diff --git a/src/domain/adb/adbDeviceAnalysis.test.ts b/src/domain/adb/adbDeviceAnalysis.test.ts
index c67a9cc72d..8a90451d43 100644
--- a/src/domain/adb/adbDeviceAnalysis.test.ts
+++ b/src/domain/adb/adbDeviceAnalysis.test.ts
@@ -99,6 +99,12 @@ it("admits empty string extras and validates typed extra text at domain admissio
     { type: "int", value: "-2147483648" },
     { type: "long", value: "9007199254740993" },
     { type: "float", value: "-1.25" },
+    { type: "float", value: "1e-3" },
+    { type: "float", value: "1E-3" },
+    { type: "float", value: ".5" },
+    { type: "float", value: "1." },
+    { type: "float", value: "0x1.8p1" },
+    { type: "float", value: "NaN" },
   ] as const;
   for (const { type, value } of accepted)
     expect(
@@ -112,7 +118,8 @@ it("admits empty string extras and validates typed extra text at domain admissio
     { type: "boolean", value: "True" },
     { type: "int", value: "1.5" },
     { type: "long", value: "" },
-    { type: "float", value: "1e3" },
+    { type: "float", value: "garbage" },
+    { type: "float", value: "0x1.8" },
   ] as const;
   for (const { type, value } of rejected) {
     const result = adbInputSchemas.start_adb_activity.safeParse({
diff --git a/src/domain/adb/adbDeviceAnalysis.ts b/src/domain/adb/adbDeviceAnalysis.ts
index 9b068c73b6..52085a8662 100644
--- a/src/domain/adb/adbDeviceAnalysis.ts
+++ b/src/domain/adb/adbDeviceAnalysis.ts
@@ -59,6 +59,10 @@ const activityExtraStringValueSchema = z
   .max(2048)
   .regex(/^[^\x00]*$/u, "Extra values cannot contain NUL");
 const activityExtraNonEmptyValueSchema = activityExtraStringValueSchema.min(1);
+// Android's `am start --ef` parses this text with Float.valueOf. Keep the
+// caller's spelling intact while admitting Java FloatValue forms.
+const javaFloatValuePattern =
+  /^[\x01-\x20]*[+-]?(?:NaN|Infinity|(?:(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?[fFdD]?|0[xX](?:[\da-fA-F]+(?:\.[\da-fA-F]*)?|\.[\da-fA-F]+)[pP][+-]?\d+[fFdD]?))[\x01-\x20]*$/u;
 const activityExtraSchema = z.discriminatedUnion("type", [
   z.strictObject({
     key: activityExtraKeySchema,
@@ -92,8 +96,13 @@ const activityExtraSchema = z.discriminatedUnion("type", [
     key: activityExtraKeySchema,
     type: z.literal("float").describe("Float extra value type"),
     value: activityExtraNonEmptyValueSchema
-      .regex(/^-?\d+(\.\d+)?$/u, "Float extra values must be a number")
-      .describe("Float extra value as decimal text"),
+      .regex(
+        javaFloatValuePattern,
+        "Float extra value must be valid Java float text",
+      )
+      .describe(
+        "Float extra text parsed by Android am without changing its spelling",
+      ),
   }),
 ]);
 
diff --git a/tests/boundary/cli/adbCli.test.ts b/tests/boundary/cli/adbCli.test.ts
index cd76936cf9..ba41a93c49 100644
--- a/tests/boundary/cli/adbCli.test.ts
+++ b/tests/boundary/cli/adbCli.test.ts
@@ -244,7 +244,11 @@ it.each([
   ["boolean:key:yes", "invalid_request"],
   ["int:key:1.5", "invalid_request"],
   ["long:key:1.5", "invalid_request"],
-  ["float:key:1e3", "invalid_request"],
+  ["float:key:garbage", "invalid_request"],
+  ["float:key:1e-3", "capability_unavailable"],
+  ["float:key:1E-3", "capability_unavailable"],
+  ["float:key:.5", "capability_unavailable"],
+  ["float:key:1.", "capability_unavailable"],
   ["boolean:key:false", "capability_unavailable"],
   ["int:key:-3", "capability_unavailable"],
   ["long:key:9007199254740993", "capability_unavailable"],
diff --git a/tests/boundary/mcp/adbStartMcp.test.ts b/tests/boundary/mcp/adbStartMcp.test.ts
index 8c4665c66e..10670561d9 100644
--- a/tests/boundary/mcp/adbStartMcp.test.ts
+++ b/tests/boundary/mcp/adbStartMcp.test.ts
@@ -160,7 +160,7 @@ const assertAdvertisedActivityExtras = async (
     ["boolean", "yes"],
     ["int", "1.5"],
     ["long", ""],
-    ["float", "1e3"],
+    ["float", "garbage"],
   ])
     expect(
       validateInput({ ...input, extras: [{ key: "invalid", type, value }] }),
@@ -224,6 +224,7 @@ it
             extras: [
               { key: "mode", type: "string" as const, value: "test" },
               { key: "empty", type: "string" as const, value: "" },
+              { key: "scale", type: "float" as const, value: "1e-3" },
             ],
           };
     const success = await client.callTool({
@@ -312,6 +313,7 @@ it
                 "-n com.example/.Main",
                 "--es mode test",
                 "--es empty ''",
+                "--ef scale 1e-3",
               ]),
         ].join(" "),
       ),