LLM To Bedrock

Migrate to Bedrock (Assess + Execute)

Single-command AI migration: OpenAI / Gemini / Anthropic → Amazon Bedrock.

Requires the gcp-to-aws skill installed alongside this one. This skill has no standalone Assess implementation — Phase A below delegates Assess entirely to gcp-to-aws via a cross-skill invocation, and there is no fallback path that performs Assess itself if gcp-to-aws is missing. If you installed this skill on its own (e.g. a single-skill npx skills add), install gcp-to-aws too before using it.

The skill base directory is given in the "Base directory for this skill: X" line the harness emits at load time. Call it <SKILL_BASE>. Derived paths:

• $SCRIPTS = <SKILL_BASE>/scripts
• $HELPERS = <SKILL_BASE>/references/helpers (the former helper skills, now references)

Step 0 — Check prerequisites

0a. Check that uv is available

uv --version 2>/dev/null || echo "MISSING"

If missing: "Install uv first — see the official install guide: https://docs.astral.sh/uv/getting-started/installation/ (e.g. brew install uv or pipx install uv)". Stop.

0b. Check that the gcp-to-aws sibling skill is installed

Phase A below delegates the entire Assess step to the gcp-to-aws skill via the Skill tool — there is no Assess logic in this skill to fall back to. gcp-to-aws is a separate skill, not bundled inside this one — a single-skill install (e.g. npx skills add ... --skill llm-to-bedrock) does not bring it along automatically. Check for it now, before promising the user an Assess phase this deployment cannot run:

[ -f "<SKILL_BASE>/../gcp-to-aws/SKILL.md" ] && echo GCP_TO_AWS_PRESENT || echo GCP_TO_AWS_MISSING

This checks the sibling directory relative to <SKILL_BASE> (defined above), which works under any install path — native plugin install and npx skills add --skill '*' both place gcp-to-aws as a sibling of this skill's own directory. It does not depend on ${CLAUDE_PLUGIN_ROOT}.

• GCP_TO_AWS_PRESENT → proceed to Step 1.

• GCP_TO_AWS_MISSING → stop here — do not proceed. Tell the user:

  "This migration needs the gcp-to-aws skill installed alongside this one — it handles code scanning, AI-workload detection, and Bedrock model design; I can't do that part myself without it. Install it with: npx skills add https://github.com/awslabs/startups/tree/main/advisor/plugins/aws-startup-advisor --skill gcp-to-aws --agent <agent> (use the same --agent and --global/project scope you used for this skill), restart your agent, then ask me to migrate again."

  Do not perform the Assess phase yourself as a workaround — Phase A below is explicit that Assess logic lives only in gcp-to-aws; re-implementing it here would drift out of sync with that skill's Discover/Clarify/Design logic over time. There is no standalone Assess for this skill — this check exists to fail fast and clearly, not to unlock alternate behavior.

Separately, invoking gcp-to-aws at all in Phase A requires your agent to support the Skill tool (cross-skill invocation by name). This is confirmed for Claude Code; it has not been verified across every agent that supports npx skills installs (Cursor, Codex, etc.) — if you're on one of those and this fails, that is the likely cause. If the Skill tool call in Phase A's A1 step fails or no such mechanism exists on your agent, this skill still has no fallback: tell the user plainly that this agent cannot chain into gcp-to-aws automatically, and ask them to invoke gcp-to-aws themselves directly (e.g. "migrate my AI workload to AWS") to run Discover through Generate, then come back to this skill once its generate phase is completed (checked in A2) to continue with the SDK rewrite. This is a manual two-step workaround for a missing agent capability, not an automated fallback — do not present it to the user as this skill "handling it."

Step 1 — Collect source code path

If $ARGUMENTS contains a path, use it as $REPO. Otherwise use AskUserQuestion: "Where is your source code? Enter a local path or GitHub URL."

If a GitHub URL, git clone it to a temp dir; use that path as $REPO.

