agent: event-based project-context reinjection (full/delta)

src/agents/pi-embedded-runner/run.ts

@@ -541,6 +541,9 @@ export async function runEmbeddedPiAgent(
             streamParams: params.streamParams,
             ownerNumbers: params.ownerNumbers,
             enforceFinalTag: params.enforceFinalTag,
+            promptContextMode: params.promptContextMode,
+            promptContextReason: params.promptContextReason,
+            compactionCountBeforeRun: params.compactionCountBeforeRun,
           });
 
           const {

src/agents/pi-embedded-runner/run/attempt.ts

@@ -434,6 +434,7 @@ export async function runEmbeddedAttempt(
     });
     const ttsHint = params.config ? buildTtsSystemPromptHint(params.config) : undefined;
 
+    const promptContextMode = params.promptContextMode ?? "full";
     const appendPrompt = buildEmbeddedSystemPrompt({
       workspaceDir: effectiveWorkspace,
       defaultThinkLevel: params.thinkLevel,
@@ -458,7 +459,9 @@ export async function runEmbeddedAttempt(
       userTimezone,
       userTime,
       userTimeFormat,
-      contextFiles,
+      contextFiles: promptContextMode === "full" ? contextFiles : [],
+      projectContextMode: promptContextMode,
+      contextFilePaths: contextFiles.map((file) => file.path),
       memoryCitationsMode: params.config?.memory?.citations,
     });
     const systemPromptReport = buildSystemPromptReport({
@@ -480,9 +483,12 @@ export async function runEmbeddedAttempt(
       })(),
       systemPrompt: appendPrompt,
       bootstrapFiles: hookAdjustedBootstrapFiles,
-      injectedFiles: contextFiles,
+      injectedFiles: promptContextMode === "full" ? contextFiles : [],
       skillsPrompt,
       tools,
+      contextInjectionMode: promptContextMode,
+      contextInjectionReason: params.promptContextReason,
+      compactionCountAtBuild: params.compactionCountBeforeRun,
     });
     const systemPromptOverride = createSystemPromptOverride(appendPrompt);
     const systemPromptText = systemPromptOverride();

src/agents/pi-embedded-runner/run/params.ts

@@ -101,4 +101,15 @@ export type RunEmbeddedPiAgentParams = {
   streamParams?: AgentStreamParams;
   ownerNumbers?: string[];
   enforceFinalTag?: boolean;
+  /** Controls whether full project-context files are reinjected this turn. */
+  promptContextMode?: "full" | "delta";
+  /** Why promptContextMode was selected. */
+  promptContextReason?:
+    | "session-start"
+    | "session-reset"
+    | "compaction"
+    | "model-handoff"
+    | "steady-state";
+  /** Compaction count observed before this run (from session entry). */
+  compactionCountBeforeRun?: number;
 };

src/agents/pi-embedded-runner/system-prompt.ts

@@ -47,6 +47,8 @@ export function buildEmbeddedSystemPrompt(params: {
   userTime?: string;
   userTimeFormat?: ResolvedTimeFormat;
   contextFiles?: EmbeddedContextFile[];
+  projectContextMode?: "full" | "delta";
+  contextFilePaths?: string[];
   memoryCitationsMode?: MemoryCitationsMode;
 }): string {
   return buildAgentSystemPrompt({
@@ -73,6 +75,8 @@ export function buildEmbeddedSystemPrompt(params: {
     userTime: params.userTime,
     userTimeFormat: params.userTimeFormat,
     contextFiles: params.contextFiles,
+    projectContextMode: params.projectContextMode,
+    contextFilePaths: params.contextFilePaths,
     memoryCitationsMode: params.memoryCitationsMode,
   });
 }

