diff --git a/README.md b/README.md
index 4a2795b..a5b0a28 100644
--- a/README.md
+++ b/README.md
@@ -34,9 +34,12 @@ them on source ports:
 | `isUsingInternalPulldown: true` | `is_using_internal_pulldown: true` | Input `pull = "Pull Down"` |
 | `activeCapability: "i2c_sda"` / `"i2c_scl"` | `is_configured_for_i2c_sda` / `is_configured_for_i2c_scl` | I2C0 SDA/SCL on physical RGE pins 3/19 |
 
-`isGpio`, `supports_*`, and `can_use_*` describe capabilities; they do not activate
-an instance. A GPIO requires exactly one input/output flag and no bidirectional
-declaration. I2C accepts open-drain and bidirectional declarations, but rejects
+`isGpio`, `isBidirectional`, `supports_*`, and `can_use_*` describe capabilities;
+they do not activate an instance. Bidirectionality can coexist with an explicit
+input/output choice; a GPIO still requires exactly one input/output flag.
+Unselected SWD and connected LF crystal pins retain their native ownership when
+bidirectional capability metadata is present. I2C accepts open-drain and
+bidirectional declarations, but rejects
 a conflicting GPIO direction. Selected electrical modes must agree with the
 native driver. Tri-state, open-collector/emitter, open-drain GPIO, SPI and UART
 are currently unsupported and fail instead of being dropped.
@@ -45,10 +48,11 @@ Output names are deterministic (`CONFIG_U1_PIN5`, `CONFIG_U1_I2C0`), and pins ar
 sorted by physical identity. No behavior is inferred from signal or net names.
 Unconnected capability-only ports remain unallocated. Connected physical GPIO
 pins without a supported function are reported together, even if all their
-attributes (including `is_gpio`) are missing. Errors identify the MCU name/part number and physical pin labels (for example,
-`U1 pin 4 (DIO11)`), without generated record IDs. They explain which existing
-TSX attributes to set and distinguish datasheet capabilities from the board
-function that must be selected.
+attributes (including `is_gpio`) are missing. Missing-direction errors contain
+one short line per pin with the component name, physical pin number, label and
+problem, for example `- U1 pin 4 (DIO11): GPIO direction is missing`.
+These diagnostics omit manufacturer part numbers, generated record IDs and TSX
+setup instructions.
 An MCU with no source ports, or a trace referencing a missing source-port record,
 fails before any output is available. An incomplete I2C selection reports the
 selected endpoints and asks for both SDA and SCL declarations. Passives and other
diff --git a/lib/cc2340/derive-requests.ts b/lib/cc2340/derive-requests.ts
index 71a560e..ecbf984 100644
--- a/lib/cc2340/derive-requests.ts
+++ b/lib/cc2340/derive-requests.ts
@@ -68,10 +68,7 @@ export function deriveCc2340Requests(
       )
     const isSda = port.is_configured_for_i2c_sda === true
     const isScl = port.is_configured_for_i2c_scl === true
-    const selectedGpio =
-      port.is_input === true ||
-      port.is_output === true ||
-      port.is_bidirectional === true
+    const selectedGpio = port.is_input === true || port.is_output === true
     const selectedElectricalMode = selectedElectricalModes.some(
       (attribute) => port[attribute] === true,
     )
@@ -149,12 +146,11 @@ export function deriveCc2340Requests(
     }
     if (!connected && !selectedGpio && !selectedElectricalMode) continue
     if (
-      port.is_bidirectional ||
       port.is_input === port.is_output ||
       (!port.is_input && !port.is_output)
     ) {
       missing.push(
-        `${identity}: ${port.is_bidirectional ? "bidirectional GPIO is unsupported" : port.is_input && port.is_output ? "both isInput and isOutput are selected" : "no GPIO direction or supported peripheral selected"}`,
+        `${identity}: ${port.is_input && port.is_output ? "both isInput and isOutput are selected" : "GPIO direction is missing"}`,
       )
       continue
     }
@@ -174,9 +170,7 @@ export function deriveCc2340Requests(
     resolved.gpios.push({ request, pin: physical.pin })
   }
   if (missing.length)
-    throw new Error(
-      `Unresolved CC2340 pin configuration for ${componentIdentity}:\n${missing.map((problem) => `- ${problem}`).join("\n")}\nUpdate ${component.name}'s TSX pinAttributes with the intended function for each listed pin: set exactly one of isInput: true or isOutput: true for GPIO, or activeCapability: "i2c_sda" / "i2c_scl" for I2C.\nDatasheet capabilities such as isGpio describe what a pin supports; they do not select how this board uses it.`,
-    )
+    throw new Error(missing.map((problem) => `- ${problem}`).join("\n"))
   if (sdaPorts.length || sclPorts.length) {
     const sda = sdaPorts[0]
     const scl = sclPorts[0]
diff --git a/lib/cc2340/resolve-port.ts b/lib/cc2340/resolve-port.ts
index 3f7bcfd..2ff724b 100644
--- a/lib/cc2340/resolve-port.ts
+++ b/lib/cc2340/resolve-port.ts
@@ -105,7 +105,7 @@ export function checkCc2340Function(
   // TI's I2CLPF3 driver configures both pins with GPIO_CFG_OUT_OD_PU.
   // Open drain is compatible with I2C, but not our standard GPIO output mode.
   if (role === "gpio") {
-    forbidden.push("is_using_open_drain", "is_bidirectional")
+    forbidden.push("is_using_open_drain")
     if (typeof request !== "string")
       forbidden.push(request.direction === "input" ? "is_output" : "is_input")
   } else {
diff --git a/tests/cc2340-conversion.test.ts b/tests/cc2340-conversion.test.ts
index b53c57f..30ddbe3 100644
--- a/tests/cc2340-conversion.test.ts
+++ b/tests/cc2340-conversion.test.ts
@@ -70,6 +70,20 @@ test("actual board emits three GPIOs and the exact I2C identifiers", () => {
   )
 })
 
