diff --git a/apps/simplex-calculator-bot/README.md b/apps/simplex-calculator-bot/README.md
index 72a47f87ca..9646008e04 100644
--- a/apps/simplex-calculator-bot/README.md
+++ b/apps/simplex-calculator-bot/README.md
@@ -9,7 +9,7 @@ Each user who connects via the bot's business address receives a calculator mess
 - Tap `C` to clear the number, and `C` again to clear the calculation.
 - Numbers are shown without exponent, up to 15 digits; larger results are shown as `Error`.
 - You can also send numbers and keys like `+`, `=`, `add` or `c`. Expressions like `(2 + 3) × 4` are entered as one number, and the bot replies to them with the result.
-- The bot deletes keys and numbers, tapped or sent, and sends each calculation after `=`.
+- The bot deletes keys and numbers, tapped or sent, and logs each computed operation, such as `15 + 10 = 25`.
 - After 10 minutes without input, the bot turns the calculator off and discards the calculation; tap any key to turn it on.
 - The bot sends keys like `/+` to apps with chat protocol version 21 or later, and keys like `/add` to older apps.
 
diff --git a/apps/simplex-calculator-bot/calculator.test.ts b/apps/simplex-calculator-bot/calculator.test.ts
index 54083d1f9f..e7662666c4 100644
--- a/apps/simplex-calculator-bot/calculator.test.ts
+++ b/apps/simplex-calculator-bot/calculator.test.ts
@@ -27,8 +27,8 @@ describe("keys", () => {
 
   test("compute × and ÷ before + and -", () => {
     expect(tap("2 + 2 =")).toEqual({calc: expect.objectContaining({display: "4"}), logLines: ["2 + 2 = 4"]})
-    expect(tap("2 + 3 × 4 =").logLines).toEqual(["2 + 3 × 4 = 14"])
-    expect(tap("2 × 3 + 4 =").logLines).toEqual(["2 × 3 + 4 = 10"])
+    expect(tap("2 + 3 × 4 =").logLines).toEqual(["3 × 4 = 12\n2 + 12 = 14"])
+    expect(tap("2 × 3 + 4 =").logLines).toEqual(["2 × 3 = 6", "6 + 4 = 10"])
     expect(display("1 0 - 2 × 3 =")).toBe("4")
     expect(display("1 0 - 2 - 3 =")).toBe("5")
     expect(display("8 ÷ 4 ÷ 2 =")).toBe("1")
@@ -41,15 +41,17 @@ describe("keys", () => {
     expect(display("2 + 3 × 4 +")).toBe("14")
   })
 
-  test("log only after equals", () => {
+  test("log each computed operation", () => {
+    expect(tap("1 5 + 1 0 + 5 + 1 =").logLines).toEqual(["15 + 10 = 25", "25 + 5 = 30", "30 + 1 = 31"])
+    expect(tap("2 + 3 × 4 × 5 +").logLines).toEqual(["3 × 4 = 12", "12 × 5 = 60\n2 + 60 = 62"])
     expect(tap("2 + 3 × 4").logLines).toEqual([])
     expect(tap("5 =").logLines).toEqual([])
   })
 
   test("replace operator", () => {
     expect(tap("2 + × 3 =").logLines).toEqual(["2 × 3 = 6"])
-    expect(tap("2 + 3 × + 4 =").logLines).toEqual(["2 + 3 + 4 = 9"])
-    expect(tap("2 × 3 + × 4 =").logLines).toEqual(["2 × 3 × 4 = 24"])
+    expect(tap("2 + 3 × + 4 =").logLines).toEqual(["2 + 3 = 5", "5 + 4 = 9"])
+    expect(tap("2 × 3 + × 4 =").logLines).toEqual(["2 × 3 = 6", "6 × 4 = 24"])
   })
 
   test("continue from result", () => {
@@ -68,7 +70,7 @@ describe("keys", () => {
     expect(display("5 0 ÷ 1 0 % =")).toBe("500")
     expect(display("1 5 %")).toBe("0.15")
     expect(display("1 0 0 + 2 × 1 5 %")).toBe("0.15")
-    expect(display("1 0 0 + 2 × 1 5 % =")).toBe("100.3")
+    expect(tap("1 0 0 + 2 × 1 5 % =").logLines).toEqual(["2 × 15% = 0.3\n100 + 0.3 = 100.3"])
     expect(display("2 × 3 + 1 0 %")).toBe("0.6")
   })
 
@@ -113,7 +115,7 @@ describe("typed messages", () => {
     expect(type("25", "+", "25", "=")).toEqual({calc: expect.objectContaining({display: "50"}), logLines: ["25 + 25 = 50"]})
     expect(type("25", "add", "25", "eq").logLines).toEqual(["25 + 25 = 50"])
     expect(type("6", "x", "7", "=").logLines).toEqual(["6 × 7 = 42"])
-    expect(type("5", "*", "5", "/", "2", "=").logLines).toEqual(["5 × 5 ÷ 2 = 12.5"])
+    expect(type("5", "*", "5", "/", "2", "=").logLines).toEqual(["5 × 5 = 25", "25 ÷ 2 = 12.5"])
     expect(type("25", "+", "3", "c", "4", "=").logLines).toEqual(["25 + 4 = 29"])
   })
 
