feat(session-anchors): configurable budget scale + research-backed truncation fix

Remove 500-char assistant text truncation in anchor serializer — research
consensus (JetBrains NeurIPS 2025, SWE-agent, OpenDev ACC) is that agent
reasoning must never be truncated; only tool outputs get observation-masked.

Add AnchorBudgetScale type with 4 presets (Small=2K, Medium=6K, Large=12K,
Full=20K) and per-project range slider in SettingsTab. Remove Ollama-specific
warning toast — budget slider handles context limits generically.

v2/src/lib/agent-dispatcher.ts

@@ -31,6 +31,7 @@ import { extractWritePaths, extractWorktreePath } from './utils/tool-files';
 import { hasAutoAnchored, markAutoAnchored, addAnchors, getAnchorSettings } from './stores/anchors.svelte';
 import { selectAutoAnchors, serializeAnchorsForInjection } from './utils/anchor-serializer';
 import type { SessionAnchor } from './types/anchors';
+import { getEnabledProjects } from './stores/workspace.svelte';
 
 let unlistenMsg: (() => void) | null = null;
 let unlistenExit: (() => void) | null = null;
@@ -418,7 +419,8 @@ function triggerAutoAnchor(
 ): void {
   markAutoAnchored(projectId);
 
-  const settings = getAnchorSettings(projectId);
+  const project = getEnabledProjects().find(p => p.id === projectId);
+  const settings = getAnchorSettings(project?.anchorBudgetScale);
   const { turns, totalTokens } = selectAutoAnchors(
     messages,
     sessionPrompt,

v2/src/lib/components/Agent/AgentPane.svelte

@@ -14,7 +14,7 @@
   import { getInjectableAnchors, getProjectAnchors, addAnchors, removeAnchor } from '../../stores/anchors.svelte';
   import { estimateTokens } from '../../utils/anchor-serializer';
   import type { SessionAnchor } from '../../types/anchors';
-  import { notify } from '../../stores/notifications.svelte';
+
   import AgentTree from './AgentTree.svelte';
   import { getHighlighter, highlightCode, escapeHtml } from '../../utils/highlight';
   import type {
@@ -171,12 +171,6 @@
       if (anchors.length > 0) {
         // Anchors store pre-serialized content — join them directly
         systemPrompt = anchors.map(a => a.content).join('\n');
-
-        // Warn if Ollama provider — default context windows (2K-4K) may be too small
-        if (providerId === 'ollama') {
-          const anchorTokens = anchors.reduce((sum, a) => sum + a.estimatedTokens, 0);
-          notify('warning', `Ollama: injecting ~${anchorTokens} anchor tokens into system prompt. Ensure num_ctx >= 8192 to avoid truncation.`);
-        }
       }
     }
 

v2/src/lib/components/Workspace/ContextTab.svelte

@@ -9,15 +9,16 @@
     removeAnchor,
     changeAnchorType,
   } from '../../stores/anchors.svelte';
-  import { DEFAULT_ANCHOR_SETTINGS, MAX_ANCHOR_TOKEN_BUDGET } from '../../types/anchors';
-  import type { SessionAnchor, AnchorType } from '../../types/anchors';
+  import { ANCHOR_BUDGET_SCALE_MAP, MAX_ANCHOR_TOKEN_BUDGET } from '../../types/anchors';
+  import type { SessionAnchor, AnchorType, AnchorBudgetScale } from '../../types/anchors';
 
   interface Props {
     sessionId: string | null;
     projectId?: string;
+    anchorBudgetScale?: AnchorBudgetScale;
   }
 
-  let { sessionId, projectId }: Props = $props();
+  let { sessionId, projectId, anchorBudgetScale }: Props = $props();
 
