diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 075c20d..7ff0daa 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -493,7 +493,7 @@ jobs:
           export PKG_CONFIG_PATH="$PWD/inst/lib/pkgconfig"
           pkg-config --exists protothread
           echo "version: $(pkg-config --modversion protothread)"
-          test "$(pkg-config --modversion protothread)" = "2.0.0"
+          test "$(pkg-config --modversion protothread)" = "2.1.0"
           printf '#include "protothread.h"\nint main(void){struct protothread_s s;protothread_init(&s);return protothread_run(&s);}\n' > use.c
           gcc $(pkg-config --cflags protothread) use.c -o use $(pkg-config --libs protothread)
           ./use
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 98e7f86..3ffbfcf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [2.1.0] - 2026-10-15
+
 ### Added
 
 - `pt_wait_until(c, channel, cond)`, which tests the predicate and enqueues in
@@ -22,7 +24,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   before `pt_kill()`ing or freeing one that might be using the lock, as
   `pt_timer_cancel()` is for one that might be sleeping. Without it such a kill
   left the lock granted to a dead thread and never released.
-
 - `protothread_queue.h`: message queues, what Go calls channels. A queue is a
   fixed-capacity ring buffer in storage the caller supplies, so it needs no
   allocator, and `PT_QUEUE_DEFINE(name, type)` makes it type-safe; `pt_queue_t`
@@ -47,6 +48,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   the lock can tell a live request from a finished one. Internal, but it means
   a `pt_lock_env_t` must be zeroed or have been used with that lock before
   `pt_lock_cancel()` is called on it.
+- The README's sections on semaphores, timers, locks, and queues moved to
+  their own pages under `doc/`, and the rest of the README was edited for
+  readability.
 
 ## [2.0.0] - 2026-09-22
 
@@ -170,4 +174,6 @@ There were no tagged releases before 2.0.0. The earlier code, which CMake and
 pkg-config reported as version 1.0 regardless of what changed, is referred to
 here as 1.x.
 
+[Unreleased]: https://github.com/LarryRuane/protothread/compare/v2.1.0...HEAD
+[2.1.0]: https://github.com/LarryRuane/protothread/releases/tag/v2.1.0
 [2.0.0]: https://github.com/LarryRuane/protothread/releases/tag/v2.0.0
diff --git a/README.md b/README.md
index c596b2d..6c67da7 100644
--- a/README.md
+++ b/README.md
@@ -697,10 +697,10 @@ This project uses [semantic versioning](https://semver.org). The version lives i
 
 ```c
 #define PT_VERSION_MAJOR 2
-#define PT_VERSION_MINOR 0
+#define PT_VERSION_MINOR 1
 #define PT_VERSION_PATCH 0
-#define PT_VERSION_NUMBER   /* ordered: 20000 */
-#define PT_VERSION_STRING   /* "2.0.0", derived from the numbers */
+#define PT_VERSION_NUMBER   /* ordered: 20100 */
+#define PT_VERSION_STRING   /* "2.1.0", derived from the numbers */
 #define PT_VERSION_AT_LEAST(major, minor, patch)
 ```
 
diff --git a/TODO.md b/TODO.md
index ebd3e2f..3d80ac0 100644
--- a/TODO.md
+++ b/TODO.md
@@ -68,11 +68,9 @@ argument actually bites.
 
 ## More synchronization primitives ##
 
-Timers are done (`protothread_timer.h`). Remaining, most useful first:
+Timers (`protothread_timer.h`) and message queues (`protothread_queue.h`, in
+2.1.0) are done. Remaining, most useful first:
 
-  * **Message queue.** The most-used RTOS primitive in practice, and it would
-    replace the hand-rolled single-slot mailbox in the README's own example.
-    Bounded ring over a caller-supplied buffer, blocking put/get, no allocation.
   * **Event flags.** Wait for any or all of a bit mask. Pairs well with
     interrupt handlers, and is the cheap workaround for the lack of multi-wait.
   * **Wait with timeout.** Needs the pattern the reader-writer lock already
@@ -147,7 +145,7 @@ debugging into a one-line call, and costs nothing in a production build.
 
   * ~~Continuous integration~~ -- done, `.github/workflows/ci.yml`. Its first
     run found that the library did not build under clang at all.
-  * ~~Tag a release~~ -- done, `v2.0.0`.
+  * ~~Tag a release~~ -- done, `v2.0.0`, then `v2.1.0`.
   * ~~Document that `pt_wait`/`pt_signal` *is* a condition variable~~ -- done,
     the "Wait channels" section of README.md, which also makes the case for the
     interface: it is universal, and it degenerates to a busy-wait loop you can
diff --git a/protothread.h b/protothread.h
index aff43c1..aa0c53e 100644
--- a/protothread.h
+++ b/protothread.h
@@ -68,7 +68,7 @@
  *   #endif
  */
 #define PT_VERSION_MAJOR 2
-#define PT_VERSION_MINOR 0
+#define PT_VERSION_MINOR 1
 #define PT_VERSION_PATCH 0
 
 #define PT_VERSION_NUMBER \