Improve in-flight cancel latency via run abort signal propagation

docs/api/PROTOCOL.md

@@ -700,6 +700,7 @@ Cancel the current agent operation.
 
 Used by the web dashboard/chat stop button and channel-level `/stop` / `/cancel` command fast-paths.
 Cancellation is best-effort and stops at the next agent/tool-loop safe point.
+Flynn now propagates a run-level abort signal into model/tool execution, so providers/tools that honor `AbortSignal` typically stop promptly instead of waiting for request/tool timeouts.
 
 ### Node Methods
 

docs/api/TOOLS.md

@@ -68,6 +68,8 @@ export interface ToolExecutionContext {
 }
 ```
 
+`signal` is wired to run-level cancellation (`agent.cancel`, `/stop`, `/cancel`) and tool timeout. Tools should honor it for fast cooperative aborts.
+
 ### ToolResult
 
 ```typescript

docs/plans/state.json

@@ -3,6 +3,27 @@
   "updated_at": "2026-02-19",
   "description": "Tracks the status of all Flynn plans and implementation phases",
   "plans": {
+    "faster-inflight-cancel-propagation": {
+      "status": "completed",
+      "date": "2026-02-19",
+      "updated": "2026-02-19",
+      "summary": "Reduced cancellation latency by wiring a run-level AbortSignal from NativeAgent into model and tool execution. `agent.cancel`/`/stop` now abort in-flight model/tool awaits immediately for signal-aware providers/tools instead of waiting for timeout/safe-point boundaries.",
+      "files_modified": [
+        "src/backends/native/agent.ts",
+        "src/tools/executor.ts",
+        "src/models/types.ts",
+        "src/models/openai.ts",
+        "src/models/github.ts",
+        "src/models/anthropic.ts",
+        "src/models/bedrock.ts",
+        "src/models/local/llamacpp.ts",
+        "src/backends/native/agent.test.ts",
+        "docs/api/PROTOCOL.md",
+        "docs/api/TOOLS.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/backends/native/agent.test.ts src/tools/executor.test.ts src/models/router.test.ts src/gateway/handlers/agent.test.ts + pnpm typecheck passing"
+    },
     "makefile-skills-convenience-targets": {
       "status": "completed",
       "date": "2026-02-17",

src/backends/native/agent.test.ts

@@ -24,10 +24,11 @@ describe('NativeAgent', () => {
     const response = await agent.process('Hi');
 
     expect(response).toBe('Hello!');
-    expect(mockClient.chat).toHaveBeenCalledWith({
+    expect(mockClient.chat).toHaveBeenCalledWith(expect.objectContaining({
       messages: [{ role: 'user', content: 'Hi' }],
       system: 'You are helpful.',
-    });
+      signal: expect.any(AbortSignal),
+    }));
 
     const history = agent.getHistory();
     expect(history).toHaveLength(2);

src/backends/native/agent.ts

@@ -83,6 +83,7 @@ export class NativeAgent {
   private _lastToolFingerprint?: string;
   private _cancelRequested = false;
   private _runInProgress = false;
+  private _runAbortController?: AbortController;
   private modelTimeoutMs: number;
 
   constructor(config: NativeAgentConfig) {
@@ -106,6 +107,7 @@ export class NativeAgent {
 
   async process(userMessage: string, attachments?: Attachment[]): Promise<string> {
     this._cancelRequested = false;
+    this._runAbortController = new AbortController();
     if ('clearAbort' in this.modelClient && typeof this.modelClient.clearAbort === 'function') {
       this.modelClient.clearAbort();
     }
@@ -144,6 +146,7 @@ export class NativeAgent {
     } finally {
       this._runInProgress = false;
       this._cancelRequested = false;
+      this._runAbortController = undefined;
     }
   }
 
@@ -353,7 +356,9 @@ export class NativeAgent {
             }
             : undefined;
 
-          const result = await toolExecutor.execute(internalName, tc.args, perCallContext);
+          const result = await toolExecutor.execute(internalName, tc.args, perCallContext, {
+            signal: this._runAbortController?.signal,
+          });
 
           this.onToolUse?.({ type: 'end', tool: internalName, result });
 
@@ -426,11 +431,22 @@ export class NativeAgent {
   }
 
   private async chatWithRouter(request: ChatRequest): Promise<ChatResponse> {
+    const runSignal = this._runAbortController?.signal;
+    const requestSignal = request.signal;
+    const signal = runSignal && requestSignal
+      ? AbortSignal.any([runSignal, requestSignal])
+      : (runSignal ?? requestSignal);
+
+    const requestWithSignal = signal
+      ? { ...request, signal }
+      : request;
+
     const requestPromise = 'getClient' in this.modelClient
-      ? (this.modelClient as ModelRouter).chat(request, this.currentTier)
+      ? (this.modelClient as ModelRouter).chat(requestWithSignal, this.currentTier)
-      : this.modelClient.chat(request);
+      : this.modelClient.chat(requestWithSignal);
 
