diff --git a/docs/PRE-RELEASE-TASKS.md b/docs/PRE-RELEASE-TASKS.md
index 17ccad7..9aff97e 100644
--- a/docs/PRE-RELEASE-TASKS.md
+++ b/docs/PRE-RELEASE-TASKS.md
@@ -82,7 +82,7 @@ These land together because both edit `domain/job.go` and `storage/store.go`.
 ### Phase 1 — Storage JSON + exit-code removal
 - [x] P1.1 — JSON struct tags
 - [x] P1.2 — `writeJSON` + JSON unmarshal
-- [ ] P1.3 — `gosentry.json` / `jobs.json` paths; drop pysentry name
+- [x] P1.3 — `gosentry.json` / `jobs.json` paths; drop pysentry name
 - [ ] P1.4 — One-time YAML import
 - [ ] P1.5 — Remove `SuccessExitCodes` across code
 - [ ] P1.6 — Update storage/runner/format tests + TESTS.md
diff --git a/src/storage/paths.go b/src/storage/paths.go
index 5c482e3..f3049fa 100644
--- a/src/storage/paths.go
+++ b/src/storage/paths.go
@@ -8,15 +8,16 @@ import (
 const (
 	// The config file stays beside the executable so the portable build behaves
 	// predictably: moving the program folder moves its settings with it.
-	ConfigFileName = "gosentry.yaml"
-	// Older builds were named PySentry. Keep the old config name readable during
-	// the rename window so portable installations can start once and rewrite the
-	// settings to gosentry.yaml without manual file copying.
-	LegacyConfigFileName = "pysentry.yaml"
-	// Jobs are kept in a separate YAML file because the user can choose a
+	ConfigFileName = "gosentry.json"
+	// Jobs are kept in a separate JSON file because the user can choose a
 	// different jobs directory, while application settings remain local to the
 	// installed/copied program.
-	JobsFileName = "jobs.yaml"
+	JobsFileName = "jobs.json"
+
+	// Legacy YAML file names used by builds before the JSON migration. These are
+	// read once on first start (P1.4) and then replaced by the JSON equivalents.
+	legacyYAMLConfigFileName = "gosentry.yaml"
+	legacyYAMLJobsFileName   = "jobs.yaml"
 )
 
 // Paths contains both the physical program location and the resolved runtime
diff --git a/src/storage/store.go b/src/storage/store.go
index f8cb64f..08552b4 100644
--- a/src/storage/store.go
+++ b/src/storage/store.go
@@ -41,9 +41,9 @@ func OpenStore() (*Store, []domain.Job, error) {
 		return nil, nil, err
 	}
 	normalizeJobs(jobs)
-	// Jobs are also rewritten after normalization. That keeps jobs.yaml compact:
+	// Jobs are also rewritten after normalization. That keeps jobs.json compact:
 	// only durable job definitions remain, because runtime fields are tagged
-	// yaml:"-" in the model.
+	// json:"-" in the model.
 	if err := store.SaveJobs(jobs); err != nil {
 		return nil, nil, err
 	}
@@ -80,13 +80,11 @@ func loadOrCreateConfig(paths Paths) (domain.Config, error) {
 
 	configPath := paths.ConfigPath
 	if _, err := os.Stat(configPath); errors.Is(err, os.ErrNotExist) {
-		legacyPath := filepath.Join(paths.AppDir, LegacyConfigFileName)
+		legacyPath := filepath.Join(paths.AppDir, legacyYAMLConfigFileName)
 		if _, legacyErr := os.Stat(legacyPath); legacyErr == nil {
-			// The rename from PySentry to GoSentry changed the preferred config
-			// filename. Read the old file once if it is still present so portable
-			// installs continue to start without a manual migration step. The
-			// caller later saves the loaded config back through SaveConfig, which
-			// naturally rewrites it under gosentry.yaml.
+			// gosentry.yaml is the pre-JSON-migration config file. Read it once
+			// when gosentry.json is absent so existing installs migrate without
+			// manual intervention. SaveConfig rewrites the result as gosentry.json.
 			configPath = legacyPath
 		} else {
 			return config, writeJSON(paths.ConfigPath, config)
diff --git a/src/storage/store_test.go b/src/storage/store_test.go
index 9d14f03..02c2fd1 100644
--- a/src/storage/store_test.go
+++ b/src/storage/store_test.go
@@ -155,15 +155,14 @@ func TestNormalizeJobsFillsDefaults(t *testing.T) {
 	}
 }
 
-// TestLoadOrCreateConfigMigratesFromLegacy verifies that when gosentry.yaml is
-// absent but pysentry.yaml exists the config is read from the legacy file. This
-// lets portable installs that still carry a pysentry.yaml start without manual
-// migration.
+// TestLoadOrCreateConfigMigratesFromLegacy verifies that when gosentry.json is
+// absent but gosentry.yaml exists the config is read from the legacy YAML file.
+// This lets installs that pre-date the JSON migration start without manual steps.
 func TestLoadOrCreateConfigMigratesFromLegacy(t *testing.T) {
 	dir := t.TempDir()
 	paths := Paths{
 		AppDir:     dir,
-		ConfigPath: filepath.Join(dir, ConfigFileName), // gosentry.yaml — not created
+		ConfigPath: filepath.Join(dir, ConfigFileName), // gosentry.json — not created
 	}
 
 	legacy := domain.Config{
@@ -173,7 +172,7 @@ func TestLoadOrCreateConfigMigratesFromLegacy(t *testing.T) {
 		MaxLogAgeDays: 13,
 		StartOnLogin:  true,
 	}
-	if err := writeYAML(filepath.Join(dir, LegacyConfigFileName), legacy); err != nil {
+	if err := writeYAML(filepath.Join(dir, legacyYAMLConfigFileName), legacy); err != nil {
 		t.Fatal(err)
 	}
 
@@ -199,7 +198,7 @@ func TestLoadOrCreateConfigMigratesFromLegacy(t *testing.T) {
 }
 
 // TestLoadOrCreateConfigCreatesDefaultsOnFirstRun verifies that the first run
-// (no config files present) writes gosentry.yaml and returns sensible defaults.
+// (no config files present) writes gosentry.json and returns sensible defaults.
 func TestLoadOrCreateConfigCreatesDefaultsOnFirstRun(t *testing.T) {
 	dir := t.TempDir()
 	paths := Paths{
@@ -223,9 +222,9 @@ func TestLoadOrCreateConfigCreatesDefaultsOnFirstRun(t *testing.T) {
 	if got.MaxLogAgeDays != 30 {
 		t.Errorf("default MaxLogAgeDays = %d, want 30", got.MaxLogAgeDays)
 	}
-	// The function must have written the defaults to gosentry.yaml.
+	// The function must have written the defaults to gosentry.json.
 	if _, err := os.Stat(paths.ConfigPath); err != nil {
-		t.Errorf("gosentry.yaml should have been created: %v", err)
+		t.Errorf("gosentry.json should have been created: %v", err)
 	}
 }