diff --git a/MODULE.bazel b/MODULE.bazel
index f1a0f2cd..109d909d 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -39,7 +39,7 @@ bazel_dep(name = "apple_support", version = "2.10.1")
 
 # WASM builds (//wasm:*, //web:dds_web_wasm). If you bump this version,
 # rebuild and run web/update_wasm.sh; see docs/wasm_build.md and patch_web_wasm.py.
-bazel_dep(name = "emsdk", version = "5.0.7")
+bazel_dep(name = "emsdk", version = "6.0.12")
 # Java bindings (//jni:*). Provides the hermetic remote JDK used to build and run
 # the FFM (java.lang.foreign) smoke test. rules_java 9.9.0 registers remotejdk_21
 # and remotejdk_25; we pin JDK 25 (>= 22, so the Foreign Function & Memory API is
@@ -51,14 +51,14 @@ bazel_dep(name = "rules_java", version = "9.9.0")
 bazel_dep(name = "rules_jvm_external", version = "7.1")
 
 # Prefer GitHub, fall back to codeload CDN on transient timeouts (see CI flakes).
-# Integrity and strip_prefix match BCR emsdk 5.0.7 source.json.
+# Integrity and strip_prefix match BCR emsdk 6.0.12 source.json.
 archive_override(
     module_name = "emsdk",
-    integrity = "sha256-Jm30uWRN3hgwOvBdzn0EhUJzsLtSckbLf7aglZF3TM8=",
-    strip_prefix = "emsdk-5.0.7/bazel",
+    integrity = "sha256-TdOYQqDiy+O4KYeVdfuz+nArIkpf1LiYxHaMADVCJPk=",
+    strip_prefix = "emsdk-6.0.12/bazel",
     urls = [
-        "https://github.com/emscripten-core/emsdk/archive/refs/tags/5.0.7.tar.gz",
-        "https://codeload.github.com/emscripten-core/emsdk/tar.gz/refs/tags/5.0.7",
+        "https://github.com/emscripten-core/emsdk/archive/refs/tags/6.0.12.tar.gz",
+        "https://codeload.github.com/emscripten-core/emsdk/tar.gz/refs/tags/6.0.12",
     ],
 )
 
