feat(cli): add --since, --tail, --json flags to tilt logs

Implements #6652 - adds filtering and JSON output capabilities to tilt logs:

- --since: Filter logs by time (e.g., "5m", "1h", "30s")
- --tail: Limit output to last N lines (applies only to initial history
  when combined with -f/--follow)
- --json: Output logs as JSON Lines (JSONL) format
- --json-fields: Configure JSON output fields ("minimal", "full", or
  comma-separated field list)

Implementation details:
- Extends LogFilter with Since/Tail fields and time-based filtering
- Adds JSONPrinter for structured JSONL output with configurable fields
- Uses pointer types in JSONLogLine to distinguish "not included" from
  "empty value" for --json-fields=full
- LogStreamer tracks isFirstBatch to apply tail only to initial history
- Validates --since (positive duration), --tail (>= -1), and --json-fields
  (rejects unknown field names)

Closes #6652

Signed-off-by: Big Boss <bigboss@metalrodeo.xyz>

Author: 0xBigBoss

.gitignore

@@ -63,3 +63,9 @@ yarn-error.log*
 # http caches from running kubectl in integration tests
 integration/.kube
 .aider*
+
+# Claude Code state files
+.claude/
+
+# Built binary at repo root
+/tilt

internal/cli/flags.go

@@ -122,6 +122,13 @@ func addLogFilterFlags(cmd *cobra.Command, prefix string) {
 	)
 }
 
+func addLogOutputFlags(cmd *cobra.Command) {
+	cmd.Flags().StringVar(&logSinceFlag, "since", "", `Only show logs since duration ago (e.g., "5m", "1h", "30s")`)
+	cmd.Flags().IntVar(&logTailFlag, "tail", -1, `Number of lines to show from the end of logs (-1 for all)`)
+	cmd.Flags().BoolVar(&logJSONFlag, "json", false, `Output logs in JSON Lines format`)
+	cmd.Flags().StringVar(&logJSONFieldsFlag, "json-fields", "", `Fields to include in JSON output. Presets: "minimal" (default), "full". Or comma-separated: "time,resource,level,message"`)
+}
+
 var kubeContextOverride string
 
 func ProvideKubeContextOverride() k8s.KubeContextOverride {

internal/cli/logs.go

@@ -35,6 +35,7 @@ By default, looks for a running Tilt instance on localhost:10350
 
 	addConnectServerFlags(cmd)
 	addLogFilterFlags(cmd, "")
+	addLogOutputFlags(cmd)
 	return cmd
 }
 
@@ -56,5 +57,5 @@ func (c *logsCmd) run(ctx context.Context, args []string) error {
 		return err
 	}
 
-	return server.StreamLogs(ctx, c.follow, logDeps.url, logDeps.filter, logDeps.printer)
+	return server.StreamLogs(ctx, c.follow, logDeps.url, logDeps.filter, logDeps.stdout)
 }

internal/cli/logs_test.go

@@ -0,0 +1,113 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestProvideLogSinceValidation(t *testing.T) {
+	testCases := []struct {
+		name        string
+		flag        string
+		expectError bool
+		errorMsg    string
+	}{
+		{
+			name:        "empty is valid",
+			flag:        "",
+			expectError: false,
+		},
+		{
+			name:        "positive duration is valid",
+			flag:        "5m",
+			expectError: false,
+		},
+		{
+			name:        "negative duration is invalid",
+			flag:        "-5m",
+			expectError: true,
+			errorMsg:    "must be positive",
+		},
+		{
+			name:        "invalid format returns parse error",
+			flag:        "notaduration",
+			expectError: true,
+			errorMsg:    "invalid duration",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Save and restore the global flag
+			oldFlag := logSinceFlag
+			defer func() { logSinceFlag = oldFlag }()
+
+			logSinceFlag = tc.flag
+			_, err := provideLogSince()
+
+			if tc.expectError {
+				require.Error(t, err)
+				assert.Contains(t, err.Error(), tc.errorMsg)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestProvideLogTailValidation(t *testing.T) {
+	testCases := []struct {
+		name        string
+		flag        int
+		expectError bool
+		errorMsg    string
+	}{
+		{
+			name:        "-1 (no limit) is valid",
+			flag:        -1,
+			expectError: false,
+		},
+		{
+			name:        "0 is valid",
+			flag:        0,
+			expectError: false,
+		},
+		{
+			name:        "positive is valid",
+			flag:        100,
+			expectError: false,
+		},
+		{
+			name:        "-2 is invalid",
+			flag:        -2,
+			expectError: true,
+			errorMsg:    "must be -1 (no limit) or >= 0",
+		},
+		{
+			name:        "-100 is invalid",
+			flag:        -100,
+			expectError: true,
+			errorMsg:    "must be -1 (no limit) or >= 0",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Save and restore the global flag
+			oldFlag := logTailFlag
+			defer func() { logTailFlag = oldFlag }()
+
+			logTailFlag = tc.flag
+			_, err := provideLogTail()
+
+			if tc.expectError {
+				require.Error(t, err)
+				assert.Contains(t, err.Error(), tc.errorMsg)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}

