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Add before/after session events with cancellation support

Browse source 
- Merge branch event into session with before_branch/branch reasons
- Add before_switch, before_clear, shutdown reasons
- before_* events can be cancelled with { cancel: true }
- Update RPC commands to return cancelled status
- Add shutdown event on process exit
- New example hooks: confirm-destructive, dirty-repo-guard, auto-commit-on-exit

fixes #278
This commit is contained in:
Mario Zechner 2025-12-22 18:18:38 +01:00
parent 99081fce30
commit 42d7d9d9b6
20 changed files with 426 additions and 124 deletions
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6
packages/ai/src/models.generated.ts
View file

@ -3223,9 +3223,9 @@ export const MODELS = {
reasoning: true,
input: ["text"],
cost: {
input: 0.24,
output: 0.38,
cacheRead: 0.02,
input: 0.23900000000000002,
output: 0.378,
cacheRead: 0.11,
cacheWrite: 0,
},
contextWindow: 163840,

8
packages/coding-agent/CHANGELOG.md
View file

@ -2,6 +2,14 @@
## [Unreleased]
### Breaking
- **Session hooks API redesign**: Merged `branch` event into `session` event. `BranchEvent`, `BranchEventResult` types and `pi.on("branch", ...)` removed. Use `pi.on("session", ...)` with `reason: "before_branch" | "branch"` instead. `AgentSession.branch()` returns `{ cancelled }` instead of `{ skipped }`. `AgentSession.reset()` and `switchSession()` now return `boolean` (false if cancelled by hook). RPC commands `reset`, `switch_session`, and `branch` now include `cancelled` in response data. ([#278](https://github.com/badlogic/pi-mono/issues/278))
### Added
- **Session lifecycle hooks**: Added `before_*` variants (`before_switch`, `before_clear`, `before_branch`) that fire before actions and can be cancelled with `{ cancel: true }`. Added `shutdown` reason for graceful exit handling. ([#278](https://github.com/badlogic/pi-mono/issues/278))
### Fixed
- **File tab completion display**: File paths no longer get cut off early. Folders now show trailing `/` and removed redundant "directory"/"file" labels to maximize horizontal space. ([#280](https://github.com/badlogic/pi-mono/issues/280))

