Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
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Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
Loading
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix"); } } catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
Loading
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length \u003e 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms"); } } catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
Skip to content

Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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8 commits
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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
View file
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
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Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
Loading
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links"); } } catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); } })(); (function(){ try { var __m = "youtube.com"; var __re = new RegExp('^' + "youtube\\.com" + '
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Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
Loading
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default"); } } catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
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Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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8 commits
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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Original file line numberDiff line numberDiff line change
Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode"); } } catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); } })(); })();
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Improve token caching.#1366

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Merged
jsourcebot merged 8 commits into from
Jun 24, 2026
Merged

Improve token caching. #1366

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f929e9a
feat(web): add layered prompt caching for the Ask agent
jsourcebot Jun 22, 2026
8c9142e
feat(web): advance the prompt-cache tail marker per agent step
jsourcebot Jun 23, 2026
6d2ce96
fix(web): bound the cache-break snapshot map and use sha256 for its s…
jsourcebot Jun 23, 2026
f024e8c
docs: update changelog for prompt caching
jsourcebot Jun 23, 2026
93ebced
refactor(web): drop the tools-block prompt-cache breakpoint
jsourcebot Jun 23, 2026
b8c8b23
clean up comments
jsourcebot Jun 24, 2026
8610781
trim comments further
jsourcebot Jun 24, 2026
cd7ae3e
refactor(web): always enable static-prefix prompt caching
jsourcebot Jun 24, 2026
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line numberDiff line numberDiff line change
Expand Up@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed
- [EE] Improved Ask Sourcebot prompt caching by splitting static and dynamic prompt sections and advancing cache breakpoints after every agent step instead of only after each message. [#1366](https://github.com/sourcebot-dev/sourcebot/pull/1366)

### Added
- Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)

Expand Down
8 changes: 8 additions & 0 deletions packages/shared/src/env.server.ts
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Expand Up@@ -311,6 +311,14 @@ const options = {

SOURCEBOT_CHAT_MAX_STEP_COUNT: numberSchema.default(100),
SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED: booleanSchema.default('true'),
/** TTL for the static block. The moving tail marker always uses the 5m default. */
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: z.enum(['5m', '1h']).default('5m'),
/**
* Observability: when enabled, logs a warning on unexpected prompt-cache
* breaks (static-prefix signature changes, or zero cache reads on a
* continuation step). Does not affect request behavior.
*/
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: booleanSchema.default('false'),
SOURCEBOT_MCP_TOOL_CALL_TIMEOUT_MS: numberSchema.int().positive().max(maxTimerDelayMs).default(60000),

DEBUG_WRITE_CHAT_MESSAGES_TO_FILE: booleanSchema.default('false'),
Expand Down
9 changes: 9 additions & 0 deletions packages/web/src/app/api/(server)/ee/chat/route.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
import { sew } from "@/middleware/sew";
import { getAskMcpAvailabilityAnalytics, getAskMcpTurnCompletedAnalytics } from "@/ee/features/chat/askMcpAnalytics.server";
import { createMessageStream } from "@/ee/features/chat/agent";
import { getPromptCacheStrategy } from "@/ee/features/chat/promptCaching";
import { additionalChatRequestParamsSchema } from "@/features/chat/types";
import { getLanguageModelKey } from "@/features/chat/utils";
import { checkAskEntitlement, getConfiguredLanguageModels, isOwnerOfChat, updateChatMessages } from "@/features/chat/utils.server";
Expand DownExpand Up@@ -88,6 +89,13 @@ export const POST = apiHandler(async (req: NextRequest) => {

const { model, providerOptions, temperature } = await getAISDKLanguageModelAndOptions(languageModelConfig);

