diff --git a/packages/adapter-utils/src/command-redaction.test.ts b/packages/adapter-utils/src/command-redaction.test.ts
index 7be371ff22..2293c6eaf4 100644
--- a/packages/adapter-utils/src/command-redaction.test.ts
+++ b/packages/adapter-utils/src/command-redaction.test.ts
@@ -321,10 +321,11 @@ describe("redactCommandText header secrets", () => {
     }
   });
 
-  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.
+  it("redacts a truncated serialized argument to the end of its line", () => {
+    // A run log can cut a serialized command inside the header argument. With
+    // no closer on the line, the value runs to the end of the line: a bare
+    // quote there may be a further segment of the same shell word, so the rule
+    // redacts it rather than keeping it as the enclosing string's delimiter.
     const cuts = [
       'curl -H "X-API-Key: SECRET',
       'curl -H X-API-Key:"SECRET',
@@ -336,12 +337,32 @@ describe("redactCommandText header secrets", () => {
       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("keeps an even backslash run before a quote out of the escape pair", () => {
+    // Two backslashes are an escaped backslash; the quote after them opens a
+    // further segment of the same word, which is consumed with the value.
+    const input = 'curl -H X-API-Key:SECRET\\\\"TAILMARK"MORE ;echo safe';
+    const output = redactCommandText(input);
+    expect(output).not.toContain("SECRET");
+    expect(output).not.toContain("TAILMARK");
+    expect(output).not.toContain("MORE");
+    expect(output).toBe(`curl -H X-API-Key:${REDACTED_COMMAND_TEXT_VALUE} ;echo safe`);
+    expect(redactCommandText(output)).toBe(output);
+  });
+
+  it("redacts a truncated quoted tail after an escaped-quoted value", () => {
+    const input = 'curl -H X-API-Key:\\"SECRET"TAILMARK';
+    const output = redactCommandText(input);
+    expect(output).not.toContain("SECRET");
+    expect(output).not.toContain("TAILMARK");
+    expect(output).toBe(`curl -H X-API-Key:\\"${REDACTED_COMMAND_TEXT_VALUE}`);
+    expect(redactCommandText(output)).toBe(output);
+  });
+
   it("consumes an escaped-space continuation at every serialization depth", () => {
     // A shell escape pair doubles its backslash with each serialization
     // layer; the continuation reads the whole run as one pair.
diff --git a/packages/adapter-utils/src/command-redaction.ts b/packages/adapter-utils/src/command-redaction.ts
index 3a534525e0..9d4d6f6c54 100644
--- a/packages/adapter-utils/src/command-redaction.ts
+++ b/packages/adapter-utils/src/command-redaction.ts
@@ -135,13 +135,13 @@ const COMMAND_SHELL_QUOTED_SEGMENT_PATTERNS = [
   String.raw`'[^'\r\n]*'`,
   String.raw`\$'(?:\\.|[^'\\\r\n])*'`,
 ] as const;
-const COMMAND_SHELL_ESCAPE_PAIR_PATTERN = String.raw`\\+[^\r\n]`;
+const COMMAND_SHELL_ESCAPE_PAIR_PATTERN = String.raw`(?:(?:\\\\)+[^"\r\n]|(?:\\\\)*\\[^\r\n])`;
 // An opening escape pair carries the first byte of an unquoted value, as in
 // `X-API-Key:\ abc`. The backslash run may be longer inside a serialized
 // command, where each layer doubles it. A run followed by a quote is excluded,
 // so a `\"` opener at any depth falls to the escaped branches, which precede
 // the unquoted one in the alternation.
-const COMMAND_SHELL_OPENING_ESCAPE_PAIR_PATTERN = String.raw`\\+[^"\r\n]`;
+const COMMAND_SHELL_OPENING_ESCAPE_PAIR_PATTERN = String.raw`(?:(?:\\\\)+[^"\r\n]|(?:\\\\)*\\[^"\r\n])`;
 // The first segment of an unquoted value is a raw token, bounded only by
 // whitespace, a quote, a backtick, or a backslash. A raw HTTP diagnostic
 // carries an opaque credential the same way, so a `;`, `|`, or `&` inside it
@@ -185,19 +185,14 @@ const commandSecretHeaderEscapedOpener = (run: string) =>
   String.raw`(?<!\\)(?<${run}>(?:\\\\)*\\)"`;
 const commandSecretHeaderEscapedBody = (run: string) =>
   String.raw`(?:(?!(?<!\\)\k<${run}>")[^\s\r\n])(?:(?!(?<!\\)\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}>")(?!${COMMAND_SECRET_HEADER_BARE_QUOTE_PATTERN})[^\r\n])*`;
+// The closer itself is unescaped, so backtracking never reads an escaped
+// backslash as the closer. A truncated argument has no closer on its line and
+// the value then runs to the end of the line: a bare quote there may be a
+// further segment of the same shell word, so it is redacted rather than kept.
 const commandSecretHeaderEscapedValue = (run: string, close: string) =>
   `(?:${commandSecretHeaderEscapedBody(run)}(?<!\\\\)(?<${close}>\\k<${run}>")` +
-  `|${commandSecretHeaderEscapedTruncatedBody(run)}` +
-  String.raw`(?=[\r\n]|$|${COMMAND_SECRET_HEADER_BARE_QUOTE_PATTERN}))`;
+  `|${commandSecretHeaderEscapedBody(run)}` +
+  String.raw`(?=[\r\n]|$))`;
 const COMMAND_SECRET_HEADER_RE = new RegExp(
   String.raw`(?<!\\)(?<dqPrefix>"${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}` +