diff --git a/Dockerfile.test b/Dockerfile.test
index faf73ba45..374d0a666 100644
--- a/Dockerfile.test
+++ b/Dockerfile.test
@@ -110,4 +110,14 @@ RUN cd packages/producer && bunx tsx scripts/generate-font-data.ts
 
 WORKDIR /app/packages/producer
 
-ENTRYPOINT ["bunx", "tsx", "src/regression-harness.ts", "--", "--sequential"]
+# Skip fixtures tagged `transparency` (Chrome alpha-channel PSNR quirks not
+# reproducible on the CI image) and `field-signal-reproducer` (known-broken
+# fixture per PR #2512 — codifies a real bug awaiting a fix). Mirrors the
+# `--exclude-tags` in the local `test:regression*` scripts in
+# packages/producer/package.json so `bun run docker:test*` and the aws-lambda
+# smoke tests skip the same set. Docker CMD args from `docker run <image> ...`
+# are appended after these flags, so positional test names (e.g. shard args
+# `hdr-regression style-5-prod ...` in .github/workflows/regression.yml) still
+# resolve normally; the harness applies excludeTags whether testNames is empty
+# or non-empty (see discoverTestSuites in src/regression-harness.ts).
+ENTRYPOINT ["bunx", "tsx", "src/regression-harness.ts", "--", "--sequential", "--exclude-tags", "transparency,field-signal-reproducer"]
diff --git a/packages/producer/src/regression-harness-parse.test.ts b/packages/producer/src/regression-harness-parse.test.ts
new file mode 100644
index 000000000..ae7ba3933
--- /dev/null
+++ b/packages/producer/src/regression-harness-parse.test.ts
@@ -0,0 +1,54 @@
+// Pure-function tests for `parseArgs()` in the regression harness. Pins the
+// `--exclude-tags` comma-parsing contract that the values baked into
+// `Dockerfile.test` and `packages/producer/package.json` test scripts depend
+// on. When someone changes the parser (e.g. to space-separated or repeated
+// flags) these tests + the invocation strings in the Dockerfile / package.json
+// must move together.
+
+import { describe, expect, it } from "bun:test";
+import { parseArgs } from "./regression-harness.js";
+
+// parseArgs reads from index 2 onwards (node + script name are argv[0..1]).
+const withProgram = (rest: string[]): string[] => ["node", "regression-harness.ts", ...rest];
+
+describe("parseArgs() — --exclude-tags", () => {
+  it("splits a single --exclude-tags argument on commas", () => {
+    const opts = parseArgs(withProgram(["--exclude-tags", "transparency,field-signal-reproducer"]));
+    expect(opts.excludeTags).toEqual(["transparency", "field-signal-reproducer"]);
+  });
+
+  it("accepts a single tag with no comma", () => {
+    const opts = parseArgs(withProgram(["--exclude-tags", "transparency"]));
+    expect(opts.excludeTags).toEqual(["transparency"]);
+  });
+
+  it("supports repeated --exclude-tags flags (accumulating)", () => {
+    const opts = parseArgs(
+      withProgram(["--exclude-tags", "transparency", "--exclude-tags", "field-signal-reproducer"]),
+    );
+    expect(opts.excludeTags).toEqual(["transparency", "field-signal-reproducer"]);
+  });
+
+  it("matches the values baked into Dockerfile.test ENTRYPOINT and package.json scripts", () => {
+    // Pins the exact string the Dockerfile.test ENTRYPOINT + package.json
+    // `test:regression*` scripts pass. If either invocation site changes to
+    // whitespace-separated or another delimiter, this test fails and forces
+    // an audit of the parser at the same time.
+    const opts = parseArgs(
+      withProgram([
+        "--sequential",
+        "--exclude-tags",
+        "transparency,field-signal-reproducer",
+        "hdr-regression",
+      ]),
+    );
+    expect(opts.sequential).toBe(true);
+    expect(opts.excludeTags).toEqual(["transparency", "field-signal-reproducer"]);
+    expect(opts.testNames).toEqual(["hdr-regression"]);
+  });
+
+  it("defaults excludeTags to an empty array when the flag is absent", () => {
+    const opts = parseArgs(withProgram([]));
+    expect(opts.excludeTags).toEqual([]);
+  });
+});
diff --git a/packages/producer/src/regression-harness.ts b/packages/producer/src/regression-harness.ts
index d1c6dde2e..15e056819 100644
--- a/packages/producer/src/regression-harness.ts
+++ b/packages/producer/src/regression-harness.ts
@@ -241,7 +241,10 @@ function formatResidualSuffix(residualRmsDb: number | null, error: string | unde
   return `, residualRMS: ${residualRmsDb.toFixed(2)} dBFS`;
 }
 
-function parseArgs(argv: string[]): CliOptions {
+// Exported for unit testing (pinning `--exclude-tags` comma-parsing so the
+// values baked into `Dockerfile.test` and `packages/producer/package.json`
+// scripts keep matching the parser's contract).
+export function parseArgs(argv: string[]): CliOptions {
   const testNames: string[] = [];
   const excludeTags: string[] = [];
   let update = false;