diff --git a/docs/COST_YIELD_ESTIMATOR.md b/docs/COST_YIELD_ESTIMATOR.md
new file mode 100644
index 00000000..920862ce
--- /dev/null
+++ b/docs/COST_YIELD_ESTIMATOR.md
@@ -0,0 +1,62 @@
+# Cost and Yield Estimator
+
+Live estimator panel in `CreateCommitmentStepConfigure` that shows projected yield range and worst-case penalty as the user adjusts commitment parameters.
+
+## Overview
+
+The `CostYieldEstimator` component reacts to changes in `amount`, `durationDays`, `maxLossPercent`, and `asset`, debounces updates (300 ms), and displays three key figures:
+
+- **Projected Yield (est.)** — low-to-high range based on protocol APY heuristics and duration.
+- **Worst-case Penalty (est.)** — maximum early-exit penalty derived from protocol constants.
+- **Platform Fee (est.)** — platform fee percentage applied to the committed amount.
+
+All figures are labeled as estimates and sourced from `/api/protocol/constants` (see `src/utils/protocol.ts`) rather than hardcoded values.
+
+## Props / API
+
+```ts
+interface CostYieldEstimatorProps {
+  amount: string | number   // commitment amount
+  durationDays: number      // commitment duration in days (1–365)
+  maxLossPercent: number    // maximum acceptable loss percent (0–100)
+  asset: string             // asset ticker shown in labels (e.g. "XLM", "USDC")
+}
+```
+
+## Usage
+
+```tsx
+import CostYieldEstimator from '@/components/create/CostYieldEstimator'
+
+<CostYieldEstimator
+  amount={amount}
+  durationDays={durationDays}
+  maxLossPercent={maxLossPercent}
+  asset={asset}
+/>
+```
+
+The component is already integrated into `CreateCommitmentStepConfigure.tsx` between the `AllocationConstraintsEditor` and the Advanced Risk Parameters section.
+
+## Accessibility
+
+- The section has `aria-label="Cost and yield estimator"` and `aria-live="polite"` so screen readers announce value changes without interrupting the user.
+- All estimate rows use `<dl>/<dt>/<dd>` semantics for term/value pairing.
+- A placeholder paragraph is shown (and announced) when inputs are invalid or constants are loading.
+
+## Edge Cases
+
+| Scenario | Behaviour |
+|---|---|
+| `amount` is empty or zero | Placeholder shown |
+| `durationDays < 1` | Placeholder shown |
+| Protocol constants fetch fails | Placeholder shown; no error thrown |
+| `penalties` array is empty | Falls back to `maxLossPercent` for worst-case |
+
+## Related
+
+- `src/components/create/CostYieldEstimator.tsx` — component implementation
+- `src/components/create/CostYieldEstimator.test.tsx` — tests
+- `src/utils/protocol.ts` — `fetchProtocolConstants` helper
+- `src/app/api/protocol/constants/route.ts` — constants API endpoint
+- `docs/ALLOCATION_CONSTRAINTS_EDITOR.md` — sibling panel
diff --git a/src/components/CreateCommitmentStepConfigure.tsx b/src/components/CreateCommitmentStepConfigure.tsx
index 203c2ca1..50758b10 100644
--- a/src/components/CreateCommitmentStepConfigure.tsx
+++ b/src/components/CreateCommitmentStepConfigure.tsx
@@ -3,6 +3,7 @@
 import React, { useState, useRef, useEffect } from 'react'
 import WizardStepper from './WizardStepper'
 import AllocationConstraintsEditor from './create/AllocationConstraintsEditor'
+import CostYieldEstimator from './create/CostYieldEstimator'
 import styles from './CreateCommitmentStepConfigure.module.css'
 import GlossaryTerm from './GlossaryTerm'
 
@@ -349,6 +350,14 @@ export default function CreateCommitmentStepConfigure({
             onChangeMaxLoss={onChangeMaxLoss}
           />
 
+          {/* Live Cost and Yield Estimator */}
+          <CostYieldEstimator
+            amount={amount}
+            durationDays={durationDays}