// No-op for non-Anthropic providers / when caching is disabled, so
// it never perturbs other providers' requests.
const promptCacheStrategy = getPromptCacheStrategy(
languageModelConfig.provider,
env.SOURCEBOT_CHAT_PROMPT_CACHING_ENABLED === 'true',
);

const expandedRepos = (await Promise.all(selectedSearchScopes.map(async (scope) => {
if (scope.type === 'repo') return [scope.value];
if (scope.type === 'reposet') {
Expand DownExpand Up@@ -131,6 +139,7 @@ export const POST = apiHandler(async (req: NextRequest) => {
disabledMcpServerIds,
model,
modelName: languageModelConfig.displayName ?? languageModelConfig.model,
promptCacheStrategy,
modelProviderOptions: providerOptions,
modelTemperature: temperature,
userId: user?.id,
Expand Down
192 changes: 187 additions & 5 deletions packages/web/src/ee/features/chat/agent.test.ts
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Original file line numberDiff line numberDiff line change
@@ -1,6 +1,8 @@
import { beforeEach, describe, expect, test, vi } from 'vitest';
import type { ModelMessage } from 'ai';
import type { ProviderOptions } from '@ai-sdk/provider-utils';
import type { SBChatMessage, SBChatMessagePart } from '@/features/chat/types';
import type { PromptCacheStrategy } from './promptCaching';

const mockLogger = vi.hoisted(() => ({
debug: vi.fn(),
Expand All@@ -25,6 +27,8 @@ vi.mock('@sourcebot/shared', () => ({
SOURCEBOT_CHAT_MAX_STEP_COUNT: 8,
SOURCEBOT_CHAT_MODEL_TEMPERATURE: 0,
SOURCEBOT_TELEMETRY_PII_COLLECTION_ENABLED: 'false',
SOURCEBOT_CHAT_PROMPT_CACHE_STATIC_TTL: '5m',
SOURCEBOT_CHAT_PROMPT_CACHE_BREAK_DETECTION_ENABLED: 'false',
},
getDBConnectionString: () => 'postgresql://sourcebot:sourcebot@db.example.com:5432/sourcebot',
}));
Expand DownExpand Up@@ -94,6 +98,11 @@ vi.mock('ai', async (importOriginal) => {
});

const { createMessageStream } = await import('./agent');
const { getPromptCacheStrategy } = await import('./promptCaching');

// Strategies reused across the prompt-caching tests below.
const anthropicStrategy = getPromptCacheStrategy('anthropic', true);
const noopStrategy = getPromptCacheStrategy('openai', true);

const listReposInput = {
sort: 'name',
Expand DownExpand Up@@ -150,7 +159,29 @@ const createFakeStreamResult = () => ({
}),
});

const runCreateMessageStream = async (messages: SBChatMessage[]) => {
type FakePrepareStep = (opts: {
steps: Array<{ toolResults: Array<{ toolName: string; output: unknown }> }>;
stepNumber: number;
model: unknown;
messages: ModelMessage[];
}) =>
| { messages?: ModelMessage[]; activeTools?: string[] }
| Promise<{ messages?: ModelMessage[]; activeTools?: string[] }>;

interface StreamTextArgs {
messages: ModelMessage[];
system: Array<{ role: 'system'; content: string; providerOptions?: ProviderOptions }>;
tools: Record<string, { providerOptions?: ProviderOptions }>;
prepareStep?: FakePrepareStep;
}

const runCreateMessageStream = async (
messages: SBChatMessage[],
opts: {
promptCacheStrategy?: PromptCacheStrategy;
selectedRepos?: string[];
} = {},
): Promise<StreamTextArgs> => {
const convertedLastTurn: ModelMessage = {
role: 'assistant',
content: 'converted-last-turn',
Expand All@@ -161,10 +192,13 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
const props = {
chatId: 'chat-id',
messages,
selectedRepos: [],
selectedRepos: opts.selectedRepos ?? [],
prisma: {},
model: {},
modelName: 'test-model',
// Default to a no-op strategy so the approval-continuation tests below
// (which assert plain, unmarked messages) are unaffected by caching.
promptCacheStrategy: opts.promptCacheStrategy ?? noopStrategy,
onFinish: vi.fn(),
onError: () => 'error',
} as unknown as Parameters<typeof createMessageStream>[0];
Expand All@@ -188,7 +222,7 @@ const runCreateMessageStream = async (messages: SBChatMessage[]) => {
throw new Error('Expected streamText to be called with messages.');
}

return streamTextArgs.messages as ModelMessage[];
return streamTextArgs as StreamTextArgs;
};

