diff --git a/src/main/services/provider-background-service.ts b/src/main/services/provider-background-service.ts
index 0933734f..0bc544b3 100644
--- a/src/main/services/provider-background-service.ts
+++ b/src/main/services/provider-background-service.ts
@@ -19,6 +19,7 @@ import { ProviderRateLimitRegistry } from "./provider-rate-limit-registry";
 import { ProviderRequestStore, type ProviderBackgroundRequestRow } from "./provider-request-store";
 import { ProviderResponseObserver } from "./provider-response-observer";
 import { hashPrompt, readProviderFailureMessage, requireBackgroundText } from "./provider-response-utils";
+import { promptChars } from "./spend";
 
 const AUTH_STATE_CONFIGURED = "configured";
 const HEALTH_STATE_HEALTHY = "healthy";
@@ -60,7 +61,7 @@ export class ProviderBackgroundService {
       model: execution.provider.model,
       workspaceId: execution.workspaceId,
       promptSha256: hashPrompt(execution.prompt),
-      inputCharCount: execution.prompt.length,
+      inputCharCount: promptChars(execution.prompt, execution.instructions),
       executionMode: PROVIDER_EXECUTION_MODE.BACKGROUND,
       createdAt: new Date().toISOString(),
     });
@@ -99,7 +100,7 @@ export class ProviderBackgroundService {
         requestId,
         executionMode: PROVIDER_EXECUTION_MODE.BACKGROUND,
         startedAt,
-        inputCharCount: execution.prompt.length,
+        inputCharCount: promptChars(execution.prompt, execution.instructions),
         error,
       });
       throw error;
diff --git a/src/main/services/provider-response-runner.ts b/src/main/services/provider-response-runner.ts
index 5ec1de0a..abea2dce 100644
--- a/src/main/services/provider-response-runner.ts
+++ b/src/main/services/provider-response-runner.ts
@@ -17,7 +17,7 @@ import { type AgentTurnMessage, type AgentTurnResult, type ToolDefinition, type
 import { selectToolTurn, supportsToolTurn } from "./provider-tool-turns/router";
 import { resolveTurnCredential } from "./provider-tool-turns/credential-resolver";
 import { currentRunId } from "./run-control";
-import { budgetBlock, isPriced, providerPrices } from "./spend";
+import { budgetBlock, isPriced, promptChars, providerPrices } from "./spend";
 import {
   HEALTH_STATE_HEALTHY,
   WORKSPACE_SCOPES,
@@ -86,7 +86,7 @@ export class ProviderResponseRunner {
       });
       this.deps.requestStore.settleUsage({
         orgId: input.orgId, requestId, provider: execution.provider, rawResponseJson: result.rawResponseJson,
-        inputCharCount: execution.prompt.length, outputCharCount: result.text.length,
+        inputCharCount: promptChars(execution.prompt, execution.instructions), outputCharCount: result.text.length,
       });
       return requestId;
     } catch (error) {
@@ -96,7 +96,7 @@ export class ProviderResponseRunner {
         requestId,
         executionMode: execution.executionMode,
         startedAt,
-        inputCharCount: execution.prompt.length,
+        inputCharCount: promptChars(execution.prompt, execution.instructions),
         error,
       });
       throw error;
@@ -129,7 +129,8 @@ export class ProviderResponseRunner {
     const blocked = agent ? budgetBlock(this.deps.db, agent.id, isPriced(providerPrices(this.deps.db, provider.id)), new Date()) : null;
     if (blocked) throw new Error(blocked);
     const credential = await resolveTurnCredential({ authBroker: this.deps.authBroker, integrationKeys: this.deps.integrationKeys, orgId: input.orgId, provider });
-    const promptChars = JSON.stringify(input.messages).length;
+    // Everything the model reads: instructions, the conversation, and the tool definitions.