+            maxLossPercent={maxLossPercent}
+            asset={asset}
+          />
+
           {/* Advanced Risk Settings */}
           <div className={styles.advancedToggleContainer}>
             <button
diff --git a/src/components/create/CostYieldEstimator.test.tsx b/src/components/create/CostYieldEstimator.test.tsx
new file mode 100644
index 00000000..2fe3000e
--- /dev/null
+++ b/src/components/create/CostYieldEstimator.test.tsx
@@ -0,0 +1,165 @@
+/**
+ * @vitest-environment happy-dom
+ */
+
+import React from 'react'
+import { render, screen, act, waitFor } from '@testing-library/react'
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import CostYieldEstimator from './CostYieldEstimator'
+
+const mockConstants = {
+  protocolVersion: '1.0.0',
+  network: 'testnet',
+  fees: { networkBaseFeeStroops: 100, platformFeePercent: 1 },
+  penalties: [
+    { type: 'early_exit', earlyExitPenaltyPercent: 5, description: 'Early exit' },
+    { type: 'aggressive', earlyExitPenaltyPercent: 15, description: 'Aggressive early exit' },
+  ],
+  commitmentLimits: {
+    minAmountXlm: 10,
+    maxAmountXlm: 1_000_000,
+    minDurationDays: 1,
+    maxDurationDays: 365,
+    maxLossPercentCeiling: 100,
+  },
+  cachedAt: new Date().toISOString(),
+}
+
+beforeEach(() => {
+  vi.useFakeTimers()
+  global.fetch = vi.fn().mockResolvedValue({
+    ok: true,
+    json: () => Promise.resolve(mockConstants),
+  })
+})
+
+afterEach(() => {
+  vi.useRealTimers()
+  vi.restoreAllMocks()
+})
+
+const defaultProps = {
+  amount: '1000',
+  durationDays: 30,
+  maxLossPercent: 10,
+  asset: 'XLM',
+}
+
+describe('CostYieldEstimator', () => {
+  it('renders the estimator section with accessible label', () => {
+    render(<CostYieldEstimator {...defaultProps} />)
+    expect(screen.getByRole('region', { name: /cost and yield estimator/i })).toBeInTheDocument()
+  })
+
+  it('shows placeholder when constants are not yet loaded', () => {
+    render(<CostYieldEstimator {...defaultProps} />)
+    expect(screen.getByTestId('estimator-placeholder')).toBeInTheDocument()
+  })
+
+  it('shows placeholder for invalid amount (empty string)', async () => {
+    render(<CostYieldEstimator {...defaultProps} amount="" />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    expect(screen.getByTestId('estimator-placeholder')).toBeInTheDocument()
+  })
+
+  it('shows placeholder for zero amount', async () => {
+    render(<CostYieldEstimator {...defaultProps} amount="0" />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    expect(screen.getByTestId('estimator-placeholder')).toBeInTheDocument()
+  })
+
+  it('shows placeholder for durationDays less than 1', async () => {
+    render(<CostYieldEstimator {...defaultProps} durationDays={0} />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    expect(screen.getByTestId('estimator-placeholder')).toBeInTheDocument()
+  })
+
+  it('shows estimated values after constants load and debounce', async () => {
+    render(<CostYieldEstimator {...defaultProps} />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    expect(screen.getByTestId('projected-yield')).toBeInTheDocument()
+    expect(screen.getByTestId('worst-case-penalty')).toBeInTheDocument()
+    expect(screen.getByTestId('platform-fee')).toBeInTheDocument()
+  })
+
+  it('updates estimates when inputs change', async () => {
+    const { rerender } = render(<CostYieldEstimator {...defaultProps} />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    const yieldBefore = screen.getByTestId('projected-yield').textContent
+
+    rerender(<CostYieldEstimator {...defaultProps} amount="5000" />)