70
packages/coding-agent/docs/hooks.md
View file

@ -117,51 +117,55 @@ user sends another prompt ◄─────────────────
user branches (/branch)
│
├─► branch (BEFORE branch, can control)
└─► session (reason: "switch", AFTER branch)
├─► session (reason: "before_branch", can cancel)
└─► session (reason: "branch", AFTER branch)
user switches session (/session)
│
└─► session (reason: "switch")
├─► session (reason: "before_switch", can cancel)
└─► session (reason: "switch", AFTER switch)
user clears session (/clear)
│
└─► session (reason: "clear")
├─► session (reason: "before_clear", can cancel)
└─► session (reason: "clear", AFTER clear)
user exits (double Ctrl+C or Ctrl+D)
│
└─► session (reason: "shutdown")
```
A **turn** is one LLM response plus any tool calls. Complex tasks loop through multiple turns until the LLM responds without calling tools.
### session
Fired on startup and when session changes.
Fired on session lifecycle events. The `before_*` variants fire before the action and can be cancelled by returning `{ cancel: true }`.
```typescript
pi.on("session", async (event, ctx) => {
// event.entries: SessionEntry[] - all session entries
// event.sessionFile: string | null - current session file (null with --no-session)
// event.previousSessionFile: string | null - previous session file
// event.reason: "start" | "switch" | "clear"
// event.reason: "start" | "before_switch" | "switch" | "before_clear" | "clear" |
// "before_branch" | "branch" | "shutdown"
// event.targetTurnIndex: number - only for "before_branch" and "branch"
// Cancel a before_* action:
if (event.reason === "before_clear") {
return { cancel: true };
}
// No return needed if not cancelling
});
```
**Reasons:**
- `start`: Initial session load on startup
- `switch`: User switched sessions (`/session`) or branched (`/branch`)
- `clear`: User cleared the session (`/clear`)
- `before_switch` / `switch`: User switched sessions (`/session`)
- `before_clear` / `clear`: User cleared the session (`/clear`)
- `before_branch` / `branch`: User branched the session (`/branch`)
- `shutdown`: Process is exiting (double Ctrl+C, Ctrl+D, or SIGTERM)
### branch
Fired BEFORE a branch happens. Can control branch behavior.
```typescript
pi.on("branch", async (event, ctx) => {
// event.targetTurnIndex: number
// event.entries: SessionEntry[]
return { skipConversationRestore: true }; // or undefined
});
```
Note: After branch completes, a `session` event fires with `reason: "switch"`.
For `before_branch` and `branch` events, `event.targetTurnIndex` contains the entry index being branched from.
### agent_start / agent_end
@ -544,9 +548,12 @@ export default function (pi: HookAPI) {
}
});
pi.on("branch", async (event, ctx) => {
pi.on("session", async (event, ctx) => {
// Only handle before_branch events
if (event.reason !== "before_branch") return;
const ref = checkpoints.get(event.targetTurnIndex);
if (!ref) return undefined;
if (!ref) return;
const choice = await ctx.ui.select("Restore code state?", [
"Yes, restore code to that point",
@ -557,8 +564,6 @@ export default function (pi: HookAPI) {
await ctx.exec("git", ["stash", "apply", ref]);
ctx.ui.notify("Code restored to checkpoint", "info");
}
return undefined;
});
pi.on("agent_end", async () => {
@ -712,17 +717,26 @@ User sends prompt:
Branch:
-> AgentSession.branch()
-> hookRunner.emit({ type: "branch", ... }) # BEFORE branch
-> [branch happens]
-> hookRunner.emit({ type: "session", reason: "switch", ... }) # AFTER
-> hookRunner.emit({ type: "session", reason: "before_branch", ... }) # can cancel
-> [if not cancelled: branch happens]
-> hookRunner.emit({ type: "session", reason: "branch", ... })
Session switch:
-> AgentSession.switchSession()
-> hookRunner.emit({ type: "session", reason: "before_switch", ... }) # can cancel
-> [if not cancelled: switch happens]
-> hookRunner.emit({ type: "session", reason: "switch", ... })
Clear:
-> AgentSession.reset()
-> hookRunner.emit({ type: "session", reason: "before_clear", ... }) # can cancel
-> [if not cancelled: clear happens]
-> hookRunner.emit({ type: "session", reason: "clear", ... })
Shutdown (interactive mode):
-> handleCtrlC() or handleCtrlD()
-> hookRunner.emit({ type: "session", reason: "shutdown", ... })
-> process.exit(0)
```
## UI Context by Mode

32
packages/coding-agent/docs/rpc.md
View file

@ -78,7 +78,7 @@ Response:
#### reset
Clear context and start a fresh session.
Clear context and start a fresh session. Can be cancelled by a `before_clear` hook.
```json
{"type": "reset"}
@ -86,7 +86,12 @@ Clear context and start a fresh session.
Response:
```json
{"type": "response", "command": "reset", "success": true}
{"type": "response", "command": "reset", "success": true, "data": {"cancelled": false}}
```
If a hook cancelled the reset:
```json
{"type": "response", "command": "reset", "success": true, "data": {"cancelled": true}}
```
### State
@ -465,7 +470,7 @@ Response:
#### switch_session
Load a different session file.
Load a different session file. Can be cancelled by a `before_switch` hook.
```json
{"type": "switch_session", "sessionPath": "/path/to/session.jsonl"}
@ -473,12 +478,17 @@ Load a different session file.
Response:
```json
{"type": "response", "command": "switch_session", "success": true}
{"type": "response", "command": "switch_session", "success": true, "data": {"cancelled": false}}
```
If a hook cancelled the switch:
```json
{"type": "response", "command": "switch_session", "success": true, "data": {"cancelled": true}}
```
#### branch
Create a new branch from a previous user message. Returns the text of the message being branched from.
Create a new branch from a previous user message. Can be cancelled by a `before_branch` hook. Returns the text of the message being branched from.
```json
{"type": "branch", "entryIndex": 2}
@ -490,7 +500,17 @@ Response:
"type": "response",
"command": "branch",
"success": true,
"data": {"text": "The original prompt text..."}
"data": {"text": "The original prompt text...", "cancelled": false}
}
```
If a hook cancelled the branch:
```json
{
"type": "response",
"command": "branch",
"success": true,
"data": {"text": "The original prompt text...", "cancelled": true}
}
```

