tools: add github_pr_merge, wait for CI then land a PR

src/permissions/rules.lex

@@ -80,7 +80,7 @@ fn spec_permission() -> sp.Spec {
 }
 
 fn refactor_permission() -> sp.Spec {
-  allow_tools("refactor_tools", list.concat(["read", "write", "edit", "grep", "glob", "bash", "remember", "lex_check", "os_check", "lex_audit", "sigid_lookup", "effects_of", "lex_store_merge", "propagate_effect", "github_pr_create"], list.concat(vcs_read_names(), vcs_write_names())))
+  allow_tools("refactor_tools", list.concat(["read", "write", "edit", "grep", "glob", "bash", "remember", "lex_check", "os_check", "lex_audit", "sigid_lookup", "effects_of", "lex_store_merge", "propagate_effect", "github_pr_create", "github_pr_merge"], list.concat(vcs_read_names(), vcs_write_names())))
 }
 
 fn test_permission() -> sp.Spec {

src/tools/github_pr_merge.lex

@@ -0,0 +1,94 @@
+# lex-code — wait for a pull request's checks, then merge it
+#
+# github_pr_create (lex-code#152) got a change as far as "a PR exists".
+# Landing it always meant a human (or Claude, driving `gh` by hand outside
+# this codebase) polling `gh pr checks`, then running `gh pr merge` once
+# green -- exactly the pattern GitHub Copilot's "Agent Merge" and Codex's
+# automatic pre-merge approval reviews both shipped in 2026, and exactly
+# what a real dogfooding session ended up doing by hand for six PRs in a
+# row before this tool existed.
+#
+# Approval-gated for the same reason github_pr_create is: merging is
+# visible to everyone with repo access and cannot be un-merged the way a
+# local edit can be un-written. The approval prompt covers the whole
+# conditional intent ("merge this once checks pass"), asked BEFORE the
+# outcome is known -- the same shape as a human reviewer saying "LGTM,
+# merge when CI is green" without re-approving after the fact.
+#
+# Deliberately verifies checks itself rather than trusting the caller's
+# own judgment that they're green: `gh pr checks --watch --fail-fast`
+# blocks until resolution and this tool refuses to call `gh pr merge` at
+# all unless that reports success, regardless of whether the repo's own
+# branch protection would have caught a bad merge anyway. A CI failure's
+# output is returned as the error detail (not swallowed) so the failure
+# can actually be diagnosed and fixed, not just reported as "didn't
+# merge".
+#
+# `pr` accepts anything `gh` itself accepts for a PR -- a number, a URL,
+# or a branch name (github_pr_create's own stdout is the PR's URL) --
+# rather than forcing this tool to parse one shape out of another.
+
+import "std.process" as proc
+
+import "std.list" as list
+
+import "lex-llm/tool" as t
+
+import "lex-schema/json_value" as jv
+
+import "lex-schema/error" as e
+
+import "lex-schema/schema" as s
+
+import "./util" as util
+
+fn params() -> s.ModelSchema {
+  { title: "GithubPrMergeArgs", description: "Wait for a pull request's checks to finish, then merge it if (and only if) they pass. Requires operator approval before it runs.", fields: [s.required_str("pr", []), s.optional(s.required_str("merge_method", []))] }
+}
+
+fn merge_flag(method :: Str) -> Str
+  examples {
+    merge_flag("squash") => "--squash",
+    merge_flag("rebase") => "--rebase",
+    merge_flag("merge") => "--merge",
+    merge_flag("") => "--squash",
+    merge_flag("bogus") => "--squash"
+  }
+{
+  if method == "rebase" {
+    "--rebase"
+  } else {
+    if method == "merge" {
+      "--merge"
+    } else {
+      "--squash"
+    }
+  }
+}
+
+fn execute(args :: jv.Json) -> [net, io, proc] Result[jv.Json, e.Errors] {
+  match util.field_str(args, "pr") {
+    None => Err(e.single("", "missing_field", "pr is required (a PR number, URL, or branch name)")),
+    Some(pr) => match proc.run("gh", ["pr", "checks", pr, "--watch", "--fail-fast"]) {
+      Err(msg) => Err(e.single("", "proc_error", msg)),
+      Ok(checks_out) => match util.cli_result(checks_out) {
+        Err(detail) => Err(e.single("", "checks_failed", detail)),
+        Ok(_) => {
+          let method := merge_flag(util.field_str_or(args, "merge_method", "squash"))
+          match proc.run("gh", ["pr", "merge", pr, method, "--delete-branch"]) {
+            Err(msg) => Err(e.single("", "proc_error", msg)),
+            Ok(merge_out) => match util.cli_result(merge_out) {
+              Err(detail) => Err(e.single("", "gh_pr_merge_failed", detail)),
+              Ok(body_out) => Ok(JStr(body_out)),
+            },
+          }
+        },
+      },
+    },
+  }
+}
+
+fn tool() -> t.Tool {
+  t.with_approval(t.define("github_pr_merge", "Wait for a pull request's CI checks to finish (gh pr checks --watch), then merge it only if they pass, deleting the branch afterward. Requires operator approval before it runs.", params(), execute), "github_pr_merge")
+}
+

