diff --git a/libs/logging/src/main/kotlin/com/getcode/utils/LiveSecrets.kt b/libs/logging/src/main/kotlin/com/getcode/utils/LiveSecrets.kt
new file mode 100644
index 0000000000..cf76ff6e5a
--- /dev/null
+++ b/libs/logging/src/main/kotlin/com/getcode/utils/LiveSecrets.kt
@@ -0,0 +1,31 @@
+package com.getcode.utils
+
+import java.util.concurrent.ConcurrentHashMap
+
+/**
+ * Values that must not reach a log in full while they can still be used, such as a payment
+ * request's `payment_intent_id`: anyone who learns it before the share is paid can use it up
+ * and block the payment. Once the payment succeeds the value is harmless and is [release]d so
+ * logs can show it in full again.
+ *
+ * Values are base58 strings, the form the log formatters render ids in.
+ */
+object LiveSecrets {
+    private val held = ConcurrentHashMap.newKeySet<String>()
+
+    fun hold(value: String) {
+        held += value
+    }
+
+    fun release(value: String) {
+        held -= value
+    }
+
+    fun isLive(value: String): Boolean = value in held
+
+    /** [value] masked if it is held, otherwise unchanged. */
+    fun redact(value: String): String = if (isLive(value)) value.maskedSuffix() else value
+}
+
+/** Only the last [visibleLength] characters, after an ellipsis: `…3kQx9Z`. */
+fun String.maskedSuffix(visibleLength: Int = 6): String = "…${takeLast(visibleLength)}"
diff --git a/libs/logging/src/test/kotlin/com/getcode/utils/LiveSecretsTest.kt b/libs/logging/src/test/kotlin/com/getcode/utils/LiveSecretsTest.kt
new file mode 100644
index 0000000000..6d842013a2
--- /dev/null
+++ b/libs/logging/src/test/kotlin/com/getcode/utils/LiveSecretsTest.kt
@@ -0,0 +1,34 @@
+package com.getcode.utils
+
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class LiveSecretsTest {
+
+    private val id = "4vJ9JU1bJJE96FWSJKvHsmmFADCg4gpZQff4P3bkLKi"
+
+    @After
+    fun tearDown() {
+        LiveSecrets.release(id)
+    }
+
+    @Test
+    fun `maskedSuffix keeps only the last six characters`() {
+        assertEquals("…3bkLKi", id.maskedSuffix())
+    }
+
+    @Test
+    fun `redact masks a held value and passes others through`() {
+        LiveSecrets.hold(id)
+        assertEquals("…3bkLKi", LiveSecrets.redact(id))
+        assertEquals("other", LiveSecrets.redact("other"))
+    }
+
+    @Test
+    fun `redact shows a released value in full`() {
+        LiveSecrets.hold(id)
+        LiveSecrets.release(id)
+        assertEquals(id, LiveSecrets.redact(id))
+    }
+}
diff --git a/services/opencode/build.gradle.kts b/services/opencode/build.gradle.kts
index e3129cb094..538849797b 100644
--- a/services/opencode/build.gradle.kts
+++ b/services/opencode/build.gradle.kts
@@ -94,4 +94,6 @@ dependencies {
     testImplementation(kotlin("test"))
     testImplementation(libs.bundles.unit.testing)
     testImplementation(testFixtures(project(":libs:currency-math")))
+    // formatProto tests render a flipcash2 response that carries a payment_intent_id.
+    testImplementation(libs.flipcash2.client.protocol)
 }
diff --git a/services/opencode/src/main/kotlin/com/getcode/opencode/internal/network/executors/IntentExecutor.kt b/services/opencode/src/main/kotlin/com/getcode/opencode/internal/network/executors/IntentExecutor.kt
index 6d9f07fbb6..ca61a3569d 100644
--- a/services/opencode/src/main/kotlin/com/getcode/opencode/internal/network/executors/IntentExecutor.kt
+++ b/services/opencode/src/main/kotlin/com/getcode/opencode/internal/network/executors/IntentExecutor.kt
@@ -15,7 +15,9 @@ import com.getcode.opencode.solana.intents.ServerParameter
 import com.getcode.services.opencode.BuildConfig
 import com.getcode.solana.keys.base58
 import com.getcode.solana.keys.redact
+import com.getcode.utils.LiveSecrets
 import com.getcode.utils.TraceType
+import com.getcode.utils.maskedSuffix
 import com.getcode.utils.trace
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
@@ -101,9 +103,10 @@ class IntentExecutor(
     ): Result<IntentType> = openBidirectionalStreamForResult(
         streamRef = streamRef,
         apiCall = { request ->
+            val id = intent.id.base58()
             trace(
                 tag = "SubmitIntent",
-                message = "submitting intent ${intent.id.base58().redact()}"
+                message = "submitting intent ${if (LiveSecrets.isLive(id)) id.maskedSuffix() else id.redact()}"
             )
             api.submitIntent(request)
         },
diff --git a/services/opencode/src/main/kotlin/com/getcode/opencode/utils/logging/LoggingClientCallListener.kt b/services/opencode/src/main/kotlin/com/getcode/opencode/utils/logging/LoggingClientCallListener.kt
index 7edb1afadd..e1b6289283 100644
--- a/services/opencode/src/main/kotlin/com/getcode/opencode/utils/logging/LoggingClientCallListener.kt
+++ b/services/opencode/src/main/kotlin/com/getcode/opencode/utils/logging/LoggingClientCallListener.kt
@@ -1,7 +1,10 @@
 package com.getcode.opencode.utils.logging
 
