diff --git a/docs/release.md b/docs/release.md
index 7f0f67d..8c61dba 100644
--- a/docs/release.md
+++ b/docs/release.md
@@ -51,7 +51,7 @@ Two things worth knowing:
 ## Versioning
 
 What couples the CLI to a payload is the manifest's `schemaVersion` (currently
-`3`), not the package version. A CLI accepts a set of versions — `{2, 3}` today —
+`4`), not the package version. A CLI accepts a set of versions — `{2, 3, 4}` today —
 exported at the `./manifest` subpath as `SUPPORTED_SCHEMA_VERSION` (the current
 one) plus `SUPPORTED_SCHEMA_VERSIONS` (the accepted set). Adding a version is a
 minor when older ones keep parsing, **a major once one is dropped**; either way
@@ -70,22 +70,8 @@ anything that moves that envelope, the exit codes, or `schemaVersion`.
 
 Generated notes only cover commit subjects, so add these by hand.
 
-- **The default config location moved** to `streamctl.config.ts` in the repo
-  root. `init` writes it there.
-- **`.streamctl/config.*` keeps working, permanently.** Not deprecated, no
-  warning, no removal planned. Existing repos need to do nothing.
-- **One break:** `.config/.streamctl/config.ts` used to resolve through c12's
-  `.config/` convention and now raises `NOT_INITIALIZED`. Fix:
-
-  ```sh
-  git mv .config/.streamctl/config.ts streamctl.config.ts
-  ```
-
-  Nothing else under `.config/` was ever read. Realistically nobody is affected:
-  the layout is undocumented, and it only ever worked on trees resolving
-  c12 >= 3.2.0.
-- **New warning:** two extensions at one location (`streamctl.config.js` beside
-  `streamctl.config.ts`) now warn on stderr which one is being read, since c12
-  orders `.js` ahead of `.ts`. Nothing is read differently than before, so a repo
-  that sees it needs no migration.
-- Minor bump: new default, no removals.
+- **Manifest schemaVersion 4.** With placeholder `omitLineIfEmpty: true`, a line
+  holding only the token is removed when the value is `""` instead of left blank.
+- v2 and v3 payloads parse unchanged. Using the key needs `schemaVersion: 4` and
+  this CLI or newer.
+- Minor bump: new schema version, no removals.
diff --git a/src/engine/manifest.ts b/src/engine/manifest.ts
index 7e45898..b2502dc 100644
--- a/src/engine/manifest.ts
+++ b/src/engine/manifest.ts
@@ -3,7 +3,7 @@ import type { ManagedFile as EngineManagedFile } from "../config/types";
 import type { ConfigKeyType, ManagedFile as ManifestManagedFile, PayloadManifest, PresetManifest, RenderDef } from "../manifest/schema";
 import type { PayloadHandle } from "../payload/resolve";
 import { StreamctlError } from "../errors";
-import { FROM_DEPENDENCY_MIN_SCHEMA_VERSION, payloadManifestSchema, presetManifestSchema, SUPPORTED_SCHEMA_VERSION_LIST, SUPPORTED_SCHEMA_VERSIONS, zodToIssues } from "../manifest/schema";
+import { FROM_DEPENDENCY_MIN_SCHEMA_VERSION, OMIT_LINE_MIN_SCHEMA_VERSION, payloadManifestSchema, presetManifestSchema, SUPPORTED_SCHEMA_VERSION_LIST, SUPPORTED_SCHEMA_VERSIONS, zodToIssues } from "../manifest/schema";
 
 const PAYLOAD_MANIFEST = "presets/manifest.json";
 
@@ -102,17 +102,24 @@ export async function loadPresetManifest(payload: PayloadHandle, name: string, m
     }
   }
 