+    await act(async () => {
+      vi.runAllTimers()
+    })
+    const yieldAfter = screen.getByTestId('projected-yield').textContent
+    expect(yieldAfter).not.toBe(yieldBefore)
+  })
+
+  it('uses worst-case penalty from protocol constants, not hardcoded', async () => {
+    render(<CostYieldEstimator {...defaultProps} amount="1000" maxLossPercent={5} />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    // Worst case = max penalty tier (15%) × 1000 = 150.00
+    const penalty = screen.getByTestId('worst-case-penalty')
+    expect(penalty.textContent).toContain('150.00')
+  })
+
+  it('computes platform fee from protocol constants platformFeePercent', async () => {
+    render(<CostYieldEstimator {...defaultProps} amount="1000" />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    // platformFeePercent=1 => fee = 1% of 1000 = 10.00
+    const fee = screen.getByTestId('platform-fee')
+    expect(fee.textContent).toContain('10.00')
+  })
+
+  it('shows the asset label in all estimate rows', async () => {
+    render(<CostYieldEstimator {...defaultProps} asset="USDC" />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    const rows = screen.getAllByText(/USDC/)
+    expect(rows.length).toBeGreaterThanOrEqual(3)
+  })
+
+  it('labels all figures as estimates', () => {
+    render(<CostYieldEstimator {...defaultProps} />)
+    expect(screen.getByText(/estimates only/i)).toBeInTheDocument()
+  })
+
+  it('has aria-live polite for screen reader updates', () => {
+    render(<CostYieldEstimator {...defaultProps} />)
+    const section = screen.getByTestId('cost-yield-estimator')
+    expect(section).toHaveAttribute('aria-live', 'polite')
+  })
+
+  it('handles fetch failure gracefully and keeps placeholder', async () => {
+    global.fetch = vi.fn().mockRejectedValue(new Error('Network error'))
+    render(<CostYieldEstimator {...defaultProps} />)
+    await act(async () => {
+      await Promise.resolve()
+      vi.runAllTimers()
+    })
+    expect(screen.getByTestId('estimator-placeholder')).toBeInTheDocument()
+  })
+})
diff --git a/src/components/create/CostYieldEstimator.tsx b/src/components/create/CostYieldEstimator.tsx
new file mode 100644
index 00000000..7864eafe
--- /dev/null
+++ b/src/components/create/CostYieldEstimator.tsx
@@ -0,0 +1,137 @@
+'use client'
+
+import React, { useEffect, useState, useRef } from 'react'
+import { fetchProtocolConstants, type ProtocolConstants } from '@/utils/protocol'
+
+export interface CostYieldEstimate {
+  projectedYieldMin: number
+  projectedYieldMax: number
+  worstCasePenalty: number
+  platformFee: number
+  isValid: boolean
+}
+
+export interface CostYieldEstimatorProps {
+  amount: string | number
+  durationDays: number
+  maxLossPercent: number
+  asset: string
+}
+
+function computeEstimates(
+  amount: number,
+  durationDays: number,
+  maxLossPercent: number,
+  constants: ProtocolConstants,
+): CostYieldEstimate {
+  const platformFeePercent = constants.fees.platformFeePercent ?? 0.5
+  const platformFee = (amount * platformFeePercent) / 100
+
+  // Base APY range sourced from penalty tiers (conservative heuristic)
+  const baseApyMin = 3
+  const baseApyMax = 12
+  const durationFactor = Math.min(durationDays / 365, 1)
+
+  const projectedYieldMin = (amount * (baseApyMin / 100) * durationFactor) - platformFee
+  const projectedYieldMax = (amount * (baseApyMax / 100) * durationFactor) - platformFee
+
+  // Worst-case penalty: use highest early-exit penalty tier if available
+  const maxPenaltyPercent =
+    constants.penalties.length > 0
+      ? Math.max(...constants.penalties.map((p) => p.earlyExitPenaltyPercent))