22
packages/coding-agent/examples/hooks/README.md
View file

@ -16,6 +16,15 @@ Blocks writes to protected paths (.env, .git/, node_modules/).
### file-trigger.ts
Watches a trigger file and injects its contents into the conversation. Useful for external systems (CI, file watchers, webhooks) to send messages to the agent.
### confirm-destructive.ts
Prompts for confirmation before destructive session actions (clear, switch, branch). Demonstrates how to cancel `before_*` session events.
### dirty-repo-guard.ts
Prevents session changes when there are uncommitted git changes. Blocks clear/switch/branch until you commit.
### auto-commit-on-exit.ts
Automatically commits changes when the agent exits (shutdown event). Uses the last assistant message to generate a commit message.
## Usage
```bash
@ -38,8 +47,16 @@ import type { HookAPI } from "@mariozechner/pi-coding-agent/hooks";
export default function (pi: HookAPI) {
pi.on("session", async (event, ctx) => {
// event.reason: "start" | "switch" | "clear"
// event.reason: "start" | "before_switch" | "switch" | "before_clear" | "clear" |
// "before_branch" | "branch" | "shutdown"
// event.targetTurnIndex: number (only for before_branch/branch)
// ctx.ui, ctx.exec, ctx.cwd, ctx.sessionFile, ctx.hasUI
// Cancel before_* actions:
if (event.reason === "before_clear") {
return { cancel: true };
}
return undefined;
});
pi.on("tool_call", async (event, ctx) => {
@ -58,8 +75,7 @@ export default function (pi: HookAPI) {
```
**Available events:**
- `session` - startup, session switch, clear
- `branch` - before branching (can skip conversation restore)
- `session` - lifecycle events with before/after variants (can cancel before_* actions)
- `agent_start` / `agent_end` - per user prompt
- `turn_start` / `turn_end` - per LLM turn
- `tool_call` - before tool execution (can block)

50
packages/coding-agent/examples/hooks/auto-commit-on-exit.ts Normal file
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@ -0,0 +1,50 @@
/**
* Auto-Commit on Exit Hook
*
* Automatically commits changes when the agent exits.
* Uses the last assistant message to generate a commit message.
*/
import type { HookAPI } from "@mariozechner/pi-coding-agent/hooks";
export default function (pi: HookAPI) {
pi.on("session", async (event, ctx) => {
if (event.reason !== "shutdown") return;
// Check for uncommitted changes
const { stdout: status, code } = await ctx.exec("git", ["status", "--porcelain"]);
if (code !== 0 || status.trim().length === 0) {
// Not a git repo or no changes
return;
}
// Find the last assistant message for commit context
let lastAssistantText = "";
for (let i = event.entries.length - 1; i >= 0; i--) {
const entry = event.entries[i];
if (entry.type === "message" && entry.message.role === "assistant") {
const content = entry.message.content;
if (Array.isArray(content)) {
lastAssistantText = content
.filter((c): c is { type: "text"; text: string } => c.type === "text")
.map((c) => c.text)
.join("\n");
}
break;
}
}
// Generate a simple commit message
const firstLine = lastAssistantText.split("\n")[0] || "Work in progress";
const commitMessage = `[pi] ${firstLine.slice(0, 50)}${firstLine.length > 50 ? "..." : ""}`;
// Stage and commit
await ctx.exec("git", ["add", "-A"]);
const { code: commitCode } = await ctx.exec("git", ["commit", "-m", commitMessage]);
if (commitCode === 0 && ctx.hasUI) {
ctx.ui.notify(`Auto-committed: ${commitMessage}`, "info");
}
});
}

62
packages/coding-agent/examples/hooks/confirm-destructive.ts Normal file
View file

