Add PreparedRun model and render formatters (text/json) with tests

internal/domain/domain.go

@@ -75,6 +75,22 @@ type RunResult struct {
 	Error                error
 }
 
+// PreparedRun contains pre-LLM execution state from the prepare/render phase.
+// It must never include resolved API key values, model output, or validation data.
+type PreparedRun struct {
+	PromptID             string            `json:"prompt_id"`
+	PromptVersion        string            `json:"prompt_version,omitempty"`
+	PromptHash           string            `json:"prompt_hash,omitempty"`
+	SelectedProfileID    string            `json:"selected_profile_id"`
+	EffectiveModelParams ExecutionTarget   `json:"effective_model_params"`
+	InputHashes          map[string]string `json:"input_hashes,omitempty"`
+	RenderedPromptHash   string            `json:"rendered_prompt_hash"`
+	Messages             []RenderedMessage `json:"messages"`
+	StartTime            time.Time         `json:"start_time,omitempty"`
+	EndTime              time.Time         `json:"end_time,omitempty"`
+	DurationMS           int64             `json:"duration_ms,omitempty"`
+}
+
 // ArtifactRef represents a reference to an input artifact.
 type ArtifactRef struct {
 	Type ArtifactRefType
@@ -156,13 +172,13 @@ type OutputContract struct {
 
 // RenderedPrompt represents the prompt after template application.
 type RenderedPrompt struct {
-	Messages []RenderedMessage
+	Messages []RenderedMessage `json:"messages"`
 }
 
 // RenderedMessage is a single message in a rendered prompt.
 type RenderedMessage struct {
-	Role    string
-	Content string
+	Role    string `json:"role"`
+	Content string `json:"content"`
 }
 
 // GenerateRequest is the internal request passed to the LLM client.

internal/domain/prepared_run_test.go

@@ -0,0 +1,55 @@
+package domain
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestPreparedRunJSONDoesNotIncludeSecretValues(t *testing.T) {
+	const envName = "SCRIPTORIUM_TEST_API_KEY"
+	const secret = "super-secret-value"
+	t.Setenv(envName, secret)
+
+	prepared := PreparedRun{
+		PromptID:          "prompt.id",
+		PromptVersion:     "v1",
+		PromptHash:        "prompt-hash",
+		SelectedProfileID: "local-fast",
+		EffectiveModelParams: ExecutionTarget{
+			Endpoint:  "http://llm/v1",
+			Model:     "gpt-test",
+			APIKeyEnv: envName,
+		},
+		InputHashes:        map[string]string{"transcript": "hash-1"},
+		RenderedPromptHash: "rendered-hash",
+		Messages: []RenderedMessage{
+			{Role: "system", Content: "You are helpful."},
+			{Role: "user", Content: "Summarize this."},
+		},
+	}
+
+	b, err := json.Marshal(prepared)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+
+	out := string(b)
+	if strings.Contains(out, secret) {
+		t.Fatalf("prepared run JSON unexpectedly contains secret value: %s", out)
+	}
+	if !strings.Contains(out, `"api_key_env":"`+envName+`"`) {
+		t.Fatalf("prepared run JSON should include api_key_env name: %s", out)
+	}
+
+	var top map[string]any
+	if err := json.Unmarshal(b, &top); err != nil {
+		t.Fatalf("unmarshal failed: %v", err)
+	}
+
+	for _, forbidden := range []string{"raw_output", "validation", "artifact"} {
+		if _, ok := top[forbidden]; ok {
+			t.Fatalf("prepared run JSON should not include %q", forbidden)
+		}
+	}
+}