diff --git a/.env.example b/.env.example
index ffdc314..33edbcf 100644
--- a/.env.example
+++ b/.env.example
@@ -12,7 +12,6 @@ ENABLE_GOLDEN_RECORDS=false
 ENABLE_EXTERNAL_CONNECTIONS=true
 ALLOW_PRIVATE_DATABASE_HOSTS=false
 CONNECTION_ENCRYPTION_KEY=
-AUTH_SIGNING_KEY=
 DATABASE_CONNECTION_TIMEOUT_SECONDS=5
 DATABASE_STATEMENT_TIMEOUT_MS=10000
 DATABASE_MAX_RESULT_ROWS=500
diff --git a/README.md b/README.md
index 91610a0..7843cc6 100644
--- a/README.md
+++ b/README.md
@@ -112,7 +112,7 @@ For the default Compose stack, optional vector features are off so schema intros
 | `EMBEDDING_PROVIDER`, `EMBEDDING_MODEL` | Local semantic-retrieval configuration |
 | `ENABLE_SCHEMA_RAG`, `ENABLE_GOLDEN_RECORDS` | Optional embedding features |
 | `ENABLE_EXTERNAL_CONNECTIONS`, `ALLOW_PRIVATE_DATABASE_HOSTS` | BYOD and SSRF policy flags |
-| `CONNECTION_ENCRYPTION_KEY`, `AUTH_SIGNING_KEY` | Backend-only Fernet and session signing secrets |
+| `CONNECTION_ENCRYPTION_KEY` | Backend-only Fernet key; session signing is derived from it with domain separation |
 | `DATABASE_*` | Connect timeout, statement timeout, SQL length, and result caps |
 | `SCHEMA_*_TABLE_LIMIT` | Full-context and retrieval bounds |
 | `NEXT_PUBLIC_API_URL` | Browser-visible API `/api/v1` URL |
diff --git a/apps/api/.env.example b/apps/api/.env.example
index 291ae1f..396de61 100644
--- a/apps/api/.env.example
+++ b/apps/api/.env.example
@@ -15,7 +15,6 @@ ENABLE_GOLDEN_RECORDS=false
 ENABLE_EXTERNAL_CONNECTIONS=false
 ALLOW_PRIVATE_DATABASE_HOSTS=false
 CONNECTION_ENCRYPTION_KEY=
-AUTH_SIGNING_KEY=
 DATABASE_CONNECTION_TIMEOUT_SECONDS=5
 DATABASE_STATEMENT_TIMEOUT_MS=10000
 DATABASE_MAX_RESULT_ROWS=500
diff --git a/apps/api/README.md b/apps/api/README.md
index 96d315c..99c9804 100644
--- a/apps/api/README.md
+++ b/apps/api/README.md
@@ -28,7 +28,7 @@ uvicorn app.main:app --reload --port 8000
 
 Production startup never creates tables. Alembic creates application tables and pgvector. The demo seed is idempotent. Use `../../scripts/create_readonly_role.sql` as a reviewed template and run query traffic with that role.
 
-Saved customer credentials require `CONNECTION_ENCRYPTION_KEY` (a Fernet key). Signed workspace sessions require a separate `AUTH_SIGNING_KEY`. Generate them with the commands in `../../docs/deployment.md`. BYOD accepts URL or structured PostgreSQL input, requires SSL, blocks unsafe networks by default, and stores normalized schema snapshots without row data.
+Saved customer credentials require `CONNECTION_ENCRYPTION_KEY` (a Fernet key). Workspace-session signing uses a domain-separated key derived from that Fernet key, so no second signing secret is required. Generate the key with the command in `../../docs/deployment.md`. BYOD accepts URL or structured PostgreSQL input, requires SSL, blocks unsafe networks by default, and stores normalized schema snapshots without row data.
 
