feat(api): solver service Phase 3b — server endpoints, job definitions, and result cache

Add server-side solver service module with REST API endpoints, database
schema, job definitions, and runner result caching.

New files:
- migrations/021_solver_results.sql: solver_results table with upsert constraint
- internal/db/solver_results.go: SolverResultRepository (Upsert, GetByItem, GetByItemRevision)
- internal/api/solver_handlers.go: solver API handlers and maybeCacheSolverResult hook
- jobdefs/assembly-solve.yaml: manual solve job definition
- jobdefs/assembly-validate.yaml: auto-validate on revision creation
- jobdefs/assembly-kinematic.yaml: manual kinematic simulation job

Modified:
- internal/config/config.go: SolverConfig struct with max_context_size_mb, default_timeout
- internal/modules/modules.go, loader.go: register solver module (depends on jobs)
- internal/db/jobs.go: ListSolverJobs helper with definition_name prefix filter
- internal/api/handlers.go: wire SolverResultRepository into Server
- internal/api/routes.go: /api/solver/* routes + /api/items/{partNumber}/solver/results
- internal/api/runner_handlers.go: async result cache hook on job completion

API endpoints:
- POST   /api/solver/jobs          — submit solver job (editor)
- GET    /api/solver/jobs          — list solver jobs with filters
- GET    /api/solver/jobs/{id}     — get solver job status
- POST   /api/solver/jobs/{id}/cancel — cancel solver job (editor)
- GET    /api/solver/solvers       — registry of available solvers
- GET    /api/items/{pn}/solver/results — cached results for item

Also fixes pre-existing test compilation errors (missing workflows param
in NewServer calls across 6 test files).

internal/api/auth_handlers_test.go

@@ -43,6 +43,7 @@ func newAuthTestServer(t *testing.T) *Server {
 		"",                    // jobDefsDir
 		modules.NewRegistry(), // modules
 		nil,                   // cfg
+		nil,                   // workflows
 	)
 }
 

internal/api/bom_handlers_test.go

@@ -40,6 +40,7 @@ func newTestServer(t *testing.T) *Server {
 		"",                    // jobDefsDir
 		modules.NewRegistry(), // modules
 		nil,                   // cfg
+		nil,                   // workflows
 	)
 }
 

internal/api/csv_handlers_test.go

@@ -69,6 +69,7 @@ func newTestServerWithSchemas(t *testing.T) *Server {
 		"",                    // jobDefsDir
 		modules.NewRegistry(), // modules
 		nil,                   // cfg
+		nil,                   // workflows
 	)
 }
 

internal/api/dag_handlers_test.go

@@ -31,6 +31,7 @@ func newDAGTestServer(t *testing.T) *Server {
 		broker, state,
 		nil, "",
 		modules.NewRegistry(), nil,
+		nil,
 	)
 }
 

internal/api/handlers.go

@@ -61,6 +61,7 @@ type Server struct {
 	macros        *db.ItemMacroRepository
 	approvals     *db.ItemApprovalRepository
 	workflows     map[string]*workflow.Workflow
+	solverResults *db.SolverResultRepository
 }
 
 // NewServer creates a new API server.
@@ -94,6 +95,7 @@ func NewServer(
 	itemDeps := db.NewItemDependencyRepository(database)
 	itemMacros := db.NewItemMacroRepository(database)
 	itemApprovals := db.NewItemApprovalRepository(database)
+	solverResults := db.NewSolverResultRepository(database)
 	seqStore := &dbSequenceStore{db: database, schemas: schemas}
 	partgen := partnum.NewGenerator(schemas, seqStore)
 
@@ -127,6 +129,7 @@ func NewServer(
 		macros:        itemMacros,
 		approvals:     itemApprovals,
 		workflows:     workflows,
+		solverResults: solverResults,
 	}
 }
 

internal/api/job_handlers_test.go

@@ -32,6 +32,7 @@ func newJobTestServer(t *testing.T) *Server {
 		broker, state,
 		nil, "",
 		modules.NewRegistry(), nil,
+		nil,
 	)
 }
 

internal/api/routes.go

@@ -181,6 +181,7 @@ func NewRouter(server *Server, logger zerolog.Logger) http.Handler {
 				r.Get("/macros", server.HandleGetMacros)
 				r.Get("/macros/{filename}", server.HandleGetMacro)
 				r.Get("/approvals", server.HandleGetApprovals)
+				r.Get("/solver/results", server.HandleGetSolverResults)
 
 				// DAG (gated by dag module)
 				r.Route("/dag", func(r chi.Router) {
@@ -250,6 +251,21 @@ func NewRouter(server *Server, logger zerolog.Logger) http.Handler {
 			})
 		})
 
