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feat(FN-3892): honor assigned runtime model for merger sessions

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- Add resolveMergerSessionModel helper to centralize merger model selection precedence
- Route merger session creation paths through the helper for commit, push/rebase, and autostash recovery flows
- Add comprehensive engine tests for merger model resolution and fallback behavior
- Document merger model hierarchy in settings reference and add a patch changeset for @runfusion/fusion

Fusion-Task-Id: FN-3892
This commit is contained in:
Fusion
2026-05-09 21:41:18 -07:00
committed by gsxdsm
parent 392713f851
commit 4051dabe4d
5 changed files with 142 additions and 35 deletions
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91
packages/engine/src/__tests__/agent-session-helpers.test.ts
View File

@@ -1,5 +1,5 @@
import { describe, expect, it } from "vitest";
import { extractRuntimeHint } from "../agent-session-helpers.js";
import { extractRuntimeHint, resolveMergerSessionModel } from "../agent-session-helpers.js";
describe("extractRuntimeHint", () => {
it("returns undefined for undefined config", () => {
@@ -22,3 +22,92 @@ describe("extractRuntimeHint", () => {
expect(extractRuntimeHint({ runtimeHint: 42 })).toBeUndefined();
});
});
describe("resolveMergerSessionModel", () => {
it("uses assigned agent runtime model when both provider and modelId are present", () => {
expect(
resolveMergerSessionModel(
{
defaultProviderOverride: "openai",
defaultModelIdOverride: "gpt-4.1",
defaultProvider: "anthropic",
defaultModelId: "claude-3-5-sonnet",
},
{ model: " anthropic/claude-3-5-sonnet-20241022 " },
),
).toEqual({
provider: "anthropic",
modelId: "claude-3-5-sonnet-20241022",
});
});
it("falls back to default override pair when runtime model is not fully specified", () => {
expect(
resolveMergerSessionModel(
{
defaultProviderOverride: "openai",
defaultModelIdOverride: "gpt-4.1",
defaultProvider: "anthropic",
defaultModelId: "claude-3-5-sonnet",
},
{ modelProvider: "anthropic" },
),
).toEqual({
provider: "openai",
modelId: "gpt-4.1",
});
});
it("falls back to global defaults when no override pair is configured", () => {
expect(
resolveMergerSessionModel(
{
defaultProvider: "anthropic",
defaultModelId: "claude-3-5-sonnet",
},
{ modelId: "claude-3-opus" },
),
).toEqual({
provider: "anthropic",
modelId: "claude-3-5-sonnet",
});
});
it("ignores partial override pairs and falls back to global defaults", () => {
expect(
resolveMergerSessionModel({
defaultProviderOverride: "openai",
defaultProvider: "anthropic",
defaultModelId: "claude-3-5-sonnet",
}),
).toEqual({
provider: "anthropic",
modelId: "claude-3-5-sonnet",
});
expect(
resolveMergerSessionModel({
defaultModelIdOverride: "gpt-4.1",
defaultProvider: "anthropic",
defaultModelId: "claude-3-5-sonnet",
}),
).toEqual({
provider: "anthropic",
modelId: "claude-3-5-sonnet",
});
});
it("works when assignedAgentRuntimeConfig is undefined", () => {
expect(
resolveMergerSessionModel({
defaultProviderOverride: "openai",
defaultModelIdOverride: "gpt-4.1",
defaultProvider: "anthropic",
defaultModelId: "claude-3-5-sonnet",
}),
).toEqual({
provider: "openai",
modelId: "gpt-4.1",
});
});
});

22
packages/engine/src/agent-session-helpers.ts
View File

@@ -163,6 +163,28 @@ export function resolvePlanningSessionModel(
};
}
export function resolveMergerSessionModel(
settings: Partial<Settings> | undefined,
assignedAgentRuntimeConfig?: Record<string, unknown>,
): { provider: string | undefined; modelId: string | undefined } {
const assignedRuntimeModel = extractRuntimeModel(assignedAgentRuntimeConfig);
if (assignedRuntimeModel.provider && assignedRuntimeModel.modelId) {
return assignedRuntimeModel;
}
if (settings?.defaultProviderOverride && settings.defaultModelIdOverride) {
return {
provider: settings.defaultProviderOverride,
modelId: settings.defaultModelIdOverride,
};
}
return {
provider: settings?.defaultProvider,
modelId: settings?.defaultModelId,
};
}
/**
* Create an agent session using runtime resolution.
*