 ## Safety model
 
diff --git a/apps/api/app/auth/dependencies.py b/apps/api/app/auth/dependencies.py
index bbf572c..c806a92 100644
--- a/apps/api/app/auth/dependencies.py
+++ b/apps/api/app/auth/dependencies.py
@@ -1,4 +1,5 @@
 import base64
+import binascii
 import hashlib
 import hmac
 import json
@@ -13,9 +14,17 @@
 
 
 def _key() -> bytes:
-    if not settings.AUTH_SIGNING_KEY:
-        raise DependencyError("AUTH_SIGNING_KEY is required for saved connection sessions")
-    return settings.AUTH_SIGNING_KEY.encode()
+    if not settings.CONNECTION_ENCRYPTION_KEY:
+        raise DependencyError("CONNECTION_ENCRYPTION_KEY is required for saved connection sessions")
+    try:
+        key_material = base64.b64decode(
+            settings.CONNECTION_ENCRYPTION_KEY.encode(), altchars=b"-_", validate=True
+        )
+    except (binascii.Error, ValueError) as exc:
+        raise DependencyError("CONNECTION_ENCRYPTION_KEY is invalid") from exc
+    if len(key_material) != 32:
+        raise DependencyError("CONNECTION_ENCRYPTION_KEY is invalid")
+    return hmac.new(key_material, b"querymindai/workspace-session/v1", hashlib.sha256).digest()
 
 
 def issue_session() -> tuple[str, str, int]:
diff --git a/apps/api/app/core/config.py b/apps/api/app/core/config.py
index d1c31b4..f8f2190 100644
--- a/apps/api/app/core/config.py
+++ b/apps/api/app/core/config.py
@@ -23,7 +23,6 @@ class Settings(BaseSettings):
     ENABLE_EXTERNAL_CONNECTIONS: bool = False
     ALLOW_PRIVATE_DATABASE_HOSTS: bool = False
     CONNECTION_ENCRYPTION_KEY: str | None = None
-    AUTH_SIGNING_KEY: str | None = None
     AUTH_SESSION_TTL_SECONDS: int = Field(2592000, ge=300, le=31536000)
     DATABASE_CONNECTION_TIMEOUT_SECONDS: int = Field(5, ge=1, le=30)
     DATABASE_STATEMENT_TIMEOUT_MS: int = Field(10000, ge=100, le=300000)
diff --git a/apps/api/tests/test_auth.py b/apps/api/tests/test_auth.py
index a898697..cb3977c 100644
--- a/apps/api/tests/test_auth.py
+++ b/apps/api/tests/test_auth.py
@@ -1,12 +1,19 @@
 import pytest
+from cryptography.fernet import Fernet
 
 from app.auth.dependencies import get_current_user_id, issue_session
 from app.core.config import settings
-from app.core.exceptions import AuthenticationError
+from app.core.exceptions import AuthenticationError, DependencyError
 
 
 def test_signed_session_subject_cannot_be_forged(monkeypatch):
-    monkeypatch.setattr(settings,"AUTH_SIGNING_KEY","test-signing-key-not-for-production")
+    monkeypatch.setattr(settings, "CONNECTION_ENCRYPTION_KEY", Fernet.generate_key().decode())
     token,user_id,_=issue_session()
     assert get_current_user_id(f"Bearer {token}")==user_id
     with pytest.raises(AuthenticationError): get_current_user_id(f"Bearer {token}tampered")
+
+
+def test_session_requires_connection_encryption_key(monkeypatch):
+    monkeypatch.setattr(settings, "CONNECTION_ENCRYPTION_KEY", None)
+    with pytest.raises(DependencyError, match="CONNECTION_ENCRYPTION_KEY"):
+        issue_session()
diff --git a/docker-compose.yml b/docker-compose.yml
index fff069d..474f6fb 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -32,7 +32,6 @@ services:
       ENABLE_EXTERNAL_CONNECTIONS: ${ENABLE_EXTERNAL_CONNECTIONS:-true}
       ALLOW_PRIVATE_DATABASE_HOSTS: ${ALLOW_PRIVATE_DATABASE_HOSTS:-false}
       CONNECTION_ENCRYPTION_KEY: ${CONNECTION_ENCRYPTION_KEY:-}
-      AUTH_SIGNING_KEY: ${AUTH_SIGNING_KEY:-}
       DATABASE_CONNECTION_TIMEOUT_SECONDS: ${DATABASE_CONNECTION_TIMEOUT_SECONDS:-5}
       DATABASE_STATEMENT_TIMEOUT_MS: ${DATABASE_STATEMENT_TIMEOUT_MS:-10000}
       DATABASE_MAX_RESULT_ROWS: ${DATABASE_MAX_RESULT_ROWS:-500}
diff --git a/docs/deployment.md b/docs/deployment.md
index dc65d0a..f43b359 100644
--- a/docs/deployment.md
+++ b/docs/deployment.md
@@ -4,16 +4,15 @@
 
 ```bash
 cp .env.example .env
-# Generate backend-only secrets and paste them into .env:
+# Generate the backend-only credential encryption key and paste it into .env:
 python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
-python -c "import secrets; print(secrets.token_urlsafe(48))"
 docker compose up --build
 # Optional local provider:
 docker compose --profile ollama up --build
 docker compose exec ollama ollama pull sqlcoder
 ```
 