Checks on $REPO:

1. Git-root check (compare resolved paths — on macOS /tmp resolves to /private/tmp, so a raw string comparison false-positives):

   [ "$(git -C <REPO> rev-parse --show-toplevel 2>/dev/null)" = "$(cd <REPO> && pwd -P)" ] && echo GIT_ROOT_OK || echo GIT_ROOT_MISMATCH
   

   • GIT_ROOT_OK → proceed.
   • GIT_ROOT_MISMATCH and the command errored (not a git repo at all) → tell the user the path must be a git repository (the deliverable is a git branch); re-ask.
   • GIT_ROOT_MISMATCH but inside a repo (user pointed at a subdirectory) → AskUserQuestion: "Use the repo root instead" (recommended) / "Continue with this subdirectory" / "Abort".

2. Dirty-tree check:

   git -C <REPO> status --porcelain
   

   If uncommitted changes exist, show them and AskUserQuestion: "Continue anyway" or "Let me clean up first".

Record $REPO for all subsequent steps.

Phase A — Assess (MANDATORY: delegate to the gcp-to-aws skill)

CRITICAL: You MUST use the Skill tool to invoke aws-startup-advisor:gcp-to-aws (a sibling skill in this same plugin). Do NOT perform the Assess phase yourself. Do NOT read source code, detect AI SDKs, or ask Clarify questions manually. The entire Assess phase is handled by the gcp-to-aws skill — you only invoke it and wait for completion.

A1 — Invoke the Assess skill

Call the Skill tool with skill name aws-startup-advisor:gcp-to-aws.

Before invoking, tell the user:

"I'm now invoking the gcp-to-aws Assess skill to discover your AI workloads and design the Bedrock migration. It will ask you some questions — please answer them. (Don't be confused by the skill's gcp-to-aws name — it also covers pure AI/LLM migrations with no GCP or infrastructure component, which is how it's being used here.)"

After invoking the Skill tool, the gcp-to-aws skill instructions will load into context. Follow those instructions exactly — they will drive the Discover, Clarify, Design, Estimate, and Generate phases. The source code to scan is at $REPO.

Important context for the gcp-to-aws skill execution:

• Source code is at $REPO — when the skill asks for GCP sources or scans for files, point it there
• This is an AI/LLM workload migration — the AI path is the goal
• Unless Terraform/IaC files are actually present in $REPO, skip IaC discovery
• Unless the user offers billing data, skip billing discovery. If the source provider is OpenAI, the skill may instead offer its OpenAI Admin API usage discovery (discover-openai-api.md — read-only, consent-gated, needs an Admin key with Usage set to Read); accepting it gives Estimate real spend and token volumes without manual CSV exports

A2 — Wait for Assess completion

The gcp-to-aws skill is a state machine. After each phase completes, it may stop and wait for the next invocation. Check progress against the LATEST run directory only (older .migration/ runs may contain a stale "completed" status):

MIGRATION_DIR=$(ls -td "$REPO/.migration"/*/ 2>/dev/null | head -1)
# Stdlib-only JSON read — no boto3, so bare python3 is fine here (no pinned env needed).
python3 -c "import json,sys; print(json.load(open('$MIGRATION_DIR/.phase-status.json'))['phases'].get('generate','missing'))" 2>/dev/null || echo "no-status-file"

• completed → proceed to A3.
• Anything else (including no-status-file) → the skill needs to run again. Re-invoke aws-startup-advisor:gcp-to-aws via the Skill tool — it picks up where it left off.

Cap: at most 6 re-invocations. If generate is still not completed after 6, stop and show the user the last status output — the Assess skill is stuck and needs manual attention; looping further just burns context.