+    const turnInputChars = (input.instructions?.length ?? 0) + JSON.stringify(input.messages).length + JSON.stringify(input.tools).length;
     const requestId = this.deps.requestStore.create({
       agentId: agent?.id ?? null,
       taskRunId,
@@ -139,19 +140,21 @@ export class ProviderResponseRunner {
       model,
       workspaceId,
       promptSha256: hashPrompt(JSON.stringify(input.messages)),
-      inputCharCount: promptChars,
+      inputCharCount: turnInputChars,
       executionMode: PROVIDER_EXECUTION_MODE.FOREGROUND,
       createdAt: new Date().toISOString(),
     });
     const startedAt = Date.now();
     try {
       const result = await turn({ credential, model, instructions: input.instructions, messages: input.messages, tools: input.tools });
+      // Tool calls are output the model wrote, as much as its text.
+      const outputChars = result.text.length + (result.toolCalls.length > 0 ? JSON.stringify(result.toolCalls).length : 0);
       this.deps.requestStore.markSucceeded({
         orgId: input.orgId,
         requestId,
         responseText: result.text,
         rawResponseJson: result.rawResponseJson,
-        outputCharCount: result.text.length,
+        outputCharCount: outputChars,
         externalResponseId: readProviderResponseId(result.rawResponseJson),
         completedAt: new Date().toISOString(),
       });
@@ -165,7 +168,7 @@ export class ProviderResponseRunner {
       });
       this.deps.requestStore.settleUsage({
         orgId: input.orgId, requestId, provider: owner, rawResponseJson: result.rawResponseJson,
-        inputCharCount: promptChars, outputCharCount: result.text.length,
+        inputCharCount: turnInputChars, outputCharCount: outputChars,
       });
       return { ...result, requestId };
     } catch (error) {
@@ -175,7 +178,7 @@ export class ProviderResponseRunner {
         requestId,
         executionMode: PROVIDER_EXECUTION_MODE.FOREGROUND,
         startedAt,
-        inputCharCount: promptChars,
+        inputCharCount: turnInputChars,
         error,
       });
       throw error;
@@ -253,7 +256,7 @@ export class ProviderResponseRunner {
       });
       this.deps.requestStore.settleUsage({
         orgId: input.orgId, requestId, provider: execution.provider, rawResponseJson: JSON.stringify(rawEvents),
-        inputCharCount: execution.prompt.length, outputCharCount: responseText.length,
+        inputCharCount: promptChars(execution.prompt, execution.instructions), outputCharCount: responseText.length,
       });
       return requestId;
     } catch (error) {
@@ -263,7 +266,7 @@ export class ProviderResponseRunner {
         requestId,
         executionMode: execution.executionMode,
         startedAt,
-        inputCharCount: execution.prompt.length,
+        inputCharCount: promptChars(execution.prompt, execution.instructions),
         error,
       });
       throw error;
@@ -332,7 +335,7 @@ export class ProviderResponseRunner {
       model: execution.provider.model,
       workspaceId: execution.workspaceId,
       promptSha256: hashPrompt(execution.prompt),
-      inputCharCount: execution.prompt.length,
+      inputCharCount: promptChars(execution.prompt, execution.instructions),
       executionMode: execution.executionMode,
       createdAt: new Date().toISOString(),
     });
diff --git a/src/main/services/spend.ts b/src/main/services/spend.ts
index 3df37610..7ce2ca97 100644
--- a/src/main/services/spend.ts
+++ b/src/main/services/spend.ts
@@ -50,6 +50,11 @@ export function providerPrices(db: DatabaseSync, providerId: string): TokenPrice
   return { inputCentsPerMtok: row.input_cents_per_mtok, cachedInputCentsPerMtok: row.cached_input_cents_per_mtok, outputCentsPerMtok: row.output_cents_per_mtok };
 }
 
+/** Characters a call sends: the instructions count as much as the prompt. */
+export function promptChars(prompt: string, instructions: string | null): number {
+  return prompt.length + (instructions?.length ?? 0);