52
packages/engine/src/merger.ts
View File

@@ -53,7 +53,7 @@ import {
} from "@fusion/core";
import { describeModel, promptWithFallback } from "./pi.js";
import { accumulateSessionTokenUsage } from "./session-token-usage.js";
import { createResolvedAgentSession, extractRuntimeHint } from "./agent-session-helpers.js";
import { createResolvedAgentSession, extractRuntimeHint, resolveMergerSessionModel } from "./agent-session-helpers.js";
import { createFallbackModelObserver } from "./fallback-model-observer.js";
import { buildSessionSkillContext } from "./session-skill-context.js";
import type { WorktreePool } from "./worktree-pool.js";
@@ -820,6 +820,7 @@ async function attemptInMergeVerificationFix(
? await agentStoreWithGetAgent.getAgent(assignedAgentId).catch(() => null)
: null;
const mergerRuntimeHint = extractRuntimeHint(assignedAgent?.runtimeConfig);
const mergerSessionModel = resolveMergerSessionModel(settings, assignedAgent?.runtimeConfig);
const { session } = await createResolvedAgentSession({
sessionPurpose: "merger",
runtimeHint: mergerRuntimeHint,
@@ -846,12 +847,8 @@ Do not refactor, rename broadly, or make opportunistic improvements.
onThinking: logger.onThinking,
onToolStart: logger.onToolStart,
onToolEnd: logger.onToolEnd,
defaultProvider: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultProviderOverride
: settings.defaultProvider,
defaultModelId: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultModelIdOverride
: settings.defaultModelId,
defaultProvider: mergerSessionModel.provider,
defaultModelId: mergerSessionModel.modelId,
fallbackProvider: settings.fallbackProvider,
fallbackModelId: settings.fallbackModelId,
defaultThinkingLevel: settings.defaultThinkingLevel,
@@ -1919,6 +1916,7 @@ async function runAiAgentForAutostashConflict(params: {
? await agentStoreWithGetAgent.getAgent(assignedAgentId).catch(() => null)
: null;
const mergerRuntimeHint = extractRuntimeHint(assignedAgent?.runtimeConfig);
const mergerSessionModel = resolveMergerSessionModel(settings, assignedAgent?.runtimeConfig);
const systemPrompt = `You are an autostash-conflict resolution agent running after a Fusion merge has already committed on the main branch.
@@ -1962,12 +1960,8 @@ ${fileList}
onThinking: agentLogger.onThinking,
onToolStart: agentLogger.onToolStart,
onToolEnd: agentLogger.onToolEnd,
defaultProvider: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultProviderOverride
: settings.defaultProvider,
defaultModelId: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultModelIdOverride
: settings.defaultModelId,
defaultProvider: mergerSessionModel.provider,
defaultModelId: mergerSessionModel.modelId,
fallbackProvider: settings.fallbackProvider,
fallbackModelId: settings.fallbackModelId,
defaultThinkingLevel: settings.defaultThinkingLevel,
@@ -2290,6 +2284,7 @@ async function runAiAgentForAutostashHardFail(params: {
? await agentStoreWithGetAgent.getAgent(assignedAgentId).catch(() => null)
: null;
const mergerRuntimeHint = extractRuntimeHint(assignedAgent?.runtimeConfig);
const mergerSessionModel = resolveMergerSessionModel(settings, assignedAgent?.runtimeConfig);
const systemPrompt = `You are an autostash hard-failure recovery agent for the Fusion merger.
@@ -2343,12 +2338,8 @@ ${fileList}
onThinking: agentLogger.onThinking,
onToolStart: agentLogger.onToolStart,
onToolEnd: agentLogger.onToolEnd,
defaultProvider: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultProviderOverride
: settings.defaultProvider,
defaultModelId: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultModelIdOverride
: settings.defaultModelId,
defaultProvider: mergerSessionModel.provider,
defaultModelId: mergerSessionModel.modelId,
