diff --git a/cmd/cueckoo/cmd/cltrigger.go b/cmd/cueckoo/cmd/cltrigger.go
index 2e62a29..9f837ac 100644
--- a/cmd/cueckoo/cmd/cltrigger.go
+++ b/cmd/cueckoo/cmd/cltrigger.go
@@ -45,36 +45,58 @@ func newCLTrigger(cmd *Command, cfg *config, b builder) *cltrigger {
 	}
 }
 
+// Per https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#change-id,
+// a change ID can be in multiple forms.
+// We only really care about CL numbers and Change-ID identifiers from git commit trailers,
+// since those are what a human user is most likely going to find useful.
+// The long forms, like "project~branch~I1234..." are far too cumbersome.
+var rxChangeID = regexp.MustCompile(`^[1-9][0-9]{3,}|I[0-9a-f]{40}$`)
+
 func (c *cltrigger) run() (err error) {
 	var changeIDs []revision
-	args := make(map[string]bool)
-	for _, a := range c.cmd.Flags().Args() {
-		args[a] = true
+	args := c.cmd.Flags().Args()
+	derive := true
+	for _, arg := range args {
+		if rxChangeID.MatchString(arg) {
+			derive = false
+		} else if !derive {
+			return fmt.Errorf("cannot mix change IDs and git refs")
+		}
 	}
-	if flagChange.Bool(c.cmd) {
+	if derive {
+		changeIDs, err = c.deriveChangeIDs(args)
+		if err != nil {
+			return err
+		}
+	} else {
 		if len(args) == 0 {
 			return fmt.Errorf("must provide at least one change number of ID")
 		}
-		for a := range args {
+		for _, a := range args {
 			changeIDs = append(changeIDs, revision{
 				changeID: a,
 			})
 		}
-	} else {
-		changeIDs, err = c.deriveChangeIDs(args)
-		if err != nil {
-			return err
-		}
 	}
 	return c.triggerBuilds(changeIDs)
 }
 
+// TODO: replace once we can use slices.Contains
+func slicesContains[S ~[]E, E comparable](s S, v E) bool {
+	for i := range s {
+		if v == s[i] {
+			return true
+		}
+	}
+	return false
+}
+
 // deriveChangeIDs determines a list of change IDs for the supplied args (if
 // there are any). See the trybot docs for an explanation of what is derived.
 // Essentially however we try to follow the semantics of git-codereview:
 //
 // https://pkg.go.dev/golang.org/x/review/git-codereview
-func (c *cltrigger) deriveChangeIDs(args map[string]bool) (res []revision, err error) {
+func (c *cltrigger) deriveChangeIDs(args []string) (res []revision, err error) {
 	ctx := context.TODO()
 	// Work out the branchpoint
 	bp, err := run(ctx, "git", "codereview", "branchpoint")
@@ -91,10 +113,11 @@ func (c *cltrigger) deriveChangeIDs(args map[string]bool) (res []revision, err e
 	if len(pendingCommits) == 0 {
 		return nil, fmt.Errorf("no pending commits")
 	}
-	if args["HEAD"] && len(args) > 1 {
+	argHead := slicesContains(args, "HEAD")
+	if argHead && len(args) > 1 {
 		return nil, fmt.Errorf("HEAD can only be supplied as an argument by itself")
 	}
-	if !args["HEAD"] && len(pendingCommits) > 1 && len(args) == 0 {
+	if !argHead && len(pendingCommits) > 1 && len(args) == 0 {
 		return nil, fmt.Errorf("must specify commits as arguments or use HEAD for everything")
 	}
 	addRevision := func(pc commit) error {
@@ -124,7 +147,7 @@ func (c *cltrigger) deriveChangeIDs(args map[string]bool) (res []revision, err e
 		})
 		return nil
 	}
-	if args["HEAD"] || len(args) == 0 && len(pendingCommits) == 1 {
+	if argHead || len(args) == 0 && len(pendingCommits) == 1 {
 		// Verify all
 		for _, pc := range pendingCommits {
 			if err := addRevision(pc); err != nil {
@@ -137,7 +160,7 @@ func (c *cltrigger) deriveChangeIDs(args map[string]bool) (res []revision, err e
 