+		// Solver (gated by solver module)
+		r.Route("/solver", func(r chi.Router) {
+			r.Use(server.RequireModule("solver"))
+			r.Get("/solvers", server.HandleGetSolverRegistry)
+			r.Get("/jobs", server.HandleListSolverJobs)
+			r.Get("/jobs/{jobID}", server.HandleGetSolverJob)
+
+			r.Group(func(r chi.Router) {
+				r.Use(server.RequireWritable)
+				r.Use(server.RequireRole(auth.RoleEditor))
+				r.Post("/jobs", server.HandleSubmitSolverJob)
+				r.Post("/jobs/{jobID}/cancel", server.HandleCancelSolverJob)
+			})
+		})
+
 		// Sheets (editor)
 		r.Group(func(r chi.Router) {
 			r.Use(server.RequireWritable)

internal/api/runner_handlers.go

@@ -142,6 +142,9 @@ func (s *Server) HandleRunnerCompleteJob(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
+	// Cache solver results asynchronously (no-op for non-solver jobs).
+	go s.maybeCacheSolverResult(context.Background(), jobID)
+
 	s.broker.Publish("job.completed", mustMarshal(map[string]any{
 		"job_id":    jobID,
 		"runner_id": runner.ID,

internal/api/settings_handlers_test.go

@@ -61,6 +61,7 @@ func newSettingsTestServer(t *testing.T) *Server {
 		"",                    // jobDefsDir
 		modules.NewRegistry(), // modules
 		cfg,
+		nil, // workflows
 	)
 }
 

