diff --git a/packages/opencode/test/provider/harmoniqs-no-tools.test.ts b/packages/opencode/test/provider/harmoniqs-no-tools.test.ts
index b3b25aeec..2227ef6e5 100644
--- a/packages/opencode/test/provider/harmoniqs-no-tools.test.ts
+++ b/packages/opencode/test/provider/harmoniqs-no-tools.test.ts
@@ -99,25 +99,33 @@ describe("LLMRequestPrep.prepare - harmoniqs idempotency", () => {
     }
   }
 
+  // The per-provider header union carries the static shape only — harmoniqs
+  // injects Idempotency-Key at runtime (#374) — so tests index through a
+  // widened record rather than the narrowed type.
+  async function prepareHeaders(model: any) {
+    const result = await Effect.runPromise(LLMRequestPrep.prepare(baseInput(model)))
+    return result.headers as Record<string, string | undefined>
+  }
+
   test("sends Idempotency-Key header for harmoniqs provider", async () => {
-    const result = await Effect.runPromise(LLMRequestPrep.prepare(baseInput(harmoniqsModel)))
-    expect(result.headers["Idempotency-Key"]).toBeDefined()
-    expect(result.headers["Idempotency-Key"]).toMatch(/^amicode:/)
+    const headers = await prepareHeaders(harmoniqsModel)
+    expect(headers["Idempotency-Key"]).toBeDefined()
+    expect(headers["Idempotency-Key"]).toMatch(/^amicode:/)
   })
 
   test("sends X-Session-Id header for harmoniqs provider", async () => {
-    const result = await Effect.runPromise(LLMRequestPrep.prepare(baseInput(harmoniqsModel)))
-    expect(result.headers["X-Session-Id"]).toBe(sessionID)
+    const headers = await prepareHeaders(harmoniqsModel)
+    expect(headers["X-Session-Id"]).toBe(sessionID)
   })
 
   test("does not send Idempotency-Key for non-harmoniqs providers", async () => {
-    const result = await Effect.runPromise(LLMRequestPrep.prepare(baseInput(anthropicModel)))
-    expect(result.headers["Idempotency-Key"]).toBeUndefined()
+    const headers = await prepareHeaders(anthropicModel)
+    expect(headers["Idempotency-Key"]).toBeUndefined()
   })
 
   test("generates unique Idempotency-Key per request", async () => {
-    const a = await Effect.runPromise(LLMRequestPrep.prepare(baseInput(harmoniqsModel)))
-    const b = await Effect.runPromise(LLMRequestPrep.prepare(baseInput(harmoniqsModel)))
-    expect(a.headers["Idempotency-Key"]).not.toBe(b.headers["Idempotency-Key"])
+    const a = await prepareHeaders(harmoniqsModel)
+    const b = await prepareHeaders(harmoniqsModel)
+    expect(a["Idempotency-Key"]).not.toBe(b["Idempotency-Key"])
   })
 })
diff --git a/packages/ui/src/context/marked-math.test.ts b/packages/ui/src/context/marked-math.test.ts
index 05338bcb2..313cd6e2b 100644
--- a/packages/ui/src/context/marked-math.test.ts
+++ b/packages/ui/src/context/marked-math.test.ts
@@ -17,6 +17,25 @@ test("renders tight and loose-inner single-$ math", async () => {
   expect(await parse("set $\\delta/2\\pi = 0.1$ MHz")).toContain('class="katex"')
 })
 
+test("renders digit-led single-$ inline math", async () => {
+  // #375 — the open-side digit guard rejected any math starting with a digit,
+  // which is the standard physics reporting shape ($3.53\times10^{-5}$)
+  expect(await parse("nice determinism check ($3.53\\times10^{-5}$ — free)")).toContain('class="katex"')
+  expect(await parse("floor through the mock seam ($3.1\\times10^{-3}$, T1-dominated)")).toContain(
+    'class="katex"',
+  )
+  expect(await parse("infidelity $10^{-5}$ at best")).toContain('class="katex"')
+  expect(await parse("$0.99$-style fidelity")).toContain('class="katex"')
+})
+
+test("keeps tight digit-pair currency literal under the close-side guard", async () => {
+  // Pandoc rule: the closing $ must not be followed by a digit — the first $
+  // in "$30-and-$50" closes against "3", so the pair stays literal
+  const html = await parse("prices: $30-and-$50 pairs")
+  expect(html).not.toContain('class="katex"')
+  expect(html).toContain("$30-and-$50")
+})
+
 test("keeps currency and env-var dollars literal", async () => {
   const prices = await parse("costs $5 and $10 total")
   expect(prices).not.toContain('class="katex"')
@@ -66,6 +85,10 @@ test("renderMathInText renders single-$ inline and spares prose dollars", () =>
   expect(prices).toContain("$5")
   expect(prices).toContain("$10")
 
+  // #375 — digit-led math through the global replace, tight pairs still literal
+  expect(renderMathInText("check ($3.53\\times10^{-5}$ — free)")).toContain('class="katex"')
+  expect(renderMathInText("prices: $30-and-$50 pairs")).not.toContain('class="katex"')
+
   expect(renderMathInText("$$\n\\hat H\n$$")).toContain("katex-display")
   expect(renderMathInText("inline \\(\\Omega_x\\) math")).toContain('class="katex"')
 })
diff --git a/packages/ui/src/context/marked.tsx b/packages/ui/src/context/marked.tsx
index e4a00db7d..47fda7846 100644
--- a/packages/ui/src/context/marked.tsx
+++ b/packages/ui/src/context/marked.tsx
@@ -420,12 +420,15 @@ registerCustomTheme("OpenCode", () => Promise.resolve(OpenCodeTheme))
 
 // Single-$ inline math — restored after #34850 removed it for currency false
 // positives. Pandoc-style tight delimiters (no whitespace just inside either
-// $), no digit-led content (so $5, and $30-and-$50 pairs, stay literal), no
-// $$ adjacency, no escaped \$. One regex family, three shapes: the tokenizer
-// start hint, the anchored tokenizer match, and the global replace below.
+// $): the opening $ drops the digit-led guard so $3.53\times10^{-5}$ renders;
+// instead the closing $ must not be followed by a digit (Pandoc's actual
+// currency rule — $30-and-$50 pairs stay literal because the first closing $
+// abuts a digit). No $$ adjacency, no escaped \$. One regex family, three
+// shapes: the tokenizer start hint, the anchored tokenizer match, and the
+// global replace below.
 const singleDollarStartRegex = /(?<![\\$])\$(?!\$)/
-const singleDollarTokenizerRegex = /^\$(?!\$|\s|\d)((?:\\.|[^$\\\n])+?)(?<![\\\s])\$(?!\$)/
-const singleDollarInlineRegex = /(?<![\\$])\$(?!\$|\s|\d)((?:\\.|[^$\\\n])+?)(?<![\\\s])\$(?!\$)/g
+const singleDollarTokenizerRegex = /^\$(?!\$|\s)((?:\\.|[^$\\\n])+?)(?<![\\\s])\$(?!\$|\d)/
+const singleDollarInlineRegex = /(?<![\\$])\$(?!\$|\s)((?:\\.|[^$\\\n])+?)(?<![\\\s])\$(?!\$|\d)/g
 
 export function renderMathInText(text: string): string {
   let result = text