   // Reactive session data
   let session = $derived(sessionId ? getAgentSession(sessionId) : undefined);
@@ -193,7 +194,7 @@
   let anchors = $derived(projectId ? getProjectAnchors(projectId) : []);
   let injectableAnchors = $derived(projectId ? getInjectableAnchors(projectId) : []);
   let anchorTokens = $derived(projectId ? getInjectableTokenCount(projectId) : 0);
-  let anchorBudget = $derived(DEFAULT_ANCHOR_SETTINGS.anchorTokenBudget);
+  let anchorBudget = $derived(ANCHOR_BUDGET_SCALE_MAP[anchorBudgetScale ?? 'medium']);
   let anchorBudgetPct = $derived(anchorBudget > 0 ? Math.min((anchorTokens / anchorBudget) * 100, 100) : 0);
 
   function anchorTypeLabel(t: AnchorType): string {

v2/src/lib/components/Workspace/ProjectBox.svelte

@@ -157,7 +157,7 @@
       <ProjectFiles cwd={project.cwd} projectName={project.name} />
     </div>
     <div class="content-pane" style:display={activeTab === 'context' ? 'flex' : 'none'}>
-      <ContextTab sessionId={mainSessionId} projectId={project.id} />
+      <ContextTab sessionId={mainSessionId} projectId={project.id} anchorBudgetScale={project.anchorBudgetScale} />
     </div>
 
     <!-- PERSISTED-LAZY: mount on first activation, then toggle via display -->

v2/src/lib/components/Workspace/SettingsTab.svelte

@@ -20,6 +20,7 @@
   import { invoke } from '@tauri-apps/api/core';
   import { getProviders } from '../../providers/registry.svelte';
   import type { ProviderId, ProviderSettings } from '../../providers/types';
+  import { ANCHOR_BUDGET_SCALES, ANCHOR_BUDGET_SCALE_LABELS, type AnchorBudgetScale } from '../../types/anchors';
 
   const PROJECT_ICONS = [
     '📁', '🚀', '🤖', '🌐', '🔧', '🎮', '📱', '💻',
@@ -771,6 +772,27 @@
               </div>
             {/if}
 
+            <div class="card-field">
+              <span class="card-field-label">
+                <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M12 20V10"/><path d="M18 20V4"/><path d="M6 20v-4"/></svg>
+                Anchor Budget
+              </span>
+              <div class="scale-slider">
+                <input
+                  type="range"
+                  min="0"
+                  max={ANCHOR_BUDGET_SCALES.length - 1}
+                  step="1"
+                  value={ANCHOR_BUDGET_SCALES.indexOf(project.anchorBudgetScale ?? 'medium')}
+                  oninput={(e) => {
+                    const idx = parseInt((e.target as HTMLInputElement).value);
+                    updateProject(activeGroupId, project.id, { anchorBudgetScale: ANCHOR_BUDGET_SCALES[idx] });
+                  }}
+                />
+                <span class="scale-label">{ANCHOR_BUDGET_SCALE_LABELS[project.anchorBudgetScale ?? 'medium']}</span>
+              </div>
+            </div>
+
             <div class="card-footer">
               <button class="btn-remove" onclick={() => removeProject(activeGroupId, project.id)}>
                 <svg width="12" height="12" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M3 6h18"/><path d="M8 6V4h8v2"/><path d="M19 6v14a2 2 0 0 1-2 2H7a2 2 0 0 1-2-2V6"/></svg>
@@ -1203,6 +1225,40 @@
     font-family: var(--term-font-family, monospace);
   }
 
+  /* Anchor budget scale slider */
+  .scale-slider {
+    display: flex;
+    align-items: center;
+    gap: 0.5rem;
+  }
+
+  .scale-slider input[type="range"] {
+    flex: 1;
+    height: 0.25rem;
+    appearance: none;
+    background: var(--ctp-surface1);
+    border-radius: 0.125rem;
+    outline: none;
+    cursor: pointer;
+  }
+
+  .scale-slider input[type="range"]::-webkit-slider-thumb {
+    appearance: none;
+    width: 0.875rem;
+    height: 0.875rem;
+    border-radius: 50%;
+    background: var(--ctp-blue);
+    border: 2px solid var(--ctp-base);
+    cursor: pointer;
+  }
+
+  .scale-label {
+    font-size: 0.75rem;
+    color: var(--ctp-subtext0);
+    white-space: nowrap;
+    min-width: 5.5em;
+  }
+
   /* CWD input: left-ellipsis */
   .cwd-input {
     direction: rtl;

v2/src/lib/stores/anchors.svelte.ts

@@ -1,8 +1,8 @@
 // Session Anchors store — Svelte 5 runes
 // Per-project anchor management with re-injection support
 