diff --git a/MODULE.bazel.lock b/MODULE.bazel.lock
index 2ac32500..6deee378 100644
--- a/MODULE.bazel.lock
+++ b/MODULE.bazel.lock
@@ -296,15 +296,18 @@
   "moduleExtensions": {
     "@@emsdk+//:emscripten_cache.bzl%emscripten_cache": {
       "general": {
-        "bzlTransitiveDigest": "uqDvXmpTNqW4+ie/Fk+xC3TrFrKvL+9hNtoP51Kt2oo=",
-        "usagesDigest": "pWzD9zlSoLlTg9KHHx+GNAE4f/zuf6Hiv5i/aMApD/U=",
+        "bzlTransitiveDigest": "3DgiP8fPZPy6qdtRGjf4cPNZFohfnP8gP3DSqOJ/bTQ=",
+        "usagesDigest": "j0qhTD5sk+iB1IrfY4adqZMEU79AbIp+5ZBSsKlRbas=",
         "recordedInputs": [],
         "generatedRepoSpecs": {
           "emscripten_cache": {
             "repoRuleId": "@@emsdk+//:emscripten_cache.bzl%_emscripten_cache_repository",
             "attributes": {
               "configuration": [],
-              "targets": []
+              "targets": [],
+              "prebuilt_cache_url": "",
+              "prebuilt_cache_sha256": "",
+              "prebuilt_cache_strip_prefix": ""
             }
           }
         }
@@ -312,8 +315,8 @@
     },
     "@@emsdk+//:emscripten_deps.bzl%emscripten_deps": {
       "general": {
-        "bzlTransitiveDigest": "EJqXFpA5GJ8rvygFWFdlw8H9g/+nTCLJKMvuE73WaXU=",
-        "usagesDigest": "wvQRffIp8pEJeKXankBKEQBAOCI8HTtmw9TvnW7/e1c=",
+        "bzlTransitiveDigest": "W3qo734P/T6JS0ckkD5z9s0NxMKjqjFivtNQNDg/Pzk=",
+        "usagesDigest": "ylRE9xa02aOPgtPFSFWXvW46yPVlgjW9ShIVIqKd84M=",
         "recordedInputs": [
           "REPO_MAPPING:bazel_features+,bazel_features_globals bazel_features++version_extension+bazel_features_globals",
           "REPO_MAPPING:bazel_features+,bazel_features_version bazel_features++version_extension+bazel_features_version",
@@ -333,51 +336,51 @@
           "emscripten_bin_linux": {
             "repoRuleId": "@@bazel_tools//tools/build_defs/repo:http.bzl%http_archive",
             "attributes": {
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               "type": "tar.xz",
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+              "url": "https://storage.googleapis.com/webassembly/emscripten-releases-builds/linux/6e9f6885cb17a3d6c8fd488a5cff730f50aba61d/wasm-binaries.tar.xz"
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+              "build_file_content": "\npackage(default_visibility = ['//visibility:public'])\n\nfilegroup(\n    name = \"all\",\n    srcs = glob([\"**\"]),\n)\n\nfilegroup(\n    name = \"includes\",\n    srcs = glob([\n        \"emscripten/cache/sysroot/include/c++/v1/**\",\n        \"emscripten/cache/sysroot/include/compat/**\",\n        \"emscripten/cache/sysroot/include/**\",\n        \"lib/clang/**/include/**\",\n    ]),\n)\n\nfilegroup(\n    name = \"builtin_cache\",\n    srcs = glob([\n        \"emscripten/cache/**\",\n    ]),\n)\n\nfilegroup(\n    name = \"emcc_common\",\n    srcs = [\n        \"emscripten/emcc.py\",\n        \"emscripten/em++.py\",\n        \"emscripten/embuilder.py\",\n        \"emscripten/emscripten-version.txt\",\n        \"emscripten/cache/sysroot_install.stamp\",\n        \"emscripten/src/settings.js\",\n        \"emscripten/src/settings_internal.js\",\n    ] + glob(\n        include = [\n            \"emscripten/third_party/**\",\n            \"emscripten/tools/**\",\n        ],\n        exclude = [\n            \"**/__pycache__/**\",\n        ],\n    ),\n)\n\nfilegroup(\n    name = \"compiler_files\",\n    srcs = [\n        \"bin/clang\",\n        \"bin/clang++\",\n        \":emcc_common\",\n        \":includes\",\n    ],\n)\n\nfilegroup(\n    name = \"linker_files\",\n    srcs = [\n        \"bin/clang\",\n        \"bin/llvm-ar\",\n        \"bin/llvm-dwarfdump\",\n        \"bin/llvm-nm\",\n        \"bin/llvm-objcopy\",\n        \"bin/wasm-ctor-eval\",\n        \"bin/wasm-emscripten-finalize\",\n        \"bin/wasm-ld\",\n        \"bin/wasm-metadce\",\n        \"bin/wasm-opt\",\n        \"bin/wasm-split\",\n        \"bin/wasm2js\",\n        \":emcc_common\",\n    ] + glob(\n        include = [\n            \"emscripten/cache/sysroot/lib/**\",\n            \"emscripten/node_modules/**\",\n            \"emscripten/src/**\",\n        ],\n    ),\n)\n\nfilegroup(\n    name = \"ar_files\",\n    srcs = [\n        \"bin/llvm-ar\",\n        \"emscripten/emar.py\",\n        \"emscripten/emscripten-version.txt\",\n        \"emscripten/src/settings.js\",\n        \"emscripten/src/settings_internal.js\",\n    ] + glob(\n        include = [\n            \"emscripten/tools/**\",\n        ],\n        exclude = [\n            \"**/__pycache__/**\",\n        ],\n    ),\n)\n",
+              "sha256": "8e91c0eca2b8728aa2babb32b805318eaf5e8d6652c6535163d0ea467a6d907c",
               "strip_prefix": "install",
               "type": "tar.xz",
-              "url": "https://storage.googleapis.com/webassembly/emscripten-releases-builds/mac/6cd98e86d7749ff98b82b7f2ae78eb4f01942788/wasm-binaries-arm64.tar.xz"
+              "url": "https://storage.googleapis.com/webassembly/emscripten-releases-builds/mac/6e9f6885cb17a3d6c8fd488a5cff730f50aba61d/wasm-binaries-arm64.tar.xz"
             }
           },
           "emscripten_bin_win": {
             "repoRuleId": "@@bazel_tools//tools/build_defs/repo:http.bzl%http_archive",
             "attributes": {
-              "build_file_content": "\npackage(default_visibility = ['//visibility:public'])\n\nfilegroup(\n    name = \"all\",\n    srcs = glob([\"**\"]),\n)\n\nfilegroup(\n    name = \"includes\",\n    srcs = glob([\n        \"emscripten/cache/sysroot/include/c++/v1/**\",\n        \"emscripten/cache/sysroot/include/compat/**\",\n        \"emscripten/cache/sysroot/include/**\",\n        \"lib/clang/**/include/**\",\n    ]),\n)\n\nfilegroup(\n    name = \"emcc_common\",\n    srcs = [\n        \"emscripten/emcc.py\",\n        \"emscripten/embuilder.py\",\n        \"emscripten/emscripten-version.txt\",\n        \"emscripten/cache/sysroot_install.stamp\",\n        \"emscripten/src/settings.js\",\n        \"emscripten/src/settings_internal.js\",\n    ] + glob(\n        include = [\n            \"emscripten/third_party/**\",\n            \"emscripten/tools/**\",\n        ],\n        exclude = [\n            \"**/__pycache__/**\",\n        ],\n    ),\n)\n\nfilegroup(\n    name = \"compiler_files\",\n    srcs = [\n        \"bin/clang.exe\",\n        \"bin/clang++.exe\",\n        \":emcc_common\",\n        \":includes\",\n    ],\n)\n\nfilegroup(\n    name = \"linker_files\",\n    srcs = [\n        \"bin/clang.exe\",\n        \"bin/llvm-ar.exe\",\n        \"bin/llvm-dwarfdump.exe\",\n        \"bin/llvm-nm.exe\",\n        \"bin/llvm-objcopy.exe\",\n        \"bin/wasm-ctor-eval.exe\",\n        \"bin/wasm-emscripten-finalize.exe\",\n        \"bin/wasm-ld.exe\",\n        \"bin/wasm-metadce.exe\",\n        \"bin/wasm-opt.exe\",\n        \"bin/wasm-split.exe\",\n        \"bin/wasm2js.exe\",\n        \":emcc_common\",\n    ] + glob(\n        include = [\n            \"emscripten/cache/sysroot/lib/**\",\n            \"emscripten/node_modules/**\",\n            \"emscripten/src/**\",\n        ],\n    ),\n)\n\nfilegroup(\n    name = \"ar_files\",\n    srcs = [\n        \"bin/llvm-ar.exe\",\n        \"emscripten/emar.py\",\n        \"emscripten/emscripten-version.txt\",\n        \"emscripten/src/settings.js\",\n        \"emscripten/src/settings_internal.js\",\n    ] + glob(\n        include = [\n            \"emscripten/tools/**\",\n        ],\n        exclude = [\n            \"**/__pycache__/**\",\n        ],\n    ),\n)\n",