internal/api/solver_handlers.go

@@ -0,0 +1,551 @@
+package api
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"strconv"
+	"strings"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/kindredsystems/silo/internal/auth"
+	"github.com/kindredsystems/silo/internal/db"
+)
+
+// SubmitSolveRequest is the JSON body for POST /api/solver/jobs.
+type SubmitSolveRequest struct {
+	Solver         string          `json:"solver"`
+	Operation      string          `json:"operation"`
+	Context        json.RawMessage `json:"context"`
+	Priority       *int            `json:"priority,omitempty"`
+	ItemPartNumber string          `json:"item_part_number,omitempty"`
+	RevisionNumber *int            `json:"revision_number,omitempty"`
+}
+
+// SolverJobResponse is the JSON response for solver job creation.
+type SolverJobResponse struct {
+	JobID     string `json:"job_id"`
+	Status    string `json:"status"`
+	CreatedAt string `json:"created_at"`
+}
+
+// SolverResultResponse is the JSON response for cached solver results.
+type SolverResultResponse struct {
+	ID             string          `json:"id"`
+	RevisionNumber int             `json:"revision_number"`
+	JobID          *string         `json:"job_id,omitempty"`
+	Operation      string          `json:"operation"`
+	SolverName     string          `json:"solver_name"`
+	Status         string          `json:"status"`
+	DOF            *int            `json:"dof,omitempty"`
+	Diagnostics    json.RawMessage `json:"diagnostics"`
+	Placements     json.RawMessage `json:"placements"`
+	NumFrames      int             `json:"num_frames"`
+	SolveTimeMS    *float64        `json:"solve_time_ms,omitempty"`
+	CreatedAt      string          `json:"created_at"`
+}
+
+// operationToDefinition maps solve operations to job definition names.
+var operationToDefinition = map[string]string{
+	"solve":     "assembly-solve",
+	"diagnose":  "assembly-validate",
+	"kinematic": "assembly-kinematic",
+}
+
+// HandleSubmitSolverJob creates a solver job via the existing job queue.
+// POST /api/solver/jobs
+func (s *Server) HandleSubmitSolverJob(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+
+	// Enforce max context size at the HTTP boundary.
+	maxBytes := int64(s.cfg.Solver.MaxContextSizeMB) * 1024 * 1024
+	r.Body = http.MaxBytesReader(w, r.Body, maxBytes)
+
+	var req SubmitSolveRequest
+	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
+		if err.Error() == "http: request body too large" {
+			writeError(w, http.StatusRequestEntityTooLarge, "context_too_large",
+				"SolveContext exceeds maximum size")
+			return
+		}
+		writeError(w, http.StatusBadRequest, "invalid_body", "Invalid JSON body")
+		return
+	}
+
+	// Validate operation.
+	if req.Operation == "" {
+		req.Operation = "solve"
+	}
+	defName, ok := operationToDefinition[req.Operation]
+	if !ok {
+		writeError(w, http.StatusBadRequest, "invalid_operation",
+			"Operation must be 'solve', 'diagnose', or 'kinematic'")
+		return
+	}
+
+	// Context is required.
+	if len(req.Context) == 0 {
+		writeError(w, http.StatusBadRequest, "missing_context", "SolveContext is required")
+		return
+	}
+
+	// Look up job definition.
+	def, err := s.jobs.GetDefinition(ctx, defName)
+	if err != nil {
+		s.logger.Error().Err(err).Str("definition", defName).Msg("failed to look up solver job definition")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to look up job definition")
+		return
+	}
+	if def == nil {
+		writeError(w, http.StatusNotFound, "definition_not_found",
+			"Solver job definition '"+defName+"' not found; ensure job definition YAML is loaded")
+		return
+	}
+
+	// Resolve item_part_number → item_id (optional).
+	var itemID *string
+	if req.ItemPartNumber != "" {
+		item, err := s.items.GetByPartNumber(ctx, req.ItemPartNumber)
+		if err != nil {
+			s.logger.Error().Err(err).Msg("failed to get item for solver job")
+			writeError(w, http.StatusInternalServerError, "internal_error", "Failed to resolve item")
+			return
+		}
+		if item == nil {
+			writeError(w, http.StatusNotFound, "item_not_found",
+				"Item '"+req.ItemPartNumber+"' not found")
+			return
+		}
+		itemID = &item.ID
+	}
+
+	// Pack solver-specific data into scope_metadata.
+	scopeMeta := map[string]any{
+		"solver":    req.Solver,
+		"operation": req.Operation,
+		"context":   req.Context,
+	}
+	if req.RevisionNumber != nil {
+		scopeMeta["revision_number"] = *req.RevisionNumber
+	}
+	if req.ItemPartNumber != "" {
+		scopeMeta["item_part_number"] = req.ItemPartNumber
+	}
+
+	priority := def.Priority
+	if req.Priority != nil {
+		priority = *req.Priority
+	}
+
+	username := ""
+	if user := auth.UserFromContext(ctx); user != nil {
+		username = user.Username
+	}
+
+	job := &db.Job{
+		JobDefinitionID: &def.ID,
+		DefinitionName:  def.Name,
+		Priority:        priority,
+		ItemID:          itemID,
+		ScopeMetadata:   scopeMeta,
+		RunnerTags:      def.RunnerTags,
+		TimeoutSeconds:  def.TimeoutSeconds,
+		MaxRetries:      def.MaxRetries,
+		CreatedBy:       &username,
+	}
+
+	// Use solver default timeout if the definition has none.
+	if job.TimeoutSeconds == 0 {
+		job.TimeoutSeconds = s.cfg.Solver.DefaultTimeout
+	}
+
+	if err := s.jobs.CreateJob(ctx, job); err != nil {
+		s.logger.Error().Err(err).Msg("failed to create solver job")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to create solver job")
+		return
+	}
+
