diff --git a/packages/adapter-utils/src/command-redaction.test.ts b/packages/adapter-utils/src/command-redaction.test.ts
index 1f80f44eb2..b58d37aad8 100644
--- a/packages/adapter-utils/src/command-redaction.test.ts
+++ b/packages/adapter-utils/src/command-redaction.test.ts
@@ -306,6 +306,42 @@ describe("redactCommandText header secrets", () => {
     );
   });
 
+  it("consumes a suffix segment adjacent to a serialized quoted header argument", () => {
+    // The suffix is part of the same shell word as the header, so it is part
+    // of the credential at every serialization depth.
+    let text = 'curl -H "X-API-Key: SECRET"TAILMARK;echo safe';
+    for (let depth = 1; depth <= 3; depth += 1) {
+      text = JSON.stringify(text);
+      const output = redactCommandText(text);
+      expect(output).not.toContain("SECRET");
+      expect(output).not.toContain("TAILMARK");
+      expect(output).toContain(";echo safe");
+      expect(() => JSON.parse(output)).not.toThrow();
+      expect(redactCommandText(output)).toBe(output);
+    }
+  });
+
+  it("keeps a serializer's closing delimiter when the argument is truncated", () => {
+    // A run log can cut a serialized command inside the header argument. The
+    // truncated value stops before the enclosing string's own quote, even
+    // when the cut lands after a backslash, so the string stays well formed.
+    const cuts = [
+      'curl -H "X-API-Key: SECRET',
+      'curl -H X-API-Key:"SECRET',
+      'curl -H "X-API-Key: SECRET\\',
+      'curl -H "X-API-Key: SECRET\\\\',
+      'curl -H X-API-Key:"SECRET\\',
+    ];
+    for (const cut of cuts) {
+      for (const text of [JSON.stringify(cut), JSON.stringify(JSON.stringify(cut))]) {
+        const output = redactCommandText(text);
+        expect(output).not.toContain("SECRET");
+        expect(() => JSON.parse(output)).not.toThrow();
+        expect(redactCommandText(output)).toBe(output);
+      }
+    }
+  });
+
   it("redacts a bare apikey header value", () => {
     // Supabase sends the key under an unhyphenated `apikey` header.
     expect(redactCommandText("apikey: abc")).toBe(
diff --git a/packages/adapter-utils/src/command-redaction.ts b/packages/adapter-utils/src/command-redaction.ts
index abf7ab022e..0223179264 100644
--- a/packages/adapter-utils/src/command-redaction.ts
+++ b/packages/adapter-utils/src/command-redaction.ts
@@ -185,16 +185,27 @@ const commandSecretHeaderEscapedOpener = (run: string) =>
   String.raw`(?<!\\)(?<${run}>(?:\\\\)*\\)"`;
 const commandSecretHeaderEscapedBody = (run: string) =>
   String.raw`(?:(?!(?<!\\)\k<${run}>")[^\s\r\n])(?:(?!(?<!\\)\k<${run}>")[^\r\n])*`;
-const commandSecretHeaderEscapedCloser = (run: string, close: string) =>
-  String.raw`(?:(?<${close}>\k<${run}>")|(?=[\r\n]|$))`;
+// A truncated argument has no closer on its line. Its body then also stops
+// before a bare quote, one preceded by an even run of backslashes, which can
+// only be an enclosing serializer's delimiter; that delimiter survives and the
+// enclosing string stays well formed. The closer itself is unescaped, so
+// backtracking never reads an escaped backslash as the closer.
+const COMMAND_SECRET_HEADER_BARE_QUOTE_PATTERN = String.raw`(?<=(?<!\\)(?:\\\\)*)"`;
+const commandSecretHeaderEscapedTruncatedBody = (run: string) =>
+  String.raw`(?:(?!(?<!\\)\k<${run}>")(?!${COMMAND_SECRET_HEADER_BARE_QUOTE_PATTERN})[^\s\r\n])` +
+  String.raw`(?:(?!(?<!\\)\k<${run}>")(?!${COMMAND_SECRET_HEADER_BARE_QUOTE_PATTERN})[^\r\n])*`;
+const commandSecretHeaderEscapedValue = (run: string, close: string) =>
+  `(?:${commandSecretHeaderEscapedBody(run)}(?<!\\\\)(?<${close}>\\k<${run}>")` +
+  `|${commandSecretHeaderEscapedTruncatedBody(run)}` +
+  String.raw`(?=[\r\n]|$|${COMMAND_SECRET_HEADER_BARE_QUOTE_PATTERN}))`;
 const COMMAND_SECRET_HEADER_RE = new RegExp(
   String.raw`(?<!\\)(?<dqPrefix>"${COMMAND_SECRET_HEADER_PREFIX_PATTERN})(?:\\.|[^\s"\\])(?:\\\r?\n|\\.|[^"\\\r\n])*\\?(?:(?<dqClose>")|(?=[\r\n]|$))${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}` +
     String.raw`|(?<sqPrefix>'${COMMAND_SECRET_HEADER_PREFIX_PATTERN})[^\s'][^'\r\n]*(?:(?<sqClose>')|(?=[\r\n]|$))${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}` +
     String.raw`|(?<ansiPrefix>\$'${COMMAND_SECRET_HEADER_PREFIX_PATTERN})(?:\\.|[^\s'\\])(?:\\.|[^'\\\r\n])*\\?(?:(?<ansiClose>')|(?=[\r\n]|$))${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}` +
     `|(?<serPrefix>${commandSecretHeaderEscapedOpener("serRun")}${COMMAND_SECRET_HEADER_PREFIX_PATTERN})` +
-    `${commandSecretHeaderEscapedBody("serRun")}${commandSecretHeaderEscapedCloser("serRun", "serClose")}` +
+    `${commandSecretHeaderEscapedValue("serRun", "serClose")}${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}` +
     String.raw`|(?<![A-Za-z0-9_-])(?<evPrefix>\b${COMMAND_SECRET_HEADER_NAME_PATTERN}${COMMAND_SECRET_HEADER_COLON_PATTERN}${COMMAND_SECRET_HEADER_SCHEME_PATTERN}${commandSecretHeaderEscapedOpener("evRun")}${COMMAND_SECRET_HEADER_SCHEME_PATTERN})` +
-    `${commandSecretHeaderEscapedBody("evRun")}${commandSecretHeaderEscapedCloser("evRun", "evClose")}${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}` +
+    `${commandSecretHeaderEscapedValue("evRun", "evClose")}${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}` +
     String.raw`|(?<![A-Za-z0-9_-])(?<!(?<!\\)["'])(?<uqPrefix>\b${COMMAND_SECRET_HEADER_PREFIX_PATTERN})${COMMAND_SECRET_HEADER_UNQUOTED_VALUE_PATTERN}${COMMAND_SECRET_HEADER_CONTINUATION_PATTERN}`,
   "gi",
 );