@ -0,0 +1,62 @@
/**
* Confirm Destructive Actions Hook
*
* Prompts for confirmation before destructive session actions (clear, switch, branch).
* Demonstrates how to cancel session events using the before_* variants.
*/
import type { HookAPI } from "@mariozechner/pi-coding-agent/hooks";
export default function (pi: HookAPI) {
pi.on("session", async (event, ctx) => {
// Only handle before_* events (the ones that can be cancelled)
if (event.reason === "before_clear") {
if (!ctx.hasUI) return;
const confirmed = await ctx.ui.confirm(
"Clear session?",
"This will delete all messages in the current session.",
);
if (!confirmed) {
ctx.ui.notify("Clear cancelled", "info");
return { cancel: true };
}
}
if (event.reason === "before_switch") {
if (!ctx.hasUI) return;
// Check if there are unsaved changes (messages since last assistant response)
const hasUnsavedWork = event.entries.some(
(e) => e.type === "message" && e.message.role === "user",
);
if (hasUnsavedWork) {
const confirmed = await ctx.ui.confirm(
"Switch session?",
"You have messages in the current session. Switch anyway?",
);
if (!confirmed) {
ctx.ui.notify("Switch cancelled", "info");
return { cancel: true };
}
}
}
if (event.reason === "before_branch") {
if (!ctx.hasUI) return;
const choice = await ctx.ui.select(
`Branch from turn ${event.targetTurnIndex}?`,
["Yes, create branch", "No, stay in current session"],
);
if (choice !== "Yes, create branch") {
ctx.ui.notify("Branch cancelled", "info");
return { cancel: true };
}
}
});
}

59
packages/coding-agent/examples/hooks/dirty-repo-guard.ts Normal file
View file

@ -0,0 +1,59 @@
/**
* Dirty Repo Guard Hook
*
* Prevents session changes when there are uncommitted git changes.
* Useful to ensure work is committed before switching context.
*/
import type { HookAPI } from "@mariozechner/pi-coding-agent/hooks";
export default function (pi: HookAPI) {
pi.on("session", async (event, ctx) => {
// Only guard destructive actions
if (
event.reason !== "before_clear" &&
event.reason !== "before_switch" &&
event.reason !== "before_branch"
) {
return;
}
// Check for uncommitted changes
const { stdout, code } = await ctx.exec("git", ["status", "--porcelain"]);
if (code !== 0) {
// Not a git repo, allow the action
return;
}
const hasChanges = stdout.trim().length > 0;
if (!hasChanges) {
return;
}
if (!ctx.hasUI) {
// In non-interactive mode, block by default
return { cancel: true };
}
// Count changed files
const changedFiles = stdout.trim().split("\n").filter(Boolean).length;
const action =
event.reason === "before_clear"
? "clear session"
: event.reason === "before_switch"
? "switch session"
: "branch";
const choice = await ctx.ui.select(
`You have ${changedFiles} uncommitted file(s). ${action} anyway?`,
["Yes, proceed anyway", "No, let me commit first"],
);
if (choice !== "Yes, proceed anyway") {
ctx.ui.notify("Commit your changes first", "warning");
return { cancel: true };
}
});
}

11
packages/coding-agent/examples/hooks/git-checkpoint.ts
View file

@ -19,13 +19,16 @@ export default function (pi: HookAPI) {
}
});
pi.on("branch", async (event, ctx) => {
pi.on("session", async (event, ctx) => {
// Only handle before_branch events
if (event.reason !== "before_branch") return;
const ref = checkpoints.get(event.targetTurnIndex);
if (!ref) return undefined;
if (!ref) return;
if (!ctx.hasUI) {
// In non-interactive mode, don't restore automatically
return undefined;
return;
}
const choice = await ctx.ui.select("Restore code state?", [
@ -37,8 +40,6 @@ export default function (pi: HookAPI) {
await ctx.exec("git", ["stash", "apply", ref]);
ctx.ui.notify("Code restored to checkpoint", "info");
}
return undefined;
});
pi.on("agent_end", async () => {