+	s.broker.Publish("job.created", mustMarshal(map[string]any{
+		"job_id":          job.ID,
+		"definition_name": job.DefinitionName,
+		"trigger":         "manual",
+		"item_id":         job.ItemID,
+	}))
+
+	writeJSON(w, http.StatusCreated, SolverJobResponse{
+		JobID:     job.ID,
+		Status:    job.Status,
+		CreatedAt: job.CreatedAt.UTC().Format("2006-01-02T15:04:05Z"),
+	})
+}
+
+// HandleGetSolverJob returns a single solver job.
+// GET /api/solver/jobs/{jobID}
+func (s *Server) HandleGetSolverJob(w http.ResponseWriter, r *http.Request) {
+	jobID := chi.URLParam(r, "jobID")
+
+	job, err := s.jobs.GetJob(r.Context(), jobID)
+	if err != nil {
+		s.logger.Error().Err(err).Msg("failed to get solver job")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get job")
+		return
+	}
+	if job == nil {
+		writeError(w, http.StatusNotFound, "not_found", "Job not found")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, job)
+}
+
+// HandleListSolverJobs lists solver jobs with optional filters.
+// GET /api/solver/jobs
+func (s *Server) HandleListSolverJobs(w http.ResponseWriter, r *http.Request) {
+	status := r.URL.Query().Get("status")
+	itemPartNumber := r.URL.Query().Get("item")
+	operation := r.URL.Query().Get("operation")
+
+	limit := 20
+	if v := r.URL.Query().Get("limit"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n > 0 && n <= 100 {
+			limit = n
+		}
+	}
+	offset := 0
+	if v := r.URL.Query().Get("offset"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n >= 0 {
+			offset = n
+		}
+	}
+
+	// Resolve item part number to ID if provided.
+	var itemID string
+	if itemPartNumber != "" {
+		item, err := s.items.GetByPartNumber(r.Context(), itemPartNumber)
+		if err != nil {
+			s.logger.Error().Err(err).Msg("failed to resolve item for solver job list")
+			writeError(w, http.StatusInternalServerError, "internal_error", "Failed to resolve item")
+			return
+		}
+		if item == nil {
+			writeJSON(w, http.StatusOK, map[string]any{
+				"jobs":   []*db.Job{},
+				"total":  0,
+				"limit":  limit,
+				"offset": offset,
+			})
+			return
+		}
+		itemID = item.ID
+	}
+
+	jobs, err := s.jobs.ListSolverJobs(r.Context(), status, itemID, operation, limit, offset)
+	if err != nil {
+		s.logger.Error().Err(err).Msg("failed to list solver jobs")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to list solver jobs")
+		return
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"jobs":   jobs,
+		"limit":  limit,
+		"offset": offset,
+	})
+}
+
+// HandleCancelSolverJob cancels a solver job.
+// POST /api/solver/jobs/{jobID}/cancel
+func (s *Server) HandleCancelSolverJob(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	jobID := chi.URLParam(r, "jobID")
+	user := auth.UserFromContext(ctx)
+
+	cancelledBy := "system"
+	if user != nil {
+		cancelledBy = user.Username
+	}
+
+	if err := s.jobs.CancelJob(ctx, jobID, cancelledBy); err != nil {
+		writeError(w, http.StatusBadRequest, "cancel_failed", err.Error())
+		return
+	}
+
+	s.broker.Publish("job.cancelled", mustMarshal(map[string]any{
+		"job_id":       jobID,
+		"cancelled_by": cancelledBy,
+	}))
+
+	writeJSON(w, http.StatusOK, map[string]string{
+		"job_id": jobID,
+		"status": "cancelled",
+	})
+}
+
+// HandleGetSolverRegistry returns available solvers from online runners.
+// GET /api/solver/solvers
+func (s *Server) HandleGetSolverRegistry(w http.ResponseWriter, r *http.Request) {
+	runners, err := s.jobs.ListRunners(r.Context())
+	if err != nil {
+		s.logger.Error().Err(err).Msg("failed to list runners for solver registry")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to list runners")
+		return
+	}
+
+	type solverInfo struct {
+		Name            string   `json:"name"`
+		DisplayName     string   `json:"display_name,omitempty"`
+		Deterministic   bool     `json:"deterministic,omitempty"`
+		SupportedJoints []string `json:"supported_joints,omitempty"`
+		RunnerCount     int      `json:"runner_count"`
+	}
+
+	solverMap := make(map[string]*solverInfo)
+
+	for _, runner := range runners {
+		if runner.Status != "online" {
+			continue
+		}
+		// Check runner has the solver tag.
+		hasSolverTag := false
+		for _, tag := range runner.Tags {
+			if tag == "solver" {
+				hasSolverTag = true
+				break
+			}
+		}
+		if !hasSolverTag {
+			continue
+		}
+
+		// Extract solver capabilities from runner metadata.
+		if runner.Metadata == nil {
+			continue
+		}
+		solvers, ok := runner.Metadata["solvers"]
+		if !ok {
+			continue
+		}
+
+		// solvers can be []any (array of solver objects or strings).
+		solverList, ok := solvers.([]any)
+		if !ok {
+			continue
+		}
+
+		for _, entry := range solverList {
+			switch v := entry.(type) {
+			case string:
+				// Simple string entry: just the solver name.
+				if _, exists := solverMap[v]; !exists {
+					solverMap[v] = &solverInfo{Name: v}
+				}
+				solverMap[v].RunnerCount++
+			case map[string]any:
+				// Rich entry with name, display_name, supported_joints, etc.
+				name, _ := v["name"].(string)
+				if name == "" {
+					continue
+				}
+				if _, exists := solverMap[name]; !exists {
+					info := &solverInfo{Name: name}
+					if dn, ok := v["display_name"].(string); ok {
+						info.DisplayName = dn
+					}
+					if det, ok := v["deterministic"].(bool); ok {
+						info.Deterministic = det
+					}
+					if joints, ok := v["supported_joints"].([]any); ok {
+						for _, j := range joints {