A3 — Locate Assess output

Find $MIGRATION_DIR (the .migration/<MMDD-HHMM>/ directory that was created):

ls -td "$REPO/.migration"/*/ 2>/dev/null | head -1

Verify these files exist in $MIGRATION_DIR:

• aws-design-ai.json (model mapping + architecture)
• ai-workload-profile.json (detected workloads)
• preferences.json (user preferences from Clarify)

If aws-design-ai.json is missing, Assess did not complete the AI path correctly. Show the error and stop.

Phase B — Execute Prep

B1 — Read Assess outputs

Read $MIGRATION_DIR/aws-design-ai.json and extract:

• ai_architecture.bedrock_models[] → array of {source_model, aws_model_id, use_case}
• Collect all aws_model_id values into $TARGET_MODELS (array). Keep the use_case of each: the preflight script probes each model by the right API automatically (Converse for chat, InvokeModel for embeddings), but the evaluator's quality scoring only applies to chat models — embedding targets get format/dimension validation only.

Read $MIGRATION_DIR/ai-workload-profile.json and extract:

• summary.ai_source → source provider

Read $MIGRATION_DIR/preferences.json and extract:

• design_constraints.target_region → $REGION (default us-east-1 if absent)

Validation: If aws-design-ai.json has no ai_architecture.bedrock_models[] array, or the array is empty, STOP: "Assess output incomplete — model mapping missing."

B2 — AWS identity confirmation

aws sts get-caller-identity 2>&1

If the command fails (no credentials, expired SSO token): show the error and tell the user to run aws configure or aws sso login (suggest typing ! aws sso login to run it in this session), then re-run B2. Do not proceed without a confirmed identity.

On success, show Account, Arn, UserId via AskUserQuestion: "This AWS identity will be used for Bedrock calls. Is this correct?"

Options:

• Yes, use this identity → proceed
• Use a different AWS profile → ask which profile, record it as $AWS_PROFILE_CHOICE, re-run B2 as aws sts get-caller-identity --profile $AWS_PROFILE_CHOICE, and re-confirm. Do NOT rely on exporting AWS_PROFILE — env vars do not persist across Bash tool calls or into workflow subagents (see B3). Instead pass the choice explicitly everywhere: --profile on every aws CLI call, and prepend AWS_PROFILE=$AWS_PROFILE_CHOICE inline on the B4 preflight command and inside the workflow args (awsProfile field) so subagents can do the same.

Also confirm region: "Bedrock region will be $REGION. OK or override?"

B3 — Source API key (optional)

First, create the artifact directory and make it self-ignoring IMMEDIATELY — before any key exists, so the secret is never sitting in an unignored working tree (even if the user aborts before the rewriter runs):

mkdir -p "$REPO/.saws-migrate" && printf '*\n' > "$REPO/.saws-migrate/.gitignore"

Determine $KEY_ENV_VAR from B1's source provider (this is the env-var name the baseline skill's parser expects — a bare key without the NAME= prefix will NOT be parsed):

• openai → OPENAI_API_KEY
• anthropic → ANTHROPIC_API_KEY
• google / gemini → GEMINI_API_KEY

The key must never enter this conversation (HARD RULE). Do not ask the user to paste the key in chat, and never echo, cat, or interpolate its VALUE into any command, question, or output — the agent only ever handles the file path. If the user pastes a key into the chat unprompted, do not use it: tell them it is now part of the transcript, recommend rotating it, and continue with one of the paths below.

First check whether the key is already present in the shell environment (each Bash call initializes from the user's profile, so a profile-exported key is visible to every call). POSIX-safe — printenv works in bash and zsh alike (${!VAR} indirection is bash-only and zsh errors on it). This prints presence only, never the value:

[ -n "$(printenv "$KEY_ENV_VAR")" ] && echo ENV_KEY_PRESENT || echo ENV_KEY_ABSENT

AskUserQuestion: "Do you have an API key for the source model (e.g. OpenAI key for GPT-4o)? Providing it enables side-by-side quality comparison. Without it, evaluation uses absolute scoring only."