-              "sha256": "32995a98db21951cb7e84b4898b235ba57553c9f35eeaa158cfff052fab83856",
+              "build_file_content": "\npackage(default_visibility = ['//visibility:public'])\n\nfilegroup(\n    name = \"all\",\n    srcs = glob([\"**\"]),\n)\n\nfilegroup(\n    name = \"includes\",\n    srcs = glob([\n        \"emscripten/cache/sysroot/include/c++/v1/**\",\n        \"emscripten/cache/sysroot/include/compat/**\",\n        \"emscripten/cache/sysroot/include/**\",\n        \"lib/clang/**/include/**\",\n    ]),\n)\n\nfilegroup(\n    name = \"builtin_cache\",\n    srcs = glob([\n        \"emscripten/cache/**\",\n    ]),\n)\n\nfilegroup(\n    name = \"emcc_common\",\n    srcs = [\n        \"emscripten/emcc.py\",\n        \"emscripten/em++.py\",\n        \"emscripten/embuilder.py\",\n        \"emscripten/emscripten-version.txt\",\n        \"emscripten/cache/sysroot_install.stamp\",\n        \"emscripten/src/settings.js\",\n        \"emscripten/src/settings_internal.js\",\n    ] + glob(\n        include = [\n            \"emscripten/third_party/**\",\n            \"emscripten/tools/**\",\n        ],\n        exclude = [\n            \"**/__pycache__/**\",\n        ],\n    ),\n)\n\nfilegroup(\n    name = \"compiler_files\",\n    srcs = [\n        \"bin/clang.exe\",\n        \"bin/clang++.exe\",\n        \":emcc_common\",\n        \":includes\",\n    ],\n)\n\nfilegroup(\n    name = \"linker_files\",\n    srcs = [\n        \"bin/clang.exe\",\n        \"bin/llvm-ar.exe\",\n        \"bin/llvm-dwarfdump.exe\",\n        \"bin/llvm-nm.exe\",\n        \"bin/llvm-objcopy.exe\",\n        \"bin/wasm-ctor-eval.exe\",\n        \"bin/wasm-emscripten-finalize.exe\",\n        \"bin/wasm-ld.exe\",\n        \"bin/wasm-metadce.exe\",\n        \"bin/wasm-opt.exe\",\n        \"bin/wasm-split.exe\",\n        \"bin/wasm2js.exe\",\n        \":emcc_common\",\n    ] + glob(\n        include = [\n            \"emscripten/cache/sysroot/lib/**\",\n            \"emscripten/node_modules/**\",\n            \"emscripten/src/**\",\n        ],\n    ),\n)\n\nfilegroup(\n    name = \"ar_files\",\n    srcs = [\n        \"bin/llvm-ar.exe\",\n        \"emscripten/emar.py\",\n        \"emscripten/emscripten-version.txt\",\n        \"emscripten/src/settings.js\",\n        \"emscripten/src/settings_internal.js\",\n    ] + glob(\n        include = [\n            \"emscripten/tools/**\",\n        ],\n        exclude = [\n            \"**/__pycache__/**\",\n        ],\n    ),\n)\n",
+              "sha256": "51ac2e51a2c6eeba09fa04418496750662b5c1f022665814b0ee8f557c8328c9",
               "strip_prefix": "install",
               "type": "zip",
-              "url": "https://storage.googleapis.com/webassembly/emscripten-releases-builds/win/6cd98e86d7749ff98b82b7f2ae78eb4f01942788/wasm-binaries.zip"
+              "url": "https://storage.googleapis.com/webassembly/emscripten-releases-builds/win/6e9f6885cb17a3d6c8fd488a5cff730f50aba61d/wasm-binaries.zip"
             }
           }
         }
@@ -435,7 +438,7 @@
     "@@rules_nodejs+//nodejs:extensions.bzl%node": {
       "general": {
         "bzlTransitiveDigest": "4pUxCNc22K4I+6+4Nxu52Hur12tFRfa1JMsN5mdDv60=",
-        "usagesDigest": "vZ6azLX/KFnBVNfNqvqrt+aTI+qpRIspF5DmoxPiuUs=",
+        "usagesDigest": "2M7mMWUyvVHuprBgqKwNd7hq64IT77Mutbf9CGEsSqw=",
         "recordedInputs": [],
         "generatedRepoSpecs": {
           "nodejs_linux_amd64": {
diff --git a/docs/wasm_build.md b/docs/wasm_build.md
index 2dc7c11b..39b63cdb 100644
--- a/docs/wasm_build.md
+++ b/docs/wasm_build.md
@@ -17,7 +17,7 @@ The Emscripten SDK (emsdk) does NOT need to be manually installed. Bazel downloa
 