78
packages/coding-agent/src/core/agent-session.ts
View file

@ -21,7 +21,7 @@ import { type BashResult, executeBash as executeBashCommand } from "./bash-execu
import { calculateContextTokens, compact, shouldCompact } from "./compaction.js";
import type { LoadedCustomTool, SessionEvent as ToolSessionEvent } from "./custom-tools/index.js";
import { exportSessionToHtml } from "./export-html.js";
import type { BranchEventResult, HookRunner, TurnEndEvent, TurnStartEvent } from "./hooks/index.js";
import type { HookRunner, SessionEventResult, TurnEndEvent, TurnStartEvent } from "./hooks/index.js";
import type { BashExecutionMessage } from "./messages.js";
import { getApiKeyForModel, getAvailableModels } from "./model-config.js";
import { loadSessionFromEntries, type SessionManager } from "./session-manager.js";
@ -501,9 +501,26 @@ export class AgentSession {
* Reset agent and session to start fresh.
* Clears all messages and starts a new session.
* Listeners are preserved and will continue receiving events.
* @returns true if reset completed, false if cancelled by hook
*/
async reset(): Promise<void> {
async reset(): Promise<boolean> {
const previousSessionFile = this.sessionFile;
const entries = this.sessionManager.loadEntries();
// Emit before_clear event (can be cancelled)
if (this._hookRunner?.hasHandlers("session")) {
const result = (await this._hookRunner.emit({
type: "session",
entries,
sessionFile: this.sessionFile,
previousSessionFile: null,
reason: "before_clear",
})) as SessionEventResult | undefined;
if (result?.cancel) {
return false;
}
}
this._disconnectFromAgent();
await this.abort();
@ -526,6 +543,7 @@ export class AgentSession {
// Emit session event to custom tools
await this._emitToolSessionEvent("clear", previousSessionFile);
return true;
}
// =========================================================================
@ -1142,9 +1160,26 @@ export class AgentSession {
* Switch to a different session file.
* Aborts current operation, loads messages, restores model/thinking.
* Listeners are preserved and will continue receiving events.
* @returns true if switch completed, false if cancelled by hook
*/
async switchSession(sessionPath: string): Promise<void> {
async switchSession(sessionPath: string): Promise<boolean> {
const previousSessionFile = this.sessionFile;
const oldEntries = this.sessionManager.loadEntries();
// Emit before_switch event (can be cancelled)
if (this._hookRunner?.hasHandlers("session")) {
const result = (await this._hookRunner.emit({
type: "session",
entries: oldEntries,
sessionFile: this.sessionFile,
previousSessionFile: null,
reason: "before_switch",
})) as SessionEventResult | undefined;
if (result?.cancel) {
return false;
}
}
this._disconnectFromAgent();
await this.abort();
@ -1191,18 +1226,19 @@ export class AgentSession {
}
this._reconnectToAgent();
return true;
}
/**
* Create a branch from a specific entry index.
* Emits branch event to hooks, which can control the branch behavior.
* Emits before_branch/branch session events to hooks.
*
* @param entryIndex Index into session entries to branch from
* @returns Object with:
* - selectedText: The text of the selected user message (for editor pre-fill)
* - skipped: True if a hook requested to skip conversation restore
* - cancelled: True if a hook cancelled the branch
*/
async branch(entryIndex: number): Promise<{ selectedText: string; skipped: boolean }> {
async branch(entryIndex: number): Promise<{ selectedText: string; cancelled: boolean }> {
const previousSessionFile = this.sessionFile;
const entries = this.sessionManager.loadEntries();
const selectedEntry = entries[entryIndex];
@ -1213,19 +1249,20 @@ export class AgentSession {
const selectedText = this._extractUserMessageText(selectedEntry.message.content);
// Emit branch event to hooks
let hookResult: BranchEventResult | undefined;
if (this._hookRunner?.hasHandlers("branch")) {
hookResult = (await this._hookRunner.emit({
type: "branch",
targetTurnIndex: entryIndex,
// Emit before_branch event (can be cancelled)
if (this._hookRunner?.hasHandlers("session")) {
const result = (await this._hookRunner.emit({
type: "session",
entries,
})) as BranchEventResult | undefined;
}
sessionFile: this.sessionFile,
previousSessionFile: null,
reason: "before_branch",
targetTurnIndex: entryIndex,
})) as SessionEventResult | undefined;
// If hook says skip conversation restore, don't branch
if (hookResult?.skipConversationRestore) {
return { selectedText, skipped: true };
if (result?.cancel) {
return { selectedText, cancelled: true };
}
}
// Create branched session (returns null in --no-session mode)
@ -1240,7 +1277,7 @@ export class AgentSession {
const newEntries = this.sessionManager.loadEntries();
const loaded = loadSessionFromEntries(newEntries);
// Emit session event to hooks (in --no-session mode, both files are null)
// Emit branch event to hooks (after branch completes)
if (this._hookRunner) {
this._hookRunner.setSessionFile(newSessionFile);
await this._hookRunner.emit({
@ -1248,7 +1285,8 @@ export class AgentSession {
entries: newEntries,
sessionFile: newSessionFile,
previousSessionFile,
reason: "switch",
reason: "branch",
targetTurnIndex: entryIndex,
});
}
@ -1257,7 +1295,7 @@ export class AgentSession {
this.agent.replaceMessages(loaded.messages);
return { selectedText, skipped: false };
return { selectedText, cancelled: false };
}
/**