     let timer: NodeJS.Timeout | undefined;
+    let abortCleanup: (() => void) | undefined;
     const timeoutPromise = new Promise<never>((_, reject) => {
       timer = setTimeout(() => {
         const error = new Error(`Model request timed out after ${this.modelTimeoutMs}ms`);
@@ -439,13 +455,31 @@ export class NativeAgent {
       }, this.modelTimeoutMs);
       timer.unref?.();
     });
+    const abortPromise = signal
+      ? new Promise<never>((_, reject) => {
+        if (signal.aborted) {
+          const error = new Error('Operation cancelled by user.');
+          error.name = 'AbortError';
+          reject(error);
+          return;
+        }
+        const onAbort = () => {
+          const error = new Error('Operation cancelled by user.');
+          error.name = 'AbortError';
+          reject(error);
+        };
+        signal.addEventListener('abort', onAbort, { once: true });
+        abortCleanup = () => signal.removeEventListener('abort', onAbort);
+      })
+      : null;
 
     try {
-      return await Promise.race([requestPromise, timeoutPromise]);
+      return await Promise.race([requestPromise, timeoutPromise, ...(abortPromise ? [abortPromise] : [])]);
     } finally {
       if (timer) {
         clearTimeout(timer);
       }
+      abortCleanup?.();
     }
   }
 
@@ -544,6 +578,7 @@ export class NativeAgent {
   cancel(): void {
     if (this._runInProgress) {
       this._cancelRequested = true;
+      this._runAbortController?.abort();
       if ('requestAbort' in this.modelClient && typeof this.modelClient.requestAbort === 'function') {
         this.modelClient.requestAbort();
       }
@@ -555,7 +590,7 @@ export class NativeAgent {
   }
 
   private throwIfCancelled(): void {
-    if (!this._cancelRequested) {
+    if (!this._cancelRequested && !this._runAbortController?.signal.aborted) {
       return;
     }
 

src/models/anthropic.ts

@@ -100,7 +100,10 @@ export class AnthropicClient implements ModelClient {
       params.thinking = { type: 'enabled', budget_tokens: 4096 };
     }
 
-    const response = await this.client.messages.create(params) as AnthropicMessage;
+    const response = await this.client.messages.create(
+      params,
+      request.signal ? { signal: request.signal } : undefined,
+    ) as AnthropicMessage;
 
     const textContent = response.content.find((c) => c.type === 'text');
     const content = textContent?.type === 'text' ? textContent.text : '';

src/models/bedrock.ts

@@ -65,7 +65,10 @@ export class BedrockClient implements ModelClient {
     }
 
     const command = new ConverseCommand(params);
-    const response = await this.client.send(command);
+    const response = await this.client.send(
+      command,
+      request.signal ? { abortSignal: request.signal } : undefined,
+    );
 
     // Extract text and tool_use content from the response
     const outputContent = response.output?.message?.content ?? [];
@@ -126,7 +129,10 @@ export class BedrockClient implements ModelClient {
 
     try {
       const command = new ConverseStreamCommand(params);
-      const response = await this.client.send(command);
+      const response = await this.client.send(
+        command,
+        request.signal ? { abortSignal: request.signal } : undefined,
+      );
 
       let inputTokens = 0;
       let outputTokens = 0;

src/models/github.ts

@@ -163,7 +163,10 @@ export class GitHubModelsClient implements ModelClient {
       (params as OpenAI.ChatCompletionCreateParamsNonStreaming & { reasoning_effort?: 'low' | 'medium' | 'high' }).reasoning_effort = 'medium';
     }
 
-    const response = await this.client.chat.completions.create(params);
+    const response = await this.client.chat.completions.create(
+      params,
+      request.signal ? { signal: request.signal } : undefined,
+    );
 
     const choice = response.choices[0];
     const content = choice?.message?.content ?? '';
@@ -237,7 +240,10 @@ export class GitHubModelsClient implements ModelClient {
     }
 
     try {
-      const stream = await this.client.chat.completions.create(params);
+      const stream = await this.client.chat.completions.create(
+        params,
+        request.signal ? { signal: request.signal } : undefined,
+      );
 
       let totalInputTokens = 0;
       let totalOutputTokens = 0;

src/models/local/llamacpp.ts

@@ -247,13 +247,16 @@ export class LlamaCppClient implements ModelClient {
       }
 
       const controller = new AbortController();
+      const signal = request.signal
+        ? AbortSignal.any([request.signal, controller.signal])
+        : controller.signal;
       const timer = setTimeout(() => controller.abort(), this.requestTimeout);
       try {
         response = await fetch(`${this.endpoint}/v1/chat/completions`, {
           method: 'POST',
           headers,
           body: JSON.stringify(body),
-          signal: controller.signal,
+          signal,
         });
       } finally {
         clearTimeout(timer);
@@ -331,6 +334,7 @@ export class LlamaCppClient implements ModelClient {
         method: 'POST',
         headers,
         body: JSON.stringify(body),
+        signal: request.signal,
       });
 
       if (!response.ok) {

src/models/openai.ts

@@ -140,6 +140,7 @@ export class OpenAIClient implements ModelClient {
       method: 'POST',
       headers,
       body: JSON.stringify(body),
+      signal: request.signal,
     });
 