beforeEach(() => {
Expand DownExpand Up@@ -216,7 +250,7 @@ describe('createMessageStream approval continuation', () => {
approvalPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand DownExpand Up@@ -249,7 +283,7 @@ describe('createMessageStream approval continuation', () => {
dynamicApprovalRespondedPart,
]);

const streamTextMessages = await runCreateMessageStream([
const { messages: streamTextMessages } = await runCreateMessageStream([
createUserMessage(),
assistantMessage,
]);
Expand All@@ -265,3 +299,151 @@ describe('createMessageStream approval continuation', () => {
});
});
});

const EPHEMERAL = { type: 'ephemeral' };

describe('createMessageStream prompt caching', () => {
test('marks the static system block for the Anthropic family', async () => {
const { system, messages } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// No repos / files / MCP tools → only the static system block.
expect(system).toHaveLength(1);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// The tail marker is applied per-step in prepareStep, not on the messages
// handed to streamText — those stay unmarked.
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
});

test('moves the tail marker onto the last message of each step via prepareStep', async () => {
const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});
expect(prepareStep).toBeTypeOf('function');

// Step 0: a single input message → marker lands on it.
const step0 = await prepareStep!({
steps: [],
stepNumber: 0,
model: {},
messages: [{ role: 'user', content: 'q' }],
});
expect(step0.messages?.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);

// Continuation step: the marker rides the NEW last message, and only it —
// earlier messages (including the prior tail) carry no marker.
const stepN = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'searching' },
{ role: 'assistant', content: 'tool output' },
],
});
const out = stepN.messages!;
expect(out[0].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out[1].providerOptions?.anthropic?.cacheControl).toBeUndefined();
expect(out.at(-1)?.providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
});

test('prepareStep adds no tail marker for non-Anthropic providers', async () => {
// Force MCP so prepareStep exists even without a tail marker.
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { prepareStep } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: noopStrategy,
});
expect(prepareStep).toBeTypeOf('function');

const result = await prepareStep!({
steps: [],
stepNumber: 1,
model: {},
messages: [
{ role: 'user', content: 'q' },
{ role: 'assistant', content: 'a' },
],
});

// activeTools still managed (MCP), but no message override / marker.
expect(result.messages).toBeUndefined();
expect(result.activeTools).toContain('tool_request_activation');
});

test('leaves the dynamic system block uncached', async () => {
const { system } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/repo'],
});

// Static checkpoint + dynamic (per-conversation) block.
expect(system).toHaveLength(2);
expect(system[0].providerOptions?.anthropic?.cacheControl).toEqual(EPHEMERAL);
expect(system[1].providerOptions).toBeUndefined();
expect(system[1].content).toContain('<selected_repositories>');
});

test('does not mark the tools block, so mid-run activeTools growth never busts it', async () => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
});

// The static checkpoint sits on the system block (after the full tools
// section in render order), so no tool definition carries a breakpoint.
for (const tool of Object.values(tools)) {
expect(tool.providerOptions?.anthropic?.cacheControl).toBeUndefined();
}
});

test.each([
['non-Anthropic provider', () => getPromptCacheStrategy('openai', true)],
['caching disabled', () => getPromptCacheStrategy('anthropic', false)],
])('emits no cache markers for %s (multi-provider regression guard)', async (_label, makeStrategy) => {
const { buildMcpToolRegistry } = await import('@/ee/features/chat/mcp/mcpToolRegistry');
vi.mocked(buildMcpToolRegistry).mockReturnValueOnce([
{ name: 'mcp_linear__save_issue', description: 'Save an issue', serverName: 'linear' },
]);

const { system, messages, tools } = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: makeStrategy(),
selectedRepos: ['github.com/acme/repo'],
});

for (const block of system) {
expect(block.providerOptions).toBeUndefined();
}
for (const message of messages) {
expect(message.providerOptions).toBeUndefined();
}
for (const tool of Object.values(tools)) {
expect(tool.providerOptions).toBeUndefined();
}
});

test('builds a byte-identical static prompt regardless of repos', async () => {
const first = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/one'],
});
const second = await runCreateMessageStream([createUserMessage()], {
promptCacheStrategy: anthropicStrategy,
selectedRepos: ['github.com/acme/two', 'github.com/acme/three'],
});

expect(first.system[0].content).toBe(second.system[0].content);
});
});
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