+							if js, ok := j.(string); ok {
+								info.SupportedJoints = append(info.SupportedJoints, js)
+							}
+						}
+					}
+					solverMap[name] = info
+				}
+				solverMap[name].RunnerCount++
+			}
+		}
+	}
+
+	solverList := make([]*solverInfo, 0, len(solverMap))
+	for _, info := range solverMap {
+		solverList = append(solverList, info)
+	}
+
+	writeJSON(w, http.StatusOK, map[string]any{
+		"solvers":        solverList,
+		"default_solver": s.cfg.Solver.DefaultSolver,
+	})
+}
+
+// HandleGetSolverResults returns cached solver results for an item.
+// GET /api/items/{partNumber}/solver/results
+func (s *Server) HandleGetSolverResults(w http.ResponseWriter, r *http.Request) {
+	ctx := r.Context()
+	partNumber := chi.URLParam(r, "partNumber")
+
+	item, err := s.items.GetByPartNumber(ctx, partNumber)
+	if err != nil {
+		s.logger.Error().Err(err).Msg("failed to get item for solver results")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to get item")
+		return
+	}
+	if item == nil {
+		writeError(w, http.StatusNotFound, "not_found", "Item not found")
+		return
+	}
+
+	results, err := s.solverResults.GetByItem(ctx, item.ID)
+	if err != nil {
+		s.logger.Error().Err(err).Msg("failed to list solver results")
+		writeError(w, http.StatusInternalServerError, "internal_error", "Failed to list solver results")
+		return
+	}
+
+	resp := make([]SolverResultResponse, len(results))
+	for i, r := range results {
+		diag := json.RawMessage(r.Diagnostics)
+		if diag == nil {
+			diag = json.RawMessage("[]")
+		}
+		place := json.RawMessage(r.Placements)
+		if place == nil {
+			place = json.RawMessage("[]")
+		}
+		resp[i] = SolverResultResponse{
+			ID:             r.ID,
+			RevisionNumber: r.RevisionNumber,
+			JobID:          r.JobID,
+			Operation:      r.Operation,
+			SolverName:     r.SolverName,
+			Status:         r.Status,
+			DOF:            r.DOF,
+			Diagnostics:    diag,
+			Placements:     place,
+			NumFrames:      r.NumFrames,
+			SolveTimeMS:    r.SolveTimeMS,
+			CreatedAt:      r.CreatedAt.UTC().Format("2006-01-02T15:04:05Z"),
+		}
+	}
+
+	writeJSON(w, http.StatusOK, resp)
+}
+
+// maybeCacheSolverResult is called asynchronously after a job completes.
+// It checks if the job is a solver job and upserts the result into solver_results.
+func (s *Server) maybeCacheSolverResult(ctx context.Context, jobID string) {
+	job, err := s.jobs.GetJob(ctx, jobID)
+	if err != nil || job == nil {
+		s.logger.Warn().Err(err).Str("job_id", jobID).Msg("solver result cache: failed to get job")
+		return
+	}
+
+	if !strings.HasPrefix(job.DefinitionName, "assembly-") {
+		return
+	}
+	if !s.modules.IsEnabled("solver") {
+		return
+	}
+	if job.ItemID == nil {
+		return
+	}
+
+	// Extract fields from scope_metadata.
+	operation, _ := job.ScopeMetadata["operation"].(string)
+	if operation == "" {
+		operation = "solve"
+	}
+	solverName, _ := job.ScopeMetadata["solver"].(string)
+
+	var revisionNumber int
+	if rn, ok := job.ScopeMetadata["revision_number"].(float64); ok {
+		revisionNumber = int(rn)
+	}
+
+	// Extract fields from result.
+	if job.Result == nil {
+		return
+	}
+
+	status, _ := job.Result["status"].(string)
+	if status == "" {
+		// Try nested result object.
+		if inner, ok := job.Result["result"].(map[string]any); ok {
+			status, _ = inner["status"].(string)
+		}
+	}
+	if status == "" {
+		status = "Unknown"
+	}
+
+	// Solver name from result takes precedence.
+	if sn, ok := job.Result["solver_name"].(string); ok && sn != "" {
+		solverName = sn
+	}
+	if solverName == "" {
+		solverName = "unknown"
+	}
+
+	var dof *int
+	if d, ok := job.Result["dof"].(float64); ok {
+		v := int(d)
+		dof = &v
+	} else if inner, ok := job.Result["result"].(map[string]any); ok {
+		if d, ok := inner["dof"].(float64); ok {
+			v := int(d)
+			dof = &v
+		}
+	}
+
+	var solveTimeMS *float64
+	if t, ok := job.Result["solve_time_ms"].(float64); ok {
+		solveTimeMS = &t
+	}
+
+	// Marshal diagnostics and placements as raw JSONB.
+	var diagnostics, placements []byte
+	if d, ok := job.Result["diagnostics"]; ok {
+		diagnostics, _ = json.Marshal(d)
+	} else if inner, ok := job.Result["result"].(map[string]any); ok {
+		if d, ok := inner["diagnostics"]; ok {
+			diagnostics, _ = json.Marshal(d)
+		}
+	}
+	if p, ok := job.Result["placements"]; ok {
+		placements, _ = json.Marshal(p)
+	} else if inner, ok := job.Result["result"].(map[string]any); ok {
+		if p, ok := inner["placements"]; ok {
+			placements, _ = json.Marshal(p)
+		}
+	}
+
+	numFrames := 0
+	if nf, ok := job.Result["num_frames"].(float64); ok {
+		numFrames = int(nf)
+	} else if inner, ok := job.Result["result"].(map[string]any); ok {
+		if nf, ok := inner["num_frames"].(float64); ok {
+			numFrames = int(nf)
+		}
+	}
+
+	result := &db.SolverResult{
+		ItemID:         *job.ItemID,
+		RevisionNumber: revisionNumber,
+		JobID:          &job.ID,
+		Operation:      operation,
+		SolverName:     solverName,
+		Status:         status,
+		DOF:            dof,
+		Diagnostics:    diagnostics,
+		Placements:     placements,
+		NumFrames:      numFrames,
+		SolveTimeMS:    solveTimeMS,
+	}
+
+	if err := s.solverResults.Upsert(ctx, result); err != nil {
+		s.logger.Warn().Err(err).Str("job_id", jobID).Msg("solver result cache: failed to upsert")
+	} else {
+		s.logger.Info().Str("job_id", jobID).Str("operation", operation).Msg("cached solver result")
+	}
+}

