fix(calculator): SSR with ?g_model so share links open the right model

packages/app/cypress/e2e/throughput-calculator.cy.ts

@@ -521,5 +521,22 @@ describe('TCO Calculator', () => {
       cy.get('[data-testid="calculator-controls"]').should('be.visible');
       cy.get('[data-testid="calculator-bar-chart"] svg .bar').should('have.length.greaterThan', 0);
     });
+
+    // Regression: SSR'd HTML must reflect the URL-supplied model so share links
+    // open straight to the right model without a flash of the default. See #430.
+    it('?g_model= seeds the model selector before client hydration', () => {
+      cy.request('/calculator?g_model=DeepSeek-V4-Pro').then((response) => {
+        expect(response.body).to.contain('DeepSeek V4 Pro 1.6T');
+        expect(response.body).not.to.contain('DeepSeek R1 0528 671B');
+      });
+    });
+
+    it('renders the URL-supplied model in the dropdown after navigating', () => {
+      cy.window().then((win) => {
+        win.localStorage.setItem('inferencex-star-modal-dismissed', String(Date.now()));
+      });
+      cy.visit('/calculator?g_model=DeepSeek-V4-Pro');
+      cy.get('[data-testid="calc-model-selector"]').should('contain.text', 'DeepSeek V4 Pro 1.6T');
+    });
   });
 });

packages/app/src/app/(dashboard)/calculator/page.tsx

@@ -1,10 +1,17 @@
 import type { Metadata } from 'next';
 
 import ThroughputCalculatorDisplay from '@/components/calculator/ThroughputCalculatorDisplay';
+import { resolveCalculatorUrlSeed } from '@/components/calculator/url-seed';
 import { tabMetadata } from '@/lib/tab-meta';
 
 export const metadata: Metadata = tabMetadata('calculator');
 
-export default function CalculatorPage() {
-  return <ThroughputCalculatorDisplay />;
+interface Props {
+  searchParams: Promise<Record<string, string | string[] | undefined>>;
+}
+
+export default async function CalculatorPage({ searchParams }: Props) {
+  const sp = await searchParams;
+  const seed = resolveCalculatorUrlSeed(sp);
+  return <ThroughputCalculatorDisplay urlSeed={seed} />;
 }

packages/app/src/components/calculator/ThroughputCalculatorDisplay.tsx

@@ -6,7 +6,8 @@ import { BarChart3, Table2 } from 'lucide-react';
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 
 import CalculatorTable from '@/components/calculator/CalculatorTable';
-import { useGlobalFilters } from '@/components/GlobalFilterContext';
+import type { CalculatorUrlSeed } from '@/components/calculator/url-seed';
+import { GlobalFilterProvider, useGlobalFilters } from '@/components/GlobalFilterContext';
 import { Badge } from '@/components/ui/badge';
 import { Card } from '@/components/ui/card';
 import { ChartButtons } from '@/components/ui/chart-buttons';
@@ -93,7 +94,22 @@ const CALCULATOR_VIEW_MODE_OPTIONS: SegmentedToggleOption<CalculatorViewMode>[]
 const CALCULATOR_MOBILE_VIEW_MODE_OPTIONS: SegmentedToggleOption<CalculatorViewMode>[] =
   CALCULATOR_VIEW_MODE_OPTIONS.map(({ testId: _testId, ...option }) => option);
 
-export default function ThroughputCalculatorDisplay() {
+export default function ThroughputCalculatorDisplay({ urlSeed }: { urlSeed?: CalculatorUrlSeed }) {
+  if (urlSeed && (urlSeed.model || urlSeed.sequence || urlSeed.precisions)) {
+    return (
+      <GlobalFilterProvider
+        initialModel={urlSeed.model}
+        initialSequence={urlSeed.sequence}
+        initialPrecisions={urlSeed.precisions}
+      >
+        <ThroughputCalculatorInner />
+      </GlobalFilterProvider>
+    );
+  }
+  return <ThroughputCalculatorInner />;
+}
+
+function ThroughputCalculatorInner() {
   const [openDropdown, setOpenDropdown] = useState<string | null>(null);
   const handleDropdownOpenChange = (dropdownKey: string) => (isOpen: boolean) => {
     if (isOpen) {