 		// We verify each of the arguments
 	EachArg:
-		for h := range args {
+		for _, h := range args {
 			// Resolve the arg and ensure we have a matching pending commit
 			// and ensure we have a single one
 			commits, err := resolveCommits(ctx, "-1", h)
@@ -177,6 +200,9 @@ func resolveCommits(ctx context.Context, args ...string) ([]commit, error) {
 	if err != nil {
 		return nil, err
 	}
+	if commitStream == "" {
+		return nil, fmt.Errorf("%q resulted in no git commits", args)
+	}
 
 	var commits []commit
 
diff --git a/cmd/cueckoo/cmd/runtrybot.go b/cmd/cueckoo/cmd/runtrybot.go
index 764d26a..0edee7a 100644
--- a/cmd/cueckoo/cmd/runtrybot.go
+++ b/cmd/cueckoo/cmd/runtrybot.go
@@ -22,7 +22,6 @@ import (
 )
 
 const (
-	flagChange           flagName = "change"
 	flagRunTrybotNoUnity flagName = "nounity"
 	flagForce            flagName = "force"
 )
@@ -35,23 +34,18 @@ func newRuntrybotCmd(c *Command) *cobra.Command {
 		Long: `
 Usage of runtrybot:
 
-	runtrybot [--change] [--nounity] [ARGS...]
+	runtrybot [--nounity] [ARGS...]
 
 Triggers trybot and unity runs for its arguments.
 
 When run with no arguments, runtrybot derives a revision and change ID for each
 pending commit in the current branch. If multiple pending commits are found,
-you must either specify which commits to run, or specify HEAD to run the
+you must either specify which commits or CLs to run, or specify HEAD to run the
 trybots for all of them.
 
-If the --change flag is provide, then the list of arguments is interpreted as
-change numbers or IDs, and the latest revision from each of those changes is
-assumed.
-
-runtrybot requires GITHUB_USER and GITHUB_PAT environment variables to be set
-with your GitHub username and personal acccess token respectively. The personal
-access token requires the "repo" scope, since Unity is a private repository.
-
+runtrybot needs your GitHub username and a personal acccess token
+with the "repo" scope. You can configure them via your git credential helper,
+or by setting the GITHUB_USER and GITHUB_PAT environment variables.
 Note that the personal access token should be "classic"; GitHub's new
 fine-grained tokens are still in beta and haven't been tested to work here.
 
@@ -59,7 +53,6 @@ If the --nounity flag is provided, only a trybot run is triggered.
 `,
 		RunE: mkRunE(c, runtrybotDef),
 	}
-	cmd.Flags().Bool(string(flagChange), false, "interpret arguments as change numbers or IDs")
 	cmd.Flags().Bool(string(flagRunTrybotNoUnity), false, "do not simultaenously trigger unity build")
 	cmd.Flags().BoolP(string(flagForce), string(flagForce[0]), false, "force the trybots to run, ignoring any results")
 	return cmd
diff --git a/cmd/cueckoo/cmd/unity.go b/cmd/cueckoo/cmd/unity.go
index d5e03f7..c9f709b 100644
--- a/cmd/cueckoo/cmd/unity.go
+++ b/cmd/cueckoo/cmd/unity.go
@@ -45,13 +45,14 @@ unity for all of them.
 If the --normal flag is provided, then the list of arguments is interpreted as
 versions understood by unity.
 
-unity requires GITHUB_USER and GITHUB_PAT environment variables to be set with
-your GitHub username and personal acccess token respectively. The personal
-access token requires the "repo" scope, since Unity is a private repository.
+runtrybot needs your GitHub username and a personal acccess token
+with the "repo" scope. You can configure them via your git credential helper,
+or by setting the GITHUB_USER and GITHUB_PAT environment variables.
+Note that the personal access token should be "classic"; GitHub's new
+fine-grained tokens are still in beta and haven't been tested to work here.
 `,
 		RunE: mkRunE(c, unityDef),
 	}
-	cmd.Flags().Bool(string(flagChange), false, "interpret arguments as change numbers or IDs")
 	cmd.Flags().Bool(string(flagUnityVersions), false, "pass arguments to unity as versions")
 	return cmd
 }
@@ -62,10 +63,6 @@ func unityDef(cmd *Command, args []string) error {
 		return err
 	}
 
-	if flagUnityVersions.Bool(cmd) && flagChange.Bool(cmd) {
-		return fmt.Errorf("cannot supply --change and --versions")
-	}
-
 	// If we are passed --normal, interpret all args as versions to be passed to
 	// unity
 	if flagUnityVersions.Bool(cmd) {