diff --git a/.replit b/.replit
index 86703645..9b5e227a 100644
--- a/.replit
+++ b/.replit
@@ -1,6 +1,5 @@
-run = "make && echo \"UPM is built, can be found here: ./cmd/upm/upm\""
-
-modules = ["go-1.20:v2-20230911-b5aa5df"]
+run = "make upm && echo \"UPM is built, can be found here: ./cmd/upm/upm\""
+modules = ["bash", "bun-1.1", "go-1.21", "python-3.12"]
 
 [nix]
-channel = "stable-23_05"
+channel = "stable-24_05"
diff --git a/internal/api/types.go b/internal/api/types.go
index 4e18ce3d..b3e19d64 100644
--- a/internal/api/types.go
+++ b/internal/api/types.go
@@ -182,6 +182,10 @@ type LanguageBackend struct {
 	// Check to see if we think we can run at all
 	IsAvailable func() bool
 
+	// Check for signs that this backend has either been used or
+	// can be used to query
+	IsActive func() bool
+
 	// List of filename globs that match against files written in
 	// this programming language, e.g. "*.py" for Python. These
 	// should not include any slashes, because they may be matched
diff --git a/internal/backends/nodejs/nodejs.go b/internal/backends/nodejs/nodejs.go
index 9ae4a0e5..06b9f856 100644
--- a/internal/backends/nodejs/nodejs.go
+++ b/internal/backends/nodejs/nodejs.go
@@ -391,12 +391,20 @@ var tsxPathGlobs = []string{
 	"*.tsx",
 }
 
+func commonIsActive(lockfile string) bool {
+	_, err := os.Stat(lockfile)
+	return !os.IsNotExist(err)
+}
+
 // NodejsYarnBackend is a UPM backend for Node.js that uses [Yarn](https://yarnpkg.com/).
 var NodejsYarnBackend = api.LanguageBackend{
 	Name:             "nodejs-yarn",
 	Specfile:         "package.json",
 	Lockfile:         "yarn.lock",
 	IsAvailable:      yarnIsAvailable,
+	IsActive: func() bool {
+		return commonIsActive("yarn.lock")
+	},
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
@@ -481,6 +489,9 @@ var NodejsPNPMBackend = api.LanguageBackend{
 	Specfile:         "package.json",
 	Lockfile:         "pnpm-lock.yaml",
 	IsAvailable:      pnpmIsAvailable,
+	IsActive: func() bool {
+		return commonIsActive("pnpm-lock.yaml")
+	},
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
@@ -581,6 +592,9 @@ var NodejsNPMBackend = api.LanguageBackend{
 	Specfile:         "package.json",
 	Lockfile:         "package-lock.json",
 	IsAvailable:      npmIsAvailable,
+	IsActive: func() bool {
+		return commonIsActive("package-lock.json")
+	},
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
@@ -670,6 +684,9 @@ var BunBackend = api.LanguageBackend{
 	Specfile:         "package.json",
 	Lockfile:         "bun.lockb",
 	IsAvailable:      bunIsAvailable,
+	IsActive: func() bool {
+		return commonIsActive("bun.lockb")
+	},
 	FilenamePatterns: nodejsPatterns,
 	Quirks: api.QuirksAddRemoveAlsoLocks |
 		api.QuirksAddRemoveAlsoInstalls |
diff --git a/internal/backends/python/python.go b/internal/backends/python/python.go
index 92be5938..278a2f91 100644
--- a/internal/backends/python/python.go
+++ b/internal/backends/python/python.go
@@ -301,6 +301,11 @@ func commonGuessPackageDir() string {
 	return ""
 }
 
+func commonIsActive(lockfile string) bool {
+	_, err := os.Stat(lockfile)
+	return !os.IsNotExist(err)
+}
+
 var pythonGuessRegexps = util.Regexps([]string{
 	// The (?:.|\\\n) subexpression allows us to
 	// match match multiple lines if
@@ -383,6 +388,9 @@ func makePythonPoetryBackend() api.LanguageBackend {
 			_, err := exec.LookPath("poetry")
 			return err == nil
 		},
+		IsActive: func() bool {
+			return commonIsActive("poetry.lock")
+		},
 		FilenamePatterns: []string{"*.py"},
 		Quirks: api.QuirksAddRemoveAlsoLocks |
 			api.QuirksAddRemoveAlsoInstalls,
@@ -754,6 +762,9 @@ func makePythonUvBackend() api.LanguageBackend {
 			_, err := exec.LookPath("uv")
 			return err == nil
 		},
+		IsActive: func() bool {
+			return commonIsActive("uv.lock")
+		},
 		Alias:                "python-python3-uv",
 		FilenamePatterns:     []string{"*.py"},
 		Quirks:               api.QuirksAddRemoveAlsoInstalls | api.QuirksAddRemoveAlsoLocks,
diff --git a/internal/cli/cli.go b/internal/cli/cli.go
index ac70b0d0..eeb19b22 100644
--- a/internal/cli/cli.go
+++ b/internal/cli/cli.go
@@ -96,9 +96,12 @@ func DoCLI() {
 		Long:  "Ask which language your project is autodetected as",
 		Args:  cobra.NoArgs,
 		Run: func(cmd *cobra.Command, args []string) {
-			runWhichLanguage(language)
+			runWhichLanguage(language, all)
 		},
 	}
+	cmdWhichLanguage.Flags().BoolVarP(
+		&all, "all", "a", false, "List all packages for all detected languages",
+	)
 	rootCmd.AddCommand(cmdWhichLanguage)
 
 	cmdListLanguages := &cobra.Command{
diff --git a/internal/cli/cmds.go b/internal/cli/cmds.go
index 53d7b8c4..22e3e578 100644
--- a/internal/cli/cmds.go
+++ b/internal/cli/cmds.go
@@ -42,9 +42,29 @@ func (s *subroutineSilencer) restore() {
 }
 
 // runWhichLanguage implements 'upm which-language'.
-func runWhichLanguage(language string) {
-	b := backends.GetBackend(context.Background(), language)
-	fmt.Println(b.Name)
+func runWhichLanguage(language string, all bool) {
+	if !all {
+		b := backends.GetBackend(context.Background(), language)
+		fmt.Println(b.Name)
+		return
+	}
+	for _, bi := range backends.GetBackendNames() {
+		if !bi.Available {
+			continue
+		}
+		if language != "" && !strings.Contains(bi.Name, language) {
+			continue
+		}
+
+		b := backends.GetBackend(context.Background(), bi.Name)
+
+		// If we can't determine we are in use, don't report
+		if b.IsActive == nil || !b.IsActive() {
+			continue
+		}
+
+		fmt.Println(b.Name)
+	}
 }
 
 // runListLanguages implements 'upm list-languages'.