packages/app/src/components/calculator/url-seed.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it } from 'vitest';
+
+import { resolveCalculatorUrlSeed } from './url-seed';
+import { Model, Precision, Sequence } from '@/lib/data-mappings';
+
+describe('resolveCalculatorUrlSeed', () => {
+  it('returns the model when g_model is a known enum value', () => {
+    expect(resolveCalculatorUrlSeed({ g_model: 'DeepSeek-V4-Pro' })).toEqual({
+      model: Model.DeepSeek_V4_Pro,
+    });
+  });
+
+  it('ignores unknown g_model values so SSR falls back to the default', () => {
+    expect(resolveCalculatorUrlSeed({ g_model: 'not-a-model' })).toEqual({});
+  });
+
+  it('returns the sequence when i_seq is a known enum value', () => {
+    expect(resolveCalculatorUrlSeed({ i_seq: '1k/1k' })).toEqual({
+      sequence: Sequence.OneK_OneK,
+    });
+  });
+
+  it('parses i_prec as a comma-separated list, dropping unknown precisions', () => {
+    expect(resolveCalculatorUrlSeed({ i_prec: 'fp8,not-real,bf16' })).toEqual({
+      precisions: [Precision.FP8, Precision.BF16],
+    });
+  });
+
+  it('omits precisions when none of the supplied values are known', () => {
+    expect(resolveCalculatorUrlSeed({ i_prec: 'garbage' })).toEqual({});
+  });
+
+  it('combines model, sequence, and precisions from the same URL', () => {
+    expect(
+      resolveCalculatorUrlSeed({
+        g_model: 'DeepSeek-V4-Pro',
+        i_seq: '1k/8k',
+        i_prec: 'fp4,fp8',
+      }),
+    ).toEqual({
+      model: Model.DeepSeek_V4_Pro,
+      sequence: Sequence.OneK_EightK,
+      precisions: [Precision.FP4, Precision.FP8],
+    });
+  });
+
+  it('picks the first value when a param is repeated as an array', () => {
+    expect(resolveCalculatorUrlSeed({ g_model: ['DeepSeek-V4-Pro', 'GLM-5'] })).toEqual({
+      model: Model.DeepSeek_V4_Pro,
+    });
+  });
+
+  it('returns an empty seed for an empty searchParams object', () => {
+    expect(resolveCalculatorUrlSeed({})).toEqual({});
+  });
+});

packages/app/src/components/calculator/url-seed.ts

@@ -0,0 +1,56 @@
+import {
+  Model,
+  MODEL_OPTIONS,
+  Precision,
+  PRECISION_OPTIONS,
+  Sequence,
+  SEQUENCE_OPTIONS,
+} from '@/lib/data-mappings';
+
+export interface CalculatorUrlSeed {
+  model?: Model;
+  sequence?: Sequence;
+  precisions?: string[];
+}
+
+function pickString(value: string | string[] | undefined): string | undefined {
+  if (typeof value === 'string') return value;
+  if (Array.isArray(value)) return value[0];
+  return undefined;
+}
+
+/**
+ * Read the URL params that the calculator can SSR with into a typed seed.
+ * Without this, `?g_model=DeepSeek-V4-Pro` only takes effect after client
+ * hydration runs the `useLayoutEffect` in `GlobalFilterContext` — so the
+ * initial paint (and any preview/scraper that doesn't run JS) shows the
+ * default model instead of the shared one.
+ */
+export function resolveCalculatorUrlSeed(
+  sp: Record<string, string | string[] | undefined>,
+): CalculatorUrlSeed {
+  const seed: CalculatorUrlSeed = {};
+
+  const modelParam = pickString(sp.g_model);
+  if (modelParam && (MODEL_OPTIONS as readonly string[]).includes(modelParam)) {
+    seed.model = modelParam as Model;
+  }
+
+  const seqParam = pickString(sp.i_seq);
+  if (seqParam && (SEQUENCE_OPTIONS as readonly string[]).includes(seqParam)) {
+    seed.sequence = seqParam as Sequence;
+  }
+
+  const precParam = pickString(sp.i_prec);
+  if (precParam) {
+    const precs = precParam
+      .split(',')
+      .filter((p) => (PRECISION_OPTIONS as readonly string[]).includes(p));
+    if (precs.length > 0) seed.precisions = precs;
+  }
+
+  return seed;
+}
+
+// Re-export Model/Precision/Sequence for callers that already import this module.
+export { Model, Precision, Sequence };