Options (offer the first only on ENV_KEY_PRESENT):

• Use the $KEY_ENV_VAR already in my environment → materialize env var to file in one command — the value never appears in the transcript:

  printf '%s=%s\n' "$KEY_ENV_VAR" "$(printenv "$KEY_ENV_VAR")" > "$REPO/.saws-migrate/.source-provider-env" && chmod 600 "$REPO/.saws-migrate/.source-provider-env"
  

  Then run the format check below and set sourceBaselineAvailable = true, sourceKeyRef = "$REPO/.saws-migrate/.source-provider-env".

• I'll write it to a file myself → give the user this command to run in THEIR OWN terminal (not through the agent; in Claude Code an ! prefix runs it in-session) — read -rs collects the key without echoing it:

  read -rs k && printf '%s=%s\n' "<KEY_ENV_VAR>" "$k" > "<REPO>/.saws-migrate/.source-provider-env" && chmod 600 "<REPO>/.saws-migrate/.source-provider-env" && unset k
  

  Substitute the literal env-var name and repo path when presenting it (those are not secrets). Then run the format check below and set the same flags as above.

• Skip → sourceBaselineAvailable = false, sourceKeyRef = "".

Whichever path wrote the file, verify the format (never prints the key; catches a value written without the NAME= prefix, which the baseline parser would silently miss):

grep -qE '^(OPENAI|ANTHROPIC|GEMINI)_API_KEY=.+' "$REPO/.saws-migrate/.source-provider-env" && echo KEY_FORMAT_OK || echo KEY_FORMAT_BAD

On KEY_FORMAT_BAD, have the same path that wrote the file rewrite it (do not echo its contents).

(.saws-migrate/ is already self-ignoring from the first command above; the rewriter re-asserts this before any commit as a second layer.)

IMPORTANT: The file is the handoff mechanism — do NOT rely on export to carry the key into later steps. Shell state set in one Bash call does not persist into other calls or into workflow subagents; only a profile-exported variable (the ENV_KEY_PRESENT path above) is reliably visible, and even that must be materialized to the file for the baseline runner.

B4 — Bedrock preflight

uv run --project $SCRIPTS python $SCRIPTS/preflight_bedrock.py --region $REGION --models <comma-separated $TARGET_MODELS> --dataset-size 200

(--dataset-size 200 matches the golden-dataset cap, so the quota warning reflects the worst case. Prefix with AWS_PROFILE=$AWS_PROFILE_CHOICE if B2 chose a non-default profile.)

Parse the JSON output. On failure the TOP LEVEL carries reason/detail (lifted from the first failing model) plus failing_models (all failing ids); per-model verdicts are in models[]:

• ok == false + reason: credentials → show the detail (configure/refresh credentials), stop; user re-runs after fixing.
• ok == false + reason: model_access → model access not enabled in the Bedrock console (NOT an IAM problem): point the user at the console Model access page for the failing models, stop; re-run B4 after they enable it.
• ok == false + reason: authz → IAM denies inference. For a Converse/InvokeModel target the action to grant is bedrock:InvokeModel; for a mantle-only openai.gpt-5* target it is the bedrock-mantle:* set (see B4a). The detail names which. Tell the user the action to grant; stop.
• ok == false + reason: mantle_deps_missing → the pinned scripts environment lacks openai / aws-bedrock-token-generator, so a mantle-only target could not be probed at all. This is an environment fault, not a Bedrock verdict: tell the user to re-sync (uv sync --project $SCRIPTS) and stop. Do NOT proceed — access was never verified.
• ok == false + reason: model_unavailable → Read the resolve-bedrock-model-id reference at $HELPERS/resolve-bedrock-model-id/resolve-bedrock-model-id.md and follow its procedure with each ID from failing_models + region. AskUserQuestion with the candidates: "Use <candidate> (cross-region inference profile)" / "Paste a different model ID" / "Abort". On a choice, replace the ID in $TARGET_MODELS and re-run B4.
• ok == false + any other reason → show detail and stop.
• ok == true → proceed. Surface any quota_warning, and any model whose reason is embedding_unprobed (embedding family the preflight can't probe — remind the user to confirm model access in the console).