+test("explicit requests preserve GPIO and I2C settings with bidirectional capabilities", () => {
+  const enriched = circuit.map((element) =>
+    element.type === "source_port" &&
+    element.source_component_id === pedometerOptions.source_component_id
+      ? { ...element, is_bidirectional: true }
+      : element,
+  )
+  const before = structuredClone(enriched)
+  expect(
+    convertCircuitJsonToSysConfig(enriched, pedometerOptions).getString(),
+  ).toBe(output().getString())
+  expect(enriched).toEqual(before)
+})
+
 test("100000 bits/s becomes numeric 100 kbit/s through serialization and re-parsing", async () => {
   const options = structuredClone(pedometerOptions)
   expect(options.i2c?.max_bit_rate).toBe(100000)
diff --git a/tests/derived-cc2340-lf-crystal.test.ts b/tests/derived-cc2340-lf-crystal.test.ts
index e12095e..c089af5 100644
--- a/tests/derived-cc2340-lf-crystal.test.ts
+++ b/tests/derived-cc2340-lf-crystal.test.ts
@@ -97,6 +97,16 @@ test("direct traces and swapped interchangeable crystal terminals resolve the sa
   )
 })
 
+test("bidirectional capabilities do not claim connected LF crystal pins", () => {
+  const circuitJson = crystalCircuit()
+  const baseline = convertCircuitJsonToSysConfig(circuitJson).getString()
+  for (const pin_number of [4, 14, 15])
+    mcuPort(circuitJson, pin_number).is_bidirectional = true
+  const before = structuredClone(circuitJson)
+  expect(convertCircuitJsonToSysConfig(circuitJson).getString()).toBe(baseline)
+  expect(circuitJson).toEqual(before)
+})
+
 test("missing crystal terminals and incomplete wiring remain unresolved", () => {
   for (const source_trace_id of [
     "crystal_p_trace",
@@ -202,7 +212,6 @@ test("multiple connected crystals are ambiguous", () => {
 for (const declarations of [
   { is_output: true },
   { is_input: true },
-  { is_bidirectional: true },
   { is_configured_for_i2c_sda: true },
   { is_using_internal_pullup: true },
   { is_using_open_drain: true },
diff --git a/tests/derived-cc2340.test.ts b/tests/derived-cc2340.test.ts
index 9ff58be..89ccbbb 100644
--- a/tests/derived-cc2340.test.ts
+++ b/tests/derived-cc2340.test.ts
@@ -131,13 +131,12 @@ test("an MCU with no pin records gets an actionable component error", () => {
 })
 