internal/cli/up.go

@@ -31,12 +31,16 @@ var webModeFlag model.WebMode = model.DefaultWebMode
 const DefaultWebDevPort = 46764
 
 var (
-	updateModeFlag   string   = string(liveupdates.UpdateModeAuto)
-	webDevPort                = 0
-	logActionsFlag   bool     = false
-	logSourceFlag    string   = ""
-	logResourcesFlag []string = nil
-	logLevelFlag     string   = ""
+	updateModeFlag    string   = string(liveupdates.UpdateModeAuto)
+	webDevPort                 = 0
+	logActionsFlag    bool     = false
+	logSourceFlag     string   = ""
+	logResourcesFlag  []string = nil
+	logLevelFlag      string   = ""
+	logSinceFlag      string   = ""
+	logTailFlag       int      = -1 // -1 means no limit
+	logJSONFlag       bool     = false
+	logJSONFieldsFlag string   = ""
 )
 
 var userExitError = errors.New("user requested Tilt exit")

internal/cli/wire.go

@@ -7,6 +7,7 @@ package cli
 
 import (
 	"context"
+	"fmt"
 	"time"
 
 	"github.com/spf13/afero"
@@ -113,6 +114,10 @@ var BaseWireSet = wire.NewSet(
 	provideLogSource,
 	provideLogResources,
 	provideLogLevel,
+	provideLogSince,
+	provideLogTail,
+	provideLogJSON,
+	provideLogJSONFields,
 	hud.WireSet,
 	prompt.WireSet,
 	wire.Value(openurl.OpenURL(openurl.BrowserOpen)),
@@ -304,9 +309,9 @@ func wireLogsDeps(ctx context.Context, tiltAnalytics *analytics.TiltAnalytics, s
 }
 
 type LogsDeps struct {
-	url     model.WebURL
-	printer *hud.IncrementalPrinter
-	filter  hud.LogFilter
+	url    model.WebURL
+	stdout hud.Stdout
+	filter hud.LogFilter
 }
 
 func provideClock() func() time.Time {
@@ -366,3 +371,32 @@ func provideLogLevel() hud.FilterLevel {
 		return hud.FilterLevel(logger.NoneLvl)
 	}
 }
+
+func provideLogSince() (hud.FilterSince, error) {
+	if logSinceFlag == "" {
+		return hud.FilterSince(0), nil
+	}
+	d, err := time.ParseDuration(logSinceFlag)
+	if err != nil {
+		return 0, err
+	}
+	if d < 0 {
+		return 0, fmt.Errorf("--since duration must be positive, got %v", d)
+	}
+	return hud.FilterSince(d), nil
+}
+
+func provideLogTail() (hud.FilterTail, error) {
+	if logTailFlag < -1 {
+		return 0, fmt.Errorf("--tail must be -1 (no limit) or >= 0, got %d", logTailFlag)
+	}
+	return hud.FilterTail(logTailFlag), nil
+}
+
+func provideLogJSON() hud.FilterJSON {
+	return hud.FilterJSON(logJSONFlag)
+}
+
+func provideLogJSONFields() hud.FilterJSONFields {
+	return hud.FilterJSONFields(logJSONFieldsFlag)
+}