src/agents/system-prompt-report.ts

@@ -125,6 +125,9 @@ export function buildSystemPromptReport(params: {
   injectedFiles: EmbeddedContextFile[];
   skillsPrompt: string;
   tools: AgentTool[];
+  contextInjectionMode?: SessionSystemPromptReport["contextInjectionMode"];
+  contextInjectionReason?: SessionSystemPromptReport["contextInjectionReason"];
+  compactionCountAtBuild?: number;
 }): SessionSystemPromptReport {
   const systemPrompt = params.systemPrompt.trim();
   const projectContext = extractBetween(
@@ -155,6 +158,11 @@ export function buildSystemPromptReport(params: {
       projectContextChars,
       nonProjectContextChars: Math.max(0, systemPrompt.length - projectContextChars),
     },
+    contextInjectionMode: params.contextInjectionMode,
+    contextInjectionReason: params.contextInjectionReason,
+    compactionCountAtBuild: params.compactionCountAtBuild,
+    fullPromptCompactionCount:
+      params.contextInjectionMode === "full" ? params.compactionCountAtBuild : undefined,
     injectedWorkspaceFiles: buildInjectedWorkspaceFiles({
       bootstrapFiles: params.bootstrapFiles,
       injectedFiles: params.injectedFiles,

src/agents/system-prompt.ts

@@ -180,6 +180,10 @@ export function buildAgentSystemPrompt(params: {
   userTime?: string;
   userTimeFormat?: ResolvedTimeFormat;
   contextFiles?: EmbeddedContextFile[];
+  /** Inject full project context files or only a lightweight delta note. */
+  projectContextMode?: "full" | "delta";
+  /** Paths to context files for delta-mode reminders. */
+  contextFilePaths?: string[];
   skillsPrompt?: string;
   heartbeatPrompt?: string;
   docsPath?: string;
@@ -577,10 +581,14 @@ export function buildAgentSystemPrompt(params: {
   }
 
   const contextFiles = params.contextFiles ?? [];
+  const projectContextMode = params.projectContextMode ?? "full";
   const validContextFiles = contextFiles.filter(
     (file) => typeof file.path === "string" && file.path.trim().length > 0,
   );
-  if (validContextFiles.length > 0) {
+  const deltaContextPaths = (params.contextFilePaths ?? validContextFiles.map((file) => file.path))
+    .map((value) => value.trim())
+    .filter(Boolean);
+  if (projectContextMode === "full" && validContextFiles.length > 0) {
     const hasSoulFile = validContextFiles.some((file) => {
       const normalizedPath = file.path.trim().replace(/\\/g, "/");
       const baseName = normalizedPath.split("/").pop() ?? normalizedPath;
@@ -597,6 +605,17 @@ export function buildAgentSystemPrompt(params: {
       lines.push(`## ${file.path}`, "", file.content, "");
     }
   }
+  if (projectContextMode === "delta" && deltaContextPaths.length > 0) {
+    lines.push(
+      "# Project Context (delta)",
+      "",
+      "Full project-context file contents were already injected earlier in this session.",
+      "Reinject full context on session starts/resets, compaction boundaries, and model/session handoffs.",
+      "Known context files:",
+      ...deltaContextPaths.map((path) => `- ${path}`),
+      "",
+    );
+  }
 
   // Skip silent replies for subagent/none modes
   if (!isMinimal) {

src/auto-reply/reply/agent-runner-utils.ts

@@ -165,6 +165,9 @@ export function buildEmbeddedRunBaseParams(params: {
     skillsSnapshot: params.run.skillsSnapshot,
     ownerNumbers: params.run.ownerNumbers,
     enforceFinalTag: resolveEnforceFinalTag(params.run, params.provider),
+    promptContextMode: params.run.promptContextMode,
+    promptContextReason: params.run.promptContextReason,
+    compactionCountBeforeRun: params.run.compactionCountBeforeRun,
     provider: params.provider,
     model: params.model,
     ...params.authProfile,

src/auto-reply/reply/followup-runner.ts

@@ -160,6 +160,9 @@ export function createFollowupRunner(params: {
               extraSystemPrompt: queued.run.extraSystemPrompt,
               ownerNumbers: queued.run.ownerNumbers,
               enforceFinalTag: queued.run.enforceFinalTag,
+              promptContextMode: queued.run.promptContextMode,
+              promptContextReason: queued.run.promptContextReason,
+              compactionCountBeforeRun: queued.run.compactionCountBeforeRun,
               provider,
               model,
               ...authProfile,
@@ -212,6 +215,7 @@ export function createFollowupRunner(params: {
           modelUsed,
           providerUsed: fallbackProvider,
           contextTokensUsed,
+          systemPromptReport: runResult.meta?.systemPromptReport,
           logLabel: "followup",
         });
       }