-  // Feature gate. zod strictness only stops `fromDependency` on an OLD CLI; without this
-  // check a payload author who forgets the schemaVersion bump ships a payload this CLI
-  // accepts and every older one rejects with a raw zod wall.
-  if (manifest.schemaVersion < FROM_DEPENDENCY_MIN_SCHEMA_VERSION) {
+  // Feature gates. zod strictness only stops a new key on an OLD CLI; without this check a
+  // payload author who forgets the schemaVersion bump ships a payload this CLI accepts and
+  // every older one rejects with a raw zod wall.
+  const gates = [
+    { feature: "fromDependency", required: FROM_DEPENDENCY_MIN_SCHEMA_VERSION },
+    { feature: "omitLineIfEmpty", required: OMIT_LINE_MIN_SCHEMA_VERSION },
+  ] as const;
+  for (const { feature, required } of gates) {
+    if (manifest.schemaVersion >= required) {
+      continue;
+    }
     for (const [render, def] of Object.entries(preset.renders ?? {})) {
       for (const [key, placeholder] of Object.entries(def.placeholders ?? {})) {
-        if (placeholder.fromDependency !== undefined) {
+        if (placeholder[feature] !== undefined) {
           throw new StreamctlError(
             "CONFIG_INVALID",
-            `${file} renders.${render} placeholder "${key}" uses fromDependency, which requires schemaVersion ${FROM_DEPENDENCY_MIN_SCHEMA_VERSION}, but ${PAYLOAD_MANIFEST} declares schemaVersion ${manifest.schemaVersion}.`,
-            { file, preset: name, render, placeholder: key, found: manifest.schemaVersion, required: FROM_DEPENDENCY_MIN_SCHEMA_VERSION },
+            `${file} renders.${render} placeholder "${key}" uses ${feature}, which requires schemaVersion ${required}, but ${PAYLOAD_MANIFEST} declares schemaVersion ${manifest.schemaVersion}.`,
+            { file, preset: name, render, placeholder: key, found: manifest.schemaVersion, required },
           );
         }
       }
diff --git a/src/engine/render.ts b/src/engine/render.ts
index 7f08465..0dc72e5 100644
--- a/src/engine/render.ts
+++ b/src/engine/render.ts
@@ -145,6 +145,17 @@ function unresolvedTokens(text: string, values: ReadonlyMap<string, string>, pas
   return names.sort().map(name => `\${${name}}`);
 }
 
+/** Removes every line holding at least one of `tokens` and nothing else but spaces, tabs and a CR. */
+function dropTokenLines(text: string, tokens: readonly string[]): string {
+  return text
+    .split("\n")
+    .filter((line) => {
+      const rest = tokens.reduce((acc, token) => acc.replaceAll(token, ""), line);
+      return rest === line || /[^ \t\r]/.test(rest);
+    })
+    .join("\n");
+}
+
 /**
  * Assemble fragments in declared order (`toggle` includes when true, `forEach`
  * repeats per `string[]` item as `${ITEM}`), then substitute `${KEY}` placeholders
@@ -195,6 +206,7 @@ export function renderFile(
   // Values are resolved (and pattern-checked) once, ahead of substitution: they come from
   // the config and the dependency map, never from the output being assembled.
   const values = new Map<string, string>();
+  const omitTokens: string[] = [];
   for (const [key, def] of Object.entries(renderDef.placeholders ?? {})) {
     const value = resolvePlaceholder(def, config, key, filePath, deps);
     if (def.pattern !== undefined && !new RegExp(def.pattern).test(value)) {
@@ -204,6 +216,10 @@ export function renderFile(
         { file: filePath, placeholder: key, value },
       );
     }
+    if (def.omitLineIfEmpty === true && value === "") {
+      omitTokens.push(`\${${key}}`);
+      continue;
+    }
     values.set(key, value);
   }
 