fallbackProvider: settings.fallbackProvider,
fallbackModelId: settings.fallbackModelId,
defaultThinkingLevel: settings.defaultThinkingLevel,
@@ -4143,6 +4134,7 @@ async function resolveComplexRebaseConflictsWithAi(
pluginRunner?: import("./plugin-runner.js").PluginRunner;
signal?: AbortSignal;
runtimeHint?: string;
assignedAgentRuntimeConfig?: Record<string, unknown>;
onSession?: (session: { dispose: () => void }) => void;
},
): Promise<void> {
@@ -4171,6 +4163,7 @@ You are assisting with a paused \`git pull --rebase\`.
});
throwIfAborted(options?.signal, taskId);
const mergerSessionModel = resolveMergerSessionModel(settings, options?.assignedAgentRuntimeConfig);
const { session } = await createResolvedAgentSession({
sessionPurpose: "merger",
runtimeHint: options?.runtimeHint,
@@ -4182,12 +4175,8 @@ You are assisting with a paused \`git pull --rebase\`.
onThinking: agentLogger.onThinking,
onToolStart: agentLogger.onToolStart,
onToolEnd: agentLogger.onToolEnd,
defaultProvider: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultProviderOverride
: settings.defaultProvider,
defaultModelId: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultModelIdOverride
: settings.defaultModelId,
defaultProvider: mergerSessionModel.provider,
defaultModelId: mergerSessionModel.modelId,
fallbackProvider: settings.fallbackProvider,
fallbackModelId: settings.fallbackModelId,
defaultThinkingLevel: settings.defaultThinkingLevel,
@@ -4241,6 +4230,7 @@ async function resolveRebaseConflictSet(
onAgentText?: (delta: string) => void;
signal?: AbortSignal;
runtimeHint?: string;
assignedAgentRuntimeConfig?: Record<string, unknown>;
onSession?: (session: { dispose: () => void }) => void;
},
): Promise<void> {
@@ -4289,6 +4279,7 @@ async function pullWithRebaseAndResolveConflicts(
onAgentText?: (delta: string) => void;
signal?: AbortSignal;
runtimeHint?: string;
assignedAgentRuntimeConfig?: Record<string, unknown>;
onSession?: (session: { dispose: () => void }) => void;
},
): Promise<void> {
@@ -4385,6 +4376,7 @@ export async function pushToRemoteAfterMerge(
onAgentText?: (delta: string) => void;
signal?: AbortSignal;
runtimeHint?: string;
assignedAgentRuntimeConfig?: Record<string, unknown>;
onSession?: (session: { dispose: () => void }) => void;
},
): Promise<{ pushed: boolean; error?: string }> {
@@ -5891,6 +5883,7 @@ export async function aiMergeTask(
onAgentText: options.onAgentText,
signal: options.signal,
runtimeHint: pushRuntimeHint,
assignedAgentRuntimeConfig: pushAssignedAgent?.runtimeConfig,
onSession: options.onSession,
});
if (pushResult.pushed) {
@@ -6833,6 +6826,7 @@ async function runAiAgentForCommit(params: AiAgentParams): Promise<{ success: bo
? await agentStoreWithGetAgent.getAgent(assignedAgentId).catch(() => null)
: null;
const mergerRuntimeHint = extractRuntimeHint(assignedAgent?.runtimeConfig);
const mergerSessionModel = resolveMergerSessionModel(settings, assignedAgent?.runtimeConfig);
const { session } = await createResolvedAgentSession({
sessionPurpose: "merger",
@@ -6846,12 +6840,8 @@ async function runAiAgentForCommit(params: AiAgentParams): Promise<{ success: bo
onThinking: agentLogger.onThinking,
onToolStart: agentLogger.onToolStart,
onToolEnd: agentLogger.onToolEnd,
defaultProvider: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultProviderOverride
: settings.defaultProvider,
defaultModelId: settings.defaultProviderOverride && settings.defaultModelIdOverride
? settings.defaultModelIdOverride
: settings.defaultModelId,
defaultProvider: mergerSessionModel.provider,
defaultModelId: mergerSessionModel.modelId,
fallbackProvider: settings.fallbackProvider,
fallbackModelId: settings.fallbackModelId,
defaultThinkingLevel: settings.defaultThinkingLevel,