diff --git a/apps/simplex-calculator-bot/calculatorBot.test.ts b/apps/simplex-calculator-bot/calculatorBot.test.ts
index c2afc83433..85a40c0550 100644
--- a/apps/simplex-calculator-bot/calculatorBot.test.ts
+++ b/apps/simplex-calculator-bot/calculatorBot.test.ts
@@ -59,7 +59,13 @@ test("calculator in business chat", async () => {
     }
     await send(["/2", "/+", "/2", "/="], receives(hasText("2 + 2 = 4")), receives(calculatorShows("4")), deletes("/+"))
     await send(["2 × (3 + 4) - 1"], receives(repliesTo("2 × (3 + 4) - 1", "13")), receives(calculatorShows("13")))
-    await send(["25", "+", "25", "="], receives(hasText("25 + 25 = 50")), receives(calculatorShows("50")), deletes("+"))
+    await send(
+      ["15", "+", "10", "+", "5", "="],
+      receives(hasText("15 + 10 = 25")),
+      receives(hasText("25 + 5 = 30")),
+      receives(calculatorShows("30")),
+      deletes("+"),
+    )
   } finally {
     await alice.close()
     await calculator.close()
diff --git a/apps/simplex-calculator-bot/src/calculator.ts b/apps/simplex-calculator-bot/src/calculator.ts
index a2b8f23763..12e33159f3 100644
--- a/apps/simplex-calculator-bot/src/calculator.ts
+++ b/apps/simplex-calculator-bot/src/calculator.ts
@@ -10,9 +10,12 @@ export interface Calc {
   mode: "typing" | "result" | "operator"
 }
 
-interface Term {
-  operand: string
+interface Operand {
+  text: string
   value: number
+}
+
+interface Term extends Operand {
   op: Operator
 }
 
@@ -59,7 +62,7 @@ export function press(calc: Calc, key: Key): [Calc, string?] {
   switch (key) {
     case "C": return [clear(calc)]
     case "=": return equals(calc)
-    case "+": case "-": case "×": case "÷": return [operator(calc, key)]
+    case "+": case "-": case "×": case "÷": return operator(calc, key)
     case "%": return [showNumber(calc, percent(calc), `${calc.operand}%`)]
     case "√": return [showNumber(calc, Math.sqrt(value(calc)), `√${calc.operand}`)]
     case "±": return [negate(calc)]
@@ -92,7 +95,7 @@ function negate(calc: Calc): Calc {
 function percent(calc: Calc): number {
   const last = calc.terms.at(-1)
   const share = value(calc) / 100
-  return last && isAdditive(last.op) ? leftOperand(calc.terms) * share : share
+  return last && isAdditive(last.op) ? last.value * share : share
 }
 
 function showNumber(calc: Calc, n: number, operand?: string): Calc {
@@ -100,35 +103,30 @@ function showNumber(calc: Calc, n: number, operand?: string): Calc {
   return {...calc, display, operand: operand ?? display, mode: "result"}
 }
 
-function operator(calc: Calc, op: Operator): Calc {
-  const terms = calc.mode === "operator"
-    ? [...calc.terms.slice(0, -1), {...calc.terms[calc.terms.length - 1], op}]
-    : [...calc.terms, {operand: calc.operand, value: value(calc), op}]
-  const display = format(leftOperand(terms))
-  return {display, operand: display, terms, mode: "operator"}
+function operator(calc: Calc, op: Operator): [Calc, string?] {
+  const terms = calc.mode === "operator" ? calc.terms.slice(0, -1) : calc.terms
+  const reduced = reduce(terms, {text: calc.operand, value: value(calc)}, precedence(op))
+  const display = format(reduced.right.value)
+  const logLine = reduced.lines.length > 0 ? reduced.lines.join("\n") : undefined
+  return [{display, operand: display, terms: [...reduced.terms, {...reduced.right, op}], mode: "operator"}, logLine]
 }
 
 function equals(calc: Calc): [Calc, string?] {
   if (calc.terms.length === 0) return [calc]
-  const display = format(evaluate(calc.terms, value(calc)).total)
-  const logLine = [...calc.terms.flatMap(term => [term.operand, term.op]), calc.operand, "=", display].join(" ")
-  return [{display, operand: display, terms: [], mode: "result"}, logLine]
+  const {right, lines} = reduce(calc.terms, {text: calc.operand, value: value(calc)}, 0)
+  return [{display: right.text, operand: right.text, terms: [], mode: "result"}, lines.join("\n")]
 }
 
-function leftOperand(terms: Term[]): number {
-  const {value, op} = terms[terms.length - 1]
-  const {total, product} = evaluate(terms.slice(0, -1), value)
-  return isAdditive(op) ? total : product
+function reduce(terms: Term[], right: Operand, minPrecedence: number): {terms: Term[], right: Operand, lines: string[]} {
+  const left = terms.at(-1)
+  if (!left || precedence(left.op) < minPrecedence) return {terms, right, lines: []}
+  const text = format(apply(left.value, left.op, right.value))
+  const reduced = reduce(terms.slice(0, -1), {text, value: Number(text)}, minPrecedence)
+  return {...reduced, lines: [`${left.text} ${left.op} ${right.text} = ${text}`, ...reduced.lines]}
 }
 
-function evaluate(terms: Term[], last: number): {total: number, product: number} {
-  const sumEnd = terms.map(term => isAdditive(term.op)).lastIndexOf(true)
-  const factors = terms.slice(sumEnd + 1)
-  const values = [...factors.map(term => term.value), last]
-  const product = factors.reduce((acc, {op}, i) => apply(acc, op, values[i + 1]), values[0])
-  if (sumEnd < 0) return {total: product, product}
-  const {value, op} = terms[sumEnd]
-  return {total: apply(evaluate(terms.slice(0, sumEnd), value).total, op, product), product}
+function precedence(op: Operator): number {
+  return isAdditive(op) ? 1 : 2
 }
 
 function isAdditive(op: Operator): boolean {