src/tools/index.lex

@@ -48,6 +48,8 @@ import "./remember" as remember_tool
 
 import "./github_pr_create" as github_pr_tool
 
+import "./github_pr_merge" as github_pr_merge_tool
+
 import "./lex_store_merge" as store_merge_tool
 
 import "./vcs/ast_diff" as vcs_ast_diff_tool
@@ -124,7 +126,7 @@ fn vcs_tools() -> List[t.Tool] {
 # calling it — it compares a file's effects against that mode's grant —
 # so the toolset has to be built per mode rather than shared.
 fn all_tools_for_mode(mode :: Str) -> List[t.Tool] {
-  list.concat([read_tool.tool(), write_tool.tool(), edit_tool.tool(), grep_tool.tool(), glob_tool.tool(), bash_tool.tool(), todo_tool.tool(), remember_tool.tool(), check_tool.tool(), os_check_tool.tool_for_mode(mode), audit_tool.tool(), semantic_search_tool.tool(), run_tool.tool(), test_tool.tool(), spec_check_tool.tool(), spec_smt_tool.tool(), sigid_tool.tool(), attest_tool.tool(), effects_tool.tool(), store_merge_tool.tool(), propagate_tool.tool(), guidelines_tool.tool(), bar_check_tool.tool(), github_pr_tool.tool()], vcs_tools())
+  list.concat([read_tool.tool(), write_tool.tool(), edit_tool.tool(), grep_tool.tool(), glob_tool.tool(), bash_tool.tool(), todo_tool.tool(), remember_tool.tool(), check_tool.tool(), os_check_tool.tool_for_mode(mode), audit_tool.tool(), semantic_search_tool.tool(), run_tool.tool(), test_tool.tool(), spec_check_tool.tool(), spec_smt_tool.tool(), sigid_tool.tool(), attest_tool.tool(), effects_tool.tool(), store_merge_tool.tool(), propagate_tool.tool(), guidelines_tool.tool(), bar_check_tool.tool(), github_pr_tool.tool(), github_pr_merge_tool.tool()], vcs_tools())
 }
 
 # The build agent's own toolset: build's grant forbids nothing, so this

src/tools/smoke.lex

@@ -143,10 +143,10 @@ fn render(o :: Outcome) -> Str {
 # one anybody kept.
 fn skipped() -> List[Str]
   examples {
-    skipped() => ["read", "write", "edit", "grep", "glob", "bash", "todowrite", "remember", "semantic_search", "load_toolset", "vcs_branch_create", "vcs_branch_use", "vcs_merge_start", "vcs_merge_resolve", "vcs_merge_resolve_one", "vcs_merge_defer", "vcs_merge_commit", "vcs_op_push", "vcs_op_pull", "github_pr_create"]
+    skipped() => ["read", "write", "edit", "grep", "glob", "bash", "todowrite", "remember", "semantic_search", "load_toolset", "vcs_branch_create", "vcs_branch_use", "vcs_merge_start", "vcs_merge_resolve", "vcs_merge_resolve_one", "vcs_merge_defer", "vcs_merge_commit", "vcs_op_push", "vcs_op_pull", "github_pr_create", "github_pr_merge"]
   }
 {
-  ["read", "write", "edit", "grep", "glob", "bash", "todowrite", "remember", "semantic_search", "load_toolset", "vcs_branch_create", "vcs_branch_use", "vcs_merge_start", "vcs_merge_resolve", "vcs_merge_resolve_one", "vcs_merge_defer", "vcs_merge_commit", "vcs_op_push", "vcs_op_pull", "github_pr_create"]
+  ["read", "write", "edit", "grep", "glob", "bash", "todowrite", "remember", "semantic_search", "load_toolset", "vcs_branch_create", "vcs_branch_use", "vcs_merge_start", "vcs_merge_resolve", "vcs_merge_resolve_one", "vcs_merge_defer", "vcs_merge_commit", "vcs_op_push", "vcs_op_pull", "github_pr_create", "github_pr_merge"]
 }
 
 fn is_skipped(name :: Str) -> Bool