@@ -235,6 +251,9 @@ export function renderFile(
     }
   }
 
+  // Last, so "alone on its line" is judged on the rendered text.
+  output = omitTokens.reduce((acc, token) => acc.replaceAll(token, ""), dropTokenLines(output, omitTokens));
+
   for (const match of output.matchAll(LEFTOVER_TOKEN_RE)) {
     const token = match[0];
     const name = match[1] ?? "";
diff --git a/src/manifest/schema.ts b/src/manifest/schema.ts
index 61c192c..7cd9b3c 100644
--- a/src/manifest/schema.ts
+++ b/src/manifest/schema.ts
@@ -18,13 +18,14 @@ const LEGACY_CONFIG_DIR = ".streamctl";
  * name because base-config's `scripts/validate-presets.mjs` imports it from
  * `@sidebase/streamctl/manifest`. Manifest and package versions are otherwise independent.
  */
-export const SUPPORTED_SCHEMA_VERSION = 3;
+export const SUPPORTED_SCHEMA_VERSION = 4;
 
 /**
  * Every version this CLI accepts; anything else maps to `SCHEMA_UNSUPPORTED`. v2 payloads
- * keep working unchanged, v3 additionally allows placeholder `fromDependency`.
+ * keep working unchanged, v3 additionally allows placeholder `fromDependency`, v4
+ * placeholder `omitLineIfEmpty`.
  */
-export const SUPPORTED_SCHEMA_VERSIONS: ReadonlySet<number> = new Set([2, SUPPORTED_SCHEMA_VERSION]);
+export const SUPPORTED_SCHEMA_VERSIONS: ReadonlySet<number> = new Set([2, 3, SUPPORTED_SCHEMA_VERSION]);
 
 /** Sorted rendering of {@link SUPPORTED_SCHEMA_VERSIONS} for error messages. */
 export const SUPPORTED_SCHEMA_VERSION_LIST = [...SUPPORTED_SCHEMA_VERSIONS].sort((a, b) => a - b).join(", ");
@@ -32,6 +33,9 @@ export const SUPPORTED_SCHEMA_VERSION_LIST = [...SUPPORTED_SCHEMA_VERSIONS].sort
 /** Lowest `schemaVersion` a payload may declare while using placeholder `fromDependency`. */
 export const FROM_DEPENDENCY_MIN_SCHEMA_VERSION = 3;
 
+/** Lowest `schemaVersion` a payload may declare while using placeholder `omitLineIfEmpty`. */
+export const OMIT_LINE_MIN_SCHEMA_VERSION = 4;
+
 /** The CLI checks shape only; semantics stay payload-owned. `"object"` is a presence + `typeof` check with no deep validation. */
 export const CONFIG_KEY_TYPES = ["boolean", "string", "string[]", "object"] as const;
 export type ConfigKeyType = (typeof CONFIG_KEY_TYPES)[number];
@@ -44,6 +48,10 @@ export type ConfigKeyType = (typeof CONFIG_KEY_TYPES)[number];
  * `fromDependency` names an npm package whose pin in the consumer's package.json supplies
  * the value (stripped to its range floor) when `configPath` yields nothing. Requires payload
  * `schemaVersion` {@link FROM_DEPENDENCY_MIN_SCHEMA_VERSION}, enforced in `loadPresetManifest`.
+ *
+ * `omitLineIfEmpty`: when the value is `""`, a line holding only such tokens (plus
+ * spaces/tabs) after all other placeholders are substituted is removed; any other occurrence
+ * becomes `""`. Requires `schemaVersion` {@link OMIT_LINE_MIN_SCHEMA_VERSION}.
  */
 export const placeholderSchema = z.strictObject({
   configPath: z.string().min(1),
@@ -51,6 +59,7 @@ export const placeholderSchema = z.strictObject({
   default: z.string(),
   pattern: z.string().min(1).optional(),
   join: z.enum(["space", "lines"]).optional(),
+  omitLineIfEmpty: z.boolean().optional(),
 });
 
 /**
diff --git a/test/manifest-loader.test.ts b/test/manifest-loader.test.ts
index 91c5a5e..4b5d060 100644
--- a/test/manifest-loader.test.ts
+++ b/test/manifest-loader.test.ts
@@ -89,17 +89,17 @@ describe("schemaVersion contract", () => {
 
