diff --git a/.env.example b/.env.example
index d3b3f4b364..270f16855e 100644
--- a/.env.example
+++ b/.env.example
@@ -1414,7 +1414,7 @@ APP_LOG_TO_FILE=true
 
 # Whether call log pipeline capture stores stream chunks when enabled in settings.
 # Only applies when call_log_pipeline_enabled=true.
-# Default: true
+# Default: false (opt-in — saves disk: stream chunks are the biggest call-log artifact)
 # CALL_LOG_PIPELINE_CAPTURE_STREAM_CHUNKS=true
 
 # Maximum call log artifact size for pipeline captures, in KB.
@@ -1893,7 +1893,7 @@ APP_LOG_TO_FILE=true
 
 # Log request shape (content-type + content-length) for large chat payloads.
 # Used by: src/app/api/v1/chat/completions/route.ts. Set to "0" to silence.
-# Default: enabled.
+# Default: disabled (opt-in).
 # OMNIROUTE_LOG_REQUEST_SHAPE=1
 
 # Write raw (untruncated) request/response JSON in call log artifacts.
diff --git a/docs/reference/ENVIRONMENT.md b/docs/reference/ENVIRONMENT.md
index 161b9f1252..d14e2ec18d 100644
--- a/docs/reference/ENVIRONMENT.md
+++ b/docs/reference/ENVIRONMENT.md
@@ -736,7 +736,7 @@ The logging system writes to both stdout and rotated log files. All configuratio
 | `CALL_LOGS_TABLE_MAX_ROWS`                | `100000`                   | Max rows in the `call_logs` SQLite table before pruning.                          |
 | `ENABLE_REQUEST_LOGS`                     | _(unset)_                  | Force detailed request logging on or off, overriding the dashboard setting.       |
 | `MAX_PENDING_REQUEST_AGE_MS`              | `3600000` (1 hour)         | Max age for orphaned active request log entries before in-memory cleanup.         |
-| `CALL_LOG_PIPELINE_CAPTURE_STREAM_CHUNKS` | `true`                     | Store stream chunks in pipeline artifacts when `call_log_pipeline_enabled=true`.  |
+| `CALL_LOG_PIPELINE_CAPTURE_STREAM_CHUNKS` | `false`                    | Store stream chunks in pipeline artifacts when `call_log_pipeline_enabled=true`. Opt-in (`true`) — off by default to save disk. |
 | `CALL_LOG_PIPELINE_MAX_SIZE_KB`           | `512`                      | Max pipeline call log artifact size in KB when `call_log_pipeline_enabled=true`.  |
 | `PROXY_LOGS_TABLE_MAX_ROWS`               | `100000`                   | Max rows in the `proxy_logs` SQLite table before pruning.                         |
 | `APP_LOG_ROTATION_CHECK_INTERVAL_MS`      | `60000` (1 min)            | How often `src/lib/logRotation.ts` re-checks the active log file size.            |
@@ -976,7 +976,7 @@ changing them requires a code edit, not an env var:
 | `CURSOR_AGENT_CLI_VERSION`       | _(detect / pin)_    | `open-sse/utils/cursorAgentCliVersion.ts`  | Agent CLI build id (`YYYY.MM.DD-<hash>`) for `x-cursor-client-version: cli-…` on Agent Run.   |
 | `CURSOR_DATA_DIR`                | _(probed)_          | `open-sse/utils/cursorAgentCliVersion.ts`  | Override Cursor Agent CLI data dir (`…/versions/<id>`); same var the official agent uses.    |
 | `CURSOR_TOKEN`                   | _(unset)_           | `scripts/ad-hoc/cursor-tap.cjs`            | Direct Cursor bearer token used by developer tooling.                                        |
-| `OMNIROUTE_LOG_REQUEST_SHAPE`    | enabled (`!== "0"`) | `src/app/api/v1/chat/completions/route.ts` | Log content-type/length markers for large chat payloads. Set `"0"` to silence.               |
+| `OMNIROUTE_LOG_REQUEST_SHAPE`    | disabled (opt-in via `"1"`) | `src/app/api/v1/chat/completions/route.ts` | Log content-type/length markers for large chat payloads when `"1"` is set. Off by default to reduce log noise. |
 | `DEBUG_RESPONSES_SSE_TO_JSON`    | _(unset)_           | `open-sse/handlers/responseTranslator.ts`  | Set `true` to log Responses API SSE→JSON translation details.                                |
 | `NEXT_PUBLIC_OMNIROUTE_E2E_MODE` | _(unset)_           | E2E test harness                           | Set `true` to enable E2E test mode (relaxed auth, test hooks).                               |
 
diff --git a/src/app/api/v1/chat/completions/route.ts b/src/app/api/v1/chat/completions/route.ts
index 4c8f16331a..d86f6685b0 100644
--- a/src/app/api/v1/chat/completions/route.ts
+++ b/src/app/api/v1/chat/completions/route.ts
@@ -109,8 +109,8 @@ export async function POST(request) {
   try {
     // One-line marker for diagnosing 413 / Server-Action interceptions.
     // Logs only when Content-Length is present so debug noise stays low for
-    // typical chat payloads. Toggle off via OMNIROUTE_LOG_REQUEST_SHAPE=0.
-    if (process.env.OMNIROUTE_LOG_REQUEST_SHAPE !== "0") {
+    // typical chat payloads. Opt-in via OMNIROUTE_LOG_REQUEST_SHAPE=1.
+    if (process.env.OMNIROUTE_LOG_REQUEST_SHAPE === "1") {
       const ct = request.headers.get("content-type") ?? "";
       const cl = request.headers.get("content-length");
       if (cl && Number(cl) > 256 * 1024) {
diff --git a/src/lib/logEnv.ts b/src/lib/logEnv.ts
index 8486628b4e..eb40bda66a 100644
--- a/src/lib/logEnv.ts
+++ b/src/lib/logEnv.ts
@@ -116,7 +116,7 @@ export function getCallLogsTableMaxRows(): number {
 }
 
 export function getCallLogPipelineCaptureStreamChunks(): boolean {
-  return parseBoolean(process.env.CALL_LOG_PIPELINE_CAPTURE_STREAM_CHUNKS, true);
+  return parseBoolean(process.env.CALL_LOG_PIPELINE_CAPTURE_STREAM_CHUNKS, false);
 }
 
 export function getCallLogPipelineMaxSizeBytes(): number {