 test("pins with no attributes report every connected physical pin", () => {
-  expect(() =>
-    convertCircuitJsonToSysConfig(
-      connected([{ pin_number: 5 }, { pin_number: 6 }]),
-    ),
-  ).toThrow(
-    /U1 \(CC2340R52E0RGER\)[\s\S]*U1 pin 5 \(signal_0\)[\s\S]*U1 pin 6 \(signal_1\)[\s\S]*isInput: true or isOutput: true/,
-  )
+  expect(
+    conversionError(connected([{ pin_number: 5 }, { pin_number: 6 }])),
+  ).toMatchInlineSnapshot(`
+    "- U1 pin 5 (signal_0): GPIO direction is missing
+    - U1 pin 6 (signal_1): GPIO direction is missing"
+  `)
 })
 
 test("one configured pin cannot hide another pin's missing attributes", () => {
@@ -215,6 +214,7 @@ test("unused capabilities do not activate GPIO or I2C", () => {
       {
         pin_number: 6,
         is_gpio: true,
+        is_bidirectional: true,
         supports_i2c_sda: true,
         can_use_open_drain: true,
       },
@@ -227,8 +227,7 @@ test("unused capabilities do not activate GPIO or I2C", () => {
 
 for (const flags of [
   { is_input: true, is_output: true },
-  { is_bidirectional: true },
-  { is_output: true, is_bidirectional: true },
+  { is_input: true, is_output: true, is_bidirectional: true },
   { is_output: true, is_using_open_drain: true },
   { is_output: true, is_using_tri_state: true },
   { is_output: true, is_using_open_collector: true },
@@ -278,6 +277,39 @@ test("unpaired, duplicate, conflicting and unsupported I2C routes fail", () => {
     expect(() => convertCircuitJsonToSysConfig(circuit(ports))).toThrow()
 })
 
+test("bidirectional capabilities preserve selected GPIO directions and SWD ownership", () => {
+  const input = connected([
+    { pin_number: 4, name: "DIO11", is_output: true },
+    { pin_number: 5, name: "DIO12", is_input: true },
+    { pin_number: 7, name: "DIO16_SWDIO", is_gpio: true },
+    { pin_number: 8, name: "DIO17_SWDCK", is_gpio: true },
+  ])
+  const baseline = convertCircuitJsonToSysConfig(input).getString()
+  const enriched = input.map((element) =>
+    element.type === "source_port"
+      ? { ...element, is_bidirectional: true }
+      : element,
+  )
+  const before = structuredClone(enriched)
+  expect(convertCircuitJsonToSysConfig(enriched).getString()).toBe(baseline)
+  expect(enriched).toEqual(before)
+})
+
+test("a connected bidirectional capability still requires a board direction", () => {
+  const input = connected([
+    { pin_number: 4, name: "DIO11", is_output: true },
+    { pin_number: 5, name: "DIO12", is_bidirectional: true, is_gpio: true },
+  ])
+  expect(conversionError(input)).toMatchInlineSnapshot(
+    `"- U1 pin 5 (DIO12): GPIO direction is missing"`,
+  )
+  const converter = new CircuitJsonToSysConfigConverter(input)
+  converter.step()
+  expect(() => converter.step()).toThrow(/U1 pin 5/)
+  expect(converter.finished).toBe(false)
+  expect(() => converter.getOutput()).toThrow("must finish")
+})
+
 test("SDK debug ownership and LF crystal conflicts are explicit", () => {
   const debug = convertCircuitJsonToSysConfig(
     connected([
@@ -368,7 +400,7 @@ test("three stages snapshot inputs, stay deterministic and expose no partial out
 
 test("the unmodified pedometer cannot acquire firmware choices from its name", () => {
   expect(() => convertCircuitJsonToSysConfig(pedometer)).toThrow(
-    /Unresolved CC2340 pin configuration/,
+    /GPIO direction is missing/,
   )
 })
 
