diff --git a/AGENTS.md b/AGENTS.md
index 0d0f9635c0..3428b7a315 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -128,6 +128,18 @@ app, err := api.Database.GetOAuth2ProviderAppByClientID(ctx, clientID)
 - Keep nullable-field handling, type coercion, and response shaping in the
   converter so handlers stay focused on request flow and authorization.
 
+### Transactions and `InTx`
+
+- Inside `db.InTx(...)` closures, do not use the outer store (`api.Database`,
+  `p.db`, etc.) directly or indirectly. Use the `tx` handle for DB work inside
+  the closure, or fetch read-only inputs before opening the transaction.
+- Watch for helper methods on a receiver that hide outer-store access. A call
+  like `p.someHelper(ctx)` is still unsafe inside `InTx` if that helper uses
+  `p.db` internally.
+- Using the outer store while a transaction is open can hold one connection and
+  then block on another pool checkout, which can cause pool starvation and
+  `idle in transaction` incidents under load.
+
 ## Quick Reference
 
 ### Full workflows available in imported WORKFLOWS.md
diff --git a/coderd/x/chatd/chatd.go b/coderd/x/chatd/chatd.go
index 2a4ab237f0..474675476d 100644
--- a/coderd/x/chatd/chatd.go
+++ b/coderd/x/chatd/chatd.go
@@ -875,6 +875,10 @@ func (p *Server) CreateChat(ctx context.Context, opts CreateOptions) (database.C
 	if opts.Labels == nil {
 		opts.Labels = database.StringMap{}
 	}
+	// Resolve the deployment prompt before opening the transaction so
+	// chat creation does not hold one DB connection while waiting for
+	// another pool checkout.
+	deploymentPrompt := p.resolveDeploymentSystemPrompt(ctx)
 
 	var chat database.Chat
 	txErr := p.db.InTx(func(tx database.Store) error {
@@ -915,7 +919,6 @@ func (p *Server) CreateChat(ctx context.Context, opts CreateOptions) (database.C
 			return xerrors.Errorf("insert chat: %w", err)
 		}
 
-		deploymentPrompt := p.resolveDeploymentSystemPrompt(ctx)
 		userPrompt := SanitizePromptText(opts.SystemPrompt)
 		var workspaceAwareness string
 		if opts.WorkspaceID.Valid {
diff --git a/coderd/x/chatd/subagent.go b/coderd/x/chatd/subagent.go
index 4792df2b66..25620aa5ef 100644
--- a/coderd/x/chatd/subagent.go
+++ b/coderd/x/chatd/subagent.go
@@ -452,6 +452,10 @@ func (p *Server) createChildSubagentChatWithOptions(
 		return database.Chat{}, xerrors.Errorf("marshal labels: %w", err)
 	}
 	childSystemPrompt := SanitizePromptText(opts.systemPrompt)
+	// Resolve the deployment prompt before opening the transaction so
+	// child chat creation does not hold one DB connection while waiting
+	// for another pool checkout.
+	deploymentPrompt := p.resolveDeploymentSystemPrompt(ctx)
 
 	var child database.Chat
 	txErr := p.db.InTx(func(tx database.Store) error {
@@ -482,7 +486,6 @@ func (p *Server) createChildSubagentChatWithOptions(
 			return xerrors.Errorf("insert child chat: %w", err)
 		}
 
-		deploymentPrompt := p.resolveDeploymentSystemPrompt(ctx)
 		workspaceAwareness := "There is no workspace associated with this chat yet. Create one using the create_workspace tool before using workspace tools like execute, read_file, write_file, etc."
 		if insertedChat.WorkspaceID.Valid {
 			workspaceAwareness = "This chat is attached to a workspace. You can use workspace tools like execute, read_file, write_file, etc."