Fix: Forward customModel to batch synopsis call

[pedramamini]

Summary

• Forward customModel to the synopsis spawnAgent call in batch-processor.ts so synopsis generation uses the user's configured model instead of the default
• Fix prettier formatting in agent-spawner.ts (leftover from fix: enforce read-only mode for JSON line agents and pass customModel in CLI #563)

Context

Follow-up to #563 — the task-execution call got customModel forwarded but the synopsis call was missed.

Test plan

• Existing agent-spawner tests pass (verified via pre-push hook)
• Batch processor with custom model uses that model for both task execution and synopsis

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[greptile-apps]

Greptile Summary

This PR is a targeted follow-up to #563 that forwards customModel to the synopsis spawnAgent call in batch-processor.ts, ensuring synopsis generation uses the user's configured model consistently with the task-execution call. It also includes a cosmetic reformatting of CLAUDE_ARGS in agent-spawner.ts.

• batch-processor.ts: Adds { customModel: session.customModel } as the options argument to the synopsis spawnAgent call (lines 483–484), making it symmetric with the already-fixed task-execution call.
• agent-spawner.ts: Collapses the multi-line CLAUDE_ARGS array to a single line — no functional change.
• Pre-existing gap: customModel is extracted inside spawnAgent but is never forwarded to spawnClaudeAgent. Claude Code users who configure a custom model will still see it silently ignored in both task-execution and synopsis paths. The comment in spawnClaudeAgent acknowledges this limitation, though Claude Code CLI does accept --model. This is not introduced by this PR, but the fix is incomplete for the claude-code tool type.

Confidence Score: 4/5

• Safe to merge — the change is minimal, correct for non-Claude-Code agents, and introduces no regressions.
• The fix is a one-liner that makes the synopsis call consistent with the task-execution call. The only concern is a pre-existing limitation where customModel is silently ignored for claude-code agents, but this PR doesn't worsen that situation — it simply doesn't fix it either.
• No files require special attention; the pre-existing spawnClaudeAgent limitation in agent-spawner.ts is worth addressing in a follow-up if Claude Code custom model support is desired.

Important Files Changed

Filename	Overview
src/cli/services/batch-processor.ts	Adds { customModel: session.customModel } as the options argument to the synopsis spawnAgent call, making it consistent with the task-execution call added in #563. The change is minimal, correct, and addresses the stated goal for non-Claude-Code agents.
src/cli/services/agent-spawner.ts	Pure formatting fix — collapses the multi-line CLAUDE_ARGS constant to a single line. No functional change, but highlights a pre-existing gap: customModel extracted in spawnAgent is never forwarded to spawnClaudeAgent, so Claude Code users with a custom model still won't see it applied in either task execution or synopsis calls.

Sequence Diagram

sequenceDiagram
    participant BP as batch-processor.ts<br/>(runPlaybook)
    participant SA as agent-spawner.ts<br/>(spawnAgent)
    participant CL as spawnClaudeAgent
    participant JL as spawnJsonLineAgent

    Note over BP: Task Execution
    BP->>SA: spawnAgent(toolType, cwd, finalPrompt, undefined,<br/>{ customModel })
    alt toolType === 'claude-code'
        SA->>CL: spawnClaudeAgent(cwd, prompt, agentSessionId, readOnly)
        Note over CL: ⚠️ customModel silently dropped
    else usesJsonLineOutput
        SA->>JL: spawnJsonLineAgent(..., customModel)
        Note over JL: ✅ customModel applied via def.modelArgs
    end

    Note over BP: Synopsis Generation (this PR's fix)
    BP->>SA: spawnAgent(toolType, cwd, BATCH_SYNOPSIS_PROMPT,<br/>result.agentSessionId, { customModel })
    alt toolType === 'claude-code'
        SA->>CL: spawnClaudeAgent(cwd, prompt, agentSessionId, readOnly)
        Note over CL: ⚠️ customModel silently dropped (pre-existing)
    else usesJsonLineOutput
        SA->>JL: spawnJsonLineAgent(..., customModel)
        Note over JL: ✅ customModel now correctly forwarded
    end

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Comments Outside Diff (1)

1. src/cli/services/agent-spawner.ts, line 518-520 (link)

   customModel silently dropped for claude-code

   customModel is extracted from options (line 516) but is never forwarded to spawnClaudeAgent — the function signature doesn't even accept it. This means that even after this PR's fix in batch-processor.ts, synopsis (and task-execution) calls for Claude Code users who configure a custom model will silently ignore it and fall back to the default model.

   The spawnClaudeAgent JSDoc acknowledges this ("Custom model … [is] not supported in CLI mode"), but Claude Code CLI does accept a --model flag. If supporting customModel for Claude Code is in scope, spawnClaudeAgent would need a customModel?: string parameter and the corresponding --model <value> args appended — similar to how spawnJsonLineAgent handles it via def.modelArgs. At minimum, it may be worth updating the comment to explicitly note that customModel is intentionally unsupported rather than merely a missing feature.

_{Last reviewed commit: a787abb}