-Use the first generated value for `CONNECTION_ENCRYPTION_KEY` and the second for `AUTH_SIGNING_KEY`. Open web at `http://localhost:4028`, API docs at `http://localhost:8000/docs`, and check `/health` then `/ready`. Configure a provider for generation. BYOD databases must be publicly reachable PostgreSQL on port 5432 with SSL and a read-only role.
+Use the generated value for `CONNECTION_ENCRYPTION_KEY`. Session signing is derived from this key, so no separate signing secret is needed. Open web at `http://localhost:4028`, API docs at `http://localhost:8000/docs`, and check `/health` then `/ready`. Configure a provider for generation. BYOD databases must be publicly reachable PostgreSQL on port 5432 with SSL and a read-only role.
 
 ## Supabase application database
 
@@ -33,7 +32,7 @@ Enter the complete value only in Render's secret `DATABASE_URL` field. Never com
 
 1. Push this repository to GitHub. In Render choose **New → Blueprint**, connect that repository, and select `render.yaml`.
 2. Review creation or update of `querymind-api` and `querymind-web`. The Blueprint intentionally does not provision a Render PostgreSQL database.
-3. Enter backend secrets in the non-synced fields: Supabase session-pooler `DATABASE_URL`, Groq `LLM_API_KEY`, a Fernet `CONNECTION_ENCRYPTION_KEY`, and an independent random `AUTH_SIGNING_KEY`. Never reuse or commit these values.
+3. Enter backend secrets in the non-synced fields: Supabase session-pooler `DATABASE_URL`, Groq `LLM_API_KEY`, and a Fernet `CONNECTION_ENCRYPTION_KEY`. Never reuse or commit these values.
 4. Set `CORS_ALLOW_ORIGINS` on the API to the final HTTPS web origin, without a trailing slash.
 5. Deploy the API. On the free tier, the API start command runs `alembic upgrade head` before starting Uvicorn because Render does not support pre-deploy commands for free services. Confirm `https://<api-host>/health` and `/ready`.
 6. Set `NEXT_PUBLIC_API_URL` on `querymind-web` to `https://<api-host>/api/v1`, then trigger a clean frontend deploy. Render does not provide a supported Blueprint interpolation from another web service’s eventual public hostname into a Next.js build variable; this manual build-time step is required.
diff --git a/docs/local-development.md b/docs/local-development.md
index cb716c0..1a464bf 100644
--- a/docs/local-development.md
+++ b/docs/local-development.md
@@ -23,14 +23,13 @@ cd QueryMindAI
 cp .env.example .env
 ```
 
-Generate two independent backend secrets:
+Generate the backend credential-encryption key:
 
 ```bash
 python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())"
-python -c "import secrets; print(secrets.token_urlsafe(48))"
 ```
 
-Put the first value in `CONNECTION_ENCRYPTION_KEY` and the second in `AUTH_SIGNING_KEY` in your local `.env`. Never commit that file.
+Put the value in `CONNECTION_ENCRYPTION_KEY` in your local `.env`. Workspace-session signing is derived from it, so no second signing secret is needed. Never commit that file.
 
 ### Option A: local Ollama
 
@@ -107,7 +106,7 @@ alembic upgrade head
 uvicorn app.main:app --reload --port 8000
 ```
 