   // Checked ahead of zod so the user sees both version numbers instead of a refinement issue.
   it("names the payload's version and ours when they disagree", async () => {
-    const payload = payloadOf({ "manifest.json": { schemaVersion: 4, presets: ["base"], profiles: [], defaultBase: "base" } });
+    const payload = payloadOf({ "manifest.json": { schemaVersion: 5, presets: ["base"], profiles: [], defaultBase: "base" } });
     const error = await caught(loadPayloadManifest(payload));
     expect(error.code).toBe("SCHEMA_UNSUPPORTED");
-    expect(error.message).toContain("schemaVersion 4");
-    expect(error.message).toContain("schemaVersion 2, 3");
+    expect(error.message).toContain("schemaVersion 5");
+    expect(error.message).toContain("schemaVersion 2, 3, 4");
     expect(error.message).toContain("Upgrade the CLI or the payload");
-    expect(error.details).toMatchObject({ found: 4, supported: [2, 3] });
+    expect(error.details).toMatchObject({ found: 5, supported: [2, 3, 4] });
   });
 
   it("surfaces through resolvePresetChain too", async () => {
-    const payload = payloadOf({ "manifest.json": { schemaVersion: 4, presets: ["base"], profiles: [], defaultBase: "base" } });
+    const payload = payloadOf({ "manifest.json": { schemaVersion: 5, presets: ["base"], profiles: [], defaultBase: "base" } });
     const error = await caught(resolvePresetChain(payload, "base", "nuxt-4"));
     expect(error.code).toBe("SCHEMA_UNSUPPORTED");
   });
@@ -149,6 +149,32 @@ describe("fromDependency feature gate", () => {
   });
 });
 
+describe("omitLineIfEmpty feature gate", () => {
+  function withOmitLine(schemaVersion: number): PayloadHandle {
+    return payloadOf({
+      "manifest.json": { schemaVersion, presets: ["base"], profiles: [], defaultBase: "base" },
+      "base/preset.json": {
+        name: "base",
+        files: [{ path: "Dockerfile", strategy: "full", source: "Dockerfile", render: "dockerfile" }],
+        renders: { dockerfile: { placeholders: { HOOK: { configPath: "docker.hook", default: "", omitLineIfEmpty: true } } } },
+        configKeys: { "docker.hook": "string" },
+      },
+    });
+  }
+
+  it("lets a v4 payload declare it", async () => {
+    const { files } = await resolvePresetChain(withOmitLine(4), "base", "nuxt-4");
+    expect(files.find(f => f.path === "Dockerfile")?.renderDef?.placeholders?.HOOK?.omitLineIfEmpty).toBe(true);
+  });
+
+  it("refuses it under a v3 payload, naming the placeholder and the version it needs", async () => {
+    const error = await caught(resolvePresetChain(withOmitLine(3), "base", "nuxt-4"));
+    expect(error.code).toBe("CONFIG_INVALID");
+    expect(error.message).toContain("\"HOOK\" uses omitLineIfEmpty, which requires schemaVersion 4");
+    expect(error.details).toMatchObject({ file: "presets/base/preset.json", render: "dockerfile", placeholder: "HOOK", found: 3, required: 4 });
+  });
+});
+
 describe("resolvePresetChain (v2 payload)", () => {
   it("walks the extends chain parents-first and merges the baseline", async () => {
     const { files, baseline } = await resolvePresetChain(validPayload(), "nuxt-app", "nuxt-4");
diff --git a/test/manifest-schema.test.ts b/test/manifest-schema.test.ts
index 9bada7c..1d7d766 100644
--- a/test/manifest-schema.test.ts
+++ b/test/manifest-schema.test.ts
@@ -292,14 +292,14 @@ describe("PayloadManifest schemaVersion contract", () => {
   // The exported constant is base-config's `validate-presets.mjs` contract: it writes this
   // value into new payloads, so it has to be the current one, not just a supported one.
   it("names the current version, which is supported", () => {
-    expect(SUPPORTED_SCHEMA_VERSION).toBe(3);
+    expect(SUPPORTED_SCHEMA_VERSION).toBe(4);
     expect(SUPPORTED_SCHEMA_VERSIONS.has(SUPPORTED_SCHEMA_VERSION)).toBe(true);
   });
 