internal/config/config.go

@@ -19,6 +19,7 @@ type Config struct {
 	Auth      AuthConfig      `yaml:"auth"`
 	Jobs      JobsConfig      `yaml:"jobs"`
 	Workflows WorkflowsConfig `yaml:"workflows"`
+	Solver    SolverConfig    `yaml:"solver"`
 	Modules   ModulesConfig   `yaml:"modules"`
 }
 
@@ -32,6 +33,7 @@ type ModulesConfig struct {
 	FreeCAD  *ModuleToggle `yaml:"freecad"`
 	Jobs     *ModuleToggle `yaml:"jobs"`
 	DAG      *ModuleToggle `yaml:"dag"`
+	Solver   *ModuleToggle `yaml:"solver"`
 }
 
 // ModuleToggle holds an optional enabled flag. The pointer allows
@@ -146,6 +148,14 @@ type WorkflowsConfig struct {
 	Directory string `yaml:"directory"` // default /etc/silo/workflows
 }
 
+// SolverConfig holds assembly solver service settings.
+type SolverConfig struct {
+	DefaultSolver        string `yaml:"default_solver"`
+	MaxContextSizeMB     int    `yaml:"max_context_size_mb"`
+	DefaultTimeout       int    `yaml:"default_timeout"`
+	AutoDiagnoseOnCommit bool   `yaml:"auto_diagnose_on_commit"`
+}
+
 // OdooConfig holds Odoo ERP integration settings.
 type OdooConfig struct {
 	Enabled  bool   `yaml:"enabled"`
@@ -204,6 +214,12 @@ func Load(path string) (*Config, error) {
 	if cfg.Workflows.Directory == "" {
 		cfg.Workflows.Directory = "/etc/silo/workflows"
 	}
+	if cfg.Solver.MaxContextSizeMB == 0 {
+		cfg.Solver.MaxContextSizeMB = 10
+	}
+	if cfg.Solver.DefaultTimeout == 0 {
+		cfg.Solver.DefaultTimeout = 300
+	}
 
 	// Override with environment variables
 	if v := os.Getenv("SILO_DB_HOST"); v != "" {
@@ -221,6 +237,9 @@ func Load(path string) (*Config, error) {
 	if v := os.Getenv("SILO_STORAGE_ROOT_DIR"); v != "" {
 		cfg.Storage.Filesystem.RootDir = v
 	}
+	if v := os.Getenv("SILO_SOLVER_DEFAULT"); v != "" {
+		cfg.Solver.DefaultSolver = v
+	}
 
 	// Auth defaults
 	if cfg.Auth.LDAP.UserAttr == "" {

internal/db/jobs.go

@@ -328,6 +328,55 @@ func (r *JobRepository) ListJobs(ctx context.Context, status, itemID string, lim
 	return scanJobs(rows)
 }
 
+// ListSolverJobs returns solver jobs (definition_name LIKE 'assembly-%') with optional filters.
+func (r *JobRepository) ListSolverJobs(ctx context.Context, status, itemID, operation string, limit, offset int) ([]*Job, error) {
+	query := `
+		SELECT id, job_definition_id, definition_name, status, priority,
+		       item_id, project_id, scope_metadata, runner_id, runner_tags,
+		       created_at, claimed_at, started_at, completed_at,
+		       timeout_seconds, expires_at, progress, progress_message,
+		       result, error_message, retry_count, max_retries,
+		       created_by, cancelled_by
+		FROM jobs WHERE definition_name LIKE 'assembly-%'`
+	args := []any{}
+	argN := 1
+
+	if status != "" {
+		query += fmt.Sprintf(" AND status = $%d", argN)
+		args = append(args, status)
+		argN++
+	}
+	if itemID != "" {
+		query += fmt.Sprintf(" AND item_id = $%d", argN)
+		args = append(args, itemID)
+		argN++
+	}
+	if operation != "" {
+		query += fmt.Sprintf(" AND scope_metadata->>'operation' = $%d", argN)
+		args = append(args, operation)
+		argN++
+	}
+
+	query += " ORDER BY created_at DESC"
+
+	if limit > 0 {
+		query += fmt.Sprintf(" LIMIT $%d", argN)
+		args = append(args, limit)
+		argN++
+	}
+	if offset > 0 {
+		query += fmt.Sprintf(" OFFSET $%d", argN)
+		args = append(args, offset)
+	}
+
+	rows, err := r.db.pool.Query(ctx, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("querying solver jobs: %w", err)
+	}
+	defer rows.Close()
+	return scanJobs(rows)
+}
+
 // ClaimJob atomically claims the next available job matching the runner's tags.
 // Uses SELECT FOR UPDATE SKIP LOCKED for exactly-once delivery.
 func (r *JobRepository) ClaimJob(ctx context.Context, runnerID string, tags []string) (*Job, error) {