     if (!res.ok) {
@@ -277,7 +278,10 @@ export class OpenAIClient implements ModelClient {
 
     let response: OpenAI.ChatCompletion;
     try {
-      response = await this.client.chat.completions.create(params);
+      response = await this.client.chat.completions.create(
+        params,
+        request.signal ? { signal: request.signal } : undefined,
+      );
     } catch (error) {
       const status = typeof (error as { status?: unknown })?.status === 'number'
         ? (error as { status: number }).status

src/models/types.ts

@@ -80,6 +80,8 @@ export interface ChatRequest {
   tools?: ToolDefinition[];
   /** Enable extended thinking/reasoning mode for this request. */
   thinking?: boolean;
+  /** Optional abort signal for cancelling in-flight provider requests. */
+  signal?: AbortSignal;
 }
 
 export interface ChatResponse {

src/tools/executor.ts

@@ -24,6 +24,10 @@ export interface ToolExecutionObserverEvent {
   timestampSeconds: number;
 }
 
+export interface ToolExecuteOptions {
+  signal?: AbortSignal;
+}
+
 export class ToolExecutor {
   private registry: ToolRegistry;
   private hooks: HookEngine;
@@ -64,7 +68,12 @@ export class ToolExecutor {
     return base;
   }
 
-  async execute(toolName: string, args: unknown, context?: ToolPolicyContext): Promise<ToolResult> {
+  async execute(
+    toolName: string,
+    args: unknown,
+    context?: ToolPolicyContext,
+    options?: ToolExecuteOptions,
+  ): Promise<ToolResult> {
     const executionId = randomUUID();
     const executionEnvironment = this.resolveEffectiveExecutionEnvironment(toolName, context);
     const skillName = context?.skillName;
@@ -279,31 +288,56 @@ export class ToolExecutor {
     });
 
     let timeoutHandle: NodeJS.Timeout | undefined;
-    const abortController = new AbortController();
+    const timeoutAbortController = new AbortController();
+    const externalSignal = options?.signal;
+    const combinedSignal = externalSignal
+      ? AbortSignal.any([externalSignal, timeoutAbortController.signal])
+      : timeoutAbortController.signal;
+    let externalAbortCleanup: (() => void) | undefined;
+
     try {
+      const externalAbortPromise = externalSignal
+        ? new Promise<ToolResult>((_, reject) => {
+          if (externalSignal.aborted) {
+            const error = new Error('Operation cancelled by user.');
+            error.name = 'AbortError';
+            reject(error);
+            return;
+          }
+          const onAbort = () => {
+            const error = new Error('Operation cancelled by user.');
+            error.name = 'AbortError';
+            reject(error);
+          };
+          externalSignal.addEventListener('abort', onAbort, { once: true });
+          externalAbortCleanup = () => externalSignal.removeEventListener('abort', onAbort);
+        })
+        : null;
+
       const result = await Promise.race([
         (async () => {
           if (executionEnvironment === 'sandbox' && this.sandboxManager) {
             const sandboxSessionId = context?.sessionId ?? `${context?.channel ?? 'unknown'}:${context?.sender ?? 'unknown'}`;
             const sandbox = await this.sandboxManager.getOrCreate(sandboxSessionId);
             if (toolName === 'shell.exec') {
-              return createSandboxedShellTool(sandbox).execute(args, { signal: abortController.signal });
+              return createSandboxedShellTool(sandbox).execute(args, { signal: combinedSignal });
             }
             if (toolName === 'process.start') {
-              return createSandboxedProcessStartTool(sandbox).execute(args, { signal: abortController.signal });
+              return createSandboxedProcessStartTool(sandbox).execute(args, { signal: combinedSignal });
             }
           }
-          return tool.execute(args, { signal: abortController.signal });
+          return tool.execute(args, { signal: combinedSignal });
         })(),
         new Promise<ToolResult>((_, reject) => {
           timeoutHandle = setTimeout(
             () => {
-              abortController.abort();
+              timeoutAbortController.abort();
               reject(new Error(`Tool '${toolName}' timed out after ${this.defaultTimeoutMs}ms`));
             },
             this.defaultTimeoutMs,
           );
         }),
+        ...(externalAbortPromise ? [externalAbortPromise] : []),
       ]);
 
       const duration = Date.now() - startTime;
@@ -357,6 +391,10 @@ export class ToolExecutor {
         timestampSeconds: Math.floor(Date.now() / 1000),
       });
 
+      if (externalSignal?.aborted && this.isAbortError(error)) {
+        throw error;
+      }
+
       return {
         success: false,
         output: '',
@@ -366,9 +404,14 @@ export class ToolExecutor {
       if (timeoutHandle) {
         clearTimeout(timeoutHandle);
       }
+      externalAbortCleanup?.();
     }
   }
 
+  private isAbortError(error: unknown): boolean {
+    return error instanceof Error && error.name === 'AbortError';
+  }
+
   private notifyExecutionObserver(event: ToolExecutionObserverEvent): void {
     if (!this.executionObserver) {
       return;