   // Plain refinement failure here; the loader is what turns it into SCHEMA_UNSUPPORTED.
   it("rejects anything older or newer", () => {
     expect(payloadManifestSchema.safeParse({ ...payload(), schemaVersion: 1 }).success).toBe(false);
-    expect(payloadManifestSchema.safeParse({ ...payload(), schemaVersion: 4 }).success).toBe(false);
+    expect(payloadManifestSchema.safeParse({ ...payload(), schemaVersion: 5 }).success).toBe(false);
     expect(payloadManifestSchema.safeParse({ ...payload(), schemaVersion: 2.5 }).success).toBe(false);
   });
 
diff --git a/test/render-generic.test.ts b/test/render-generic.test.ts
index d1d3de1..75024a7 100644
--- a/test/render-generic.test.ts
+++ b/test/render-generic.test.ts
@@ -249,6 +249,47 @@ describe("renderFile: nested placeholder tokens", () => {
   });
 });
 
+describe("renderFile: omitLineIfEmpty", () => {
+  const def = (omitLineIfEmpty?: boolean): RenderDef => ({ placeholders: { HOOK: { configPath: "docker.hook", default: "", omitLineIfEmpty } } });
+  const source = "FROM a\n${HOOK}\n\nCOPY b\n";
+
+  it("drops the whole line when the value is empty", () => {
+    expect(renderFile(source, def(true), cfg(), {})).toBe("FROM a\n\nCOPY b\n");
+  });
+
+  it("keeps the line when the value is set", () => {
+    expect(renderFile(source, def(true), cfg({ docker: { hook: "RUN x" } }), {})).toBe("FROM a\nRUN x\n\nCOPY b\n");
+  });
+
+  it("leaves an empty line without the flag, as before", () => {
+    expect(renderFile(source, def(), cfg(), {})).toBe("FROM a\n\n\nCOPY b\n");
+  });
+
+  it("drops an indented token line, CRLF included", () => {
+    expect(renderFile("a:\n  ${HOOK}  \nb\n", def(true), cfg(), {})).toBe("a:\nb\n");
+    expect(renderFile("a\r\n\t${HOOK}\r\nb\r\n", def(true), cfg(), {})).toBe("a\r\nb\r\n");
+  });
+
+  it("substitutes a token that shares its line with other text", () => {
+    expect(renderFile("RUN a ${HOOK}\n", def(true), cfg(), {})).toBe("RUN a \n");
+  });
+
+  it("drops a line of several flagged tokens, in any order", () => {
+    const a = { configPath: "docker.a", default: "", omitLineIfEmpty: true };
+    const b = { configPath: "docker.b", default: "", omitLineIfEmpty: true };
+    const source = "before\n${A}${B}${A}\nafter\n";
+    expect(renderFile(source, { placeholders: { A: a, B: b } }, cfg(), {})).toBe("before\nafter\n");
+    expect(renderFile(source, { placeholders: { B: b, A: a } }, cfg(), {})).toBe("before\nafter\n");
+  });
+
+  it("does not depend on placeholder declaration order", () => {
+    const prefix = { configPath: "docker.prefix", default: "RUN a\n" };
+    const hook = { configPath: "docker.hook", default: "", omitLineIfEmpty: true };
+    expect(renderFile("${PREFIX}${HOOK}\n", { placeholders: { PREFIX: prefix, HOOK: hook } }, cfg(), {})).toBe("RUN a\n");
+    expect(renderFile("${PREFIX}${HOOK}\n", { placeholders: { HOOK: hook, PREFIX: prefix } }, cfg(), {})).toBe("RUN a\n");
+  });
+});
+
 describe("renderFile: fragments", () => {
   const frags = { a: "FRAG-A", b: "FRAG-B", c: "FRAG-C" };
   const def: RenderDef = {