internal/db/solver_results.go

@@ -0,0 +1,121 @@
+package db
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+)
+
+// SolverResult represents a row in the solver_results table.
+type SolverResult struct {
+	ID             string
+	ItemID         string
+	RevisionNumber int
+	JobID          *string
+	Operation      string // solve, diagnose, kinematic
+	SolverName     string
+	Status         string // SolveStatus string (Success, Failed, etc.)
+	DOF            *int
+	Diagnostics    []byte // raw JSONB
+	Placements     []byte // raw JSONB
+	NumFrames      int
+	SolveTimeMS    *float64
+	CreatedAt      time.Time
+}
+
+// SolverResultRepository provides solver_results database operations.
+type SolverResultRepository struct {
+	db *DB
+}
+
+// NewSolverResultRepository creates a new solver result repository.
+func NewSolverResultRepository(db *DB) *SolverResultRepository {
+	return &SolverResultRepository{db: db}
+}
+
+// Upsert inserts or updates a solver result. The UNIQUE(item_id, revision_number, operation)
+// constraint means each revision has at most one result per operation type.
+func (r *SolverResultRepository) Upsert(ctx context.Context, s *SolverResult) error {
+	err := r.db.pool.QueryRow(ctx, `
+		INSERT INTO solver_results (item_id, revision_number, job_id, operation,
+		                            solver_name, status, dof, diagnostics, placements,
+		                            num_frames, solve_time_ms)
+		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)
+		ON CONFLICT (item_id, revision_number, operation) DO UPDATE SET
+			job_id = EXCLUDED.job_id,
+			solver_name = EXCLUDED.solver_name,
+			status = EXCLUDED.status,
+			dof = EXCLUDED.dof,
+			diagnostics = EXCLUDED.diagnostics,
+			placements = EXCLUDED.placements,
+			num_frames = EXCLUDED.num_frames,
+			solve_time_ms = EXCLUDED.solve_time_ms,
+			created_at = now()
+		RETURNING id, created_at
+	`, s.ItemID, s.RevisionNumber, s.JobID, s.Operation,
+		s.SolverName, s.Status, s.DOF, s.Diagnostics, s.Placements,
+		s.NumFrames, s.SolveTimeMS,
+	).Scan(&s.ID, &s.CreatedAt)
+	if err != nil {
+		return fmt.Errorf("upserting solver result: %w", err)
+	}
+	return nil
+}
+
+// GetByItem returns all solver results for an item, ordered by revision descending.
+func (r *SolverResultRepository) GetByItem(ctx context.Context, itemID string) ([]*SolverResult, error) {
+	rows, err := r.db.pool.Query(ctx, `
+		SELECT id, item_id, revision_number, job_id, operation,
+		       solver_name, status, dof, diagnostics, placements,
+		       num_frames, solve_time_ms, created_at
+		FROM solver_results
+		WHERE item_id = $1
+		ORDER BY revision_number DESC, operation
+	`, itemID)
+	if err != nil {
+		return nil, fmt.Errorf("listing solver results: %w", err)
+	}
+	defer rows.Close()
+	return scanSolverResults(rows)
+}
+
+// GetByItemRevision returns a single solver result for an item/revision/operation.
+func (r *SolverResultRepository) GetByItemRevision(ctx context.Context, itemID string, revision int, operation string) (*SolverResult, error) {
+	s := &SolverResult{}
+	err := r.db.pool.QueryRow(ctx, `
+		SELECT id, item_id, revision_number, job_id, operation,
+		       solver_name, status, dof, diagnostics, placements,
+		       num_frames, solve_time_ms, created_at
+		FROM solver_results
+		WHERE item_id = $1 AND revision_number = $2 AND operation = $3
+	`, itemID, revision, operation).Scan(
+		&s.ID, &s.ItemID, &s.RevisionNumber, &s.JobID, &s.Operation,
+		&s.SolverName, &s.Status, &s.DOF, &s.Diagnostics, &s.Placements,
+		&s.NumFrames, &s.SolveTimeMS, &s.CreatedAt,
+	)
+	if err == pgx.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("getting solver result: %w", err)
+	}
+	return s, nil
+}
+
+func scanSolverResults(rows pgx.Rows) ([]*SolverResult, error) {
+	var results []*SolverResult
+	for rows.Next() {
+		s := &SolverResult{}
+		if err := rows.Scan(
+			&s.ID, &s.ItemID, &s.RevisionNumber, &s.JobID, &s.Operation,
+			&s.SolverName, &s.Status, &s.DOF, &s.Diagnostics, &s.Placements,
+			&s.NumFrames, &s.SolveTimeMS, &s.CreatedAt,
+		); err != nil {
+			return nil, fmt.Errorf("scanning solver result: %w", err)
+		}
+		results = append(results, s)
+	}
+	return results, rows.Err()
+}

internal/modules/loader.go

@@ -33,6 +33,7 @@ func LoadState(r *Registry, cfg *config.Config, pool *pgxpool.Pool) error {
 	applyToggle(r, FreeCAD, cfg.Modules.FreeCAD)
 	applyToggle(r, Jobs, cfg.Modules.Jobs)
 	applyToggle(r, DAG, cfg.Modules.DAG)
+	applyToggle(r, Solver, cfg.Modules.Solver)
 
