
           SMOKE_REQUIRE_WRAPPERS: "1"
 
       - name: Build prod + smoke (macOS)
-        if: matrix.os == 'macos-14'
+        if: matrix.os == 'macos-15'
         run: |
           scripts/build.sh CC=cc CXX=c++
           codesign --sign - --force build/c/codebase-memory-mcp
diff --git a/.github/workflows/smoke.yml b/.github/workflows/smoke.yml
index e9b4f93575..2de8e1b8e4 100644
--- a/.github/workflows/smoke.yml
+++ b/.github/workflows/smoke.yml
@@ -39,9 +39,6 @@ jobs:
           - os: ubuntu-24.04-arm
             cc: gcc
             cxx: g++
-          - os: macos-14            # arm64
-            cc: cc
-            cxx: c++
           - os: macos-15            # arm64
             cc: cc
             cxx: c++
diff --git a/Makefile.cbm b/Makefile.cbm
index 3c73982925..12f0fe5c12 100644
--- a/Makefile.cbm
+++ b/Makefile.cbm
@@ -18,8 +18,24 @@
 # that use their own *_CFLAGS — and so it survives a command-line `CC=` override.
 # ARCHFLAGS is empty on Linux/Windows and for native direct `make` invocations,
 # leaving CC/CXX unchanged there.
-override CC := $(CC) $(ARCHFLAGS)
-override CXX := $(CXX) $(ARCHFLAGS)
+#
+# Minimum macOS version (Apple targets only). Without one, clang takes the
+# minimum from the SDK it compiles against (LC_BUILD_VERSION minos), so a
+# release built on a macos-15 runner would refuse to start on macOS 14. 14.0
+# keeps every macOS that could run a release built on the macos-14 runner
+# (retired 2026-11-02). A flag folded into the drivers like ARCHFLAGS, not an
+# exported MACOSX_DEPLOYMENT_TARGET: it reaches every compile AND link on every
+# build path (build.sh, test.sh, direct make) and is part of each command line.
+# Detected from the compiler's target, not the host, so a cross compiler run
+# on a Mac is left untouched.
+MACOS_MIN_VERSION := 14.0
+IS_APPLE_TARGET := $(shell echo | $(CC) $(ARCHFLAGS) -dM -E - 2>/dev/null | grep -q '__APPLE__' && echo yes || echo no)
+MACOS_MIN_FLAGS :=
+ifeq ($(IS_APPLE_TARGET),yes)
+MACOS_MIN_FLAGS := -mmacosx-version-min=$(MACOS_MIN_VERSION)
+endif
+override CC := $(CC) $(ARCHFLAGS) $(MACOS_MIN_FLAGS)
+override CXX := $(CXX) $(ARCHFLAGS) $(MACOS_MIN_FLAGS)
 
 # ── Common flags ─────────────────────────────────────────────────
 
diff --git a/tests/test_lane_gate_contract.sh b/tests/test_lane_gate_contract.sh
index 57e2cc12ee..f016f2e99d 100755
--- a/tests/test_lane_gate_contract.sh
+++ b/tests/test_lane_gate_contract.sh
@@ -49,7 +49,7 @@ t1_jobs() { # the jobs of a green T1 run; $1 = conclusion of the x86 leg
     job "lint / lint-mem" success
     job "test / setup-matrix" success
     job "test / test-unix (ubuntu-latest, gcc, g++, unix-x86, 1/1)" "$1"
-    job "test / test-unix (macos-14, cc, c++, unix-macos14, 1/1)" success
+    job "test / test-unix (macos-15, cc, c++, unix-macos14, 1/1)" success
     job "test / test-windows (windows-latest, CLANG64, x86_64, windows, 1/1)" success
     job "test / test-windows-guards" skipped
     job "test / test-package-wrappers" skipped
@@ -116,7 +116,7 @@ gate "a selection without the job list is red" 1 "$NEEDS_OK" "$T1" "$WORK/does-n
     job "lint / lint" success
     job "lint / lint-mem" success
     job "test / test-windows-guards" success
-    job "pr-smoke (macos-14, smoke-mac)" success
+    job "pr-smoke (macos-15, smoke-mac)" success
 } >"$WORK/guards-only"
 gate "windows-guards is not the windows leg" 1 "$NEEDS_OK" '["lint","lint-mem","security-static","windows"]' "$WORK/guards-only"
 gate "pr-smoke matrix name maps to its lane" 0 "$NEEDS_OK" '["lint","lint-mem","security-static","smoke-mac","windows-guards"]' "$WORK/guards-only"