-At minimum, set the application `DATABASE_URL`, `ENABLE_EXTERNAL_CONNECTIONS=true`, and the two generated `CONNECTION_ENCRYPTION_KEY` and `AUTH_SIGNING_KEY` values in `apps/api/.env`. Keep `CORS_ALLOW_ORIGINS=http://localhost:4028` for the default frontend port.
+At minimum, set the application `DATABASE_URL`, `ENABLE_EXTERNAL_CONNECTIONS=true`, and the generated `CONNECTION_ENCRYPTION_KEY` value in `apps/api/.env`. Keep `CORS_ALLOW_ORIGINS=http://localhost:4028` for the default frontend port.
 
 In another terminal:
 
@@ -123,7 +122,7 @@ The browser API URL must include `/api/v1`. `CORS_ALLOW_ORIGINS` on the API must
 ## Troubleshooting
 
 - **Connections are disabled:** set `ENABLE_EXTERNAL_CONNECTIONS=true` in the API environment and restart it.
-- **Encryption/signing configuration error:** provide valid, different `CONNECTION_ENCRYPTION_KEY` and `AUTH_SIGNING_KEY` values.
+- **Encryption/signing configuration error:** provide a valid Fernet `CONNECTION_ENCRYPTION_KEY` value.
 - **Host rejected:** public mode rejects localhost, private, link-local, reserved, and metadata IP ranges. Use a public hostname or opt into private hosts only in a trusted local environment.
 - **Browser reports a network or CORS error:** verify `NEXT_PUBLIC_API_URL`, `CORS_ALLOW_ORIGINS`, and `/health`. Next.js public variables are embedded at build time, so rebuild the web image after changing the API URL.
 - **Generation fails but schema browsing works:** verify the LLM provider URL, model, and backend-only key. Database credentials and LLM keys must never be added to `NEXT_PUBLIC_*` variables.
diff --git a/docs/security.md b/docs/security.md
index 35c6e3d..c491796 100644
--- a/docs/security.md
+++ b/docs/security.md
@@ -4,7 +4,7 @@
 
 PostgreSQL credentials are serialized and encrypted with Fernet authenticated encryption using backend-only `CONNECTION_ENCRYPTION_KEY`. Responses contain only host, database, username, SSL mode, and status; passwords, decrypted configuration, and raw URLs are never returned or logged. Deletion cascades catalog snapshots, drafts, and BYOD history and explicitly removes connection-keyed verified examples. Audit records retain only identifiers and safe status metadata.
 
-Application encryption is not an enterprise vault. The entire dataset must be re-encrypted to rotate the key; losing the key makes credentials unrecoverable. Mature deployments should use a managed secret store/KMS. `AUTH_SIGNING_KEY` signs browser-bound anonymous workspace sessions. These sessions are not account authentication, recovery, organization membership, MFA, or revocation infrastructure; use an external identity provider for a true multi-user deployment.
+Application encryption is not an enterprise vault. The entire dataset must be re-encrypted to rotate the key; losing the key makes credentials unrecoverable. Mature deployments should use a managed secret store/KMS. Browser-bound anonymous workspace sessions are signed with a domain-separated HMAC key derived from `CONNECTION_ENCRYPTION_KEY`; the derived key is never persisted. Rotating the encryption key therefore also invalidates existing sessions. These sessions are not account authentication, recovery, organization membership, MFA, or revocation infrastructure; use an external identity provider for a true multi-user deployment.
 
 ## Network and SSRF controls
 
diff --git a/render.yaml b/render.yaml
index 0d6d9af..2f55061 100644
--- a/render.yaml
+++ b/render.yaml
@@ -26,8 +26,6 @@ services:
         sync: false
       - key: CONNECTION_ENCRYPTION_KEY
         sync: false
-      - key: AUTH_SIGNING_KEY
-        sync: false
       - key: DATABASE_CONNECTION_TIMEOUT_SECONDS
         value: "5"
       - key: DATABASE_STATEMENT_TIMEOUT_MS