Capture resolved CLI model and route slug through SLUG_MODEL

Adds RunConfig.resolvedModel, populated from the CLI's `system_init`
event, so runs remain comparable across alias bumps even when the user
selected an alias like `haiku`.

Adds SLUG_MODEL alongside JUDGE_MODEL and switches slug.ts to use it,
so the slug generator can move independently from the judge — slugs
fall back gracefully and don't anchor historical comparisons.

Author: claude

src/server/runner.ts

@@ -382,6 +382,10 @@ export class Runner extends EventEmitter {
       },
     );
 
+    if (typeof raw.model === 'string' && raw.model.length > 0) {
+      this.input.initialConfig.resolvedModel = raw.model;
+    }
+
     const memoryPaths = raw.memory_paths as Record<string, unknown> | undefined;
     const auto = memoryPaths?.auto;
     if (typeof auto !== 'string' || auto.length === 0) return;

src/server/slug.ts

@@ -3,6 +3,7 @@ import { spawn } from 'node:child_process';
 import { pathExists } from './fsUtil.js';
 import { join } from 'node:path';
 import { readdir } from 'node:fs/promises';
+import { SLUG_MODEL } from '@shared/constants.js';
 import { log } from './log.js';
 
 const MAX_SLUG_LENGTH = 32;
@@ -129,7 +130,7 @@ async function tryHaikuSlug(content: string, claudeBin: string): Promise<string
         '-p',
         prompt,
         '--model',
-        'haiku',
+        SLUG_MODEL,
         '--output-format',
         'json',
         '--tools',

src/shared/constants.ts

@@ -26,6 +26,12 @@ export const PROJECT_MARKERS = [
 // when a new Haiku ships and rebaselining is acceptable.
 export const JUDGE_MODEL = 'claude-haiku-4-5';
 
+// Model used to auto-generate run-folder slugs from variant content. Kept
+// separate from JUDGE_MODEL so the slug generator can move independently —
+// slugs are non-critical (they fall back gracefully) and don't anchor any
+// historical comparison the way judge scores do.
+export const SLUG_MODEL = 'claude-haiku-4-5';
+
 // Judge input budgets (plan § Judge flow step 2).
 export const JUDGE_PROMPT_CAP_BYTES = 4 * 1024;
 export const JUDGE_VARIANT_CAP_BYTES = 8 * 1024;

src/shared/schemas/run.ts

@@ -26,6 +26,11 @@ export const RunConfigSchema = z.object({
   promptSha256: z.string(),
   prompt: z.string(),
   model: ModelIdSchema,
+  // Concrete model identifier the CLI reports in its `system_init` event.
+  // `model` above is what the user selected (often an alias like `haiku`);
+  // this captures what actually ran, so reruns across an alias bump remain
+  // comparable. Optional/nullable for back-compat with pre-existing configs.
+  resolvedModel: z.string().nullable().optional(),
   mode: ModeSchema,
   status: RunStatusSchema,
   startedAt: z.string(),

test/runner.smoke.ts

@@ -485,6 +485,9 @@ await scenario('init.json: persisted with the system init payload', async () =>
     if (typeof init.session_id !== 'string' || !init.session_id.startsWith('fake-')) {
       throw new Error(`init.json session_id unexpected: ${init.session_id}`);
     }
+    if (final.resolvedModel !== 'haiku') {
+      throw new Error(`expected resolvedModel='haiku', got ${final.resolvedModel}`);
+    }
   });
 });