diff --git a/DESCRIPTION b/DESCRIPTION
index e03c9e0..b654a58 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,8 +1,8 @@
 Package: chat.api
 Type: Package
 Title: Transport-Agnostic Chat Contract for R Agents
-Version: 0.0.1.25
-Date: 2026-09-04
+Version: 0.0.1.26
+Date: 2026-09-07
 Authors@R: c(
     person("Troy", "Hernandez", role = c("aut", "cre"),
            email = "troy@cornball.ai",
diff --git a/NAMESPACE b/NAMESPACE
index b38b00e..8c5f1d1 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -49,6 +49,7 @@ S3method(chat_capabilities,chat_matrix)
 S3method(chat_capabilities,chat_slack)
 S3method(chat_channel_create,chat_loopback)
 S3method(chat_channel_create,chat_matrix)
+S3method(chat_channel_create,chat_slack)
 S3method(chat_channel_create,default)
 S3method(chat_channel_info,chat_matrix)
 S3method(chat_channel_info,chat_slack)
@@ -77,6 +78,7 @@ S3method(chat_join,chat_matrix)
 S3method(chat_join,chat_slack)
 S3method(chat_join,default)
 S3method(chat_leave,chat_matrix)
+S3method(chat_leave,chat_slack)
 S3method(chat_leave,default)
 S3method(chat_mark_read,chat_matrix)
 S3method(chat_mark_read,chat_slack)
diff --git a/NEWS.md b/NEWS.md
index 925f1fa..4a6a6aa 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,11 @@
+# chat.api 0.0.1.26
+
+* Slack gains chat_channel_create() and chat_leave(), posting
+  conversations.create and conversations.leave through the adapter's API
+  seam. Adapter options such as is_private = TRUE pass through to the
+  request body, and Slack's own refusals (name_taken, invalid_name,
+  not_in_channel) propagate as errors. Both capability flags are now TRUE.
+
 # chat.api 0.0.1.25
 
 * Matrix E2EE saves ratchet state before room-key request transport, retries
diff --git a/R/slack.R b/R/slack.R
index ad34be7..e92df50 100644
--- a/R/slack.R
+++ b/R/slack.R
@@ -317,6 +317,36 @@ chat_join.chat_slack <- function(client, channel, ...) {
     invisible(sub("^#", "", channel))
 }
 
+#' @export
+chat_channel_create.chat_slack <- function(client, name, ...) {
+    # conversations.create. The name is normalized the way every other
+    # channel argument here is; Slack's own naming rules (lowercase, no
+    # spaces or periods) are enforced by the API and its refusal
+    # propagates. Adapter options (is_private = TRUE) ride through ...
+    # into the request body. The created channel is NOT added to the
+    # poll set: channels= is fixed at construction, the same bargain
+    # chat_join() makes.
+    api <- client$api_fn %||% slackr::call_slack_api
+    body <- slack_body(api("/api/conversations.create", .method = "POST",
+                           token = client$token,
+                           body = list(name = sub("^#", "", name), ...)))
+    slack_stop_for_error(body, "conversations.create")
+    invisible(as.character(body$channel$name %||% body$channel$id))
+}
+
+#' @export
+chat_leave.chat_slack <- function(client, channel, ...) {
+    # conversations.leave. A refusal (not_in_channel) propagates: a
+    # leave that quietly failed keeps delivering a channel the caller
+    # believes it has left.
+    api <- client$api_fn %||% slackr::call_slack_api
+    body <- slack_body(api("/api/conversations.leave", .method = "POST",
+                           token = client$token,
+                           body = list(channel = sub("^#", "", channel))))
+    slack_stop_for_error(body, "conversations.leave")
+    invisible(sub("^#", "", channel))
+}
+
 #' @export
 chat_members.chat_slack <- function(client, channel, ...) {
     api <- client$api_fn %||% slackr::call_slack_api
@@ -387,9 +417,7 @@ chat_capabilities.chat_slack <- function(client, ...) {
          invites = FALSE, join = TRUE, whoami = TRUE,
          channels = TRUE, history = TRUE, pending = FALSE,
          mark_read = TRUE, set_identity = TRUE, relogin = FALSE,
-         # conversations.create and conversations.leave exist in the
-         # Web API; this adapter has no verbs for them yet.
-         channel_create = FALSE, leave = FALSE, set_state = FALSE,
+         channel_create = TRUE, leave = TRUE, set_state = FALSE,
          files = FALSE, attachments = FALSE, typing = FALSE, e2ee = FALSE,
          identity_override = TRUE, rich_markup = character(),
          markup_dialects = c("plain", "markdown"),
diff --git a/inst/tinytest/test_slack.R b/inst/tinytest/test_slack.R
index dee62d4..17c3347 100644
--- a/inst/tinytest/test_slack.R
+++ b/inst/tinytest/test_slack.R
@@ -406,6 +406,59 @@ local({
     expect_true(caps$join)
 })
 
+# ---- Creating ----
+# conversations.create; Slack's answer names the channel, and that name
+# is the return value, since names are what every other verb in this
+# adapter takes. Adapter options (is_private) ride into the body.
+
+local({
+    seen <- NULL
+    cl <- slack_api_client(function(path, ..., body = NULL, .method, token) {
+        seen <<- list(path = path, body = body, .method = .method)
+        list(ok = TRUE, channel = list(id = "C9", name = "warroom"))
+    })
+    expect_identical(chat_channel_create(cl, "#warroom", is_private = TRUE),
+                     "warroom")
+    expect_identical(seen$path, "/api/conversations.create")
+    expect_identical(seen$.method, "POST")
+    expect_identical(seen$body$name, "warroom")
+    expect_true(seen$body$is_private)
+})
+
+# A refusal is an error, not a phantom channel: the caller must not walk
+# away with a name it believes is a room.
+expect_error(chat_channel_create(slack_api_client(function(...) {
+    list(ok = FALSE, error = "name_taken")
+}), "warroom"), "Slack refused conversations.create: name_taken")
+
+# ---- Leaving ----
+
+local({
+    seen <- NULL
+    cl <- slack_api_client(function(path, ..., body = NULL, .method, token) {
+        seen <<- list(path = path, body = body, .method = .method)
+        list(ok = TRUE)
+    })
+    expect_identical(chat_leave(cl, "#lab"), "lab")
+    expect_identical(seen$path, "/api/conversations.leave")
+    expect_identical(seen$.method, "POST")
+    expect_identical(seen$body$channel, "lab")
+})
+
+# A refusal propagates: a leave that quietly failed keeps delivering a
+# channel the caller believes it has left.
+expect_error(chat_leave(slack_api_client(function(...) {
+    list(ok = FALSE, error = "not_in_channel")
+}), "lab"), "Slack refused conversations.leave: not_in_channel")
+
+local({
+    caps <- chat_capabilities(chat_slack(channels = "lab", token = "t",
+                                         .history = function(...) NULL,
+                                         .post = function(...) "1"))
+    expect_true(caps$channel_create)
+    expect_true(caps$leave)
+})
+
 # ---- Identity ----
 slack_msg <- function(body = "", mentions = NULL) {
     chat_message(id = "1.1", channel = "lab", sender = "U999",