 WASM builds use the Bazel Central Registry package pinned in `MODULE.bazel`:
 
-- `bazel_dep(name = "emsdk", version = "5.0.7")` (Emscripten 5.0.x toolchain)
+- `bazel_dep(name = "emsdk", version = "6.0.12")` (Emscripten 6.0.x toolchain)
 
 If you upgrade `emsdk`, rebuild WASM targets and the DDS Web (`./web/update_wasm.sh`). The post-build script `web/patch_web_wasm.py` patches one generated `isFileURI` helper for browser/file URL safety; if Emscripten changes that line, update the regex in that script and this note.
 
@@ -159,7 +159,7 @@ For other experiments, copy built `.js` / `.wasm` files from `bazel-bin/wasm/` t
 
 `-flto` is applied at compile time (`DDS_CPPOPTS`) but deliberately **not** at
 link time. Passing `-flto` to the wasm link step was tried and reverted: the
-`emsdk 5.0.7` package pinned in `MODULE.bazel` ships a frozen, pre-built cache
+`emsdk` package pinned in `MODULE.bazel` (checked again at 6.0.12) ships a frozen, pre-built cache
 containing only non-LTO system libraries, and requesting link-time LTO makes
 Emscripten require LTO-bitcode variants of core sysroot libraries (e.g.
 `libprintf_long_double`) that the frozen cache can't build on demand inside
diff --git a/library/tests/dtest.cpp b/library/tests/dtest.cpp
index cfc6ad51..e4b04a7b 100644
--- a/library/tests/dtest.cpp
+++ b/library/tests/dtest.cpp
@@ -52,7 +52,9 @@ EM_JS(void, dtest_schedule_pthread_clean_exit, (int code), {
 // Join C++ workers, let pending Worker "loaded" messages flush, then tear down
 // Emscripten pthread Workers and exit Node. Avoids ASSERTIONS noise of the form
 // `received "loaded" command from terminated worker` when -n exceeds the
-// precreated PTHREAD_POOL_SIZE.
+// precreated PTHREAD_POOL_SIZE. Emscripten 6 no longer exposes
+// PThread.runningWorkers or a per-worker `loaded` flag, so there the wait is a
+// bounded retry (up to 100 event-loop turns) rather than a readiness check.
 [[noreturn]] static void dtest_emscripten_clean_exit(const int code)
 {
     dds::internal::shutdown_parallel_boards_pool();
diff --git a/specs/wasm-emscripten.md b/specs/wasm-emscripten.md
index 74ecb8ea..667246a8 100644
--- a/specs/wasm-emscripten.md
+++ b/specs/wasm-emscripten.md
@@ -34,7 +34,7 @@ core solver builds and runs correctly under Emscripten.
 - **The toolchain is hermetic and transition-driven.** `wasm_cc_binary` applies an
   Emscripten **platform transition** to the underlying `cc_binary` — no
   `--config=wasm` or `.bazelrc` profile is needed. The emsdk toolchain is
-  downloaded/cached by Bazel (pinned in `MODULE.bazel`, currently `emsdk 5.0.7`).
+  downloaded/cached by Bazel (pinned in `MODULE.bazel`, currently `emsdk 6.0.12`).
   The transition is what makes the `//:build_wasm` config setting
   (`@platforms//cpu:wasm32`) active — see [build-system](build-system.md).
 - **WASM builds use pthreads.** Every `wasm_cc_binary` sets
@@ -75,7 +75,7 @@ core solver builds and runs correctly under Emscripten.
   `dtest_wasm` is an additional harness port, not an example CLI.
 - **No link-time LTO.** `-flto` applies at WASM compile time only
   ([build-system](build-system.md)); enabling it at link time was tried and
-  reverted because the `emsdk 5.0.7` toolchain pinned in `MODULE.bazel` ships a
+  reverted because the `emsdk` toolchain pinned in `MODULE.bazel` (checked again at 6.0.12) ships a
   frozen, pre-built cache containing only non-LTO system libraries. Link-time
   LTO requires LTO-bitcode variants of core sysroot libraries (e.g.
   `libprintf_long_double`) that the frozen cache cannot build on demand inside
diff --git a/web/BUILD.bazel b/web/BUILD.bazel
index d5cdbb01..e1cadc87 100644
--- a/web/BUILD.bazel
+++ b/web/BUILD.bazel
@@ -12,6 +12,10 @@ WASM_WEB_LINKOPTS = WASM_LINKOPTS + [
     "-sEXPORTED_FUNCTIONS=['_dds_web_calc_table','_dds_web_solve_leads','_dds_web_solve_plays','_malloc','_free']",
     "-sEXPORTED_RUNTIME_METHODS=['ccall','getValue']",
     "-sENVIRONMENT=web,worker,node",
+    # The Module properties createDdsModule() is called with (dds_web_solve.js,
+    # tests/dds_web_wasm_node.mjs). Emscripten >= 6.0.2 dropped wasmBinary from
+    # the default list: debug builds abort and release builds ignore the bytes.
+    "-sINCOMING_MODULE_JS_API=['wasmBinary']",
 ]
 
 cc_binary(
diff --git a/web/patch_web_wasm.py b/web/patch_web_wasm.py
index 4ba20e4e..6ffb70c9 100755
--- a/web/patch_web_wasm.py
+++ b/web/patch_web_wasm.py
@@ -17,9 +17,9 @@
 from pathlib import Path
 
 # Keep in sync with bazel_dep(name = "emsdk", version = "...") in MODULE.bazel.
-EXPECTED_EMSDK_BAZEL_DEP_VERSION = "5.0.7"
+EXPECTED_EMSDK_BAZEL_DEP_VERSION = "6.0.12"
 
-# Emscripten 5.x (emsdk 5.0.7): var isFileURI = filename => filename.startsWith("file://");
+# Emscripten 5.x and 6.x (emsdk 6.0.12): var isFileURI = filename => filename.startsWith("file://");
 # Older emsdk also emitted parentheses around the parameter.
 UNPATCHED_IS_FILE_URI = re.compile(
     r"var\s+isFileURI\s*=\s*(?:\(\s*)?(\w+)(?:\s*\))?\s*=>\s*"