Phase C — Execute

Phase C dispatches the five plugin agents sequentially via the Agent tool (subagent types aws-startup-advisor:llm2bedrock-code-analyzer, aws-startup-advisor:llm2bedrock-log-ingestor, aws-startup-advisor:llm2bedrock-prompt-evaluator, aws-startup-advisor:llm2bedrock-code-rewriter, aws-startup-advisor:llm2bedrock-report-generator). Each agent writes its result to a file under $PHASE_DIR = $REPO/.saws-migrate/phase-results/; you validate every file with the bundled validator before moving on. There is no workflow runtime — the files ARE the state.

The validator (used at every step)

uv run --project $SCRIPTS python $SCRIPTS/validate_result.py --schema <analysis|ingestion|eval|rewrite|delta-decisions> <file>

• Exit 0 + RESULT=valid CONTROL=ok → phase completed; proceed.
• Exit 0 + CONTROL=blocked REASON=<r> → blocked flow (below).
• Exit 0 + CONTROL=partial COMPLETED=<n> TOTAL=<m> → partial flow (eval only).
• Exit 1 (RESULT=invalid + error lines) or exit 2 (file missing) → stateless fixer retry: dispatch a FRESH agent of the same type whose prompt is the original context block + the file path + the validator's verbatim error output + the instruction "fix ONLY the output file at <path> so it validates; do not redo the phase's work unless a required field is genuinely missing from it". Cap 2 retries per phase; then stop and show the errors.

The context block (instantiated at every dispatch)

Build this exact line format (agents parse the labels). Omit lines marked optional when empty:

Repository: <$REPO>
AWS region: <$REGION>
AWS profile (pass as --profile / AWS_PROFILE= inline on every aws/boto3 invocation): <$AWS_PROFILE_CHOICE — omit line if default>
Target Bedrock model(s): <comma-joined $TARGET_MODELS, with any resolved overrides already applied>
Migration plan dir: <$MIGRATION_DIR>
Resolved target model id: <override for the primary chat model — omit if none>
Scripts directory (pinned uv toolchain): <$SCRIPTS>
Report date suffix: <saved suffix from run-context — C5/C6 dispatches only>
Source baseline available: <true|false>
Source provider env file: <path — omit if none>
User-supplied log files: <comma-joined — omit if none>
Golden dataset cap (max cases the ingestor may emit): 200
Phase results directory: <$PHASE_DIR>
Prior phase results (Read these files): <paths of already-validated phase JSONs>
Confirmed behavior-delta decisions file (Read it): <$PHASE_DIR/delta-decisions.json — C5 only>
<helper-reference lines — inject ONLY the ones this agent needs, per the table below>

Prior-phase results are passed as FILE PATHS — never inline their JSON into the prompt.

Helper references (the former helper skills, now under $HELPERS). Agents no longer load skills by name; instead the agent Reads a helper reference at an absolute path you inject. For each dispatch, add ONLY the helper lines that agent uses (per its # 4 section):

Expand $HELPERS to its absolute path (you have <SKILL_BASE>) so the subagent — where ${CLAUDE_PLUGIN_ROOT} is empty — receives a resolvable absolute path.

C0 — Run-context gate (resume safety)

The Eval phase makes one paid Bedrock call per golden case (and, with a source key, one paid source-provider call per case). Before any dispatch, tell the user evaluation will invoke Bedrock at their expense, capped at 200 cases.