+}
+
 export function monthStartIso(now: Date): string {
   return new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), 1)).toISOString();
 }
diff --git a/tests/unit/char-accounting.test.ts b/tests/unit/char-accounting.test.ts
new file mode 100644
index 00000000..daaa84e8
--- /dev/null
+++ b/tests/unit/char-accounting.test.ts
@@ -0,0 +1,40 @@
+import { randomUUID } from "node:crypto";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { describe, expect, test } from "vitest";
+import { DatabaseConnection } from "../../src/main/database/connection";
+import { OrganizationService } from "../../src/main/services/organization-service";
+import { ProviderService } from "../../src/main/services/provider-service";
+import { providerAdapters } from "../../src/main/services/provider-adapters";
+import type { AgentTurnResult, ToolDefinition } from "../../src/main/services/provider-tool-turn";
+
+const testVault = {
+  encryptSecret: (secret: string) => Buffer.from(secret, "utf8"),
+  decryptSecret: (ciphertext: Buffer) => ciphertext.toString("utf8"),
+};
+
+describe("character accounting", () => {
+  test("a tool turn counts instructions, conversation and tool definitions in, and text plus tool calls out", async () => {
+    const toolCalls = [{ id: "c1", name: "send_message", arguments: { channel: "general", body: "Shipping today." } }];
+    const turn = async (): Promise<AgentTurnResult> => ({ text: "Posting.", toolCalls, rawResponseJson: "{}" });
+    const connection = new DatabaseConnection(join(tmpdir(), `ac-chars-${randomUUID()}.db`));
+    const providers = new ProviderService(connection.db, providerAdapters, testVault, undefined, turn);
+    let orgId = "";
+    let providerId = "";
+    connection.transaction(() => {
+      orgId = new OrganizationService(connection.db).createOrganization({ organizationName: "Acme", employeeName: "Dana", mission: "m", goal: "g" });
+      providerId = (connection.db.prepare("select id from providers where org_id = ? and provider_key = 'openai'").get(orgId) as { id: string }).id;
+      providers.saveCredential({ orgId, providerId, secret: "sk-test", model: "gpt-5.4" });
+    });
+    const instructions = "You run this company.";
+    const messages = [{ role: "user" as const, text: "Kick off the launch." }];
+    const tools: ToolDefinition[] = [{ name: "send_message", description: "Post a message.", parameters: { type: "object", properties: {} } }];
+    const result = await providers.runToolTurn({ orgId, providerId, workspaceId: null, instructions, messages, tools });
+
+    expect(connection.db.prepare("select input_char_count, output_char_count from provider_requests where id = ?").get(result.requestId)).toEqual({
+      input_char_count: instructions.length + JSON.stringify(messages).length + JSON.stringify(tools).length,
+      output_char_count: "Posting.".length + JSON.stringify(toolCalls).length,
+    });
+    connection.close();
+  });
+});
diff --git a/tests/unit/provider-background-service.test.ts b/tests/unit/provider-background-service.test.ts
index 4ac978b0..97cd3c63 100644
--- a/tests/unit/provider-background-service.test.ts
+++ b/tests/unit/provider-background-service.test.ts
@@ -88,11 +88,11 @@ describe("provider background service", () => {
       state: PROVIDER_REQUEST_STATE.SUCCEEDED,
       response_text: "Background analysis complete.",
       external_response_id: "resp_bg_1",
-      input_char_count: 17,
+      input_char_count: "Run long research".length + "Use verified citations.".length,
       output_char_count: 29,
     });
     expect(JSON.parse(request.raw_response_json)).toMatchObject({ id: "resp_bg_1", status: "completed" });
-    expect(usage).toEqual({ request_count: 1, input_char_count: 17, output_char_count: 29 });
+    expect(usage).toEqual({ request_count: 1, input_char_count: 40, output_char_count: 29 });
     expect(signal).toEqual({ success: 1 });
     connection.close();
   });