+import androidx.annotation.VisibleForTesting
+import com.getcode.utils.LiveSecrets
 import com.getcode.utils.TraceManager
 import com.getcode.utils.TraceType
+import com.getcode.utils.maskedSuffix
 import com.getcode.utils.trace
 import com.getcode.vendor.Base58
 import com.google.protobuf.ByteString
@@ -70,13 +73,23 @@ private val BASE58_WRAPPER_NAMES = setOf(
     "Hash", "Blockhash", "IntentId", "SwapId",
 )
 
+/**
+ * Fields whose value can be used by anyone who reads it until the payment it belongs to
+ * succeeds, so they are only ever logged as their last six base58 characters.
+ */
+private val SENSITIVE_FIELD_NAMES = setOf(
+    "paymentIntentId_",
+)
+
 /**
  * Formats a gRPC message (expected to be a protobuf [MessageLite]) into a
  * human-readable single-line string.  Known byte-wrapper types are rendered
- * as base58; UUIDs are rendered in standard 8-4-4-4-12 form; all other
- * messages have their fields printed recursively.
+ * as base58, masked while [LiveSecrets] holds them; UUIDs are rendered in
+ * standard 8-4-4-4-12 form; all other messages have their fields printed
+ * recursively, with [SENSITIVE_FIELD_NAMES] masked.
  */
-private fun formatProto(obj: Any?): String {
+@VisibleForTesting
+internal fun formatProto(obj: Any?): String {
     if (obj == null) return "null"
     if (obj !is MessageLite) return obj.toString()
 
@@ -86,7 +99,7 @@ private fun formatProto(obj: Any?): String {
         // Byte-wrapper → base58
         if (name in BASE58_WRAPPER_NAMES) {
             val bytes = obj.getByteField("value_") ?: return name
-            return Base58.encode(bytes)
+            return LiveSecrets.redact(Base58.encode(bytes))
         }
 
         // UUID wrapper → standard format
@@ -115,7 +128,11 @@ private fun formatProto(obj: Any?): String {
             field.isAccessible = true
             val value = field.get(obj) ?: continue
 
-            val formatted = formatFieldValue(fieldName, value)
+            val formatted = if (fieldName in SENSITIVE_FIELD_NAMES) {
+                formatSensitive(value)
+            } else {
+                formatFieldValue(fieldName, value)
+            }
             if (formatted != null) {
                 // Strip the trailing underscore that protobuf-lite adds.
                 val displayName = fieldName.trimEnd('_')
@@ -160,6 +177,17 @@ private fun formatFieldValue(fieldName: String, value: Any): String? = when (val
     else -> value.toString().masked()
 }
 
+/** A sensitive field's value as its masked base58 suffix, or `null` when unset. */
+private fun formatSensitive(value: Any): String? {
+    val bytes = when (value) {
+        is ByteString -> value.toByteArray()
+        is MessageLite -> value.getByteField("value_") ?: value.toByteArray()
+        else -> return "…"
+    }
+    if (bytes.isEmpty()) return null
+    return Base58.encode(bytes).maskedSuffix()
+}
+
 /** Read a [ByteString] instance field by name via reflection. */
 private fun MessageLite.getByteField(name: String): ByteArray? {
     return try {
diff --git a/services/opencode/src/test/kotlin/com/getcode/opencode/utils/logging/FormatProtoTest.kt b/services/opencode/src/test/kotlin/com/getcode/opencode/utils/logging/FormatProtoTest.kt
new file mode 100644
index 0000000000..e0665a409f
--- /dev/null
+++ b/services/opencode/src/test/kotlin/com/getcode/opencode/utils/logging/FormatProtoTest.kt
@@ -0,0 +1,56 @@
+package com.getcode.opencode.utils.logging
+
+import com.codeinc.flipcash.gen.common.v1.Common
+import com.codeinc.flipcash.gen.paymentrequest.v1.PaymentrequestService.GetPaymentRequestResponse
+import com.codeinc.opencode.gen.common.v1.Model
+import com.getcode.utils.LiveSecrets
+import com.getcode.vendor.Base58
+import com.google.protobuf.ByteString
+import kotlin.test.AfterTest
+import kotlin.test.Test
+import kotlin.test.assertContains
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+
+class FormatProtoTest {
+
+    private val idBytes = ByteArray(32) { (it + 1).toByte() }
+    private val idBase58 = Base58.encode(idBytes)
+
+    @AfterTest
+    fun tearDown() {
+        LiveSecrets.release(idBase58)
+    }
+
+    @Test
+    fun `payment_intent_id in a GetPaymentRequest response is logged as its last six characters`() {
+        val response = GetPaymentRequestResponse.newBuilder()
+            .setResult(GetPaymentRequestResponse.Result.DENIED)
+            .setPaymentIntentId(Common.IntentId.newBuilder().setValue(ByteString.copyFrom(idBytes)))
+            .build()
+
+        val line = formatProto(response)
+
+        assertContains(line, "paymentIntentId=…${idBase58.takeLast(6)}")
+        assertFalse(idBase58 in line, "full id leaked: $line")
+        // The rest of the body is still logged (OK is the zero value, which the formatter skips).
+        assertContains(line, "result=")
+    }
+
+    @Test
+    fun `an intent id held in LiveSecrets is logged as its last six characters`() {
+        val intentId = Model.IntentId.newBuilder().setValue(ByteString.copyFrom(idBytes)).build()
+        LiveSecrets.hold(idBase58)
+
+        assertEquals("…${idBase58.takeLast(6)}", formatProto(intentId))
+    }
+
+    @Test
+    fun `an intent id is logged in full once released`() {
+        val intentId = Model.IntentId.newBuilder().setValue(ByteString.copyFrom(idBytes)).build()
+        LiveSecrets.hold(idBase58)
+        LiveSecrets.release(idBase58)
+
+        assertEquals(idBase58, formatProto(intentId))
+    }
+}