1. mkdir -p $PHASE_DIR. Build $PHASE_DIR/current-context.json with exactly these fields (hashes via shasum -a 256; key hash is a fingerprint — never store the key value):

{
  "repo_root": "<cd $REPO && pwd -P>",
  "migration_dir": "<$MIGRATION_DIR>",
  "region": "<$REGION>",
  "aws_profile": "<$AWS_PROFILE_CHOICE or \"\">",
  "aws_account": "<Account from B2>",
  "repo_head_sha": "<git -C $REPO rev-parse HEAD>",
  "repo_branch": "<git -C $REPO rev-parse --abbrev-ref HEAD>",
  "repo_dirty_sha256": "<sha256 of: git status --porcelain + git diff + git diff --cached, EACH with pathspecs -- . ':(exclude).saws-migrate' ':(exclude).migration' ':(exclude)MIGRATION_REPORT_*.md'; \"\" when all three are empty>",
  "target_models": [{"source_model": "...", "aws_model_id": "...", "use_case": "..."}],
  "resolved_model_overrides": {},
  "source_provider": "<from B1>",
  "source_baseline_available": <true|false from B3>,
  "source_key_sha256": "<sha256 of .source-provider-env contents, \"\" when absent>",
  "log_files": [{"path": "...", "sha256": "..."}],
  "max_golden_cases": 200,
  "assess_design_sha256": "<sha256 of $MIGRATION_DIR/aws-design-ai.json>",
  "report_date_suffix": "<date +%Y-%m-%d>",
  "schema_version": 1,
  "plugin_version": "<version from <plugin>/.claude-plugin/plugin.json>"
}

1. Stage 0 (post-C5 normalization). If $PHASE_DIR/rewrite.json exists and validates as a payload (CONTROL=ok), do NOT use live repo_* values. Run three integrity checks: (1) rewrite.baseline_parent_sha equals the SAVED repo_head_sha; (2) git rev-parse <rewrite.branch_name> equals rewrite.branch_tip_sha; (3) git status --porcelain (with the artifact exclusions) is empty. All pass → copy the saved repo_* values into current-context verbatim, continue to step 3. Check 2 fails (tip moved) → STOP and AskUserQuestion: "Keep your commits (regenerate report only, with a mixed-authorship note)" / "Reset the branch to the rewriter's tip and regenerate from C6" / "Abort". Check 3 fails (dirty tree) → STOP and ask: commit/stash (then re-check) or discard the edits. Check 1 fails → treat as a full repo_* mismatch in step 3.

2. If $PHASE_DIR/run-context.json exists, compare:

uv run --project $SCRIPTS python $SCRIPTS/validate_result.py --check-run-context $PHASE_DIR/run-context.json --current $PHASE_DIR/current-context.json

• RUN_CONTEXT=match → resume: walk C1→C2→C3→(C4: delta-decisions.json)→C5→(C6: report file) in order; a phase counts completed iff its file validates with CONTROL=ok (C6: iff MIGRATION_REPORT_<saved suffix>.md exists while rewrite.json is payload-valid). STOP the walk at the first missing/invalid/control-state file — blocked/partial files route to their flows below, NEVER count as completed. Offer the user "skip completed phases X..Y, resume at Z". Files after an unexplained gap: archive them with the gap.
• RUN_CONTEXT=mismatch → scoped invalidation. Map each MISMATCH line through this table, archive the named units to $REPO/.saws-migrate/phase-results-archive/<saved suffix>-$(date +%H%M%S)/ (a SIBLING of phase-results/ — never nest it inside), then immediately overwrite run-context.json with current-context.json (carrying forward the saved report_date_suffix unless REPORT itself is being invalidated), then re-run the invalidated phases in order. Tell the user which fields differed and what re-runs.

Units: ANALYSIS = analysis.json · INGESTION = ingestion.json + .saws-migrate/golden-dataset/ · EVAL = eval.json + .saws-migrate/eval-results/ (minus cost_compare.py) · REWRITE = rewrite.json + delta-decisions.json · REPORT = MIGRATION_REPORT_<saved suffix>.md.