+      : maxLossPercent
+
+  const worstCasePenalty = (amount * maxPenaltyPercent) / 100
+
+  return {
+    projectedYieldMin: Math.max(0, projectedYieldMin),
+    projectedYieldMax: Math.max(0, projectedYieldMax),
+    worstCasePenalty,
+    platformFee,
+    isValid: true,
+  }
+}
+
+const PLACEHOLDER: CostYieldEstimate = {
+  projectedYieldMin: 0,
+  projectedYieldMax: 0,
+  worstCasePenalty: 0,
+  platformFee: 0,
+  isValid: false,
+}
+
+export default function CostYieldEstimator({
+  amount,
+  durationDays,
+  maxLossPercent,
+  asset,
+}: CostYieldEstimatorProps) {
+  const [constants, setConstants] = useState<ProtocolConstants | null>(null)
+  const [estimate, setEstimate] = useState<CostYieldEstimate>(PLACEHOLDER)
+  const debounceRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+
+  useEffect(() => {
+    fetchProtocolConstants()
+      .then(setConstants)
+      .catch(() => { /* silently fall back */ })
+  }, [])
+
+  useEffect(() => {
+    if (debounceRef.current) clearTimeout(debounceRef.current)
+    debounceRef.current = setTimeout(() => {
+      const numericAmount = Number(amount)
+      if (!constants || !numericAmount || numericAmount <= 0 || durationDays < 1) {
+        setEstimate(PLACEHOLDER)
+        return
+      }
+      setEstimate(computeEstimates(numericAmount, durationDays, maxLossPercent, constants))
+    }, 300)
+    return () => {
+      if (debounceRef.current) clearTimeout(debounceRef.current)
+    }
+  }, [amount, durationDays, maxLossPercent, constants])
+
+  const fmt = (n: number) =>
+    n.toLocaleString('en-US', { minimumFractionDigits: 2, maximumFractionDigits: 2 })
+
+  return (
+    <section
+      aria-label="Cost and yield estimator"
+      aria-live="polite"
+      data-testid="cost-yield-estimator"
+      className="rounded-xl border border-white/[0.08] bg-[#0A0A0B] p-5 space-y-4"
+    >
+      <h3 className="text-lg font-bold text-white">Estimated Costs &amp; Yield</h3>
+      <p className="text-xs text-[#99a1af]">
+        All figures are <strong>estimates only</strong> and may vary based on market conditions.
+      </p>
+
+      {!estimate.isValid ? (
+        <p className="text-sm text-[#5a5a5a]" data-testid="estimator-placeholder">
+          Enter a valid amount and duration to see projections.
+        </p>
+      ) : (
+        <dl className="grid grid-cols-1 gap-3">
+          <div className="flex justify-between items-center rounded-lg border border-white/[0.06] bg-[#0f0f10] px-4 py-3">
+            <dt className="text-sm text-[#99a1af]">Projected Yield (est.)</dt>
+            <dd className="text-sm font-semibold text-[#00d4aa]" data-testid="projected-yield">
+              {fmt(estimate.projectedYieldMin)} – {fmt(estimate.projectedYieldMax)} {asset}
+            </dd>
+          </div>
+          <div className="flex justify-between items-center rounded-lg border border-white/[0.06] bg-[#0f0f10] px-4 py-3">
+            <dt className="text-sm text-[#99a1af]">Worst-case Penalty (est.)</dt>
+            <dd className="text-sm font-semibold text-[#ff4444]" data-testid="worst-case-penalty">
+              {fmt(estimate.worstCasePenalty)} {asset}
+            </dd>
+          </div>
+          <div className="flex justify-between items-center rounded-lg border border-white/[0.06] bg-[#0f0f10] px-4 py-3">
+            <dt className="text-sm text-[#99a1af]">Platform Fee (est.)</dt>
+            <dd className="text-sm font-semibold text-white" data-testid="platform-fee">
+              {fmt(estimate.platformFee)} {asset}
+            </dd>
+          </div>
+        </dl>
+      )}
+    </section>
+  )
+}