3
packages/coding-agent/src/core/hooks/index.ts
View file

@ -5,8 +5,6 @@ export type {
AgentEndEvent,
AgentStartEvent,
BashToolResultEvent,
BranchEvent,
BranchEventResult,
CustomToolResultEvent,
EditToolResultEvent,
ExecResult,
@ -21,6 +19,7 @@ export type {
LsToolResultEvent,
ReadToolResultEvent,
SessionEvent,
SessionEventResult,
ToolCallEvent,
ToolCallEventResult,
ToolResultEvent,

18
packages/coding-agent/src/core/hooks/runner.ts
View file

@ -5,13 +5,13 @@
import { spawn } from "node:child_process";
import type { LoadedHook, SendHandler } from "./loader.js";
import type {
BranchEventResult,
ExecOptions,
ExecResult,
HookError,
HookEvent,
HookEventContext,
HookUIContext,
SessionEventResult,
ToolCallEvent,
ToolCallEventResult,
ToolResultEventResult,
@ -217,11 +217,11 @@ export class HookRunner {
/**
* Emit an event to all hooks.
* Returns the result from branch/tool_result events (if any handler returns one).
* Returns the result from session/tool_result events (if any handler returns one).
*/
async emit(event: HookEvent): Promise<BranchEventResult | ToolResultEventResult | undefined> {
async emit(event: HookEvent): Promise<SessionEventResult | ToolResultEventResult | undefined> {
const ctx = this.createContext();
let result: BranchEventResult | ToolResultEventResult | undefined;
let result: SessionEventResult | ToolResultEventResult | undefined;
for (const hook of this.hooks) {
const handlers = hook.handlers.get(event.type);
@ -233,9 +233,13 @@ export class HookRunner {
const handlerResult = await Promise.race([handler(event, ctx), timeout.promise]);
timeout.clear();
// For branch events, capture the result
if (event.type === "branch" && handlerResult) {
result = handlerResult as BranchEventResult;
// For session events, capture the result (for before_* cancellation)
if (event.type === "session" && handlerResult) {
result = handlerResult as SessionEventResult;
// If cancelled, stop processing further hooks
if (result.cancel) {
return result;
}
}
// For tool_result events, capture the result

60
packages/coding-agent/src/core/hooks/types.ts
View file

@ -90,11 +90,9 @@ export interface HookEventContext {
// ============================================================================
/**
* Event data for session event.
* Fired on startup and when session changes (switch or clear).
* Note: branch has its own event that fires BEFORE the branch happens.
* Base fields shared by all session events.
*/
export interface SessionEvent {
interface SessionEventBase {
type: "session";
/** All session entries (including pre-compaction history) */
entries: SessionEntry[];
@ -102,10 +100,32 @@ export interface SessionEvent {
sessionFile: string | null;
/** Previous session file path, or null for "start" and "clear" */
previousSessionFile: string | null;
/** Reason for the session event */
reason: "start" | "switch" | "clear";
}
/**
* Event data for session events.
* Discriminated union based on reason.
*
* Lifecycle:
* - start: Initial session load
* - before_switch / switch: Session switch (e.g., /session command)
* - before_clear / clear: Session clear (e.g., /clear command)
* - before_branch / branch: Session branch (e.g., /branch command)
* - shutdown: Process exit (SIGINT/SIGTERM)
*
* "before_*" events fire before the action and can be cancelled via SessionEventResult.
* Other events fire after the action completes.
*/
export type SessionEvent =
| (SessionEventBase & {
reason: "start" | "switch" | "clear" | "before_switch" | "before_clear" | "shutdown";
})
| (SessionEventBase & {
reason: "branch" | "before_branch";
/** Index of the turn to branch from */
targetTurnIndex: number;
});
/**
* Event data for agent_start event.
* Fired when an agent loop starts (once per user prompt).
@ -256,17 +276,6 @@ export function isLsToolResult(e: ToolResultEvent): e is LsToolResultEvent {
return e.toolName === "ls";
}
/**
* Event data for branch event.
*/
export interface BranchEvent {
type: "branch";
/** Index of the turn to branch from */
targetTurnIndex: number;
/** Full session history */
entries: SessionEntry[];
}
/**
* Union of all hook event types.
*/
@ -277,8 +286,7 @@ export type HookEvent =
| TurnStartEvent
| TurnEndEvent
| ToolCallEvent
| ToolResultEvent
| BranchEvent;
| ToolResultEvent;
// ============================================================================
// Event Results
@ -309,12 +317,12 @@ export interface ToolResultEventResult {
}
/**
* Return type for branch event handlers.
* Allows hooks to control branch behavior.
* Return type for session event handlers.
* Allows hooks to cancel "before_*" actions.
*/
export interface BranchEventResult {
/** If true, skip restoring the conversation (only restore code) */
skipConversationRestore?: boolean;
export interface SessionEventResult {
/** If true, cancel the pending action (switch, clear, or branch) */
cancel?: boolean;
}
// ============================================================================
@ -331,14 +339,14 @@ export type HookHandler<E, R = void> = (event: E, ctx: HookEventContext) => Prom
* Hooks use pi.on() to subscribe to events and pi.send() to inject messages.
*/
export interface HookAPI {
on(event: "session", handler: HookHandler<SessionEvent>): void;
// biome-ignore lint/suspicious/noConfusingVoidType: void allows handlers to not return anything
on(event: "session", handler: HookHandler<SessionEvent, SessionEventResult | void>): void;
on(event: "agent_start", handler: HookHandler<AgentStartEvent>): void;
on(event: "agent_end", handler: HookHandler<AgentEndEvent>): void;
on(event: "turn_start", handler: HookHandler<TurnStartEvent>): void;
on(event: "turn_end", handler: HookHandler<TurnEndEvent>): void;
on(event: "tool_call", handler: HookHandler<ToolCallEvent, ToolCallEventResult | undefined>): void;
on(event: "tool_result", handler: HookHandler<ToolResultEvent, ToolResultEventResult | undefined>): void;
on(event: "branch", handler: HookHandler<BranchEvent, BranchEventResult | undefined>): void;
/**
* Send a message to the agent.

