fix(environment): scan every form occurrence and MIME-less scenario bodies

The build's credential scan collapsed form bodies with Object.fromEntries, so a
repeated field kept only its last occurrence: `api_key=secret&api_key=` warned
about nothing although the Evidence ships the value, and repeated values were
undercounted. Form fields are now scanned as ordered name/value pairs, as
headers and query strings already are.

The review projection of a capture_browser_scenario dropped a request body
recorded without a media type, so the scan never saw it. Review keeps such a
body's text with an empty media type; the manifest projection still reads only
bodies it can classify.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/specs/agent-environments/environment-build/spec.md

@@ -47,7 +47,9 @@ before building.
   pointers, never values, and never refuse a build; the scan cannot overflow the
   stack on deeply nested bodies. A browser scenario's retained header values and
   the query parameters of its recorded URLs are scanned as a HAR's headers and
-  query strings are.
+  query strings are, and so are its request bodies recorded without a media
+  type. Each occurrence of a repeated form field counts, as each repeated
+  header or query parameter does.
 - Nothing is written before the bundle stage; `--dry-run` writes nothing,
   reports the files a build would write and refuses the package tarballs a build
   refuses, admitting and releasing the tarball as a build does: a close it

src/application/environment/environmentBuildReport.test.ts

@@ -1,5 +1,7 @@
 import { describe, expect, it } from "vitest";
 
+import { scenarioCaptureFixture } from "../../../tests/fixtures/browserScenarioCapture.js";
+import { scenarioCaptureRecords } from "../../domain/analysisView/scenarioCaptureRecords.js";
 import type { WebNetworkCaptureRecord } from "../../domain/webNetworkCapture.js";
 import {
   anonymousOrigin,
@@ -130,6 +132,47 @@ describe("scanCredentialNames", () => {
     });
   });
 
+  it("counts every occurrence of a repeated form field that holds a value", () => {
+    const form = (text: string): WebNetworkCaptureRecord => {
+      const scanned = record(3, undefined, undefined);
+      (
+        scanned.reported as { request: { postData?: unknown } }
+      ).request.postData = {
+        mimeType: "application/x-www-form-urlencoded",
+        text,
+      };
+      return scanned;
+    };
+    // A later empty occurrence does not hide the earlier value the Evidence ships.
+    expect(scanCredentialNames([form("api_key=secret&api_key=")])).toEqual({
+      count: 1,
+      pointers: ["record 3 request /api_key"],
+    });
+    expect(scanCredentialNames([form("token=a&page=1&token=b")])).toEqual({
+      count: 2,
+      pointers: ["record 3 request /token", "record 3 request /token"],
+    });
+  });
+
+  it("scans a scenario request body the capture recorded without a media type", () => {
+    const capture = scenarioCaptureFixture(
+      [
+        {
+          method: "POST",
+          url: "/api/session",
+          status: 200,
+          mediaType: "application/json",
+          body: "{}",
+          requestBody: '{"password":"x"}',
+        },
+      ],
+      { request_body: true, response_body: true, header_values: true },
+    );
+    expect(
+      scanCredentialNames(scenarioCaptureRecords(capture, "review").records),
+    ).toEqual({ count: 1, pointers: ["record 0 request /password"] });
+  });
+
   it("walks bodies nested deeper than the call stack allows", () => {
     const depth = 20_000;
     const deep = record(1, undefined, undefined);

src/application/environment/environmentBuildReport.ts

@@ -84,21 +84,26 @@ const member = (value: unknown, name: string): unknown =>
     ? Reflect.get(value, name)
     : undefined;
 
-/** A recorded body as JSON or form members, or undefined when it is neither. */
-const parsedBody = (text: unknown): unknown => {
+/** A recorded body: a JSON value to walk, or form fields in order with every occurrence kept, as headers and query strings are. */
+type ScannedBody =
+  | { readonly kind: "json"; readonly value: unknown }
+  | { readonly kind: "form"; readonly fields: readonly [string, string][] };
+
+/** A recorded body as JSON or form fields, or undefined when it is neither. */
+const parsedBody = (text: unknown): ScannedBody | undefined => {
   if (typeof text !== "string" || text.length > SCAN_BODY_LIMIT_BYTES)
     return undefined;
   const start = text.trimStart()[0];
   if (start === "{" || start === "[") {
     try {
-      return JSON.parse(text);
+      return { kind: "json", value: JSON.parse(text) };
     } catch {
       return undefined;
     }
   }
   if (!/^[^=&\s]+=[^&]*(?:&[^=&\s]+=[^&]*)*$/u.test(text)) return undefined;
   try {
-    return Object.fromEntries(new URLSearchParams(text));
+    return { kind: "form", fields: [...new URLSearchParams(text)] };
   } catch {
     return undefined;
   }
@@ -149,6 +154,13 @@ export const scanCredentialNames = (
       }
     }
   };
+  const scanBody = (body: ScannedBody | undefined, label: string): void => {
+    if (body?.kind === "json") walk(body.value, label);
+    else if (body?.kind === "form")
+      for (const [name, value] of body.fields)
+        if (credentialNamed(name) && holdsValue(value))
+          found(`${label} /${pointerToken(name)}`);
+  };
   for (const record of records) {
     const ordinal = String(record.ordinal);
     const request = member(record.reported, "request");
@@ -163,11 +175,11 @@ export const scanCredentialNames = (
     for (const [name, value] of namedValues(member(request, "queryString")))
       if (credentialNamed(name) && holdsValue(value))
         found(`record ${ordinal} request query ${name}`);
-    walk(
+    scanBody(
       parsedBody(member(member(request, "postData"), "text")),
       `record ${ordinal} request`,
     );
-    walk(
+    scanBody(
       parsedBody(
         readRecordedResponseBody(record, SCAN_BODY_LIMIT_BYTES).bodyText,
       ),

src/domain/analysisView/scenarioCaptureRecords.test.ts

@@ -293,3 +293,29 @@ it("keeps retained header values and URL query pairs only for review", () => {
     expect(projected?.reported).not.toHaveProperty("response.headers");
   }
 });
+
+it("keeps a request body without a media type for review only", () => {
+  const capture = scenarioCaptureFixture(
+    [
+      {
+        method: "POST",
+        url: "/api/session",
+        status: 200,
+        mediaType: "application/json",
+        body: "{}",
+        requestBody: '{"password":"x"}',
+      },
+    ],
+    { request_body: true, response_body: true, header_values: true },
+  );
+  // A body the capture could not classify is still shipped Evidence, so review sees its text.
+  expect(
+    scenarioCaptureRecords(capture, "review").records[0]?.reported,
+  ).toMatchObject({
+    request: { postData: { mimeType: "", text: '{"password":"x"}' } },
+  });
+  // The manifest still reads only bodies whose media type it can classify.
+  expect(
+    scenarioCaptureRecords(capture, "manifest").records[0]?.reported,
+  ).not.toHaveProperty("request.postData");
+});

src/domain/analysisView/scenarioCaptureRecords.ts

@@ -125,9 +125,10 @@ const reportedRequest = (
           queryString: queryPairs(request.url.url),
         }
       : {}),
-    ...(text === undefined || mimeType === undefined
+    // Review scans every retained body, so one the capture could not classify keeps its text with an empty media type.
+    ...(text === undefined || (mimeType === undefined && purpose !== "review")
       ? {}
-      : { postData: { mimeType, text } }),
+      : { postData: { mimeType: mimeType ?? "", text } }),
   };
 };