Post-C5 reruns of C1–C3 need the pre-migration tree. If rewrite.json was payload-valid and the table invalidates ANALYSIS/INGESTION/EVAL: confirm with the user that the old migration branch will be discarded (keep-or-reset flow first if the tip moved), then git checkout <saved repo_branch>, delete the old branch and the saws-migrate-baseline tag, and re-run from C1. If the user declines, stop — re-analyzing a tree that contains the rewrite produces garbage.

1. No saved run-context → fresh run: write current-context.json as run-context.json, dispatch C1.

C1 — Analyzer · C2 — Ingestor · C3 — Evaluator

For each phase in order, dispatch the agent with the context block (listing all prior-phase file paths), then validate its output file:

Blocked flow (CONTROL=blocked): resolve with the user per REASON —

• model_access → user enables the model in the Bedrock console (nothing fingerprinted changes; re-dispatch the blocked phase only)
• model_unresolvable → user picks/pastes an ID → record it in resolved_model_overrides, fold it into the Target line
• source_key_auth → user supplies a new key (re-run B3) or sets baseline unavailable
• authz → IAM denies inference. The detail names the action set to grant: bedrock:InvokeModel* for a Converse target, or the bedrock-mantle:* actions (CreateInference, CallWithBearerToken) for a mantle-only openai.gpt-5* target. User fixes IAM; nothing fingerprinted changes, so re-dispatch the blocked phase only. Do NOT route this to model_access — the console Model access page is the wrong fix for an IAM denial and vice versa.
• mantle_deps_missing → the pinned scripts environment lacks openai / aws-bedrock-token-generator, so a mantle target could not be probed at all. User re-syncs (uv sync --project $SCRIPTS); re-dispatch the blocked phase only. Access was never verified, so do not treat a previous pass as still valid.
• assess_output_missing → re-run Phase A, then restart Phase C at C0

After ANY resolution, re-run the C0 recipe (rebuild current-context, apply the invalidation table, overwrite run-context) and re-dispatch from the earliest invalidated phase — the table, not the block location, decides where execution resumes.

Partial flow (eval only, CONTROL=partial): AskUserQuestion —

• Continue remaining cases → re-dispatch the evaluator with the extra context line: Resume: raw_results.jsonl already contains completed cases — evaluate only prompts whose ids are not present in it, then re-score and overwrite eval.json
• Proceed with partial pass rate → re-dispatch the evaluator with: Finalize partial: do NOT call Bedrock again — score the cases already in raw_results.jsonl and emit the FULL eval payload over only those cases, with total_cases = the number scored and a notes prefix line 'partial_coverage: <completed>/<total> cases (throttled)'. Then C4 runs normally.
• Abort → stop; the files stay on disk for a later C0 resume.

C4 — Sidebar (two gates) + persist decisions

Gate (a) — Quality go/no-go. Read $PHASE_DIR/eval.json. The threshold is pass rate >= 0.9 AND source_baseline_quality != 'poor' (with no_golden_cases: true in the notes there is no quality signal — always ask). At or above → proceed silently. Below, AskUserQuestion:

• Proceed anyway → gate (b)
• Change target model → record in resolved_model_overrides, re-run C0 (the table invalidates ANALYSIS/EVAL and execution resumes at C1). Cap: 2 retries.
• Abort → stop, no code touched.

Gate (a.5) — Rewrite strategy (from migration plan). Read migration_path from $MIGRATION_DIR/aws-design-ai.json → ai_architecture.code_migration.migration_path. If the value starts with "mantle" ("mantle", "mantle_openai_responses"), set rewrite_strategy = "mantle". Otherwise (value is "converse", "gpt-oss", or the field is absent), set rewrite_strategy = "converse". No user question needed — the decision was already made during the Assess/Design phase.

Match on the prefix, not on equality: Design writes the more specific "mantle_openai_responses" for a same-model OpenAI migration, and an equality check against "mantle" would silently route those runs down the Converse path — rewriting working same-model code into a boto3 Converse client against a model that has no Converse surface.

