I'll start by reading the required files in order to understand the current state of the project.
Now let me check recent git history and read the current state of the key file I'll need to modify.
Good. I've read all the required files. Let me assess the current state:

**Completed tasks:**
- Task 1.3: `load_drug_indication_mapping()` and `get_search_terms_for_drug()` ÔÇö done in Iteration 1

**Remaining tasks (Phase 1):**
- Task 1.1: Update `get_patient_indication_groups()` to return ALL matches with code_frequency
- Task 1.2: Merge asthma Search_Terms in CLUSTER_MAPPING_SQL and `load_drug_indication_mapping()`

**Task selection reasoning:**
Progress.txt recommends either Task 1.2 (asthma merge ÔÇö self-contained, testable locally) or Task 1.1 (Snowflake query update). I'll choose **Task 1.2** because:
1. It's fully self-contained and testable without Snowflake connectivity
2. It's a prerequisite for getting clean data from both the Snowflake query AND the drug mapping
3. It's simpler and lower risk ÔÇö a good foundation before modifying the Snowflake query

Let me start by understanding what needs to change. I need to:
1. Update `CLUSTER_MAPPING_SQL` to merge 3 asthma Search_Terms into one `"asthma"` entry
2. Update `load_drug_indication_mapping()` to merge asthma variants when loading DimSearchTerm.csv
3. Verify the changes work correctly

First, let me check DimSearchTerm.csv to see the asthma-related rows.
Let me check the asthma-related entries in DimSearchTerm.csv.
Now let me check the current CLUSTER_MAPPING_SQL entries for asthma. I can see from the file I already read:
- `('allergic asthma', 'AST_COD')` ÔÇö line 1201
- `('asthma', 'eFI2_Asthma')` ÔÇö line 1210
- `('severe persistent allergic asthma', 'SEVAST_COD')` ÔÇö line 1316
- `('urticaria', 'XSAL_COD')` ÔÇö line 1337

The plan for CLUSTER_MAPPING_SQL is to map all 3 asthma Cluster_IDs to `Search_Term = 'asthma'`:
- `('asthma', 'AST_COD')` ÔÇö was allergic asthma
- `('asthma', 'eFI2_Asthma')` ÔÇö stays the same
- `('asthma', 'SEVAST_COD')` ÔÇö was severe persistent allergic asthma

`urticaria` stays as-is.
Now updating CLUSTER_MAPPING_SQL. I need to change `'allergic asthma'`  `'asthma'` and `'severe persistent allergic asthma'`  `'asthma'`. This means the CTE will have multiple rows mapping to `Search_Term = 'asthma'` with different Cluster_IDs (AST_COD, eFI2_Asthma, SEVAST_COD). That's fine  the UNION in AllIndicationCodes will just give us more SNOMED codes mapping to `'asthma'`, which is what we want.
Good. Now the CLUSTER_MAPPING_SQL has 3 rows for `'asthma'` with Cluster_IDs: AST_COD, eFI2_Asthma, SEVAST_COD. The GP lookup will return `Search_Term = 'asthma'` for any of these clusters. `urticaria` with `XSAL_COD` stays separate.

Now I need to update `load_drug_indication_mapping()` to merge the asthma variants. When loading DimSearchTerm.csv, rows with Search_Term = "allergic asthma" or "severe persistent allergic asthma" should have their drug fragments merged under a single "asthma" key.
I need to add a Search_Term normalization step in `load_drug_indication_mapping()`. The approach: define a mapping of asthma variant names  "asthma", and apply it when reading each row. This keeps the merge logic contained in one place.
Now I need to update the `__all__` exports to include the new constant, and update the log message to note the merge.