src/auto-reply/reply/get-reply-run.ts

@@ -383,6 +383,45 @@ export async function runPreparedReply(
     isNewSession,
   });
   const authProfileIdSource = sessionEntry?.authProfileOverrideSource;
+  const compactionCountBeforeRun = sessionEntry?.compactionCount ?? 0;
+  const lastPromptReport = sessionEntry?.systemPromptReport;
+  const lastFullPromptCompactionCount = lastPromptReport?.fullPromptCompactionCount;
+  const hasCompactedSinceLastFullPrompt =
+    typeof lastFullPromptCompactionCount === "number"
+      ? compactionCountBeforeRun > lastFullPromptCompactionCount
+      : compactionCountBeforeRun > 0;
+  const normalizedModelForCompare = (() => {
+    const trimmed = model.trim();
+    if (!trimmed) {
+      return trimmed;
+    }
+    const slashIndex = trimmed.indexOf("/");
+    return slashIndex >= 0 ? trimmed.slice(slashIndex + 1) : trimmed;
+  })();
+  const modelHandoffDetected =
+    !isNewSession &&
+    Boolean(
+      (sessionEntry?.modelProvider && sessionEntry.modelProvider !== provider) ||
+      (sessionEntry?.model && sessionEntry.model !== normalizedModelForCompare),
+    );
+  const promptContextMode: "full" | "delta" =
+    isNewSession || resetTriggered || hasCompactedSinceLastFullPrompt || modelHandoffDetected
+      ? "full"
+      : "delta";
+  const promptContextReason:
+    | "session-start"
+    | "session-reset"
+    | "compaction"
+    | "model-handoff"
+    | "steady-state" = isNewSession
+    ? "session-start"
+    : resetTriggered
+      ? "session-reset"
+      : hasCompactedSinceLastFullPrompt
+        ? "compaction"
+        : modelHandoffDetected
+          ? "model-handoff"
+          : "steady-state";
   const followupRun = {
     prompt: queuedBody,
     messageId: sessionCtx.MessageSidFull ?? sessionCtx.MessageSid,
@@ -431,6 +470,9 @@ export async function runPreparedReply(
       blockReplyBreak: resolvedBlockStreamingBreak,
       ownerNumbers: command.ownerList.length > 0 ? command.ownerList : undefined,
       extraSystemPrompt: extraSystemPrompt || undefined,
+      promptContextMode,
+      promptContextReason,
+      compactionCountBeforeRun,
       ...(isReasoningTagProvider(provider) ? { enforceFinalTag: true } : {}),
     },
   };

src/auto-reply/reply/queue/types.ts

@@ -78,6 +78,17 @@ export type FollowupRun = {
     ownerNumbers?: string[];
     extraSystemPrompt?: string;
     enforceFinalTag?: boolean;
+    /** Controls whether full project-context files are reinjected this turn. */
+    promptContextMode?: "full" | "delta";
+    /** Why promptContextMode was selected. */
+    promptContextReason?:
+      | "session-start"
+      | "session-reset"
+      | "compaction"
+      | "model-handoff"
+      | "steady-state";
+    /** Compaction count observed before this run (from session entry). */
+    compactionCountBeforeRun?: number;
   };
 };
 

src/config/sessions/types.ts

@@ -169,6 +169,19 @@ export type SessionSystemPromptReport = {
     projectContextChars: number;
     nonProjectContextChars: number;
   };
+  /** Whether this run injected full project context files or used lightweight delta context. */
+  contextInjectionMode?: "full" | "delta";
+  /** Reason selected for this run's context injection mode. */
+  contextInjectionReason?:
+    | "session-start"
+    | "session-reset"
+    | "compaction"
+    | "model-handoff"
+    | "steady-state";
+  /** Compaction count observed when this prompt was built. */
+  compactionCountAtBuild?: number;
+  /** Latest compaction count for which a full prompt was injected. */
+  fullPromptCompactionCount?: number;
   injectedWorkspaceFiles: Array<{
     name: string;
     path: string;