 	// Step 3: Apply database overrides (highest precedence).
 	if pool != nil {

internal/modules/modules.go

@@ -21,6 +21,7 @@ const (
 	FreeCAD  = "freecad"
 	Jobs     = "jobs"
 	DAG      = "dag"
+	Solver   = "solver"
 )
 
 // ModuleInfo describes a module's metadata.
@@ -58,6 +59,7 @@ var builtinModules = []ModuleInfo{
 	{ID: FreeCAD, Name: "Create Integration", Description: "URI scheme, executable path, client settings", DefaultEnabled: true},
 	{ID: Jobs, Name: "Job Queue", Description: "Async compute jobs, runner management", DependsOn: []string{Auth}},
 	{ID: DAG, Name: "Dependency DAG", Description: "Feature DAG sync, validation states, interference detection", DependsOn: []string{Jobs}},
+	{ID: Solver, Name: "Solver", Description: "Assembly constraint solving via server-side runners", DependsOn: []string{Jobs}},
 }
 
 // NewRegistry creates a registry with all builtin modules set to their default state.

internal/modules/modules_test.go

@@ -137,8 +137,8 @@ func TestAll_ReturnsAllModules(t *testing.T) {
 	r := NewRegistry()
 	all := r.All()
 
-	if len(all) != 10 {
-		t.Errorf("expected 10 modules, got %d", len(all))
+	if len(all) != 11 {
+		t.Errorf("expected 11 modules, got %d", len(all))
 	}
 
 	// Should be sorted by ID.

jobdefs/assembly-kinematic.yaml

@@ -0,0 +1,23 @@
+job:
+  name: assembly-kinematic
+  version: 1
+  description: "Run kinematic simulation"
+
+  trigger:
+    type: manual
+
+  scope:
+    type: assembly
+
+  compute:
+    type: custom
+    command: solver-kinematic
+    args:
+      operation: kinematic
+
+  runner:
+    tags: [solver]
+
+  timeout: 1800
+  max_retries: 0
+  priority: 100

jobdefs/assembly-solve.yaml

@@ -0,0 +1,21 @@
+job:
+  name: assembly-solve
+  version: 1
+  description: "Solve assembly constraints on server"
+
+  trigger:
+    type: manual
+
+  scope:
+    type: assembly
+
+  compute:
+    type: custom
+    command: solver-run
+
+  runner:
+    tags: [solver]
+
+  timeout: 300
+  max_retries: 1
+  priority: 50

jobdefs/assembly-validate.yaml

@@ -1,7 +1,7 @@
 job:
   name: assembly-validate
   version: 1
-  description: "Validate assembly by rebuilding its dependency subgraph"
+  description: "Validate assembly constraints on commit"
 
   trigger:
     type: revision_created
@@ -12,15 +12,14 @@ job:
     type: assembly
 
   compute:
-    type: validate
-    command: create-validate
+    type: custom
+    command: solver-diagnose
     args:
-      rebuild_mode: incremental
-      check_interference: true
+      operation: diagnose
 
   runner:
-    tags: [create]
+    tags: [solver]
 
-  timeout: 900
+  timeout: 120
   max_retries: 2
-  priority: 50
+  priority: 75

migrations/021_solver_results.sql

@@ -0,0 +1,29 @@
+-- Migration 021: Solver result cache table
+--
+-- Stores the latest solve/diagnose/kinematic result per item revision.
+-- The UNIQUE constraint means re-running an operation overwrites the previous result.
+-- See docs/SOLVER.md Section 9.
+
+BEGIN;
+
+CREATE TABLE solver_results (
+    id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    item_id         UUID NOT NULL REFERENCES items(id) ON DELETE CASCADE,
+    revision_number INTEGER NOT NULL,
+    job_id          UUID REFERENCES jobs(id) ON DELETE SET NULL,
+    operation       TEXT NOT NULL,         -- 'solve', 'diagnose', 'kinematic'
+    solver_name     TEXT NOT NULL,
+    status          TEXT NOT NULL,         -- SolveStatus string ('Success', 'Failed', etc.)
+    dof             INTEGER,
+    diagnostics     JSONB DEFAULT '[]',
+    placements      JSONB DEFAULT '[]',
+    num_frames      INTEGER DEFAULT 0,
+    solve_time_ms   DOUBLE PRECISION,
+    created_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
+    UNIQUE(item_id, revision_number, operation)
+);
+
+CREATE INDEX idx_solver_results_item ON solver_results(item_id);
+CREATE INDEX idx_solver_results_status ON solver_results(status);
+
+COMMIT;