Gate (b) — Behavior-delta resolution. For each analysis.behavior_deltas[] with user_visible == true, AskUserQuestion with the options from the behavior-delta-detection reference (Read $HELPERS/behavior-delta-detection/behavior-delta-detection.md, and the source_provider sub-reference under its references/ dir).

Persist: write the decisions array (entries {delta_type, location, resolution_chosen, source}; [] when there were no user-visible deltas) to $PHASE_DIR/delta-decisions.json and validate it (--schema delta-decisions). The file must exist before C5 — it is what makes a C5 retry or a post-crash resume self-sufficient.

C5 — Rewriter · C6 — Report

C5's context block includes the Confirmed behavior-delta decisions file line and the Report date suffix line (from run-context, NOT today's date on a resume). C6's context block lists all four phase-result file paths.

When rewrite_strategy == "mantle", C5's context block ALSO includes:

• Rewrite strategy: mantle (omit this line entirely for Converse — its absence is the signal for the default Converse path)
• Mantle model map: <source-model> -> <bedrock-model-id> — sourced from the plan's ai_architecture.bedrock_models[] entries (each source_model → aws_model_id pair).
• Mantle surface: responses and Mantle base path: /openai/v1 when any mapped aws_model_id is a proprietary GPT model (openai.gpt-5*). These are served only on the /openai/v1 path via the Responses API — distinct from the v1 path other mantle models use — so the rewriter must not emit a /v1 base URL or a Chat Completions call for them. See gcp-to-aws/references/shared/openai-on-bedrock.md.
• Same model: true when bedrock_models[].model_change is false. Signals the rewriter to keep model parameters untouched and limit changes to the endpoint, credential, model id, and (if the source used Chat Completions) the surface reshape.

C7 — Render summary

uv run --project $SCRIPTS python $SCRIPTS/render_report.py --phase-results $PHASE_DIR --repo $REPO --date-suffix <saved suffix>

Print the summary. Point the user at rewrite.branch_name (usually bedrock-migration, but a collision-suffixed variant like bedrock-migration-2 when they already had that branch) and the report file. Tell them how to undo — substitute the ACTUAL branch name from rewrite.branch_name, never a hardcoded one (on a collision run, bedrock-migration is the user's own pre-existing branch and deleting it would destroy their work):

To discard: git checkout <your original branch>, git branch -D <rewrite.branch_name>, git tag -d saws-migrate-baseline, and rm -rf .saws-migrate .migration removes all migration artifacts (including the API key file).

Inline mode (platforms without an Agent/subagent dispatch tool)

If this platform has no subagent dispatch tool, run phases inline ONE AT A TIME, with a mandatory stop between phases:

1. Read exactly ONE agent definition (<plugin>/agents/<name>.md) — never load more than one phase's definition into context at once.
2. Follow it start-to-finish; write and validate the same phase-result file.
3. STOP. Report the phase outcome (validator CONTROL line + one-line summary) and ask the user to confirm before loading the next phase's definition. This sidebar is mandatory: it is the context-pressure release valve, and the phase-result file means nothing is lost if the user continues in a fresh session instead.

Warn the user up front that inline mode is slower and context-heavier than subagent dispatch, and that the rewriter phase performs git operations (branch, commits, worktree) directly in this session.

Failure handling

• An agent dispatch dies (tool error, terminal failure) → the phase file is missing → validator exit 2 → the stateless fixer-retry path (which, finding no file to fix, re-runs the phase). Do not auto-retry more than the 2-retry cap.
• User aborts at any gate → confirm no SOURCE CODE was modified (C5 never started if aborted before then). Note that .migration/ and .saws-migrate/ artifacts do exist; show the undo commands from C7 if the user wants them gone.
• Assess skill fails → show the error and stop. User can re-run /aws-startup-advisor:llm-to-bedrock.