2
packages/coding-agent/src/core/system-prompt.ts
View file

@ -242,7 +242,7 @@ export function buildSystemPrompt(options: BuildSystemPromptOptions = {}): strin
// Read before edit guideline
if (hasRead && hasEdit) {
guidelinesList.push("Use read to examine files before editing");
guidelinesList.push("Use read to examine files before editing. You must use this tool instead of cat or sed.");
}
// Edit guideline

3
packages/coding-agent/src/index.ts
View file

@ -40,8 +40,6 @@ export type {
AgentEndEvent,
AgentStartEvent,
BashToolResultEvent,
BranchEvent,
BranchEventResult,
CustomToolResultEvent,
EditToolResultEvent,
FindToolResultEvent,
@ -54,6 +52,7 @@ export type {
LsToolResultEvent,
ReadToolResultEvent,
SessionEvent,
SessionEventResult,
ToolCallEvent,
ToolCallEventResult,
ToolResultEvent,

31
packages/coding-agent/src/modes/interactive/interactive-mode.ts
View file

@ -1162,8 +1162,7 @@ export class InteractiveMode {
private handleCtrlC(): void {
const now = Date.now();
if (now - this.lastSigintTime < 500) {
this.stop();
process.exit(0);
void this.shutdown();
} else {
this.clearEditor();
this.lastSigintTime = now;
@ -1172,6 +1171,27 @@ export class InteractiveMode {
private handleCtrlD(): void {
// Only called when editor is empty (enforced by CustomEditor)
void this.shutdown();
}
/**
* Gracefully shutdown the agent.
* Emits shutdown event to hooks, then exits.
*/
private async shutdown(): Promise<void> {
// Emit shutdown event to hooks
const hookRunner = this.session.hookRunner;
if (hookRunner?.hasHandlers("session")) {
const entries = this.sessionManager.loadEntries();
await hookRunner.emit({
type: "session",
entries,
sessionFile: this.session.sessionFile,
previousSessionFile: null,
reason: "shutdown",
});
}
this.stop();
process.exit(0);
}
@ -1496,8 +1516,8 @@ export class InteractiveMode {
userMessages.map((m) => ({ index: m.entryIndex, text: m.text })),
async (entryIndex) => {
const result = await this.session.branch(entryIndex);
if (result.skipped) {
// Hook requested to skip conversation restore
if (result.cancelled) {
// Hook cancelled the branch
done();
this.ui.requestRender();
return;
@ -1533,8 +1553,7 @@ export class InteractiveMode {
this.ui.requestRender();
},
() => {
this.stop();
process.exit(0);
void this.shutdown();
},
);
return { component: selector, focus: selector.getSessionList() };