@@ -446,11 +478,8 @@ test("pin errors use circuit labels and stay unchanged when generated IDs change
   const message = conversionError(input)
   expect(conversionError(renamed)).toBe(message)
   expect(message).toMatchInlineSnapshot(`
-    "Unresolved CC2340 pin configuration for U1 (CC2340R52E0RGER):
-    - U1 pin 4 (DIO11): no GPIO direction or supported peripheral selected
-    - U1 pin 6 (DIO13): no GPIO direction or supported peripheral selected
-    Update U1's TSX pinAttributes with the intended function for each listed pin: set exactly one of isInput: true or isOutput: true for GPIO, or activeCapability: "i2c_sda" / "i2c_scl" for I2C.
-    Datasheet capabilities such as isGpio describe what a pin supports; they do not select how this board uses it."
+    "- U1 pin 4 (DIO11): GPIO direction is missing
+    - U1 pin 6 (DIO13): GPIO direction is missing"
   `)
   expect(message).not.toMatch(
     /source_component_123|source_trace_456|mcu|port_0|port_1/,
diff --git a/tests/fixtures/derived-cc2340/README.md b/tests/fixtures/derived-cc2340/README.md
index 3bc39e3..e4b187a 100644
--- a/tests/fixtures/derived-cc2340/README.md
+++ b/tests/fixtures/derived-cc2340/README.md
@@ -5,6 +5,9 @@ firmware application preset. It declares output pin 5, input pin 6 with an
 internal pull-up, and I2C SDA/SCL pins 3/19 using the existing pin attributes.
 Physical identities use the converter's independently validated RGE target.
 No startup level, interrupt, bitrate, LF clock or RTOS choice is declared.
+The MCU ports also carry bidirectional capability flags, as published for
+CC2340R52E0RGER. These coexist with the selected GPIO/I2C functions and do not
+select a function themselves.
 
 `bun run validate:cc2340` converts it without request options, runs TI SysConfig
 1.28.1+4785 against official SimpleLink F3 SDK tag `lpf3-9.21.00.36_LTS`, and
diff --git a/tests/fixtures/derived-cc2340/circuit.json b/tests/fixtures/derived-cc2340/circuit.json
index 60bf050..8144973 100644
--- a/tests/fixtures/derived-cc2340/circuit.json
+++ b/tests/fixtures/derived-cc2340/circuit.json
@@ -13,7 +13,8 @@
     "name": "SDA",
     "pin_number": 3,
     "is_configured_for_i2c_sda": true,
-    "is_using_open_drain": true
+    "is_using_open_drain": true,
+    "is_bidirectional": true
   },
   {
     "type": "source_port",
@@ -23,7 +24,8 @@
     "pin_number": 5,
     "is_gpio": true,
     "is_output": true,
-    "is_using_push_pull": true
+    "is_using_push_pull": true,
+    "is_bidirectional": true
   },
   {
     "type": "source_port",
@@ -33,7 +35,8 @@
     "pin_number": 6,
     "is_gpio": true,
     "is_input": true,
-    "is_using_internal_pullup": true
+    "is_using_internal_pullup": true,
+    "is_bidirectional": true
   },
   {
     "type": "source_port",
@@ -42,6 +45,7 @@
     "name": "SCL",
     "pin_number": 19,
     "is_configured_for_i2c_scl": true,
-    "is_using_open_drain": true
+    "is_using_open_drain": true,
+    "is_bidirectional": true
   }
 ]
diff --git a/tests/fixtures/derived-cc2340/lf-crystal.circuit.json b/tests/fixtures/derived-cc2340/lf-crystal.circuit.json
index 0e2dce9..b8210d3 100644
--- a/tests/fixtures/derived-cc2340/lf-crystal.circuit.json
+++ b/tests/fixtures/derived-cc2340/lf-crystal.circuit.json
@@ -12,7 +12,8 @@
     "source_component_id": "mcu",
     "name": "DIO11",
     "pin_number": 4,
-    "is_output": true
+    "is_output": true,
+    "is_bidirectional": true
   },
   {
     "type": "source_port",
@@ -20,7 +21,8 @@
     "source_component_id": "mcu",
     "name": "DIO3_X32P",
     "pin_number": 14,
-    "is_gpio": true
+    "is_gpio": true,
+    "is_bidirectional": true
   },
   {
     "type": "source_port",
@@ -28,7 +30,8 @@
     "source_component_id": "mcu",
     "name": "DIO4_X32N",
     "pin_number": 15,
-    "is_gpio": true
+    "is_gpio": true,
+    "is_bidirectional": true
   },
   {
     "type": "source_component",