Let me also update the `__all__` list to include `SEARCH_TERM_MERGE_MAP` for potential use by other modules.
Now let me validate the changes.
Syntax check passed. Now let me test the import and verify the asthma merge works correctly.
All validations pass:

1. **Asthma merge works**: `asthma` now has the combined drug list: OMALIZUMAB, BENRALIZUMAB, DUPILUMAB, INHALED, MEPOLIZUMAB, RESLIZUMAB (from all 3 original rows)
2. **Variants removed**: `allergic asthma` and `severe persistent allergic asthma` no longer exist as separate entries
3. **Urticaria separate**: `urticaria`  `['OMALIZUMAB']`  correctly kept separate
4. **OMALIZUMAB maps correctly**: to both `asthma` and `urticaria` (not just one)
5. **Drug matching still works**: ADALIMUMAB maps to 7 indications as expected
6. **Count changes**: 162 Search_Terms (was 164 ÔÇö 2 fewer because 3 asthma entries merged into 1)
7. **Fragment count unchanged**: 346 (no fragments lost, just redistributed)

Now let me also verify the CLUSTER_MAPPING_SQL changes by checking the specific lines.
CLUSTER_MAPPING_SQL now has 3 entries for `'asthma'`:
- `('asthma', 'AST_COD')` ÔÇö was `allergic asthma`
- `('asthma', 'eFI2_Asthma')` ÔÇö unchanged
- `('asthma', 'SEVAST_COD')` ÔÇö was `severe persistent allergic asthma`

And `('urticaria', 'XSAL_COD')` is untouched. 

Now let me mark the task in the IMPLEMENTATION_PLAN.md.
Now let me commit the changes and update progress.txt.
I see many modified files from prior work. Let me check what my specific changes are in the files I modified.
The diff is clean and precise. Now let me update progress.txt and then commit both files together.
Now let me commit the changes.
Now let me update the commit hash in progress.txt.
**Iteration 2 complete.** Here's the summary:

**Task 1.2: Merge related asthma Search_Terms** ÔÇö DONE

Changes made:
1. **CLUSTER_MAPPING_SQL**: `'allergic asthma'`  `'asthma'` (AST_COD) and `'severe persistent allergic asthma'`  `'asthma'` (SEVAST_COD). Now 3 Cluster_IDs all map to `'asthma'`.
2. **SEARCH_TERM_MERGE_MAP**: New constant mapping asthma variants  canonical `"asthma"`. Reusable by other modules.
3. **load_drug_indication_mapping()**: Applies merge map at CSV load time. Combined asthma drug list: BENRALIZUMAB, DUPILUMAB, INHALED, MEPOLIZUMAB, OMALIZUMAB, RESLIZUMAB.
4. **urticaria** stays separate (XSAL_COD, OMALIZUMAB only).

All validation passed. Commits: `b0a8a9d`, `4fed0e5`.

**Next iteration**: Task 1.1 (update Snowflake query to return ALL matches with code_frequency) or Task 2.1 (assign_drug_indications function).
**Iteration 2 complete.** Here's the summary:

**Task 1.2: Merge related asthma Search_Terms** ÔÇö DONE

Changes made:
1. **CLUSTER_MAPPING_SQL**: `'allergic asthma'`  `'asthma'` (AST_COD) and `'severe persistent allergic asthma'`  `'asthma'` (SEVAST_COD). Now 3 Cluster_IDs all map to `'asthma'`.
2. **SEARCH_TERM_MERGE_MAP**: New constant mapping asthma variants  canonical `"asthma"`. Reusable by other modules.
3. **load_drug_indication_mapping()**: Applies merge map at CSV load time. Combined asthma drug list: BENRALIZUMAB, DUPILUMAB, INHALED, MEPOLIZUMAB, OMALIZUMAB, RESLIZUMAB.
4. **urticaria** stays separate (XSAL_COD, OMALIZUMAB only).

All validation passed. Commits: `b0a8a9d`, `4fed0e5`.

**Next iteration**: Task 1.1 (update Snowflake query to return ALL matches with code_frequency) or Task 2.1 (assign_drug_indications function).