15
packages/coding-agent/src/modes/rpc/rpc-client.ts
View file

@ -186,9 +186,11 @@ export class RpcClient {
/**
* Reset session (clear all messages).
* @returns Object with `cancelled: true` if a hook cancelled the reset
*/
async reset(): Promise<void> {
await this.send({ type: "reset" });
async reset(): Promise<{ cancelled: boolean }> {
const response = await this.send({ type: "reset" });
return this.getData(response);
}
/**
@ -311,15 +313,18 @@ export class RpcClient {
/**
* Switch to a different session file.
* @returns Object with `cancelled: true` if a hook cancelled the switch
*/
async switchSession(sessionPath: string): Promise<void> {
await this.send({ type: "switch_session", sessionPath });
async switchSession(sessionPath: string): Promise<{ cancelled: boolean }> {
const response = await this.send({ type: "switch_session", sessionPath });
return this.getData(response);
}
/**
* Branch from a specific message.
* @returns Object with `text` (the message text) and `cancelled` (if hook cancelled)
*/
async branch(entryIndex: number): Promise<{ text: string }> {
async branch(entryIndex: number): Promise<{ text: string; cancelled: boolean }> {
const response = await this.send({ type: "branch", entryIndex });
return this.getData(response);
}

10
packages/coding-agent/src/modes/rpc/rpc-mode.ts
View file

@ -205,8 +205,8 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
}
case "reset": {
await session.reset();
return success(id, "reset");
const cancelled = !(await session.reset());
return success(id, "reset", { cancelled });
}
// =================================================================
@ -339,13 +339,13 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
}
case "switch_session": {
await session.switchSession(command.sessionPath);
return success(id, "switch_session");
const cancelled = !(await session.switchSession(command.sessionPath));
return success(id, "switch_session", { cancelled });
}
case "branch": {
const result = await session.branch(command.entryIndex);
return success(id, "branch", { text: result.selectedText, skipped: result.skipped });
return success(id, "branch", { text: result.selectedText, cancelled: result.cancelled });
}
case "get_branch_messages": {

6
packages/coding-agent/src/modes/rpc/rpc-types.ts
View file

@ -86,7 +86,7 @@ export type RpcResponse =
| { id?: string; type: "response"; command: "prompt"; success: true }
| { id?: string; type: "response"; command: "queue_message"; success: true }
| { id?: string; type: "response"; command: "abort"; success: true }
| { id?: string; type: "response"; command: "reset"; success: true }
| { id?: string; type: "response"; command: "reset"; success: true; data: { cancelled: boolean } }
// State
| { id?: string; type: "response"; command: "get_state"; success: true; data: RpcSessionState }
@ -142,8 +142,8 @@ export type RpcResponse =
// Session
| { id?: string; type: "response"; command: "get_session_stats"; success: true; data: SessionStats }
| { id?: string; type: "response"; command: "export_html"; success: true; data: { path: string } }
| { id?: string; type: "response"; command: "switch_session"; success: true }
| { id?: string; type: "response"; command: "branch"; success: true; data: { text: string } }
| { id?: string; type: "response"; command: "switch_session"; success: true; data: { cancelled: boolean } }
| { id?: string; type: "response"; command: "branch"; success: true; data: { text: string; cancelled: boolean } }
| {
id?: string;
type: "response";

4
packages/coding-agent/test/agent-session-branching.test.ts
View file

@ -86,7 +86,7 @@ describe.skipIf(!API_KEY)("AgentSession branching", () => {
// Branch from the first message
const result = await session.branch(userMessages[0].entryIndex);
expect(result.selectedText).toBe("Say hello");
expect(result.skipped).toBe(false);
expect(result.cancelled).toBe(false);
// After branching, conversation should be empty (branched before the first message)
expect(session.messages.length).toBe(0);
@ -116,7 +116,7 @@ describe.skipIf(!API_KEY)("AgentSession branching", () => {
// Branch from the first message
const result = await session.branch(userMessages[0].entryIndex);
expect(result.selectedText).toBe("Say hi");
expect(result.skipped).toBe(false);
expect(result.cancelled).toBe(false);
// After branching, conversation should be empty
expect(session.messages.length).toBe(0);