-import type { SessionAnchor, AnchorType, SessionAnchorRecord } from '../types/anchors';
-import { DEFAULT_ANCHOR_SETTINGS } from '../types/anchors';
+import type { SessionAnchor, AnchorType, AnchorBudgetScale, SessionAnchorRecord } from '../types/anchors';
+import { DEFAULT_ANCHOR_SETTINGS, ANCHOR_BUDGET_SCALE_MAP } from '../types/anchors';
 import {
   saveSessionAnchors,
   loadSessionAnchors,
@@ -119,7 +119,11 @@ export async function loadAnchorsForProject(projectId: string): Promise<void> {
   }
 }
 
-/** Get anchor settings (uses defaults for now — per-project config can be added later) */
-export function getAnchorSettings(_projectId: string) {
-  return DEFAULT_ANCHOR_SETTINGS;
+/** Get anchor settings, resolving budget from per-project scale if provided */
+export function getAnchorSettings(budgetScale?: AnchorBudgetScale) {
+  if (!budgetScale) return DEFAULT_ANCHOR_SETTINGS;
+  return {
+    ...DEFAULT_ANCHOR_SETTINGS,
+    anchorTokenBudget: ANCHOR_BUDGET_SCALE_MAP[budgetScale],
+  };
 }

v2/src/lib/types/anchors.ts

@@ -37,6 +37,28 @@ export const MAX_ANCHOR_TOKEN_BUDGET = 20_000;
 /** Minimum token budget */
 export const MIN_ANCHOR_TOKEN_BUDGET = 2_000;
 
+/** Budget scale presets — maps to provider context window sizes */
+export type AnchorBudgetScale = 'small' | 'medium' | 'large' | 'full';
+
+/** Token budget for each scale preset */
+export const ANCHOR_BUDGET_SCALE_MAP: Record<AnchorBudgetScale, number> = {
+  small: 2_000,
+  medium: 6_144,
+  large: 12_000,
+  full: 20_000,
+};
+
+/** Human-readable labels for budget scale presets */
+export const ANCHOR_BUDGET_SCALE_LABELS: Record<AnchorBudgetScale, string> = {
+  small: 'Small (2K)',
+  medium: 'Medium (6K)',
+  large: 'Large (12K)',
+  full: 'Full (20K)',
+};
+
+/** Ordered list of scales for slider indexing */
+export const ANCHOR_BUDGET_SCALES: AnchorBudgetScale[] = ['small', 'medium', 'large', 'full'];
+
 /** Rust-side record shape (matches SessionAnchorRecord in session.rs) */
 export interface SessionAnchorRecord {
   id: string;

v2/src/lib/types/groups.ts

@@ -1,4 +1,5 @@
 import type { ProviderId } from '../providers/types';
+import type { AnchorBudgetScale } from './anchors';
 
 export interface ProjectConfig {
   id: string;
@@ -13,6 +14,8 @@ export interface ProjectConfig {
   provider?: ProviderId;
   /** When true, agents for this project use git worktrees for isolation */
   useWorktrees?: boolean;
+  /** Anchor token budget scale (defaults to 'medium' = 6K tokens) */
+  anchorBudgetScale?: AnchorBudgetScale;
 }
 
 export interface GroupConfig {

v2/src/lib/utils/anchor-serializer.ts

@@ -137,11 +137,10 @@ function serializeTurn(
     parts.push(`[Turn ${index + 1}] User: "${turn.userPrompt}"`);
   }
   if (turn.assistantText) {
-    // Truncate very long responses to ~500 chars
-    const text = turn.assistantText.length > 500
-      ? turn.assistantText.slice(0, 497) + '...'
-      : turn.assistantText;
-    parts.push(`[Turn ${index + 1}] Assistant: "${text}"`);
+    // Preserve assistant reasoning in full — research consensus (JetBrains NeurIPS 2025,
+    // SWE-agent, OpenDev ACC) is that agent reasoning must never be truncated;
+    // only tool outputs (observations) get masked
+    parts.push(`[Turn ${index + 1}] Assistant: "${turn.assistantText}"`);
   }
   if (turn.toolSummaries.length > 0) {
     parts.push(`[Turn ${index + 1}] Tools: ${turn.toolSummaries.join(' ')}`);