Address CodeRabbit review: validate negative max_connections on all paths

- Let negative values pass through resolvers and config fallbacks
  instead of silently treating them as unset, so Validate() rejects
  them consistently.
- Add max_connections validation to RepsetDiffCmd.Validate() and
  SchemaDiffCmd.Validate() to fail fast before per-table fan-out.
- Simplify jobs config assignments to unconditional intArg calls.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mason-sharp

internal/api/http/handler.go

@@ -299,6 +299,9 @@ func (s *APIServer) resolveMaxConnections(cfg *config.Config, requested int) int
 	if requested > 0 {
 		return requested
 	}
+	if requested < 0 {
+		return requested // rejected by Validate()
+	}
 	if cfg != nil && cfg.TableDiff.MaxConnections > 0 {
 		return cfg.TableDiff.MaxConnections
 	}

internal/consistency/diff/repset_diff.go

@@ -231,6 +231,9 @@ func (c *RepsetDiffCmd) Validate() error {
 	if c.RepsetName == "" {
 		return fmt.Errorf("repset name is required")
 	}
+	if c.MaxConnections < 0 {
+		return fmt.Errorf("max_connections must be >= 1 (or 0 to derive from concurrency factor)")
+	}
 	return nil
 }
 

internal/consistency/diff/schema_diff.go

@@ -178,6 +178,10 @@ func (c *SchemaDiffCmd) Validate() error {
 		return fmt.Errorf("schema-diff needs at least two nodes to compare")
 	}
 
+	if c.MaxConnections < 0 {
+		return fmt.Errorf("max_connections must be >= 1 (or 0 to derive from concurrency factor)")
+	}
+
 	return nil
 }
 

internal/consistency/diff/table_diff.go

@@ -729,7 +729,7 @@ func (t *TableDiffTask) Validate() error {
 	}
 
 	cfg := config.Get()
-	if t.MaxConnections == 0 && cfg.TableDiff.MaxConnections > 0 {
+	if t.MaxConnections == 0 {
 		t.MaxConnections = cfg.TableDiff.MaxConnections
 	}
 	if t.MaxConnections < 0 {

internal/jobs/config.go

@@ -109,9 +109,7 @@ func buildTableDiffJob(cfg *config.Config, def config.JobDef, spec scheduleSpec)
 	if v := intArg(def.Args, "max_diff_rows", 0); v > 0 {
 		base.MaxDiffRows = int64(v)
 	}
-	if v := intArg(def.Args, "max_connections", 0); v > 0 {
-		base.MaxConnections = v
-	}
+	base.MaxConnections = intArg(def.Args, "max_connections", 0)
 	if out := stringArg(def.Args, "output"); out != "" {
 		base.Output = out
 	}
@@ -187,9 +185,7 @@ func buildSchemaDiffJob(cfg *config.Config, def config.JobDef, spec scheduleSpec
 	if v := intArg(def.Args, "compare_unit_size", 0); v > 0 {
 		base.CompareUnitSize = v
 	}
-	if v := intArg(def.Args, "max_connections", 0); v > 0 {
-		base.MaxConnections = v
-	}
+	base.MaxConnections = intArg(def.Args, "max_connections", 0)
 	if out := stringArg(def.Args, "output"); out != "" {
 		base.Output = out
 	}
@@ -264,9 +260,7 @@ func buildRepsetDiffJob(cfg *config.Config, def config.JobDef, spec scheduleSpec
 	if out := stringArg(def.Args, "output"); out != "" {
 		base.Output = out
 	}
-	if v := intArg(def.Args, "max_connections", 0); v > 0 {
-		base.MaxConnections = v
-	}
+	base.MaxConnections = intArg(def.Args, "max_connections", 0)
 	base.TableFilter = stringArg(def.Args, "table_filter")
 	base.OverrideBlockSize = boolArg(def.Args, "override_block_size", base.OverrideBlockSize)
 	base.SkipDBUpdate = boolArg(def.Args, "skip_db_update", base.SkipDBUpdate)